JPWO2020122068A1 - Manufacturing method of fertilizer for natural water and fertilizer for natural water - Google Patents

Abstract

In the method for producing a fertilizer for natural water of the present invention, a first dissolution step of mixing sludge ash and an acidic liquid to dissolve heavy metals and phosphorus contained in the sludge ash, and the dissolution of the heavy metals and phosphorus. A first solid-liquid separation step of separating and removing the first liquid from the first solid, and a hydroxide and / or salt of an alkali metal and / or a Group 2 element with respect to the first solid. It is characterized by having a reactive ionic substance addition step of adding a reactive ionic substance and a firing step of subjecting the composition containing the first solid and the reactive ionic substance to a firing treatment. According to the present invention, it is possible to provide a fertilizer for natural water containing phosphorus, silicon and iron and having a sufficiently low content of heavy metals while effectively utilizing sludge ash, and to produce the fertilizer for natural water. A method can be provided. In particular, it is possible to provide a fertilizer for natural water in which the elution rate of a fertilizer component is suitably controlled, and to provide a method for producing the fertilizer for natural water.

Description

The present invention relates to a method for producing a fertilizer for natural water and a fertilizer for natural water.

Changes in seawater temperature due to global warming and the prohibition of dumping of organic waste substances such as sludge into the ocean promote oligotrophic conditions in the sea, especially phosphorus deficiency, which hinders the growth of seaweed. There is. Along with this, so-called desertification of the sea, which causes a decrease in the catch and a decrease in the collection of aquatic organisms such as abalone and sazae, which are also high-class foodstuffs, is progressing. Furthermore, it has a great impact on aquaculture.

As an attempt to provide nutrients to the sea, it has been reported that the growth of seaweed was improved by supplying iron by mixing steel slag and humus soil fermented with organic waste and burying it in the sea. (See, for example, Patent Document 1.). However, this was intended to be a source of iron, and could not alleviate or eliminate the problem caused by phosphorus deficiency.

Japanese Unexamined Patent Publication No. 2014-066594

An object of the present invention is to provide a fertilizer for natural water containing phosphorus, silicon and iron and having a sufficiently low content of heavy metals while effectively utilizing sludge ash, and to produce the fertilizer for natural water. To provide a method. In particular, it is an object of the present invention to provide a fertilizer for natural water in which the elution rate of a fertilizer component is suitably controlled, and to provide a method for producing the fertilizer for natural water.

Such an object is achieved by the following invention.
The method for producing a fertilizer for natural water of the present invention comprises a first dissolution step of mixing sludge ash and an acidic liquid to dissolve heavy metals and phosphorus contained in the sludge ash.
A first solid-liquid separation step of separating and removing the first liquid in which heavy metals and phosphorus are dissolved from the first solid,
A step of adding a reactive ionic substance, which is a hydroxide and / or a salt of an alkali metal and / or a Group 2 element, to the first solid.
It is characterized by having a firing step of subjecting the composition containing the first solid and the reactive ionic substance to a firing treatment.

In the method for producing a fertilizer for natural water of the present invention, the reactive ionic substance is preferably a hydroxide and / or a salt containing Na and / or Ca.

In the method for producing a fertilizer for natural water of the present invention, the reactive ionic substance is one selected from the group consisting of _{Na 2} CO ₃ , NaOH, CaCO ₃ , Ca (OH) ₂ , CaCl _{2 and NaCl.} It is preferable that there are two or more types.

In the method for producing a fertilizer for natural water of the present invention, the firing temperature in the firing process is preferably 150 ° C. or higher and 1100 ° C. or lower.

In the method for producing a fertilizer for natural water of the present invention, the treatment time of the firing treatment is preferably 0.5 hours or more and 100 hours or less.

In the method for producing a fertilizer for natural water of the present invention, it is preferable to have a reduction step of adding a reducing agent to the first solid to perform a reduction treatment.

In the method for producing a fertilizer for natural water of the present invention, it is preferable to further include an N component addition step of adding a nitrogen-based fertilizer component into the system after the first solid-liquid separation step.

In the method for producing a fertilizer for natural water of the present invention, it is preferable to further include a P component addition step of adding a phosphorus-based fertilizer component into the system after the first solid-liquid separation step.

In the method for producing a fertilizer for natural water of the present invention, the phosphorus-based fertilizer component is used.
The first precipitation step of mixing the first liquid separated in the first solid-liquid separation step with a precipitate and raising the pH to precipitate a second solid containing the heavy metal and phosphorus.
The second solid-liquid separation step of separating the second solid from the liquid component,
The second dissolution step of dissolving phosphorus contained in the second solid with an alkaline liquid, and
It is preferable that the second liquid in which phosphorus is dissolved is separated by a method having a third solid-liquid separation step of separating the solid component containing a heavy metal from the solid component.

In the method for producing a fertilizer for natural water of the present invention, the phosphorus-based fertilizer component is prepared by mixing the second liquid with a precipitate and lowering the pH after the third solid-liquid separation step to obtain phosphorus. It is preferably obtained by using a method further comprising a second precipitation step of precipitating the containing third solid.

In the method for producing a fertilizer for natural water of the present invention, it is preferable that the pH of the liquid phase at the end of the second precipitation step is 2.0 or more and 12.0 or less.

In the method for producing a fertilizer for natural water of the present invention, it is preferable to use an acidic liquid having a pH of −1.0 or more and 2.0 or less in the second precipitation step.

In the method for producing a fertilizer for natural water of the present invention, it is preferable to use the reactive ionic substance in the second precipitation step.

The fertilizer for natural water of the present invention uses sludge ash as a raw material.
Contains phosphorus, silicon and iron,
It is characterized in that the content of heavy metals is 1000 ppm or less.

In the fertilizer for natural water of the present invention, the phosphorus content is 1.0% by mass or more and 10% by mass or less.
The silicon content is 10% by mass or more and 50% by mass or less.
The iron content is preferably 1.0% by mass or more and 50% by mass or less.

In the natural water fertilizer of the present invention, when the phosphorus content is _XP [mass%], the silicon content is X _Si [mass%], and the iron content is X _Fe [mass%], 1. _{0 ≦ X Si / X P ≦} 50.0, and preferably satisfy the relationship of _{0.9 ≦ X Fe / X P ≦} 50.0.

According to the present invention, it is possible to provide a fertilizer for natural water containing phosphorus, silicon and iron and having a sufficiently low content of heavy metals while effectively utilizing sludge ash, and to manufacture the fertilizer for natural water. A method can be provided. In particular, it is possible to provide a fertilizer for natural water in which the elution rate of a fertilizer component is suitably controlled, and to provide a method for producing the fertilizer for natural water.

FIG. 1 is a process diagram showing a preferred embodiment of the method for producing a fertilizer for natural water of the present invention. FIG. 2 is a diagram schematically showing the relationship between the pH of the liquid phase at the end of the first precipitation step and the final recovery rate of phosphorus. FIG. 3 is a diagram showing changes over time in the elution rate of iron and the like when sludge ash (Comparative Example 1) is treated with hydrochloric acid. FIG. 4 shows the relationship between the number of days elapsed from the addition to the sodium chloride aqueous solution and the elution rate of the phosphorus component with respect to the change in the amount of sodium carbonate added to the fertilizers for natural water according to Examples 1 to 5 and Comparative Example 1. It is a figure. FIG. 5 is a diagram showing the correspondence between the pH of the liquid phase at the end of the first precipitation step and the X-ray diffraction (XRD) pattern of the precipitate for Examples 6, 7 and 8. FIG. 6 shows the recovery rate of phosphorus and major metal elements (that is, the amount contained in sludge ash as a raw material) for the third solid obtained in the process of producing the fertilizer for natural water of Example 6. It is a graph which shows the ratio of the amount contained in 3 solids. FIG. 7 is a graph showing the results of a water solubility test and a solubility test on a third solid obtained in the process of producing the fertilizer for natural water of Example 6. FIG. 8 is a flowchart showing a specific example of the method for producing a fertilizer for natural water of the present invention. FIG. 9 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 11 to 16 to the sodium chloride aqueous solution and the elution rate of the phosphorus component with respect to the change in firing temperature. FIG. 10 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 17 and 18 to the aqueous solution of sodium chloride and the elution rate of the phosphorus component with respect to the change in the amount of calcium carbonate added. FIG. 11 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 19 and 20 to the sodium chloride aqueous solution and the elution rate of the phosphorus component with respect to the change in the firing time. FIG. 12 is a diagram showing the relationship between the number of days elapsed from the addition of sodium hydroxide to the aqueous solution of sodium chloride and the elution rate of the iron component in the fertilizers for natural water according to Example 21 and Comparative Example 2. be. FIG. 13 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 22 and 23 to the aqueous solution of sodium chloride and the elution rate of the iron component with respect to the change in the amount of sodium hydroxide added. .. FIG. 14 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 24 and 25 to the sodium chloride aqueous solution and the elution rate of the iron component with respect to the change in firing temperature. FIG. 15 shows the relationship between the number of days elapsed from the addition of the reactive ionic substance to the aqueous sodium chloride solution and the elution rate of the silicon component for the natural water fertilizers according to Examples 26 to 28 and Comparative Example 3. It is a figure. FIG. 16 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 29 to 31 to the sodium chloride aqueous solution and the elution rate of the silicon component with respect to the change in firing temperature. FIG. 17 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 32 and 33 to the sodium chloride aqueous solution and the elution rate of the silicon component with respect to the change in the amount of sodium ion added. FIG. 18 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 34 and 35 to the sodium chloride aqueous solution and the elution rate of the silicon component with respect to the change in the amount of calcium ions added.

Hereinafter, preferred embodiments of the present invention will be described in detail.
[Manufacturing method of fertilizer for natural water]
First, a method for producing a fertilizer for natural water of the present invention will be described.

FIG. 1 is a process diagram showing a preferred embodiment of the method for producing a fertilizer for natural water of the present invention. FIG. 2 is a diagram schematically showing the relationship between the pH of the liquid phase at the end of the first precipitation step and the final recovery rate of phosphorus.

The method for producing a fertilizer for natural water of the present invention comprises a first dissolution step of mixing sludge ash and an acidic liquid to dissolve heavy metals and phosphorus contained in the sludge ash, and a first dissolution step in which heavy metals and phosphorus are dissolved. A first solid-liquid separation step of separating and removing one liquid from a first solid, and a reaction of the first solid with an alkali metal and / or a hydroxide and / or salt of a Group 2 element. It is characterized by having a reactive ionic substance addition step of adding a reactive ionic substance and a firing step of subjecting the composition containing the first solid and the reactive ionic substance to a firing treatment.

By using sludge ash as a raw material in this way, sludge ash that was conventionally treated as industrial waste can be effectively used for unprecedented purposes, from the viewpoint of resource saving and landfill of industrial waste. It is preferable from the viewpoint of securing land and reducing sludge ash treatment costs as a whole. In particular, since most of the sludge ash (for example, the portion occupying about 90% by volume) can be effectively used as fertilizer for natural water, the effect from the above viewpoint is very large. Further, the sludge ash contains iron and silicon in a high content in addition to phosphorus, and a fertilizer for natural water containing these components in a well-balanced manner can be preferably obtained. Further, by having the reactive ionic substance addition step and the firing step, it is possible to suitably enhance the solubility of fertilizer components such as silicon component and iron component in addition to the phosphorus component contained in the fertilizer for natural water. In particular, by adjusting the type and amount of the reactive ionic substance used in the reactive ionic substance addition process and the calcination treatment conditions in the calcination process, the elution rate of fertilizer components from the fertilizer for natural water produced can be adjusted. It can be suitably controlled. For example, the fertilizer application effect of a fertilizer component can be controlled in a wide range of several days to several years. More specifically, for example, in a natural water fertilizer in which the amount of sodium carbonate added is changed from 15% by mass to 35% by mass and sintered at 900 ° C. with respect to the first solid, the content of phosphorus is 50%. The time required for elution is 3% by weight for 2 days, whereas 15% requires 350 days. Under the same conditions (sintering temperature 900 ° C., phosphorus elution rate 50%), when comparing the case where the amount of calcium carbonate added is 20% by weight and 10% by weight with respect to the first solid, 20% by weight is used. It's 300 days. At 10%, 1500 days are required. That is, for example, by changing the production conditions within the above range, the fertilizer application effect of the fertilizer component can be suitably controlled in a wide range of about 2 days to 1500 days. In addition, by lengthening the sintering time and reducing the amount of ionic substances added, the elution rate of fertilizer components from the fertilizer for natural water can be made relatively low, and the sustainability of the fertilizer for natural water can be improved. .. By shortening the sintering time and increasing the amount of the ionic substance added, the elution rate of the fertilizer component from the fertilizer for natural water can be relatively increased, and the immediate effect of the fertilizer for natural water can be enhanced. For example, when the sintering temperature is from 600 ° C. to 900 ° C., the phosphorus elution rate increases as the temperature increases, but when the sintering temperature exceeds 900 ° C., the elution rate decreases. Further, in the first melting step, heavy metals can be efficiently removed from sludge ash, so that a highly safe fertilizer for natural water can be obtained. Further, since the first liquid separated in the first solid-liquid separation step contains phosphorus in a high content, it is possible to preferably obtain a high-purity phosphorus compound by purifying the first liquid. Can be done. Therefore, phosphorus contained in sludge ash can be used with particularly high efficiency as a whole. Further, since the heavy metal is selectively contained in the first liquid separated in the first solid-liquid separation step in a relatively high content, the composition containing the heavy metal in a relatively high concentration. The volume of the waste can be significantly reduced, which is preferable from the viewpoint of securing a land for treating industrial waste and managing harmful substances.

In the present invention, the heavy metal refers to a metal having a specific gravity of 4 or more and excluding iron. Further, in the present specification, natural water includes water that exists collectively in the natural world such as the sea, rivers, lakes, ponds, and swamps, and in addition, artificially created artificial ponds and reservoirs. The concept includes water that exists in a closed space that is not directly connected to the sea, rivers, lakes, ponds, swamps, etc., such as fishing ponds, water tanks, and farms. Further, in the present invention, the natural water also includes irrigation canal water. Further, the natural water may be fresh water, salt water or brackish water.

Above all, the natural water to which the fertilizer for natural water according to the present invention is applied is preferably seawater.
The sea is prone to oligotrophic problems, and so-called desertification of the sea is progressing. Therefore, when the natural water is seawater, the effect of the present invention is more remarkably exhibited.

Ecosystems can be restored by stopping the desertification of the sea. For example, by using the fertilizer for natural water according to the present invention, nutrients can be supplied to the sea, the growth of seaweeds such as kelp and wakame seaweed is improved, and it becomes a place for fish to grow. Furthermore, since seaweed can also be used as food for abalone and turban shells, the production of abalone and turban shells, which are also high-class foodstuffs, will increase. That is, it can contribute to the economic revitalization of fishing villages.

In particular, the present embodiment further includes an N component addition step of adding a nitrogen-based fertilizer component into the system after the first solid-liquid separation step.

This makes it possible to suitably prepare a fertilizer for natural water containing a nitrogen-based fertilizer component, which tends to be insufficient with a fertilizer derived from sludge ash, in a suitable ratio.

Further, in the present embodiment, after the first solid-liquid separation step, there is a P component addition step of adding a phosphorus-based fertilizer component into the system.

Thereby, for example, the content of the phosphorus-based fertilizer component in the fertilizer for natural water can be adjusted to a suitable value. In addition, a fertilizer for natural water containing a plurality of types of phosphorus-based fertilizer components having different solubility in water (particularly, a fertilizer for natural water containing these components in a suitable ratio) can be suitably prepared.

The composition containing the phosphorus-based fertilizer component added to the first solid in the P component addition step will be described in detail later.
Further, in the present embodiment, in the P component addition step, a composition containing a reactive ionic substance is added together with the phosphorus-based fertilizer component. In other words, the step of adding the P component also serves as the step of adding the reactive ionic substance.

As a result, the phosphorus-based fertilizer component can be supplied to the first solid while supplying the reactive ionic substance, and the phosphorus-based fertilizer component can be made excellent in the productivity of the fertilizer for natural water. It is possible to obtain a fertilizer for natural water in which the content of fertilizer and the elution rate of fertilizer components are more preferably controlled.

The step of adding the reactive ionic substance may be performed directly on the first solid obtained in the first solid-liquid separation step, or the first solid-liquid separation step obtained in the first solid-liquid separation step. It may be performed after the solid has been subjected to a predetermined treatment.

In particular, the step of adding the reactive ionic substance is performed before the firing step described in detail later. In other words, the firing step is performed after the step of adding the reactive ionic substance.

As a result, the sparingly soluble component (for example, phosphorus component, silicon component, iron component, etc.) contained in the treated sludge ash is suitably reacted with the reactive ionic substance, and the final obtained natural water is obtained. The solubility of the phosphorus component, the silicon component, the iron component and the like contained in the fertilizer can be more preferably adjusted.

The following is an example of a chemical reaction that proceeds when a reactive ionic substance is used. In the equation, x, y, z, l, m, and n are integers of 1 or more, respectively.

(1) When the sparingly soluble phosphorus component contained in the treated sludge ash to be treated is iron phosphate (FePO ₄ ) (1-1) Reaction with _{Na 2} CO _3:
FePO ₄ + 3/2Na ₂ CO ₃ → Na ₃ PO ₄ + 3/2CO ₂ + 1 / 2Fe ₂ O ₃
2FePO ₄ + 2Na ₂ CO ₃ → Na ₄ P ₂ O ₆ + 2CO ₂ + Fe ₂ O ₃ + 1 / 2O ₂
Fe _x P _y O _z + Na ₂ CO ₃ → Na _x P _y O _z + mCO ₂ + lFe ₂ O ₃

(1-2) Reaction with _{CaCO 3:}
2FePO ₄ + 3CaCO ₃ → Ca ₃ (PO ₄ ) ₂ + 3CO ₂ + FeCO ₃
Fe _x P _y O _z + 3CaCO ₃ → Ca _x P _y O _z + mCO ₂ + nFe ₂ O ₃

(2) When the sparingly soluble phosphorus component contained in the treated sludge ash to be treated is aluminum phosphate (AlPO ₄ ) (2-1) Reaction with _{Na 2} CO _3:
AlPO ₄ + 3/2Na ₂ CO ₃ → Na ₃ PO ₄ + 3/2CO ₂ + 1 / 2Al ₂ O ₃
2AlPO ₄ + 2Na ₂ CO ₃ → Na ₄ P ₂ O ₆ + 2CO ₂ + Al ₂ O ₃ + 1 / 2O ₂
Al _x P _y O _z + Na ₂ CO ₃ → Na _x P _y O _z + mCO ₂ + lAl ₂ O ₃

(2-2) Reaction with _{CaCO 3:}
2AlPO ₄ + 3CaCO ₃ → Ca ₃ (PO ₄ ) ₂ + 3CO ₂ + Al ₂ O ₃
Al _x P _y O _z + 3CaCO ₃ → Ca _x P _y O _z + mCO ₂ + nAl ₂ O ₃

Further, for example, such as by adjusting the contributing proportion of each component in the reaction, soluble salts, calcium-deficient _{hydroxyapatite, CaHPO 4, Ca (H 2} PO 4) 2, Ca 8 (HPO 4) 2, Na _It can also be obtained as a hydrogen phosphate salt such as 2 HPO ₄ and NaH ₂ PO _4.

An example of a chemical reaction for obtaining such a hydrogen phosphate salt is shown below. In the equation, x, y, a, b, c, d, and e are integers of 1 or more, and M is a metal element.

Ca _x PyO _z + M (OH) _a → Ca _b H _c P _d O _e
Na _x PyO _z + M (OH) _a → Na _b H _c P _d O _e

In particular, in the present embodiment, the reactive ionic substance added in the reactive ionic substance addition step is the one used in the second precipitation step described in detail later.

This prevents inconveniences such as unintentional dissolution of phosphorus components in the manufacturing process of fertilizer for natural water, and makes the productivity of fertilizer for natural water and the composition of fertilizer for natural water more reliable and suitable for nature. The solubility of phosphorus components and the like contained in water fertilizer can be more preferably increased.

Further, the method for producing a fertilizer for natural water of the present invention may have a reduction step of adding a reducing agent to a first solid which is a treated product of sludge ash to perform a reducing treatment.

Thereby, the solubility of the phosphorus component and the like contained in the fertilizer for natural water can be more preferably increased. Further, when the first solid contains iron, silicon and the like, the elution rate of these can be suitably controlled in the finally obtained fertilizer for natural water.

The reduction step may be performed directly on the first solid obtained in the first solid-liquid separation step, or a predetermined treatment may be performed on the first solid obtained in the first solid-liquid separation step. It may be performed after applying.

The reduction step can be performed using, for example, a reducing agent containing carbon, hydrogen, or the like. It is also possible to adopt a method of mixing and reducing agricultural and forestry waste such as rice husks such as rice. Examples of the reducing agent containing carbon include graphite, carbon black and the like.

The reduction step may be performed at any timing, but for example, it is preferably performed at a timing after elution and removal of heavy metals and phosphorus from sludge ash and then after the process of adding the reducing agent. Further, by performing the firing step without oxygen, the reduction step and the firing step may be performed at the same time.

Further, in the present embodiment, a firing step of performing a firing treatment on the composition containing the first solid and the reactive ionic substance is performed after the first solid-liquid separation step and the reactive ionic substance addition step. Have more.

Thereby, for example, the amount of water contained in the fertilizer for natural water can be suitably reduced. Further, for example, the solubility of the fertilizer for natural water in water can be suitably adjusted.

In the configuration shown in FIG. 1, the P component addition step, the firing step, and the N component addition step are performed in this order after the first solid-liquid separation step, but the order of these steps may be changed. Further, a plurality of steps may be performed simultaneously.

<First dissolution step>
In the first dissolution step, sludge ash and an acidic liquid are mixed.
This dissolves heavy metals and phosphorus contained in sludge ash.

Note that in the sludge ash in, phosphorus, typically oxides (P ₂ O _5, etc.) and phosphoric acid, is contained in a form such as phosphoric acid salt. In the following description, a compound containing phosphorus as an atom (including an ionic substance) including these forms and a phosphorus atom contained in the compound may be simply referred to as phosphorus.

Further, in sludge ash, heavy metals are contained in the form of metal oxides (including compound oxides), elemental metals, alloys, metal salts and the like. In the following description, a compound containing a heavy metal as an atom (including an ionic substance) including these forms and a heavy metal atom contained in the compound may be simply referred to as a heavy metal.

The sludge ash used in this step (that is, sludge ash as a raw material for fertilizer for natural water) generally contains iron and silicon in addition to heavy metals and phosphorus. In this step, heavy metals can be efficiently dissolved, but in addition to iron and silicon, a part of phosphorus in sludge ash remains in the solid content without being dissolved.

As a result, heavy metals can be prevented from remaining in the finally obtained fertilizer for natural water, and phosphorus, iron and silicon can be suitably contained.

Further, the sludge ash used in this step (that is, sludge ash as a raw material for fertilizer for natural water) generally contains Al, Mg and the like in addition to the above components.

As a result, in this step, metals other than heavy metals can be dissolved together with heavy metals and phosphorus contained in sludge ash. For example, a part of iron contained in sludge ash dissolves. These components function as impurities in the first precipitation step described in detail later, and are the crystals of phosphate (particularly, for example, calcium hydrogen phosphate dihydrate, calcium salt of phosphoric acid such as calcium phosphate). It is possible to prevent coarsening more effectively. As a result, the phosphate crystals formed are relatively unstable and tend to dissolve in alkaline liquids. As a result, the phosphate can be dissolved with higher selectivity in the second dissolution step described in detail later.

The acidic liquid used in this step is not particularly limited, but is preferably a strong acid having a pH (hydrogen ion index) of −1.0 or more and 2.0 or less.

As a result, the amount of acidic liquid used can be suppressed while ensuring safety, and this step can be efficiently performed. In addition, it is possible to effectively prevent the volume of the composition after the treatment in this step (that is, a mixture of sludge ash and an acidic liquid) from becoming too large. It is also preferable from the viewpoint of ease of subsequent processes and reduction of the amount of waste liquid to be treated.

The pH of the acidic liquid used in this step is preferably -1.0 or more and 1.5 or less, more preferably -0.5 or more and 1.3 or less, and 0 or more and 1.0 or more. The following is more preferable.
As a result, the above-mentioned effect is more prominently exhibited.

As the acidic liquid, for example, sulfuric acid, nitric acid, acetic acid, hydrochloric acid, a liquid containing two or more of these, and the like can be used.

The pH of the liquid phase (that is, the first liquid in which heavy metals and phosphorus are dissolved) at the end of this step is preferably 0.5 or more and 6.8 or less, but in particular, 1.0 or more and 6.5. It is more preferably 1.5 or more and 6.0 or less.

As a result, the heavy metal can be eluted more efficiently, and the residual amount of the heavy metal in the solid phase at the end of this step can be more reliably reduced. In addition, phosphorus can be eluted at an appropriate ratio, and it becomes easy to adjust the phosphorus content in the finally obtained fertilizer for natural water to a suitable range. In addition, it is possible to more reliably prevent heavy metals and excess phosphorus from being unintentionally deposited before the first precipitation step.

The dissolution rate of phosphorus in the liquid phase at the end of this step is not particularly limited, but is preferably 10% or more and 99% or less, more preferably 15% or more and 90% or less, and more preferably 20% or more. It is more preferably 70% or less.
As a result, phosphorus, which is a useful substance, can be recovered more efficiently.

Further, this step is preferably performed while stirring a mixture of sludge ash and an acidic liquid.
As a result, the sludge ash and the acidic liquid can be brought into contact with each other more efficiently, and heavy metals and the like can be dissolved more efficiently.

Various stirring devices and various mixing devices can be used for stirring the mixture of sludge ash and the acidic liquid.
Further, this step may be performed by a batch method or a continuous method.

<First solid-liquid separation step>
In the first solid-liquid separation step, the first liquid in which heavy metals and phosphorus are dissolved is separated and removed from the first solid which is a solid component.

As a result, a solid (that is, a first solid) containing substantially no heavy metal and having an adjusted phosphorus content can be obtained. Further, such a first solid contains silicon and iron derived from sludge ash in addition to phosphorus. Therefore, the first solid can be suitably used as a fertilizer for natural water or a raw material thereof.

The method of solid-liquid separation is not particularly limited, and examples thereof include decantation, filtration, centrifugation, and the like, and a plurality of methods may be combined.

Further, in this step, if necessary, the once separated solid phase (that is, the first solid) may be washed with water or the like.

Thereby, for example, the ion concentration of the acid component and the content of heavy metals can be further lowered.

The liquid used for washing the solid phase may be used in the first precipitation step described in detail later in combination with the liquid phase obtained by the previous solid-liquid separation after recovery.

The content of phosphorus in the solid-liquid separated solid phase is not particularly limited, but is preferably 1.0% by mass or more and 40% by mass or less, and preferably 2.0% by mass or more and 20% by mass or less. It is more preferably 3.0% by mass or more and 10.0% by mass or less.

The content of heavy metals in the solid-liquid separated solid phase (when a plurality of heavy metal elements are contained, the total amount thereof; the same applies hereinafter) is not particularly limited, but is preferably 1% by mass or less. , 0.01% by mass or less, more preferably 0.0001% by mass or less.

<P component addition process>
In the present embodiment, a phosphorus-based fertilizer component is added to the solid phase (that is, the first solid) separated in the first solid-liquid separation step in the P component addition step. In particular, in the present embodiment, in the P component addition step, a composition containing a reactive ionic substance is added to the first solid together with a phosphorus-based fertilizer component.

Examples of the phosphorus-based fertilizer component include phosphoric acid-based compounds recovered from sludge ash, commercially available phosphoric acid-based fertilizer, steelmaking slag, biomass burning ash, steel slag, and the like, and one or two selected from these. Seeds and above can be used in combination.

The phosphorus-based fertilizer component may be added in a solid state, or may be added in a solution state or a paste state.
The preparation of the composition to be added to the first solid in the P component addition step, that is, the composition containing the reactive ionic substance together with the phosphorus-based fertilizer component will be described in detail later. The timing of the P component addition step is not particularly limited, and for example, the P component addition step may be performed at a timing after the firing step.

<Baking process>
In the firing step, the composition containing the first solid and the reactive ionic substance is fired.

In particular, in the present embodiment, the firing step is performed after the P component addition step.

The firing temperature in the firing treatment is not particularly limited, but is preferably 150 ° C. or higher and 1100 ° C. or lower, more preferably 200 ° C. or higher and 1000 ° C. or lower, and further preferably 250 ° C. or higher and 950 ° C. or lower.

Thereby, the solubility of each component from the fertilizer for natural water can be more preferably adjusted.

The treatment time of the firing treatment is not particularly limited, but is preferably 0.5 hours or more and 100 hours or less, more preferably 1.5 hours or more and 90 hours or less, and 2 hours or more and 80 hours or less. Is even more preferable.

Thereby, the solubility of each component from the fertilizer for natural water can be more preferably adjusted.

<N component addition process>
In the N component addition step, a nitrogen-based fertilizer component is added.

Examples of the nitrogen-based fertilizer component include urea, lime nitrogen, sodium nitrate, ammonium nitrate, ammonium sulfate and the like, and one or a combination of two or more selected from these can be used.

The amount of the nitrogen-based fertilizer component added is not particularly limited, but the nitrogen content with respect to 100 parts by mass of the phosphorus atom in the finally obtained natural water fertilizer is such that the following conditions are satisfied. Is preferable. That is, the content of nitrogen with respect to 100 parts by mass of phosphorus atoms in the finally obtained natural water fertilizer is not particularly limited, but is preferably 1.0 part by mass or more and 30.0 parts by mass or less. It is more preferably 0 parts by mass or more and 20.0 parts by mass or less, and further preferably 3.0 parts by mass or more and 10.0 parts by mass or less.

Thereby, the balance between the phosphorus atom and the nitrogen atom contained in the fertilizer for natural water can be made more suitable.

The nitrogen-based fertilizer component may be added in a solid state, or may be added in a solution state or a paste state.

<Regarding the composition added to the first solid in the P component addition step>
Hereinafter, the composition added to the first solid in the P component addition step, that is, the composition containing the phosphorus-based fertilizer component and the reactive ionic substance will be described in detail.

The phosphorus-based fertilizer component contained in the composition added in the P component addition step is not particularly limited, and for example, a commercially available fertilizer may be used, but it is obtained through a method having each of the following steps. Is preferable.

That is, the composition added to the first solid in the P component addition step mixes the first liquid separated in the first solid-liquid separation step with the precipitate and raises the pH, and contains heavy metals and phosphorus. The first precipitation step of precipitating the second solid, the second solid-liquid separation step of separating the second solid from the liquid component, and the second solid-liquid separation step of dissolving the phosphorus contained in the second solid with an alkaline liquid. It is preferably separated by a method having a dissolution step of 2 and a third solid-liquid separation step of separating the second liquid in which phosphorus is dissolved from the solid component containing heavy metal.

As a result, the phosphorus-based fertilizer component contained in the composition added in the P component addition step can also be derived from sludge ash, and the utilization efficiency of sludge ash can be further improved. Further, such a phosphorus-based fertilizer component (a phosphorus-based fertilizer component contained in the composition added in the P component addition step) is more soluble in water than the phosphorus component contained in the first solid described above. Since it has high properties, the solubility of phosphorus-based fertilizer components as a whole of fertilizer for natural water can be suitably adjusted, and immediate effect and sustainability can be achieved at a higher level.

In particular, for the phosphorus-based fertilizer component, after the third solid-liquid separation step, the second liquid is mixed with the precipitate and the pH is lowered to precipitate the third solid containing phosphorus. It is preferable that it is obtained by using a method further comprising.

As a result, a highly pure phosphoric acid containing substantially no heavy metal can be obtained, and the phosphate can be suitably used as a phosphorus-based fertilizer component in the P component addition step. Further, since the phosphate has a high purity, it is suitable for applications other than the phosphorus-based fertilizer component used in the P component addition step. Further, phosphorus can be treated as a phosphate which is a solid substance (for example, calcium hydrogen phosphate dihydrate, calcium phosphate, etc.), and can be more preferably stored and transported.

<First precipitation step>
In the first precipitation step, the first liquid separated from the first solid in the first solid-liquid separation step is mixed with a precipitate and the pH is raised to obtain a second solid containing heavy metals and phosphorus. Precipitate. In particular, phosphorus is precipitated as a phosphate (eg, calcium hydrogen phosphate dihydrate, calcium phosphate, etc.).

This facilitates the handling of substances containing substances other than heavy metals and phosphorus in a later step. In addition, the content of components other than heavy metals and phosphorus in substances containing heavy metals and substances other than phosphorus can be reduced, and the amount of impurities mixed in the phosphorus recovery step can be reduced.

Further, by precipitating the phosphate under such conditions, the nucleation and growth of the phosphate can be suitably controlled, and the phosphate can be precipitated as microcrystals. As a result, in the subsequent second dissolution step, the phosphate can be easily dissolved, and phosphorus (dissolved state) can be suitably separated from the heavy metal (solid state).

In addition, the first liquid usually contains Al, Mg, etc. together with heavy metal and phosphorus, which further coarsens the crystals of phosphate (particularly, the calcium salt of phosphoric acid) in this step. It can be effectively prevented. As a result, the phosphate crystals formed are relatively unstable and tend to dissolve in alkaline liquids. Therefore, the phosphate can be dissolved with higher selectivity in a later step.

In this step, any substance or composition may be used as long as it can be mixed with the precipitate and the pH can be raised, but it is preferable to use an alkaline liquid having a pH of 10 or more.

Thereby, the pH of the mixture can be raised more preferably, and the second solid containing heavy metals and phosphorus can be deposited more efficiently. In addition, it is possible to more reliably prevent phosphorus and heavy metals from being unintentionally redissolved before the completion of the second solid-liquid separation step. In addition, it is possible to more effectively prevent the crystals of the phosphate contained in the precipitate deposited in this step from becoming coarse.

The precipitant may have a function of promoting the precipitation of phosphates and the like, and for example, CaCl ₂ , Ca (OH) ₂ , CaCO _{3 and the} like, Al-based substances such as Al salt, Fe. Fe-based substances such as salts and Mg-based substances such as Mg salts can be used, but Ca-based substances are preferably used. Thereby, in this step, phosphorus can be precipitated as a calcium salt of phosphoric acid (for example, calcium hydrogen phosphate dihydrate, calcium phosphate, etc.), and the subsequent step can be more preferably performed.

In this step, it is preferable to use an alkaline liquid having a pH of 10 or more, but the pH of the alkaline liquid is not particularly limited, but is more preferably 11 or more, and further preferably 12 or more and 14 or less.

As a result, the above-mentioned effects are more prominently exhibited, and the alkaline liquid can be easily and stably obtained or prepared.

Further, in this step, it is preferable to use an alkaline calcium compound (ionic substance), _{which is selected from the group consisting of CaCl 2} , Ca (OH) ₂ , CaCO ₃ and chloride having Al, Mg and Fe components. It is more preferable to use one or more kinds, and it is more preferable to use one or more kinds selected from the group consisting of _{CaCl 2} , Ca (OH) ₂ and CaCO ₃ , and it is more preferable to use _{CaCl 2.} Most preferable.

These calcium compounds more favorably function as precipitates. Therefore, the pH of the mixture can be suitably adjusted while efficiently supplying the calcium component that is a part of the calcium salt of phosphoric acid into the system. As a result, in this step, the amount of the substance mixed with the first liquid can be suppressed, and this step can be efficiently advanced. In addition, the balance between the calcium content and pH in the mixture in this step can be suitably adjusted, and while improving the precipitation efficiency of heavy metals and phosphorus, the content of impurities in the first liquid can be further increased. Can be lowered. In addition, it is possible to more reliably prevent phosphorus and heavy metals from being unintentionally redissolved before the completion of the second solid-liquid separation step.

The pH of the liquid phase at the end of this step is not particularly limited, but is preferably 1.0 or more and 12 or less, more preferably 1.5 or more and 9.0 or less, and 2.0 or more and 8. It is more preferably 0 or less.

This makes it possible to more reliably prevent phosphorus and heavy metals from being unintentionally redissolved before the completion of the second solid-liquid separation step.

In addition, the amount of phosphorus and heavy metals remaining in the liquid phase can be further reduced while preventing the amount of the material used for raising the pH from becoming excessively large.

In addition, it is possible to obtain a precipitate having an appropriately small particle size and containing a large amount of unstable phosphate crystals. As a result, the phosphate can be dissolved more efficiently in the subsequent second dissolution step.

On the other hand, if the pH of the liquid phase at the end of this step is too low, the precipitation rate of phosphorus decreases and the final recovery rate of phosphorus decreases.

If the pH of the liquid phase at the end of this step is too high, the solubility and dissolution rate of phosphorus contained in the precipitate (second solid) obtained in this step in the alkaline liquid will be low, and the final solution will be The recovery rate of typical phosphorus is reduced.

FIG. 2 is a diagram schematically showing the relationship between the pH of the liquid phase at the end of the first precipitation step and the final recovery rate of phosphorus.

In this step, it is preferable to add calcium so as to satisfy the following conditions. That is, the substance amount of phosphorus in the system at the end of this step _X P [mol], when the substance amount of calcium and _{X Ca [mol], 1.0 ≦} X Ca / X P ≦ 4.0 in Satisfying the relationship, more preferably satisfying the relationship 1.3 ≤ X _Ca / _XP ≤ 3.0, and satisfying the relationship 1.5 ≤ X _Ca / _XP ≤ 2.5. Is even more preferable.

This makes it possible to more preferably precipitate phosphorus contained in the first liquid as a calcium salt of phosphoric acid (for example, to precipitate almost 100%), and phosphorus remaining in the liquid phase in a dissolved state. The ratio of can be made particularly low. In addition, it is possible to more effectively prevent the crystals of the calcium salt of phosphoric acid contained in the precipitate deposited in this step from becoming coarse.

<Second solid-liquid separation step>
In the second solid-liquid separation step, the second solid containing phosphorus and heavy metals is separated from the liquid component.

As a result, it is possible to separate a solid containing a high concentration of phosphorus and a heavy metal (second solid) and a liquid phase containing substantially no heavy metal. In general, the phosphorus content in the liquid phase is sufficiently low.

Such a liquid phase (that is, a liquid phase that does not substantially contain heavy metals and has a sufficiently low phosphorus content) has a small load on the environment and can be drained without any problem. Further, the liquid phase separated into solid and liquid may be reused in the above step. As a result, the liquid containing calcium at a relatively high content can be reused, which is preferable from the viewpoint of further effective utilization of resources.

The method of solid-liquid separation is not particularly limited, and examples thereof include decantation, filtration, centrifugation, and the like, and a plurality of methods may be combined.

Further, in this step, if necessary, the once separated solid phase may be washed with water or the like.
The content of phosphorus in the solid-liquid separated liquid phase is not particularly limited, but is preferably 1000 ppm or less, more preferably 100 ppm or less, and further preferably 10 ppm or less.

The content of heavy metals in the solid-liquid separated liquid phase is not particularly limited, but is preferably 10,000 ppm or less, more preferably 1000 ppm or less, and further preferably 0.1 ppm or less.

<Second dissolution step>
In the second dissolution step, phosphorus contained in the second solid is dissolved with an alkaline liquid.

By using the alkaline liquid in this way, phosphorus can be selectively dissolved while preventing the dissolution of the heavy metal contained in the second solid. In particular, as described above, in the first precipitation step, since the phosphate is precipitated under predetermined conditions, the nucleation and growth of the phosphate are suitably controlled, and the phosphate becomes alkaline. It is in a state where it is easy to dissolve. On the other hand, heavy metals are generally difficult to dissolve in alkaline liquids. As a result, phosphorus as a useful substance that can be used for fertilizers and the like (particularly, a phosphorus-based fertilizer component that can be suitably used in the P component addition step) and heavy metals can be suitably separated. In addition, the final solid waste (industrial waste) can be reduced.

The pH of the alkaline liquid used in this step is not particularly limited, but is preferably 10 or more, more preferably 11 or more and 14 or less, and further preferably 12 or more and 14 or less.

This makes it possible to dissolve phosphorus (phosphate) more efficiently while preventing the redissolution of heavy metals. In addition, it is possible to more reliably prevent phosphorus from being unintentionally deposited before the completion of the third solid-liquid separation step.

The alkaline liquid may be any one that exhibits alkalinity as a whole, and examples of the alkaline substances contained in the alkaline liquid include NaOH, KOH, Mg (OH) ₂ , Ca (OH) ₂ , and Al (OH). ) ₃ metal _hydroxide, CaCO 3, MgCO ₃ or the like of metal carbonates, ammonia, triethylamine, and amine-based materials such as aniline and the like.

Among them, the alkaline liquid used in this step preferably contains a metal hydroxide as an alkaline substance, more preferably contains an alkali metal hydroxide, and further preferably contains NaOH. preferable.

This makes it possible to more efficiently dissolve phosphorus contained in the second solid while more effectively preventing the redissolution of heavy metals. Further, such an alkaline substance is inexpensive and easily available, and is preferable from the viewpoint of cost reduction, stable treatment, and the like.

The pH of the liquid phase at the end of this step is not particularly limited, but is preferably 10 or more, more preferably 11 or more and 14 or less, and further preferably 12 or more and 14 or less.

As a result, phosphorus contained in the second solid can be more efficiently dissolved while more effectively preventing the redissolution of heavy metals, and the amount of the material used for raising the pH becomes larger than necessary. This can be prevented and the amount of phosphorus remaining in the liquid phase can be reduced. In addition, it is possible to more reliably prevent phosphorus from being unintentionally deposited and heavy metals from being unintentionally dissolved before the completion of the third solid-liquid separation step.

<Third solid-liquid separation step>
In the third solid-liquid separation step, the second liquid in which phosphorus is dissolved is separated from the solid component containing heavy metals.

This makes it possible to separate phosphorus and heavy metals. In addition, heavy metals that require strict treatment can be handled as solids, which facilitates the handling of heavy metals. Further, since the volume of the material containing heavy metals can be significantly reduced, for example, even when it is treated as industrial waste, the treatment becomes easy. In addition, the separated liquid phase does not substantially contain heavy metals and therefore does not need to be treated as industrial waste.

The method of solid-liquid separation is not particularly limited, and examples thereof include decantation, filtration, centrifugation, and the like, and a plurality of methods may be combined.

Further, in this step, if necessary, the once separated solid phase may be washed with water or the like.
This makes it possible to lower the phosphorus content in the solid.

The liquid used for washing the solid phase may be combined with the liquid phase obtained by the previous solid-liquid separation after recovery.

The amount of phosphorus in the solid-liquid separated solid phase is not particularly limited, but is 30% by mass or less of the phosphorus content of the sludge ash used as a raw material (that is, the sludge ash used in the first dissolution step). Is preferable, 10% by mass or less is more preferable, and 2% by mass or less is further preferable. The phosphorus content in the solid-liquid separated solid phase is preferably 50% by mass or more, more preferably 90% by mass or more, and further preferably 99% by mass or more.

The content of heavy metals in the solid-liquid separated liquid phase is not particularly limited, but is preferably 1000 ppm or less, more preferably 10 ppm or less, and further preferably 0.01 ppm or less.

<Second precipitation step>
In the present embodiment, after the above-mentioned third solid-liquid separation step, a second precipitation step of mixing the second liquid with a precipitate and lowering the pH to precipitate a third solid containing phosphorus is further performed. Have.

As a result, a highly pure phosphate containing substantially no heavy metal can be obtained as the third solid, and the phosphate can be suitably used as a phosphorus-based fertilizer component in the P component addition step. can. Further, since the phosphate has a high purity, it is suitable for applications other than the phosphorus-based fertilizer component used in the P component addition step. Further, phosphorus can be treated as a phosphate which is a solid substance (for example, calcium hydrogen phosphate dihydrate, calcium phosphate, etc.), and can be more preferably stored and transported.

In this step, any substance or composition may be used as long as it can be mixed with the precipitate and the pH can be lowered, but an acidic liquid having a pH of -1.0 or more and 2.0 or less is used. preferable.

Thereby, the pH of the mixture can be suitably lowered, and the third solid containing phosphorus can be precipitated more efficiently. In addition, it is possible to more reliably prevent phosphorus from being unintentionally redissolved before the completion of the fourth solid-liquid separation step.

In this step, it is preferable to use an acidic liquid having a pH of -1.0 or more and 2 or less, but the pH of the acidic liquid is more preferably -0.5 or more and 1.3 or less, more preferably 0.0 or more. It is more preferably 1.0 or less.

As a result, the above-mentioned effects are more prominently exhibited, and the acidic liquid can be easily and stably obtained or prepared.

In this step, a precipitate having a function of promoting the precipitation of a phosphate or the like may be used, but it is a reactive ionicity which is a hydroxide and / or a salt of an alkali metal and / or a Group 2 element. It is preferable to use a substance.

This makes it possible to adjust the dissolution performance in an alkaline solution, and further, a phosphate can be obtained as a metal phosphate salt which is particularly useful for fertilizers and the like. In addition, the solubility of phosphorus components and the like contained in fertilizer for natural water can be more preferably enhanced.

In particular, the reactive ionic material is preferably a hydroxide and / or salt containing Na and / or Ca.
As a result, the above-mentioned effects are more prominently exhibited.

Above all, in this step, it is preferable to use one or more selected from the group consisting of _{Na 2} CO ₃ , NaOH, CaCO ₃ , Ca (OH) ₂ , CaCl _{2 and NaCl.}

This makes it possible to suitably adjust the pH of the mixture. As a result, in this step, the amount of the substance mixed with the second liquid can be suppressed, and this step can be efficiently advanced. In addition, the content of impurities in the third solid can be further lowered while improving the precipitation efficiency of phosphorus. In addition, it is possible to more reliably prevent phosphorus from being unintentionally redissolved before the completion of the fourth solid-liquid separation step. Further, the solubility of the phosphorus component and the like contained in the fertilizer for natural water can be more preferably adjusted.

In particular, the finally obtained natural water fertilizer shall be set to contain a salt containing Na or Ca as a soluble salt of phosphorus (alkali metal salt of phosphoric acid compound and / or group 2 element salt). Can be done. Examples of such a salt include a salt _{represented by Na x} P _y O _z and Ca _x P _y O _z (where x, y, and z are integers of 1 or more in the formula), CaHPO ₄ , and the like. Examples thereof include salts of hydrogen phosphate compounds such as Ca (H ₂ PO ₄ ) ₂ , NaH ₂ PO ₄ , and Na _{2 HPO 4.} Among them, it is preferable that the salt contains one or more selected from the group consisting of _{Na 3} PO ₄ , Na ₄ P ₂ O ₇ , and Ca ₃ (PO ₄ ) _2.

Further, as the reactive ionic substance, it is preferable to use a hydroxide and / or salt containing Na in combination with a hydroxide and / or salt containing Ca.

As a result, the finally obtained natural water fertilizer can contain both a sodium salt of a phosphoric acid-based compound and a calcium salt of a phosphoric acid-based compound. Since the sodium salt of the phosphoric acid-based compound and the calcium salt of the phosphoric acid-based compound have different solubilities in water, the solubility in natural water can be more preferably adjusted by combining them. For example, while making the elution amount of the phosphorus component (soluble salt) relatively high in the initial stage after application to natural water, the phosphorus component (solubility) after a relatively long period of time has passed since the application to natural water. The elution amount of salt) can also be relatively high.

The pH of the liquid phase at the end of this step is not particularly limited, but is preferably 2.0 or more and 12.0 or less, more preferably 2.5 or more and 10.0 or less, and 3.0 or more. It is more preferably 8.0 or less.

This makes it possible to more reliably prevent phosphorus from being unintentionally redissolved before the completion of the fourth solid-liquid separation step. In addition, the amount of phosphorus remaining in the liquid phase can be further reduced while preventing the amount of the material used for raising the pH from becoming larger than necessary.

In this step, it is preferable to add calcium so as to satisfy the following conditions. That is, the substance amount of phosphorus in the system at the end of this step _X P [mol], when the substance amount of calcium and _{X Ca [mol], 1.0 ≦} X Ca / X P ≦ 4.0 in Satisfying the relationship, more preferably satisfying the relationship 1.3 ≤ X _Ca / _XP ≤ 3.0, and satisfying the relationship 1.5 ≤ X _Ca / _XP ≤ 2.5. Is even more preferable.

As a result, phosphorus contained in the second liquid can be more preferably precipitated as a calcium salt of phosphoric acid, and the proportion of phosphorus remaining in the liquid phase in the dissolved state can be particularly reduced.

<Fourth solid-liquid separation step>
In the present embodiment, after the above-mentioned second precipitation step, there is a fourth solid-liquid separation step for separating a third solid (solid phase) containing phosphorus and a liquid component (liquid phase).

As a result, the material containing phosphorus can be treated as a solid, and the handling thereof becomes easy. Since the separated liquid phase does not substantially contain heavy metals, it is not necessary to treat it as an industrial waste liquid. Further, since the separated liquid phase has a sufficiently low phosphorus content, even if the liquid phase is discarded, it is not disadvantageous from the viewpoint of effective utilization of useful resources. In addition, the separated third solid contains phosphate with high purity and has an extremely low content of heavy metals, so that it is suitable for fertilizers and the like (particularly, phosphorus-based fertilizer components added in the P component addition step). Can be used. In particular, even if post-treatment or the like is not performed, or even when post-treatment is performed, it can be suitably used for fertilizer or the like by simple treatment.

The method of solid-liquid separation is not particularly limited, and examples thereof include decantation, filtration, centrifugation, and the like, and a plurality of methods may be combined.

Further, in this step, if necessary, the once separated solid phase may be washed with water or the like.
This makes it possible to lower the content of ions (cations and anions) in the solid.

The liquid used for washing the solid phase may be combined with the liquid phase obtained by the previous solid-liquid separation after recovery.

The content of heavy metals in the solid-liquid separated solid phase (second solid) is not particularly limited, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and further preferably 10 ppm or less. preferable.

FIG. 8 shows a flowchart of a specific example of the method for producing a fertilizer for natural water of the present invention.

[Fertilizer for natural water]
Next, the fertilizer for natural water of the present invention will be described.

The fertilizer for natural water of the present invention is characterized by using sludge ash as a raw material, containing phosphorus (P), silicon (Si) and iron (Fe), and having a heavy metal content of 1000 ppm or less.

Thereby, it is possible to provide a fertilizer for natural water containing phosphorus, silicon and iron and having a sufficiently low content of heavy metals while effectively utilizing sludge ash. In particular, it is possible to provide a fertilizer for natural water in which the elution rate of fertilizer components is preferably controlled.

Such a fertilizer for natural water of the present invention can be suitably produced by the above-mentioned method.

The content of heavy metals in the fertilizer for natural water of the present invention may be 5000 ppm or less, preferably 500 ppm or less, more preferably 100 ppm or less, still more preferably 10 ppm or less.
As a result, the above-mentioned effect is more prominently exhibited.

The dissolved concentration of heavy metals in the fertilizer for natural water of the present invention is preferably 1 ppm or less, more preferably 100 ppb or less.
As a result, the above-mentioned effect is more prominently exhibited.

The content of phosphorus (P) in the fertilizer for natural water of the present invention is not particularly limited, but is preferably 1.0% by mass or more and 20% by mass or less, and 1.5% by mass or more and 9.0% by mass or less. It is more preferably 2.0% by mass or more and 8.0% by mass or less.

As a result, natural water to which fertilizer for natural water is applied can be eutrophicated at a more appropriate concentration and for a longer period of time while more effectively preventing excessive eutrophication. Fertilizer can be provided. In addition, it becomes easier to adjust the balance with other nutritional components in the fertilizer for natural water to a more suitable one.

The content of silicon (Si) in the fertilizer for natural water of the present invention is not particularly limited, but the content of silicon is preferably 10% by mass or more and 50% by mass or less, and 15% by mass or more and 45% by mass or less. It is more preferably 20% by mass or more and 40% by mass or less.

As a result, natural water to which fertilizer for natural water is applied can be eutrophicated at a more appropriate concentration and for a longer period of time while more effectively preventing excessive eutrophication. Fertilizer can be provided. In addition, it becomes easier to adjust the balance with other nutritional components in the fertilizer for natural water to a more suitable one.

The iron (Fe) content in the fertilizer for natural water of the present invention is not particularly limited, but the iron content is preferably 1.0% by mass or more and 50% by mass or less, and 4.0% by mass or more. It is more preferably 12% by mass or less, and further preferably 5.0% by mass or more and 10% by mass or less.

As a result, natural water to which fertilizer for natural water is applied can be eutrophicated at a more appropriate concentration and for a longer period of time while more effectively preventing excessive eutrophication. Fertilizer can be provided. In addition, it becomes easier to adjust the balance with other nutritional components in the fertilizer for natural water to a more suitable one.

In particular, it is preferable that all of the above three components satisfy the above-mentioned conditions for the content rate.

As a result, the balance of each component becomes more suitable, and the above-mentioned effects are more prominently exhibited.

The content of phosphorus in natural water for fertilizer of the present invention X _{P [wt%],} when the content of silicon in natural water for fertilizer of the present invention was X _{Si [wt%],} 1.0 ≦ X it is preferable to satisfy the relationship _Si / _{X P} ≦ 50.0, more preferably satisfy the relation: _{3.0 ≦ X Si / X P ≦} 30.0, 4.0 ≦ X Si / X P ≦ It is more preferable to satisfy the relationship of 15.0.

This makes the balance between the phosphorus content and the silicon content in the fertilizer for natural water more suitable.

The content of phosphorus in natural water for fertilizer of the present invention X _{P [wt%],} when the content of iron in natural water for fertilizer of the present invention was X _{Fe [wt%],} 0.9 ≦ X it is more preferred that they satisfy the relation of _Fe / _{X P} ≦ 50.0, more preferably satisfy the relation: _{1.0 ≦ X Fe / X P ≦} 30.0, 1.2 ≦ X Fe / X P ≦ It is more preferable to satisfy the relationship of 15.0.

This makes the balance between the phosphorus content and the iron content in the fertilizer for natural water more suitable.

In _{particular, X Si / X P, X} Fe / X P, to satisfy both the conditions preferred.
As a result, the balance of each component becomes more suitable, and the above-mentioned effects are more prominently exhibited.

When the Na content in the fertilizer for natural water is X _Na [mol%] and the content of Ca in the fertilizer for natural water is X _Ca [mol%], 0.01 ≤ X _Ca / X _Na ≤ It is preferable to satisfy the relationship of 100, and more preferably to satisfy the relationship of _{0.1 ≤ X Ca} / X _{Na ≤ 10.}
As a result, the above-mentioned effects are more prominently exhibited.

The sum of the addition, the sum of X _{A [wt%]} of the content and the Al content of Fe in the natural water for fertilizers, and alkali metal content and the content of the second element in the natural water for fertilizers When is X _B [mass%], it _{is preferable to satisfy the relationship of 0.01 ≤ X B} / X _A ≤ 20, and it is more preferable to satisfy the relationship of 0.1 ≤ X _B / X _A ≤ 10. It is preferable to satisfy the relationship of _{0.5 ≦ X B} / X _{A ≦ 3 more preferably.}

As a result, the fertilizer component can be more preferably eluted over a long period of time, and the effect as a fertilizer for natural water can be more preferably exhibited over a long period of time.

The fertilizer for natural water may have any shape, but is preferably granular.
This makes it easier to handle fertilizers for natural water.

When the fertilizer for natural water is granular, the particle size can be adjusted depending on the purpose and environment in which the fertilizer for natural water is used. By changing the particle size of the fertilizer for natural water and the form of administration into natural water, the elution period, the balance between immediate effect and sustainability, and the like can be more preferably adjusted.

When the fertilizer for natural water is granular, it varies depending on the required duration of the fertilizer for natural water and the like, but the average particle size is preferably 1 μm or more and 1.0 m or less, and 2 mm or more and 500 mm or less. Is more preferable.

Thereby, the dissolution rate of the fertilizer for natural water in natural water, the balance between immediate effect and sustainability, and the like can be more preferably adjusted.

The form of administration of the fertilizer for natural water into natural water is not particularly limited as long as it is administered in contact with natural water. It is administered by mixing fertilizer with soil or gravel and laying it on the seabed.

Further, the fertilizer for natural water may be applied to natural water in a state of being contained in a container having an opening smaller than the size of the fertilizer for natural water.

As a result, for example, it is possible to more reliably prevent the solid natural water fertilizer from spreading over a wider range than necessary due to the influence of water flow or the like, and the sufficient effect cannot be obtained in a desired region. Can be done.
As the container, for example, a bag having a mesh may be used.

The constituent material of the bag is not particularly limited, but is preferably a biodegradable material such as iron or polylactic acid.

In addition, fertilizer for natural water is used for structures such as revetment blocks, wave-dissipating blocks, artificial reefs, and embankments that are installed in contact with natural water, especially large concrete fixed objects or buildings as a whole. Alternatively, it may be used in a state of being included in a part.

This makes it possible to more effectively prevent the fertilizer for natural water from being washed away by ocean currents, water currents, and the like. Further, by being contained in concrete or the like, the property of gradually dissolving can be more effectively exhibited, and the effect can be sustained for a longer period of time.

The fertilizer for natural water may be contained in the whole of the structure, or may be contained only in a part of the structure (however, a part that can come into contact with natural water).

When the structure is manufactured, it can be mixed with concrete or the like as a raw material to obtain a structure in which fertilizer for natural water is mixed.

Further, the structure may have a composition containing a fertilizer for natural water attached to the surface thereof. Further, the fertilizer for natural water (the structure) may be used by burying it in the ground as long as it can come into contact with natural water.

This is suitably applied to, for example, a structure that has already been installed in a portion that may come into contact with natural water, a structure that has already been manufactured before installation (for example, a structure that is being prepared for installation, etc.). It is possible, and it is advantageous from the viewpoint of cost and labor. In addition, even when the elution of fertilizer components progresses and the effect as a fertilizer for natural water deteriorates, the fertilizer for natural water is extended for a desired period by reattaching the composition containing the fertilizer for natural water. Can be made to. In addition, the amount of adhered composition containing fertilizer for natural water and the composition of the composition can be adjusted depending on the amount of elution of fertilizer components and growing conditions such as seaweed when applied to natural water, creating a more favorable environment. Can be made up. In addition, in the unlikely event that the amount of elution of fertilizer components becomes excessive, the remaining fertilizer for natural water can be recovered relatively easily.

Further, the composition containing the fertilizer for natural water can be suitably attached to the structure as the base material by, for example, a painting method.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto.

For example, the method for producing a fertilizer for natural water of the present invention may have steps other than the above-mentioned steps (for example, pretreatment step, intermediate treatment step, posttreatment step, etc.).

More specifically, for example, it may have a step of easily solubilizing at least a part (for example, a phosphorus component) of the constituent components of the treated product of sludge ash.

Further, in the above-described embodiment, when the reduction step is provided together with the reactive ionic substance addition step, the solubility of the phosphorus component and the like contained in the fertilizer for natural water can be more preferably enhanced, and iron and silicon can be obtained. Although the elution rate of the above was described as being able to be suitably controlled, when the reactive ionic substance addition step is omitted, that is, at least the first dissolution step, the first solid-liquid separation step and the reduction step are omitted. And a method having a firing step, it is possible to provide a fertilizer for natural water in which the solubility of a fertilizer component, particularly an iron component and a silicon component, is suitably adjusted. (However, the reducing step includes a step of adding a reducing agent.)

Thereby, the solubility of the fertilizer component contained in the fertilizer for natural water can be more preferably enhanced.

Further, the method for producing a fertilizer for natural water of the present invention may include a first dissolution step, a first solid-liquid separation step, a reactive ionic substance addition step, and a firing step. It may not have other steps.

Further, in the above-described embodiment, the case where the reactive ionic substance is added to the first solid in the P component addition step by using the reactive ionic substance in the second precipitation step is typical. As described above, the reactive ionic substance may be added to the first solid in other forms. For example, the method for producing a fertilizer for natural water of the present invention does not have a P component addition step, and a reactive ionic substance is directly added to the first solid separated in the first solid-liquid separation step. You may.

Further, the method for producing a fertilizer for natural water of the present invention may have a first dissolution step, a first solid-liquid separation step, an ionic substance addition step, and a firing step in this order. The order of the other steps is not limited to that described in the above-described embodiment, and the order may be changed. For example, the P component addition step may be provided after the firing step.

Further, the fertilizer for natural water of the present invention is not limited to the fertilizer produced by the above-mentioned method, as long as it is made from sludge ash, contains phosphorus, silicon and iron, and the elution rate of heavy metals is 1000 ppm or less.

Hereinafter, the present invention will be described in detail based on specific examples, but the present invention is not limited thereto.

<< 1 >> Production of fertilizer for natural water (Example 1)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, sodium carbonate as a reactive ionic substance was added at a ratio of 15 parts by mass with respect to 100 parts by mass of the first solid (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, the temperature is first raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 800 ° C. (maximum firing temperature) at a heating rate of 20 ° C./min. The temperature was raised in minutes and held at 800 ° C. (maximum firing temperature) for 2 hours, then lowered to 200 ° C. at a temperature lowering rate of 5 ° C./min, held at 200 ° C. for 2 hours, and then lowered to room temperature. The speed was increased by lowering the temperature at 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Examples 2 to 5)
A fertilizer for natural water was used in the same manner as in Example 1 except that the ratio of sodium carbonate (reactive ionic substance) to be added to 100 parts by mass of the first solid was changed as shown in Table 1. Manufactured.

(Example 6)
Calcium chloride was added to the sample solution prepared using the first liquid in the same manner as in Example 1 so that the ratio of the amount of the eluted phosphorus to the amount of the substance of calcium was 1: 2. The pH was measured using a pH meter while adding a 1 M NaOH solution, and phosphorus and heavy metals were precipitated while stirring (first precipitation step). At this time, phosphorus was mainly precipitated as a phosphate.

After adjusting the pH to 4, the mixture was further stirred for 30 minutes, then the filter paper was set in a filter, and solid-liquid separation was performed using a vacuum pump (second solid-liquid separation step).

Using a 500 mL volumetric flask, the solid-liquid separated filtrate (liquid phase) was measured up.
The volumetric flask was diluted at a specific ratio, the phosphorus concentration was measured by the molybdenum blue absorbance method, and the phosphorus precipitation rate was calculated from the measurement results. A UV spectrophotometer was used to measure the phosphorus concentration.

In addition, the concentrations of metals and heavy metals in the filtrate were determined using ICP-AES and ICP-MS, and the amounts contained in the solid phase and the liquid phase of the metals and heavy metals were calculated.

The solid phase obtained in the second solid-liquid separation step was dried at 105 ° C. for 2 hours, powdered, and analyzed by XRD.

The solid phase obtained in the second solid-liquid separation step was dried, placed in a triangular flask containing 200 mL of 1.0 M NaOH aqueous solution, and stirred at 60 ° C. for 20 minutes. As a result, phosphorus was re-eluted (second dissolution step).

The second liquid (liquid phase) in which phosphorus was dissolved was solid-liquid separated with a filter paper, and separated from the solid component (solid phase) containing heavy metals (third solid-liquid separation step).

Next, calcium chloride was added to the solid-liquid separated second liquid so that the ratio of the amount of phosphorus in the second liquid to the amount of calcium to be added was 1: 2, and 1M was added. The pH was measured using a pH meter while adding hydrochloric acid, and the calcium salt of phosphoric acid was precipitated while stirring (second precipitation step). This step was performed so that the liquid temperature was 20 ° C. or higher and 80 ° C. or lower.

After stirring for another 60 minutes while adjusting the pH between 2.0 and 12, solid-liquid separation was performed to obtain a solid (third solid) mainly composed of a calcium salt of phosphoric acid (fourth solid). Solid-liquid separation step).

Then, a third solid obtained in the fourth solid-liquid separation step was added as a phosphorus-based fertilizer component to the first solid separated in the first solid-liquid separation step at a predetermined ratio (P). Ingredient addition process).

Then, a firing process was performed (firing step). In the firing process, the temperature is first raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 800 ° C. (maximum firing temperature) at a heating rate of 20 ° C./min. The temperature was raised in minutes and held at 800 ° C. (maximum firing temperature) for 2 hours, then lowered to 200 ° C. at a temperature lowering rate of 5 ° C./min, held at 200 ° C. for 2 hours, and then lowered to room temperature. The speed was increased by lowering the temperature at 10 ° C./min.

Then, sodium nitrate as a nitrogen-based fertilizer component was added at a predetermined ratio (N component addition step).
As a result, fertilizer for natural water was obtained.

(Examples 7 to 10)
A fertilizer for natural water was produced in the same manner as in Example 6 except that the pH at the end of the first precipitation step was changed as shown in Table 1.

(Example 11)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, sodium hydroxide as a reactive ionic substance was added at a ratio of 25 parts by mass with respect to 100 parts by mass of the first solid (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, the temperature is first raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature) at a heating rate of 20 ° C./min. The temperature was raised in minutes and held at 900 ° C (maximum firing temperature) for 2 hours, then lowered to 200 ° C at a temperature lowering rate of 5 ° C / min, held at 200 ° C for 2 hours, and then lowered to room temperature. The speed was increased by lowering the temperature at 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 12)
A fertilizer for natural water was produced in the same manner as in Example 11 except that the maximum firing temperature was changed to 600 ° C.

(Example 13)
A fertilizer for natural water was produced in the same manner as in Example 11 except that the maximum firing temperature was changed to 700 ° C.

(Example 14)
A fertilizer for natural water was produced in the same manner as in Example 11 except that the maximum firing temperature was changed to 800 ° C.

(Example 15)
A fertilizer for natural water was produced in the same manner as in Example 11 except that the maximum firing temperature was changed to 1000 ° C.

(Example 16)
A fertilizer for natural water was produced in the same manner as in Example 11 except that the maximum firing temperature was changed to 1100 ° C.

(Example 17)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, calcium carbonate as a reactive ionic substance was added at a ratio of 10 parts by mass with respect to 100 parts by mass of the first solid (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, the temperature is first raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature) at a heating rate of 20 ° C./min. The temperature was raised in minutes and held at 900 ° C (maximum firing temperature) for 2 hours, then lowered to 200 ° C at a temperature lowering rate of 5 ° C / min, held at 200 ° C for 2 hours, and then lowered to room temperature. The speed was increased by lowering the temperature at 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 18)
A fertilizer for natural water was produced in the same manner as in Example 17 except that the ratio of calcium carbonate (reactive ionic substance) to be added to 100 parts by mass of the first solid was changed to 20 parts by mass.

(Example 19)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, sodium hydroxide as a reactive ionic substance was added at a ratio of 25 parts by mass with respect to 100 parts by mass of the first solid (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, the temperature is first raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature) at a heating rate of 20 ° C./min. The temperature is raised in minutes and held at 900 ° C (maximum firing temperature) for 1 hour, then lowered to 200 ° C at a temperature lowering rate of 5 ° C / min, held at 200 ° C for 2 hours, and then lowered to room temperature. The speed was increased by lowering the temperature at 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 20)
A fertilizer for natural water was produced in the same manner as in Example 19 except that the holding time at the maximum firing temperature (900 ° C.) in the firing step was changed to 3 hours.

(Example 21)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 10 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, sodium hydroxide as a reactive ionic substance was added at a ratio of 20 parts by mass with respect to 100 parts by mass of the first solid (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, first, in a nitrogen atmosphere, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature). : Heat up at 20 ° C./min and hold at 900 ° C. (maximum firing temperature) for 2 hours, then down to 200 ° C., lowering rate: 5 ° C./min, hold at 200 ° C. for 2 hours, then The temperature was lowered to room temperature at a temperature lowering rate of 10 ° C./min.
As a result, fertilizer for natural water was obtained.
In this example, regarding the amount of the reactive ionic substance added, the phosphorus content (5% by mass) of the residue is converted into moles, and the amount of the reactive ionic substances added is also converted into moles, and the ratio thereof. showed that. The amount of reducing agent is based on the mass of the residue. The same applies to each of the following examples.

(Example 22)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 10 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, the phosphorus content of the first solid is converted into moles per unit mass of the first solid, and the molar ratio is one tenth of the mole of the contained phosphorus as a reactive ionic substance. Sodium hydroxide was added (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, first, in a nitrogen atmosphere, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature). : Heat up at 20 ° C./min and hold at 900 ° C. (maximum firing temperature) for 2 hours, then down to 200 ° C., lowering rate: 5 ° C./min, hold at 200 ° C. for 2 hours, then The temperature was lowered to room temperature at a temperature lowering rate of 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 23)
A fertilizer for natural water was produced in the same manner as in Example 22 except that the ratio of sodium hydroxide as a reactive ionic substance was changed from 1 tenth to the same amount (1: 1).

(Example 24)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 10 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, the phosphorus content of the first solid is converted into moles per unit mass of the first solid, and the reactive ions are at the same amount (1: 1) with respect to the moles of the contained phosphorus. Sodium hydroxide as a sex substance was added (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, first, in a nitrogen atmosphere, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 500 ° C. (maximum firing temperature). : Heat up at 20 ° C./min and hold at 500 ° C. (maximum firing temperature) for 2 hours, then down to 200 ° C., lowering rate: 5 ° C./min, hold at 200 ° C. for 2 hours, then The temperature was lowered to room temperature at a temperature lowering rate of 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 25)
A fertilizer for natural water was produced in the same manner as in Example 24 except that the maximum firing temperature in the firing step was changed from 500 ° C. to 900 ° C.

(Example 26)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 10 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, the phosphorus content of the first solid is converted into moles per unit mass of the first solid, and the reactive ions are at the same amount (1: 1) with respect to the moles of the contained phosphorus. Sodium hydroxide as a sex substance was added (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, first, in a nitrogen atmosphere, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature). : Heat up at 20 ° C./min and hold at 900 ° C. (maximum firing temperature) for 2 hours, then down to 200 ° C., lowering rate: 5 ° C./min, hold at 200 ° C. for 2 hours, then The temperature was lowered to room temperature at a temperature lowering rate of 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 27)
In the step of adding the reactive ionic substance, a fertilizer for natural water was produced in the same manner as in Example 26, except that sodium hydroxide was changed to calcium hydroxide as the reactive ionic substance.

(Example 28)
In the step of adding the reactive ionic substance, sodium hydroxide (0.5) and calcium hydroxide (0.5) are combined as the reactive ionic substance to the same amount (1: 1) as the molar amount of phosphorus contained. A fertilizer for natural water was produced in the same manner as in Example 26.

(Example 29)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 20 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, the phosphorus content of the first solid is converted into moles per unit mass of the first solid, and water as a reactive ionic substance is used at a ratio of 5 times the mole of the contained phosphorus. Sodium oxide was added (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, first, in a nitrogen atmosphere, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 500 ° C. (maximum firing temperature). : Heat up at 20 ° C./min and hold at 500 ° C. (maximum firing temperature) for 2 hours, then down to 200 ° C., lowering rate: 5 ° C./min, hold at 200 ° C. for 2 hours, then The temperature was lowered to room temperature at a temperature lowering rate of 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 30)
A fertilizer for natural water was produced in the same manner as in Example 29 except that the maximum firing temperature in the firing step was changed to 700 ° C.

(Example 31)
A fertilizer for natural water was produced in the same manner as in Example 30 except that the maximum firing temperature in the firing step was changed to 900 ° C.

(Example 32)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 20 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, the phosphorus content of the first solid is converted into moles per unit mass of the first solid, and the ratio is 0.1 times the mole of the contained phosphorus as a reactive ionic substance. Sodium hydroxide was added (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, the temperature is first raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, held at 200 ° C. for 2 hours, and then raised to 900 ° C. (maximum firing temperature) at a heating rate of 20 ° C./min. The temperature was raised in minutes and held at 900 ° C (maximum firing temperature) for 2 hours, then lowered to 200 ° C at a temperature lowering rate of 5 ° C / min, held at 200 ° C for 2 hours, and then lowered to room temperature. The speed was increased by lowering the temperature at 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 33)
The above-mentioned implementation was carried out except that the phosphorus content of the first solid was converted into moles per unit mass of the first solid and sodium hydroxide was added at a ratio of 5 times the mole of the contained phosphorus. A fertilizer for natural water was produced in the same manner as in Example 32.

(Example 34)
First, sludge ash was prepared and dried at 110 ° C. for 2 hours to set the water content to 0%. This sludge ash contained phosphorus, silicon, iron, aluminum, magnesium and heavy metals.

Next, 200 mL of 1 M hydrochloric acid was placed in a 300 mL Erlenmeyer flask, heated at 80 ° C., 10 g of sludge ash was added into the Erlenmeyer flask, and the mixture was stirred for 40 minutes using a magnetic stirrer. As a result, phosphorus oxide in the sludge was eluted as phosphate ions (first dissolution step).

After stirring for 60 minutes, the filter paper was set in a filter, and the solid phase first solid and the liquid phase first liquid were solid-liquid separated (first solid-liquid separation step). ..

Using a 500 mL volumetric flask, the first liquid, which is a solid-liquid separated filtrate (liquid phase), was made up and used as a sample liquid.

The sample solution was diluted, the phosphorus concentration was measured by the molybdenum blue absorptiometry, and the phosphorus elution rate was calculated from the measurement results. A UV spectrophotometer was used for the analysis of the eluate.

In addition, the concentration of metal / heavy metal in the sample liquid was determined using ICP-AES and ICP-MS, and the amount and liquid phase (first liquid) of the metal / heavy metal contained in the solid phase (first solid). The amount contained in was calculated.

Next, carbon black (reducing agent) was added at a ratio of 10 parts by mass with respect to 100 parts by mass of the first solid (reducing agent addition step).

Next, the phosphorus content of the first solid is converted into moles per unit mass of the first solid, and the ratio is 0.1 times the mole of the contained phosphorus as a reactive ionic substance. Calcium hydroxide was added (reactive ionic substance addition step).

Then, a firing process was performed (firing step). In the firing process, first, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere, and the temperature is maintained at 200 ° C. for 2 hours, and then the temperature is raised to 900 ° C. (maximum firing temperature). The temperature was raised at 20 ° C./min and held at 900 ° C. (maximum firing temperature) for 2 hours, then lowered to 200 ° C. at a temperature lowering rate of 5 ° C./min, held at 200 ° C. for 2 hours, and then at room temperature. The temperature was lowered at a rate of 10 ° C./min.
As a result, fertilizer for natural water was obtained.

(Example 35)
The ratio of calcium hydroxide (reactive ionic substance) to be added to the mole of contained phosphorus in which the phosphorus content of the first solid is converted into moles per unit mass of the first solid has been changed by 10 times. A fertilizer for natural water was produced in the same manner as in Example 34.

(Comparative Example 1)
The sludge ash was used as it was as fertilizer for natural water.

(Comparative Example 2)
A fertilizer for natural water was produced in the same manner as in Example 21 except that the reduction step and the step of adding the reactive ionic substance were omitted.

(Comparative Example 3)
A fertilizer for natural water was produced in the same manner as in Example 26, except that sodium carbonate was not used as the reactive ionic substance.

For Examples 1 to 10 and Comparative Example 1, the ratio of sodium carbonate (reactive ionic substance) added in the reactive ionic substance addition step to 100 parts by mass of the first solid, the first dissolution step, the first. Table 1 summarizes the treatment conditions in the precipitation step 1. In Examples 1 to 10, the phosphorus content in the first solid separated in the first solid-liquid separation step is 1.0% by mass or more and 10.0% by mass or less. The content of heavy metals in the first solid separated in the first solid-liquid separation step was 3% or less of the initial content. Further, in Examples 6 to 10, the phosphorus content in the liquid phase separated in the second solid-liquid separation step is 1% by mass or less, and the separation is performed in the second solid-liquid separation step. The content of heavy metal in the liquid phase was 0.1% by mass or less, and the content of phosphorus in the solid phase separated in the third solid-liquid separation step was 95% by mass. % Or more, and the content of heavy metal in the solid phase separated in the third solid-liquid separation step was 90% or more of the initial content, and was separated in the fourth solid-liquid separation step. The content of heavy metal in the solid phase (third solid) is 1.0% or less of the initial content, and the solid phase (third solid) separated in the fourth solid-liquid separation step. The recovery rate of phosphorus in each was 50% or more of the initial content (maximum 85%). In all of the natural water fertilizers of Examples 1 to 10, the phosphorus content is in the range of 1.0% by mass or more and 10% by mass or less, and the silicon content is 10% by mass or more and 50% by mass or less. The iron content was in the range of 3.0% by mass or more and 50.0% by mass or less, and the heavy metal content was 100 ppm or less. Further, X _{P [wt%]} of the content of phosphorus in natural water for fertilizers, the content of silicon X _{Si [mass%],} when the content of iron was X _{Fe [wt%],} Example 1-10 natural water fertilizers are both relationships _{4.0 ≦ X Si / X P ≦} 15, and satisfied the relationship of _{3 ≦ X Fe / X P ≦} 20.0. Moreover, when the components of the fertilizers for natural water of Examples 1 to 10 were analyzed by X-ray diffraction (XRD), it was confirmed that all of them contained sodium phosphate. In addition, the fertilizers for natural water obtained in Examples 1 to 10 were all granular, and the average particle size thereof was 3 mm or more and 10 mm or less. In addition, the natural water fertilizers obtained in Examples 1 to 10 all have a content of soluble salts (alkali metal salts of phosphoric acid compounds and / or group 2 element salts) of 3.0 mass. It was more than%. On the other hand, the content of heavy metals in the fertilizer for natural water of Comparative Example 1 was 1000 ppm or less, and the dissolution concentration was 100 ppb or less.

<< 2 >> Evaluation << 2-1 >> Confirmation of elution rate of iron, etc. from sludge ash First, 10 g of sludge ash (fertilizer for natural water of Comparative Example 1) was added to 200 mL of 1 M hydrochloric acid and sufficiently stirred. The elution rate of iron etc. was confirmed.
The results are shown in FIG.

As is clear from FIG. 3, the elution rate of iron from sludge ash within 60 minutes is 20% or less, and from this result, the fertilizer for natural water of the above-mentioned example treated with acid (hydrochloric acid) in the manufacturing process. It can be seen that iron is contained (remains) in a high content rate.

<< 2-2 >> Evaluation of Phosphorus Elution Rate 1 g of the fertilizer for natural water of Examples 1 to 10 and Comparative Example 1 were added to 500 mL of a 3.5 mass% sodium chloride aqueous solution, respectively, and at 25 ° C. It was left still.
At this time, the elution rate of phosphorus contained in the fertilizer for natural water was measured over 30 days.

FIG. 4 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 1 to 5 and Comparative Example 1 to the aqueous solution of sodium chloride and the elution rate of the phosphorus component.

As is clear from FIG. 4, in Comparative Example 1 in which sludge ash was used as it was, the elution rate of the phosphorus component in 30 days was about 0.5%, whereas in Examples 1 to 5, any of them It can be seen that the solubility is improved. Further, it can be seen that the elution rate of phosphorus in the fertilizer for natural water can be changed by changing the concentration of the reactive ionic substance. More specifically, in the range of Examples 1 to 5, the elution rate can be increased by increasing the ratio of the reactive ionic substance, and the elution rate of phosphorus can be increased in the range of about 5% to 50%. Was adjustable. From this, it is possible to control the elution rate of the phosphorus component from the fertilizer for natural water by the amount of the reactive ionic substance used. It can be said that the balance between immediate effect and sustainability can be adjusted to correspond to the characteristics to be treated.

Further, in Examples 1 to 5, it was confirmed that the elution rate of phosphorus increased even after the lapse of 30 days. From this, it is estimated that the phosphorus component can be eluted for 2 years in the estimation, and in this case, about 80% of the phosphorus contained in the sludge ash can be eluted.

Further, also in Examples 6 to 10 in which the reactive ionic substance (CaCl ₂ ) was used in the second precipitation step, excellent results were obtained as in Examples 1 to 5.

In addition, natural water was used in the same manner as in Examples 1 to 10 except that CaCO ₃ , NaOH, Ca (OH) _{2 and NaCl were used instead of Na 2} CO ₃ and CaCl ₂ as the reactive ionic substance. Excellent results were obtained in all of the fertilizers produced.

Further, the heating temperature of the heat treatment is changed within the range of 150 ° C. or higher and 1500 ° C. or lower, and the heat treatment treatment time (heating time at a temperature of 150 ° C. or higher) is within the range of 1 hour or more and 100 hours or less. When fertilizers for natural water were produced in the same manner as in Examples 1 to 10 except for the changes in the above, excellent results were obtained in all cases.

Further, when the same method as in Examples 1 to 10 was carried out except that the acidic liquid used in the first dissolution step was changed in the range of pH of −1.0 or more and 1.5 or less, all of them were carried out. Excellent results were obtained.

Further, regarding Examples 6 to 10, the ratio of the extracted phosphorus to the total amount of phosphorus contained in the sludge ash as a raw material (recovered as a third solid separated in the fourth solid-liquid separation step). The ratio of phosphorus) was calculated.

In addition, the content of heavy metals with respect to the total solid content contained in the object (third solid separated in the fourth solid-liquid separation step) for which the amount of phosphorus extracted was determined as described above was determined.

The amount of phosphorus elution and the amount of precipitation were calculated from the results of quantifying the phosphoric acid concentration by the molybdenum absorptiometry. The behavior of metals and heavy metals during elution and precipitation was calculated by ICP spectroscopic analysis (ICP-AES), ICP mass analysis (ICP-MS), and elemental analysis equipment. The precipitates were identified by using the X-ray diffraction (XRD) method and the ICP-MS method.
These results are summarized in Table 2.

FIG. 5 shows the correspondence between the pH of the liquid phase at the end of the first precipitation step and the X-ray diffraction (XRD) pattern of the precipitate in Examples 6, 7 and 8.

Further, regarding the third solid obtained in the process of producing the fertilizer for natural water of Example 6, the recovery rate of phosphorus and the main metal element (in the third solid with respect to the amount contained in the sludge ash as a raw material). The ratio of the amount contained in the above) is shown in FIG. The recovery rate of arsenic (As) in the third solid is higher than that of other heavy metals, but the content of arsenic in the third solid is 46.4 mg / kg, which is a standard value for fertilizer. It is significantly lower than 1400 mg / kg, and it is considered that there is no problem in safety.

In addition, the third solid obtained in the process of producing the fertilizer for natural water of Examples 6 to 10 was determined by the Food and Agricultural Materials Safety Technology Center (FAMIC) for the purpose of evaluating the suitability as a fertilizer. The water solubility test and the solubility test were carried out with reference to the fertilizer analysis method used.

In the water-soluble test, the amount of solvent (water) was 12 mL with respect to 0.15 g of the sample (third solid), and after stirring at room temperature for 30 minutes, solid-liquid separation was performed, and the dissolved phosphorus concentration was determined by the molybdenum absorptiometry. The phosphorus elution rate was calculated.

In the solubility test, 8 mL of an aqueous citric acid solution was added to 0.10 g of a sample (third solid), and elution was performed with stirring at 30 ° C. for 60 minutes. Here, the citric acid solution used is 100 g of citric acid monohydrate dissolved in 100 mL of water, and the solution is diluted 5-fold.

As a result, all of the third solids obtained in Examples 6 to 10 had a small amount of elution with water, but a large amount of citric acid elution.

Representatively, FIG. 7 shows the results of a water solubility test and a solubility test on a third solid obtained in the process of producing the fertilizer for natural water of Example 6.

Further, the same method as in Examples 6 to 10 was carried out except that the amount of the alkaline liquid used was changed so that the pH of the liquid phase at the end of the first precipitation step was 2.0 or more and 10 or less. However, the same result as described above was obtained.

Further, the substance amount of phosphorus in the system at the end of the first precipitation step _X P [mol], when the substance amount of calcium was _X Ca _[mol], the value of X Ca / _{X P} 1.3 When the same method as in Examples 6 to 10 was performed except that the amount of the precipitate used was changed so as to be 3.0 or less, the same result as described above was obtained.

Further, the same method as in Examples 6 to 10 is used except that the amount of the acidic liquid used is changed so that the pH of the liquid phase at the end of the second precipitation step is 2.0 or more and 12.0 or less. As a result, the same result as described above was obtained.

Further, when the same method as in Examples 6 to 10 was carried out except that the acidic liquid used in the second precipitation step was changed in the range of −1.0 or more and 2 or less, the same result as described above was performed. was gotten.

Further, the substance amount of phosphorus in the system at the end of the second precipitation step _X P [mol], when the substance amount of calcium was _X Ca _[mol], the value of X Ca / _{X P} 1.3 When the same method as in Examples 6 to 10 was performed except that the amount of the precipitate used was changed so as to be 3.0 or less, the same result as described above was obtained.

Further, the same method as in Examples 6 to 10 was performed except that Ca (OH) ₂ and CaCO _{3 were used instead of CaCl 2} in the first precipitation step and the second precipitation step. The same result as above was obtained.

FIG. 9 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 11 to 16 to the aqueous sodium chloride solution and the elution rate of the phosphorus component.

As is clear from FIG. 9, it can be seen that the elution rate of the phosphorus component of the fertilizer for natural water can be changed by changing the firing temperature in the firing step. From this, the elution rate of the phosphorus component from the fertilizer for natural water can be controlled by the calcination temperature in the calcination step. It can be said that the balance between immediate effect and sustainability can be adjusted so as to correspond to.

FIG. 10 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 17 and 18 to the aqueous sodium chloride solution and the elution rate of the phosphorus component.

As is clear from FIG. 10, similar to FIG. 4 showing the results of Examples 1 to 5 in which sodium carbonate was used as the reactive ionic substance, the reactivity was also obtained when calcium carbonate was used as the reactive ionic substance. It can be seen that the elution rate of the phosphorus component of the fertilizer for natural water can be changed by changing the concentration of the ionic substance. From this, it is possible to control the elution rate of the phosphorus component from the fertilizer for natural water by the amount of the reactive ionic substance used. It can be said that the balance between immediate effect and sustainability can be adjusted to correspond to the characteristics to be treated.

FIG. 11 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 19 and 20 to the aqueous sodium chloride solution and the elution rate of the phosphorus component.

As is clear from FIG. 11, it can be seen that the elution rate of the phosphorus component of the fertilizer for natural water can be changed by changing the firing time in the firing step. From this, it is possible to control the elution rate of the phosphorus component from the fertilizer for natural water by the firing time in the firing step. It can be said that the balance between immediate effect and sustainability can be adjusted so as to correspond to.

FIG. 12 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Example 21 and Comparative Example 2 to the aqueous sodium chloride solution and the elution rate of the iron component.

As is clear from FIG. 12, the elution rate of the iron component is significantly improved by performing the reduction step using the reducing agent together with the step of adding the reactive ionic substance. From this, it can be said that the iron component contained in the sludge ash as a raw material has been changed to a highly soluble state by the reduction step.

FIG. 13 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 22 and 23 to the aqueous sodium chloride solution and the elution rate of the iron component.

As is clear from FIG. 13, the elution rate of the iron component from the fertilizer for natural water finally changes depending on the amount of the reducing agent used in the reducing step. From this, it is possible to control the elution rate of the iron component from the fertilizer for natural water by the amount of the reducing agent used. It can be said that the balance between immediate effect and sustainability can be adjusted accordingly.

FIG. 14 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 24 and 25 to the aqueous sodium chloride solution and the elution rate of the iron component.

As is clear from FIG. 14, the elution rate of the iron component from the fertilizer for natural water finally changes depending on the firing temperature in the firing step. From this, it is possible to control the elution rate of the iron component from the fertilizer for natural water by the firing temperature, and for example, it corresponds to the required characteristics according to the usage pattern, the place of use, etc. of the fertilizer for natural water. In addition, it can be said that the balance between immediate effect and sustainability can be adjusted.

FIG. 15 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 26 to 28 and Comparative Example 3 to the aqueous solution of sodium chloride and the elution rate of the silicon component.

As is clear from FIG. 15, in Comparative Example 3 in which the reactive ionic substance was not used, the elution rate of silicon was low, whereas in Examples 27 to 29 using the reactive ionic substance, the silicon component was found. The elution rate is improved. From this, it can be said that the silicon component contained in the sludge ash as a raw material has been changed to a highly soluble state by the use of the reactive ionic substance. Further, from Examples 27 to 29, it can be seen that the elution rate of the silicon component of the fertilizer for natural water can be changed depending on the type of the reactive ionic substance. From this, it is possible to control the elution rate of the silicon component from the fertilizer for natural water by the amount of the reactive ionic substance used. It can be said that the balance between immediate effect and sustainability can be adjusted to correspond to the characteristics to be treated.

FIG. 16 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 29 to 31 to the aqueous sodium chloride solution and the elution rate of the silicon component.

As is clear from FIG. 16, the elution rate of the silicon component from the fertilizer for natural water finally changes depending on the firing temperature in the firing step. From this, it is possible to control the elution rate of the silicon component from the fertilizer for natural water by the firing temperature, and for example, it corresponds to the required characteristics according to the usage pattern, the place of use, etc. of the fertilizer for natural water. In addition, it can be said that the balance between immediate effect and sustainability can be adjusted.

FIG. 17 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 32 and 33 to the aqueous sodium chloride solution and the elution rate of the silicon component.

As is clear from FIG. 17, it can be seen that the elution rate of the silicon component of the fertilizer for natural water can be changed by changing the concentration of the reactive ionic substance. From this, it is possible to control the elution rate of the silicon component from the fertilizer for natural water by the amount of the reactive ionic substance used. It can be said that the balance between immediate effect and sustainability can be adjusted to correspond to the characteristics to be treated.

FIG. 18 is a diagram showing the relationship between the number of days elapsed from the addition of the fertilizer for natural water according to Examples 34 and 35 to the aqueous sodium chloride solution and the elution rate of the silicon component.

As is clear from FIG. 18, similar to FIG. 17 showing the results of Examples 32 and 33 in which sodium hydroxide was used as the reactive ionic substance, even when calcium hydroxide was used as the reactive ionic substance, as in FIG. It can be seen that the elution rate of the silicon component of the fertilizer for natural water can be changed by changing the concentration of the reactive ionic substance. From this, it is possible to control the elution rate of the silicon component from the fertilizer for natural water by the amount of the reactive ionic substance used. It can be said that the balance between immediate effect and sustainability can be adjusted to correspond to the characteristics to be treated.

In the method for producing a fertilizer for natural water of the present invention, a first dissolution step of mixing sludge ash and an acidic liquid to dissolve heavy metals and phosphorus contained in the sludge ash, and the dissolution of the heavy metals and phosphorus. A first solid-liquid separation step of separating and removing the first liquid from the first solid, and a hydroxide and / or salt of an alkali metal and / or a Group 2 element with respect to the first solid. It has a step of adding a reactive ionic substance to which a reactive ionic substance is added, and a firing step of subjecting the composition containing the first solid and the reactive ionic substance to a firing treatment. Further, the fertilizer for natural water of the present invention is made from sludge ash, contains phosphorus, silicon and iron, and has a heavy metal content of 1000 ppm or less. Therefore, to provide a fertilizer for natural water containing phosphorus, silicon and iron and having a sufficiently low content of heavy metals while effectively utilizing sludge ash, and to provide a method for producing the fertilizer for natural water. be able to. In particular, it is possible to provide a fertilizer for natural water in which the elution rate of a fertilizer component is suitably controlled, and to provide a method for producing the fertilizer for natural water. Therefore, the method for producing a fertilizer for natural water and the fertilizer for natural water of the present invention have industrial applicability.

Claims (16)

The first melting step of mixing sludge ash and an acidic liquid to dissolve heavy metals and phosphorus contained in the sludge ash, and
A first solid-liquid separation step of separating and removing the first liquid in which heavy metals and phosphorus are dissolved from the first solid,
A step of adding a reactive ionic substance, which is a hydroxide and / or a salt of an alkali metal and / or a Group 2 element, to the first solid.
A method for producing a fertilizer for natural water, which comprises a calcining step of subjecting a composition containing the first solid and the reactive ionic substance to a calcining treatment. The method for producing a fertilizer for natural water according to claim 1, wherein the reactive ionic substance is a hydroxide and / or a salt containing Na and / or Ca. _{The natural substance according to claim 2} , wherein the reactive ionic substance is one or more selected from the group consisting of Na 2 CO ₃ , NaOH, CaCO ₃ , Ca (OH) ₂ , CaCl _{2 and NaCl.} How to make water fertilizer. The method for producing a fertilizer for natural water according to any one of claims 1 to 3, wherein the firing temperature in the firing treatment is 150 ° C. or higher and 1100 ° C. or lower. The method for producing a fertilizer for natural water according to any one of claims 1 to 4, wherein the processing time of the firing treatment is 0.5 hours or more and 100 hours or less. The method for producing a fertilizer for natural water according to any one of claims 1 to 5, further comprising a reducing step of adding a reducing agent to the first solid to perform a reducing treatment. The method for producing a fertilizer for natural water according to any one of claims 1 to 6, further comprising an N component adding step of adding a nitrogen-based fertilizer component into the system after the first solid-liquid separation step. .. The method for producing a fertilizer for natural water according to any one of claims 1 to 7, further comprising a P component adding step of adding a phosphorus-based fertilizer component into the system after the first solid-liquid separation step. .. The phosphorus-based fertilizer component is
The first precipitation step of mixing the first liquid separated in the first solid-liquid separation step with a precipitate and raising the pH to precipitate a second solid containing the heavy metal and phosphorus.
The second solid-liquid separation step of separating the second solid from the liquid component,
A second dissolution step of dissolving phosphorus contained in the second solid with an alkaline liquid, and
The production of fertilizer for natural water according to claim 8, wherein the second liquid in which phosphorus is dissolved is separated by a method having a third solid-liquid separation step of separating the solid component containing a heavy metal from the solid component. Method. After the third solid-liquid separation step, the phosphorus-based fertilizer component mixes the second liquid with a precipitate and lowers the pH to precipitate a third solid containing phosphorus. The method for producing a fertilizer for natural water according to claim 9, which is obtained by using a method further comprising a step. The method for producing a fertilizer for natural water according to claim 10, wherein the pH of the liquid phase at the end of the second precipitation step is 2.0 or more and 12.0 or less. The method for producing a fertilizer for natural water according to claim 10 or 11, wherein an acidic liquid having a pH of −1.0 or more and 2.0 or less is used in the second precipitation step. The method for producing a fertilizer for natural water according to any one of claims 10 to 12, wherein the reactive ionic substance is used in the second precipitation step. Using sludge ash as a raw material
Contains phosphorus, silicon and iron,
A fertilizer for natural water characterized by a heavy metal content of 1000 ppm or less. The phosphorus content is 1.0% by mass or more and 10% by mass or less.
The silicon content is 10% by mass or more and 50% by mass or less.
The fertilizer for natural water according to claim 14, wherein the iron content is 1.0% by mass or more and 50% by mass or less. When the phosphorus content is _XP [mass%], the silicon content is X _Si [mass%], and the iron content is X _Fe [mass%], 1.0 ≤ X _Si / _XP ≤ 50. .0, and natural water fertilizer according to claim 14 or 15 satisfies the relation of _{0.9 ≦ X Fe / X P ≦} 50.0.

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