JP2006205154A - Method for manufacturing adsorbent consisting essentially of hydroxyapatite crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an adsorbent consisting essentially of hydroxyapatite with ease and at a low cost from gypsum and sewage sludge incineration ash or dried and solidified sewage sludge or sewage sludge subjected to carbonization treatment without deposition of aluminum hydroxide, without production of ammonia at the time of manufacturing and with ease treatment of a waste solution and to obtain the adsorbent which has acid resistance and high adsorption effect and which is effective to a countermeasure against water pollution and soil pollution. <P>SOLUTION: The sewage sludge incineration ash or dried and solidified sewage sludge or sewage sludge subjected to carbonization treatment is agitated in an alkaline solution and then filtration separation is carried out to obtain a solution. Gypsum is charged to the solution and then agitation at 40 to 100°C is carried out while holding pH at 13 to 14.9 at the time of reaction initiation and at ≥12 at the time of reaction ending. Thus phosphoric acid and gypsum in the alkaline solution are made to react with each other to manufacture the adsorbent consisting essentially of a hydroxyapatite crystal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an adsorbent mainly composed of hydroxyapatite crystals using gypsum and sewage sludge incineration ash, dried and solidified sewage sludge or carbonized sewage sludge, and an environment obtained from this method. It relates to an adsorbent that adsorbs heavy metals in water and soil. Further, in detail, the present invention can use waste gypsum as gypsum, and among wastes that are disposed of in landfills, the amount of disposal is extremely large and has become a social problem, gypsum board waste and sewage sludge incineration The present invention relates to a method for producing an adsorbent capable of utilizing ash or sewage sludge.

Hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ) is known to be rich in adsorptivity accompanied by ion exchange with respect to specific inorganic ions, among calcium phosphate compounds. Hydroxyapatite crystals have the property of selectively adsorbing lead, cadmium, fluorine, tin, uranium or rare earth elements yttrium and lanthanum at normal pressure, and are used as water purification materials and soil purification materials. Is also being used.

  For the purpose of synthesizing a large amount of hydroxyapatite, an alkaline aqueous solution mixing method in which calcium nitrate and ammonium phosphate are mixed has been conventionally used, as reported by Jarcho (Non-patent Document 1). Recently, as a method for producing hydroxyapatite from gypsum waste, Furuta has proposed a method for producing hydroxyapatite using gypsum (calcium sulfate) instead of calcium nitrate in the Jarcho method (patent document). 1, Non-Patent Document 2). Most of the gypsum board waste discharged with the dismantling of the building is disposed of in landfill, and the method using this gypsum board waste is an epoch-making method.

JP 2004-284890 A 1976, J.of Material Sci., 11, p.2027-2030 1998, J. Mater. Chem., 8, 2803-2806

  However, these methods use a chemical ammonium phosphate salt as a phosphoric acid source, so the cost of the raw material is high.

  In addition, the ammonia component in the solution is volatilized in the air during the hydrothermal synthesis process using a salt containing ammonia, so it is necessary to consider work safety and the surrounding environment for large-scale production. Sealing, ventilation, etc. There is also a problem that the equipment cost is high.

  In addition, phosphate ore as a raw material for phosphoric acid is currently being exhausted worldwide, and considering this situation, development of a new synthesis method using a recycled phosphoric acid raw material is desired. For example, if phosphorous contained in sewage sludge incineration ash, dried / solidified sewage sludge or carbonized sewage sludge can be used, this problem can be solved.

  More than 1 million tons of gypsum board waste discharged with the dismantling of buildings is discharged annually (estimated in 2001), and most of it is landfilled. On the other hand, more than 700,000 tons of sewage sludge incineration ash is disposed of in landfills each year (fiscal 2001), both of which are large in volume, and this is a factor that puts pressure on the capacity of recent waste disposal sites. Effective use of gypsum board waste, sewage sludge and sewage sludge incineration ash if adsorbents can be synthesized using gypsum board waste and sewage sludge incineration ash, dried and solidified sewage sludge, or carbonized sewage sludge It is possible to provide an inexpensive environmental purification material.

  However, using sewage sludge incinerated ash, dried / solidified sewage sludge or carbonized sewage sludge extracted with an alkaline solution as it is, mixed with gypsum and reacted to obtain hydroxyapatite. Then, the following problems arise.

  In the course of reaction between gypsum and phosphoric acid, when gypsum crystallizes apatite, sulfate ions are separated from gypsum, and the pH changes in principle to the lower side. Due to this decrease in pH, when a large amount of aluminum ions coexists in the phosphoric acid-containing extraction solution, aluminum hydroxide precipitates simultaneously during the pH decrease process, making it difficult to separate from the hydroxyapatite crystals thereafter. It becomes.

  In addition, when the waste liquid obtained by solid-liquid separation of hydroxyapatite after the reaction contains a lot of aluminum ions, it is usually neutralized to near neutrality and precipitated in the form of aluminum hydroxide. The water content is high and generally dehydration and separation are not easy.

  On the other hand, with respect to the obtained hydroxyapatite, the hydroxyapatite crystals produced by the conventional method are unstable under a weakly acidic environment at pH 5.5 or less, and may be decomposed in a short period of time when added to acidic soil. There is also a need to improve acid resistance.

  Therefore, the present invention is based on gypsum and sewage sludge incineration ash, dried and solidified sewage sludge or carbonized sewage sludge without precipitation of aluminum hydroxide, production of ammonia during production, and A method for producing an adsorbent composed mainly of hydroxyapatite that is easy to process and inexpensive, and an adsorbent that is acid resistant, has a high adsorbing effect, and is effective for water and soil contamination countermeasures. For the purpose.

  In order to achieve this object, the method for producing an adsorbent mainly composed of hydroxyapatite crystals according to claim 1 is a solution obtained by stirring and separating sewage sludge incineration ash in an alkaline solution. The gypsum is added, the pH at the start of the reaction is set to 13 to 14.9, the mixture is stirred at 40 to 100 ° C., and the pH at the end of the reaction is maintained at 12 or more, so that phosphoric acid in the alkaline solution The gypsum is made to react.

  According to a second aspect of the present invention, there is provided a method for producing an adsorbent comprising hydroxyapatite crystals as a main component, wherein dried and solidified sewage sludge or carbonized sewage sludge is stirred in an alkaline solution and then filtered and separated. Gypsum is added to the obtained solution, the pH at the start of the reaction is set to 13 to 14.9, the mixture is stirred at 40 to 100 ° C., and the pH at the end of the reaction is maintained at 12 or more in an alkaline solution. The phosphoric acid and gypsum are made to react.

  By stirring the sewage sludge incineration ash, which is a waste, with an alkaline solution, phosphorus contained in the sewage sludge incineration ash can be extracted as phosphoric acid in the alkaline solution. And by making the said phosphoric acid and gypsum react on the said conditions, precipitation of aluminum hydroxide can be prevented and the adsorbent which has a hydroxyapatite crystal as a main component can be obtained with high purity and high yield cheaply. it can.

  In addition, even when using dried and solidified sewage sludge or carbonized sewage sludge, it is possible to extract phosphorus in the same manner as when using sewage sludge incineration ash, so even if these are used, The hydroxyapatite crystal of the present invention can be obtained by a similar method.

  Furthermore, as described in claim 3, it is preferable to use waste gypsum as gypsum. Therefore, waste gypsum can be recycled and cost reduction can be achieved.

  The method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to claim 4 is the method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to any one of claims 1 to 3, The alkaline solution is a potassium hydroxide solution having a concentration in the range of 1.5 to 3.0 mol / L, and the ratio of the alkaline solution to the sewage sludge incineration ash, the dried / solidified sewage sludge or the carbonized sewage sludge is solid. The liquid ratio (L / S) is 2 to 10 (liter / kg), and the amount of gypsum to be added is the molar ratio of Ca contained in the gypsum and P contained in the solution obtained by filtration and separation. Is 10: 6.

  By using a potassium hydroxide solution having an alkaline solution having a concentration in the range of 1.5 to 3.0 mol / L, the pH at the start of the reaction is set to 13 to 14.9, and the pH at the end of the reaction is set to 12 or more. Since it can hold | maintain, it becomes difficult to precipitate aluminum hydroxide. In addition, the ratio of the alkaline solution to the sewage sludge incineration ash, the dried and solidified sewage sludge or the carbonized sewage sludge is 2 to 10 (liter / kg) in terms of the solid-liquid ratio (L / S), thereby phosphoric acid. Can be extracted efficiently. Furthermore, leaving the unreacted gypsum by setting the molar ratio of Ca contained in the gypsum and P contained in the solution obtained by filtration separation to 10: 6 which is a hydroxyapatite stoichiometric ratio. And hydroxyapatite crystals can be produced.

  The method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to claim 5 is the method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to any one of claims 1 to 3, The alkaline solution is a potassium hydroxide solution having a concentration in the range of 0.1 to 3.0 mol / L, and the ratio of the alkaline solution to the sewage sludge incineration ash, the dried / solidified sewage sludge or the carbonized sewage sludge is solid. The liquid ratio (L / S) is 2 to 10 (liter / kg), and the amount of gypsum to be added is the molar ratio of Ca contained in the gypsum and P contained in the solution obtained by filtration and separation. Is 10: 6, and at the time of gypsum injection, potassium hydroxide equivalent to 0.3 to 1 times the molar amount of gypsum input is further added to adjust the pH at the start of the hydrothermal reaction to 13 to 14. 9 is held.

  By adding potassium hydroxide equivalent to 0.3 to 1 times the molar amount of gypsum charged at the time of gypsum charging, the pH at the start of the reaction is 13 to 14.9, and the pH at the end of the reaction is increased to 12 or more. Can be held. Therefore, precipitation of aluminum hydroxide can be prevented, and high-purity hydroxyapatite crystals can be obtained with high yield.

  The method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to claim 6 is the method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to any one of claims 1 to 5, After completion of the reaction, sulfuric acid is added to the high-temperature waste liquid obtained by solid-liquid separation of the adsorbent, and the pH is adjusted to 3 or less, and then cooled to precipitate potassium alum and separate the aluminum ion and sulfate ion in the waste liquid. The process is included.

Potash alum is highly temperature-dependent and dissolves at 710 g / L at 80 ° C., whereas only 59 g / L can be dissolved at 20 ° C. (FIG. 2). Therefore, after the reaction is completed, the adsorbent is subjected to solid-liquid separation while the solution is at a high temperature, and sulfuric acid is added to the obtained waste liquid at a high temperature, neutralized to a pH of 3 or less, and then the potassium alum (AlK (SO ₄ ) By precipitating ₂ ), alum can be efficiently precipitated from the liquid phase as the temperature is lowered, which facilitates waste liquid treatment.

  The method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to claim 7 is the method for producing an adsorbent mainly comprising a hydroxyapatite crystal according to any one of claims 1 to 6, The waste liquid obtained by solid-liquid separation of the adsorbent after completion of the reaction is used as the alkaline solution.

  The aluminum concentration in the liquid phase is limited by the solubility of amorphous aluminum hydroxide. Therefore, wastewater containing aluminum obtained by solid-liquid separation of the adsorbent after completion of the reaction is used for phosphorus extraction from sewage sludge incineration ash, dried and solidified sewage sludge, or carbonized sewage sludge, so that sewage sludge can be used. New inflow of aluminum from incinerated ash, dried and solidified sewage sludge or carbonized sewage sludge can be reduced, and the amount of final waste liquid that needs to be treated can be reduced. The amount of alum generated can be reduced. Furthermore, the amount of potassium hydroxide used in the elution process of sewage sludge incineration ash, dried / solidified sewage sludge or carbonized sewage sludge can be reduced.

  Furthermore, the invention according to claim 8 obtained by the production method described above relates to an adsorbent mainly composed of hydroxyapatite crystals that exhibit alkalinity when in contact with water. Since this adsorbent is mainly composed of hydroxyapatite crystals that exhibit alkalinity when in contact with water, it does not easily decompose even in an acidic atmosphere, and the adsorbing effect can be maintained.

The invention according to claim 9 obtained by the above production method relates to an adsorbent in which the composition of hydroxyapatite crystals is silica-containing hydroxyapatite. Since the hydroxyapatite crystal which is the main component of this adsorbent contains silica, it can ion-remove a large amount of various cations, and in particular, adsorbs more Mn ²⁺ , Zn ²⁺ and Cd ^2+. Excellent cation exchange characteristics such as excellent adsorption characteristics.

  According to the present invention, for the synthesis of hydroxyapatite, two wastes of sewage sludge incineration ash, dried and solidified sewage sludge or sewage sludge and waste gypsum can be used as raw materials, and the hydroxyapatite can be inexpensively produced. It is possible to obtain In addition, by promoting the recycling of both these wastes, it can be expected to reduce the amount of waste landfill disposal.

  In addition, sewage sludge incineration ash, dried and solidified sewage sludge or carbonized sewage sludge alkaline extract is used as raw materials as it is, so conventional sewage sludge incineration ash, dried and solidified sewage sludge or carbonized. In addition, it is not necessary to carry out separation treatment of aluminum necessary for separation and extraction of phosphorus from sewage sludge.

  Furthermore, in the treatment of waste liquid, utilizing the fact that the solution after hydrothermal synthesis is still hot, sulfuric acid is added to the solution, and potassium alum with high temperature dependence of solubility is precipitated, thereby adding new heating energy. At least, it is possible to efficiently remove aluminum and sulfate ions in the solution.

  In addition, the waste liquid containing aluminum obtained by solid-liquid separation of the adsorbent after completion of the reaction is used for phosphorus extraction from sewage sludge incineration ash, dried and solidified sewage sludge, or carbonized sewage sludge. New inflow of aluminum from incinerated ash, dried / solidified sewage sludge or carbonized sewage sludge can be reduced, and the amount of waste liquid that ultimately needs to be treated can be reduced. Reduces the amount of certain potassium alum generated. The amount of potassium hydroxide used in the phosphoric acid extraction process of sewage sludge incineration ash, dried / solidified sewage sludge or carbonized sewage sludge can also be reduced.

  Hydroxyapatite crystals obtained by the present invention have the property of exhibiting weak alkalinity when contacted with water, and can generally exist more stably even when added to acidic soil where heavy metal elution tends to become apparent.

  In addition, since no ammonia salt is used in the manufacturing process, the hydrothermal synthesis process can be performed under unsealed conditions, and ammonia is not diffused, ensuring work safety and reducing the impact on the surrounding environment. it can.

The present invention newly provides a method for extracting and utilizing phosphorus contained in sewage sludge incineration ash. In the present invention, sewage sludge incineration ash is used as a phosphoric acid source when synthesizing hydroxyapatite. The sewage sludge incineration ash contains phosphorus at a high concentration, and the content thereof is said to be about 10 to 30% by weight in terms of oxide P ₂ O ₅ .

  As a technique for extracting phosphoric acid from incinerated ash, an extraction method using acid or alkali has been attempted so far. Regarding the method using acid, it has been pointed out that toxic substances such as heavy metals are also eluted at the same time. On the other hand, the phosphorus extraction method using an alkali has an advantage that the amount of elution of heavy metals is smaller than that of acid extraction. However, in any method, since the extract contains a large amount of aluminum ions together with phosphoric acid, the product from the extract becomes aluminum phosphate as it is, and industrial reuse is difficult.

  In the present invention, an alkaline eluate of sewage sludge incineration ash, which is conventionally difficult to be reused in the industry, is utilized as an apatite crystal production raw material, thereby reducing the manufacturing cost. Further, if gypsum waste is used as gypsum, the profitability of the production business can be further improved by transferring the disposal acceptance costs for both gypsum waste disposal and sewage sludge incineration ash disposal to production costs.

  In the present invention, an alkaline solution is added to the sewage sludge incineration ash and stirred to extract phosphoric acid with the alkaline solution. Stirring is usually performed for at least 1 hour, preferably 3 to 12 hours. After stirring, solid-liquid separation can be performed to obtain an alkaline solution containing phosphoric acid. Examples of the alkaline solution include alkaline hydroxide solutions such as potassium hydroxide, sodium hydroxide, and magnesium hydroxide.

  It is not impossible to extract phosphorus by using sodium hydroxide instead of potassium hydroxide. However, the ionic radius of potassium ion (0.133 nm) is larger than the ionic radius of calcium (0.099 nm), whereas the ionic radius of sodium (0.095 nm) is smaller than this, so sodium ions are easily It has the property of entering into the crystal lattice in the hydroxyapatite in a form dissolved in the hydroxyapatite synthesis process. For this reason, when the sodium ion in the liquid phase increases, the purity of the hydroxyapatite crystal decreases and the crystallization rate also decreases. Therefore, it is desirable to use potassium hydroxide for the alkali extraction in the present invention.

The alkaline solution is usually 0.1 to 3.0 mol / l, but preferably has a high concentration. For example, if it is a potassium hydroxide solution, 0.5-3.0 mol / l is preferable, More preferably, it is 1.0-2.0 mol / l. If the concentration is low, the amount of phosphoric acid that can be extracted decreases, which is not preferable. If the concentration is increased, the amount of phosphoric acid extracted will increase, but if it exceeds 1 mol / l, there will be no significant difference. Therefore, it may be appropriately selected based on the balance between the amount of the chemical input and the amount of phosphoric acid extracted. However, if the concentration is too high, alkanite (K ₂ SO ₄ ) is produced during the reaction with gypsum, which is not preferable. It is preferable that phosphoric acid is extracted under such conditions, and the pH at the time of extraction is about 12 to 14. In the case of a phosphoric acid extract (aluminum concentration of 0.5 mol / l or less) using general sewage sludge incineration ash, the reaction is started by setting the concentration of the potassium hydroxide solution to 1.5 mol / l or more. The pH at the time can be 13 or more, and can be 12 or more at the end of the reaction. Therefore, in this case, aluminum hydroxide does not precipitate without additional addition of potassium hydroxide described later. However, when the aluminum concentration of the phosphoric acid extract is about 0.7 mol / l or more, aluminum hydroxide may be precipitated even at pH 12. In such a case, the addition of potassium hydroxide, which will be described later, can be performed to reliably prevent the precipitation of aluminum hydroxide and increase the purity of the produced hydroxyapatite crystals.

  Further, the ratio of the alkaline solution to the sewage sludge incinerated ash in the extraction is preferably 2 to 10 (liter / kg) in terms of solid-liquid ratio (L / S). Phosphoric acid can be satisfactorily extracted within the range of the solid-liquid ratio, but the phosphoric acid can be extracted even when the range is exceeded, and is not limited to this range.

  The concentration of phosphoric acid in the solution thus obtained is measured, and gypsum is added to this solution so that the Ca / P molar ratio is preferably 10/6 (hydroxyapatite stoichiometric ratio). . Even if this molar ratio is not 10/6, it is sufficient if it is an excess condition of phosphoric acid from the viewpoint of leaving no unreacted gypsum, and if it is shown in the range, it may be in the range of about 10/6 to 10/10.

  In the present invention, as the gypsum, waste gypsum such as gypsum board waste and desulfurized gypsum can be used. From the viewpoint of recycling and cost, any gypsum such as ordinary commercial gypsum powder can be used.

After adding the gypsum, the hydrothermal reaction is carried out at 40 to 100 ° C., preferably 45 to 95 ° C., more preferably 70 to 95 ° C., for 6 to 48 hours, preferably 12 to 24 hours. Hydroxyapatite crystals are produced even when the hydrothermal reaction time is set to 1 hour. However, in order to substantially complete the production of hydroxyapatite, it is preferable to carry out the hydrothermal reaction for 6 hours or more, and sufficient production of hydroxyapatite is sufficient. In order to complete the process, it is preferable to conduct a hydrothermal reaction for 12 to 24 hours. Here, in general, the reaction rate is higher at a higher temperature, and even if the temperature exceeds 100 ° C., the synthesis is possible if the reaction is carried out using a pressure vessel. Therefore, the synthesis is performed at a temperature exceeding 100 ° C. There is no denying what to do. In addition, the synthesis is possible even under atmospheric pressure conditions where the solution is boiled (around 100 ° C.), but in this case, it is necessary to replenish water lost due to boiling. In addition, the reaction of gypsum and phosphoric acid must be such that the pH of the solution at the start of the reaction is 13 to 14.9, preferably pH 13 to 13.5 and the pH at the end of the reaction is 12 or more. Generally, the aluminum concentration of the sewage sludge incinerated ash eluate is considered to be about 10 g / L at the maximum. If the pH at the start of the hydrothermal reaction is less than 13, the pH decreases after the hydrothermal reaction and cannot be maintained at 12 or more. , Aluminum hydroxide (Al (OH) ₃ ) may be precipitated. On the other hand, when the pH exceeds 14.0, the potassium concentration in the liquid phase is high, so that the purity of the product is lowered and alkanite (K ₂ SO ₄ ) may be generated. When the pH is 13 to 14.0, preferably 13 to 13.5, a hydroxyapatite containing almost no aluminum hydroxide or alkanite (K ₂ SO ₄ ) can be obtained. If the pH value is maintained as described above, the composition of the solution is still unsaturated (dissolved) with respect to aluminum hydroxide (Al (OH) ₃ ), and this operation prevents the precipitation of aluminum hydroxide. Only the produced hydroxyapatite component can be solid-liquid separated.

  As described above, since the sulfuric acid is separated and produced in the reaction process, the pH is lowered. Therefore, in order to keep the pH in the range of 12 until the end of the reaction during the reaction, the pH of the solution needs to be higher than 13 at the start of the reaction. If the pH of the alkaline solution at the time of alkali extraction is high and the pH can be maintained at 12 or more at the end of the reaction even if the pH is lowered by the reaction, gypsum can be added and the hydrothermal reaction can be performed. However, when the initial pH of the extraction solution is low, such as when extracted with a potassium hydroxide solution having a concentration in the range of 0.1 to 1 mol / L, for example, an alkali in an amount exceeding the amount of sulfate ion to be separated Is again added to the liquid to further increase the pH of the liquid phase, and then a hydrothermal reaction is performed. After the hydrothermal reaction, the pH drops, but since alkali is added again, the reaction solution is kept at a higher value than the pH when the sewage sludge incineration ash is alkali extracted, and the aluminum hydroxide during the hydrothermal reaction It is possible to keep the degree of saturation always lower than the alkaline solution at the time of alkaline extraction. In this case, the added molar amount of alkali is 0.2 times or more of the gypsum charged molar amount, and preferably about 0.3 to 1 times.

  Moreover, even when the initial pH of the extraction solution is not low as described above, the alkali may be added again into the liquid. When an amphoteric metal ion such as Fe or Zn is contained in a large amount in an alkaline solution, these precipitates are formed due to a decrease in pH accompanying a hydrothermal reaction. Also in this case, it is possible to suppress the mixing of these hydroxides into the product by re-adding the alkali.

  Furthermore, when the aluminum concentration in the phosphoric acid solution is unknown, it is possible to easily and reliably maintain the pH within the range where the above aluminum hydroxide does not precipitate by adding alkali to the solution again. There are also merits that are not necessary, and this is the preferred method.

  FIG. 1 shows an example of a method for producing an adsorbent mainly composed of a hydroxyapatite crystal of the present invention.

  The chemical formula of the reaction is as follows if the alkaline extract composition is represented in the form of phosphate.

10CaSO ₄ : 2H ₂ O + 6K ₃ PO ₄ → Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ + 9K ₂ SO ₄ + H ₂ SO ₄

  In the method of the present invention, the pH during the reaction is about pH 12 to 14.9, and the fact that a hydroxyapatite crystal can actually be produced by such a hydrothermal reaction under extremely high alkaline conditions. There are no reports in the past, and it is an unknown fact.

  Since the hydroxyapatite thus obtained is produced under high alkaline conditions, it is alkaline when in contact with water, unlike general hydroxyapatite. General hydroxyapatite is a neutral substance and easily decomposes in an environment of pH 5.5 or lower. However, the hydroxyapatite obtained by the method of the present invention is not easily decomposed even in an acidic atmosphere. It is thought that the effect can be sustained. Therefore, it can exist more stably even if it is added to acidic soil where heavy metal elution tends to become obvious.

Further, the hydroxyapatite obtained by the method of the present invention contains 4.7 to 5.0% by weight of silica (SiO ₂ ) as a composition from the analysis results, and the product of the present invention is a silica-containing hydroxy acid. It is apatite.

  After the hydrothermal reaction, the alkali solution (residual liquid) obtained by filtering and separating the hydroxyapatite can be repeatedly used for alkali extraction for cost reduction. When a potassium hydroxide solution is used as the alkaline solution, about 60% by volume of the liquid volume at the time of phosphoric acid extraction finally becomes a residual liquid, and this portion can be reused for alkaline extraction. The liquid loss at this time is mainly the amount of water remaining in the sewage sludge incineration ash separated after the phosphoric acid extraction. Also, the aluminum concentration in the liquid phase is limited by the solubility of amorphous aluminum hydroxide. Therefore, by using the residual liquid for phosphorus extraction from sewage sludge incineration ash, the amount of new aluminum leaching from the sewage sludge incineration ash can be reduced, and the amount of final waste liquid that needs to be processed can be reduced. It is possible to reduce the amount of potassium alum generated as a sediment. Furthermore, since a short amount of potassium hydroxide solution can be added to the residual liquid and used, the amount of potassium hydroxide used in the sewage sludge incineration ash elution process can also be reduced.

Even after the hydrothermal reaction, even if the residual liquid is repeatedly used for alkali extraction, it is necessary to finally separate dissolved components. Usually, aluminum ions become zero-valent aluminum hydroxide by neutralizing the pH and precipitate, but this precipitate has a large water content and is not easy to dehydrate and separate. In the present invention, utilizing the fact that the solution after the hydrothermal reaction is still at a high temperature, the adsorbent is separated into solid and liquid while the solution is at a high temperature after the reaction is completed, and sulfuric acid is added to the obtained waste liquid with the high temperature. Then, after neutralizing to pH 3 or lower, potassium alum (AlK (SO ₄ ) ₂ ) is allowed to settle in the cooling process. Potash alum is highly temperature-dependent and dissolves at 710 g / L at 80 ° C., whereas only 59 g / L can be dissolved at 20 ° C. (FIG. 2). For this reason, as the temperature decreases, it is possible to precipitate potassium alum efficiently from the liquid phase, thereby facilitating waste liquid treatment. Combining this process has the advantage that no new heating energy is required because the energy during the hydrothermal reaction of apatite generation is used as it is.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above embodiment, phosphorus is extracted from sewage sludge incineration ash, but is not limited to this as long as it is a raw material derived from sewage sludge containing phosphorus. For example, dried and solidified sewage sludge Or it is also possible to perform phosphorus extraction using carbonization treatment, for example, sewage sludge heat-treated in a low oxygen atmosphere.

  In addition, bio-power generation systems that use sewage sludge dried, solidified, or carbonized, mixed with coal, and burned to generate electricity have a high phosphorus content in the fuel, resulting in co-firing with coal. The phosphorus content in the coal ash that increases is also increased. The current main recycling application of coal ash is as a raw material for cement, but as the phosphorus content in coal ash increases, the hardening performance of cement using coal ash decreases. For this reason, when considering the recycling of coal ash, it is difficult to greatly increase the amount of sewage sludge processing fuel input at the time of co-firing, but if the concentration of phosphorus in the sewage sludge can be reduced, the biomass processed from this sewage sludge The concentration of phosphorus in the fuel can also be reduced, which is advantageous in terms of recycling coal ash. Therefore, by using sewage sludge with a reduced phosphorus concentration using the method of the present invention in advance, an increase in the phosphorus concentration of coal ash can be suppressed as a result, and the quality of the cement material, which is its maximum application, is reduced ( There is an advantage that a decrease in curing performance due to an increase in phosphorus concentration can be suppressed. Also, since desulfurized gypsum is discharged at many thermal power plants, phosphorus is extracted from sewage sludge in the vicinity of the power plant, and a hydroxyapatite adsorbent is produced from the phosphorus and desulfurized gypsum. Is considered to be able to significantly reduce the cost of transporting gypsum and sewage sludge after phosphorus extraction. Therefore, according to the present invention, an apatite adsorbent can be obtained at a very low cost, and the phosphorus content of coal ash after use of the carbonized fuel can be reduced by reducing the phosphorus content of the carbonized fuel. An economically very advantageous system (FIG. 15) can be provided in which a high-quality cement material can be provided.

  In FIG. 15, apatite is synthesized from sewage sludge. Hydroxyapatite is mainly composed of this material using dry, solidified or carbonized material of sewage sludge and desulfurized gypsum from a coal-fired power plant. Can also reduce the phosphorus content of the raw material obtained by drying, solidifying, or carbonizing sewage sludge, thereby solving the problem related to the increase in the phosphorus concentration of coal ash. Demonstrate.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

The gypsum board waste used as a raw material was waste gypsum after paper separation processing generated from a domestic intermediate processing company. The X-ray diffraction result of the gypsum waste is shown in FIG. Most of the gypsum waste is dihydrate gypsum, but a trace amount of anhydrous gypsum and hemihydrate gypsum was included. Table 1 shows the results of XRF (fluorescence X-ray) analysis. In addition to the main component of gypsum, it contained 10% by weight of SiO ₂ and 2.8% by weight of Al ₂ O ₃ . In this example, for the X-ray diffraction measurement, Philips PW3020 (tube Cu, output 40 kV, 50 mA, wavelength CuKα, 1.54056 mm, diffraction angle 2θ = 2 ° -60 °, scan speed 1 ° / min. The XRF measurement was performed using Shimadzu Corporation XRF1500, and all the gypsum samples were quantified by the powder press method.

On the other hand, sewage sludge incineration ash was generated from domestic sewage treatment plants. Table 2 shows the XRF analysis results of the sewage sludge incineration ash. Main component of sewage sludge incineration ash _SiO 2 30 _wt%, Al _{2 O} 3 15 _wt%, P 2 _{O 5} is 28% by weight, CaO were contained 10% by weight.

  Next, 0.5 mol / L, 1 mol / L, 2 mol / L of potassium hydroxide solution is mixed with sewage sludge incineration ash at a solid-liquid ratio (L / S) of 5 (liter / kg), respectively. The elution operation was performed at 200 rpm with a shaker at room temperature for 6 hours. After shaking, the solution obtained by filtration and separation was analyzed by ICP. The cation component was analyzed by Shimadzu Corporation ICPS-8100, and the anion component was analyzed by Tosoh Corporation IC-2001 (anion component). The results are shown in Table 3. A large amount of phosphoric acid and aluminum are eluted from the solution, and there is a large difference in the concentration of phosphoric acid between 0.5 mol / L and 1 mol / L, but the phosphoric acid eluted at 1 mol / L and 2 mol / L. Since there is not much difference in concentration, from this result, it is judged that 1 mol / L is appropriate for the potassium hydroxide concentration when considering the balance between the amount of the drug input and the amount of phosphoric acid extracted.

  The amount of gypsum to be added is 1.67 times the amount of phosphoric acid in the liquid phase, and 0.5 mol of potassium hydroxide is further added to 1 L of the above extraction solution to prevent precipitation of aluminum hydroxide. It was. Regarding the amount of potassium hydroxide re-introduced, from the chemical formula, it is possible to prevent a decrease in pH by adding 0.2 times the number of moles of gypsum added, but once during the hydrothermal reaction, aluminum hydroxide Therefore, it is necessary to keep the water composition sufficiently unsaturated with respect to aluminum. Taking the above solution extracted at a concentration of 1 mol / L as an example, the amount of potassium hydroxide required to maintain a pH at which no aluminum hydroxide precipitate is generated is about 0.1 mol at maximum with respect to 1 L of this solution. However, considering the influence of other coexisting components, it is desirable that the addition amount is considerably larger than the theoretical amount, so that 0.5 mol of potassium hydroxide corresponding to about 5 times the theoretical amount per 1 liter. The amount added was set.

  Regarding the addition of potassium hydroxide at this point, based on the chemical composition analysis results of the dissolved components of the alkaline eluate, the pH after hydrothermal synthesis, the amount of hydroxyapatite (HAP) produced, and the amount of aluminum hydroxide precipitated are heated. Table 4 shows the results calculated by a geochemical model using dynamic equilibrium theory. About 0.5 mol / L concentration eluate and 1.0 mol / L eluate, when potassium hydroxide is not added, the pH after hydrothermal synthesis is remarkably lowered and aluminum hydroxide is remarkably precipitated. It became the calculation result. On the other hand, when potassium hydroxide was added, it was confirmed by calculation that aluminum hydroxide did not settle and only the hydroxyapatite component could be selectively produced.

  From this calculation result, 0.5 mol / L of gypsum (corresponding to a 10/6 molar ratio of phosphoric acid) and KOH were added to each solution, shaken at a temperature of 120 ° C. for 24 hours at a temperature of 80 ° C., and then filtered. Solid-liquid separation was performed, and the obtained solid phase was washed with pure water. In addition, the pH value (actual measurement) at the start of the hydrothermal reaction of these samples was about 13.9 to 14.9, and the pH value at the end was about 12.9 to 13.8.

The X-ray diffraction waveform of this solid phase is shown in FIG. In the figure, the black circle is a peak of hydroxyapatite, and it was confirmed that the synthesized product was mainly composed of hydroxyapatite crystals in all three obtained samples. In addition, with respect to the synthesized product from the 2 mol / L alkaline eluate, a peak of alkanite (K ₂ SO ₄ ) was also confirmed, and under conditions of 2 mol / L, the alkanite was mixed in the solid phase. It has been found. In addition, these waveforms did not confirm the peak of gypsum, and it was clarified that calcium in the gypsum completely changed into a hydroxyapatite crystal. Moreover, the peak of gibbsite (Al (OH) ₃ ) was not confirmed in the waveform.

Table 5 shows the XRF analysis results of the obtained solid phase. In addition, XRF analysis of the obtained solid phase was performed by a glass bead quantitative analysis method. It was confirmed that all the synthesized products were mainly composed of calcium and phosphorus. The product of the present invention contains potassium and aluminum as impurities. As for aluminum, the amount contained in the composite is the same as or slightly less than the total amount of aluminum contained in the gypsum waste used as a raw material. By adding, it is shown that aluminum ions contained in a high concentration in the sludge incineration ash extract can be prevented from precipitating in the solid phase. From the analysis results, the composition contained 4.7 to 5.0% by weight of silica (SiO ₂ ), and it was found that the product of the present invention was silica-containing hydroxyapatite. This silica is thought to be the component that was contained in the waste gypsum raw material remained in the crystal during the hydrothermal synthesis process.

From this table, the purity of hydroxyapatite is highest under the condition of 0.5 mol / L. However, the potassium hydroxide concentration of 1 mol / L is the most suitable for practical use, taking into account the production efficiency of the synthetic product derived from the extraction efficiency of phosphorus. Can be judged.

Next, FIG. 8 shows the result of investigating the synthesized product by XRF analysis regarding the effect of adding potassium hydroxide after adding gypsum to the extract. In addition, the measurement result of FIG. 8 is a result of having implemented the waste gypsum sample different from the case of Table 5 as a raw material. In FIG. 8, (a) is a compound synthesized using 0.5 mol / L extract without additional potassium hydroxide, and (b) is potassium hydroxide using 0.5 mol / L extract. A compound synthesized by additional addition, (c) using 1.0 mol / L extract and adding no potassium hydroxide, (d) using 1.0 mol / L extract The results of the synthesized product with additional potassium hydroxide added are shown. The amount of potassium hydroxide added was 0.5 mol per liter. By additionally adding potassium hydroxide, the total content of CaO and P ₂ O _{5 in} the composition is reduced from 54 wt% to 71 wt% when using an extract under the condition of KOH-0.5 mol / L. When the KOH-1.0 mol / L extract was used, the content increased from 47% by weight to 64% by weight, confirming that the hydroxyapatite content in the composite was increased. In addition, by adding potassium hydroxide, the content of potassium in the composition was lowered, and the extract of aluminum (Al ₂ O ₃ ) was used under the condition of KOH-0.5 mol / L. It was confirmed that 9.9% by weight of the sample was reduced to 2.8% by weight, and that of the sample using the KOH-1.0 mol / L conditioned extract was reduced from 11.5% by weight to 5.9% by weight. Therefore, it was found that it is better to add potassium hydroxide in order to produce hydroxyapatite with high purity and high yield.

  Further, FIG. 9 shows the results of investigation on the time required for synthesizing the hydroxyapatite crystal and the optimum temperature condition. The X-ray diffraction maximum peak height (count number) on the vertical axis is the maximum peak value of the hydroxyapatite crystal when the obtained hydroxyapatite crystal is measured by X-ray diffraction. This is an index value. Also, ● represents the result when the synthesis temperature is 40 ° C., and ○ represents the result when the synthesis temperature is 95 ° C. Hydroxyapatite crystals begin to form within about 1 hour after the start of synthesis under both temperature conditions, and up to 6 hours after the start of synthesis, an increase in the maximum peak height of X-ray diffraction is observed under both temperature conditions. Under the conditions, the peak height was almost constant, and at 95 ° C., the peak height tended to increase slightly. Accordingly, a hydroxyapatite crystal can be obtained in a synthesis time of about 1 hour, but it takes about 6 hours to complete the synthesis, and a synthesis time of about 12 to 24 hours to fully complete the synthesis. It turned out to be preferable. Further, it is found that a hydroxyapatite crystal can be sufficiently obtained if the synthesis temperature is set to 40 ° C. to 95 ° C., but it is preferable that the synthesis temperature is close to 95 ° C. in order to obtain more hydroxyapatite crystals. did.

[Adsorption performance test]
Next, in order to compare and confirm the adsorption performance of this composite, an adsorption performance test was conducted on lead, cadmium and fluorine.

  Samples to be compared were hydroxyapatite high purity reagent (manufactured by Wako Pure Chemical Industries), commercially available bone charcoal powder with similar components, diammonium hydrogen phosphate and gypsum board waste (the same product used in the present invention product) Hydroxyapatite (synthetic product by a conventional method) produced by hydrothermal reaction of) and 3 samples (inventive product) synthesized by the method of the present invention as described above.

  Add an adsorbate sample at a rate of 1 g / L to lead (lead nitrate salt solution) and cadmium (cadmium nitrate salt) solution, and add 2 g / L to fluorine (sodium fluoride salt) solution. did. The initial concentration of the solution was adjusted to 50 ppm for lead and cadmium and 20 ppm for fluorine, adjusted to an initial pH of 5.8 to 6.3, shaken at a shaking speed of 120 rpm for 6 hours at room temperature, and the filtrate after shaking. Was analyzed. The analysis was conducted by ICP (Shimadzu ICP-8100) for lead and cadmium concentrations, and ion chromatograph (Tosoh IC-2001) for fluorine concentrations.

The results are shown in FIGS. Regarding lead, when adsorbed with hydroxyapatite high purity reagent or bone charcoal, 5 to 15 ppm or more remains, while the adsorbate synthesized by the method of the present invention has a residual amount of 0.07 to 0. The sample synthesized by the method of the present invention showed better adsorptivity than other samples. Also, the adsorption performance of the product of the present invention was superior to cadmium as compared with high purity reagents, bone charcoal, and conventional methods. According to the literature (1992, Gypsum & Lime, 236, 3-11), “silica-containing hydroxyapatite removes a large amount of various cations than hydroxyapatite”, “especially Mn ²⁺ , Zn ²⁺ , Cd It has been confirmed that it has excellent adsorption properties for adsorbing more ^{2+, and} that the product of the present invention is silica-containing hydroxyapatite, the cation adsorption property of the product of the present invention is higher than that of a high purity reagent / bone charcoal It is estimated that it is the main factor that excels. In addition, the product of the present invention also exhibited substantially the same adsorptivity to fluorine as the hydroxyapatite obtained by the conventional method.

  In addition, when the pH of the liquid phase at the end of shaking in the cadmium adsorption test was measured, the other samples were neutral at 5.9 to 6.7, but were synthesized by the method of the present invention. The pH value of the sample was weakly alkaline at 7.8 to 8.2. In addition, the product of the present invention (1 mol / L synthesis condition) in an amount equivalent to a solid-liquid ratio of 10 (L / kg) in pure water and shaken for 6 hours has an equilibrium pH value of 10.2 and is alkaline. Indicated. The fact that the product of the present invention exhibits alkalinity is a preferable property for suppressing elution of heavy metals whose solubility generally decreases in the alkaline region.

  Next, isothermal adsorption lines were created from the amount of fluorine adsorption at various fluorine concentrations of the inventive product and the comparative product (reagent hydroxide apatite, bone charcoal), and the fluorine adsorption performance of the inventive product and the comparative product was examined. The isothermal adsorption line was obtained as follows. 2g / L of adsorbent was added and the initial concentration of fluoride ion was 1mg / L, 5mg / L, 20mg / L, 125mg / L, and a batch test was performed at room temperature for 6 hours at a shaking speed of 120rpm. The concentration of the liquid phase was measured with an ion chromatograph (Tosoh IC-2001), and this concentration was taken as the equilibrium concentration. The amount of adsorption was determined from the difference between the concentration value in the liquid phase of the control test without adsorbent and the concentration value of the test with adsorbent, and this was plotted as the amount of adsorption per adsorbent input (g). The results are shown in FIG. In FIG. 10, ● represents a reagent hydroxyapatite (hydroxyapatite high purity reagent (manufactured by Wako Pure Chemical Industries)), ○ represents bone charcoal, ▲ represents an invention product synthesized by the method of the present invention using a gypsum board, and Δ represents desulfurized gypsum. The result of the invention product synthesized by the method of the present invention using is shown. It was confirmed that the adsorption performance of the product of the invention was very high compared to the reagent hydroxyapatite. Further, when the invention product and bone charcoal are compared, there is not much difference in the adsorption amount in the concentration range of 0.1 to 1 mg / L of fluorine concentration, but the adsorption performance superior to that of the comparative product in the concentration range of 1 mg / L or more. In particular, in the range of 10 to 100 mg / L, it was revealed that the adsorption performance is very excellent as compared with bone charcoal.

Next, a long-term column adsorption test was conducted on the adsorption ability when the invention product was added to the soil. The results are shown in FIG. The column had a size of an outer diameter of 18 mm and a length of 30.5 cm, and the packing used for the column was Toyoura standard sand added with the invention or comparative product in a ratio of 100: 8 to sand (70 g). . An aqueous solution containing 2 mg / L of fluorine ions was circulated from the column inlet, and the concentration of waste water after passing through the column was measured periodically. The space velocity (unit time passage flow rate / column packing volume), which is an index of flow velocity, is 0.089 hr ⁻¹ (= 2) in order to simulate the infiltration phenomenon of groundwater, that is, the adsorption phenomenon under a very slow condition of water flow. 0.1 day ^-1 ). In the figure, the horizontal axis represents the cumulative amount of treated water (L) per gram of the invention or comparative product input. In the figure, groundwater environmental standard value 0.8 mg / L, which is the purification target value of groundwater related to fluorine, is described. As comparative products, bone charcoal (●), synthesized by the method of the present invention using desulfurized gypsum (◯), and synthesized by the method of the present invention using gypsum board (△) are used. It was. From this test result, comparing the cumulative amount of treated water until the waste water from the column reaches 0.8 mg / L, the inventive product has more cumulative treated water than bone charcoal, and the inventive product synthesized from desulfurized gypsum is one of bone charcoal. It was confirmed that the invention synthesized from gypsum board, which is twice (1.5 L / g), can treat 1.6 times (1.9 L / g) water of bone charcoal. Therefore, it has been shown that the invention is extremely effective as a soil purification material contaminated with fluorine and a chemical barrier material in a waste disposal site containing a substance containing a large amount of fluorine.

  Finally, the concentration of fluorine, boron, cadmium, selenium, hexavalent chromium, arsenic and lead eluted from the invention was confirmed by an elution test according to the Environmental Agency Notification No. 46 method. The results are shown in Table 6. The elution concentration of any element was below the soil environmental standard value, confirming the environmental safety of the product of the present invention. Moreover, the pH of water at the time of equilibrium is about 10, and this test result also showed that the product of the present invention exhibits alkalinity.

  From the above results, it was shown that the apatite produced this time is silica-containing hydroxyapatite, and has the same or better adsorption ability as the existing product as an environmental purification material, and also has an alkaline property.

[Reuse of residual liquid]
An investigation was made as to whether or not a liquid obtained by solid-liquid separation after synthesis of hydroxyapatite (hereinafter referred to as residual liquid) can be reused. The residual liquid was obtained by synthesizing hydroxyapatite using a phosphoric acid extract obtained by using a 1.0 mol / L potassium hydroxide solution in sewage sludge incineration ash, followed by solid-liquid separation. Liquid was used. 40% by volume of a 1.0 mol / L potassium hydroxide solution is mixed with 60% by volume of the remaining liquid, and sewage sludge incineration ash is put therein at a solid-liquid ratio of 1: 5. The elution operation was carried out with shaking. An additional 0.5 mol of potassium hydroxide per liter was added to the solution after extraction, 88 g / L of gypsum was placed therein, and the mixture was reacted at a temperature of 80 ° C. for 24 hours. After completion of the reaction operation, solid-liquid separation was performed to obtain a residual liquid (second time). Furthermore, this residual liquid (2nd time) was used for extraction of phosphoric acid from sewage sludge incineration ash by the same operation as described above.

  The amount of potassium hydroxide used when reusing the residual liquid is 1.5 mol / L in total when the residual liquid is not used, but 0.9 mol / L when the residual liquid is used. The amount of potassium oxide used can be substantially reduced by 40%. In addition, from the measurement results at the time of the experimental operation, about 60% by volume of the liquid volume at the time of phosphoric acid extraction finally becomes the residual liquid, and the liquid volume loss at this time is mainly in the sewage sludge incineration ash. The amount of water remaining. For this reason, mixing at a ratio of 60% by volume of the remaining liquid at the time of recycling means that most of the actually generated residual liquid is reused.

  FIG. 12 shows (a) when extracting phosphoric acid for the first time (using no residual liquid), (b) when extracting phosphoric acid using the residual liquid once used, and (c) when extracting phosphoric acid using the residual liquid used twice. The concentration of aluminum newly eluted from each sewage sludge incineration ash is shown. From this figure, it became clear that the aluminum elution amount from the sewage sludge incineration ash can be reduced by adopting the phosphoric acid extraction process using the residual liquid.

FIG. 13 shows the XRD measurement results of the sample synthesized from the eluate using the used residual liquid. (A) is a measurement result of a synthetic sample using a potassium hydroxide eluate, and (b) is a measurement result of a synthetic sample using a residual liquid (60% by volume) utilization eluate. Since the eluate using the used residual liquid contains a high concentration of sulfate ions, the XRD waveform has a shigenite (KCa (SO ₄ ) ₂ : H ₂ O) peak, and the mineral is present in the product. It was confirmed that some amount was contained. On the other hand, the peak of the gypsum component of dihydrate gypsum and hemihydrate gypsum completely disappeared, and it was confirmed that the gypsum crystals were completely decomposed during the synthesis process. In addition, the waveform shape and peak height of the hydroxyapatite peak are almost the same as the waveform of the sample synthesized without using the residual liquid. Was shown to have no effect.

[Comparison of phosphorus extraction rate when using sewage sludge incineration ash and dry sewage sludge]
FIG. 14 shows the measurement results (XRF analysis results) of the change in phosphorus content in the solid phase by the extraction operation of phosphorus using a potassium hydroxide solution for the sewage sludge incineration ash and the dried sewage sludge. (A) is sewage sludge incineration ash (before treatment), (b) is sewage sludge incineration ash (0.5 mol / L potassium hydroxide treatment), and (c) is sewage sludge incineration ash (1 mol / L potassium hydroxide treatment). (D) is sewage sludge incineration ash (2 mol / L potassium hydroxide treatment), (e) is dry sewage sludge (before treatment), (f) dry sewage sludge (extraction under pH 12 conditions (0.5 to 1 mol / L). Equivalent to L potassium hydroxide treatment))). The dried sewage sludge was obtained by further drying (air-drying) the dehydrated cake. It was confirmed that the phosphorus content in the sewage sludge incineration ash and dry sewage sludge decreased by the extraction operation of phosphorus with potassium hydroxide solution. The phosphorus extraction rate (elution amount / content before treatment) is 12 to 36% for sewage sludge incineration ash and 34% for dry sewage sludge. It was revealed that phosphorus can be extracted with From the above results, it is possible to produce an adsorbent mainly composed of hydroxyapatite crystals using dry sewage sludge (usually in the form of a dehydrated cake) as a raw material in the same process as when using sewage sludge incineration ash as a raw material. I found it possible. In addition, the quantity of the alkaline solution to be used can be reduced by drying sewage sludge as much as possible. In addition, the volume of the alkaline solution can be reduced by further reducing the volume by carbonization.

  According to the present invention, effective utilization of gypsum board waste, sewage sludge incineration ash, or sewage sludge can be promoted, and an adsorbent mainly composed of hydroxyapatite can be provided at a low cost. The adsorbent of the present invention is useful as an environmental purification material. In addition, with the enforcement of the Soil Contamination Countermeasures Law, the need for materials that stabilize heavy metals contained in contaminated soil has increased, so the adsorbent according to the present invention can be used for such soil contamination countermeasures. .

It is process drawing which shows an example of the manufacturing method of the adsorbent of this invention. It is a solubility curve of potash alum. It is a result of the X-ray diffraction of the gypsum board waste used in the Example. It is a result of the X-ray diffraction of the adsorbent obtained in the Example. It is a graph which shows the lead concentration which remain | survives when using each adsorbent in the test of an Example. It is a graph which shows the cadmium density | concentration which remain | survives when using each adsorbent in the test of an Example. It is a graph which shows the fluorine density | concentration which remain | survives when using each adsorbent in the test of an Example. It is a figure which shows the XRF measurement result of the sample which added potassium hydroxide, and the sample which did not add additionally. It is a figure which shows the relationship between hydrothermal reaction time and the amount of hydroxyapatite crystal production. It is a figure which shows the isothermal adsorption line of the fluorine at the time of using each adsorbent in the test of an Example. It is a figure which shows the long-term column adsorption test result of the fluorine in the test of an Example. It is a figure which shows the aluminum concentration newly eluted from the sewage sludge incineration ash in the solution after the phosphoric acid extraction operation using a used residual liquid. It is a figure which shows the result of having performed the XRD measurement of the sample synthesize | combined with the phosphoric acid eluate using a used residual liquid. It is a figure which shows the change of phosphorus content of the sewage sludge incineration ash before and behind alkali treatment, and dry sewage sludge. It is a figure which shows a phosphorus recovery type sewage sludge carbonization fuel system.

Claims (9)

  After stirring the sewage sludge incinerated ash in an alkaline solution, gypsum is added to the solution obtained by filtration and separation, and the pH at the start of the reaction is adjusted to 13.0 to 14.9 and stirred at 40 to 100 ° C. And the pH at the time of completion | finish of reaction is hold | maintained to 12 or more, The phosphoric acid in the said alkaline solution and the said gypsum are made to react, The manufacturing method of the adsorbent which has a hydroxyapatite crystal as a main component is characterized by the above-mentioned.   The dried and solidified sewage sludge or carbonized sewage sludge is stirred in an alkaline solution, and gypsum is added to the solution obtained by filtration and separation, and the pH at the start of the reaction is 13.0 to 14.9. And a hydroxyapatite crystal, which is stirred at 40 to 100 ° C. and maintains the pH at the end of the reaction at 12 or more to react phosphoric acid in the alkaline solution with the gypsum. The manufacturing method of adsorbent.   The method for producing an adsorbent comprising a hydroxyapatite crystal as a main component according to claim 1 or 2, wherein the gypsum is waste gypsum.   The alkaline solution is a potassium hydroxide solution having a concentration in the range of 1.5 to 3.0 mol / L, and is an alkaline solution for the sewage sludge incineration ash, the dried / solidified sewage sludge, or the carbonized sewage sludge. The ratio is 2 to 10 (liter / kg) in terms of solid-liquid ratio (L / S), and the amount of the gypsum to be added is contained in a solution obtained by filtration separation from Ca contained in the gypsum. The method for producing an adsorbent comprising a hydroxyapatite crystal as a main component according to any one of claims 1 to 3, wherein the molar ratio of P is 10: 6.   The alkaline solution is a potassium hydroxide solution having a concentration in the range of 0.1 to 3.0 mol / L, and is an alkaline solution for the sewage sludge incineration ash, the dried / solidified sewage sludge, or the carbonized sewage sludge. The ratio is 2 to 10 (liter / kg) in the solid-liquid ratio (L / S), and the amount of the gypsum to be added is contained in the solution obtained by filtration separation from Ca contained in the gypsum. The molar ratio of P is 10: 6. When gypsum is charged, potassium hydroxide corresponding to 0.3 to 1 times the molar amount of gypsum is further added to adjust the pH at the start of the hydrothermal reaction. The manufacturing method of the adsorbent which has a hydroxyapatite crystal as described in any one of Claims 1-3 hold | maintained at 13-14.9.   After completion of the reaction, sulfuric acid is added to the high-temperature waste liquid obtained by solid-liquid separation of the adsorbent, and the pH is adjusted to 3 or less, and then cooled to precipitate potassium alum and separate the aluminum ion and sulfate ion in the waste liquid. The manufacturing method of the adsorbent which has a hydroxyapatite crystal | crystallization as described in any one of Claims 1-5 containing a process process as a main component.   The adsorbent comprising a hydroxyapatite crystal as a main component according to any one of claims 1 to 6, wherein the alkaline solution is a waste liquid obtained by solid-liquid separation of the adsorbent after completion of the reaction. Manufacturing method.   The adsorbent which has as a main component the hydroxyapatite crystal | crystallization which exhibits the alkalinity when it contacts with water obtained by the manufacturing method as described in any one of Claims 1-7. The adsorbent whose composition of the hydroxyapatite crystal | crystallization obtained by the manufacturing method as described in any one of Claims 1-7 is a silica containing hydroxyapatite.

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