TW201838929A - Water treatment method, magnesium agent for water treatment, and method for producing magnesium agent for water treatment - Google Patents

Abstract

An object of the invention is to provide a water treatment method which, from a water containing matter to be removed, can insolubilize the matter to be removed in a short time, perform a solid-liquid separation, obtain a treated water of favorable water quality, and efficiently reduce the volume of separated solids. The water treatment method entails adding, to a water to be treated containing matter to be removed, at least one material among a magnesium agent prepared by sintering basic magnesium carbonate at a temperature within a range from 500 to 700 DEG C, and a magnesium agent prepared by sintering magnesium hydroxide at a temperature within a range from 450 to 650 DEG C.

Description

Water treatment method, magnesium agent for water treatment, and manufacturing method of magnesium agent for water treatment

The present invention relates to a method for treating water containing boron and other substances to be removed using a magnesium compound, a magnesium agent for water treatment used in the water treatment, and a method for producing the magnesium agent for the water treatment.

Wastewater discharged by various industries containing boron, fluorine, selenium, silicon dioxide, heavy metals and other substances in high concentrations must be treated below the emission standards before being discharged. For example, power generation equipment that burns coal to generate electricity or the like is provided with desulfurization equipment for purifying exhaust gas, such as removing sulfur content in the exhaust gas with water in which alkali agent is dissolved, or coal dust that cannot be removed by a dust collector. The water that has absorbed the sulfur content or coal dust can be appropriately discharged as desulfurization drainage from the desulfurization equipment, treated to the discharge standard and then discharged to the ocean.

The desulfurization drainage usually contains boron, fluorine, selenium, heavy metals (iron, lead, copper, chromium, cadmium, mercury, zinc, arsenic, manganese, nickel, etc.) contained in coal and the like. Among them, boric acid (H ₃ BO ₃ ) or the like contains a high concentration of boron, and there are cases of about 200 to 500 mg-B / L.

For the water treatment of these substances, there are cases in which the following methods are used: magnesium salts which are inexpensive and almost harmless even if they remain in water are added to insolubilize these substances, and separate insoluble matters from solid-liquid separation. Separated by treated water. Magnesium salts are known to generally insolubilize these substances (see Patent Document 1, Patent Document 2, Non-Patent Document 1).

On the other hand, when the silica-containing water containing silica is to be recovered and reused, it is difficult to increase the content of the silica due to scale formation in a piping or a reverse osmosis membrane (RO) device at the subsequent stage. The recovery rate of silicon water may be difficult to run stably. Therefore, it is required to reduce the amount of silicon dioxide in water containing silicon dioxide. As a method for reducing the amount of silicon dioxide in water containing silicon dioxide, a method using a magnesium salt is being examined (see Non-Patent Document 2).

As described above, magnesium salts can remove various substances and ions in water and can be used as a water treatment agent. Magnesium salts become magnesium ions if dissolved in water. However, if the water is adjusted to a basic pH of about 10 or more, boron, fluorine, and the like are bonded to magnesium to form insoluble matter, or boron, fluorine, and the like are adsorbed on magnesium and hydroxide ions. Insolubilization is performed by bonding insoluble magnesium hydroxide. By separating these insolubles from solid and liquid, various substances such as boron and fluorine can be removed from water.

Since magnesium is a resource produced in large quantities and is inexpensive, the operating costs required for processing are also low. In addition, when the treated water is made neutral and released to the environment, almost harmless magnesium has an excellent feature that it has almost no problems even if it remains in the treated water.

Those who are magnesium salts and can be used as industrial water treatment agents include magnesium chloride hexahydrate (MgCl ₂ · 6H ₂ O), basic magnesium carbonate (3MgCO ₃ · Mg (OH) ₂ · H ₂ O), hydrogen Magnesium oxide (Mg (OH) ₂ ), magnesium oxide (MgO), and the like. Any magnesium salt can be used to insolubilize a substance to be removed in an alkaline solution having a pH of 10 or more in water.

These magnesium salts have excellent characteristics as described above, and relatively have the following problems. First, regarding magnesium chloride and hexahydrate, the magnesium content of the magnesium salt is about 12%, which is less than other magnesium salts, and a larger amount of addition is required. Moreover, since it does not contain a hydroxyl group, in order to make the to-be-processed water alkaline and insolubilize a substance to be removed, it is necessary to separately add an alkali agent such as sodium hydroxide.

Although basic magnesium carbonate and magnesium hydroxide have more magnesium content than magnesium chloride and hexahydrate and contain bases (hydroxyl groups) in the molecule, they are almost insoluble in neutral water. Therefore, it is necessary to add an acid to the treated water to make it acidic. Add it later, or add an acid to the magnesium salt itself to make an aqueous solution, and then add it to the treated water. If the water to be treated is acidic in advance, if it is neutral, it is necessary to add an acid and then add a magnesium salt, and then it is necessary to further add an alkali agent in order to make the pH of the water to be treated alkaline. In addition, after the acid is added, most of the magnesium becomes magnesium ions, and when the pH is 9.5 or higher with an alkali agent, most of the magnesium ions except those bound to the target substance become swollen magnesium hydroxide (Mg (OH) ₂ ) The slurry has the problems of poor precipitation separation and dehydration.

Magnesium oxide sintered basic magnesium carbonate and magnesium hydroxide at a high temperature of 500 ° C or higher. The magnesium content is large, and if dissolved in water, it becomes magnesium hydroxide, and the water is alkaline. In addition, the insoluble matter produced by making it alkaline is not only magnesium hydroxide, but it contains crystals of magnesium oxide or magnesium carbonate in a part, so it also has a higher concentration than that formed by using alkaline magnesium carbonate and magnesium hydroxide as water treatment agents. Magnesium hydroxide-based insoluble matter slurry has better precipitation separation and dehydration characteristics.

However, depending on the sintering conditions, there are some cases where magnesium oxide dissolves slowly in water, and the insolubilization reaction to remove the target substance takes a lot of time, and it takes time to process. If the process is to be performed in a short time, the target substance is removed The problem is that the treatment water cannot be sufficiently insolubilized and the quality of the treated water is poor. In order to improve the quality of the treated water, it is necessary to add a large amount of magnesium oxide. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3355281 [Patent Document 2] Japanese Patent No. 4558633 [Non-Patent Document]

[Non-Patent Document 1] Izawa Ayaka, Maeda Susei, Suqian Qing, Tochigi Keiko, "Examination of the Mechanism of Boron Removal in the Wastewater of the Magnesium Hydroxide Co-precipitation Process", Journal of MMIJ, Vol. 130, pp.155-161 (2014) [Non-Patent Document 2] Isabel Latour, Ruben Miranda, Angeles Blanco, "Silica removal with sparingly soluble magnesium compounds. Part I", Separation and Purification Technology, 138 (2014), pp.210-218

[Problems to be Solved by the Invention]

An object of the present invention is to provide a water treatment method, a magnesium agent for water treatment used in the water treatment, and a method for producing the magnesium agent for water treatment; the water treatment method can self-contain water for removing a target substance and remove the target The substance undergoes insolubilization and solid-liquid separation in a short time to obtain treated water with good water quality, which effectively reduces the volume of the separated solid. [Means to solve the problem]

The present invention is a water treatment method, in which a magnesium agent that sinters alkaline magnesium carbonate at a temperature in the range of 500 to 700 ° C and a magnesium agent that sinters magnesium hydroxide at a temperature in the range of 450 to 650 ° C At least one of them is added to the treated water containing the substance to be removed.

In the water treatment method, it is preferable that the magnesium agent has a BET specific surface area of 85 m ² / g or more and a crystallite size of 110 Å or less.

In the water treatment method, it is preferable that the water to be treated contains at least one of boron, fluorine, selenium, a heavy metal or a compound thereof, or silicon dioxide as the substance to be removed.

The water treatment method may further include: a step of performing an insolubilization reaction to remove a target substance after adding the magnesium agent to the water to be treated; and solid-liquid separation of the insolubilized insoluble matter. And the magnesium agent is added to the water to be treated in such an amount that the pH of the insoluble matter before the solid-liquid separation becomes 10 or more.

In addition, the present invention is a magnesium agent for water treatment, comprising at least one sintered product of basic magnesium carbonate and magnesium hydroxide, a BET specific surface area of 85 m ² / g or more, and a crystallite size of 110 Å or less.

In addition, the present invention is a method for producing a magnesium agent for water treatment, in which alkaline magnesium carbonate is sintered at a temperature in a range of 500 to 700 ° C, or magnesium hydroxide is in a range of 450 to 650 ° C. Sintered at this temperature to obtain a magnesium agent.

In the method for producing a magnesium agent for water treatment, it is preferable that the magnesium agent has a BET specific surface area of 85 m ² / g or more and a crystallite size of 110 Å or less. [Inventive effect]

According to the present invention, it is possible to provide a water treatment method, a magnesium agent for water treatment used in the water treatment, and a method for producing the magnesium agent for water treatment; the water treatment method can include water for removing an object substance from the object to be removed The substance undergoes insolubilization and solid-liquid separation in a short time to obtain treated water with good water quality, which effectively reduces the volume of the separated solid.

Hereinafter, embodiments of the present invention will be described. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

The water treatment method according to the embodiment of the present invention is a magnesium agent containing magnesium oxide obtained by sintering alkaline magnesium carbonate at a temperature in the range of 500 to 700 ° C as a main component, and magnesium hydroxide at 450 to A method of adding at least one of the magnesium agents obtained by sintering at a temperature of 650 ° C as a main component to the treated water containing the target substance. By this method, a cheap magnesium salt can be used to self-contain water for removal of the substance to be removed, and the substance to be removed can be insolubilized and solid-liquid separated in a short period of time to obtain treated water of good water quality. Reduce solids. In addition, since inexpensive magnesium salts can be used efficiently, the cost of medicines required for processing can be reduced. The magnesium agent for water treatment according to the embodiment of the present invention contains at least one sintered product of basic magnesium carbonate and magnesium hydroxide, has a BET specific surface area of 85 m ² / g or more, and a crystallite size of 110 Å or less. The method for producing a magnesium agent for water treatment according to the embodiment of the present invention is to sinter alkaline magnesium carbonate at a temperature in the range of 500 to 700 ° C, or to make magnesium hydroxide in the range of 450 to 650 ° C. A method for sintering at a temperature to obtain a magnesium agent.

[Magnesium agent] As raw materials for manufacturing the magnesium agent used in the water treatment method of this embodiment, basic magnesium carbonate (mMgCO ₃ · Mg (OH) ₂ · nH ₂ O) and magnesium hydroxide (Mg (OH) ₂ ) At least one of them. Among them, basic magnesium carbonate is one in which m is 3 to 5 and n is 3 to 7 with respect to Mg (OH) ₂ .

The temperature used as the raw material for sintering is in the range of 500 to 700 ° C when alkaline magnesium carbonate is used as the raw material, more preferably in the range of 500 to 650 ° C, and even more preferably in the range of 550 to 650 ° C. When magnesium hydroxide is used as a raw material, the range is 450 to 650 ° C, and the range of 450 to 550 ° C is more preferable. By sintering the raw materials at a temperature in this range, hydrated water or hydroxyl groups in the raw materials are desorbed through a dehydration reaction. When basic magnesium carbonate is used as a raw material, carbonic acid is also desorbed through a decarbonation reaction to generate magnesium oxide as a main component. Of matter. It is considered that the substance has a large specific surface area (for example, a BET specific surface area of 80 m ² / g or more) due to detachment of hydrated water, hydroxyl group, carbonic acid, and the like. On the other hand, the size of the crystallites of the magnesium agent containing the obtained magnesium oxide as a main component is smaller than that in the case of sintering at a temperature higher than 700 ° C, and the crystallinity is low. It is considered that due to such a large specific surface area and low crystallinity, it can dissolve in water faster than conventional magnesium oxide. It is considered that when the sintering temperature is less than 500 ° C, the specific surface area is small due to failure to sufficiently separate hydrated water, hydroxyl groups, carbonic acid, etc., and the dissolution rate in water cannot be increased. On the other hand, it is considered that when the sintering temperature is higher than 700 ° C, the crystallinity of a substance containing magnesium oxide as a main component is high, and it becomes difficult to dissolve in water.

The sintering time is the time when the weight of the sintering is reduced to more than 50% of the weight of the raw material when the basic magnesium carbonate is used as the raw material, preferably the time of 50% to 65%; when magnesium hydroxide is used as the raw material, The time when the weight reduction due to sintering becomes 25% or more of the weight of the raw material, preferably 25% or more and less than 30%, and the BET specific surface area becomes 85m ² / g or more, and the crystallite size becomes 110Å or less The time is better.

Basic magnesium carbonate and magnesium hydroxide used as raw materials for sintering are used in powder form (for example, 0.5 μm to 30 μm in terms of volume average particle diameter) and granular ( For example, the volume average particle diameter is preferably 0.5 μm to 2 μm).

Magnesium BET specific surface area of the thus obtained, for example, the Department of 80m ² / g or more, 85m ² / g or more is preferred, 100m ² / g or more is more preferable. The upper limit of the BET specific surface area is not particularly limited, and as large as possible, the better. If the BET specific surface area of the magnesium agent is less than 80 m ² / g, it may become difficult to dissolve in water. The BET specific surface area of the magnesium agent can be measured by a method according to JIS8830: 2013.

As an index indicating the crystallinity of the magnesium agent, the crystallite size obtained by the Halder-Wagner method based on the measurement result of the X-ray diffraction spectrum can be used. From the viewpoint of solubility in water, the crystallite size is preferably 110 Å or less, and more preferably 100 Å or less. When the crystallite size is larger than 110 Å, the crystallinity is high and it may become difficult to dissolve in water. The crystallite size is as small as possible.

The particle diameter of the magnesium agent is preferably a volume average particle diameter of 1,000 μm or less, and more preferably in a range of 0.5 μm to 30 μm. If the volume average particle diameter of the magnesium agent is more than 1,000 μm, the inside of the particles cannot sufficiently contact with water even in water, and the proportion of insolubilization that is not used to remove the target substance in the reagent increases. In the solid-liquid separation after the insoluble substance is removed, the unused part has the effect of increasing the solid-liquid separation speed. However, if the unused part is too much, the object to be removed cannot be sufficiently insolubilized. The quality of the treated water may be deteriorated, or the amount of magnesium added may be increased in order to sufficiently dissolve the substance to be removed. If the volume average particle diameter is less than 0.5 μm, it may be difficult to handle such as scattering due to wind during use.

When the volume average particle diameter of the sintered magnesium agent is greater than 1,000 μm, the raw materials whose volume average particle diameter after sintering becomes the particle diameter in this range can be adjusted by grinding or sieving after sintering. path.

[Water treatment method] When the magnesium agent used in the water treatment method of this embodiment is added to water, a part thereof is dissolved to become magnesium ions and hydroxide ions, and the pH of the water to be treated becomes high. At this time, if it is a substance which is co-precipitated by forming an insoluble matter with magnesium ions, it becomes a substance to be removed from the above-mentioned magnesium agent. In addition, the pH of the water to be treated becomes higher, and magnesium ions and hydroxide ions form insoluble matter of magnesium hydroxide, and substances adsorbed on the insoluble matter also become substances to be removed. That is, the substances to be removed included in the water to be treated are not particularly limited as long as they form an insoluble matter with the above-mentioned magnesium agent, or are insoluble by being adsorbed on insoluble magnesium hydroxide or the like, And boron (such as borate ion), fluorine (such as fluoride ion), selenium (such as selenate ion (SeO ₄ ^2- : hexavalent selenium), selenite ion (SeO ₃ ^2- : quaternary selenium)), At least one of heavy metals (such as iron, lead, copper, chromium, cadmium, mercury, zinc, arsenic, manganese, nickel, etc.) or these compounds (such as arsenic acid), or silicon dioxide is preferred.

The water to be treated is not particularly limited as long as it contains at least one of the above-mentioned substances to be removed. When the water to be treated is water containing two or more of the above-mentioned substances to be removed, the water treatment method of this embodiment can be suitably applied. The treated water may be water discharged on the premise that it is discharged to a public water area after the treatment, or water that is prepared on the premise that the soluble substance is removed using a purification means such as a reverse osmosis membrane and reused. Examples of the former include desulfurization drainage or plating drainage of coal-fired thermal power plants, drainage of glass manufacturing, and the like. In the latter case, the water in the water recovery systems of factories in various industries is targeted, and the water treatment method of this embodiment is implemented before the reverse osmosis membrane treatment step, so as to reduce the oxidization of the reverse osmosis membrane and the like. Silicon is used as the main purpose. In addition, since the magnesium agent used in the water treatment method of this embodiment can aggregate suspended matter in water, the water to be treated may also contain suspended matter other than the target substance.

The content of the substance to be removed in the treated water is, for example, in the range of 0.01 to 50 mmol / L, and the content of the suspended substance is in the range of, for example, 50 to 1,000 mg / L.

The content of boron in the treated water is, for example, in a range of 10 mg / L to 550 mg / L, and preferably in a range of 20 mg / L to 500 mg / L. The content of fluorine in the treated water is, for example, in the range of 15 mg / L to 950 mg / L, and preferably in the range of 20 mg / L to 100 mg / L. The content of selenium in the treated water is, for example, in a range of 0.1 mg / L to 10 mg / L, and preferably in a range of 0.2 mg / L to 2 mg / L. The content of the heavy metal in the water to be treated is, for example, in a range of 0.1 mg / L to 100 mg / L, and preferably in a range of 0.1 mg / L to 20 mg / L. The content of silicon dioxide in the treated water is, for example, in a range of 10 mg / L to 120 mg / L, and preferably in a range of 40 mg / L to 120 mg / L. The water treatment method according to this embodiment is particularly preferably applicable to treated water containing boron with a high concentration of 100 mg / L or more.

The water treatment method of this embodiment includes: a magnesium agent that sinters alkaline magnesium carbonate at a temperature in the range of 500 to 700 ° C; and a magnesium agent that sinters magnesium hydroxide at a temperature in the range of 450 to 650 ° C. At least one of these is added to the treated water step (addition step) including the removal target substance. The water treatment method according to this embodiment may further include a step of insolubilizing the object to be removed (insolubilization step) after adding a magnesium agent to the water to be treated, and subjecting the insolubilization step to insolubilization. The step of solid-liquid separation of insoluble matter (solid-liquid separation step).

In the adding step, the magnesium agent can be added to the treated water while maintaining the powder state, and the magnesium agent can also be added to the clear water with a small content of the target substance or suspended substance (for example, industrial water or using The treated water treated by the water treatment method according to the embodiment is adjusted to a pH near neutral (for example, pH 6 to pH 8 water), and the water is added to the water to be treated. From the viewpoint of simple operation and the like It is preferable to add the magnesium agent to the water to be treated while maintaining the powder state.

Since the added magnesium agent is immediately and sufficiently dispersed in the water to be treated, it is easier to exert the effect. Therefore, the addition of the magnesium agent to the water to be treated can be performed while the water to be treated is sufficiently stirred by a stirring device or the like. .

The amount of magnesium added in the addition step varies depending on the type and concentration of the target substance to be removed in the treated water, and the required treated water quality (target substance removal rate), coexisting substances, etc., but it can be added in solid-liquid separation The pH of the water to be treated before the step is 10 or more, preferably an amount of 10.5 or more.

For example, when the treated water contains 500 mg-B / L of boron compound (boric acid) as a substance to be removed, and if it is to be reduced to less than 230 mg-B / L in the sea area, you can add 7.5 to 10 g / L of Magnesium.

The insolubilization step is a step of reacting magnesium with a substance to be removed after adding a magnesium agent, and insolubilizing the substance to be removed. In this step, the pH of the water to be treated can be monitored so that the pH before the solid-liquid separation step becomes 10 or more, preferably 10.5 or more.

The reaction temperature in the insolubilization step is, for example, as long as the water to be treated is 0 ° C or higher without freezing, but the higher the temperature, the better the removal performance of the target substance, preferably 15 ° C or higher, and more preferably 20 ° C. -40 ° C range.

The reaction time in the insolubilization step is not particularly limited as long as the insolubilization of the target substance can be performed sufficiently, and it is, for example, in the range of 1 minute to 720 minutes, and preferably in the range of 10 to 120 minutes. If the reaction time in the insolubilization step is less than 1 minute, the insolubilization of the target substance may not be sufficiently performed, and if the reaction time is longer than 720 minutes, a greater reduction effect of the target substance may not be obtained.

The solid-liquid separation method in the solid-liquid separation step is not particularly limited as long as it is a method capable of separating insoluble matter and treated water. As a solid-liquid separation method, precipitation separation is the simplest and most convenient operation, and it is also possible to supply fine air bubbles for floating separation, or to perform membrane filtration through a precision filtration membrane or the like. It is also possible to perform vacuum suction filtration or pressure filtration through a filter cloth. The slurry containing the separated solid components may be further filtered by vacuum suction or pressure filtration using a filter cloth or the like to perform solid-liquid separation.

In addition, after the insolubilization step and before the solid-liquid separation step, in order to increase the solid-liquid separation speed of the insoluble matter in the solid-liquid separation step, it may be provided that a coagulant such as a polymer coagulant is added to the treated water. A step of aggregating insoluble matter and growing it into a granular material having a large diameter and strength (aggregation step).

Examples of the coagulant used in the coagulation step include an inorganic coagulant and a polymer coagulant, and examples of the polymer coagulant include a cationic polyacrylamide. The addition amount of the coagulant such as a polymer coagulant is, for example, in the range of 1 to 10 mg / L, and the reaction time is in the range of, for example, 3 to 15 minutes.

The treated water obtained by the water treatment method of this embodiment can be discharged to public water areas such as the ocean, and can also be reused.

The content of the substance to be removed in the treated water obtained by the water treatment method of this embodiment is, for example, 30 mmol / L or less, and the content of the suspended substance is, for example, 20 mg / L or less.

The content of boron in the treated water is, for example, 250 mg / L or less, and preferably 200 mg / L or less. The content of fluorine in the treated water is, for example, 15 mg / L or less, and preferably 8 mg / L or less. The content of selenium in the treated water is, for example, 0.1 mg / L or less, and preferably 0.05 mg / L or less. The content of the heavy metal in the treated water is, for example, 2 mg / L or less, and preferably 1 mg / L or less. The content of silicon dioxide in the treated water is, for example, 20 mg / L or less, and preferably 10 mg / L or less. According to the water treatment method of this embodiment, it is possible to obtain treated water having a boron content of 250 mg / L or less from to-be-treated water containing a high concentration of boron of 500 mg / L or more. [Example]

Examples and comparative examples are given below to describe the present invention in more detail, but the present invention is not limited to the following examples.

<Examples 1-1 to 1-5, 2-1 to 2-5, Comparative Examples 1-1 to 1-5, and 2-1 to 2-2> [Preparation of magnesium agents] Measure 10 parts of 5g of alkali Magnesium carbonate (manufactured by Wako Pure Chemical Industries, Ltd., heavy) at 400 ° C (Comparative Example 1-1), 450 ° C (Comparative Example 1-2), 500 ° C (Example 1-1), and 550 ° C ( Example 1-2), 600 ° C (Example 1-3), 650 ° C (Example 1-4), 700 ° C (Example 1-5), 800 ° C (Comparative Example 1-3), 900 ° C ( Comparative Examples 1-4) and 1000 ° C (Comparative Examples 1-5), after reaching each temperature, they were sintered in an electric furnace for 1 hour. In addition, 7 parts of 5 g of magnesium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were measured at 400 ° C (Comparative Example 2-1), 450 ° C (Example 2-1), and 500 ° C (Example 2-2). ), 550 ° C (Example 2-3), 600 ° C (Example 2-4), 650 ° C (Example 2-5), 700 ° C (Comparative Example 2-2), and after reaching each temperature, they were placed in an electric furnace. Sintered for 1 hour.

After sintering, it was left to cool, and the BET specific surface area of each magnesium agent obtained was measured by a specific surface area measuring device (ASAP2010) made by Shimadzu Corporation according to JIS8830: 2013.

In addition, in order to confirm the crystal state of the magnesium agent sintered at each temperature, an X-ray diffraction (XRD) spectrum was measured using an X-ray diffraction device (Rigaku Co., Ltd., RINT Ultima III). In addition, in the measurement of the X-ray diffraction spectrum, in order to confirm the occurrence position of the peak of the magnesium oxide (horizontal axis 2θ (θ: Bragg angle)), the amount of magnesium oxide (manufactured by Wako Pure Chemical Industries, Wako Grade 1, heavy) was measured. X-ray diffraction spectrum is used as a comparison reference. From the peaks of 2θ = 42.9 ° and 62.2 ° of the spectrum, the crystal size of silicon (powder, 4N, manufactured by Kanto Chemical Co., Ltd.) was used as an external standard, and the crystallite size was calculated by the Halder-Wagner method. Among them, the Halder-Wagner method draws a graph represented by (β / tanθ) ² = (Kλ / L) × [β / (tanθ × sinθ)] + 16 × e ² based on the integral width of the wave peaks. From the slope ( Kλ / L) Method for calculating the crystallite size. Here, β is the integral width of the peak, θ is the Bragg angle, K is the Xerox constant, L is the crystallite size, λ is the wavelength of X-rays, and e is the lattice strain.

The weight of the magnesium agent before and after sintering and its reduction rate (reduction rate (%) = (weight before sintering-weight after sintering) ÷ weight before sintering × 100), BET specific surface area (m ² / g), crystallite size (Å ) Are shown in Tables 1 and 2, and X-ray diffraction spectra are shown in Figs.

【Table 1】 ※ Weight reduction rate (%) = (weight before sintering-weight after sintering) ÷ weight before sintering × 100

As shown in Table 1, when alkaline magnesium carbonate is used as the raw material, the reduction rate of the comparative example 1-1 at 400 ° C is 26.8%, which is smaller than that of other sintering temperatures. From the sintering temperature of 450 ° C ( In the case of Comparative Example 1-2), the reduction rate was 51.2% and it became large rapidly. It is considered that in the case of 400 ° C of Comparative Example 1-1, carbonic acid or the like remained in the magnesium agent. From the case that the sintering temperature is 500 ° C or higher after Example 1-1, the increase in the reduction rate with the increase in the sintering temperature is small. It can be estimated that the sintering temperature is 500 ° C or higher, and moisture, carbonic acid, and the like have been sufficiently vaporized.

As shown in FIG. 1, in the XRD spectrum at a sintering temperature of 500 ° C. or higher, the same spectrum as that of the known magnesium oxide measured as a reference for comparison, and peaks appeared at 2θ = 42 ° and 62 °. From this, it can be confirmed that the cases where the sintering temperature is 500 ° C or higher (Examples 1-1 to 1-5 and Comparative Examples 1-3 to 1-5) are all magnesium oxide as the main component.

As shown in Table 1, regarding the specific surface area of the magnesium agent, when the sintering temperature of Comparative Examples 1-1 to 1-2 is 450 ° C or lower, the BET specific surface area is smaller than 36.0 m ² / g; In the cases of Examples 1-1 to 1-5 at a temperature of 500 ° C to 700 ° C, the BET specific surface area was large and was 85.4 to 148 m ² / g. In addition, if the sintering temperature is higher than 700 ° C, the BET specific surface area tends to be small, and the BET specific surface area of Comparative Examples 1-3 to 1-5 at a sintering temperature of 800 ° C or higher is 119 m ² / g or less.

On the other hand, regarding the crystal size of the magnesium agent, from the crystallite size calculated by the Halder-Wagner method based on the XRD spectrum, the sintering temperature tends to become larger as the sintering temperature becomes higher than 450 ° C ( In the case of Comparative Examples 1-1 to 1-2), the temperature was 36.1 ° C or less, and the sintering temperature was 500 to 700 ° C (Examples 1-1 to 1-5). The temperature was 54.0 to 97.4 ° C, and the sintering temperature was 800 ° C or more (Comparative Example). In the case of 1-3 to 1-5), it is 201 Å or more.

【Table 2】 ※ Weight reduction rate (%) = (weight before sintering-weight after sintering) ÷ weight before sintering × 100

As shown in Table 2, when magnesium hydroxide was used as the raw material, the reduction rate of Comparative Example 2-1 at 400 ° C was 12.6%, which was smaller than that of other sintering temperatures. In the case of Example 2-1), the reduction rate was 27.0% and it became sharply larger. In the case of 400 ° C of Comparative Example 2-1, it is considered that undehydrated magnesium hydroxide remained in the magnesium agent. From the case where the sintering temperature is 450 ° C or higher after Example 2-1, and the increase in the decrease rate with the increase in the sintering temperature is small, it can be estimated that the case where the sintering temperature is 450 ° C or higher is sufficiently dehydrated.

As shown in FIG. 2, in the XRD spectrum at a sintering temperature of 450 ° C. or higher, the peaks appeared at 2θ = 42 ° and 62 ° in the same spectrum as that of the known magnesium oxide measured as a reference for comparison. From this, it was confirmed that the cases where the sintering temperature was 450 ° C or higher (Examples 2-1 to 2-5 and Comparative Example 2-2) were all magnesium oxide as the main component.

As shown in Table 2, regarding the specific surface area of the magnesium agent, when the sintering temperature of Comparative Example 2-1 was 400 ° C, the BET specific surface area was 81.9 m ² / g or less, and the sintering temperature was 450 ° C to In the cases of Examples 2-1 to 2-5 at 650 ° C, the BET specific surface area was large and was 111 to 229 m ² / g. In addition, if the sintering temperature is higher than 550 ° C, the BET specific surface area tends to be small, and the BET specific surface area of Comparative Example 2-2 at a sintering temperature of 700 ° C or higher is 76.4 m ² / g.

On the other hand, regarding the crystal size of the magnesium agent, from the crystal size calculated by the Halder-Wagner method based on the XRD spectrum, the sintering temperature tends to become larger as the sintering temperature becomes higher, compared to 400 ° C (comparative example) 2-1) is 54.8 ° C or less, sintering temperature is 450 to 650 ° C (Examples 2-1 to 2-5) is 64.1 to 107 ° C, and sintering temperature is 700 ° C (Comparative Example 2-2) is 158 ° C. .

[Water treatment method] Here, water is treated with boron-containing water using a magnesium agent that sinters alkaline magnesium carbonate or magnesium hydroxide at various temperatures.

(Procedure of operation) The boron-containing water is prepared by adding boric acid to distilled water so that the boron concentration becomes about 500 mg / L, and further adding potassium hydroxide so that the pH becomes 7.0. In each of the 10 beakers, 300 mL of boron-containing water was prepared, and these were used as treated water (water temperature of about 20 ° C).

While stirring the water to be treated, 7.46 g of Examples 1-1 to 1-5, 2-1 to 2-5 and Comparative Examples 1-1 to 1-5, 2-1 to 2- were respectively added thereto. After the powder of the magnesium agent produced by the manufacturing method of 2 is added, the reaction is continued by stirring for 720 minutes. Meanwhile, while continuously measuring the pH of the water to be treated with a pH sensor, 0.5 mL of the water to be treated was suitably taken from 1 minute to 720 minutes after the addition (before stopping stirring). This collected water was immediately filtered through a filter having a diameter of 0.1 μm to remove insoluble matter, and it was used as an analysis sample for the concentration of residual boron in the water at each reaction time.

In addition, immediately after the stirring was stopped for 720 minutes, 300 mL of the water to be treated was suction-filtered with a filter paper having a diameter of 0.45 μm. Measure the time (seconds) required for this filtration.

In addition, the concentration of residual boron in the treated water was analyzed by an ICP emission method using an ICP emission analysis apparatus (manufactured by Seiko Instruments, SPS7800 type) in accordance with a method prescribed in JIS 0102.

(Result) [In the case of using a sintered magnesium agent using basic magnesium carbonate as a raw material] Add each sintered magnesium agent using basic magnesium carbonate as a raw material to a pH value of the water to be treated 120 minutes after the reaction. The measurement results are shown in Fig. 3; the dissolved boron in the treated water is analyzed, and the result of calculating the residual rate of the dissolved boron (the ratio to the boron in the treated water) is shown in Fig. 4. The time required for filtration through a filter paper after a 720 minute reaction is shown in Table 3.

【table 3】

The pH after adding the magnesium agent sintered at each temperature is shown in FIG. 3. In each of the examples 1-1 to 1-5, the reaction became 10.6 or more in 10 minutes, and then changed to the range of 10.6 to 10.8. In the case of Comparative Examples 1-1 to 1-2, where the sintering temperature was low, after 10 minutes of reaction, it was 10.5 or more and the shift was 10.5 to 10.7, and in the case of Comparative Examples 1-3 to 1-5, which had a high sintering temperature, after 30 minutes It is 10.2 to 10.4, and it is also 10.3 to 10.4 after 120 minutes.

As shown in FIG. 4, the residual boron residual rate in the treated water at this time is the case of Examples 1-1 to 1-5 at a sintering temperature of 500 to 700 ° C., which is 64 to 72% in 30 minutes and 50 to 60 minutes. 62%, 28-50% for 120 minutes. In contrast, in the cases of Comparative Examples 1-1 to 1-5, the reaction was 88 to 100% for 30 minutes, 77 to 100% for 60 minutes, and 59 to 97% for 120 minutes. If it is observed up to 120 minutes, the residual boron dissolution rate at the same reaction time is significantly lower in Examples 1-1 to 1-5 than in the comparative example. It can be said that the insolubility rate of boron is the sintering temperature of 500. Examples 1-1 to 1-5 of the magnesium agent at ~ 700 ° C were significantly higher.

In addition, the residual rate of dissolved boron after a long reaction time of 720 minutes was 21 to 35% in the case of Examples 1-1 to 1-5. The comparative example was 19 to 40% except for Comparative Example 1-5, which had a sintering temperature of 1000 ° C, and no significant difference from the example was observed (the residual boron residual ratio of Comparative Example 1-5 was 60%).

However, as shown in Table 3, the filtration time (time required for filtration) when the treated water after the reaction of 720 minutes was evacuated with filter paper is shown in Table 3, and Comparative Examples 1-1 to 1 with respect to the sintering temperature of 400 to 450 ° C In the case of -2, it takes 120 to 180 seconds, and it is 32 to 50 seconds for Examples 1-1 to 1-5 and Comparative Examples 1-3 to 1-5. That is, it was confirmed that by using a magnesium agent having a sintering temperature of 500 to 700 ° C, the solid-liquid separation speed of insoluble matter was significantly increased.

These results show that those having a high boron removal rate and a high solid-liquid separation rate are Example 1 using alkaline magnesium carbonate as a raw material and adding a magnesium agent sintered at 500 to 700 ° C. 1 to 1-5. It has also been shown that a magnesium agent having a BET specific surface area of 85 m ² / g or more and a crystallite size of 110 Å or less is preferred.

[In the case of using a sintered magnesium agent using magnesium hydroxide as a raw material] The results of measuring the pH of the water to be treated after reacting with the magnesium agent using magnesium hydroxide as a raw material for 120 minutes are shown in FIG. 5 ; Analysis of the dissolved boron in the treated water, and the result of calculating the residual rate of the dissolved boron (the ratio with respect to the boron in the treated water) is shown in FIG. 6. The time required for filtration through a filter paper after 120 minutes of reaction is shown in Table 4.

【Table 4】

The pH after adding the magnesium agent sintered at each temperature is shown in Fig. 5. In each of the examples 2-1 to 2-5, the reaction became 10.3 or more in 10 minutes, and then changed to the range of 10.3 to 10.7. In Comparative Example 2-1 with a low sintering temperature and Comparative Example 2-2 with a high sintering temperature, the reaction became 10.2 to 10.3 and the shift was 10.3 to 10.4 for 10 minutes, which was slightly lower than the pH shift of the example.

As shown in FIG. 6, the residual boron residual rate in the treated water at this time is the case of Examples 2-1 to 2-5 at a sintering temperature of 450 to 600 ° C., which is 67 to 80% in 30 minutes and 48 to 60 minutes. 66%, 27 to 48% for 120 minutes. In contrast, in the cases of Comparative Examples 2-1 and 2-2, the reaction was 87% for 30 minutes, 75 to 77% for 60 minutes, and 59 to 64% for 120 minutes. If it is observed until 120 minutes, from the point that the residual boron-based examples 2-1 to 2-5 are significantly lower, it can be said that the insolubility rate of boron is the example 2 in which a magnesium agent having a sintering temperature of 450 to 650 ° C is added. -1 ～ 2-5 is significantly higher.

In addition, the residual rate of dissolved boron after a long reaction time of 720 minutes was 16 to 24% in the case of Examples 2-1 to 2-5. Comparative Example 2-2 is 17%, which is the same as the example, and Comparative Example 2-1 is 56%, which is significantly different from the example.

The filtration time (time required for filtration) when the treated water after the reaction of 720 minutes was evacuated with filter paper is shown in Table 4. Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2- Both are 28 to 50 seconds, which is a greatly shortened filtration time compared to the filtration time of Examples 1-1 to 1-5. That is, it was confirmed that a high solid-liquid separation rate can be obtained by using a magnesium agent having a sintering temperature of 450 to 650 ° C.

These results show that those having a high boron removal rate and also a high solid-liquid separation rate are Example 2 in which a magnesium agent obtained by using magnesium hydroxide as a raw material and sintered at 450 to 650 ° C is added. 1 to 2-5. It has also been shown that a magnesium agent having a BET specific surface area of 85 m ² / g or more and a crystallite size of 110 Å or less is preferred.

As described above, at least one of a magnesium agent that sinters alkaline magnesium carbonate at a temperature in the range of 500 to 700 ° C and a magnesium agent that sinters magnesium hydroxide at a temperature in the range of 450 to 650 ° C is used. In the examples, it is shown that the object to be removed can be self-contained, and the object to be removed can be insolubilized and solid-liquid separated in a short time to obtain treated water of good water quality, which can effectively reduce the volume of the separated solid. .

no

[Fig. 1] X-ray diffraction spectra of each magnesium agent in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5. [Fig. 2] X-ray diffraction spectra of each magnesium agent in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2. [Fig. 3] A graph showing the measurement results of the pH of the treated water 1 to 120 minutes after the addition of each magnesium agent in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5. [Fig. 4] An analysis showing the residual ratio (%) of dissolved boron in the treated water 1 to 120 minutes after the addition of each magnesium agent in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5 Graph of results. [Fig. 5] A graph showing the measurement results of the pH of the treated water 1 to 120 minutes after the addition of each magnesium agent in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2. [Fig. 6] Analysis of the residual boron residual ratio (%) in treated water from 1 to 120 minutes after the addition of each magnesium agent in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2 Graph of results.

Claims (7)

A water treatment method, comprising: a magnesium agent that sinters alkaline magnesium carbonate at a temperature in the range of 500 to 700 ° C; and a magnesium agent that sinters magnesium hydroxide at a temperature in the range of 450 to 650 ° C. At least one of these is added to the treated water containing the substance to be removed. The water treatment method according to claim 1, wherein the magnesium agent has a BET specific surface area of 85 m ² / g or more and a crystallite size of 110 Å or less. The water treatment method according to claim 1 or 2, wherein the water to be treated contains at least one of boron, fluorine, selenium, a heavy metal or a compound thereof, or silicon dioxide as the substance to be removed. The water treatment method according to claim 1 or 2, further comprising: after adding the magnesium agent to the water to be treated, performing the insolubilization reaction of removing the target substance; and insolubilizing the insoluble matter A step of performing solid-liquid separation; and adding the magnesium agent to the treated water in an amount such that the pH of the insoluble matter before the solid-liquid separation becomes 10 or more. A magnesium agent for water treatment, comprising at least one sintered substance among basic magnesium carbonate and magnesium hydroxide, a BET specific surface area of 85 m ² / g or more, and a crystallite size of 110 Å or less. A method for producing a magnesium agent for water treatment, characterized by sintering alkaline magnesium carbonate at a temperature in a range of 500 to 700 ° C, or by making magnesium hydroxide at a temperature in a range of 450 to 650 ° C. Sintered to obtain a magnesium agent. The method for producing a magnesium agent for water treatment according to claim 6, wherein the magnesium agent has a BET specific surface area of 85 m ² / g or more and a crystallite size of 110 Å or less.