JP7690189B2 - Method for producing an anion treatment agent, and method for regenerating an anion treatment agent - Google Patents

Description

The present invention relates to a method for producing an anion treatment agent used to remove anions such as fluorine, nitrogen and phosphorus compounds contained in surface water such as river water and lake water, well water, and domestic and industrial wastewater, and a method for regenerating the agent after anion treatment .

As anion treatment agents, for example, hydrotalcite granules obtained by adding an organic solvent to a mixture of hydrotalcite powder, which is a layered double hydroxide, and a polymeric compound such as aminated polyacrylamide, which is a binder, and then kneading the mixture, which is then formed in a granulator, and drying and hardening the resulting molded product, and a structure in which the kneaded mixture of hydrotalcite powder and binder is applied as a powder layer to the surface of a core material made of zeolite particles, and then dried and hardened, have been proposed (see, for example, Patent Document 1).

JP 2003-299948 A

However, since the anion exchange capacity of an anion treatment agent is proportional to the amount of layered double hydroxide contained therein, the anion treatment agents in the above-mentioned Patent Document 1 are all produced by drying and hardening a mixture of layered double hydroxide powder and binder on the surface of a core material made of zeolite particles, and the core material made of zeolite particles forms the main part of the granules, which poses the problem of limited anion exchange capacity.

In addition, the anion treatment agent of the aforementioned Patent Document 1 uses a polymeric compound such as polyacrylamide as a binder, so it is necessary to dilute the polymeric compound itself or the polymeric compound as a binder with an organic solvent to a predetermined concentration, but the organic solvent used for dilution may dissolve as a permeate into the anion treatment agent. In this case, if water treated with the anion treatment agent is used for drinking water, for example, there is a high risk that it will fall under the category of harmful organic substances such as volatile organic compounds and acrylic acid that are problematic in the TOC (total organic carbon) and compliance standards for water supply equipment and materials in the relevant drinking water quality standards, and therefore the use of polymeric compounds and the organic solvents used for diluting them should be avoided.

The present invention has been made with a focus on these problems, and aims to provide a method for producing an anion treatment agent that can improve the anion exchange capacity without using a polymer compound or an organic solvent used for diluting it, and eliminate the above-mentioned drawbacks of anion treatment agents made from layered double hydroxides as a raw material , and a method for regenerating the anion treatment agent after anion treatment .

In order to solve the above problems, the method for producing an anion treatment agent according to the present invention is characterized in that it comprises mixing a layered double hydroxide having an anion exchange capacity with feldspar clay which is prepared by grinding feldspar, a type of three-dimensional tectosilicate mainly composed of aluminosilicate, into a powder of 5 μm or less, tumbling and granulating the mixture, drying the mixture at 300° C. to 600° C., and classifying the mixture to produce an anion treatment agent.
The method for producing an anion treatment agent according to the present invention is characterized in that it comprises mixing a layered double hydroxide having an anion exchange capacity with feldspar clay which is prepared by grinding feldspar, a type of three-dimensional tectosilicate mainly composed of aluminosilicate, into a powder of 5 μm or less, tumbling and granulating the mixture to form the mixture, classifying the mixture, and then drying the mixture at 300° C. to 600° C. to produce an anion treatment agent, and reusing the raw materials that were not subjected to the molding and classification selection.
The method for regenerating an anion treatment agent according to the present invention is characterized in that the anion treatment agent is produced by grinding a layered double hydroxide having an anion exchange capacity and feldspar, which is a type of three-dimensional tectosilicate mainly composed of aluminosilicate, and mixing them with feldspar clay in a powder form of 5 μm or less , tumbling and granulating them, drying them at 300° C. to 600° C. , and then classifying them, and then adding a regenerating agent containing chloride ions to the anion treatment agent, thereby regenerating the anion treatment agent.

The anion treatment agent according to the present invention is manufactured by mixing layered double hydroxide having anion exchange capacity with feldspar clay, which is made by grinding feldspar, a type of three-dimensional tectosilicate mainly composed of aluminosilicate, into powder of 5 μm or less, tumbling and granulating it, forming it into a shape, and drying it, and therefore does not use a core material made of zeolite particles or the like as in the past. Therefore, it is possible to increase the proportion of layered double hydroxide in the granules, and the anion exchange capacity can be improved.
Furthermore, since a core material composed of zeolite particles or the like is not used, there is no need for a polymer compound such as polyacrylamide as a binder for the layered double hydroxide, and an organic solvent for diluting the polymer compound. This makes it possible to reliably prevent the organic solvent from dissolving into groundwater, etc., and causing adverse effects on the environment.
As a result, it is possible to eliminate the drawbacks of anion treatment agents made from layered double hydroxides, such as the limited anion exchange capacity and the need for polymer compounds necessary to produce the core material and organic solvents used to dilute them.
In addition, the anion treatment agent according to the present invention has the advantage that it can be easily regenerated by processing the layered double hydroxide in a powder form into granules.

FIG. 1 is a perspective view showing an example of the appearance of an anion treatment agent according to an embodiment of the present invention. FIG. 2 is a table showing an example of the composition of feldspar clay constituting the anion treatment agent according to the embodiment of the present invention. FIG. 2 is a photograph showing an example of a granule of an anion treatment agent according to an embodiment of the present invention. FIG. 1 is a graph showing the results of measuring the amount of fluorine treated per filler volume and the fluorine concentration of treated water by passing raw water through the anion treatment agent according to an embodiment of the present invention and a conventional anion treatment agent in the form of granules in which a mixture of layered double hydroxide powder and a binder is dried and hardened on the surface of a core material under specified conditions. FIG. 1 is a table showing the rate of increase in the amount of fluorine treated per volume of filler, measured by passing raw water through the anion treatment agent according to an embodiment of the present invention and a conventional anion treatment agent in the form of granules in which a mixture of layered double hydroxide powder and a binder is dried and hardened on the surface of a core material under specified conditions. FIG. 1 is a graph showing the results of measuring the water flow rate and the fluorine concentration of treated water before and after regeneration for an anion treatment agent that has not been regenerated and an anion treatment agent whose anion exchange capacity has been regenerated by a method for regenerating an anion treatment agent according to an embodiment of the present invention, in which the water flow rate SV during regeneration is changed in three stages.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the method for producing an anion treatment agent and the method for regenerating an anion treatment agent according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an enlarged view of an anion treatment agent A according to an embodiment of the present invention.
As shown in FIG. 1, the anion treatment agent A is a granular material obtained by granulating a mixture of particles of layered double hydroxide 1 having anion exchange capacity and feldspar clay 2, and is produced by granulating the mixture of layered double hydroxide 1 and feldspar clay 2, followed by drying and classification to obtain a product.

(Layered double hydroxide 1)
Layered double hydroxide 1 exists in various types, such as chloride type and carbonate type, depending on the anion species contained in the layer. When the purpose is to treat the anions of ionic fluorine, nitrogen and phosphorus compounds proposed in the embodiment of the present invention, it is desirable to use a chloride type layered double hydroxide, which has excellent anion exchange selectivity, as the raw material.

(Feldspar clay 2)
In the anion treatment agent A according to the embodiment of the present invention, in order to achieve granular formation, feldspar clay 2 that can retain its shape even in water when dried is used. The feldspar clay 2 has a composition, for example, as shown in Fig. 2, and is made by grinding feldspar, which is a type of three-dimensional tectosilicate mainly composed of aluminosilicates of alkali metals and alkaline earth metals, into a powder of 5 μm or less. In the composition shown in Fig. 2, 10 types are listed in descending order of their proportions.

<Method of producing layered double hydroxide 1 and feldspar clay 2>
Next, a method for producing the layered double hydroxide 1 and the feldspar clay 2 when producing the anion treatment agent A according to the embodiment of the present invention will be described.

(Ratio of layered double hydroxide 1 and feldspar clay 2 when kneading)
First, in the anion treatment agent A according to the embodiment of the present invention, the layered double hydroxide 1 and the feldspar clay 2 are kneaded at a weight ratio of 10%:90% to 90%:10% to form a kneaded product.

Granulation is carried out using rolling granulation, which has the advantage of allowing all of the raw materials to be used by turning the kneaded material into granules as is. When granulating, 10% to 40% water (by weight, assuming 100% raw materials) is added to allow the raw materials to maintain their granular shape.

The granules obtained by rolling granulation are classified using two sieves with different openings between 0.1 mm and 2.0 mm, and the granules remaining between the two sieves are transferred to the drying process.

The material that falls through the sieve with small openings during the classification process and the material that remains on the sieve with large openings are ground without being dried, and turned into a powder of 5 μm or less, which can be used as raw material for the next production run.

The outer parts of the product that are generated when granules are manufactured using feldspar clay 2 lose their moldability when they go through the drying process, making it impossible to mold them again. However, this method does not go through the drying process, so it has the advantage of making it possible to mold them again.

The granules are classified using two types of sieves with different openings of 0.1 mm to 2.0 mm, and the granules remaining between the two sieves are dried at 300°C to 600°C in a drying process, completing the production of anion treatment agent A according to an embodiment of the present invention. Drying increases the strength of the granules, allowing them to retain the shape of the granules even in water when used to treat anions dissolved in water.

<Test on anion exchange capacity of anion treatment agent A>
One of the advantages of the anion treatment agent A according to the embodiment of the present invention is the improvement of the anion exchange capacity. The anion exchange capacity of the anion treatment agent A in the form of a granule was investigated. The granules of anion treatment agent A, which were prepared by rolling granulation of a chlorine-type layered double hydroxide 1 and a feldspar clay 2 in a weight ratio of 50% each, sieved with 0.3 mm and 1.0 mm sieves, and dried at 500° C., looked, for example, like the photograph shown in FIG.

When the anion exchange capacity of anion treatment agent A according to an embodiment of the present invention was compared with that of a conventional granulated anion treatment agent in which a mixture of layered double hydroxide 1 powder and a binder was dried and hardened on the surface of a core material, tests were conducted under the following conditions, and the anion exchange capacity of anion treatment agent A according to an embodiment of the present invention was confirmed to be improved.

(Test conditions)
The test conditions were as follows: a column was filled with anion treatment agent A according to an embodiment of the present invention, and a conventional granulated anion treatment agent in which a mixture of layered double hydroxide 1 powder and a binder was dried and hardened on the surface of a core material; raw water in which anions were dissolved was passed through at a constant filtration speed and flow rate; and the anions in the treated water were analyzed to confirm the anion exchange capacity of anion treatment agent A according to an embodiment of the present invention and the conventional granulated anion treatment agent.

・Treated anion: Fluoride ion ・Raw water: Sodium fluoride was added to purified water to adjust the fluoride ion concentration to 9.0-9.5 mg/L ・Filter layer thickness: 300 mm
Filtration speed: SV (space velocity) 10h ^-1
-End point: Until the fluoride ion concentration in the treated water is the same as that in the raw water.
The fluorine treatment amount per packing volume and the fluorine concentration of the treated water when raw water was passed through under the above conditions are shown in a graph in FIG. 4, and the fluorine treatment capacity per packing volume when the end point was reached and the rate of increase in the fluorine treatment amount (mg/mL) of the conventional product and the anion treatment agent A of the present embodiment are shown in a table in FIG. 5.

As shown in Figures 4 and 5, in the case of the conventional product, which is a conventional granule in which a binder mixture is dried and hardened on the surface of a core material, the amount of fluororesin is only about 5.2 mg/mL, whereas in the anion treatment agent A of the embodiment of the present invention, the amount of fluororesin is about 9.4 mg/mL. This means that the anion treatment agent A of the embodiment of the present invention treats 180% more fluoride ions than the conventional product, proving the improvement of the anion exchange capacity.

<Effects of the anion treatment agent A according to the embodiment of the present invention>
As described above, the anion treatment agent A of the embodiment of the present invention can provide a treatment agent that has better anion exchange capacity for fluorine, phosphorus, etc. than conventional anion treatment agents, and in particular, since the anion treatment agent A is a granule of a kneaded product of layered double hydroxide 1 and feldspar clay 2 and does not use a core material composed of zeolite particles or the like, it can eliminate concerns about organic solvents leaking into the permeate.

In addition, the anion treatment agent A according to the embodiment of the present invention does not use a core material made of zeolite particles or the like, so it is possible to increase the proportion of layered double hydroxide 1 in the granules, thereby improving the anion exchange capacity.

In addition, by processing the layered double hydroxide 1 from powder to granules, it has the advantage of being easily regenerated.

Furthermore, as described below, the non-product material generated during production can be reused as raw material, making this an economical and clean method for producing granules that does not generate waste. By carrying out a regeneration operation after anion exchange, the anion exchange capacity can be repeatedly maintained.

<Regeneration operation of anion treatment agent>
Next, the regeneration operation of the anion treatment agent according to the embodiment of the present invention will be described.

It is generally known that layered double hydroxide 1 has anions in its structure and has anion exchange ability. The ease with which anions are exchanged, or so-called selectivity, varies depending on the type of anion. The anion that shows the lowest selectivity for layered double hydroxide 1 is the chloride ion. Therefore, when used for the purpose of anion exchange, it is used as a so-called "chlorine-type layered double hydroxide." The anion to be exchanged is exchanged with the chloride ion, the chloride ion is released into the water, and the anion to be exchanged is taken up into the correlation of layered double hydroxide 1, as if it had been removed.

As the exchange progresses, the chloride ions in layered double hydroxide 1 disappear, and the correlation is satisfied with the anions to be exchanged. When this state is reached, the anion exchange capacity is lost.

Therefore, a so-called regeneration operation is required to return the chlorine-type layered double hydroxide 1 to have anion exchange capacity again.

However, layered double hydroxide 1 is a powder, and recovery after processing and regeneration is difficult. In addition, there has been no economical method to regenerate it into the chloride ion form until now, so it has had to be discarded after use. By making it granular, recovery has become easier.

As a cheap regeneration method, we investigated an economical method that uses substances containing chloride ions.

The outline of the study is as follows:
In other words, water containing anions that are more selective than chloride ions (fluoride ions, sulfate ions, ionic silica, phosphate ions, bicarbonate ions, carbonate ions) is passed through a column packed with granules of anion treatment agent A of an embodiment of the present invention, which is composed of a chlorine-type layered double hydroxide 1 and feldspar clay 2, to exchange the anions for chloride ions until a state in which no more anions can be exchanged is reached.

In this state, a regenerating liquid containing chloride ions is passed through the anion treatment agent A to perform the regeneration operation. The regeneration operation of the anion treatment agent A after the anion exchange is completed includes the following three steps (1) to (3):
(1) A cleaning process using treated water; (2) A regeneration process using regenerated liquid; and (3) An extrusion cleaning process using treated water.

(1) Washing process with treated water In the washing process with treated water, anion exchange treated water or purified water is passed through. The water may be passed in either the forward or reverse direction of the treatment. The water passing speed is 2 to 50 m/h as linear velocity LV or 2 to 50 h ^-1 as space velocity SV. A linear velocity LV of 5 to 30 m/h is particularly suitable. The water passing time is 5 to 60 minutes, with 10 to 30 minutes being suitable.

(2) Regeneration process using regenerating liquid In the regeneration process, the following regenerating liquid is passed through. The concentration of the regenerating liquid should be between 10 g/L and the saturated concentration, with 20 g/L or more being particularly suitable. The water may be passed in either the forward or reverse direction of the treatment, but the reverse direction is suitable. The water passing speed should be 2 to 50 h ^-1 in terms of space velocity SV, with 2.5 to 20 h ^-1 being particularly suitable. The water passing time should be 0.5 to 10 hours, with 1 to 4 hours being particularly suitable.

(3) Extrusion process In the extrusion process, anion exchange treated water or purified water is passed through. The water may be passed in either the forward or reverse direction of the treatment. The water passing speed is 2 to 50 h ^-1 in terms of space velocity SV, with 5 to 20 h ^-1 being particularly suitable. The water passing time is 5 to 60 minutes, with 10 to 30 minutes being suitable.

After the extrusion process is completed, the treated raw water is passed through the anion exchange process again.

The test was carried out as follows to confirm the regeneration of anion exchange capacity. It was carried out under four conditions in total, including no regeneration and three different water flow rates (SV) during regeneration.

The common conditions are as follows:
Water column inner diameter: 13 mm
・Granule layer thickness: 300mm
・Amount of filled granules: 40mL

(1) Conditions for the anion exchange process: Raw water: Purified water with sodium fluoride dissolved in it Raw water concentration: 10 mg/L as fluoride
・Flow rate: 400mL/h
・Water flow speed: SV 10h ^-1
-End point: The point at which the fluorine content of the treated water is equal to or greater than that of the raw water.

(2) Conditions for the washing process Washing water: Purified water Flow rate: 2,000 mL/h
・Water flow speed: LV 15m/h (SV 50h ^-1 )
Cleaning process time: 15 minutes

(3) Conditions for the regeneration process (without regeneration)
Regenerated liquid: Purified water with sodium chloride dissolved in it Regenerated liquid concentration: 180g/L as chloride ions (300g/L as sodium chloride)
・Flow rate: 400mL/h
・Water flow rate: Run-1 SV10h ^-1 , Run-2 SV5h ^-1 , Run-3 SV2.5h ^-1
・Regeneration process time: Run-1 1h, Run-2 2h, Run-3 4h

(4) Conditions for the extrusion washing process: Extrusion liquid: Purified water Flow rate: 400 mL/h
・Water flow speed: SV 10h ^-1
Extrusion process time: 30 minutes

(5) Conditions for the process to confirm the regeneration of anion exchange capacity: Raw water: Purified water with sodium fluoride dissolved in it Raw water concentration: 10 mg/L as fluoride
・Flow rate: 400mL/h
・Water flow speed: SV 10h ^-1
-End point: The point at which the fluorine content of the treated water is equal to or greater than that of the raw water.

Figure 6 shows the results of measuring the water flow rate and fluorine concentration of treated water before and after regeneration for an anion treatment agent without regeneration and for an anion treatment agent A whose anion exchange capacity was regenerated by a regeneration method for an anion treatment agent A according to an embodiment of the present invention, in which the water flow rate SV during regeneration was changed in three stages.

In Figure 6, circles indicate no regeneration, triangles indicate Run-1 SV10, squares indicate Run-2 SV5, and diamonds indicate Run-3 SV2.5. The plots before regeneration are solid and the plots after regeneration are white.

Under the conditions without regeneration, indicated by circles, the fluorine concentration of the treated water after the regeneration process was high, whereas under the three conditions where regeneration was performed, indicated by triangles, squares, and diamonds (Run-1 SV10, Run-2 SV5, and Run-3 SV2.5), the behavior of the fluorine treatment after regeneration was the same as that before regeneration. This indicates that the anion treatment capacity was regenerated.

A Anion Treatment Agent 1 Layered double hydroxide 2 Feldspar clay

Claims (3)

A method for producing an anion treatment agent , comprising the steps of grinding a layered double hydroxide having an anion exchange capacity and feldspar, which is a type of three-dimensional tectosilicate mainly composed of aluminosilicate, and mixing the ground feldspar clay into powder of 5 μm or less , tumbling and granulating the mixture, and then drying the mixture at 300°C to 600°C and classifying the mixture to produce an anion treatment agent. A method for producing an anion treatment agent, comprising the steps of grinding a layered double hydroxide having an anion exchange capacity and feldspar, a type of three-dimensional tectosilicate whose main component is aluminosilicate, and mixing the ground feldspar with powder of 5 μm or less, tumbling and granulating the mixture, molding the mixture, classifying the mixture, and then drying the mixture at 300°C to 600°C to produce an anion treatment agent, and reusing the raw materials that were not subjected to molding and classification. A method for regenerating an anion treatment agent , comprising the steps of: grinding a layered double hydroxide having an anion exchange capacity and feldspar, which is a type of three-dimensional tectosilicate mainly composed of aluminosilicate, into powder form of 5 μm or less; mixing the mixture with feldspar clay; rolling granulating the mixture; drying the mixture at 300°C to 600°C ; and classifying the mixture; and adding a regenerating agent containing chloride ions to the anion treatment agent to regenerate the anion treatment agent.

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