JP2005324128A - Phosphorus removing agent and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphorus removing agent of which the active ingredients are hydrotalcites not only having a high removal ratio of phosphorus dissolved in water, but also being excellent in handling and durability, and its manufacturing method. <P>SOLUTION: In the agent for removing phosphorus dissolved in water, the hydrotalcites represented by general formula (I), M<SP>2+</SP><SB>1-x</SB>M<SP>3+</SP><SB>x</SB>(OH<SP>-</SP>)<SB>2</SB>A<SP>n-</SP><SB>x/n</SB>-mH<SB>2</SB>O (wherein M<SP>2+</SP>is at least one divalent metal ion selected from Mg<SP>2+</SP>, Zn<SP>2+</SP>, and Cu<SP>2+</SP>; M<SP>3+</SP>is at least one trivalent metal ion selected from Al<SP>3+</SP>and Fe<SP>3+</SP>; A<SP>n-</SP>is at least one anion selected from SO<SB>4</SB><SP>2-</SP>, Cl<SP>-</SP>, CO<SB>3</SB><SP>2-</SP>, and OH<SP>-</SP>; n is a valence of the above anion; x is a number satisfying 0<x<0.5; m is a number satisfying 0≤m<2) are made of a molded material dispersed in a porous matrix made of a water-insoluble resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a phosphorus removing agent dissolved in water and a method for producing the same.

  Purification of natural environmental waters such as rivers, lakes, ponds, dam reservoirs, seas, etc. as well as various industrial and household wastewaters such as various plating wastewaters and washing wastewaters. This is an important issue for protecting the earth's environment.

  In particular, eutrophication occurs when the phosphorus concentration in natural environmental waters such as rivers, lakes, reservoirs, and seas increases. So far, various phosphorus removal agents such as iron, aluminum compounds, activated carbon, activated sludge, etc. have been proposed, but all of these conventional phosphorus removal agents have low phosphorus removal rates and are naturally It was insufficient to prevent eutrophication of environmental water.

Thus, recently, it has been proposed to use hydrotalcites as a phosphorus removal agent that has a high phosphorus removal rate and can be regenerated (see Patent Document 1). The talcite is used as a powder as it is as a phosphorus remover, or is kneaded with water, granulated, and used as a phosphorus remover. Hydrotalcite is not easy to handle if it is in powder form, and it is low in strength even if it is simply granulated. Since collapse and channeling will occur, problems will arise in the phosphorus removal treatment from raw water.
Japanese Unexamined Patent Publication No. 2000-024658

  The present invention has been made in order to solve the above-mentioned problems related to the removal of phosphorus that have been conventionally known, in particular, the above-described problems in phosphorus removal agents comprising hydrotalcites. The purpose of the present invention is to provide a phosphorus removal agent and a method for producing the same, in which not only the removal rate of phosphorus dissolved in water is high but also the strength and handleability are excellent. To do.

According to the invention, the general formula (I)
^{_{M 2+ 1-x M 3+ x}} (OH -) 2 A n- x / n · mH 2 O ... (I)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from Mg ²⁺ , Zn ²⁺ and Cu ²⁺ , and M ³⁺ represents at least one selected from Al ³⁺ and Fe ^3+. A ⁿ⁻ represents at least one anion selected from SO ₄ ²⁻ , Cl ⁻ , CO ₃ ²⁻ and OH ⁻ , n represents the valence of the anion, and x represents (0 <x <0.5 and m is a number satisfying 0 ≦ m <2)
There is provided a remover of phosphorus dissolved in water, characterized in that the hydrotalcite represented by the formula consists of a molded product dispersed in a porous matrix made of a water-insoluble resin.

Furthermore, according to the invention, the general formula (I)
^{_{M 2+ 1-x M 3+ x}} (OH -) 2 A n- x / n · mH 2 O ... (I)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from Mg ²⁺ , Zn ²⁺ and Cu ²⁺ , and M ³⁺ represents at least one selected from Al ³⁺ and Fe ^3+. A ⁿ⁻ represents at least one anion selected from SO ₄ ²⁻ , Cl ⁻ , CO ₃ ²⁻ and OH ⁻ , n represents the valence of the anion, and x represents (0 <x <0.5 and m is a number satisfying 0 ≦ m <2)
The hydrotalcite represented by the formula is melted, kneaded and molded together with a water-insoluble resin and a water-soluble polymer substance, and then the water-soluble polymer substance is extracted with water to make the hydrotalcite porous. There is provided a method for producing a remover of phosphorus dissolved in water, characterized in that the molded article is fixed in a matrix made of a water-insoluble resin.

  The phosphorus removing agent of the present invention is a molded product in which hydrotalcites are dispersed and fixed in a porous matrix made of a water-insoluble resin, so that it is dissolved in water without being washed away in water. Phosphorus can be removed with high removal rate and high efficiency. In particular, according to the phosphorus removing agent of the present invention, for example, raw water containing phosphorus at a high concentration can be treated to remove phosphorus at a high removal rate, and also about about dissolved in water. About 90% or more can be removed even with phosphorus at a low concentration of about 5 ppm. Moreover, as described above, the phosphorus removing agent of the present invention consists of a molded product in which hydrotalcites are dispersed and fixed in a porous matrix made of a water-insoluble resin. Is convenient and has excellent durability.

The phosphorus removal agent according to the present invention has the general formula (I)
^{_{M 2+ 1-x M 3+ x}} (OH -) 2 A n- x / n · mH 2 O ... (I)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from Mg ²⁺ , Zn ²⁺ and Cu ²⁺ , and M ³⁺ represents at least one selected from Al ³⁺ and Fe ^3+. trivalent metal indicates ion, a ^{n-is _{SO 4 2-, Cl -, CO}} 3 2- and OH ^- represents at least one anion selected from, n represents indicates the valence of the anion, x Is a number satisfying 0 <x <0.5, and m is a number satisfying 0 ≦ m <2.)
It consists of hydrotalcite represented by. Such hydrotalcites can be easily obtained as commercial products, but can also be synthesized if necessary.

According to the present invention, among the hydrotalcites represented by the general formula (I), in particular, M ²⁺ is at least one selected from Mg ²⁺ and Zn, and M ³⁺ is Al. It is preferably ³⁺ and An ⁿ⁻ is at least one selected from SO ⁴⁻ and Cl ⁻ .

Hydrotalcite is known as a natural product or a synthetic product, and is a viscous mineral having a layered structure, as is well known. Natural hydrotalcite (hydrotalcite) is a hydrous basic carbonate mineral of magnesium and aluminum represented by the composition formula Mg _0.75 Al _0.25 (OH) ₂ (CO ₃ ) _0.125 · 0.5H ₂ O. Carbonate ions and crystal water are sandwiched between magnesium aluminum hydroxide layers. The same applies to the hydrotalcites represented by the general formula (I), for example, having anions such as carbonate ion, sulfate ion, chlorine ion, hydroxyl ion between magnesium hydroxide aluminum layers, The anion has ion exchange properties.

  Therefore, the phosphorus removing agent according to the present invention captures phosphate ions dissolved in water by ion exchange of the anions with phosphate ions. On the other hand, by ion exchange with such phosphate ions, anion components of hydrotalcites such as carbonate ions and sulfate ions are eluted in water, but these anions do not cause water contamination.

  The phosphorus removing agent according to the present invention is a molded product in which such hydrotalcites are dispersed and fixed in a porous matrix made of a water-insoluble resin. The water-insoluble resin is not particularly limited, and examples thereof include ethylene-vinyl acetate copolymer, polyethylene, polypropylene, vinyl chloride resin, polystyrene, polycarbonate, polyamide, ABS resin, polyacetal, polyphenylene oxide, and the like. be able to. However, it is not limited to these.

  In addition, according to the present invention, the biodegradable resin can be used as a water-insoluble resin as in the case of the above-mentioned resin if it is water-insoluble. Examples of such a biodegradable resin include polylactic acid.

  The phosphorus removing agent according to the present invention is preferably a kneaded product obtained by melting and kneading the above-described hydrotalcites with a water-insoluble resin and a water-soluble polymer substance, for example, using an extruder. Is extruded into an appropriate shape, for example, a strand, cut and formed into pellets, and then the water-soluble polymer substance is extracted from the pellets with water to make the hydrotalcite porous. It can be obtained by fixing in a matrix made of a water-insoluble resin.

  As described above, the water-soluble polymer substance can be melted and kneaded together with hydrotalcites and a water-insoluble resin, and is extracted into water when the pellet made of the kneaded material is immersed in water. Any material can be used. In the present invention, preferred specific examples of such water-soluble polymer materials include synthetic polymer materials such as polyvinyl alcohol, polyethylene glycol, polypropylene glycol, and polyvinyl ether, corn starch, starch, gum arabic, pullulan, dextran, and the like. Natural polymer materials, semi-synthetic polymer materials such as dialdehyde starch, methylcellulose, and hydroxyethylcellulose. Among these, polyvinyl alcohol is particularly preferably used.

  More specifically, for example, 100 parts by weight of hydrotalcite is melted and kneaded using an extruder together with 5 to 100 parts by weight of a water-insoluble resin and 5 to 100 parts by weight of a water-soluble polymer, extruded as a strand, and cut. Then, the pellet is immersed in water, stirred and washed to dissolve the water-soluble polymer substance and extracted into water, so that the hydrotalcite is removed from the porous water-insoluble resin. The phosphorus removing agent according to the present invention can be obtained as a porous particulate molded product dispersed and fixed in a matrix.

  When the above pellets are immersed in water, stirred and mixed to extract the water-soluble polymer substance, the temperature of water may be in the range of room temperature to 95 ° C, preferably 50 to 90 ° C. It is a range. The time for stirring and mixing in water is usually 1 to 24 hours, preferably 2 to 10 hours, although it depends on the type of the water-soluble polymer used and the size of the pellets. However, it is not limited.

  In particular, according to the present invention, when hydrotalcite is melted, kneaded and extruded with a water-insoluble resin and a water-soluble polymer substance, the temperature is usually in the range of 140 to 200 ° C. Is preferred. In particular, the temperature is preferably in the range of 150 to 190 ° C.

  The shape and size of the phosphorus adsorbent according to the present invention are not particularly limited, but for convenience of handling, for example, from a pellet or particle having a diameter of 1 to 2 mm and a length of about 3 mm. Become.

  In the thus obtained phosphorus removing agent according to the present invention, the hydrotalcite is in the range of 1 to 95% by weight, the water-insoluble resin is in the range of 5 to 99% by weight, preferably the hydrotalcite. Is in the range of 50 to 95% by weight, and the water-insoluble resin is in the range of 5 to 50% by weight.

  As described above, the phosphorus removing agent according to the present invention captures and removes phosphate ions in water by ion exchange with anions between the metal hydroxide layers, so when the ion exchange capacity is saturated, for example, Washing hydrotalcites with an excessive amount of alkaline aqueous solution such as sodium carbonate, potassium carbonate, ammonium carbonate, etc., and exchanging phosphate ions with carbonate ions makes it possible to cope with phosphate ions. In addition, it can be recovered as sodium phosphate, potassium phosphate, ammonium phosphate, etc., and the phosphorus removal agent can be regenerated. Furthermore, if necessary, the carbonate ions can be exchanged for sulfate ions or chloride ions by treating with an aqueous sulfuric acid solution or hydrochloric acid.

  In order to capture and remove phosphorus dissolved in water using the phosphorus removal agent according to the present invention, for example, a container is filled with the phosphorus removal agent, and water is passed therethrough in an upward flow or a downward flow. do it. The raw water to be treated is usually contacted with the phosphorus remover according to the present invention in the range of 1 minute to 24 hours, and preferably in the range of 5 minutes to 1 hour.

  Using 1 part by weight of the phosphorus remover according to the present invention, 1 L of raw water containing 1000 ppm of phosphorus in terms of phosphate ions can be treated, and according to a preferred embodiment, 70% of phosphorus in the raw water can be removed, The raw water containing 5 ppm of phosphorus in terms of phosphate ions can be continuously treated to reduce the phosphorus concentration in the raw water to 0.1 to 0.5 ppm. Treatment of raw water containing 1 ppm of phosphorus in terms of phosphate ion by continuously setting the raw water treatment conditions, for example, the amount of phosphorus removal agent used in the raw water, the contact rate of the raw water with the phosphorus removal agent, etc. Thus, according to a preferred embodiment, the phosphorus concentration in the raw water can be reduced to 0.1 ppm.

  In this way, eutrophication of natural environmental water can be substantially prevented by removing phosphorus in the raw water to about 0.1 to 0.5 ppm.

  Thus, the phosphorus removing agent according to the present invention can be suitably used for removing phosphorus contained in natural water areas such as rivers, lakes, ponds, dam reservoirs, seas, and domestic wastewater.

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

Reference example 1
(Manufacture of hydrotalcite a)
Hydrothermal synthesis was performed by a conventionally known method. After completion of the hydrothermal reaction, the obtained hydrotalcites are surface-treated with stearic acid, then separated by filtration, dried and ground to give Mg _0.67 Al _0.33 (OH) ₂ (CO ₃ ) _0.165 · 0. A hydrotalcite having a composition of .48H ₂ O was obtained.

Reference example 2
(Manufacture of hydrotalcite b)
A mixed solution of magnesium chloride and aluminum chloride (Mg ²⁺ = 32.0 g / L, Al ³⁺ = 17.0 g / L) and 1 L of aqueous sodium hydroxide (150 g / L) in a 3 L beaker at the same time for 30 minutes It was dripped over. After completion of the dropwise addition, an aqueous sodium hydroxide solution was further added until pH 8 was reached. The slurry thus obtained was heated to 200 ° C. over 4 hours, held at this temperature for 4 hours, and then cooled to 90 ° C. Thereafter, the obtained hydrotalcites are separated by filtration, dried and pulverized, and then subjected to a dry surface treatment with sodium stearate to become Mg _0.7 Al _0.3 (OH) ₂ Cl _0.2 · 0.49H ₂ O. Hydrotalcites having a composition were obtained.

Reference example 3
(Manufacture of hydrotalcite c)
A mixed solution of magnesium sulfate and aluminum sulfate (Mg ²⁺ = 35.0 g / L, Al ³⁺ = 17.0 g / L) and 1 L of an aqueous sodium hydroxide solution (150 g / L) simultaneously in a 3 L beaker for 30 minutes It was dripped over. After completion of the dropwise addition, an aqueous sodium hydroxide solution was further added until pH 8 was reached. The slurry thus obtained was heated to 200 ° C. over 4 hours, held at this temperature for 4 hours, and then cooled to 90 ° C. Thereafter, the obtained hydrotalcites are separated by filtration, dried and pulverized, and then subjected to a dry surface treatment using sodium stearate to obtain Mg _0.7 Al _0.3 (OH) ₂ (SO ₄ ). Hydrotalcites having a composition of _0.15 · 0.48H ₂ O were obtained.

Reference example 4
(Manufacture of hydrotalcite d)
A mixed solution of magnesium chloride and aluminum sulfate (Mg ²⁺ = 32.0 g / L, Al ³⁺ = 17.0 g / L) and 1 L of aqueous sodium hydroxide (150 g / L) in a 3 L capacity beaker simultaneously for 30 minutes It was dripped over. After completion of the dropwise addition, an aqueous sodium hydroxide solution was further added until pH 8 was reached. The slurry thus obtained was heated to 200 ° C. over 4 hours, held at this temperature for 4 hours, and then cooled to 90 ° C. Thereafter, the obtained hydrotalcites are separated by filtration, dried and pulverized, and then subjected to a dry surface treatment using sodium stearate to obtain Mg _0.7 Al _0.3 (OH) ₂ Cl _0.06 (SO ₄ ) Hydrotalcites having a composition of _0.12 · 0.48H ₂ O were obtained.

Reference Example 5
(Manufacture of hydrotalcite e)
Hydrothermal synthesis was performed by a conventionally known method. After completion of the hydrothermal reaction, the obtained hydrotalcites are surface-treated with stearic acid, then separated by filtration, dried and ground, and then Mg _0.59 Zn _0.08 Al _0.33 (OH) ₂ Cl _0.06 (SO ₄ ) Hydrotalcite having a composition of _0.135 · 0.48H ₂ O was obtained.

Comparative Example 1
70 parts by weight of hydrotalcite b obtained in Reference Example 2 and 30 parts by weight of ethylene-vinyl acetate copolymer are mixed, put into an extruder, melted and kneaded at a temperature of 180 ° C., and the kneaded product is formed into pellets. This was designated as phosphorus removal agent B ′.

Example 1
(Production of phosphorus removing agents A to D)
Phosphorus removers A to D were produced using the hydrotalcites a to d obtained in Reference Examples 1 to 4, respectively. That is, 70 parts by weight of hydrotalcite, 24 parts by weight of ethylene-vinyl acetate copolymer and 6 parts by weight of water-soluble polyvinyl alcohol are mixed, put into an extruder, melted and kneaded at a temperature of 190 ° C. Molded into pellets. FIG. 1 shows a scanning electron micrograph (magnified 20000 times) of a cross section of the pellet which was rapidly frozen in liquid nitrogen and crushed. The cross section is flat and there are no voids.

  Next, the obtained pellets are poured into 85 ° C. warm water and stirred for 3 hours to dissolve and extract polyvinyl alcohol from the pellets, and then the pellets are separated by filtration and dried at 50 ° C. for 24 hours. D was obtained from phosphorus removers A to D. FIG. 2 shows a scanning electron micrograph (magnified 20000 times) of a cross section of the phosphorus remover A rapidly frozen in liquid nitrogen and crushed. The white string is an ethylene-vinyl acetate copolymer forming a porous matrix, and hydrotalcite particles are fixed in the matrix.

Example 2
(Production of phosphorus remover E)
60 parts by weight of hydrotalcites e obtained in Reference Example 5 above, 25 parts by weight of polylactic acid (“LACEA” H-100J F19, manufactured by Mitsui Chemicals, Inc.) and 15 parts by weight of water-soluble polyvinyl alcohol are mixed together in an extruder. It was charged, melted and kneaded at a temperature of 190 ° C., and formed into pellets. The obtained pellets are poured into warm water at 85 ° C. and stirred for 3 hours to dissolve and extract polyvinyl alcohol from the pellets. The pellets are separated by filtration and dried at 50 ° C. for 24 hours to remove phosphorus. Agent E was obtained.

Example 3
1 g or 0.1 g of the above phosphorus removal agent is added to 100 mL of raw water containing 1000 ppm of phosphorus in terms of phosphate ion (PO ₄ ³⁻ ). After stirring for 24 hours, the phosphorus removal agent is removed by filtration. Then, the phosphate ion concentration in the filtrate was measured to determine the phosphate ion removal rate. The phosphate ion removal rate R is defined as R = ((C when the phosphate ion concentration in the raw water is C ₀ and the phosphate ion concentration in the treated water after the raw water is treated with the phosphorus removal agent is C. ₀₋ C) / C ₀ ) × 100 (%). The results are shown in Table 1.

Example 4
The above phosphorus removing agent C500 mL is packed in a column having an inner diameter of 47 mm and a total length of 120 cm, and water containing 5 ppm of phosphorus in terms of phosphate ion (PO ₄ ³⁻ ) is continuously supplied from the lower end of the column at a rate of 42 mL / min. Then, the phosphorus concentration of the treated water from the upper end of the column was measured and found to be 0.1 ppm after 24 hours and 0.5 ppm after 30 days.

Example 5
In Example 4, except that the phosphorus removing agent D was used instead of the phosphorus removing agent C, the phosphorus concentration of the treated water from the top of the column was measured in the same manner. After 24 hours, it was 0.1 ppm. After 30 days, it was 0.5 ppm.

Example 6
In Example 4, except that the phosphorus removing agent E was used instead of the phosphorus removing agent C, the phosphorus concentration of the treated water from the upper end of the column was measured in the same manner. After 24 hours, it was 0.1 ppm. After 30 days, it was 0.5 ppm.

2 is a scanning electron micrograph (magnified 20000 times) showing the particle structure of particles (pellets) obtained in Example 1. FIG. 2 is a scanning electron micrograph (20000 times) showing the particle structure of the phosphorus remover of the present invention comprising porous particles obtained in Example 1. FIG.

Claims (2)

Formula (I)
^{_{M 2+ 1-x M 3+ x}} (OH -) 2 A n- x / n · mH 2 O ... (I)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from Mg ²⁺ , Zn ²⁺ and Cu ²⁺ , and M ³⁺ represents at least one selected from Al ³⁺ and Fe ^3+. A ⁿ⁻ represents at least one anion selected from SO ₄ ²⁻ , Cl ⁻ , CO ₃ ²⁻ and OH ⁻ , n represents the valence of the anion, and x represents (0 <x <0.5 and m is a number satisfying 0 ≦ m <2)
A remover of phosphorus dissolved in water, characterized in that the hydrotalcite represented by the formula comprises a molded product dispersed in a porous matrix made of a water-insoluble resin. Formula (I)
^{_{M 2+ 1-x M 3+ x}} (OH -) 2 A n- x / n · mH 2 O ... (I)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from Mg ²⁺ , Zn ²⁺ and Cu ²⁺ , and M ³⁺ represents at least one selected from Al ³⁺ and Fe ^3+. A ⁿ⁻ represents at least one anion selected from SO ₄ ²⁻ , Cl ⁻ , CO ₃ ²⁻ and OH ⁻ , n represents the valence of the anion, and x represents (0 <x <0.5 and m is a number satisfying 0 ≦ m <2)
The hydrotalcite represented by the formula is melted, kneaded and molded together with a water-insoluble resin and a water-soluble polymer substance, and then the water-soluble polymer substance resin is extracted with water to make the hydrotalcite porous. A method for producing a remover of phosphorus dissolved in water, characterized in that the molded article is fixed in a matrix made of a water-insoluble resin.