Selenium adsorbent, selenium adsorbent set, and selenium removal method

Abstract

To provide a selenium absorber, a selenium absorber set, and a selenium removal method, which enable absorption of selenium irrespective of pH and even when other anions are included.SOLUTION: A selenium absorber comprises a polymer gel which is a copolymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group and a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group. A selenium absorbent set comprises a first polymer gel which is a polymer of the tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group and a second polymer gel which is a polymer of the quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a selenium adsorbent, a selenium adsorbent set, and a method for removing selenium. [Background technology]

[0002] Many adsorbents and flocculants are known to remove heavy metals that contaminate soil and water (see, for example, Patent Documents 1-7). These adsorbents are anionic, taking advantage of the fact that many metal ions are cationic. Therefore, they cannot adsorb selenium, which does not exist in water as a single cation but is instead bound to oxygen and exists as an oxoacid.

[0003] Furthermore, when a cationic adsorbent capable of adsorbing oxoacid anions is used, the oxoacids cannot be adsorbed in the low pH range because they do not bond with hydrogen ions and are not ionized, whereas in the high pH range, hydroxide ions inhibit the adsorption of oxoacids.

[0004] Furthermore, when it is adsorbed onto a resin or the like, it has low selectivity with respect to other coexisting anions and is therefore difficult to adsorb. Therefore, it is reduced to selenious acid, which is more easily adsorbed, and then adsorbed and removed. However, even in this case, other anions tend to be adsorbed first, resulting in a decrease in the amount of selenious acid adsorbed.

[0005] In addition, selenate and selenious acid often coexist with other heavy metals, and while heavy metals are generally removed by coagulation and precipitation as hydroxides in alkaline solutions, they are ionized as selenium, acid, and selenious acid in alkaline solutions, making removal by coagulation and precipitation difficult. Furthermore, salts of oxoacids are highly soluble and lack suitable cations that can form insoluble salts. In particular, the high solubility of various salts of selenate makes removal by coagulation and precipitation difficult. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-323676 [Patent Document 2] Japanese Patent Application Publication No. 10-218611 [Patent Document 3] Japanese Patent Application Publication No. 10-310409 [Patent Document 4] Japanese Patent Application Publication No. 10-310410 [Patent Document 5] Japanese Patent Application Publication No. 10-310411 [Patent Document 6] Japanese Patent Application Publication No. 10-310412 [Patent Document 7] Japanese Patent Application Publication No. 11-207364 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a selenium adsorbent, a selenium adsorbent set, and a selenium removal method that can adsorb selenium regardless of pH and even when other anions are present. [Means for solving the problem]

[0008] The selenium adsorbent according to the first aspect of the present invention comprises: The present invention provides a polymer gel that is a copolymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group and a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group, Selenium-containing solutions and soils S It adsorbs both Se(IV) and Se(VI). It is characterized by:

[0009] The selenium adsorbent according to the second aspect of the present invention comprises: a first polymer gel which is a polymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group and a second polymer gel which is a polymer of a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group form an interpenetrating polymer network structure; Selenium-containing solutions and soils SIt adsorbs both Se(IV) and Se(VI). It is characterized by:

[0010] The tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group is represented by Formula 1, The quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group is preferably represented by formula 2. [ka] (In Formula 1 and Formula 2, R 1 each independently represents an optionally substituted alkyl group, R 2 represents an alkylene group, Z represents a polymerizable unsaturated group, n represents an integer of 0 or more, and in formula 2, X represents a halogen.

[0011] The polymerizable unsaturated group is preferably selected from the group consisting of an acryloyl group, a methacryl group, an acrylamide group, a methacrylamide group, a vinyl group, and an allyl group.

[0012] A selenium adsorbent set according to a third aspect of the present invention comprises: a first polymer gel which is a polymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group; a second polymer gel which is a polymer of a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group, Selenium-containing solutions and soils S It adsorbs both Se(IV) and Se(VI). It is characterized by:

[0013] The tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group is represented by Formula 1, The quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group is preferably represented by formula 2. [ka] (In Formula 1 and Formula 2, R 1 each independently represents an optionally substituted alkyl group, R2 represents an alkylene group, Z represents a polymerizable unsaturated group, n represents an integer of 0 or more, and in formula 2, X represents a halogen.

[0014] The polymerizable unsaturated group is preferably selected from the group consisting of an acryloyl group, a methacryl group, an acrylamide group, a methacrylamide group, a vinyl group, and an allyl group.

[0015] A method for removing selenium according to a fourth aspect of the present invention comprises: a selenium adsorbent according to the first aspect of the present invention, a selenium adsorbent according to the second aspect of the present invention, or a selenium adsorbent set according to the third aspect of the present invention is placed in a solution or soil containing selenium; the solution and the soil S Adsorbs both Se(IV) and Se(VI), It is characterized by: [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a selenium adsorbent, a selenium adsorbent set, and a selenium removal method that are capable of adsorbing selenium regardless of pH and even when other anions are present. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a graph showing the dissociation rate of selenious acid. [Figure 2] 1 is a graph showing the dissociation rate of selenate. [Figure 3] 1 is a graph showing the residual Se(IV) concentration in an aqueous sodium selenite solution in Experimental Example 1. [Figure 4] 1 is a graph showing the residual Se(VI) concentration of an aqueous sodium selenate solution in Experimental Example 1. [Figure 5] 1 is a graph showing the residual Se(IV) concentration in an aqueous sodium selenite solution in Experimental Example 2. [Figure 6] 1 is a graph showing the residual Se(VI) concentration of an aqueous sodium selenate solution in Experimental Example 2. [Figure 7] 1 is a graph showing the removal rates of Se(IV) and phosphate ions in Experimental Example 3. [Figure 8] 1 is a graph showing the adsorption amounts of Se(IV) and phosphate ions in Experimental Example 3. [Figure 9] 1 is a graph showing the removal rates of Se(VI) and phosphate ions in Experimental Example 3. [Figure 10] 1 is a graph showing the adsorption amounts of Se(VI) and phosphate ions in Experimental Example 3. [Figure 11] 10 is a graph showing the equilibrium adsorption amount of Se(IV) in Experimental Example 4. [Figure 12] 10 is a graph showing the equilibrium adsorption amount of Se(VI) in Experimental Example 5. [Figure 13] 10 is a graph showing the equilibrium adsorption amount of Se(VI) in Experimental Example 6. [Figure 14] 10 is a graph showing the equilibrium adsorption amount of Se(VI) in Experimental Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Selenium adsorbent) The selenium adsorbent according to the present embodiment comprises a polymer gel that is a copolymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group (hereinafter also simply referred to as a tertiary nitrogen atom-containing monomer) and a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group (hereinafter also simply referred to as a quaternary nitrogen atom-containing monomer). The polymerizable unsaturated group is not particularly limited as long as it is a radically reactive crosslinkable functional group.

[0020] The tertiary nitrogen atom-containing monomer is not limited as long as it has a polymerizable unsaturated group and a tertiary nitrogen atom in the compound, and the quaternary nitrogen atom-containing monomer is also not limited as long as it has a polymerizable unsaturated group and a quaternary nitrogen atom in the compound.

[0021] Examples of the tertiary nitrogen atom-containing monomer and the quaternary nitrogen atom-containing monomer include monomers represented by formula 1 and formula 2, respectively.

[0022] [ka]

[0023] In Formula 1 and Formula 2, R 1 Each independently represents an alkyl group which may be substituted, and the alkyl group preferably has 1 to 12 carbon atoms and may be linear, branched, or cyclic. Some of the hydrogen atoms in the alkyl group may be substituted with a substituent such as a phenyl group or a polymerizable unsaturated group as described below. In addition, in Formula 1 and Formula 2, R 2 represents an alkylene group, and n represents an integer of 0 or more, preferably 0 to 6. In Formula 1 and Formula 2, Z represents a polymerizable unsaturated group. The polymerizable unsaturated group is preferably an acryloyl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, or a vinyl group. In Formula 2, X represents a halogen, preferably chlorine, bromine, or iodine.

[0024] Tertiary nitrogen atom-containing monomers include N,N-dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N,N-diethylaminopropyl(meth)acrylamide, N,N-methylethylaminoethyl(meth)acrylamide, N,N-methylpropylaminoethyl(meth)acrylamide, N,N-methylpropylaminopropyl(meth)acrylamide, and N,N-dipropylaminopropyl(meth)acrylamide; acrylate, N,N-dialkylaminoalkyl (meth)acrylates such as N,N-methylethylaminopropyl (meth)acrylate, N,N-methylpropylaminopropyl (meth)acrylate, N,N-dipropylaminopropyl (meth)acrylate, N,N-dialkylacrylamides such as N,N-dimethylacrylamide, N,N-diethylacrylamide, N-methyl-N-ethylacrylamide, N-methyl-N-isopropylacrylamide, N-methyl-Nn-propylacrylamide, N,N-dialkylaminoalkyl acrylamides such as N,N-dimethylaminoethylacrylamide, N,N-dialkylaminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate, N,N-dialkyl (meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-dialkyldiallylamines such as N,N-dimethylallylamine and N,N-diethylallylamine, and alkyldiallylamines such as methyldiallylamine.

[0025] Examples of the quaternary nitrogen atom-containing monomer include monomers obtained by subjecting the above-mentioned tertiary nitrogen atom-containing monomer to a quaternization reaction with a quaternizing agent (e.g., alkyl halide, dialkyl sulfate, dialkyl carbonate, alkyl sulfonate, benzenesulfonate, p-toluenesulfonate, tetraphenylborate, thiocyanate) in water or an organic solvent.

[0026] The polymer gel can be obtained by polymerizing the above-mentioned tertiary nitrogen atom-containing monomer and quaternary nitrogen atom-containing monomer according to a conventional method.

[0027] The selenium adsorbent may contain other components in addition to the polymer gel. The other components may be copolymerized in the polymer gel. For example, the polymer gel may be polymerized not only with the above-mentioned monomer but also with a crosslinking agent, and contain the crosslinking agent component. Alternatively, the selenium adsorbent may include the polymer gel and another polymer.

[0028] The crosslinking agent is not particularly limited as long as it has a polymerizable unsaturated group, and examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl acrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl ... (meth)acrylic acid alkyl esters such as ethyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate; primary hydroxyl group-containing (meth)acrylic monomers such as hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; 2-hydroxypropyl methacrylate; (meth)acrylic monomers containing a secondary hydroxyl group, such as 2-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy 3-phenoxypropyl (meth)acrylate, 3-chloro 2-hydroxypropyl (meth)acrylate, and 2-hydroxy 3-phenoxypropyl (meth)acrylate, N-isopropylacrylamide, Nn-propylacrylamide, Nn-propylmethacrylamide, N-methylacrylamide, N-ethylmethacrylamide, N-cyclopropylmethacrylamide, and N-cyclopropylacrylamide N-substituted (meth)acrylamides such as N-acryloylpiperidine, N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-hydroxypropyl (meth)acrylamide, and (meth)acryloylmorpholine, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and dipropylene glycol di(meth)acrylate,Bifunctional monomers such as polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, propylene oxide-modified bisphenol A di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol ethylene oxide-modified di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate, isocyanuric acid ethylene oxide-modified diacrylate, and 2-(meth)acryloyloxyethyl acid phosphate diester, pentaerythritol tri( Examples of the trifunctional or higher functional monomer include tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly(meth)acrylate, ethylene oxide-modified isocyanuric acid tri(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, and succinic acid-modified pentaerythritol tri(meth)acrylate.

[0029] The selenium adsorbent may also have an interpenetrating polymer network (IPN) structure formed by a first polymer gel, which is a polymer of a tertiary nitrogen atom-containing monomer, and a second polymer gel, which is a polymer of a quaternary nitrogen atom-containing monomer. A selenium adsorbent having an IPN structure can be obtained, for example, as follows: A tertiary nitrogen atom-containing monomer is polymerized according to a conventional method to obtain a first polymer gel. The dried first polymer gel is immersed in a monomer solution of a quaternary nitrogen atom-containing monomer to swell the first polymer gel. The quaternary nitrogen atom-containing monomer is then polymerized to form a second polymer gel, resulting in a selenium adsorbent having an IPN structure formed by the first and second polymer gels.

[0030] (Selenium adsorbent set) The selenium adsorbent set includes a first polymer gel that is a polymer of a tertiary nitrogen atom-containing monomer and a second polymer gel that is a polymer of a quaternary nitrogen atom-containing monomer. The tertiary nitrogen atom-containing monomer and the quaternary nitrogen atom-containing monomer are the same as those described above.

[0031] The first polymer gel and the second polymer gel are obtained by polymerizing a tertiary nitrogen atom-containing monomer and a quaternary nitrogen atom-containing monomer, respectively, according to a conventional method, and may be polymerized using the above-mentioned crosslinking agent.

[0032] There are no limitations on the blending ratio of the first polymer gel to the second polymer gel, but it is 1:9 to 9:1 by weight, preferably 4:6 to 6:4, and more preferably 5:5.

[0033] The selenium adsorbent set may contain other components. The first polymer gel and the second polymer gel may be polymers containing other components in addition to the tertiary nitrogen atom-containing monomer and the quaternary nitrogen atom-containing monomer, respectively.

[0034] (Explanation of selenium removal method) The selenium removal method involves placing the above-mentioned selenium adsorbent in a selenium-containing solution or soil. The selenium adsorbent adsorbs the selenium in the solution or soil, and the selenium in the solution or soil can be removed by separating the selenium-adsorbed selenium adsorbent from the solution or soil.

[0035] Selenium is used in various industrial manufacturing fields, such as semiconductor materials, battery materials, photoconductors for copying machines, rectifiers, and electrolytic colorants for metals such as aluminum. The selenium adsorbent can be used to remove, separate, and recover selenium from wastewater discharged from these manufacturing processes. Furthermore, since selenium is an essential trace element for animals but is also a highly toxic environmental pollutant, it can also be used to remove selenium from selenium-contaminated soil by interposing it in the soil.

[0036] Selenium is insoluble in water and generally exists in solution as SeO3 2- (Se(IV)), SeO4 2- Se(IV) exists in the form of H2SeO3, HSeO3-, and SeO3, depending on the pH, as shown in Figure 1. 2- As shown in Figure 2, Se(VI) takes the form of H2SeO4 or HSeO4 depending on the pH. - , SeO4 2- It takes the form of:

[0037] The selenium adsorbent is capable of adsorbing and removing both Se(IV) and Se(VI), which can take various forms depending on the pH, regardless of the pH.

[0038] Tertiary amines exhibit a property that their adsorption ability to Se(IV) decreases in the pH range above pH 3, but increases in the low pH range below pH 3. This is thought to be because, in the low pH range, protonation of tertiary amines ionizes H2SeO3, allowing adsorption. On the other hand, quaternary amines exhibit a property that their adsorption ability to Se(IV) decreases in the low pH range, but increases in the pH range above pH 3.

[0039] Furthermore, tertiary amines have high adsorption properties for Se(VI) in the pH range below pH 3, and the adsorption properties decrease as the pH increases. On the other hand, quaternary amines have the property of showing high adsorption properties for Se(IV) in all pH ranges.

[0040] The selenium adsorbent comprises a polymer gel that is a copolymer of a tertiary nitrogen atom-containing monomer and a quaternary nitrogen atom-containing monomer, and has a structure that contains tertiary amines and quaternary amines. This compensates for the areas where the adsorption strength decreases depending on the pH, and therefore can adsorb both Se(IV) and Se(VI) regardless of the pH.

[0041] Furthermore, although the reason is unclear, the selenium adsorbent is able to adsorb and remove selenium even when other anions, such as phosphate ions, sulfate ions, and bicarbonate ions, are present in the solution.

[0042] The selenium adsorbent set described above may be placed in a solution or soil containing selenium. The selenium adsorbent set includes a first polymer gel that is a polymer of a tertiary nitrogen atom-containing monomer and a second polymer gel that is a polymer of a quaternary nitrogen atom-containing monomer, and therefore exhibits the same effects as the selenium adsorbent described above. [Example]

[0043] (Synthesis of selenium adsorbent) A monomer, a crosslinking agent, a polymerization accelerator, and distilled water were placed in a measuring flask and mixed to prepare a polymerization solution. In a separate volumetric flask, initiator and water were mixed to prepare an initiator solution. The polymerization solution and the initiator solution were aerated with nitrogen at room temperature for 1 hour, then mixed under a nitrogen atmosphere, poured into a polypropylene tube, and sealed with parafilm. The polypropylene tube was kept in a constant temperature water bath at 7°C for 4 hours to carry out polymerization, thereby obtaining a selenium adsorbent.

[0044] The monomer, crosslinking agent, polymerization accelerator, and initiator are shown in Table 1. Selenium adsorbent 1 having a tertiary amine was obtained by using N,N-dimethylaminopropylacrylamide having a tertiary amine as the monomer. Furthermore, by using N,N-dimethylaminopropylacrylamide methyl chloride quaternary salt having a quaternary amine as a monomer, a selenium adsorbent 2 having a quaternary amine was obtained. Furthermore, by using N,N-dimethylaminopropylacrylamide and N,N-dimethylaminopropylacrylamide methyl chloride quaternary salt as monomers, a selenium adsorbent 3 having a tertiary amine and a quaternary amine was obtained. Using these selenium adsorbents 1-3, the following experiments were carried out.

[0045] [Table 1]

[0046] (Experiment 1) Selenium adsorption experiment using selenium adsorbent 1 and selenium adsorbent 2 Sodium selenite (Na2SeO3) was added to water to prepare a sodium selenite aqueous solution (initial concentration 30 ppm). Furthermore, a pH adjuster (HCl) was added to prepare various sodium selenite aqueous solutions with different pH values. The following selenium adsorbent (0.1 g) was added to each aqueous solution of sodium selenite (10 mL), and the concentration of Se(IV) remaining in the aqueous solution after 48 hours was measured.

[0047] In addition, various aqueous sodium selenate solutions (initial concentration 30 ppm) with different pH values ​​were prepared in the same manner as above, except that sodium selenate (NaSeO) was used instead of sodium selenite. The following selenium adsorbents were added to the aqueous sodium selenate solutions in the same manner as above, and the Se(VI) concentration remaining in the solutions was measured after 48 hours.

[0048] The selenium adsorbents used were as follows: Selenium adsorbent 1 Selenium adsorbent 2 Commercially available selenium adsorbent 1 (Magical Fix (MFX) (registered trademark): manufactured by Sumitomo Osaka Cement Co., Ltd.) Commercially available selenium adsorbent 2 (NLDH (registered trademark): manufactured by Japan Land Development Co., Ltd.)

[0049] The experimental results using each selenium adsorbent are shown in Figure 3 for the residual Se(IV) concentration in the sodium selenite aqueous solution, and Figure 4 for the Se(VI) concentration in the sodium selenate aqueous solution.

[0050] The lower the pH, the better the adsorption capacity of selenium adsorbent 1 for Se(IV) and Se(VI). It is presumed that the lower the pH, the more the amino groups of selenium adsorb hydrogen from selenic acid and selenious acid, causing ionization, and the greater the ability to adsorb the oxo acid ions from which hydrogen has been extracted. In addition, selenium adsorbent 2 had a high adsorption capacity for Se(VI) regardless of the pH. However, at low pH, the adsorption capacity for Se(IV) decreased.

[0051] (Experiment 2) Selenium adsorption experiment using selenium adsorbents 1-3 and the adsorbent set As in Experiment 1, various aqueous sodium selenite solutions (initial concentration 27 ppm) and aqueous sodium selenate solutions (initial concentration 30 ppm) with different pH values ​​were prepared. The following selenium adsorbents were added to each aqueous solution (10 mL), and the residual Se concentration in the aqueous solution after 42 hours was measured.

[0052] The selenium adsorbents used and the amounts added were as follows: Selenium adsorbent 1 (0.1g) Selenium adsorbent 2 (0.1g) Selenium adsorbent 3 (0.1g) Selenium adsorbent set (Selenium adsorbent 1 (0.05g) + Selenium adsorbent 2 (0.05g))

[0053] The residual Se(IV) concentration in sodium selenite aqueous solution is shown in Figure 5, and the residual Se(VI) concentration in sodium selenate aqueous solution is shown in Figure 6. When selenium adsorbent 3 was added, the adsorption capacity for both Se(IV) and Se(VI) was high regardless of the pH of the aqueous solution. Furthermore, when selenium adsorbent set was added, similar to selenium adsorbent 3, high adsorption capacity for both Se(IV) and Se(VI) was also shown regardless of the pH. While selenium adsorbents 1 and 2 have a range in which the adsorption amount decreases depending on the pH, selenium adsorbent 3 and adsorbent set compensate for this and were found to be able to remove selenium regardless of the pH.

[0054] (Experiment 3) Verification experiment of the effects of other coexisting anions We verified whether the selenium adsorbent can adsorb selenium even in the presence of other anions.

[0055] A mixed aqueous solution containing Se(IV) was prepared by adding thorium selenite (Na2SeO3), potassium phosphate (K3PO4), sodium bicarbonate (NaHCO3), and sodium sulfate (Na2SO4) to water and adjusting the pH to neutral with a pH adjuster (hydrochloric acid).

[0056] In addition, sodium selenate (Na2SeO4), potassium phosphate (K3PO4), sodium bicarbonate (NaHCO3), and sodium sulfate (Na2SO4) were added to water, and the pH was adjusted to neutral with a pH adjuster (hydrochloric acid) to prepare a Se(VI)-containing mixed aqueous solution.

[0057] Table 2 shows the initial element concentrations of Se, P, C, and S in the prepared Se(IV)-containing mixed aqueous solution and Se(VI)-containing mixed aqueous solution, as well as the pH.

[0058] [Table 2]

[0059] The following selenium adsorbent (0.1 g) was added to each Se(IV)-containing mixed aqueous solution (10 mL) and stirred for 48 hours. After centrifugation, the supernatant was filtered through a 0.22 μm filter, and the removal rate and adsorption amount of Se(IV) and phosphate ion in each Se(IV)-containing mixed aqueous solution were measured.

[0060] The selenium adsorbents used are shown below. Selenium adsorbent 3 Commercially available selenium adsorbent 3 (Mine Ace (registered trademark) FMAA: manufactured by Nippon Steel Cement Co., Ltd.) Commercially available selenium adsorbent 4 (Lock Ace (registered trademark) SF21: manufactured by Nippon Steel Cement Co., Ltd.) Commercially available selenium adsorbent 5 (Rock Ace (registered trademark) MSM: manufactured by Nippon Steel Cement Co., Ltd.)

[0061] The results of the removal rates and adsorption amounts of Se(IV) and phosphate ions are shown in Figures 7 and 8. Commercial selenium adsorbents 3 to 5 had high removal rates of phosphate ions, but low removal rates of Se(IV), approximately 20% or less. On the other hand, the removal rate of Se(IV) for selenium adsorbent 3 exceeded 50%, which was significantly higher than that for commercial selenium adsorbents 3 to 5. Furthermore, because the initial concentrations of Se(IV) and P in the aqueous solution were different, the amount of phosphate ions adsorbed was greater than the amount of Se(IV) adsorbed for all adsorbents.

[0062] Commercial selenium adsorbents 3 to 5 adsorb phosphate ions more easily than Se(IV), and when the concentration of coexisting phosphate ions was high, they adsorbed phosphate ions first, presumably preventing them from adsorbing Se(IV). Note that commercial selenium adsorbents 3 and 5 are hydrotalcite-based adsorbents that adsorb phosphate ions more easily than Se(IV), and commercial selenium adsorbent 4 is a schwertmannite-based adsorbent that adsorbs anions by substitution with sulfuric acid. Therefore, when sulfuric acid coexists, the substitution reaction is less likely to occur, resulting in a low adsorption amount.

[0063] Next, to the Se(VI)-containing mixed aqueous solution (10 mL), selenium adsorbent 3 and commercially available selenium adsorbents 3 to 5 (0.1 g) were added in the same manner as above, and the mixture was stirred for 48 hours. The removal rate and adsorption amount of Se(VI) and phosphate ions in each Se(VI)-containing mixed aqueous solution were measured.

[0064] The results of the removal rate and adsorption amount of Se(VI) and phosphate ions are shown in Figures 9 and 10. When commercial selenium adsorbents 3 to 5 were added, the removal rate and adsorption amount of phosphate ions were similar, but Se(VI) was not removed at all. On the other hand, with selenium adsorbent 3, the removal rate of Se(VI) exceeded 80%, indicating that Se(VI) can also be adsorbed and removed.

[0065] As described above, it has been demonstrated that the selenium adsorbent 3 can adsorb both Se(IV) and Se(VI) even when other anions such as phosphate ions, sulfate ions, and bicarbonate ions are present in the aqueous solution.

[0066] Various selenium adsorbents were synthesized and subjected to the following experiments. Selenium adsorbents 4-6 were synthesized using the same procedure as for the synthesis of selenium adsorbents 1-3 described above. The monomers, crosslinkers, polymerization accelerators, and initiators used in the synthesis of selenium adsorbents 4-6 are shown in Table 3.

[0067] [Table 3]

[0068] Furthermore, a selenium adsorbent 7 having an interpenetrating polymer network structure was synthesized as follows. N,N-dimethylaminopropylacrylamide methyl chloride quaternary salt (500 mol / m 3 ), and methylenebisacrylamide (50 mol / m 3 ), and tetramethylethylenediamine (20 mol / m 3 ), and ammonium persulfate (20 mol / m 3) was dissolved and mixed in 25 ml of distilled water, and after nitrogen aeration, polymerization was carried out at 25°C for 4 hours to synthesize a polymer gel. This polymer gel was washed with methanol and dried at room temperature. 2.0 g of this dried polymer gel was dissolved in N,N-dimethylaminopropylacrylamide (500 mol / m 3 ), and methylenebisacrylamide (50 mol / m 3 ), and tetramethylethylenediamine (20 mol / m 3 The substrate was immersed in a monomer solution prepared by dissolving 100g of ammonium persulfate (20 mol / m) in 25 ml of distilled water, and the substrate was allowed to swell. 3 ) was added, and selenium adsorbent 7 with an interpenetrating polymer network structure was obtained by radical polymerization.

[0069] In addition, a mixture of a cationic ion exchange resin (cation exchange resin (PK302: manufactured by Mitsubishi Chemical Corporation)) and an anionic ion exchange resin (strongly basic anion exchange resin (PA312: manufactured by Mitsubishi Chemical Corporation)) (hereinafter referred to as commercial ion exchange resin 1) was prepared.

[0070] (Experiment 4) Selenious acid adsorption experiment 0.04 g of each adsorbent (selenium adsorbents 11-14 and commercial ion exchange resin 1) was immersed in a sodium selenite solution (20 mg / L, 40 mL, pH 6), and the concentration of the solution was measured after 24 hours. The amount of adsorption onto each adsorbent was calculated using the following formula A. q e =(C0-C e ) / m...(Formula A) (q e : Equilibrium adsorption amount (mg / g-dry gel), C e : equilibrium concentration (mg / L), C0: initial concentration (mg / L), m: adsorbent dry weight

[0071] The results are shown in Figure 11. All adsorbents were able to adsorb the anion selenious acid. The reason why the adsorption amount of commercial ion exchange resin 1 was low is because selenate, an anion, could only be adsorbed by anionic ion exchange resins.

[0072] (Experiment 5) Selenate adsorption experiment 0.04 g of each adsorbent (selenium adsorbents 11-14 and commercial ion exchange resin 1) was immersed in a sodium selenate solution (10 mg / L, 40 mL, pH 6), and the solution concentration was measured after 24 hours. The adsorption amount of each adsorbent was then calculated using the above formula A.

[0073] The results are shown in Figure 12. All adsorbents were able to adsorb selenium, an anion. The adsorption amount of commercial ion exchange resin 1 was low because selenium, an anion, is less likely to ionize than selenious acid, and it could only be adsorbed by anionic ion exchange resins. The adsorption amount of commercial ion exchange resin 1 was lower than that of selenious acid in Experiment 4 because the initial concentration of the solution was low.

[0074] (Experiment 6) Verification of the effect of copolymerization Various selenium adsorbents were added to selenic acid aqueous solutions (initial concentration 10 mg / L, 50 mL) with different initial pH values, and selenic acid adsorption was carried out at 25°C for 48 hours with a shaking speed of 120 rpm. The amount of selenic acid adsorbed onto each selenium adsorbent was calculated using the above formula A, and the effect of initial pH was examined.

[0075] The selenium adsorbents used are shown below. Selenium adsorbent 3 (3 mg) Selenium adsorbent set (Selenium adsorbent 1 (1.5 mg) + Selenium adsorbent 2 (1.5 mg)) Selenium adsorbent 8 (3 mg) Cationic monomer, anionic monomer copolymer gel

[0076] The selenium adsorbent 8 contains N-(2-acryloyloxyethyl)-N-benzyl-N,N-dimethylammonium chloride and 2-acrylamido-2-methylpropanesulfonic acid as monomers, each at 500 mol / m 3 This copolymer was synthesized in the same manner as in the above-mentioned selenium adsorbent 1-3, except that each copolymer was used separately.

[0077] The results are shown in Figure 13. Selenium adsorbent 3, which was copolymerized with a tertiary nitrogen atom-containing monomer and a quaternary nitrogen atom-containing monomer, was able to adsorb selenate at pH 2 or higher. The adsorption amount decreased as the pH decreased because selenate dissociation was suppressed at pH 3 or lower. Selenium adsorbent 1 and selenium adsorbent 2 were also able to adsorb selenate when mixed in equal amounts without copolymerization, but the adsorption amount was about half that of copolymerized selenium adsorbent 3. The reason why the adsorption ability of selenate appears to be lower than in Experiment 2 is because the amount of selenium adsorbent added in Experiment 6 was much smaller than in Experiment 2. Furthermore, almost no adsorption occurred with selenium adsorbent 8. This is because the anionic sulfonic acid groups bonded to the cationic quaternary amino groups, making it impossible to adsorb selenate ions in the solution, and because H dissociated from the sulfonic acid groups. + This is thought to be because the pH of the solution was lowered and the dissociation of selenate was also suppressed.

[0078] (Experiment 7) Comparison with ion exchange resin Various selenium adsorbents and ion exchange resins were added to selenic acid aqueous solutions (initial concentration 10 mg / L, 50 mL) with different initial pH values, and the selenic acid was adsorbed at 25°C for 48 hours with a shaking speed of 120 rpm. The amount of selenic acid adsorbed onto each selenium adsorbent and ion exchange resin was calculated using Equation A above, and the effect of initial pH was examined.

[0079] The selenium adsorbents used were as follows: Selenium adsorbent 1 Selenium adsorbent 2 Selenium adsorbent 3 Commercially available ion exchange resin 2 (weakly acidic cation exchange resin: WK-10: manufactured by Mitsubishi Chemical Corporation) Commercially available ion exchange resin 3 (weakly basic anion exchange resin: WA-40L: manufactured by Mitsubishi Chemical Corporation)

[0080] The results are shown in Figure 14. The weakly acidic cation exchange resin was unable to adsorb selenate, which is an anion. The weakly basic anion exchange resin also adsorbed a small amount of selenate at low pH, but as the pH increased, it became difficult for the selenate to dissociate, and so it was unable to adsorb selenate.

[0081] In contrast, selenium adsorbent 2, which has a strong basic anion exchange capacity, showed high selenate adsorption capacity in the pH range above 2. The reason why the adsorption capacity drops dramatically at pH 2 is because the dissociation of selenate is suppressed at low pH, making it difficult to ionize.

[0082] Furthermore, although selenium adsorbent 1 has a lower adsorption capacity than selenium adsorbent 2 in the weakly acidic to neutral range, its adsorption power does not decrease significantly even at pH 2. This is thought to be because the protonation of the tertiary amino group of selenium adsorbent 1 promotes the dissociation of selenic acid even at low pH.

[0083] Furthermore, selenium adsorbent 3 showed an adsorption amount intermediate between selenium adsorbent 1 and selenium adsorbent 2. This is thought to be because the other copolymerized component compensated for the decrease in adsorption amount when each component was used alone.

[0084] From the above, it was shown that a gel-type selenium adsorbent copolymerized with a monomer having a tertiary amino group and a monomer having a quaternary amino group can adsorb selenate over a wide pH range, even though dissociation is suppressed at low pH and adsorption is difficult using ion exchange resins. [Industrial Applicability]

[0085] The selenium adsorbent can adsorb both Se(IV) and Se(VI) regardless of pH and even in the presence of other anions, so it can be used to remove selenium from various industrial wastewaters that use selenium and to improve selenium-contaminated soil.

Claims

1. The present invention comprises a polymer gel which is a copolymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group and a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group, Adsorbs both Se(IV) and Se(VI) from selenium-containing solutions and soils; A selenium adsorbent characterized by:

2. a first polymer gel which is a polymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group and a second polymer gel which is a polymer of a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group form an interpenetrating polymer network structure; Adsorbs both Se(IV) and Se(VI) from selenium-containing solutions and soils; A selenium adsorbent characterized by:

3. The tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group is represented by Formula 1, The quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group is represented by Formula 2: 【Chemistry 1】 (In Formula 1 and Formula 2, R １ each independently represents an optionally substituted alkyl group, R ２ represents an alkylene group, Z represents a polymerizable unsaturated group, n represents an integer of 0 or more, and in formula 2, X represents a halogen. The selenium adsorbent according to claim 1 or 2.

4. the polymerizable unsaturated group is selected from the group consisting of an acryloyl group, a methacryl group, an acrylamide group, a methacrylamide group, a vinyl group, and an allyl group; The selenium adsorbent according to any one of claims 1 to 3.

5. a first polymer gel which is a polymer of a tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group; a second polymer gel which is a polymer of a quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group, Adsorbs both Se(IV) and Se(VI) from selenium-containing solutions and soils; A selenium adsorbent set characterized by:

6. The tertiary nitrogen atom-containing monomer having a polymerizable unsaturated group is represented by Formula 1, The quaternary nitrogen atom-containing monomer having a polymerizable unsaturated group is represented by Formula 2: 【Chemistry 2】 (In Formula 1 and Formula 2, R １ each independently represents an optionally substituted alkyl group, R ２ represents an alkylene group, Z represents a polymerizable unsaturated group, n represents an integer of 0 or more, and in formula 2, X represents a halogen. The selenium adsorbent set according to claim 5 .

7. the polymerizable unsaturated group is selected from the group consisting of an acryloyl group, a methacryl group, an acrylamide group, a methacrylamide group, a vinyl group, and an allyl group; 7. The selenium adsorbent set according to claim 5 or 6.

8. A method for producing a selenium-containing solution or soil comprising the steps of: providing the selenium adsorbent according to any one of claims 1 to 4; or providing the selenium adsorbent set according to any one of claims 5 to 7 in the solution or soil containing selenium; Adsorbing both Se(IV) and Se(VI) from the solution and the soil; A method for removing selenium.

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