JPS5864180A - Removal of arsenic in aqueous solution - Google Patents

Abstract

PURPOSE:To facilitate efficient removal of arsenic dissolved in an aqueous solution, by bringing an aqueous arsenic-contg. solution into contact with a chelating resin having a chelate-forming group represented by a specified formula. CONSTITUTION:An aqueous trivalent arsenic-contg. solution is brought into contact with a chelating resin having a chelate-forming group represented by formulaI(wherein R is H or a 1-5C alkyl group and n is an integer of 1-6) to remove the trivalent arsenic in the aqueous solution. The chelating resin having the chelate-forming group represented by formulaIis a phenolic resin having the chelate-forming group of formulaIin its phenolic nucleus. Said phenolic resin is prepared, for instance, by resinifying a phenolic compound such as N-methyl- N-(2-hydroxyphenylmethyl)-D-glucamine, with another phenolic compound, a kind of phenols and an aldehyde by a polycondensing reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing arsenic from an aqueous solution using a chelate resin having an aminopolyalcohol group.

Arsenic is contained in wastewater from the non-ferrous metal smelting industry as well as other pharmaceuticals, agricultural chemicals, and pigment industries, as well as in thermal wastewater from geothermal power plants. Regarding the toxicity of arsenic, especially trivalent arsenic.

It has been known for a long time, but in recent years, the carcinogenicity of arsenic has been recognized, and its presence has been reduced to 0.5ppP by wastewater standards and 0.5pP by environmental standards. O2 is regulated to a low level of 5ppm or less. Several methods are known to date for treating wastewater containing arsenic, among which a coagulation method using metal hydroxides such as hydricium, magnesium, barium, iron, and aluminum is known. The starch method is widely used because it can reduce residual arsenic to below wastewater standards through relatively simple treatment operations. However, this method is typified by hot water from geothermal power plants. When treating a large amount of wastewater containing low concentrations of arsenic, it is necessary to use a large amount of chemicals, and there are also problems in processing the large amount of arsenic-containing waste generated at this time. As an alternative to such a metal hydroxide coprecipitation method, the activity, active μmina, Vlikageμ, red mud, manganese dioxide, titanium-
Adsorption method using activity composite adsorbent, Shirasu particles supporting diμconium oxide, iron (1) or zirconium (F
) Ligand ion exchange method using compatible cation exchange resin,
Ion exchange methods using anion exchange resins are being considered. However, methods using these adsorbents or ion exchange resins have a small adsorption capacity for hypo, especially harmful trivalent arsenic, and are insufficient in 9 selectivity. Furthermore, regeneration is complicated and durability is poor. So, 5I! It's not useful.

On the other hand, as for the method of using chelate resin.

A method has been proposed in which the arsenic anion is removed by a ligand exchange method after adsorbing pentavalent iron or zirconium, but these methods have a low adsorption capacity. Because it is small and the adsorption rate is extremely slow, it is not suitable for treating large amounts of wastewater containing low concentrations of arsenic.In addition, the regeneration method is complicated and usually requires regeneration treatment with a strong acid. , iron or zirconium elutes with arsenic, and there is a problem in processing the sulphate generated at this time, and when reusing it, it is necessary to adsorb iron or e) pvconicum again, so it is not suitable for 5JI. However, it was difficult to remove arsenic efficiently.

In view of these circumstances, the inventors of the present invention conducted extensive research with the aim of providing a method for efficiently removing elements dissolved in an aqueous solution, and found that when a chelate resin having an aminopolyalcohol group is used, find that the purpose of is achieved.

We have arrived at the present invention.

That is, 5 the present invention provides a method for removing carbon in an aqueous solution by bringing a chelate-forming group represented by formula (I) into contact with an arsenic-containing aqueous solution. This is a method for removing arsenic.

The chelate resin used in the present invention may be any three-dimensionally crosslinked resin, but it must have a group represented by formula (I) as a chelate forming group. The formula (R of Il is particularly a methyl group, ethyl ρ
A group is preferable, and n is preferably a group.

4 is preferable, and as the m fat base, styrene/divinybenzene copolymer, phenol-formalin resin, epoxy resin, etc. are preferable. As a preferable specific example of these resins, Amberphyto IRA-743
(Styrene-divinylbenzene copolymer, manufactured by Rohm and Haas).

Examples include phenol resins having a chelate-forming group of formula (I) in the pheno-μ nucleus (Japanese Patent Application No. 81475/1982).

To prepare a pheno-μ tree with a chelating group of formula (Il) on this pheno-μ nucleus, for example, N-methyl-
It may be produced by polycondensation reaction of a phenol compound such as N-(2-ni-dorokiVphenimethyl)-D-gukamine, a phenol compound, phenols, and aldehydes into a resin.

First, in the first step, a pheno compound and an aldehyde are reacted. At that time, aldehydes are pheno-μ
7 ratio of 0.2:1 to 2.0:1 to the compound
, preferably in a ratio of 0.8:1 to 1.5 to 1, then add a polymerization catalyst and heat and stir at 20 to 90°C for 1 to 6 hours, preferably at 50 to 80°C for 2 to 4 hours. 0 to do
Then, as a second step, the reaction obtained in the first step,
Phenols are added to the product and reacted. At that time, the ratio of phenol to pheno-μ compound is 0.7μ.
1-9.0:1. Preferably 0.3:1 to 5.0
: 117) and heated and stirred at 25 to 95 °C for 1 to 6 hours, preferably at 50 to 90 °C for 2 to 4 hours.

Furthermore, in the S step, aldehydes are added to the reaction product obtained in the second step and reacted. At that time, the ratio of aldehydes to pheno compounds is 7 to 1.0:
1-6.0:1. Preferably 2.0:1 to 5.0
: It is possible to easily produce a cross-linked three-dimensional chelate resin by adding it at a ratio of 1 part, molding it into the shape of @, and then heating it to 60 to 150 m, preferably 90 to 1'50°C. .

Of course, by using a method completely similar to the conventionally known method for producing small spherical chelate resins, by performing bar-N polycondensation in an organic solvent that is immiscible with water.

Granulation and three-dimensional crosslinking can be performed simultaneously to form small spherical chelate resins.

Next, to remove arsenic from an aqueous solution using the above chelate resin, the patch method and cuff method are used in the same way as the normal ion exchange method. preferable. Also.

The contact time with the arsenic-containing solution is determined by the amount of chelate resin used, the composition 1 of the arsenic concentration of the liquid to be treated, and the pH.

Although it varies depending on the speed of liquid passage into the cuff, etc., when using 50sZ resin, the time is 30 seconds to 5 hours, preferably 1 minute to 6 hours.
Used in the range of 0 minutes. j! The contact temperature between the arsenic-containing aqueous solution and the chelate resin is 5 to 100°C, preferably 15 to 80'C. For example, an arsenite-containing aqueous solution (18Q
I), 200t/l, NtbCl, 5. B9/1
．． When PH-8-5) is passed through at a rate of 250 m per hour, the arsenic leakage concentration remains 0.5”f/20 hours later.
It is kept below l.

Next, when the adsorption of arsenic reaches saturation, 7μ of 4 to 1096
Arsenic can be removed from the resin by treatment with an aqueous potassium solution. As the alkaline aqueous solution, alkali metal hydroxides such as caustic soda, caustic potash, and lithium hydroxide are used, and caustic soda is particularly preferred. After eluting arsenic, the sample is washed with 100 to 10 d of water. Even when the resin is regenerated by such a method, no decrease in arsenic adsorption ability or persistence is observed.

According to the present invention, arsenic in an aqueous solution is trivalent or pentavalent.
It is well known that arsenic is dissolved in a valent state, but in particular, arsenic in a trivalent state such as subacid and *sodium arsenate can be efficiently removed. The reason for this is not clear, but the dissociation constant of arsenic acid (PKI -2-19, 'PK
This is thought to be due to the difference in the dissociation constant between subacid (PKz-6-94, PKa=13-5) and PH1-10. Preferably PH
It efficiently adsorbs trivalent arsenic in the range of 4 to 10.

This trivalent arsenic in the PH region is arsenite (Hs As Os
) or arsenite ion (HmAB (%-)), and the group represented by formula 1 (Il) is considered to have an excellent ability to form a complex with undissociated or monovalent anions.

Also, according to the present invention, 9 common salt, chloridizing power/I/V um.

Even if an inorganic salt such as magnesium chloride coexists in the range of 1 to 1096, the adsorption capacity does not decrease at all.

Adsorption and elution properties using the Kago method are also good. In particular, the method of the present invention is extremely effective for removing and treating hot water of geothermal power plants where hexavalent arsenic is present at a low concentration of 0.01 to 2.4"l/11.

Next, the present invention will be explained in more detail with reference to Examples. In addition, % in the examples represents weight.

Reference example 1 N-methyμ-N-(2-hydroxyVphenimethytv
) -D-glucamiy62. While cooling, gradually added 137.59 g of a 12% caustic soda aqueous solution to make a homogeneous solution, and to this was added 57 g of 20.5 g of homarin. Then, the mixture was heated and stirred at 65° C. to 70 tl for 2 hours.

After cooling the obtained reaction solution to 50'C, pheno-μ
After adding m9.4f, heating and stirring were continued for 2 hours at 85c to 90U. Furthermore, this reaction solution was cooled to 50C, and 37%7
After adding 46.8% formalin and heating and stirring at 65T: to 70'C for 2 hours, the mixture was cooled to It: to obtain a viscous reaction liquid. When this reaction solution was subjected to bar-N polycondensation using chlorobenzene as a solvent in a conventional manner, a three-dimensional crosslinked resin in the form of 8B.O9 small spheres was obtained.

After washing this resin with water, 4. Neutralize with O96 hydrochloric acid 9
Next, it was treated with a 4.0% caustic soda aqueous solution, and then thoroughly washed with water until the phenolphthalein became colorless, resulting in a blackish brown resin with a water content of 42.79.
It was 6. In addition, this blackish brown resin is finely (pulverized),
The infrared absorption spectrum of the dried product is 5500
ft and around 1100a-x, and from the single element analysis value (N: 5.28%), pheno-〃 and N-methyμ-N-(2-hydroxyphenylmethyl)-D- The molar ratio with gukamine is 1:0
．． It was 95.

Reference example 2 Commercially available iminodiacetic acid type chelate resin (sodium type)
Fill 100sr into a gaff scaphum with an inner diameter of 9m.

After washing with 500d of ion exchange water, 0.05
2,000 wt of an aqueous ferric chloride solution of M was passed through the tube for 1 hour at a side pressure of 100 d. Next, wash thoroughly with ion-exchanged water until trivalent iron ions are no longer detected in the effluent.
An iron(III) supported chelate resin was obtained.

Examples 1-2. Comparative Examples 1 to 3 Using the chelate resin obtained in Example 1 (!*Example 1) and the commercially available resin Amberphyto IRA-745 (manufactured by Rohm & Haas, Example 2), this was wetted.・Immerse in 50 d of an aqueous solution containing nitrous acid at 25°C, and quantify the arsenic concentration remaining in the solution after immersion for 24 hours by atomic absorption spectrophotometry. Then, the adsorption amount of the resin was determined.

In addition, for comparison, the resin obtained in Reference Example 2 (Comparative Example 1),
Commercially available strong basic ion exchange resin [(20-50 meth)
, Comparative Example 2], Ya V guy active translation [(30-60 Metsu V:L
) and Comparative Example 3] were measured in the same manner.

The results are shown in Table 1.

The composition of the arsenite-containing aqueous solution, which is the liquid to be treated, is (A
s ([1I)t 1250tsu71. NaCA' 5
．． 859/j, 1PH8-5).

Table 1 Example 3. Comparative Example 4 Commercially available chelating ion exchange resin Amberly) IRA
-744S was treated with 1N sodium hydroxide solution and then thoroughly washed with water. Next, this resin 50- has an inner diameter of 9H.
Fill the glass cuff and '! s”l/l concentration no As(
厘) containing aqueous solution (PIII 8.5 >
V) 20 hr-'', the liquid was passed by downward flow at a temperature of 25 to 50 r.The Aa (IK) concentration in the effluent was measured by spectrophotometry (diethyl-dioμ silver carbamate method, JISKO
102, 199 pages.

(1971), and the #i output concentration was determined.

The results are shown in Table 2.

Note that the composition of the aqueous solution containing As (1) is * (As
(1) 597g, NaCJ 2.09/l,
CaCjm 20/j * Na2 COs 100
”l/l, HmSiOs 40/l, NaF
'5t/l, Nam 804100g/J).

Also, for comparison, chelate resin 50 obtained in lI Example 2
The solution was passed in the same manner using d.

The results are also shown in Table 2.

Table 2 Patent applicant: Unitika Co., Ltd.

Claims (3)

[Claims] (1) A method for removing arsenic from an aqueous solution, which comprises bringing a chelate resin having a chelate-forming group represented by formula (I) into contact with an arsenic-containing aqueous solution to remove arsenic from the aqueous solution. (2) The removal method according to claim 1, wherein the chelate resin having a chelate-forming group represented by formula (I) is a phenol resin having a chelate-forming group represented by formula (I) in the phenol nucleus. (3) The removal method according to claim 1 or 2, wherein the arsenic is pentavalent arsenic.