SU561503A3 - The method of extraction of mercury from aqueous solutions - Google Patents

Description

one

The invention relates to methods for the recovery of mercury from aqueous solutions, it can be used for the purification of industrial wastewater, for example, in the electrolysis of alkali metal chloride solutions.

It is known to extract mercury from aqueous solutions with chelating compounds, for example diethyldithiocarbamate, in carbon tetrachloride 1.

In order to simplify the process, polyacrylthioamide and / or polyacrythoamide copolymer are used as an ogforming compound, in which the ratio of nitrile groups to thioamide, respectively thiolimide, groups is 0.6-12.

According to the proposed method, a copolymer of polyacrylthioamnd, divinylbenzene and acetylstylerol copolymer of polyacrylthioamide and styrene, a copolymer of polyacrylthioamide and methyl ether of methacrylic acid is used. The sulfur content of the sodolimers is more than 15%.

Polyacrylthioamide and polyacrylthiol copolymer are polymeric materials, part of which nitrile groups are replaced by HbiNoi thioamide AND / OR thio imide groups. Thioamide

2

the group may be in tautomeric equilibrium with the thiolimide form.

The formulas shown below show the structure of one of the possible elementary units of a full-acrylthioamide polymer, respectively copolymer, in which, for example, thioimide groups, respectively, tolimide groups, are located next to nitrile groups

CHi-CH-Clif-CHCSN c "s

in

2 j

-dHo-CH-CH -CH 1 CSN (J-SH II kn

Polyacrylthioasides and their copolymers can be used in a single form, for example in the form of powders, granulated products, lumps, etc.

The mercury compounds contained in the solution are chelated with the thioamide, respectively, with the thio-imide, groups. As a consequence, the absorptive capacity of the polyacrylthioamide and the corresponding copolymer material depends on the ratio of thioamide or thiolimide moieties and inert nitrile groups. For this reason, it is most preferable to use polymeric materials, the nitrile groups of which are possibly more fully replaced by hyoamide, respectively, titanium groups. Polymers with the specified high quality by washing to mercury ions are those in which 40 mol.% {Of the domestic groups are converted to thioacketdus, respectively, tetanus groups.

The absorption of mercury by polyacrythyloamide or polyacrylthiochacrylate copolymer is relatively weakly influenced by the pH value of the solution being treated, which contains salt of mercury. The high absorption capacity of polymers takes place in environments from more neutral to slightly acidic, however, ceteris paribus, even at a pH of I and a pH of 10, mercury absorption is observed, which is only 20% less than the maximally absorbed amount.

In addition, the absorption capacity of polymers depends on the state of their swelling. It is established that the absorption capacity of the swollen material is higher than that of the dry material, therefore, when implementing the proposed method, it is preferable to use strongly swollen polyacrylthioamides. In water, materials can be obtained, for example, if the polymer is precipitated from the reaction solution with water and immediately after that the solvent is carefully removed.

The presence of alkali metal salts and alkaline earth metal salts practically does not adversely affect the absorption capacity of polyacrylthioamide and polyacrylthioamide copolymer used in accordance with the invention. In the presence of heavy metal salts, mercury absorption is also extremely selective. Lead and iron ions, for example, are not absorbed at all, and copper ions, even at 9 molar excess, based on mercury ions, are absorbed in an amount of 2-3 wt. %

The molecular weight of the polymeric materials used in the chelation reaction is irrelevant. Polymers with an average molecular weight of about 50,000 to 130,000 are most useful, since such polymeric products are characterized by distinctive mechanical CBOiicTBaMM.

The rate of absorption of metal ions is influenced by the state of napa. polymeric material. If the polymer material, prior to contact with the solution being treated with a solution containing mercury salts, has a maximum degree to the ear, the nonionic metal ions flow linearly almost to saturation by Schmerian.

When non-swollen materials or incompletely swollen materials are used, the absorption of mercury ions first occurs very slowly, then the absorption rate gradually increases due to an increase in the swelling capacity of the polymer in the solution being cleaned, after which the absorption of metal ions gradually stops.

The proposed method can be implemented

both intermittently and continuously. During the period of the process, the chelating polymer material is suspended in a solution containing mercury salts.

Continuous method can be implemented

in the following way.

The solution containing mercury salts continuously passes through a layer of swollen potashakshtioamid. The contact time required for the mercury ions to be absorbed by the chelating polymer material from the solution, due to the large local excess of the chelating material, is much shorter than the contact time when the process is carried out periodically, therefore continuous

the method is most preferred.

The proposed method can be applied for the purification of solutions with any concentration. mercury, especially it is suitable for cleaning solutions with a low concentration of mercury. At the same time, the mercury concentration in the solution can be up to 0.5 ppm, since each mole of sulfur contained in the polymer material absorbs from 1 to L2 mole of mercury. This means that 1 g of a polymer material containing 25 mol.% Of sulfur absorbs from 7.8 to

9.4 mol (or from 1.60 to 1.88 g) of mercury, which corresponds to a maximum of 188 wt.,% Of polymer used.

PRI me R. As a chelating polymer, powdered polyacrylthioamide is used, which has been pre-swelled in water up to about 70%, the sodium groups of which are reduced by 40% to thioamide and thiolimide groups. The average molecular weight of the polymer material is 125,000, and the temperature is approximately 200 ° C.

11 g of this polymeric material is loaded into an ion exchange column with a diameter of 1.4 cm. The bulk volume (BUT) when the polymer was loaded to a height of 18.5 cm was 28.5 cm. A solution containing 5 ppm (ppm) of mercury ions and 2 g of sodium chloride per 1 was passed through the filled column at room temperature. l With a capacity of 660 ml / hour, the conversion time is 2.7 minutes, therefore the flow rate of the solution is 23

BUT / H The eluate has a concentration reduced by 2-6 ppHh, / m71rd. After passing 400 liters, which corresponds to 13,000 times the bulk volume, the concentration of mercury ion ions in the eluate increases gradually. The experiment was stopped and the column contents were divided in height into three equal parts.

When analyzing the contents of the column in separate parts, the following amounts of mercury were found (in%):

Upper part21.9 (1.08 g)

Average - -14.7 (0.67g)

Lower 7 (0.25 g)

Example 2.0 g of swollen powdered on acrythioamide with a sulfur content of 25 mol. The mixture is stirred for 72 hours at room temperature in a solution containing 4.1 g of mercury (II) chloride and 3.5 g of chlorohydrochloride in 100 ml of water, then the polymer material is filtered and washed thoroughly with water.

3.12 g of a light yellow color polymer chelate is obtained, analysis of which for mercury content indicates the presence of 60 wt.% Mercury, and the chlorine content is 8.8 wt.%.

Example 3.1, Ln of a non-swollen powdered copolymer of acridioamide and acrylic acid methyl ester, obtained at the synthesis of acrylonitrile and methyl acrylic acid 86; 15, containing 16.2 mol. 7 sulfur, stirred at room temperature for 24 hours in a solution containing 4.1 g of mercury chloride (II) and 3.5 g of sodium chloride in 100 ml of water. After that, the polymer material is filtered and thoroughly washed with water. 2.41 g of polymer are obtained.

chelate, painted in a light yellow color, containing 52% mercury and 7 wt. % chlorine.

Claims (4)

1. A method for recovering mercury from aqueous solutions of chelating compounds containing sulfur, characterized in that, in order to simplify the process, polyacrylthioamide and / or a copolymer of polyacrythlyamide are used as chelating compounds. 2. A method according to claim 1, characterized in that polyacry is used; thioamide, in which the ratio of nitrile to thioamide, respectively thiolimide, groups is 0.6-12. 3. A method according to claim 1 wherein a copolymer of polyacrylthioamide, divinylbenzene and acetylstyrene, a copolymer of polyacrylthioamide and styrene, a copolymer of polyacrylthioamide and methacrylic acid methyl ester is used. 4. A method according to claim 3, characterized in that the copolymer with a sulfur content of more than 15% is exchanged. Sources of information taken into account during examination: 1. I.Stara, Extraction of chelates, MIR, M. 1966, pp. 230, 231, 235, 246, 247.