RU2481274C2 - Method of removing mercury from amalgamation solution and flush water - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to removal of mercury ions from a spent amalgamation solution and flush water and can be used to decontaminate spent solutions from amalgamation of zinc electrodes of chemical cells. The method involves removal of mercury from a spent amalgamation solution and flush water in form of solid particles. The spent solution or flush water is electrochemically treated in the cathode chamber of a two-compartment electrolysis cell with a cation-exchange membrane, in whose anode camber there is a platinised titanium anode and in the cathode chamber there is a cathode made from titanium or stainless steel which revolves at a speed of 120-300 rpm. The anode chamber is filled with zinc acetate in amount of 1-10 g/l and acetic acid in amount of 5-30 g/l. Electrolysis is carried out at cathode current density of 0.1-1 A/dm² while passing 1-10 A·h/l, after which particles of zinc powder containing mercury are separated from the aqueous phase.

EFFECT: method enables to form a closed process cycle on amalgamation area and prevent the release of mercury compounds into waste water in form of nanoparticles which cannot be trapped by filters.

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Description

The invention relates to the production of chemical current sources, specifically to the removal of mercury ions from a spent solution of amalgamation of zinc electrodes and wash water in this operation, which contain acetic acid, zinc ions and mercury.

A known method of removing mercury by adsorption on adsorbents forming complex compounds with it [US 6521131 (B1), op. 01/25/2001].

The closest to the problem to be solved and the effect achieved is the method of removing mercury from wastewater and other liquids by binding it to insoluble complexes and subsequent ultra - or microfiltration. [CA 2734634, op. 03/04/2010].

A significant drawback of this method is the formation of microparticles, the complete removal of which by filtration is difficult.

The technical task of the invention is the extraction of mercury from spent solutions of amalgamation of zinc anodes and wash water in this operation in the form of mercury-containing particles of the solid phase, which are easily and completely separated from the liquid phase.

In the present invention, the problem is solved in that in order to remove mercury from the spent amalgamation solution and wash water in the form of solid particles, the spent solution or wash water is subjected to electrochemical treatment (see drawing) in the cathode chamber of a two-chamber electrolyzer (1) with a cation exchange membrane (3) , in the anode chamber (4) of which a platinum titanium anode (5) is located, and in the cathode chamber is a cathode (2) made of titanium or stainless steel, rotating at a speed of 120-300 rpm, and the anode chamber ru is filled with a solution of acetic acid 5-30 g / l and zinc acetate 1-10 g / l, and electrolysis is carried out at a cathodic current density of 0.1-1 A / dm ² , passing 1-10 A · h / l, after which zinc powder particles containing mercury are separated from the aqueous phase.

The process of extracting mercury from aqueous solutions by electrodepositing it at the cathode is unacceptable, since it proceeds at an extremely low speed. According to the invention, the main cathodic reactions are the discharge of hydrogen and zinc ions, moreover, zinc is deposited on the cathode in the form of dendrites that spontaneously separate from the cathode and form a suspension of crystals with a very large surface in solution. Mercury is contacted on particles of zinc powder, forming a surface amalgam on them. At the end of the process, the powder particles are separated from the aqueous phase by filtration or decantation.

The invention is illustrated by the following examples.

EXAMPLE 1

The spent amalgamation solution contains zinc acetate 3 g / l, mercury acetate 0.3 g / l and acetic acid 30 g / l. 10 l of the solution is placed in a container (1), which is a cathode chamber of a two-chamber electrolyzer. A submersible electrochemical module is placed in the tank, which represents the anode chamber (4) with the MK-40 cation exchange membrane, in which there is a platinum titanium anode (5) and 3 l of anolyte solution containing 10 g / l of zinc acetate and 30 g / l of acetic acid . A cathode (2) is placed in the cathode chamber (1) - a titanium rod 30 cm long and 0.5 cm in diameter, rotating at a speed of 300 rpm, and electrolysis is carried out at a cathode current density of 1 A / dm ² , passing 10 A · h / l At the end of the electrolysis, the immersion module (4) and the cathode were removed from the spent solution tank (1), and zinc powder containing mercury removed from the solution and partially located at the bottom of the cathode chamber and partially on the cathode surface was used to prepare new portions of the amalgamation solution . Mercury and its compounds were not found in solution.

EXAMPLE 2

In a container (1) (see Example 1), 10 l of a solution from a non-flow washing bath of zinc anodes discharged from an amalgamation bath is placed. The composition of the solution: zinc acetate - 0.5 g / l, mercury acetate - 0.03 g /, acetic acid - 3 g / l. The composition of the anolyte solution in the submersible electrochemical module (4): zinc acetate - 1 g / l, acetic acid - 5 g / l.

The titanium cathode (2) used in Example 1 was replaced with a stainless steel plate with a surface of 1.5 dm ² rotating at a speed of 120 rpm. Electrolysis was carried out at a cathodic current density of 0.1 A / dm ² , passing 1 A · h / L. At the end of the electrolysis, the immersion module (4) and the cathode (2) were removed from the wash tank (1), and zinc powder containing mercury removed from the wash water and partially located at the bottom of the cathode chamber and partially on the cathode surface was used for new portions amalgamation solution. No mercury and its compounds were found in the treated wash water.

The proposed method allows you to create a closed technological cycle at the amalgamation section - completely return to production waste solutions and wash water in non-flow washing baths (collection baths) and eliminate the removal of mercury compounds in the form of nanoparticles not retained by filters into wastewater, which inevitably takes place in known ways.

1 - container with the processed solution

2 - rotating cathode

3 - cation exchange membrane

4 - submersible electrochemical module

5 - platinum titanium anode

6 - power supply (rectifier)

Claims (1)

The method of removing mercury from the spent amalgamation solution and washing water in the form of solid particles, characterized in that the spent solution or washing water is subjected to electrochemical treatment in a cathode chamber of a two-chamber electrolyzer with a cation exchange membrane, in which the platinum titanium anode is located in the anode chamber, and in the cathode chamber a cathode made of titanium or stainless steel, rotating at a speed of 120-300 rpm, and the anode chamber is filled with a solution of zinc acetate 1-10 g / l and acetic acid 5-30 g / l, and The electrolysis is carried out at a cathodic current density of 0.1-1 A / dm ² , passing 1-10 A · h / l, after which the particles of zinc powder containing mercury are separated from the aqueous phase.