SU1475953A1 - Method of recovering metal from spent nitric-acid etching solutions - Google Patents

Abstract

The invention relates to the treatment of industrial wastewater, in particular, spent pickling solutions with the extraction of valuable metals from them. The purpose of the invention is to increase the nickel yield. Nickel extraction from spent nitrate pickling solutions is carried out by electrolysis in a three-chamber electrodialyzer at a cathode current density of 2-5 A / dm ² when filling the cathode chamber with a solution of sulfuric acid, the anode chamber with a solution of nitric acid, and the middle chamber with spent etching solution. 1 il.

Description

The invention relates to the treatment of industrial wastewater, in particular spent pickling solutions, with the extraction of valuable metals from them.

The purpose of the invention is to increase the nickel yield.

The invention is illustrated by the following examples.

The spent pickling solution passes (see drawing) the filter 1 to remove sludge and enters the middle chamber of the electrolyzer 2, which is separated on one side by the anion-exchange MA-41 membrane on the mylar base, and the other by the cation-exchange membrane of the type MK-40 on the polyester layer.

The anodic and cathodic chambers are filled with a 3-5% solution of HN03 and a 5% solution of H2SO4, respectively. To adjust the acidity of the solution in the cathode chamber from tank 3

periodically, a 5% solution of HiS04 is supplied, maintaining the pH of the medium in the cathode space equal to 2-2.5. Nickel ions under the action of electric field forces migrate through the cation-exchange membrane into the cathode space, where they combine with S0 | ions to form a nickel sulfate solution, from which metallic nickel is deposited on the cathode.

In the anode chamber, due to the interaction of N0-anions migrating through the anion-exchange membrane, nitric acid with a concentration of 19–20% is formed. After the end of the electrolysis, the nitric acid solution regenerated by this method from the anode chamber of the electrolyzer enters the tank 4 for correction and then goes to the preparation of the pickling solution, H) in the range 3-5% by weight

SO

no significant influence on the process of electrolysis. The electrolysis of the spent pickling solution is carried out to a residual nickel concentration in the average space of 1.0-1.5 g / l, which corresponds to 0.1-0.15 wt.% (Or 0.1 wt.%), Due to the peculiarities process, a significant reduction in cathodic and anodic current outputs. In the known method, the residual content of nickel ions in the solution is 1.5-15 wt.%.

Example 1. 200 ml of spent pickling solution containing, g / l: HNOj 6, H, 0 5, phenyl 1-chevine 5, nickel 40, are sent to the middle space of a 3-chamber electrolyzer with anodic and cathodic spaces - exchange membranes of type MK-40 and MA-4 on mylar basis,

The cathode chamber of the cell with a capacity of 100 ml is filled with a 5% solution, maintaining the pH in the cathode compartment equal to 2-2.5. An anode chamber with a capacity of 100 ml is filled with a 3% NHS solution. At a cathode current density of 2 A / dm2, an anode current density of 2 A / dm2, and a temperature of 35–40 ° C during the electrolysis time of 9 hours, the amount of released nickel is 7 75 g, recovery rate 96.2%. Nitric acid is formed in the anode chamber with a concentration of 19 wt%.

Example 2. 200 ml of spent pickling solution with a content, g / l: HNO ", 6, 5, phenylurea 5, nickel 40 g / l, are sent to the middle space of a 3-chamber electrolyzer. The cathode chamber of the electrolyzer is filled with 100 ml of 5%. maintaining the pH in the cathode compartment, equal to 2-2.5. The anode chamber is filled with 100 ml of 5% HNQj solution. At cathode current density

3.5 A / dm2, a temperature of 35-40 ° C during the electrolysis time of 8.5 hours, the amount of metallic nickel released at the cathode will be 7.75 g, the recovery rate is 96.8%. Nitric acid of 20% by weight is formed in the anode chamber.

Example 200 ml of the spent pickling solution of the same composition as in examples 1, 2; the cathode and anode chambers are filled with 5% solutions of H2 SO and HNOg, respectively. During the electrolysis time of 7.5 hours, the amount of nickel released on the cathode is 7.8 g (the degree of nickel extraction is 97.5%), the concentration of nitric acid in the anode chamber increases to 20%, the cathode current density is 5 A / dm2.

These examples show that the proposed technology for the extraction of nickel from spent nitric acid pickling solutions can significantly increase the degree of extraction of nickel and obtain pure metallic nickel. The use of lower cathode current densities allows an increase in the service life of ion-exchange membranes.

Ф о р / м у-л and inventions

A method for extracting metal from spent nitric acid etching solutions, mainly nickel, including electrolysis in a three-chamber electrodialyzer, characterized in that, in order to increase nickel yield, the process is carried out at a cathode current density of 2-5 A / dm2 and filling the cathode chamber with a solution sulfuric acid, the anode chamber with a solution of nitric acid, and the middle chamber with spent pickling solution.

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Claims (1)

Claim A method for extracting metal from spent nitric acid pickling solutions, mainly nickel, including electrolysis in a three-chamber electrodialyzer, characterized in that, in order to increase the nickel yield, the process is carried out at a cathode current density of 2-5 A / dm ² and the cathode chamber is filled with a solution sulfuric acid, the anode chamber with a solution of nitric acid, and the middle chamber with spent pickling solution. Spent Etchant Solution ---- X 11 2 “Mr. Metallic Nickel To sewage treatment plants