Reagent cleaning of washing waters of galvanic industries

Abstract

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The main results of research tests of the developed technologies and installations for reagent treatment of metal-containing wastewater and washing water, using the example of low-concentration spent solutions of electrochemical nickel plating and chromium plating processes present in the article. The proposed technologies provide full or partial return of purified water for washing products after the stage of applying a metal coating on them and for preparing working solutions – precipitants. When disposing of spent solutions of nickel plating processes, a saturated solution of soda ash at 200C was used as a precipitant; for chromium-containing wastewater, a saturated solution of barium hydroxide (II) with preliminary alkalizing of the original wastewater. Tests have confirmed the possibility of automatic dosing of reagents depending on the pH of the medium, which can be used for both continuous and periodic washing processes. A mode of washing products after the processes of electrochemical nickel plating and chrome plating is proposed. The length of time during which it is possible to wash products without updating the volume of the bath is determined. Calculations carried out based on the results of the tests substantiated the possibility of reducing the consumption of fresh water supplied for washing, due to the reversible use of purified water without worsening the results of washing products. Practically confirmed reduction of water consumption for washing in the amount of 35% after the process of electrochemical chromium plating and in the amount of 65% after the process of nickel plating from the regulated values. Based on the results of the chemical and X-ray structural analysis of the sediments obtained during the disposal of washing waters after the processes of electrochemical nickel plating and chromium plating, ways of their further use are proposed.