Treatment method of trivalent chromium passivation wastewater

Abstract

The invention discloses a treatment method for trivalent chromium passivation wastewater, adding ferrous chloride solution to a wastewater treatment pool, then adding lime emulsion to make the pH of the wastewater to 10-11, and co-precipitating carboxyl groups with ferrous ions and calcium ions The organic acid complexing agent is used to make trivalent chromium and other metal ions generate hydroxide precipitates, add flocculants to aggregate the precipitated particles, filter and separate the precipitates, adjust the pH of the wastewater to 6-9, and obtain the product. The treatment results meet the requirements of Table 3 of GB 21900-2008 "Electroplating Pollutant Discharge Standard". The invention creates a new method for removing carboxyl-containing organic acid complexing agents and heavy metal ions in waste water by using ferrous ions and calcium ions. The process is simple and easy, the treatment cost is low, and the method has good market application prospects.

Description

technical field [0001] The invention belongs to the technical field of industrial wastewater treatment, in particular to a treatment method for trivalent chromium passivation wastewater. Background technique [0002] Replacing the highly toxic hexavalent chromium passivation with trivalent chromium passivation has been widely used and achieved good environmental and social benefits. [0003] The trivalent chromium passivation solution contains two kinds of metal ions, trivalent chromium and cobalt, and a carboxyl-containing organic acid complexing agent that forms complex ions with it. Some trivalent passivation solutions also contain a small amount of rare earth salts. Trivalent chromium passivation is generally used for passivation treatment of zinc coating and zinc-nickel alloy coating. Passivation wastewater contains zinc ions, nickel ions, iron ions, and rare earth element ions in addition to the components of passivation solution. [0004] The composition of the triva...

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Problems solved by technology

[0004] The composition of the trivalent chromium passivation solution changes rapidly during use and needs to be replaced frequently, resulting in a large amount of trivalent chromium passivation waste liquid, so the treatment volume of trivalent chromium passivation wastewater is relatively large

However, the time for trivalent chromium passivation to be put into large-scale production is relatively short, and its wastewater treatment technology is not yet mature enough.

[0005] Citric acid has strong oxidation resistance, and the efficiency of destroying citric acid by traditional oxidation methods is low. Generally, a large amount of oxidant is required, and the treatment cost is high. It is difficult to effectively remove citric acid in winter when the temperature is low.

Therefore, the trivalent chromium passivation wastewater containing citric acid is treated by the traditional oxidation-hydroxide precipitation method, and the content of trivalent chromium in the treated wastewater often does not meet the requirements of GB21900-2008 "Electroplating Pollutant Discharge Standard"

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