Treatment method for removing cyanide and hexavalent chromium in electroplating wastewater at same time

Abstract

The invention discloses a treatment method for removing cyanide and hexavalent chromium in electroplating wastewater at the same time. The treatment method comprises the following steps of: according to acid-base property of the electroplating wastewater, adding acid or base for regulating pH to be about 6, then adding sodium metabisulfite, under acidic condition, breaking cyanide ions through oxidation and reducing the hexavalent chromium at the same time, finally adding base for regulating pH to be about 9, and carrying out precipitation separation, so that the wastewater meets discharge standard. The treatment method disclosed by the invention can deep treat a small amount of hexavalent chromium and cyanide which coexist in the wastewater, enables the wastewater to continuously and stably meet the discharge standard and has the advantages of simple technological process, easy operation, strong adaptability on water quality fluctuation, relatively low treatment cost and easiness in meeting the discharge standard.

Description

technical field [0001] The invention belongs to the technical field of wastewater treatment, in particular to a treatment method for simultaneously removing cyanide and hexavalent chromium in electroplating wastewater. Background technique [0002] The composition of electroplating wastewater is complex, and its treatment technology is also varied, such as traditional chemical neutralization precipitation method, traditional redox method, membrane separation method, etc. In the traditional chemical neutralization precipitation method, the electroplating wastewater is divided into three streams of wastewater: chromium-containing wastewater, cyanide-containing wastewater and acid-base wastewater (copper-nickel-zinc-containing wastewater), and the chromium-containing wastewater and cyanide-containing wastewater are treated separately first. Finally, it is mixed with acid-base wastewater. The specific steps are: the hexavalent chromium ions in the chromium-containing wastewater ...

AI Technical Summary

Problems solved by technology

[0003] However, in actual operation, due to the common problem of mixed discharge in the electroplating industry (i.e., the phenomenon of running, running, dripping, and leaking in the workshop), there are often hexavalent chromium wastewater and cyanide-containing wastewater mixed in the comprehensive wastewater, causing chromium and cyanide to exceed the standard. Although the amount of hexavalent chromium and cyanide is small, it greatly increases the difficulty of removal, because cyanide ions are easy to form copper cyanide complexes and nickel hydrogen complexes that are difficult to remove with copper ions and nickel ions in acid-base wastewater. As a result, copper and nickel in the comprehensive wastewater also exceed the standard, and due to the simultaneous presence of hexavalent chromium and cyanide ions, it is difficult to treat the comprehensive wastewater with traditional processes. If the chemical neutralization precipitation method is used again, the hexavalent Valence chromium is reduced to trivalent chromium, and then the pH value is adjusted to break cyanide to remove cyanide, which may cause the phenomenon that cyanide volatilizes highly toxic hydrogen cyanide; if other methods are used, the treatment process is complicated and the cost is too high. The cost may be as high as 25 to 35 yuan, which greatly increases the production cost of the enterprise