Recovery Cyanide from Cyanide-Containing Wastewater By Selective Electroconcentration

A large amount of hydrogen cyanide poisonous gases released from Polyacrylonitrile（PAN）-basis carbon fiber manufacturing process. Stimulated by its value and harmfulness to human and environment, electrochemical methods have proposed to deal with the double-edged materials. A novel electrodeionization technology, named as selective electroconcentration (SEC), was used to segregate targeted ions from mixed aqueous solution. SEC is an approach not only removes needless ions，but also obtains concentrated ions in brine water. In this paper, synthetic water contained cyanide and carbonate was investigated to examine the separation and enrichment effects of SEC. It was found that the pH raise in divalent ions concentrated chamber prevented carbonate conversion, which avoided bicarbonate competing with cyanide. Thus monovalent ions were able to migrate to next concentrated chamber. To acquire details about how to optimize the SEC apparatus, operation parameters like current, pH change, and proportion were discussed here.

   Practical results show that cyanide purity can reach 90%, with a high cyanide concentration (250mmol/L). The cyanide product can be used as plating solution. Beyond that, the concentration of treated cyanide wastewater conformed sewage discharge standard. It is proved that SEC is feasible to concentrate cyanide and the separation efficiency is satisfactory.