Enhanced precipitation of cyanide from electroplating wastewater via self-assembly of bimetal cyanide complex

• Advanced method for cyanide purification basing on precipitation.
• 99% of cyanide were removed from the simulated wastewater.
• 75% of cyanide could be removed from the real electroplating wastewater.
• Co-existed heavy metal can be simultaneously treated.
• The main precipitation was bimetal cyanide complex.

A novel and cost-effective technology has been developed to enhance cyanide (CN) removal from electroplating wastewater. In this process, CN and Zn wastewater was proportionally mixed with Ni wastewater at a controlled pH for precipitation. As a result, 99% of CN and 85% of Zn were removed from the simulated test. Characterizations of XRD and FTIR displayed that CN and Zn removals were attributed to the formation of ZnNi bimetal cyanide complex. When this method was applied to the treatment of CN and Zn electroplating wastewater, 75% of CN and 100% of Zn were synchronously removed by forming a mixture of ZnNi bimetal cyanide complex and NiZnOH. Furthermore, mechanism analyses showed that CN first transformed into Ni(CN)42−, then precipitated into bimetal cyanide complex. This work revealed that the presented strategy is an effective approach for the purification of both cyanide and heavy metal from electroplating wastewater.

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