Cyanide removal with a copper/active carbon fiber Cathode via a combined oxidation of a Fenton-like reaction and in situ generated copper oxides at anode

Abstract

Cyanide is widely present in electroplating wastewater or metallurgical effluents. In the present study, the electrochemical destruction of cyanide with copper/active carbon fiber (Cu/ACF) composite cathode and Dimensionless Stable Anode (DSA) under alkaline conditions was investigated. Firstly, various cathode materials including stainless steel, ACF, copper plate and Cu/ACF were compared for cyanide removal. Cyanide removal efficiencies by the individual H2O2 oxidation generated using ACF cathode or individual DSAs anodic oxidation using stainless steel cathode were less than 20%. Using Cu/ACF as the cathode, the removal efficiency of cyanide was largely improved compared with other cathodes. At the current density of 50.01A/m2 and the geometric area ratio of Cu/ACF=1:2, the concentration of cyanide was lowered from 1.50 to 0.07mM within 90minutes. Due to the dissolution of copper plate by the cyanide ions, the concentration of copper ions increased rapidly at first and then decreased with the efficient destruction of cyanide ions. Combined with the SEM-EDX and XPS analysis of the anode surface, it was concluded that the generation of copper oxides occurred at the anode surface, which exhibited catalytic activities for cyanide removal. Meantime, ESR results confirmed the generation of hydroxyl radicals in solution. Hydroxyl radicals generated in the reaction between copper cyanides complexs and H2O2 were responsible for the cyanide removal. Once the cyanide removal was completed, part of the copper ions was reduced and deposited onto the cathode and part of the copper ions was deposited onto the anode. Therefore, the next recycle for cyanide removal by copper oxides catalytic oxidation at the anode and the Fenton-like oxidation in the solution began. Cyanate was identified as the only product in this system.