Electrolytic arsenic removal for recycling of washing solutions in a remediation process of CCA-treated wood

The remediation of chromated copper arsenate or CCA-treated wood is a challenging problem in many countries. In a wet remediation, the recycling of the washing solutions is the key step for a successful process. Within this goal, owing to its solubility and its toxicity, the removal of arsenic from washing solution is the most difficult process. The efficiency of arsenic removal from As(III) solutions by electrolysis was investigated in view of the recycling of acidic washing solutions usable in the remediation of CCA-treated wood. Electrochemical reduction of As(III) is irreversible and thus difficult to perform at carbon electrodes. However the electrolytic extraction of arsenic can be performed by the concomitant reduction of the cupric cation and arsenite anion. The cathodic deposits obtained by controlled potential electrolysis were analyzed by X-ray diffraction (XRD) and energy dispersive X-ray microanalysis. XRD diffraction data indicated that these deposits were mixtures of copper and copper arsenides Cu3As and Cu5As2. Electrolysis was carried out in an undivided cell with graphite cathode and copper anode, under a controlled nitrogen atmosphere. The evolution of arsine gas AsH3 was not observed under these conditions.