Nickel recovery from an electroplating rinsing effluent using RCE bench scale and RCE pilot plant reactors: The influence of pH control

Abstract

This work analyses the electrochemical recovery of nickel from synthetic and real electroplating rinsing effluents (1220mgL−1 Ni(II)) without supporting electrolyte, using two rotating cylinder electrode reactors: bench scale (0.50L) and pilot plant (10L). The electrolysis were conducted with and without pH control (pH=4) at three cathode rotation speeds (200, 300 and 500rpm), utilizing a 316-type stainless steel cylinder as cathode, and six RuO2/TiO2 dimensional stable as anodes. The performance of both reactors revealed that the pH control acts favorable in two ways: (a) inhibiting the nickel dissolution caused by parasitic reactions, and (b) buffering the acidification generated in the anode due to water oxidation. This control is effective to increase the nickel recovery and current efficiency, as well as lower down the energy consumption. The optimization of the cathode rotation speed is crucial during the electrochemical recovery of nickel to prevent larger mass-transfer rates of H+, which result in low current efficiencies. Although all the nickel contained in the effluent can be recovered with both reactors, it would be wise to consider the use of other technique appropriate to remove the residual Ni(II) concentration in order to minimize the operational costs. Thus, the electrochemical recovery of nickel can be feasibly carried out from real electroplating rinsing effluents at industrial scale with pH control, without adding a supporting electrolyte.