Nickel recovery from electroplating sludge via bipolar membrane electrodialysis

In this study, nickel (Ni) was recovered from electroplating sludge in the form of Ni(OH)₂ using a bipolar membrane electrodialysis (BMED) system. The results showed that the H⁺ generated by the bipolar membrane could effectively desorb Ni from the sludge to the solution and the solution pH considerably affected Ni desorption. The desorption process can be described using the first-order kinetic model. The current density and solid/liquid ratio (m/v) considerably affected Ni recovery. Moreover, 100% of Ni was removed from the electroplating sludge and 93.5% of Ni was recovered after 28 h under a current density of 20 mA/cm², a solid/liquid ratio of 1.0:15 and an electroplating-sludge particle size of 100 mesh. As the number of electroplating compartments increased from one to two and three, the current efficiency for recovering Ni changed from 12.1% to 11.8% and 11.9%, respectively, and the specific energy consumption decreased from 0.064 to 0.048 and 0.039 kW·h/g, respectively. Fourier-transform infrared spectroscopy and Raman spectroscopy showed that the precipitate obtained in this study is similar to commercial Ni(OH)₂ and the purity of Ni(OH)₂ in the obtained precipitate was 79%. Thus, the results showed that the BMED system is effective for recovering Ni from electroplating sludge.