Electrochemical degradation of Ni-EDTA complexes in electroless plating wastewater using PbO2-Bi electrodes

With the rapid growth of nickel (Ni) electroplating industries, large amounts of Ni-containing wastewater are generated every year. Ni in these wastewaters is generally present as complexes with ligands such as ethylenediaminetetraacetic acid (EDTA) with degradation of these complexes typically a prerequisite for Ni removal. Electrochemical advanced oxidation processes (EAOP) can be used to degrade these Ni-EDTA complexes though development of cost effective, highly catalytic, stable electrodes remains a challenge. In this study, bismuth doped lead oxide (PbO2-Bi) electrodes were prepared via a co-electrodeposition process and used for electrochemical degradation of Ni-EDTA and removal of Ni. The effects of Bi doping ratio and electrodeposition current density on the electrode properties were thoroughly investigated. Results demonstrated that 90% of the Ni-EDTA complexes could be degraded and 30% total organic (TOC) and 66% Ni removed in 2 h using the optimized electrode (2% Bi doped PbO2 electrode prepared at an electrodeposition current density of 45 mA cm−2) at a reasonable energy consumption of 3.6 kWh m−3. Minor deterioration in Ni-EDTA degradation performance (<5%) was observed with minimal lead leakage occurring after 160 h electrolysis. Further investigations revealed that the lifetime of the PbO2-Bi electrode was 2.5 times longer than the pristine PbO2 electrode. The results of this study highlight the potential of EAOP employing PbO2-Bi electrodes as a cost-effective approach for the treatment of Ni-containing wastewaters.