A WO3/PPy/ACF modified electrode in electrochemical system for simultaneous removal of heavy metal ion Cu2+ and organic acid.

Heavy metal ions and organic acids are common pollutants in electroplating wastewater. Effective and economic treatment of such wastewater needs novel technologies. In this study, WO3/PPy-1/ACF electrode was prepared using a hydrothermal modification method and it has large specific area (788.27 m2 g-1), high areal capacitance (2.58 F cm-2 under 5 mA cm-2 charge and discharge) and excellent conductivity. The modified electrode was used in an electrochemical system with activated carbon fiber felt (ACF) as counter electrode. The system simultaneously and successfully removed 97.8 % Cu2+ and 80.1 % citric acid (CA) from a simulated electroplating wastewater (typically 100 mg L-1 Cu2+ and 800 mg L-1 CA) in five- hour optimized operation. The influence of operating parameters (circulating inflow rate, applied voltage and influent pH) on the treatment performance was compared. There is interplay between Cu2+ reductive deposition and CA oxidation. The synergetic electrochemical treatment mechanism involves formation of hydrogen peroxide, free radicals, and catalytic effect of Cu species was proposed. This electrochemical system which is low-cost, easy to operate and highly efficient, may be applicable in treating acid-wash or electroplating wastewater, containing heavy-metal ions and organic acids.