Effective oxidation decomplexation of Cu-EDTA and Cu2+ electrodeposition from PCB manufacturing wastewater by persulfate-based electrochemical oxidation: Performance and mechanisms.

Abstract

Complex wastewater matrices such as printed circuit board (PCB) manufacturing wastewater present a major environmental concern. In this work, simultaneous decomplexation of metal complex Cu-EDTA and reduction/electrodeposition of Cu2+ was conducted in a persulfate-based electrochemical oxidation system. Oxidizing/reductive species were simultaneously produced in this system, which realized 99.8% of Cu-EDTA decomplexation, 94.5% of Cu2+ reduction/electrodeposition under the conditions of original solution pH = 3.2, electrode distance = 3cm, [Na2S2O8]0 = 5mM, current density = 12mA/cm2, and reaction time = 180min. The total treatment cost is as low as 0.80 USD/mol Cu-EDTA. Effective mineralization (74.1% total organic carbon removal) of the solution was obtained after 3h of treatment. •OH and SO4•- drove the Cu-EDTA decomplexation, destroying the chelating sites and finally it was effectively mineralized to CO2, H2O and Cu2+. The mechanisms of copper electrodeposition on the stainless steel cathode and persulfate activation by the BDD anode were proposed based on the electrochemical measurements. The electrodes exhibited excellent reusability and low metal (total iron and Ni2+) leaching during 20 cycles of application. This study provide an effective and sustainable method for the application of the electro-persulfate process in treating complex wastewater matrices.