Effective oxidation decomplexation of Cu-EDTA and Cu²⁺ electrodeposition from PCB manufacturing wastewater by...

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 = 3 cm, [Na₂S₂O₈]0 = 5 mM, current density = 12 mA/cm², and reaction time = 180 min. 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 3 h 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.