Simultaneous Cu(II)-EDTA decomplexation and Cu precipitation by a heat activated percarbonate-persulfate system

A heat-activated sodium percarbonate and persulfate (heat-SPC-PS) system was employed to treat Cu(II)-EDTA wastewater effectively. In this binary-oxidant system, SPC functioned as an oxidant, precipitant, and neutralizer throughout the treatment process. Under optimized conditions (SPC dosage: 28.3 mM, PS dosage: 47.0 mM, temperature: 80 °C), the system achieved a Cu removal efficiency of 95.9 % and rate constant of 0.391 min −1 after 10 minutes of treating a 3.14 mM of Cu(II)-EDTA solution. The Cu ions released from Cu(II)-EDTA were precipitated as a mixture of CuO, CuCO₃, and Cu₂(OH)₂CO₃. Additionally, SPC neutralized the H⁺ ions generated from PS hydrolysis, yielding a final solution pH of approximately 7.86. When followed by an alkali precipitation (AP) step at pH 11, the combined heat-SPC-PS + AP process further increased Cu removal efficiency from 95.9 % to 98.4 %, with precipitation occurring as CuO. Reactive oxygen species (ROS) generated by heat-SPC-PS system, including OH • , SO 4 •- , O 2 •- , and 1 O 2 were key contributors to the decomplexation of Cu(II)-EDTA. Moreover, the treatment substantially reduced phytotoxicity of Cu(II)-EDTA solutions. Lettuce grown with the treated effluent exhibited growth indices comparable to those irrigated with deionized water, demonstrating the potential of the heat-SPC-PS system for the safe and effective treatment of heavy metal complexes in wastewater.