Removal of 2,4 dichlorophenol using microwave assisted nanoscale zero-valent copper activated persulfate from aqueous solutions: Mineralization, kinetics, and degradation pathways

Abstract The purpose of this study was to evaluate the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solutions using microwave irradiation (MW) assisted nanoscale zero-valent copper (CuO) activated persulfate (PS). Effective operational parameters including, pH of the solution, PS concentration, CuO dosage, MW power, and initial 2,4-DCP concentration, were investigated. Results indicated that the MW/PS/CuO system achieved higher efficiency in 2,4-DCP degradation than MW/PS, MW/CuO, and PS/CuO systems. At PS concentration of 0.4 g/L, CuO dosage of 40 mg/L, initial pH of 9 and initial 2,4-DCP concentration of 50 mg/L, complete degradation of 2,4-DCP (>98%) was achieved in reaction time of 90 min. In optimal condition, 80% and 45% of COD and TOC removal rates were respectively obtained within 90 min. Through the use of methanol (MA) and tert-butyl alcohol (TBA) as radical scavengers, sulfate radical was identified as the main radical species generated during the process. Also, the results showed that with an increasing ion strength, 2,4-DCP removal rate slightly decreased. The degradation of 2,4-DCP was pseudo-first-order kinetics. The phenol, 2,4-dichlororesorcinol, 2-chlorohydroquinine, 2-chlorophenol, p-chlorophenol, catechol, hydroquinone, oxalic acid, and acetic acid were identified as the major intermediates of 2,4-DCP degradation. Also, a tentative pathway for degradation of 2,4-DCP using the MW/PS/CuO system was proposed.