Strong enhancement on tetrabromobisphenol A removal in natural water matrix by adding cysteine into Cu(II)/peroxymonosulfate system over the wide pH range of 4–12: Efficiency and mechanism

Although Cu(II) can trigger peroxymonosulfate (PMS) oxidation of pollutants, it is only effective under alkaline environments and is susceptible to interference by aqueous matrix components. In this study, cysteine, a natural thiol and amino acid, was found to greatly improve the performance of tetrabromobisphenol A (TBBPA) elimination in the Cu(II)/PMS system across a broad pH range of 4.0–12.0. The cysteine/Cu(II)/PMS system achieved a 94.34 % elimination of TBBPA within 10 min at pH 7.0, which had a 7.55-fold increase in efficiency relative to the Cu(II)/PMS system, and superior to the previously-reported hydroxylamine and gallic acid-enhanced Cu(II)/PMS systems. Cu(III)-(cysteine) 2 , as opposed to radicals, was the main reactive species leading to the removal of TBBPA, contributing at least 91.53 %. Cysteine first coordinated with Cu(II) through sulfhydryl groups (−SH) and rapidly converted Cu(II)-(cysteine) 2 to Cu(I)-(cysteine) 2 , then Cu(III)-(cysteine) 2 was formed finally by the further oxidation of PMS on Cu(I)-(cysteine) 2 . This enhancement was further extended to other thiols including cysteamine, β-mercaptoethanol and mercaptosuccinic acid. Four potential degradation pathways of TBBPA were inferred from the determined nine degradation intermediates. A marked decline in the toxicity of the reaction solutions was observed after the elimination of TBBPA. Furthermore, the cysteine/Cu(II)/PMS system shown high anti-interference performance with common cations and anions (Ca(II), Mg(II), NO 3 – , SO 4 2– , HCO 3 – and Cl – ), humic acid and actual water samples. Overall, this study provided a promising approach to extend the working pH range of Cu(II)/PMS system and its anti-interference capability with actual water matrix, which was favorable for its potential utilization in water treatment.