Boric acid enhanced degradation of organic pollutant by Cu(II)/peroxymonosulfate: Performance and mechanism

In this paper, it was found that boric acid (BA) could improve the degradation of rhodamine B (RhB) by Cu(II)-activated peroxymonosulfate (PMS). At pH 8.5, the addition of BA could stabilize pH and generate the highly active complexes with Cu(II), which could accelerate the reduction of Cu(II) by PMS. The formed Cu(I) could activate PMS to form sulfate radical (SO4–) and/or be oxidized to Cu(III). According to the results on radical scavenging experiments, SO4– and Cu(III) both participated in the degradation of RhB in BA/Cu(II)/PMS system. Because the binding ability of BA with Cu(II) is pH-dependent, the promotion effect of BA in Cu(II)/PMS process occurred only under weakly alkaline conditions. The presence of HCO3– and natural organic matter (NOM) both had an inhibition effect on RhB degradation in BA/Cu(II)/PMS system, while Cl– could promote the removal of RhB. This study provides a new idea to enhance PMS activation by Cu(II).