Efficient degradation of phosphonate via trace Cu(II) mediated activation of peroxymonosulfate

Abstract

The phosphonates in wastewater have attracted much attention due to their potential risks to the aquatic environment, which is oxidized to orthophosphate (PO43−) is a vital step to achieve their removal. Advanced oxidation processes based on free radicals is usually crucial methods to remove phosphonates, which could be easily disturbed by water matrix. Herein, using 1-hydroxyethane1,1-diphosphonic acid (HEDP) as a model pollutant, a nonradical system was constructed via Cu(II)/PMS process. 82 % HEDP is degraded by trace Cu(II) (5 μM) mediated peroxymonosulfate (PMS) activation process within 60 min at pH = 7.0, which is much higher than that in Cu(Ⅱ)/peroxydisulfate (PDS) and Cu(Ⅱ)/H2O2 systems under identical conditions. The results of multiple experiments reveal that Cu(III) induing intramolecular electron transfer as the dominant reactive species makes responsible for the oxidation of HEDP in the Cu(II)/PMS process, whereas the role of hydroxyl radicals (HO•) and 1O2 is negligible. In addition, the presence of HCO3−, benzoic acid (BA) and phenol shows a negative effect on the oxidation of HEDP in the Cu(II)/PMS process. However, in the actual wastewater, the removal efficiency of HEDP in the Cu(II)/PMS process is much higher than that in other free radical processes (i.e., UV/H2O2, UV/PDS). This study provides a new idea for the removal of phosphonates from actual wastewater.