Peroxymonosulfate-assisted electro-oxidation/coagulation coupled with ceramic membrane for manganese and phosphorus removal in surface water

Abstract

This study considers peroxymonosulfate (PMS)-assisted iron electrolysis for electro-oxidation/coagulation (EO/EC) pretreatment combined with a ceramic ultrafiltration (UF) membrane for simultaneous manganese (0–1.0 mg/L) and phosphorus (0–0.8 mg/L) removal from surface water. The results indicated that the optimum EO/EC operation conditions appear to be current(I) of 0.2 A with an electrolysis time of 60 s at pH 7.5 (corresponding to nearly 0.5 mg/L Fe2+) under a PMS dosage of 100 µM. Electron paramagnetic resonance (EPR) spectroscopy suggested that sulfate radicals (SO4−) or hydroxyl radicals (OH) were produced during the PMS activation process, and manganese oxide formation after the EO/EC process was elucidated on the basis of the results of X-ray photoelectron spectroscopy (XPS). In addition, EO/EC pretreatment might favour the generation of large flocs and significantly decrease the UF fouling, and SEM-EDS indicated the existence of Mn, P and Fe in the flocs. In real applications, the combined process achieved trace levels of manganese and phosphorous, and membrane fouling was caused by the remaining manganese/ferric oxide. This combined process could treat pollutants in remote regions where electricity supplies are not available.