Efficient denitrification and removal of natural organic matter, emerging pollutants simultaneously for RO concentrate based on photoelectrocatalytic radical reaction

摘要

Reverse osmosis (RO) concentrate becomes a new knotty problem in water treatment for its high concentrated salts and complex pollutants. In this study; we presented a photoelectrocatalytic (PEC) chloride-radical (Cl-center dot) system to efficiently remove its pollutants including total nitrogen, natural organic matter and emerging pollutants simultaneously in taking advantage of pre-existing chloride and sulfate salts as electrolytes. NH4+ -N, humic acid and emerging pollutants of nitrosodiethylamine and bisphenol A were used as model pollutants. A WO3 vertical bar[Pd- Cu/NF] electrode couples were used in the PEC system. HO center dot and Cl-center dot radicals were generated on the surface of WO3 photoanode. Organics including humic acid and emerging pollutants were degraded by HO center dot, and NH4+-N was efficiently oxidized to N-2 with the selective reaction of Cl-center dot and NH4+ , (NO3-)-N-center dot -N overoxidized from NH4+-N was selectively reduced to N-2 on [Pd-Cu/NF] cathode. The results showed that the total nitrogen (TN) and total organic carbon (TOC) removal rate were 99.90% and 50.95% in 180 min for the model RO concentrate with 28 mg/L NH4+-N and 20 mg/L humic acid. The emerging pollutants including nitrosodiethylamine and bisphenol A performed removal rates of almost 100%. This study offers a novel, efficient and eco-friendly PEC ,system for deep purification of RO concentrate.