Natural manganese sand activates sodium hypochlorite to enhance ionic organic contaminants removal: Optimization, modeling, and mechanism.

ABSTRACT

Although sodium hypochlorite acting as an oxidant has been investigated for the role it plays in the degradation of organic contaminants, little attention has been paid to its activation and efficient utilization. In this study, natural manganese sand (NMS) was verified to be effective for activation of sodium hypochlorite (NaClO). Due to the generation of O2-, the removal efficiency of ionic organic contaminants in NMS/NaClO system was 1.9-4.1 times higher than that in NMS or NaClO alone. Hence, NMS activated NaClO system performed ~96.6 % contaminants removal efficiency at a wide pH range (pH 5-9). Kinetic modeling yielded that the NMS dosage was more important than NaClO dosage. Long-term stability was observed in the presence of various salts (bicarbonate, sulfate, phosphate, and chloride). Characterization results revealed that electron transfer among NMS, NaClO, and organic contaminants was responsible for NaClO activation. Then NaClO-based Fenton-like process was proposed by tracing the degradation intermediates of methyl orange (MO) and generations of reactive oxygen species in the MO/NMS/NaClO system. This study presents the potential of NMS to activate NaClO and enhance ionic organic contaminants removal from aquatic environments.