Efficient Degradation of Organic Contaminants by Activated Permanganate with Metal Sulfides: In Situ Generation of Mn(III)

Abstract

KMnO 4 activation processes have drawn increasing attention in water decontamination due to the massive generation of highly reactive Mn species. This study surprisingly found that metal sulfides such as molybdenum sulfide (MoS 2 ) and tungsten sulfide (WS 2 ) remarkably enhanced the oxidation of various trace organic contaminants (TrOCs, including antibiotics, pharmaceuticals, and pesticides) by KMnO 4 , with the degradation efficiency increasing to 24.6 ∼ 100% and 17.2 ∼ 100%, respectively. Probe compound oxidation experiments, Mn average valence determination, and UV absorbance spectral analyses suggested that Mn(III) species was the only reactive intermediate in situ formed and responsible for the enhanced contaminant oxidation. KMnO 4 activation with metal sulfides was mainly attributed to reducing S(−II) species, which served as the electron sacrificer for the conversion of MnO 4 − to Mn(III). The KMnO 4 /metal sulfide process exhibited a desirable removal of TrOCs in actual water. Significant degradation of sulfamethoxazole by KMnO 4 /MoS 2 and KMnO 4 /WS 2 was observed in a wide pH range from 3.0 to 9.0. HCO 3 − at a low concentration could enhance the oxidation efficiency, and humic acid (HA) simply showed a small negative impact. Importantly, metal ions leached after KMnO 4 /MoS 2 and KMnO 4 /WS 2 oxidation could be removed by the subsequent coagulation process. The results demonstrated that the KMnO 4 /metal sulfides process may be an alternative Mn(III)driven oxidation technology to remove organic contaminants for water remediation.