The degradation of 1,2,4-trichlorobenzene using synthesized Co3O4 and the hypothesized mechanism

Abstract

Co(3)O(4) was synthesized with cabbage-like, plate-like and sphere-like morphologies. The effect of different morphologies on the degradation of 1,2,4-trichlorobenzene (1,2,4-TrCB) was evaluated, and the cabbage-like Co(3)O(4) exhibited the highest reactivity. The degradation of 1,2,4-TrCB on the cabbage-like Co(3)O(4) is hypothesized to act competitively via hydrodechlorination and oxygen-attacking pathways. By the hydrodechlorination pathway, 1,2,4-TrCB is successively dechlorinated into the three dichlorobenzenes (DCBs) and then monochlorobenzene (MCB). The yield of the DCBs was in the order of p-DCB>m-DCB>o-DCB, which can be explained by the calculated C-Cl bond dissociation energies in 1,2,4-TrCB and DCBs. Derivatization and electron spin resonance experiments identified that lattice oxygen and superoxide anions may take part in the oxidation pathway. The lattice oxygen initiated a partial oxidation of 1,2,4-TrCB, leading to the formation of chlorinated phenols. The superoxide anions caused ring-cracking oxidation of 1,2,4-TrCB, possibly producing some low-molecular-weight products, thus explaining a mass imbalance in the chlorine atoms and total organic carbon.