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

► Co3O4 was synthesized with three morphologies to degrade 1,2,4-trichlorobenzene. ► The cabbage-like Co3O4 exhibited the highest reactivity. ► Reaction acts competitively via hydrodechlorination and oxygen-attacking pathways. ► The likely hydrodechlorination pathway was elucidated by theoretical calculation. ► The superoxide anions might cause ring-cracking oxidation of 1,2,4-trichlorobenzene.