Enhanced oxidation of aniline using Fe(III)-S(IV) system: Role of different oxysulfur radicals

•SO5− plays a significant role in aniline oxidation in the Fe(III)-S(IV) system.•SO5− oxidizes aniline through direct and indirect pathways.•Aniline oxidation can be effectively enhanced via sequential S(IV) replenishing.•S(IV) replenishing accelerates both the oxysulfur radicals cycle and Fe(III)/Fe(II) cycle.