Visible light is efficient to induce As(III) oxidation in Fe(III)/sulfite system.
High oxidation and removal rates of As(III) is achieved at pH 6.
Mechanism of As(III) oxidation involved both hydroxyl and oxysulfur radicals.
As(III) can sorb to Fe-particles and then be oxidized through LMCT process.
Sequential addition of sulfite is beneficial to improve the As(III) oxidation.