Visible light enhanced heterogeneous photo-degradation of Orange II by zinc ferrite (ZnFe2O4) catalyst with the assistance of persulfate

•PS promoted ZnFe2O4 catalyst assisted visible light photocatalysis significantly.•The quantum yield (Φ) of photodegradation of Orange II at 454nm was investigated.•Primary reactive species were identified and the degradation mechanism was elucidated.•Main intermediates were identified and a plausible degradation pathway was proposed.•The toxicity of the treated solution was decreased to nearly zero.