Decolourization of tartrazine from aqueous solutions by coupling electrocoagulation with ZnO photocatalyst

Decolourization of tartrazine (C.I. Acid Yellow 23, AY23) in aqueous solutions has been investigated by coupling electrocoagulation and ZnO photocatalyst methods and also by a comparison between ZnO, UV, EC, UV/ZnO, UV/EC, and EC/UV/ZnO systems in the removal of AY23 as a model contaminant. Results indicated that the decolourization efficiency was in order of EC/UV/ZnO > UV/EC > EC > UV/ZnO > ZnO > UV. Combining EC with UV/ZnO can trigger the Fenton or Fenton-like reaction, which accelerates the rate of decolourization. Desired operating conditions for decolourization of 40 mg·dm^-3 AY23 solution in EC/UV/ZnO process were [ZnO] ₀=650 mg·dm^-3, [NaCl] = 800 mg·dm^-3, light intensity = 31/2 W·m^-2, current density = 120 A·m^-2, electrodes distance = 15 mm, pH = 6.29, stirring rate = 900 rpm and electrodes of steel 304/A1, which yielded 99.70% colour removal in 5 min of treatment time.