A first pre‐pilot system for the combined treatment of dye pollutants by electrocoagulation/ EAOPs

BACKGROUND Based on promising results obtained at laboratory scale with a two‐step electrochemical treatment of Tartrazine solutions by electrocoagulation ( EC ) coupled with electrochemical advanced oxidation processes ( EAOPs ), this work addresses its scale‐up to degrade 1.85 dm 3 of solutions of this dye. Monopolar and bipolar configurations have been compared in EC . The effect of supporting electrolyte, pH , applied current, dye concentration and electrolysis time has been assessed. RESULTS Electrocoagulation with four Fe electrodes was first optimized for the treatment of 278 mg dm −3 Tartrazine solutions. The bipolar series configuration led to enhanced coagulation due to the larger electrode consumption. Solutions with 0.05 mol dm −3 NaCl at pH 6.3 were quickly decolorized with 60% total organic carbon removal, being more convenient than Na 2 SO 4 and NaNO 3 electrolytes due to the synergistic action of coagulation and oxidation by active chlorine. Among the EAOPs , carried out with a Ti/ IrO 2 ‐RuO 2 anode and an air‐diffusion cathode to electrogenerate H 2 O 2 , electro‐Fenton ( EF ) with 0.5 mmol dm −3 Fe 2+ was much better than electro‐oxidation owing to the oxidative action of active chlorine and • OH formed in the bulk from Fenton's reaction. Photoelectro‐Fenton ( PEF ) was even better by the additional photolysis of by‐products under incident UVA photons. CONCLUSIONS The use of an EC reactor in bipolar configuration for 12.5 min at 1.50 A followed by PEF treatment for 360 min at 1.50–2.00 A ensured mineralization >90%, which encourages further optimization at larger scale for the treatment of a variety of organic pollutants in real wastewaters. © 2014 Society of Chemical Industry