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

摘要

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 0.05mol dm~(-3) NaCl at pH 6.3 were quickly decolorized with 60% total organic carbon removal, beingmore convenient than Na_2SO_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_2O_2, electro-Fenton (EF) with 0.5 mmol dm~(-3) Fe~(2+) wasmuchbetter thanelectro-oxidationowing to theoxidative action of active chlorineand?OHformedin the bulk fromFenton'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 12.5min at 1.50 A followed by PEF treatment for 360 min at 1.50-2.00 A ensuredmineralization >90%, which encourages further optimization at larger scale for the treatment of a variety of organic pollutants in real wastewaters.