Ozone assisted electrocoagulation in a rectangular internal-loop airlift reactor: Application to decolorization of acid dye

Decolorization of synthetic wastewater containing Acid Brown 214, a typical triazo acid dye, was carried out by ozone assisted electrocoagulation as an advanced oxidation process. Ozonation and electrocogulation were performed simultaneously in the riser and downcomer sections of a lab-scale rectangular airlift reactor, respectively, where ozonated gas had no influence on dielectric constant. A good mixing was achieved with the liquid circulation induced by gaseous ozone, without the need of mechanical mixing. Taguchi experimental design method with orthogonal arrays L27 and the “larger is better response” category were applied to determine optimum conditions for dye removal. The operating variables considered were the initial pH, initial dye concentration, salt concentration, current density, superficial gas velocity and decolorization period with three levels. Under optimum conditions, the synergistic effect of the combined process reaching complete decolorization in 30 min with energy consumption 7.4 kWh/kg dye removed. Results indicated that combination process in innovative configuration of single airlift reactor is cost effective as compared with that obtained individually in separate conventional reactors.