Electrocoagulation-floatation assisted pulsed power plasma technology for the complete mineralization of potentially toxic dyes and real textile wastewater

Abstract

In this study, experiments were conducted for the treatment of textile wastewater containing- a diazo dye i.e. Congo Red dye (CR) and a basic dye Methylene Blue (MB). Performances of Electrocoagulation-Flotation (EC-F) and Pulsed Power Plasma Treatment (PPT) technologies were evaluated individually and in combination. The effects of various parameters such as electrolysis time, electrical conductivity (EC, mS/cm), current density (mA/cm2) and initial concentrations of dye were experimentally optimized to get high removal efficiency. Using EC-F alone, the dye concentration was reduced from 50 mg/L to BDL (below detection level) and 50 mg/L to 3.1 mg/L for CR and MB dyes, respectively at a current density of 14.2 mA/cm2, electrical conductivity 8 mS/cm. To achieve this, an electrolysis time of 2 and 14 min were employed for CR and MB, respectively. To mitigate the problems of passivation of electrodes and sludge formation, EC-F was integrated with PPT treatment system. Also, the removal efficiencies of both the systems were evaluated by treating mixed dyes and real textile wastewater. It was found that by giving a partial treatment in EC-F followed by PPT was able to achieve 100% (TOC) degradation of MB with a total energy consumption of 50.55 kW h/kg dye removed and 39.3 kW h/kg dye for CR. The complete (100%) mineralization of the pollutant was achieved without any chemical addition and no waste (sludge) was produced at the end of novel hybrid treatment. The total treatment cost was reduced by 41.2% (86.04 kW h/kg dye to 50.55 kW h/kg dye) for MB and 30.7% (56.7 kW h/kg dye to 39.3 kW h/kg dye) for CR in hybrid system as compared to PPT treatment alone. Hybrid treatment was found to be an economical and a reliable technology for treating textile industry wastewater.