ELECTROCHEMICAL OXIDATION OF REACTIVE DYE GREEN HE4BD USING SOLAR ENERGY

摘要

Cotton represents approximately half of all textiles worldwide and nearly all cottons are dyed today by reactive dyes. Reactive dye effluents are the most important pollution source in the textile industry. Hence a choice of suitable treatment method is in order, which can effectively treat pollutants without expensive chemical addition, sludge production and also cost effective. Electrochemical technology is one such technology, which can offer the above advantages. Electrochemical technology is an easy-operated 'green' technology that can easily be integrated with non-conventional energy sources like solar energy ( using solar panels) for driving the electrochemical reactions. Thus the technology can be used at no operating cost being environmentally and also economically friendly, leading to sustainable water treatment practices. The electrochemical degradation of a commonly used textile dye- Reactive Green HE4BD using solar energy was investigated in this study. The study involved electrochemical oxidation of dyes using Titanium anode coated with Titanium, Ruthenium and Iridium oxides (Ti/TiO_2-RuO_2-lrO_2). The treatment of the dye solutions were followed by analyzing the colour and TOC (Total organic carbon) of the samples obtained at frequent intervals. The effects of variations of process parameters such as electrolyte concentration, current density, pH of the solution, and the initial dye concentration were studied on dye degradation. The electrolytic experiments were carried out in the presence of sodium sulphate as electrolyte since it does not involve the possibility of formation of toxic organochlorine compounds. From the experiments conducted, the optimum dye degradation conditions were found to be at pH 9, sodium sulphate concentration of 0.01 M and a current density of 5.4 A/ dm~2. The results also showed that the treatment time increased and mineralisation efficiency decreased at higher pollutant concentration. It was however observed that complete colour removal can be achieved with all concentration of dyes. At optimal conditions of dye degradation complete colour removal and significant reduction in TOC were achieved within 5 hours of active treatment. The kinetics of the process was evaluated and the degradation of the dye followed pseudo-first order reaction. At the end of 5 h during the treatment of 1500 mg/L of the dye the rate constant of the reaction was found to be 1.22 h~-1 with the fractional conversion of pollutant being 0.99 and the anodic efficiency of the process being 9.26 Kg (Dye_r)A~-1 h~-1m~-2 respectively.