Optimization of electrochemical pathways for dyeing wastewater treatment in continuous-flow divided cell

Environmental concerns have been arisen from entrance of a significant fraction of synthetic dyes by discharging textile effluents. Reactive dyes based on azo chromophores as the most common colorants used in textile industry cannot be easily removed through many of the treatment methods mainly because of their complex aromatic structure. In many studies, potentiality of electrochemistry approach to deal with industrial pollutions has been actualized. This work was focused on finding the optimum operating conditions of dye removal using continues flow electrochemical cell through oxidation and reduction mechanisms. The graphite and stainless steel were applied as anode and cathode, sodium chloride and Reactive Red 120 (RR120) were used as supporting electrolyte and model dye, respectively. Reactor was divided by cellulosic separator and operated in continuous flow mode. CCD of Design Expert7 was considered for designing the experiments, analyzing data and optimization. Accordingly, the effects of initial dye concentration (100-500 ppm), electrolysis time (20-90 min), and current intensity (0.1-0.4 A) as variables governing the efficiency of the process were studied through a set of repeated experiments. The maximum removal of color 98.14% was achieved at 90 min of electrolysis time using 0.25 A of current intensity in a solution containing 300 ppm of dye. In effluent with same concentration under same current density, decreasing reaction time from 90 to 55 min reduced the efficiency about 5%. Electrolysis time was the most influential factor on response. 1.67 to 13.2 Kwhm-3 of electrical energy was consumed in experiments. 87.6% removal rate was observed under optimum conditions with consumption of only 6.55 kwhm-3 of electrical energy. Current research confirmed that applying electrochemical mechanisms in cell proposed by this study was an effective methode for optimized removal of RR120 from simulated dyeing wastewater.

Keywords:

Electrochemical Oxidation , Electrochemical Reduction , Optimization , Reactive Red 120