Optimization of three-dimensional electrochemical process for degradation of methylene blue from aqueous environments using central composite design

Using the various electrodes, conditions and cell design, the effectiveness of electrochemical processes in removal of various pollutants is different. In this regard, the present study aimed to achieve optimal conditions and maximum efficiency for decolorization methylene blue (MB) from aqueous solution. For this purpose, a three-dimensional (3D) electrochemical process with low-cost electrodes was used. To investigate the influence of effective factors on the MB decolorization process such as dye concentration, pH, contact time, current intensity and electrode distance were optimized using the response surface methodology (RSM). The analyses of chemical oxygen demand (COD), total organic carbon (TOC) and volumetric studies were performed to evaluate the efficacy of the studied processes for removing organic matter and intermediate products. In addition, the efficiency of two two-dimensional (2D) and 3D electrochemical methods for optimum decolorization of MB was compared. Under the optimal conditions including pH of 7.6, current density of 23 mA∕cm2, electrodes distance of 3 cm, time of 60 min and initial dye concentration of 0.155 g/L, the decolorization efficiency rates using the 3D and 2D processes were 94.7 and 83.7%, respectively. The removal efficiencies of COD and TOC using the 3D process were 87.5 and 83.0%, respectively, and using 2D process were 76 and 71.7%, respectively. Voltammetry studies illustrated that MB and formed intermediates had been degraded completely. All this makes it a suitable measure to be considered as a cost-effective process for wastewaters containing MB.