Discoloration of wastewater in a continuous electro-Fenton process using modified graphite electrode with multi-walled carbon nanotubes/surfactant

Abstract

In this study the application of the modified graphite electrode using multi-walled carbon nanotubes accompanied by a cationic surfactant (Cetyl Trimethyl Ammonium Bromide) was evaluated for the removal of two acid dyes from both single and binary dye solutions by Electro-Fenton (EF) process in a continuous reactor. In this regard, the electrodes were coated with nanotubes and used as the cathode electrode to produce H2O2in situ in the dye solution. The effect of important parameters including the current intensity, pH, initial dye concentration and Fe3+ dosage on the removal efficiency was investigated for the electrochemical process when modified and unmodified graphite electrodes were used as the cathode. Also, the kinetic study demonstrated convincingly that the EF process had followed the pseudo-second-order kinetic model with high correlation coefficients. The removal process in binary solution was optimized using the Response Surface Methodology (RSM) considering the electrical energy consumption, current efficiency and COD removal other than dye removal efficiency. The classic results indicated that the Fe3+ dosage of 0.1mM, current intensity of 0.18A, and flow rate of 0.33L/h at the pH 3 were the optimum conditions for the removal of 50mg/L of initial dye from solution. Subsequently, it was illustrated that RSM is a proper statistical tool to relate different responses to the variables in order to optimize the removal process.