Removal of cadmium heavy metal ions from wastewater by electrosorption using modified activated carbon felt electrodes

Abstract Cadmium contamination in industrial wastewater is an environmental issue posing a great threat to human and animal life. However, the available methods for the removal of cadmium at lower concentrations are limited. Such processes are often accompanied by sludge formation and lead to heavy metal wastage. This paper focuses on the application of an electrosorption process using modified activated carbon felt (MACF) electrodes for the removal and recovery of lower concentration of cadmium from a simulated wastewater sample without sludge formation. Activated carbon felt (ACF) electrodes were treated with 20% HNO3 for removing surface impurities and improving the surface area. The effect of the electrode modification was analyzed by performing various characterizations including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and cyclic voltammetry. The adsorption isotherm and kinetic models have also been studied. The effect of operating parameters including pH, voltage, initial concentration and time were analyzed and optimized using Box-Behnken design and were obtained as 6.42, 1.44 V, 0.50 mg/L and 131.51 min respectively. During the regeneration of electrodes, a concentrated cadmium solution of 18.55 mg/L was obtained, which showed the possibility of cadmium recovery. The maximum cadmium removal was 60.60% at the optimized conditions, revealing the significance of electrosorption for heavy metal treatment.