Removal of cadmium and lead from aqueous solutions by magnetic acid-treated activated carbon nanocomposite

In this study, a new approach was developed for the preparation of magnetic activated carbon (MAC) in which a nanocomposite with the mass ratio of 1:8 (Fe3O4:AC) was prepared using commercial activated carbon (AC) treated with nitric acid and magnetite nanoparticles synthesized by co-precipitation method. The MAC was characterized by scanning electron microscopy, nitrogen adsorption isotherm at 77 K, vibrating sample magnetometer, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that MAC had desirable magnetic properties and pure Fe3O4 nanoparticles were successfully synthesized and added to AC. The nanocomposite was successfully used as a separable adsorbent for removing Pb2+ and Cd2+ from aqueous solutions. The adsorption performances were evaluated by Langmuir and Freundlich isotherms, which showed the data were well fitted to the Langmuir model. The adsorbent showed good adsorption capacities of 49.8 and 86.2 mg/g for cadmium and lead at the initial pH levels of 6.0 and 5.0, respectively. Kinetic studies were performed using pseudo-first-order and pseudo-second-order kinetic models and the results demonstrated that the adsorption process followed second-order model. Thermodynamics of the adsorption of lead and cadmium onto MAC was also studied with results that showed the adsorption process was endothermic and spontaneous. Adsorption performance of MAC was also evaluated using battery manufacture wastewater samples and removal efficiencies of 91.4 and 96.6% were obtained for the removal of Cd2+ and Pb2+, respectively.