Evaluation of AC/ZnO composite for sorption of dichloromethane, trichloromethane and carbon tetrachloride: Kinetics and isotherms

The present work reports on the efficiency of activated carbon loaded with zinc oxide nanoparticles (AC/ZnO) for removing dichloromethane, trichloromethane and carbon tetrachloride from aqueous solutions. Waste tires were used as a raw material for the production of activated carbon (AC) by thermo-chemical process. Zinc oxide nanoparticles were loaded into AC by using Zn(NO₃)₂.6H₂O. The AC/ZnO composite has been characterized by BET analyzer, scanning electron spectroscope, energy dispersive X-ray spectroscope, FTIR spectrophotometer, and X-ray diffraction. Batch experiments were conducted under various adsorbent dosages, initial concentrations and contact time. Rapid adsorption was observed with adsorption capacity of 6.67 mg/g for dichloromethane, 11.91 mg/g for chloroform and 16.10 mg/g for carbon tetrachloride. The equilibrium was obtained in 20 min of contact time. The adsorption of these pollutants onto AC/ZnO was described well by the pseudo second-order model, and the hydrophilic fraction adsorption fitted the intraparticle diffusion model. Freundlich and Langmuir models were used to evaluate the process, and the Langmuir adsorption isotherm model fitted the data better than other models. The reusability of the composite was proved when no significant decrease in its adsorption capacity was observed even after several times of regeneration.