Silica nanoparticles loaded on activated carbon for simultaneous removal of dichloromethane, trichloromethane, and carbon tetrachloride

The low efficiency of carbon derived from low-cost materials limits its industrial application as a low-cost adsorbent for the removal of contaminants from wastewaters. In this work, silica nanoparticles were loaded on activated carbon to produce an activated carbon/silica (AC/SiO₂) composite. The product was characterized by means of thermogravimetric analyzer, scanning electron spectroscope, energy dispersive X-ray spectroscope, FTIR spectrophotometer, and X-ray diffraction. The AC/SiO₂ was found to have a higher thermal stability than the AC. The XRD pattern of AC/SiO₂ demonstrated that the AC was loaded with crystalline SiO₂ as a tetragonal phase. For the removal of dichloromethane, chloroform and carbon tetrachloride, the operational parameters of contact time, initial concentrations and adsorbent dosage were optimized. The adsorption capacity increased with a decrease in the initial hydrocarbon concentrations. The experimental data were fitted to Langmuir, Freundlich, and Temkin isotherms, and pseudo-kinetic models. The Langmuir isotherm provided a better fit to the experimental data, assuming that adsorption takes place at specific homogenous sites within the adsorbent. The adsorption kinetics better fitted the pseudo-second order. The results of recycling tests demonstrate the excellent potential of adsorbents for pollutant removal.