Synthesis of octyl-modified ordered mesoporous silica as a new nano sorbent for the removal of 2-chlorophenol from aqueous media

Adsorption of 2-chlorophenol onto octyl-modified ordered mesoporous silica material from an aqueous solution was investigated systematically using batch experiments in this study. Hexagonal mesoporous silica (HMS) owning double pore paths and OD-HMS were synthesized by using cheap sodium silicate and a non-ion surfactant C₁₆PyCl under room temperature here and characterized by X-ray diffraction (XRD), N₂ adsorption–desorption measurement, and Fourier Transform-Infrared (FT-IR). Results indicate that 2-chlorophenol adsorption is initially rapid and the adsorption process reaches a steady state after 5 min. The adsorption isotherms are well described by the Langmuir and the Freundlich models, the former being found to provide a better fit with the experimental data. The effects of temperature, pH, ionic strength, and humic acid on the adsorption are also examined. According to the experimental results, the amount of 2-chlorophenol adsorbed decreases with increases of temperature from 288 to 308 K, and pH from 2.0 to 11.0, the amount of 2-chlorophenol adsorbed increases with an increase of ionic strength from 0.001 to 0.1 mol/L. However, the amount of 2-chlorophenol adsorbed onto octyl-modified ordered mesoporous silica material shows notable difference in the presence of humic acid. The desorption process shows a reversibility of 2-chlorophenol adsorption onto octyl-modified ordered mesoporous silica material. Thermodynamic parameters such as Gibbs free energy are calculated from the experimental data at different temperatures. Based on the results, It was found that octyl-modified ordered mesoporous silica shows significant adsorption for 2-chlorophenol. This might be due to hydrophobic interaction among the octyl functional groups and 2-chlorophenol.