Surfactant modified montmorillonite as a low cost adsorbent for 4-chlorophenol: Equilibrium, kinetic and thermodynamic study

Abstract

Chlorophenols are toxic, mutagenic and carcinogenic compounds that must be removed before discharging into the environment. In this study, montmorillonite (Mt) modified with two cationic surfactants (hexadecyl trimethyl ammonium bromide, HDTMA, and tetradecyl trimethyl ammonium bromide, TTAB) was used to remove 4-chlorophenol (4-CP) from aqueous solutions. The influence of various factors such as surfactant loading rate, contact time, pH, adsorbate content, solution ion strength and temperature was investigated on the sorption. The sorption uptake of 4-CP was increased by increasing the surfactants loaded onto the Mt up to 150% CEC (cation exchange capacity) of the clay. The contact time of 10 min and 45 min and pH of 11 were found to be as the optimum for the sorption of 4-CP by HDTMA-Mt and TTAB-Mt, respectively. The sorption capacity of 4-CP by the sorbents at the equilibrium was 29.96 mg/g for HDTMA-Mt and 25.90 mg/g for TTAB-Mt. The results also indicated that the Freundlich isotherm model and pseudo-second order kinetic model well described the sorption process than other models. It is obvious that the surfactant modified montmorillonite, especially HDTMA type, in comparison with raw Mt was more efficient sorbent to remove 4-CP from aqueous solutions.