Removal of 2,4,6-trichlorophenol from water and petroleum refinery industry effluents by surfactant-modified bentonite

The applicability of surfactant-modified bentonite (SMB) for removing 2,4,6-trichlorophenol (TCP) from water and petroleum refinery industry effluents has been investigated through a batch adsorption process. The adsorbent was prepared from Na-bentonite by exchanging Na+ ions with the cationic surfactant, hexadecyltrimethyl ammonium (HDTMA) chloride. The adsorption capacity for TCP was significantly enhanced by 2.3 times through surfactant treatment of the bentonite. The effect of pH, Initial concentration, contact time, adsorbent dose, ionic strength and temperature on adsorption of TCP was investigated. A strong dependence of the adsorption capacity on pH was observed, the capacity increasing as the pH value decreased. The long alkyl chains of intercalated HDTMA increased the hydrophobicity of the adsorbent and provided particular affinity for TCP molecules. The adsorbent showed high efficiency towards TCP and >99.0% removal was achieved from an initial concentration of 10 μmol/L at pH 3.0. The kinetics of the adsorption process was described by a pseudo-first-order model. Film diffusion was found to be the rate-limiting step. The adsorption isotherm was consistent with the Langmuir adsorption isotherm, and maximum monolayer capacity of the adsorbent was found to be 70.42 μmol/g at 30 °C, which was higher than that of commercial activated carbon (52.63 μmol/g). The adsorbed TCP can be recovered by using 0.1 M NaOH. The regeneration process was carried out in four cycles and results indicate minimum loss in adsorption capacity.