Treatment of 2,4,5-trichlorophenol by MgAl–SDBS organo-layered double hydroxides: Kinetic and equilibrium studies

Abstract

Clay-based adsorbents were synthesized by incorporating anionic surfactants sodium dodecylbenzenesulfonate (SDBS), into calcined magnesium aluminum layered double hydroxide (MgAl–C) via ion exchange. The sample has been characterized by powder X-ray diffraction, FT-IR spectroscopy and B.E.T measurement. The result shows that SDBS adsorption on the calcined phase is enhanced by reconstruction of a matrix hydrotalcite intercalated by the dodecylbenzenesulfonate with basal spacing of 30 Å, which is larger than that of MgAl–CO 3. The product which is an organophilic layered double hydroxide or organo-LDH (MgAl–SDBS) was examined for their ability to adsorb organic pollutant. The adsorption of 2,4,5-trichlorophenol (TCP) from aqueous solutions by MgAl–SDBS hydrotalcite was investigated in a batch mode. The influence of solution pH, initial TCP concentration and temperature has been tested in kinetic runs. The results showed that the kinetic adsorption could be described by a pseudo-second order model very well. The equilibrium isotherm for TCP uptake was fitted to the Langmuir model with correlation coefficient R 2 of 0.998 at low concentrations and 0.992 for all concentrations. Its maximum adsorption amount is 240.5 mg/g from this model, while the real amount is 160 mg/g at 298 K and pH 4. The negative value of Δ G° and the positive value of Δ H° indicate the spontaneous and endothermic nature of the process.