Treatment of 2,4,5-trichlorophenol by MgA1-SDBS organo-layered double hydroxides: Kinetic and equilibrium studies

Clay-based adsorbents were synthesized by incorporating anionic surfactants sodium dodecylbenzenesulfonate (SDBS), into calcined magnesium aluminum layered double hydroxide (MgA1-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 angstrom, which is larger than that of MgA1-CO3. The product which is an organophilic layered double hydroxide or organo-LDH (MgA1-SDBS) was examined for their ability to adsorb organic pollutant. The adsorption of 2,4,5-trichlorophenol (TCP) from aqueous solutions by MgA1-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 Delta G degrees and the positive value of Delta H degrees indicate the spontaneous and endothermic nature of the process. (C) 2011 Elsevier B.V. All rights reserved.