关键词: 有机蒙脱土, 吸附, 单宁酸, 动力学, 热力学

Abstract: Organic montmorillonite （OMMT） modified by hydroxyethylhexadecyldimethyl ammonium bromine was prepared through cation exchange with natural montmorillonite（MMT）. Material characterizations before and after the modification were investigated using X-ray diffraction and Fourier transform-infrared （FT-IR） spectroscopy. Batch static experiments of OMMT for tannic acid （TA） were performed on adsorption conditions and mechanism. The adsorption process was strongly pH-dependent and the optimal pH value was 4.0. Adsorption equilibrium was reached at 6 h and the adsorption process followed pseudo-second-order kinetics. The adsorption isotherm was better described by the Langmuir isotherm equations compared to the Freundlich isotherm equations. The maximum adsorption capacity obtained was 181.6 mg/g at pH of 4 when initial TA concentration was 500 mg/L and temperature was 293 K. The thermodynamic parameters of ΔG and ΔH were negative，revealing that the adsorption of TA onto OMMT was a spontaneous and endothermic process. The adsorption capacity of the regenerated OMMT decreased by less than 20% after alternating between saturating adsorption and desorption of TA for seven times.

Key words: organic montmorillonite （OMMT）, adsorption, tannic acid （TA）, kinetics, thermodynamics