有机蒙脱土对单宁酸的吸附性能

Adsorption of tannic acid using organic montmorillonite

利用十六烷基二甲基羟乙基溴化铵对钠基蒙脱土(MMT)进行离子交换改性,制得有机蒙脱土(OMMT),并通过FT-IR、XRD对MMT改性前后的结构进行表征。通过静态吸附试验,探究OMMT对单宁酸(TA)的吸附条件和吸附机理。结果表明,OMMT吸附TA对pH值有较大的依赖性,吸附最佳pH值在4.0左右;吸附平衡时间为6h,吸附动力学曲线符合准二级动力学模型;吸附等温线用Langmuir方程比Freundlich方程能更好地描述;在pH值为4.0、TA初始浓度为500 mg/L、温度为20℃时,最大吸附容量为181.6mg/g;热力学参数ΔG、ΔH均为负值表明吸附为自发的放热过程。在饱和吸附和解吸重复7次后,再生OMMT吸附容量下降不到20%。

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.