AB24在MgAl-LDO上的吸附性能及机理研究

摘要

本文探讨了nMgAl=3的水滑石焙烧产物(MgAl-LDO)对染料酸性黑24(AB24)的吸附性能及其机理.考察了不同因素对MgAl-LDO吸附AB24性能的影响,并研究了吸附过程的热力学和动力学机理.实验结果表明:MgAl-LDO对AB24具有优异的吸附性能,在298 K,pH=10条件下,1.0g· L-1 MgAl-LDO对1000 mg· L-1 AB24溶液的吸附容量和去除率分别达到998.31 mg ·g-1和99.83％.动力学和热力学研究表明:MgAl-LDO对AB24的吸附过程同时符合Langmuir和Freundlich等温吸附方程,并且是个放热、自发的过程.计算所得的吉布斯自由能绝对值在10～15 kJ·mol-1,这主要是由染料分子与水滑石层板的氢键作用产生,结合Materials Studio 5.5软件模拟AB24染料分子在MgAl-LDHs上的排列分布,推测MgAl-LDO对AB24的吸附机理是表面吸附(占优势)与层间插层的协同作用.同时,该吸附过程符合准二级反应动力学模型.%The adsorption property and mechanism of Acid Black 24 (AB24) on MgAl Layered double hydroxides with Mg/Al molar ratio of 3 were investigated. The results of adsorption experiments indicated that the maximum capacity of AB24 at equilibrium (Qe) and percentage of adsorption (17) with a fixed adsorbent dose of 1.0 g · L-1 were 998.31 mg·g-1 and 99.83%, when concentration of AB24, temperature, and pH were 1 000 mg·L-1, 298 K and 10, respectively. Adsorption isotherms and Kinetics showed that the adsorption process was consistent with both Langmuir and Freundlich equations,it was also spontaneous and exothermic. The Gibbs free energy was calculated to be 10 to 15 kJ·mol-1 because of the Hydrogen bonds between the layer and dye molecular. According to the calculation of Materials Studio5.5, the mechanism of adsorption process was that most AB24 were adsorbed on the surface of MgAl-LDO with part of AB24 intercalated into the layer. The kinetics model has been evaluated to fit the experimental data and it was found that the pseudo-second-order best described the adsorption kinetics of MgAl-LDO to AB24.