改性树脂吸附硼的动力学和热力学研究

Kinetic and Thermodynamic Study of Boron Adsorption by Modified Resin

通过接枝法成功制备了酚羟基型改性树脂,选用典型的动力学方程、热力学方程以及非线性两参数的4种等温吸附模式对改性树脂吸附硼的试验数据进行拟合,从动力学和热力学角度分析并揭示改性树脂对硼的吸附特征和吸附机理。结果表明:伪二级动力学吸附模式可较好地描述改性树脂对硼的动力学吸附过程;在3种不同温度下的自由能变(ΔG)分别为-5.44kJ/mol、-6.32kJ/mol、-4.01kJ/mol,焓变(ΔH)为-6.43kJ/mol,均小于零,活化能(E)为11.06kJ/mol,说明该吸附过程为可自发进行的放热反应,是基于树脂表面试钛灵的邻羟基与硼酸分子发生配位反应的、以化学吸附为主的物理化学吸附过程;非线性两参数的4种等温吸附模式对改性树脂吸附硼的吸附试验数据拟合结果显示该吸附过程最符合Langmuir等温吸附模式,且在25℃条件下改性树脂对硼的吸附量最高达20.87mg/g。

The phenolic hydroxyl functional groups modified resin is synthesized by grafting method.In order to reveal the adsorption characteristics and the adsorption mechanism of boron on the modified resin from kinetics and thermodynamics,four kinds of adsorption isotherm models including typical kinetic equations,thermodynamic equations,and adsorption isotherm models with two parameters are used to fit the test boron adsorption data.Results show that the kinetic adsorption process can be well described by pseudo-second-order kinetic adsorption model.The change of free energy(ΔG)at three different temperatures are-5.44kJ/mol,-6.32kJ/mol and-4.01kJ/mol,the change of adsorption enthalpy(ΔH)is-6.43 kJ/mol,all of which are less than zero.The activation energy(E)is 11.06kJ/mol,indicating that the adsorption process is a spontaneous,exothermic reaction,which is a physical-chemical process dominated by chemical adsorption,and is mainly based on a coordination reaction between the hydroxyl functional groups of the terone on surface of the resin and the boric acid molecule.The fitting result of boron adsorption data of modified resin with the four nonlinear two-parameter adsorption isotherm models show that the adsorption process conforms to Langmuir adsorption isotherm model,and the maximum boron adsorption capacity of modified resin can reach 20.87mg/g under the condition of 25℃.