谷壳对水中镉离子的吸附动力学及热力学研究

Kinetics and Thermodynamics Study on the Adsorption of Husk to Cadmium Ions in Water

[目的]研究谷壳吸附水中镉离子的吸附过程及其影响因素。[方法]以间歇吸附的方式考察了溶液pH值、反应时间、反应温度、镉离子初始浓度等物化参数对吸附过程的影响,并对吸附过程进行动力学与热力学研究。[结果]吸附过程符合Langmuir吸附等温模式。谷壳对镉离子的吸附动力学模型较好地符合了准二级动力学方程。当反应温度为298 K,pH值为6,谷壳投加量为4 g/L,振荡速度为150 r/min,反应时间为30 min时,谷壳对镉离子的吸附效果最好。随着反应温度的升高,谷壳对镉离子的吸附加快。该吸附反应的焓变值为正,自由能变值为负。[结论]谷壳是处理镉废水的有效的低成本吸附剂,其吸附过程是自发的吸热反应。

[ Objective] The purpose was to study the adsorption process of husk to cadmium ions in water and its influencing factors. [ Method] The influences of physical and chemical parameters such as pH value, reaction time and temperature and the initial cancn, of cadmium ions on the adsorption process were investigated by batch adsorption. And then the adsorption process was studied in kinetics and thermodynamics. [Result] The adsorption process accorded with Langmuir adsorption isothermal model .The dynamic adsorption model of husk to cadmimn ions accorded with quasi-second dynamic equation better. When the reaction temperature was 298 K, pH value was 6, husk addition was 4 g/L, shaking velocity was 150 rpm and reaction time was 30 rain, the adsorption effect of husk on cadmium ions was best. As the reaction temperature increased, the adsorption of husk to cadmium ions was accelerated. The enthalpy change of the adsorption was positive and its flee energy change was negative. [ Conelusionj Husk was a low-cost and effective adsorbent to dispose the wastewater containing cadmium and its adsorption process was spontaneous endothemic reaction.