榕树叶-活性污泥协同曝气吸附铀的热动力学

Thermodynamic and Kinetics for Synergistic Aeration Adsorption Uranium(Ⅵ) on Banyan Leaves-Activated Sludge

通过吸附动力学实验及等温吸附实验,研究了20～50℃榕树叶-活性污泥协同曝气吸附铀的热动力学性质。结果表明,调节pH=3.0,吸附时间60min,榕树叶-活性污泥体系对初始质量浓度为100mg/L的UO22+的吸附率超过99%,室温20℃下最大吸附量达到13.055mg/g。吸附动力学过程可用准二级吸附速率方程来描述,计算值与实测值吻合良好,相关系数达0.99以上。吸附平衡符合Langmuir和Freundlich等温吸附方程,相关系数都大于0.98,体现了单层吸附与多层覆盖相结合的吸附模式;求得反应的ΔH=-45.2kJ/mol,ΔS=-46.2J/(mol.K),ΔG分别为-31.7(20℃),-31.2(30℃),-30.7(40℃),-30.3(50℃)kJ/mol。根据ΔG<0,ΔH<0及平均吸附能大小判断,榕树叶-活性污泥协同曝气体系吸附铀是自发、放热的物理吸附反应。

Synergistic aeration adsorption of uranium from aqueous solution using banyan leaves（BL） and activated sludge（AS） was investigated by thermodynamic and kinetics batch experiments in the temperature range of 20-50 ℃.The results show that the adsorption ratio of U（Ⅵ） with the initial concentration of 100 mg/L on BL-AS is more than 99%,and the maximal adsorption capacity is 13.055 mg/g for 60 min,at pH=3.0 and 20 ℃.Pseudo 2nd-order model best describes the reaction kinetics;the adsorption capacity calculated by the model is consistent with that actual measured （r2〉0.99）. The experimental data better follow Freundlich isotherm model and Langmuir isotherm model at 20 ℃（r2〉0. 98）. For the whole adsorp- tion process, the enthalpy change is --45.2 kJ/mol, the entropy change is --46.2 J/（mol· K）, and the Gibbs free energy chang is --31.7 （20 ℃）, --31.2 （30℃）, --30.7 （40℃）, --30.3 （50 ℃） kJ/mol respectively, which indicates that the process is spontaneous, radiative, irreversible and physical adsorption process.