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

    • 摘要: 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60 min,榕树叶-活性污泥体系对初始质量浓度为100 mg/L的UO2+2的吸附率超过99%,室温20 ℃下最大吸附量达到13.055 mg/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=-45.2 kJ/mol, ΔS=-46.2 J/(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。

       

      Abstract: 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 adsorption 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.

       

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