Department of Chemistry, University of Kerala, Kariavattom, Trivandrum 695581, Kerala, India.
J Environ Radioact. 2012 Apr;106:8-19. doi: 10.1016/j.jenvrad.2011.10.013. Epub 2011 Nov 24.
A novel adsorbent poly(methacrylic acid)-grafted chitosan/bentonite (CTS-g-PMAA/Bent) composite was prepared through graft copolymerization reaction of methacrylic acid and chitosan in the presence of bentonite (Bent) and N,N'- methylenebisacrylamide as a crosslinker. The composite was well characterized using FTIR, XRD, XPS, SEM-EDS, surface area and zeta potential analyzers. The adsorption behavior of the composite toward uranium(VI) from aqueous media was studied under varying operating conditions of pH, concentration of U(VI), contact time, adsorbent dose and temperature. The optimum pH range for U(VI) adsorption was 5.5 at 30 °C. Concentration and temperature dependent rate constants were evaluated using pseudo-second-order kinetic model. The equilibrium data were correlated with the Langmuir isotherm model with an endothermic behavior. The equilibrium U(VI) sorption capacity was estimated to be 117.2 mg g(-1) at 30 °C. For the quantitative recovery of 100 mg L(-1) U(VI) from 1.0 L simulated nuclear industry wastewater, a minimum adsorbent dosage of 2.0 g CTS-g-PMAA/Bent was required. The calculated energy of activation (E(a) = 47.83 kJ/mol) was positively correlated with chemical adsorption process. The values of enthalpy, entropy and free energy of activation were calculated to explain the nature of adsorption process. Adsorption-desorption experiments over four cycles illustrate the feasibility of the repeated uses of this composite for the extraction of U(VI) from aqueous solutions.
一种新型吸附剂聚（甲基丙烯酸）接枝壳聚糖/膨润土（CTS-g-PMAA/Bent）复合材料是通过在膨润土（Bent）和 N,N'-亚甲基双丙烯酰胺存在下，用甲基丙烯酸和壳聚糖进行接枝共聚反应制备的。采用 FTIR、XRD、XPS、SEM-EDS、比表面积和zeta 电位分析仪对复合材料进行了很好的表征。研究了在不同的操作条件下，即 pH 值、U(VI)浓度、接触时间、吸附剂剂量和温度，该复合材料对水溶液中铀（VI）的吸附行为。U(VI)吸附的最佳 pH 范围为 30°C 时的 5.5。使用拟二级动力学模型评估了浓度和温度依赖性的速率常数。平衡数据与 Langmuir 等温线模型相关联，表现出吸热行为。在 30°C 时，平衡 U(VI)吸附容量估计为 117.2mg g(-1)。为了从 1.0 L 模拟核工业废水中定量回收 100mg L(-1)的 U(VI)，需要使用 2.0 g CTS-g-PMAA/Bent 的最小吸附剂剂量。计算出的活化能（E(a) = 47.83 kJ/mol）与化学吸附过程呈正相关。计算了焓、熵和活化自由能的值，以解释吸附过程的性质。经过四个循环的吸附-解吸实验，说明了该复合材料从水溶液中提取 U(VI)的重复使用的可行性。
