Khalili Fawwaz, Al-Banna Ghadeer
The University of Jordan, Chemistry Department, Amman, Jordan.
J Environ Radioact. 2015 Aug;146:16-26. doi: 10.1016/j.jenvrad.2015.03.035. Epub 2015 Apr 15.
Humic acid from Ajloun soil has been extracted and insolubilized. The insolubilized humic acid (NaIHA) was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermal gravimetric analysis, X-ray diffraction and differential scanning calorimetry. Adsorption of U(VI) and Th(IV) by NaIHA was studied using batch technique at different temperatures (25.0, 35.0 and 45.0 °C) and at different pH values (1.00, 2.00 and 3.00). It was found that NaIHA has higher uptake for Th(IV) than U(VI), and that the metal ion uptake by NaIHA increased with pH and reached a maximum at pH = 3. The kinetic studies were done, and showed that the equilibrium time for each metal ion occurs at 6 h to achieve maximum uptake level. Adsorption data were evaluated according to the Pseudo second-order reaction kinetic. The metal ions uptake properties by the NaIHA fit Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. Thermodynamic functions, ΔG°, ΔH° and ΔS° were determined for each metal ion. The positive values of ΔG° indicate that adsorption process is not highly favorable, while ΔH° values indicated that this process is endothermic. On the other hand, the process has positive entropy which means that the adsorption process increases the disorder of the system and it is entropy driven. Column experiments were used for the determination of metal ion loading capacity and desorption studies. The uptake capacities in column technique of U(VI) and Th(IV) ions are 2.63 and 4.85 mg metal ion/g NaIHA respectively. Recovery of U(VI) and Th(IV) ions was carried out by treatment of loaded insolubilized humic acid with 0.1 M and 1.0 M HNO3, the best recovery for U(VI) and Th(IV) ions were obtained when 1.0 M HNO3 was used.
已从阿杰伦土壤中提取并使腐殖酸不溶解。通过傅里叶变换红外光谱、元素分析、热重分析、X射线衍射和差示扫描量热法对不溶性腐殖酸（NaIHA）进行了表征。采用分批技术研究了NaIHA在不同温度（25.0、35.0和45.0℃）和不同pH值（1.00、2.00和3.00）下对U(VI)和Th(IV)的吸附。结果发现，NaIHA对Th(IV)的吸附量高于U(VI)，且NaIHA对金属离子的吸附量随pH值升高而增加，在pH = 3时达到最大值。进行了动力学研究，结果表明每种金属离子的平衡时间为6小时，以达到最大吸附水平。根据伪二级反应动力学对吸附数据进行了评估。NaIHA对金属离子的吸附特性符合朗缪尔、弗伦德利希和杜比宁-拉杜舍维奇吸附等温线。测定了每种金属离子的热力学函数ΔG°、ΔH°和ΔS°。ΔG°的正值表明吸附过程并非非常有利，而ΔH°值表明该过程是吸热的。另一方面，该过程具有正熵，这意味着吸附过程增加了系统的无序度，是由熵驱动的。采用柱实验测定金属离子负载量并进行解吸研究。柱技术中U(VI)和Th(IV)离子的吸附容量分别为2.63和4.85 mg金属离子/g NaIHA。通过用0.1 M和1.0 M HNO3处理负载的不溶性腐殖酸来回收U(VI)和Th(IV)离子，使用1.0 M HNO3时获得了U(VI)和Th(IV)离子的最佳回收率。
