Mg/Al LDH对UO22+的高效吸附研究

由于放射性污染物的不合理处置及核泄漏事件的发生,对生态环境和人类健康造成了严重危害.本研究采用共沉淀法制备了不同Mg/Al比(物质的量比)的Mg/Al LDH(层状双氢氧化物),研究其对UO_2~(2+)的吸附行为.同时,考察了吸附剂投加量、p H、吸附时间、初始浓度对吸附的影响,并采用XRD、FTIR、SEM、XPS等技术对吸附前后LDH材料进行表征与分析.结果表明:Mg/Al比为2∶1的Mg/Al LDH对UO_2~(2+)吸附效果要比Mg/Al比为4∶1的Mg/Al LDH好,Mg/Al比为2∶1和4∶1的Mg/Al LDH对UO_2~(2+)吸附容量分别为301.28和263.85 mg·g-1,对UO_2~(2+)具有优良的吸附性能,可以作为高浓度放射性污染废水的吸附材料和核泄漏事件的应急吸附材料.Mg/Al LDH对UO_2~(2+)的吸附更符合Langmuir等温吸附模型和Pseudo-second-order动力学模型.吸附后Mg/Al LDH的Mg/Al比降低,Mg/Al LDH对UO_2~(2+)的吸附机理是UO_2~(2+)与材料中氢氧根、碳酸根相互作用,形成三元的络合物而被去除.

The efficient adsorption of UO22+ by Mg/Al layered double hydroxides (LDH)

Because of the unreasonable disposal of radioactive waste and the leakage of nuclear accident, a large amount of radioactive contaminant has been released into environment, which is harmful to the ecological environment and human health. Consequently, it is necessary to develop an efficiency and economical method for treating this kind of pollutants. In this study, Mg/Al layered double hydroxide (LDH) with Mg/Al molar ratios of 2:1 and 4:1 prepared by co-precipitation were used for studying the adsorption behavior of UO₂²⁺ in aqueous solution. Batch experiments were carried out to investigate the effects of contact time, adsorbent dosage, pH value and initial concentration on the adsorption performance of UO₂²⁺ by Mg/Al-2 LDH, Mg/Al-4 LDH. Moreover, the characteristics of the Mg/Al LDH before and after adsorption were determined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, The Brunner-Emmet-Teller (BET) specific surface area, X-ray photoelectron spectroscopy (XPS). The results showed that UO₂²⁺ removal by Mg/Al-2 LDH was better than Mg/Al-4 LDH, and the maximum adsorption capacities were 301.28 mg·g^-1 and 263.85 mg·g^-1, respectively. The adsorption of UO₂²⁺ by the Mg/Al-2 LDH, Mg/Al-4 LDH could be well described by Langmuir model and pseudo-second-order model. The mechanisms of the adsorption of UO₂²⁺ onto the Mg/Al-2 LDH and Mg/Al-4 LDH were mainly via chemical complexation. Overall, Mg/Al LDH is an efficient absorbent for the UO₂²⁺ adsorption, and it could be used for the adsorption of radioactive contaminated wastewater with high concentration and as an emergency adsorption material for nuclear leaking.