The physical chemistry of uranium (VI) immobilization on manganese oxides

Publication date: Available online 30 January 2020Source: Journal of Hazardous MaterialsAuthor(s): Yiming Ren, Hongliang Bao, Qian Wu, Huaisheng Wang, Tao Gai, Lang Shao, Shaofei Wang, Hao Tang, Yingru Li, Xiangke WangAbstractManganese oxides show strong affinity towards uranium, and have a promising application in uranium immobilization in environmental protection. We successfully synthesized a series of Mn oxide materials of different structures and investigated their U(VI) immobilization performances. The results showed that all Mn oxides share similar sorption capacities per unit surface area, implying similar physical chemistry during immobilization. Among these Mn oxides, α-MnO2 shows the most outstanding performance for uranium uptake (280 mg/g). More detailed studies on interfacial properties of U(VI) on α-MnO2 were performed to elucidate the binding mechanism. The uptake was largely influenced by acidity, but less impacted by ionic strength, indicative of an inner-sphere binding mode. The selectivity for uranium is much higher than other selected metal ions, i.e. Co2+, Ni2+, Eu3+, etc. ATR-FTIR, and EXAFS results showed that in both mild acidic and neutral conditions, U(VI) formed bidentate binuclear structure on α-MnO2, as evidenced by υas(O = U=O) at 912 cm-1 and the number of Mn in U coordination shell. UO2(OH)2 precipitate was found at the molecular level in neutral condition (pH 7-8). The results reveal the physical chemistry in uranium immobilization ...
Source: Journal of Hazardous Materials - Category: Environmental Health Source Type: research