The Encapsulation Capacity of Layered Double Hydroxides for Uranium (Vi) Removal Through Adsorption and Photoreduction

Abstract

The synthesis and development of cost-effective and high-efficiency adsorption-photocatalysis bifunctional treatment agent for uranium-containing wastewater. In this work, we successfully synthesized layered double hydroxides (LDHs, NiAl and ZnNiAl) with the different nickel coordination environments and aimed to investigate the adsorption activity and photocatalytic removal performance of uranium (U(VI)) under visible light. The adsorption experimental results showed the adsorption capacity of NiAl was about four times than that of ZnNiAl, and the excellent adsorption property of NiAl originated from its large surface area and surface Ni-OH groups which had high coordination ability toward U(VI). In addition, NiAl had narrower band gap than ZnNiAls due to the electronegativity of Ni2+(1.91) was greater than Zn2+(1.65), and NiAl (0.055 h-1) exhibited the higher efficiency of U(VI) photoreduction than ZnNiAl (0.0138 h-1) under visible light. Thus, NiAl showed dual properties, adsorption and photoreduction. In the process of photocatalysis, the photogenerated electrons and generated •O2- radical could reduce the absorbed U(VI) into insoluble UO2(s) and U3O8. Consequently, photocatalytic reduction could further improve the performance of NiAl in removing U(VI) from solution. In conclusion, NiAl with the low cost and disposal simplicity could be exploited for decontamination of U(VI), involving surface complexation and photocatalytic reduction.

Keywords: LDHs, U(VI), Adsorption, Photoreduction