Mussel inspired synthesis of U6N@phos-PDA composite adsorbent for the efficient separation of U(VI)

Nuclear energy is considered to be a clean, low-carbon, efficient and sustainable source of energy, which is used in a great variety of fields. However, the generation of a large quantity of wastewater containing uranium has posed a potential threat to our human well-being and ecological environment. Efficient separation of radioactive U(VI) from uranium-bearing wastewater is of great importance for humanity. Herein, a novel adsorbent UiO-66-NH 2 @phos-PDA(abbr. U6N@phos-PDA) was prepared by using phosphate and UiO-66-NH 2 encapsulated by PDA. The effects of various conditions such as solution pH, contact time and U(VI) concentration on the U(VI) adsorption process were explored by batch experiments. The kinetic study revealed that the adsorption equilibrium time of U(VI) by U6N@phos-PDA was 150 min, and the adsorption process adhered to the pseudo-second-order kinetic model, with chemisorption being the dominant mechanism. At 298 K, U6N@phos-PDA was able to adsorb U(VI) up to 423.23 mg/g. The Langmuir isotherm model describes the adsorption behavior, which was dominated by adsorption on the surface monolayer. Thermodynamic analysis indicated that U(VI) adsorption by U6N@phos-PDA is a spontaneous endothermic process. Additionally, U6N@phos-PDA exhibited excellent selectivity for U(VI) adsorption in the presence of other metal ions and can be reused effectively for at least five cycles. The FT-IR and XPS characterization analyses demonstrate that the phosphate and amino functional groups of U6N@phos-PDA are crucial for ion exchange and complexation with U(VI). Therefore, U6N@phos-PDA shows promising potential for the separation of U(VI).