Influence mechanism of amide-based amphoteric molecules on uranium adsorption capacity of WS₂

The recovery of uranium from uranium-containing wastewater is mainly based on the complexation between the material and UO₂ ²⁺ in UO₂(H₂O)₅²⁺, but the electric dipole moment of H₂O has a significant weakening effect on the complexation. The amide-based amphoteric molecule N,N-dimethyl-9-decenyl amide (NADA) was used for hydrogen bonding with UO₂(H₂O)₅²⁺ to form UO₂(H₂O)_xC₁₂H₂₃NO_n ^* (x<5, UO₂-Coordination Compound was named UO₂-CC) ,Inert tungsten disulfide (WS₂) was selected as the adsorption material, and the adsorption capacities of UO₂ ²⁺ and UO₂-CC were studied by static adsorption experiments (different pH, contact time, concentration and temperature). The kinetic fitting results showed that the adsorption reaction was a chemisorption process. After NADA reconstruction, the adsorption time of UO₂ ²⁺ was shortened from 240 min to 180 min, and the quasi-second-order kinetic adsorption constant was increased by 1.35 times. The results of the isothermal adsorption study showed that the complexation process of WS₂ and UO₂-CC conformed to the Langmuir adsorption isothermal model, and the addition of NADA made the adsorption change from spontaneous endothermic process to spontaneous exothermic process, and the order degree of the adsorption reaction process increased. After in situ reconstruction of UO₂(H₂O)₅²⁺ by NADA, the equilibrium adsorption capacity of UO₂ ²⁺ by WS₂ increased from 45.03 mg/g (WS₂/UO₂ ²⁺ system) to 122.14 mg/g (WS₂/UO₂-CC system). Spectroscopic analysis by X-ray photoelectron spectroscopy was used to deeply study the adsorption mechanism of NADA on WS₂ after in situ reconstruction of UO₂(H₂O)₅²⁺ at the molecular level, and to reveal the contribution of various forces (electrostatic, hydrogen bond and U-S covalent bond) to adsorption, especially the hydrogen bond of NADA.