Construction of functionalized microcapsule adsorbents using emulsion templates for simultaneous thermal storage and selective adsorption of uranium

The treatment of nuclear wastewater generates substantial amount of uranium (U(VI)) contaminated wastewater, along with waste heat. Efficiently extracting U(VI) while managing nuclear waste heat is crucial. In this study, the functionalized microcapsule adsorbent (PDA-PO₄³⁻/PEG) was synthesized using an emulsion template method. The synthesis involved the oxidative polymerization of dopamine with the grafting of phosphoric acid functional groups. The resulting black shell layer enabled the conversion of light energy into heat energy, while the inner phase of the microcapsule, composed of polyethylene glycol (PEG), served as a heat storage material. The maximum adsorption capacity of PDA-PO₄³⁻/PEG at 298 K was 242.59 mg g⁻¹, reaching equilibrium within 30 min. The removal efficiency of U(VI) by PDA-PO₄³⁻/PEG exceeded 99 %, even in the presence of various competing metal ions. Thermal and near-infrared light tests demonstrated that a concentration of 2.0 mg mL⁻¹ of PDA-PO₄³⁻/PEG dispersion reached temperature above 80 °C after just 5.0 min of laser irradiation. Furthermore, the latent heat of phase transition was measured at 164.13 J g⁻¹. The PDA-PO₄³⁻/PEG microcapsule demonstrated excellent adsorption capacity and selectivity. It's combined high uranium adsorption performance, selectivity, strong photothermal conversion, and thermal storage capabilities make it a material of significant interest industrial applications.