Sargassum-inspired multifunctional adsorbent by grafting cyanopyridine ionic liquid on down fiber: achieving integrated enhancement of adsorption selectivity and efficiency

The engineering design of uranium adsorbents encounters great challenge in terms of adsorption selectivity, adsorption capacity and antibacterial properties. Based on the designability of ionic liquids and good self-floating property of down fibers, we developed a novel cyanopyridine ionic liquid (IL-AN) and introduced it into the structure of down fibers by covalent binding (IDF-AN). Then the cyanogroup in IDF-AN was amidoximated to obtained IDF-AO with π-π conjugated structure, finally Ag NPs was in-situ loaded to construct an adsorbent IDF-AO/Ag with enhanced photothermal conversion and antibacterial properties. The rigid planar structure of pyridine ring and the flexible chelating arm of amidoxime group in IDF-AO/Ag make it exhibit distinguished selective adsorption for O = U = O . The K d (U/V) is as high as (2.97±0.13) × 10 5 mL/g, which is significantly higher than other adsorbents. Simultaneously, IDF-AO/Ag, just like camouflaged sargassum, can float on water surface to be exposed under solar irradiation for a long time. In this way, the adsorption capacity of IDF-AO/Ag under light condition (589.0 mg/g) is increased by 51.2 % than under dark conditions (389.78 mg/g) with the help of photothermal effects. Additionally, the water evaporation rate is improved to 2.78 kg m -2 h -1 under 1 solar irradiation. After 5 adsorption-desorption cycles, the adsorption capacity maintains 87.7 % of initial adsorption. A 30-day natural seawater experiment in Bohai Sea (121.11 °E, 40.83 °N) shows high adsorption capacity (8.45 mg/g) and excellent strength. The self-developed adsorbent has potential application in real seawater and this groundbreaking study provides a new concept for the engineering design of uranium adsorbents by synergistic strategy of bionic design and specific functional modification.