Self-Emulsifying air-in-water HIPEs-Templated construction of amidoxime functionalized and chain entanglement enhanced macroporous hydrogel for fast and selective uranium extraction

Abstract

A convenient design of amidoxime (AO)-functionalized hydrogel sorbent containing interconnected pores is critical for facilitating fast and selective uranium extraction. To address this, air-in-water high internal phase emulsions (HIPEs) templated construction of AO functionalized macroporous hydrogel sorbents (GMPAO) is reported for highly efficient extraction of uranium from aqueous solution. Curled gelatin methacryloyl (GelMA) chains, as amphiphilic Pickering emulsifier and molecular surfactant, endow self-emulsifying ability to stabilize the air/water interface. GMPAO exhibits an open-cell structure (diameter is about 80 % between 200 µm and 300 µm) with interconnecting pores (distribution is about 70 % between 55 µm and 75 µm), and the chain entanglement between polyamidoxime (PAO) and GelMA enhances mechanical strength. Benefitting from the macroporous structure and abundant affinity sites, GMPAO displays a spontaneous uranium adsorption capacity of 386.61 mg g−1 at 298 K and faster uptake within 60 min, which are superior to better than the previously reported hydrogel sorbent. In addition, GMPAO hydrogel still achieves the highest capacity and remarkable removal rate of almost 100 % towards uranium in the presence of competitive ions, as well as excellent recyclability toward uranium capture. Except for the coordination between uranium with amidoxime groups, the carboxylates from GelMA also cooperate as a synergistic effect for uranium uptake by charge interaction, which enhances the binding affinity of the adsorbent to uranium. Most importantly, this work demonstrates a new strategy for preparing macroporous hydrogel sorbents with enough stability and provides a new perspective for recovering uranium from an aqueous solution.