Mussel-inspired dual-crosslinked polyamidoxime photothermal hydrogel with enhanced mechanical strength for highly efficient and selective uranium extraction from seawater

Abstract

• Mussel-inspired photothermal PAO hydrogel adsorbents were successfully fabricated. • PDA contributes to excellent hydrophilicity and photothermal conversion capacity. • Light irradiation yields the high uranium sorption capacity of 12.67 mg-U/g-Ads. • Excellent adsorption selectivity towards U(VI) over V(V) can be obtained. • Fe 3+ coordination endows with excellent tensile strength and self-recovery ability. The efficient development of selective adsorbents for uranium extraction from seawater is necessary for their potential application in nuclear power generation. The amidoxime-based adsorbents have been recognized as the potential candidates, whereas they still suffer from a much higher affinity towards V(V) present in the seawater over U(VI), leading to the extremely limited commercial use. In this work, we develop a novel mussel-inspired photothermal polyamidoxime (PAO) hydrogel adsorbent, in which polydopamine (PDA) chains are linked to PAO (PDA-PAO) via Michael addition. Dual-crosslinked Fe@PDA-PAO hydrogel structure is constructed by noncovalent bonds between the catechol of PDA chains (e.g. π-π stacking and hydrogen bonds) as well as ionic coordination of Fe 3+ . PDA contributes to the improved hydrophilicity and high photothermal conversion efficiency. As a result, after immersing in real seawater for 6 weeks, light-irradiated Fe@PDA-PAO hydrogel delivers high uranium sorption capacity (12.67 mg-U/g-Ads) together with high U/V mass ratios (1.17), which are superior to currently available hydrogel adsorbents. Meanwhile, Fe 3+ coordination endows Fe@PDA-PAO hydrogel with excellent tensile strength and self-recovery ability, which are of great significance to withstand the harsh conditions of ocean environment for practical applications. The results presented here reveal that Fe@PDA-PAO hydrogel holds tremendous potential for practical applications in the uranium-selective extraction from seawater.