Sunlight Polymerization of Poly(amidoxime) Hydrogel Membrane for Enhanced Uranium Extraction from Seawater

Abstract

The uranium level in seawater is ≈1000 times as high as terrestrial ores and can provide potential near‐infinite fuel for the nuclear energy industry. However, it is still a significant challenge to develop high‐efficiency and low‐cost adsorbents for massively extracting uranium from seawater. Herein, a simple and fast method through low‐energy consumption sunlight polymerization to direct fabrication of a poly(amidoxime) (PAO) hydrogel membrane, which exhibits high uranium adsorption capacity, is reported. This PAO hydrogel owns semi‐interpenetrating structure and a hydrophilic poly(acrylamide) 3D network of hydrogel which can disperse and fix PAOs well. As a result, the amidoxime groups of PAOs exhibit an outstanding uranium adsorption efficiency (718 ± 16.6 and 1279 ± 14.5 mg g −1 of m uranium / m PAO in 8 and 32 ppm uranium‐spiked seawater, respectively) among reported hydrogel‐based adsorbents. Most importantly, U‐uptake capacity of this hydrogel can achieve 4.87 ± 0.38 mg g −1 of m uranium / m dry gel just after four weeks within natural seawater. Furthermore, this hydrogel can be massively produced through low‐energy consumption and environmentally‐friendly sunlight polymerization. This work will provide a high‐efficiency and low‐cost adsorbent for massive uranium extraction from seawater.

An Ion‐Crosslinked Supramolecular Hydrogel for Ultrahigh and Fast Uranium Recovery from Seawater

“…Therefore, the uranyl ions can easily immigrate into the inner layer of the hydrogel . While other hydrogel‐based adsorbents have high uranium adsorption capacities or good selectivity, amidoxime‐functionalized hydrogels have both . However, to improve the hydrophilicity of the poly(amidoxime) (PAO) and other amidoxime‐functionalized polymers, additional hydrophilic hydrogel 3D networks are commonly introduced.…”

“…However, to improve the hydrophilicity of the poly(amidoxime) (PAO) and other amidoxime‐functionalized polymers, additional hydrophilic hydrogel 3D networks are commonly introduced. These additional networks account for the high weight percentages of the adsorbents . But the low weight percentages (typically no greater than 50 wt%) of the amidoxime‐functionalized polymers seriously limits the uranium adsorption capacity of the hydrogels .…”

“…These additional networks account for the high weight percentages of the adsorbents . But the low weight percentages (typically no greater than 50 wt%) of the amidoxime‐functionalized polymers seriously limits the uranium adsorption capacity of the hydrogels . In theory, if we can design a new amidoxime‐functionalized hydrogel with both good hydrophilicity and a high weight percentage of PAOs, then we can greatly improve the uranium adsorption capacity of the hydrogel.…”

“…PAO was synthesized by amidoximating the polyacrylonitrile (PAN) according to the published literature ( Figure a) . We characterized the PAO using Fourier transform infrared spectroscopy (FT‐IR) spectra (Figure S5, Supporting Information), and found that the specific peak of the nitrile group (CN stretch, 2246 cm −1 ) had disappeared completely.…”

“…c) Comparison of the uranium adsorption capacity (96 h) of different Zn 2+ –PAO hydrogels in 32 ppm U‐spiked water and 32 ppm U‐spiked seawater. d,e) Water contact angle changes of NaOH‐treated PAO, semi‐IPN PAO dry gel, and Zn 2+ –PAO dry gel ( m Zn 2+ : m PAO = 4:100), respectively.…”