Janus photothermal adsorbent for solar-powered simultaneous uranium extraction and co-production of freshwater and sea salt from seawater

Ocean reserves massive water and mineral resources. The success in uranium extraction and desalination from seawater is expected to alleviate the severe situation of energy and freshwater scarcities around the world. Herein, a novel Janus photothermal adsorbent was fabricated via sequential electrospinning for simultaneous uranium extraction and co-production of freshwater and sea salt from seawater. It consisted of a hydrophilic polyamidoxime (PAO) nanofibrous mat as the bottom layer for uranyl ion adsorption and a hydrophobic polyvinylidene fluoride (PVDF)/MXene (Ti3C2Tx) composite nanofibrous mat as the upper layer to capture and convert solar energy to heat. With the assistance of 1-sun illumination, the Janus adsorbent exhibited 6.05 mg g−1 of uranium adsorption capacity within 28 days from natural seawater, resulting in a 30.1 % increase compared to that in dark and achieved 1.36 kg m–2h−1 of water evaporation rate in natural seawater. An outdoor solar-powered adsorption coupling with evaporation test of this Janus adsorbent demonstrates that 6.40 kg m−2 of freshwater, 2.02 mg m−2 of uranium and 0.22 kg m−2 of sea salt were co-produced within 9 h operation. This study on the Janus adsorbent paves a promising way to the comprehensive development of ocean resources in low-carbon and sustainable strategy.