image: The (MXene-MgO)@SA composite gel (MMS) features a hierarchical porous structure that enables efficient solar absorption and boron adsorption.
Credit: ©Science China Press
In a groundbreaking study published in Science Bulletin, researchers from China, have proposed a revolutionary solar-driven multi-field synergistic strategy for the simultaneous extraction of freshwater and boron from seawater or brine.
The worsening water-food-energy nexus demonstrates a critical challenge for sustainable development. With growing demand for these interconnected resources driven by population growth and economic expansion, regions such as Yemen, Pakistan, and Haiti face high water scarcity and alarming hunger levels. Seawater desalination technologies offer a viable solution, but conventional methods struggle to meet the strict boron limits in drinking water set by the World Health Organization (WHO), while also failing to recover boron as a valuable resource.
To well address these challenges, the research team engineered a (MXene-MgO)@sodium alginate (SA) composite gel (MMS) by co-doping MgO (a boron adsorbent) and MXene (a dual-functional material acting as both photothermal converter and boron adsorption aid) into an SA matrix. The MMS demonstrated outstanding performance under 1 sun illumination, achieving a high evaporation rate of 2.14 kg m–2 h–1 and a boron adsorption capacity of 225.52 mg m–2 within 9 hours.
The key to MMS's success lies in its unique hierarchical porous structure and the synergistic effects of MXene and MgO. The MXene nanosheets provide broadband light absorption and efficient photothermal conversion, while the MgO nanoparticles act as effective boron adsorbents. Notably, the interplay between temperature, concentration, and flowing fields within the MMS significantly enhances boron adsorption kinetics.
Outdoor field tests further validated the practical viability of MMS, yielding 5.20 kg m–2 of freshwater and recovering 122.45 mg m–2 of boron daily. Notably, the recovered boron significantly enhanced agricultural productivity, increasing the seed germination rate of Brassica juncea by 13% and tripling biomass production relative to the boron-deficient control.
This work establishes a revolutionary paradigm within the water-food-energy nexus, particularly relevant for resource-scarce coastal regions. The proposed desalination-coupled boron extraction technology presents a simple, universal, and resource-conserving solution with far-reaching implications for sustainable water and food security.