Tailoring anionic solar evaporator with an enhanced Donnan effect for a highly effective salt resistance desalination and water purification

Emerging solar-driven interfacial water evaporation demonstrates immense potential in mitigating worldwide water shortages, offering exceptional solar-to-vapor conversion efficiency, off-grid operability, zero liquid discharge capability and low carbon footprint. A critical requirement for sustainable extraction clean water from brine is the development of solar evaporators with both salt resistance and high evaporation rates. In response to this demand, this research proposed an enhanced Donnan effect anionic solar evaporator through filling wood in situ with PVA/PAA hydrogel. The resulting anionic solar evaporator demonstrated broadband spectral absorption, excellent photothermal conversion, and water activation capability. Notably, based on the negative charge property of the –COO– group anionic hydrogel, it could enhance Donnan effect and restrict the diffusion of Cl− to the evaporator, ensure enduring salt resistance and stability in purifying brine effectively. Experiments proved that the anionic anionic solar evaporator attained a remarkable water evaporation rate of 2.439 kg m−2 h−1 during a desalination of 15 wt% NaCl solution under 1 kW m−2 solar radiation, and no obvious salt accumulation had been observed during prolonged evaporation processes. With high efficiency, renewability, deployability, low cost, and durability, the anionic solar evaporator emerges as a promising solution for mitigating water scarcity, especially in economically challenged regions and provides valuable perspectives for future investigations into the water-energy-climate nexus.