Large-area, low-cost, highly durable solar evaporators for sustainable solarizing seawater

Conventional solarizing seawater technology faces significant challenges including a large footprint, time-consuming processes, and inefficient energy utilization. Solar-driven interfacial water evaporation (SIWE) technology, offers a promising approach for sustainable solarizing seawater, facilitating the production of solid salt with reduced time and land requirements. Nevertheless, the urgent challenge lies in the development of low-cost, large-area solar evaporators that are highly salt-resistant and adaptable, enabling efficient and sustainable solar desalination for solid salt production. As such, a large-area, affordable, and highly durable melamine foam/reduced graphene oxide/sodium alginate (MGS) solar evaporator is proposed for continuous solarizing seawater using a simple method of "immersion-crosslinking-reduction". Among them, hydrophilic melamine foam serves as the supportive framework, immersed with graphene as light absorption material, and hydrophilic sodium alginate polymeric network for fixing graphene sheets and regulating water evaporation enthalpy. As such, MGS solar evaporator can be prepared in a large-area of 0.5 m × 0.5 m at the cost prices as low as $2.91 m−2. The optimized MGS solar evaporator achieves a high water evaporation rate of 2.30 kg m−2h−1 with the photothermal conversion efficiency of 89.2 % under one sun irradiation. In outdoor environments, MGS allows for timely convective/diffusive salt discharge through its macropores, thus allowing for prolonged seawater solarization without obvious solid salt accumulation. Notably, the original seawater can be highly concentrated until all the water evaporates and solid salt precipitates. This developed MGS solar evaporator offers a novel perspective on efficient seawater solarization, conserving both time and land.