Low-cost, scalable, and durable coal-based composite aerogel beads solar evaporator for efficient seawater desalination and wastewater purification

Carbon-based aerogels have attracted extensive research interest due to its unique properties in solar-driven evaporation for seawater desalination and wastewater purification. Nevertheless, developing a low-cost, scalable, and durable carbon-based aerogel evaporator for realistic application is still challenge. Here, coal-based composite aerogel beads (coal-CABs) are successfully prepared from cheap and abundant coal powder combined with graphene oxide, sodium alginate and hollow glass bubbles via a simple liquid dripping strategy. The coal-CABs shows enhanced mechanical strength and good chemical resistance, can directly serve as integrated, self-floating, and durable solar evaporators without additional components. As a result, the coal-CABs demonstrates a stable water evaporation rate of 1.31 kg m−2 h−1 with a solar-to-vapor conversion efficiency of 84.0 % under 1 sun irradiation. Importantly, the coal-CABs exhibits good salt resistance (even for the 20 wt% NaCl solution and 1 wt% Li2CO3 solution) and anti-fouling capacity, which can be used to produce clean water from various types of water sources (seawater, lake water, rain water, acid wastewater, alkali wastewater, dye wastewater, and heavy metal wastewater). This study provides a new class of using coal powder as crude material and building block to produce low-cost, scalable, and durable solar-driven evaporators for efficient desalination and purification.