Carbonized cattle manure-based photothermal evaporator with hierarchically bimodal pores for solar desalination in high-salinity brines

Abstract

Interfacial solar desalination shows great promise to become an alternative technique for freshwater generation. However, the unavoidable fouling undermines continuous evaporation because the accumulated salt crystals weaken sunlight absorption and salt drainage, especially in high-salinity brines. Therefore, developing a photothermal evaporator with excellent salt rejection capability is urgent for high-salinity solar desalination. Here, a carbonized cattle manure-based photothermal evaporator with hierarchically bimodal pores is validated as an efficient desalinator for high-salinity brine (≥15 wt%). Taking advantage of the bimodally porous structure and interconnected microchannels formed by carbon fiber networks, it realizes rapid water transportation and quickly replenishes the surface-desalinated brine to prevent salt accumulation and enable stable freshwater generation. This carbonized manure evaporation device demonstrates a rapid evaporation rate of 2.25 kg m−2 h−1 under 1 sun irradiance (1 kW m−2) using a 15 wt% NaCl solution, as well as excellent long-term stability for the high-salinity desalination process. The nano-sized channels offer efficient nanoscale light trapping through multiple reflections and scatterations that occur within the channel walls. Furthermore, the abundance of raw materials provides a desirable and efficient approach for converting farm waste to energy, making it particularly well-suited for developing regions.