Improving seawater desalination efficiency by solar driven interfacial evaporation based on biochar evaporator of Nannochloropsis oculata residue

Abstract

Solar driven interfacial evaporation technologies have significant potential in seawater desalination, sewage purification and steam power generation applications. The interfacial evaporator is primarily composed of a solar absorption layer and a substrate for thermal insulation and water conveyance. However, the materials used in the solar absorption layer and substrate are typically expensive and difficult to produce, which is not conducive to large-scale application. Herein, a novel porous microalgae biochar solar interfacial evaporator (MBSIE) was developed for high-performance solar-driven water vapor generation. The solar absorption layer was synthesized with the residue of the microalgae species Nannochloropsis oculata, which was generated from the process of biodiesel production. The substrate was composed of polystyrene foam and absorbent cotton sticks with an optimized water channel design. The light absorptivity of porous Nannochloropsis oculata biochar reached 94.1%, and the material contains hydrophilic groups such as C–O and N–H, which was conducive to water delivery. MBSIE attains a maximum seawater evaporation rate of 1.165 kg m−2 h−1 under one Sun irradiation intensity. The total dissolved solids and salinity of the produced fresh water was 265 mg L−1 and 0.06‰, respectively. This quality of freshwater could meet domestic water standards.