Tailoring surface topography of biochar-based hydrogel for hazardous pollutants removal from contaminated seawater through simultaneous steam-electricity generation

Although solar steam generation (SSG) is a promising strategy for solving global freshwater scarcity, some technological gaps remain such as the generally costly and delicate nanostructures. Herein, multifunctional Biochar/PAAm hydrogels with excellent resilience, openly porous structure, fast water-transfer, and enhanced light-trapping performances were fabricated from the strong attraction of the biochar functional groups and the abundant amido groups of the backbone chain of hydrogel through a facile polymerization strategy. Under 1 sun irradiation, the composite exhibited a high and long-term evaporation rate of 2.22 kg m−2 h−1 due to the synergistic effect of excellent light absorption of biochar and fast water transmission in hydrogel structure which decrease the evaporation enthalpy. Furthermore, the hydrogel surface topography was controlled by template-assisted gelation producing a sharply dimpled surface (SDS) that exhibited a high evaporation rate of 2.71 kg m−2 and an efficiency of 98.7 % owing to the light trapping effect on the sharped surfaces. The high adsorption capacity of the hydrogel enables the removal of hazardous pollutants from the bulk water preventing their concentration in the brine after the solar desalination process. Besides, a thermoelectric (TE) generator can be integrated with the membrane producing a simultaneous power density of 728.2 mW/m2. [Display omitted] •Green-synthesized sawdust-derived biochar-based polyacrylamide hydrogel as evaporators•The hydrogel surface topography was controlled to increase the light scattering.•The evaporators exhibited a high evaporation rate of 2.71 kg m−2 under 1 sun irradiation.•The hydrogel possessed excellent salt resistance, and pollutants removal.•The composite exhibited simultaneous solar steam and electricity generation.