Biochar-Based Photothermal Membranes for Solar-Powered Distillation

Biochar is a carbon-rich material produced from biomass pyrolysis whose properties can be tailored for various applications, including soil improvement, water purification, and catalysis. Its light absorption capacity also makes it promising for solar-driven processes like water evaporation. Photothermal membrane distillation (PMD) combines membrane separation with light-induced heating for efficient water purification. Unlike conventional membrane distillation, PMD utilizes light-absorbing materials to enhance vapor pressure and overcome temperature polarization, a common issue in membrane distillation. This study explored the potential of biochars and activated biochars, as filler materials for photothermal membranes, in line with circular economy principles. The mixed matrix membranes were prepared in a single step, via non-solvent induced phase separation starting from a uniform dispersion of the filler in a polyvinylidene fluoride solution. These materials exhibited great heating performance, reaching surface temperature up to 36 ◦C under a 125 W/m2 light source. Increasing the biochar loading up to 15 wt.% resulted in an 85%increase in distillation flux under light irradiation.