Conversion of Hazardous Diesel Soot Particles into a Novel Highly Efficient 3D Hydrogel for Solar Desalination and Wastewater Purification.

Diesel particulate matter (DPM) generated as vehicular exhaust is one of the main sources of atmospheric soot. These soot particles have been known to cause adverse health problems in humans and cause acute environmental problems. Despite great efforts for minimizing soot production, research on the disposal and recycling of inevitable diesel soot is scarce. However, DPM consists mainly of carbonaceous soot (DS) that can be easily utilized as a photothermal material for solar desalination. Recently, interfacial solar steam generation using three-dimensional (3D) structures has gained extensive attention. 3D-structured hydrogels have exhibited incredible performance in solar desalination owing to their tunable physicochemical properties, hydrophilicity, intrinsic heat localization, and excellent water transport capability. Herein, a novel DS-incorporated 3D polyvinyl alcohol (PVA)-based hydrogel is proposed for highly efficient solar desalination. The polymer network incorporated with purified DS (DS) achieved an excellent evaporation rate of 3.01 kg m h under 1 sun illumination due to its vertically aligned water channels, hydrophilicity, and intrinsic porous structure. In addition, the DS-PVA hydrogel could generate desalinated water efficiently (2.5 kg m h) with anti-salt fouling properties. The present results would motivate the utilization and recycling of waste materials like DS as photothermal materials for efficient, low-cost, and sustainable solar desalination.