A bionic solar-driven interfacial evaporation system with a photothermal-photocatalytic hydrogel for VOC removal during solar distillation

Solar-driven interfacial evaporation is a breakthrough water treatment method because it harvests solar energy for producing clean water. However, evaporated volatile organic compounds (VOCs) in distilled water are the greatest barrier to this technology. Herein, a bionic solar-driven interfacial evaporation system integrating photothermal and photocatalysis technology was developed based on a new combined material TiO2/Ti3C2/C3N4/PVA (TTCP) hydrogel as an evaporator. Phenol-contaminated water, especially actual water (seawater, lake water and reclaimed water), is used to evaluate the water evaporation and VOC photocatalytic degradation performance. The results show that the evaporation rate of TTCP hydrogel was 1.54 kg m - 2h - 1 under 1 kW m - 2, and the removal efficiency of phenol ranged from 69.4% to 100% at different concentrations (1-50 mg/L) in source water. Particularly, the capacity of the bionic evaporator was first evaluated for different types of actual water. Despite the initial TOC (38.12-57.93 mg/L) and total dissolved solids (TDS, 1.35×103-8.78×104 mg/L) for seawater, lake water and reclaimed water being very different, the TDS was decreased by more than two orders of magnitude, below the US EPA drinking water standard (500 mg/L). The maximum TOC removal efficiency reached 80% under simulated sunlight (1 kW m - 2), which is comparable to the efficiency of the ultrafiltration technique previously reported except for seawater. Furthermore, real sunlight (average solar irradiation ∼0.82 kW m- 2) was used to assess the practicability. The bionic evaporator can produce 0.72 kg m - 2h - 1 of vapor from reclaimed water and run with steadily efficient TDS and TOC removals, reaching 99% and 74%, respectively. This technology, as a small, decentralized water treatment method, is a good choice for remote and off-grid areas.