Siphon-driven all-in-one fabric evaporators for multi-purpose treatment of hypersaline oily wastewater.

Hypersaline oily wastewater from industrial processes poses significant environmental challenges, but traditional treatment methods struggle with issues like oil contamination, membrane fouling, and incomplete oil/salt separation. In this work, we developed a siphon-driven all-in-one fabric evaporator (SAFE) that integrates siphon-driven separation with solar-driven evaporation to address these issues effectively. The photothermal fabrics are facilely fabricated by depositing polydopamine on polypropylene non-woven fabrics, imparting oil repellence, light-to-heat conversion, and hydrophilicity. Along the siphon flow line, oil emulsions are blocked by the fabric pores before reaching the evaporation unit, while concentrated saline is collected prior to scaling formation. Fabrics with a 15-µm pore size showed optimal performance, achieving an evaporation rate of 2.19 kg·m·h, over 99.8 % oil rejection, and a 65 % increase in concentration in indoor experiments. Outdoor tests demonstrated a freshwater production rate of approximately 5.84 L·m·day, with the collected liquid showing a 57 % increase in concentration for a 3.5 wt% NaCl solution and 99 % oil removal efficiency. The SAFE system offers a promising solution for efficiently treating hypersaline oily wastewater by separating oils, recovering freshwater, and concentrating salts.