Construction of a sustainable low-cost functional layered oil-water gel interfacial evaporator for fracturing flowback fluid treatment

The high treatment costs and substantial energy consumption associated with high-salinity fracturing flowback fluids remain critical bottlenecks restricting the development of shale gas. This study constructed a functionalized layered oil-water hydrogel solar interfacial evaporator (FG-SWE), aiming to achieve low energy consumption and zero emission treatment of high-salinity fracturing flowback fluids. The evaporator was synthesized via one-pot polymerization and consists of three functional layers (top: MXene, middle: 12-hydroxystearic acid (HSA)-based, bottom: porous), each responsible for light absorption, thermal management, and water transport, respectively. Results showed that under one sun irradiation, FG-SWE demonstrated an evaporation rate of 2.80 kg m −2 h −1 and a photothermal conversion efficiency over 95 % in 10 wt% standard saline waters, with the hydrophobic area ratio of the evaporation interface set at 30 %. Furthermore, the phase-change heat storage layer has a melting enthalpy of 125.8 kJ kg −1 , enabling continuous nighttime evaporation with a daily water production of 17 kg·m −2 . Furthermore, the FG-SWE effectively treated high-salinity flowback fluid, reducing total dissolved solids content (TDS) from 8 × 10 4 mg L −1 to < 125 mg L −1 to meet drinking water standards. The evaporator also demonstrated excellent anti-fouling properties and long-term stability, retaining 90.7 % performance over 30 days of continuous operation. This study provides a promising technology for high-salinity wastewater, thereby supporting the green development of shale gas and enhanced recycling of water resources.