One-step gel membrane fabrication via soft spray technique for dye/salt separation and desalination

Abstract

The effective separation of dyes and desalination represents a critical challenge in treating high-salinity dye wastewater. Herein, we propose an ultra-thin bifunctional gel membrane fabricated via a gas-liquid interface-assisted soft spray technique. This method enables precise control over membrane thickness while preserving a nano-porous architecture, which synergistically enhances both permeability and selectivity. By incorporating graphene oxide (GO), the membrane exhibits exceptional photothermal properties, enabling efficient solar-driven evaporation of separated salt solutions. The proposed two-stage treatment strategy sequentially achieves dye/salt separation and desalination, ultimately yielding potable water. During filtration, the membrane demonstrates a high separation flux of 37.3 L·m⁻²·h⁻¹ (0.1 MPa) with >99 % dye rejection, while maintaining low salt retention (<8 %), highlighting its potential for dye recovery from hypersaline wastewater. In the subsequent desalination phase, the gel-based evaporator achieves an evaporation rate of 1.76 kg·m⁻²·h⁻¹ under one-sun irradiation (1 kW·m⁻²), coupled with excellent salt resistance. Notably, the membrane exhibits outstanding antibacterial performance and anti-fouling properties, maintaining stable operation over 50 cycles. This stepwise approach not only enables resource recovery but also enhances the sustainability of wastewater management through simultaneous dye reclamation and freshwater production.