Robust superhydrophobic V2O5/CoFe2O4@SiO2/PDMS composite membranes for membrane distillation

Abstract

Membrane distillation (MD) is a promising technology for water desalination. The widespread application of MD requires membranes with improved wettability, durability, fouling resistance, precise selectivity, and high efficiency. Composite MD membranes with a superhydrophobic modification, tailored porosity, and robust textures are emerging as advanced sieves paving the way toward improved flux and exceptional salt rejection. Herein, a fluorine-free dual-layer composite membrane with superhydrophobic–hydrophilic characteristics is fabricated using a layer-by-layer assembly route. The importance of our design lies in the tailored wettability-gradient across the composite membrane with heterogeneous textures functioning as manifold sites for condensation and hierarchical pores for efficient vapor transportation. The resulting dual-layer membrane featured a re-entrant surface with a WCA of ∼168° and physicochemical durability in extreme environments, including acidic (pH = 1), basic (pH = 14), surfactant (SDS), hot saline water, rust, and sonication. In a direct-contact-membrane-distillation (DCMD) set-up, the membrane displayed a water flux of 87 L m⁻² h⁻¹ with a separation efficiency of up to ∼99.6% over 12 h of operation. Additionally, it demonstrated strong antifouling properties, stable water flux, and salt rejection ability during desalination of saline solutions containing surfactants and rust as foulants. Notably, the membrane maintained a stable flux and high salt rejection during the usage of seawater further validating its robustness and suitability for long-term use in harsh saline environments.