  Surface effect of low-surface-tension contaminants accumulating at the
evaporation surface can easily induce membrane wetting in the application of
membrane distillation, especially in hypersaline scenarios. In this work, we
propose a novel strategy to eliminate the surface effect and redistribute
contaminants at the evaporation interface with simply incorporating a layer of
hydrogel. The as-fabricated composite membrane exhibits remarkable stability,
even when exposed to extreme conditions, such as a salt concentration of 5M and
surfactant concentration of 8 mM. The breakthrough pressure of the membrane is
as high as 20 bars in the presence of surfactants, surpassing commercial
hydrophobic membranes by one to two magnitudes. Combined study of density
functional theory and molecular dynamics simulations reveals the important role
of hydrogel-surfactant interaction in suppressing the surface effect. As a
proof of concept, we also demonstrate the stable performance of the membrane in
processing synthetic wastewater containing surfactants of 144 mg L-1, mineral
oils of 1g L-1 and NaCl of 192 g L-1, showing potential of the membrane in
addressing challenges of hypersaline water treatment and zero liquid discharge
processes.
