Enhancing anti-scaling and anti-fouling performance in membrane distillation through liquid-infused membrane with slippery surface and gating properties

Membrane distillation (MD) is a promising method to produce fresh water by desalination of seawater and saline industrial wastewater. Hydrophobic membranes for MD tend to scaling and fouling during operation. Herein, liquid-infused membrane (LIM) with slippery surface and gating properties is proposed for anti-scaling/fouling MD. The LIM, denoted by PTFE-2-FL, was fabricated by coating a ∼ 2 μm-pore-sized polytetrafluoroethylene (PTFE-2) with dopamine and polyethyleneimine, silica nanoparticles, and fluoride (abbreviated as F), followed by lubricant filling (abbreviated as L). The lubricant capillary-locked in micropores forms a gate that can be reversibly opened for vapor under proper pressure, but prevents water from passing through, thus achieving vapor/water separation with a maximum salt rejection of 99.99 %. Compared with the non-lubricated membrane, PTFE-2-FL exhibits more stable separation performance, indicating the excellent anti-scaling/fouling properties owing to the non-adhesive lubricant surface avoiding contact between contaminants and membrane substrate, especially when treating high-salinity feed (NaCl of 250 g·L −1 ), simulated gypsum solution (NaCl of 35 g·L −1 , Na 2 SO 4 of 20 mM and CaCl 2 of 20 mM), organic compound-contaminated solutions (humic acid or sodium alginate of 500 mg·L −1 ), and inorganic–organic mixed solutions. PTFE-2-FL also has good reusability compared to the irreversible fouling of the hydrophobic membrane in cyclic MD process.