A 3D smart wood membrane with high flux and efficiency for separation of stabilized oil/water emulsions

Oily sewage discharged from indiscriminate industrial and frequent oil spills have become a serious global problem. There is an urgent need to separate stable oil/water emulsions by efficient and environmentally friendly methods. Membrane separation technology has the advantages of low energy consumption and low cost, thus is an effective solution to the problems of oily wastewater. However, the manufacture of multifunctional mem-branes with high efficiency, high flux and self-cleaning using renewable materials remains a challenge. Herein, three-dimensional (3D) smart membranes with switchable superhydrophobic-hydrophilic surfaces were prepared by grafting photo-responsive poly-spiropyran (PSP) on wood-based substrates via surface atom transfer radical polymerization. This novel membrane can efficiently separate stabilized water-in-oil and oil-in-water emulsions due to reversible hydrophilic-hydrophobic transition by switching UV and visible light irradiation. Remarkably, after immobilization, the PSP grafted on the wood substrate exhibited a faster photo response effect than the free spiropyran (SP). More importantly, the prepared 3D smart membranes showed exceptional high flux (4392 L center dot m-2 center dot h-1) and efficiency (above 99.99 %), good cycle stability (99.99 % after 12 times) and durability (available for at least 60 days) for the separation of surfactant-stabilized water-in-oil emulsions. This work opens a new avenue for the design of functional biomass-derived membranes for efficient and sustainable oily wastewater treatment with high flux, easy scale-up, and green regeneration.

Automated summary

In this study, a three-dimensional smart membrane with switchable superhydrophobic-hydrophilic surfaces was successfully prepared by grafting photo-responsive poly-spiropyran on wood-based substrates. This novel membrane can efficiently separate stabilized water-in-oil and oil-in-water emulsions through reversible hydrophilic-hydrophobic transition by switching UV and visible light irradiation. The prepared 3D smart membranes exhibited exceptional high flux, efficiency, cycle stability, and durability for the separation of surfactant-stabilized water-in-oil emulsions. This work opens a new avenue for the design of functional biomass-derived membranes for efficient and sustainable oily wastewater treatment.