A smart superwetting PET-Anthocyanin membrane for pH monitoring in water and emulsion separation

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Smart superwetting membranes with anti-oil pollutions and process water pH monitoring show great potential before downstream processing. Herein, a flexible intelligent monitoring membrane with strong anti-oil fouling properties was developed by utilizing a PET-Anthocyanin mixed solution through electrospinning. Specifically, using waste PET plastic bottles as raw materials, a dual-solvent system is used to dissolve the PET, and then anthocyanins are added to blend to form an electrospinning solution. The obtained A/PET showed excellent porous morphology and wettability, and its underwater oil contact angle could reach up to 150°. The introduction of anthocyanins (5 %) rich in hydroxyl functional groups reduced the formation of hydrophobic domains and promoted the hydration layer on the membrane surface, showing excellent oil resistance property. Furthermore, the stress–strain test of the A/PET5 membrane shows that the strain is significantly enhanced after the yield phenomenon, which shows that the membrane has a flexible mechanical property. Most importantly, based on the pH-sensitivity of anthocyanins, it can be intuitively found that color response changes from the original pink to light pink, and then to white, showing excellent monitoring the pH of the continuous phase. Moreover, the developed membrane possesses water flux of 7440 L m-2h−1 and oil rejection up to 99.4 % for O/W emulsions, surpassing that of the superhydrophilic PET base membrane (956 L m-2h−1, 99.3 %). Briefly, this work provides a novel multifunctional smart membrane with excellent anti-fouling, flexible mechanical, and outstanding separation performance, which can visually monitor the separation process of oily wastewater.