Facile modification of commercial PVDF membrane with poly(tetrafluoride ethylene-r-vinylpyrrolidone) for fouling tolerance and highly efficient separation of oil/water emulsion

摘要

While historical trends indicate the rapid expansion of manufacturing industries, there is an increasing interest in highly-efficient comprehensive oil-in-water emulsions separation. However, most conventional techniques, such as physical adsorption, electrocoagulation and centrifugation suffer from limitations of high energy consumption, process complexity and low separation efficiency [1], especially not effective for the surfactant-stabilized microemulsions with a droplet size below 50 μm. In order to achieve the ultimate oil contaminated wastewater purification, the pressure-driven membrane separation technology has been proved as a promising alternative, with the main advantages being energy and space efficient, low cost, high-operation flexibility and facile scalability. In this work, we have designed and fabricated an ultrathin poly(tetrafluoride ethylene-r-vinylpyrrolidone) (F-VP) layer with controllable thickness of 2 μm, supported by commercial polyvinylidene difluoride (PVDF) substrate (hereafter named F-VP/PVDF membrane), via an extremely simple, scalable and one-step surface modification method. The F-VP/PVDF membrane showed an excellent superhydrophilic/under oil superhydrophilic properties, as well as superoleophobic property to various oils (soybean oil, hexadecane and hexane). The F-VP/PVDF membrane with tunable effective pore size of ~ 400 nm could efficiently separate various complex oil-in- water emulsions containing surfactants with high water permeability of 4612 L m~(-1) h~(-1) bar~(-1), high emulsion permeability of 745 L m~(-1) h~(-1) bar~(-1) (10000 ppm soybean oil-in-water emulsion) with a high rejection efficiency ratio of >99.9%, and an extremely fouling-resistant and fouling-releasing property of nearly 100% flux recovery over 5-time continuously cyclic tests.