Hydrophilic PVDF emulsion separation membranes prepared using TA/APTES as a non-solvent: Effect of lithium chloride hydrate additive content

A hydrophilic PVDF film was prepared by solvent exchange using TA/APTES prepolymerization solution as the exchange solvent. The effect of the co-blended hydrated lithium chloride content on the growth of TA/APTES within the films was explored. The modified films exhibited excellent separation performance for micron- and submicron-sized oil-in-water emulsions containing surfactants . Currently, surfactant-containing oil–water emulsions are the more difficult part of oily wastewater to treat because of their small droplet size and stable oil–water interface. Membrane separation technology is commonly used for emulsion separation due to its surface wettability and adjustable pore size. Here, tannic acid (TA) and 3-aminopropyltriethoxysilane prepolymerization solutions are used as the exchange solvents, allowing growth on the surface and inside of polyvinylidene difluoride (PVDF). Among them, the content of lithium chloride (LCM) hydrate modulates the range and amount of growth. In the pressure range of 0.1–0.7 bar, the modified hydrophilic PVDF-TA/LCM-2 membranes exhibit high pure water permeation fluxes and emulsion separation efficiencies that can be adapted to different separation conditions. At 0.2 bar, the PVDF-TA/LCM-2 achieves pure water permeate flux and emulsion separation fluxes of 1860 and 648 L m -2 h −1 bar −1 , and an emulsion separation efficiency of 99.5 %. In addition, for different kinds of oil-in-water emulsions, the high separation fluxes and high separation efficiencies indicate that PVDF-TA/LCM-2has good emulsion separation performance.