Simple Amphoteric Charge Strategy to Reinforce Superhydrophilic Polyvinylidene Fluoride Membrane for Highly Efficient Separation of Various Surfactant-Stabilized Oil-in-Water Emulsions

Abstract

Long-term efficient separation of highly emulsified oily wastewater is challenging. Reported herein is the preparation of a reinforced superhydrophilic, underwater superoleophobic membrane with demulsification properties using active iron nanoparticles in situ generated on a polydopamine (PDA)/ polyethylenimine (PEI)-modified polyvinylidene fluoride (PVDF) membrane surface. A stable zwitterionic structure is fabricated on the membrane surface and provides it with an excellent capability of binding a hydration layer, leading to enhanced superhydrophilic/underwater superoleophobic properties. The interaction between the membrane surface and water is quantified using the relaxation time of water. After iron nanoparticles in situ anchoring, the superhydrophilic, underwater superoleophobic PDA/PEI modified PVDF membrane shows more stable flux behaviors, higher oil separation efficiency, demulsification, and excellent antioil-fouling properties for various anionic, nonionic, and cationic surfactant-stabilized oil-in-water emulsions in a crossflow filtration system. The reinforced hydration layer and the amphoteric charged demusification properties of the membrane play important roles in enhancing the membrane separation performance. The reinforced membrane also exhibits excellent cleaning and reusability performance in long-term operations. The outstanding separation performance, as well as the simple and cost-effective fabrication process of the membrane with various favorable properties, highlight its promise in practical emulsified oily water applications.

Modeling Bacterial Attachment Mechanisms on Superhydrophobic and Superhydrophilic Substrates

“…Superhydrophilic substrates exposed to an aqueous medium are assumed to yield surface properties and chemistry closely resembling those of pure water which is consistent with the experimentally observed wetting behavior of such substrates (e.g., underwater oil contact angles) [34][35][36]55]. The aforementioned experimental observation seems to indicate that ions would be largely excluded from the hydration layer associated with the substrate [35,56]. Thus, the surface energies, zeta potentials, and other related data for superhydrophilic substrates are assumed to be identical to water.…”

Efficient Fenton-Like Catalysis Boosting the Antifouling Performance of the Heterostructured Membranes Fabricated via Vapor-Induced Phase Separation and In Situ Mineralization

“…First, a hydration layer has been constructed to avoid the adsorption and deposition of the pollutants on the membranes . The hydrophilicity of the surface affects the stability and thickness of the hydration layer. , The common methods to enhance the hydrophilicity of the membranes include surface grafting and surface coating as well as blending. , Hydrophilic materials of poly­(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), zwitterion, sodium alginate, and phytic acid containing a large number of hydroxy, amino, sulfonic acid, and carboxyl groups are widely used in blending and surface modification, , which can significantly reduce the occurrence of reversible pollution . Zhou et al codeposited halloysite nanotubes (HNTs) and zwitterionic poly­(sulfobetaine methyl methacrylate) (PSBMA) on PVDF membrane.…”

Facile fabrication of underwater superoleophobic membrane based on polyacrylamide/chitosan hydrogel modified metal mesh for oil–water separation

“…[1][2][3] Highefficiency oil-water separation methods can effectively deal with oil spills and reduce property losses and environmental hazards. Commonly used oil-water separation methods include gravity separation method, 4 vacuum dehydration method, 5 phase separation due to "membrane coalescence," 6 filtration method, 7 adsorption, and absorption method, 8 floating selection method, 9 membrane separation method, 10,11 and salting-out method. 12 However, these treatment methods generally have disadvantages such as a long time, high-energy consumption, and low-separation efficiency.…”