RESUMEN
In this study, the dual strategy of 1-butyl-3-vinylimidazolium bromide ionic liquid (IL) grafting and carbon nanotubes (CNTs) nanocomposition was applied to modify poly(vinylidene fluoride) (PVDF)-based membranes. The highly hydrophilic/oleophobic and fouling-resistant PVDF-g-IL/CNTs membranes with excellent separation efficiency were obtained by the nonsolvent-induced phase separation method with ethanol-water mixed solution as the coagulation bath. The grafted IL not only generated hydrophilic groups on PVDF chains but also acted together with the CNTs to induce the formation of hydrophilic ß-crystalline phase of PVDF, which significantly improved the hydrophilicity and pore structure of the modified PVDF membranes. As a result, the pure water flux of the optimal membrane increased up to 294.2 L m-2 h-1, which was 5.2 times greater than that of the pure PVDF membrane. Simultaneously, the electrostatic interaction of the positive IL and the integration of CNTs enhanced adsorption sites of the membranes, producing exceptional retention and adsorption of dye wastewater and oil-water emulsion. This study presents a straightforward and efficient approach for fabricating PVDF separation membranes, which have potential applications in the purification of various polluted wastewater.
RESUMEN
In the process of removing dye wastewater, the membrane surface is susceptible to contamination, resulting in reduced performance and limited dye separation efficiency. A single hydrophilic modification layer is not enough to achieve effective separation of different types of dyes. The present research designed a "double layer protection" method in order to overcome the above deficiencies. A solution of dopamine (DA) coated carbon nanotubes (CNTs-COOH) was covered on the surface of the polyvinylidene fluoride (PVDF) membrane by deposition, followed by grafting a layer of chitosan (CS) polymer brushes on its surface. The spatial double layer structure provides an excellent barrier effect and effectively reduces the contamination of dyes. When filtering different types of dyes, effective filtration of anionic and cationic dyes through the electrostatic effect of the first layer, the adsorption of CNTs in the second layer and the hydration layer of both layers. All membranes have excellent rejection properties. More importantly, the membranes also had good chemical and mechanical stability and their serviceability was not degraded. Therefore, the prepared PVDF-based multi-layer composite membranes behave a potential application prospect in the wastewater purification field.
