Hydrophilic PVDF membrane with versatile surface functions fabricated via cellulose molecular coating

Fabrication of PVDF Membranes with a PVA Layer for the Effective Removal of Volatile Organic Compounds in Semiconductor Wastewater

Through the application of advanced membrane modification strategies, high-performance membranes have been developed to effectively remove organic contaminants such as toluene and xylene from wastewater. These membranes demonstrate superior antifouling resistance and long-term operational stability, offering a competitive advantage for semiconductor wastewater treatment. This study introduces a novel approach to membrane fabrication using polyvinylidene fluoride (PVDF), recognized for its cost-effectiveness and distinct antifouling properties in contaminant removal. To enhance the performance of the membrane, the solvent (DMA, DMF, NMP) that dissolves PVDF and the immersion time (30 min, 60 min, 90 min) at which phase separation occurs were identified. Additionally, the membranes were treated with polyvinyl alcohol (PVA) through multiple dip coatings to enhance their hydrophilicity before a comparative analysis was conducted. The resulting optimized membranes demonstrated high emulsion fluxes (4412 Lm-2h-1bar-1 for toluene) and achieved oil-removal efficiencies exceeding 90% when tested with various organic solvents, including toluene, cyclohexane, xylene, benzene, and chloroform. The resulting optimized membranes prove to be a reliable means of producing clean water and of efficiently separating organic contaminants from wastewater. Showcasing remarkable antifouling capabilities and suitability for repeated use without significant efficiency loss, this solution effectively addresses cost and fouling challenges, presenting it as a sustainable and efficient wastewater treatment method for the semiconductor industry.

Organic-Inorganic Modification of PVDF Membranes by PDA@ZnO and PDA@MgO Nanoparticles for Enhanced Performance of Organic Dye Wastewater Treatment

Polyvinylidene fluoride (PVDF) membranes represent a potential technology for the in-depth treatment of organic dye-containing wastewater. Nevertheless, the intractable membrane fouling and the limited versatility have significantly constrained its applications. Herein, through the nonsolvent-induced phase inversion method, we have successfully fabricated the PDA@MgO/PVDF and PDA@ZnO/PVDF membranes, which are modified by the synergistic action of MgO or ZnO nanoparticles with polydopamine (PDA), respectively. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as the analyses of pore structure, contact angle, and surface free energy, were utilized to characterize the hybrid membranes. The results demonstrate that the modification of PDA@MgO and PDA@ZnO can enhance the hydrophilicity, pure flux, dye rejection, and pollution resistance of PVDF membranes. The enhanced hydrophilicity of the modified membranes results from the increase in surface free energy and its polar component term. Comparatively, the PDA@ZnO/PVDF membrane exhibits a smaller contact angle (69°) and a higher pure water flux (378.63 L/m2·h·bar), whereas the PDA@MgO/PVDF membrane possesses greater mechanical strength and better antifouling performance. The PDA@MgO/PVDF membrane can achieve a rejection rate of 94.6% for disperse deep blue 79, and the flux recovery rate can reach approximately 82%. This research offers novel insights into the application of PVDF membranes for the treatment of organic dye-containing wastewater.

Graphene oxide-chitosan coated PVDF adsorptive microfiltration membrane: Enhancing dye removal and antifouling properties

This study investigates graphene oxide (GO) modified poly(vinylidene fluoride) (PVDF) membranes focusing on their dye rejection efficiency and their antifouling properties against bovine serum albumin (BSA). These membranes were prepared by modifying commercial PVDF membrane with a thin layer of GO nanosheets and chitosan (CS) using vacuum filtration. The synergistic physicochemical properties of the GO-CS/PVDF membranes were analyzed by XRD, FTIR, Raman, and XPS spectroscopy. The surface morphologies were observed by SEM and AFM microscopy, and WCA measurements. The deposition of GO and CS in the presence of citric acid resulted in a decrease in pore size and an increase in hydrophilicity. Modified membranes showed enhanced rejection of RB and MB, with rates increasing from 13.0 to 96.0 % and 28.3 to 69.1 %, respectively. Antifouling studies using BSA on selected membranes outperformed pristine membranes, which had higher irreversible fouling due to pore blockage. GO-CS/PVDF membranes exhibited higher flux recovery and lower irreversible fouling due to increased hydrophilicity, which prevents tight cake layer formation. Minimal detachment of the GO-CS layer during the long-term stability test is confirmed by minor fluctuations in dye flux and rejection. In summary, enhancing PVDF membranes with GO and CS augments dye rejection rates and bolsters antifouling properties.

Improving multifunctional properties of the polyvinylidene fluoride (PVDF) membrane with crosslinked dialdehyde-starch (DAS) and polyethyleneimine (PEI) coating

Dialdehyde-soluble starch (DAS) and polyethyleneimine (PEI) were used to coat the polyvinylidene fluoride (PVDF) membrane for improving its antifouling and multifunctional properties through a combination of dip-coating and spray-coating techniques. The resulting membrane demonstrated excellent hydrophilicity and underwater oleophobicity due to hydrophilic DAS and PEI on its surface. The membrane achieved an impressive oil removal rate of 99.8 % and a flux 1420.8 ± 26.5 L·m-2·h-1 when it was used for oil-water emulsion separation. The hydration layer formed by the DAS and PEI greatly enhanced the membrane antifouling property, and its flux recovery rate was up to 96.6 % in BSA filtration experiments. The positive charge PEI and the negative charge DAS contributed to high separation efficiency of 99.1 % for the anion dye MO with the membrane D10P20, and high separation efficiency of 88.3 % for the cation dye RhB with the membrane P5D20. In addition, the coating layer was stable due to the cross-linked DAS and PEI. This research contributes greatly to the preparation of antifouling and multifunctional membrane using environmentally friendly material including polysaccharide derivatives and water soluble polymer.

Catechol-Fe(III) complexes modified PVDF membrane for hazardous pollutants separation and antifouling properties

Organic pollutants, such as toluene and xylene, in industrial wastewater negatively impact the environment. Membrane treatment is one of the best methods to reduce impurities in wastewater. Existing membranes that coat the water surface with hydrophilic material only effectively resist the initial fouling, resulting in poor oil and water selectivity. Here we report a simple and efficient method to enhance the water flux and antifouling properties of polyvinylidene fluoride (PVDF) membranes. This method involves developing and applying Catechol-Fe(III) complexes with a rough surface to the PVDF surface. Forming Catechol-Fe(III) complexes on the surface better anchors them to the membrane than the dip-coating method. The PVDF membranes with rough Catechol-Fe(III) complexes are superoleophobic, with an oil contact angle of 152 ° and high permeability, with pure water flux of 10487 Lm-2h-1bar-1 and 1 wt% toluene in water emulsion flux of 4697 Lm-2h-1bar-1. Overall, the straightforward manufacturing process, increased permeability, and outstanding antifouling capabilities of the PVDF membrane incorporating rough nanoparticles offer promising prospects for designing and implementing suitable membranes for oil in water emulsion separation applications.

Cyclodextrin-modified PVDF membranes with improved anti-fouling performance

The design of hydrophilic polyvinylidene fluoride (PVDF) membranes with anti-fouling properties has been explored for decades. Surface modification and blending are typical strategies to tailor the hydrophilicity of PVDF membranes. Herein, cyclodextrin was used to improve the antifouling performance of PVDF membranes. Cyclodextrin-modified PVDF membranes were prepared by coupling PVDF amination (blending with branched polyethyleneimine) and activated cyclodextrin grafting. The blending of PEI in the PVDF casting solution preliminarily aminated the PVDF, resulting in PEI-crosslinked/grafted PVDF membranes after phase inversion. Aldehydes groups on cyclodextrin, introduced by oxidation, endow cyclodextrin to be grafted on the aminated PVDF membrane by the formation of imines. Borch reduction performed on the activated cyclodextrin-grafted PVDF membrane converted the imine bonds to secondary amines, ensuring the membrane stability. The resulting membranes possess excellent antifouling performance, with a lower protein adsorption capacity (5.7 μg/cm2, indicated by Bovine Serum Albumin (BSA)), and a higher water flux recovery rate (FRR = 96%). The proposed method provides a facial strategy to prepare anti-fouling PVDF membranes.

In situ preparation and properties of polyvinyl alcohol/synthetic ribbon-like nanocellulose composites

This study presents a novel approach in which a dual network (DN) composite, comprising polyvinyl alcohol (PVA) and ribbon-like nanocellulose (RC), was synthesized in one step using the volume exclusion effect involved in enzyme-catalyzed cellulose synthesis. Additionally, the impact of PVA as a crowding reagent during enzymatic catalysis on the in situ formation of nanocellulose and its resulting aspect ratio was explored. In contrast, the other two composites were created by incorporating enzyme-catalyzed synthetic block cellulose (BC) and its acid-hydrolyzed regenerated disc-shaped cellulose (DC) into the PVA. Subsequently, the mechanism by which three distinct types of nanocellulose, varying in morphology and size, was explored to elucidate their contributions to enhancing the properties of PVA. The results demonstrated that PVA/RC outperformed PVA/BC and PVA/DC. The elevated aspect ratio and intricate network structure of RCs not only significantly bolster the mechanical robustness of PVA/RC, leading in an 86.40 % surge in tensile strength and a remarkable 277.03 % rise in tensile modulus in comparison to pure PVA, but also induce a slight enhancement in elongation at break. Moreover, the thermal stability and biodegradability of PVA/RC was enhanced. Collectively, this study introduces an innovative strategy for the efficient fabrication of biodegradable composites with enhanced properties.

Direct-coating of cellulose hydrogel on PVDF membranes with superhydrophilic and antifouling properties for high-efficiency oil/water emulsion separation

As a well-known natural and innocuous plant constituent, cellulose consists of abundant hydroxyl groups and can tightly adsorb onto material surfaces hydrogen bonding, resulting in a superhydrophilic surface. In this work, the hydrophobic polyvinylidene fluoride (PVDF) membranes were modified by immersing them in cellulose hydrogel using a simple one-step process. The modified PVDF membrane exhibited excellent resistance to fouling and oil adhesion, making it highly effective in separating various oil-in-water emulsions. The cellulose-modified PVDF membranes achieved a high oil rejection rate (>99 %) and a maximum separation flux of 2675.2 L·m-2·h-1. Furthermore, even an oil-in-water emulsion containing bovine serum albumin maintained a steady permeation flux after four filtration cycles. Additionally, these cellulose-modified PVDF membranes demonstrated excellent underwater superoleophobicity across a wide range of pH levels and high saline conditions. Overall, these cellulose-modified superhydrophilic PVDF membranes are sustainable, environmentally friendly, easily scalable, and hold great promise for practical applications in oily wastewater treatment.