Bifunctional Membrane Research Articles

In-situ impedance diagnosis experiment and equivalent circuit modeling based on distribution of relaxation time method for unitized regenerative proton exchange membrane fuel cells

The Distribution of Relaxation Times (DRT) method provides a powerful approach for analyzing Electrochemical Impedance Spectroscopy (EIS) in electronic components, enabling clear separation of different impedance types and accurate equivalent circuit modeling. In this study, the DRT method was applied to unitized regenerative proton exchange membrane fuel cells (UR-PEMFCs) for the first time, establishing an impedance quantification model for in-situ diagnostics of multiple impedances. This foundational framework supports future durability testing efforts. In-situ impedance diagnostics were conducted in both Fuel Cell (FC) and Electrolytic Cell (EC) modes using a custom mode-switching platform. Results show that under constant electrode conditions, the bifunctional membrane electrode enhances round-trip efficiency by 15.75% compared to the constant gas mode. Through DRT imaging in FC and EC modes, impedance information corresponding to distinct relaxation peaks was extracted and assigned based on operational experiments. The three main peaks identified in both modes were attributed to proton transfer impedance, charge transfer impedance, and mass transfer impedance. Additionally, variations in operating conditions led to the appearance of new transport mechanisms within the charge transfer impedance. In FC mode, the DRT-based equivalent circuit model achieved precise fitting. Applying DRT to UR-PEMFCs improves water and bubble management, offering efficient optimization pathways and valuable guidance for cell design, operational parameter refinement, and durability monitoring.

V2CTx MXene for sustainable wastewater treatment: Inspired by the exoskeletons of nature’s microscopic architects

The polyvinylidene fluoride (PVDF) membrane is prepared and its wetting properties are tuned through polyvinyl alcohol (PVA) coating. Subsequently, a layer of Vanadium Carbide MXene (V2CTx) is derived from etching the Aluminium layer from Vanadium Aluminium Carbide (V2AlC) MAX phase. The V2CTx MXene is deposited onto the PVA-coated PVDF through vacuum deposition. This incorporation ensures that the V2CTx is deeply rooted within the substrate bolstering its separation capabilities with an underwater superoleophobic and in-air superhydrophilic surface. The bi-functional membrane serves as an essential experimental validation for the application of V2CTx MXene in treating oily wastewater. It efficiently separates oil and water while aiding in aqueous-oil demulsification, providing an innovative solution for wastewater treatment. Additionally, this membrane demonstrates effective adsorption of organic contaminants due to the presence of V2CTx MXene, further enhancing its remediation capabilities. Therefore, this work introduces a pioneering approach utilizing V2CTx MXene in treating oily wastewater.

Vapor-phase reduction synthesis of N, S co-doped graphene/MWCNT hybrid membrane for all-solid-state supercapacitors and adsorption of organic pollutants

Owing to the limited reserves of fossil fuels, many researchers are focused on seeking advanced materials to relieve the drawbacks caused by the imbalance between the supply and demand of fossil fuels. In this study, a N, S co-doped graphene/multi-walled carbon nanotubes hybrid membrane (GMHE) was synthesized by flow-directed assembly followed by vapor-phase reduction. The resulting hybrid membrane not only exhibited excellent capacitance performance, but also good adsorption capacity for organic pollutants owing to its high electrochemical activity, well-developed pore structure, and rich surface state. The assembled GMHE all-solid-state symmetric supercapacitor delivered a high power density of 6000 W·kg−1 at an energy density of 16.0 W·h·kg−1 and superior capacitance stability (retaining 97.2 % of its initial capacitance value at 3 A·g−1). The adsorption capacity of the GMHE for organic pollutants was 50 times (chlorobenzene) its own mass. In addition, the hybrid membrane exhibited remarkable reusability over in adsorption–combustion cycles. The judiciously designed bifunctional membrane material developed herein can be directly applied in energy storage and oil pollution cleanup, supporting sustainable economic development.

Polyphenol assisted assembly of prussian blue analogs nanocrystals decorated 3D GO functional microspheres for polymer fiber bifunctional membrane with high oil-water emulsion permeability and powerful photocatalytic self-cleaning ability

Due to the intricate components of wastewater and physical stacking of graphene oxide (GO), the current GO membranes exhibit the fatal defects of low porosity and poor anti-fouling ability. Herein, a three dimensional (3D) FeCo-PBA@GO functional microsphere was constructed via anchoring GO nanosheets onto hard template of 3D polymethyl methacrylate (PMMA) microsphere driven by hydrogen bond and van der Waals force. On this basis, the Prussian blue analogs nanocrystals (FeCo-PBA) grew in situ on such functional microsphere and further assembled onto porous polyacrylonitrile (PAN) fiber mat through the tannic acid assisted spraying technique, resulting in highly permeable and photocatalytic self-cleaning FeCo-PBA@GO/PAN fibrous composite membrane. Interestingly, the unique 3D nanostructure of FeCo-PBA@GO microsphere arranging on membrane surface effectively prevented the dense physical stacking of GO nanosheets and increased the oil repellence property, thereby regulating the water channel and breaking through permeability limitation of membrane. As a result, the composite membrane exhibited superior separation fluxes (˃3029 L m−2 h−1) for different oil/water (O/W) emulsions, with rejection rate above 99.0 %. Owing to rich active sites and enhanced electron/mass transport property of FeCo-PBA functional layer, the composite membrane could effectively degrade various dyes by peroxymonosulfate (PMS) activation, with the degradation efficiency of 93.1–96.9 % within 40 min and demonstrated favorable antifouling and photocatalytic self-cleaning ability after cycling separation of O/W emulsion. In addition, the generated multiple reactive oxygen species and photocatalytic mechanism were proposed. This work provides a versatile pathway to prepare multifunctional GO advanced membranes for large-scale treatment of complex emulsified oily wastewater.

Preparation of Fe/Co bimetallic oxide loaded hydrophobic & catalytic bifunctional membrane and its catalytic performance in sulfite oxidation

Sulfite oxidation is critical for the stable operation of desulfurization process and the treatment & recovery of desulfurization by-products. The Fe and Co oxides modified super hydrophobic layer was prepared on tubular ceramic membranes using hydrothermal synthesis and surface modifications to realize the combination of the membrane catalysis and membrane aeration. These two oxides were approximately two-layer distributed on the membrane surface, among which the Fe2O3 located in the bottom layer and the Co3O4 located in the upper layer. The catalytic rate of the bifunctional membrane was about 5.8 times than that of the original ceramic membrane, which was decreased with the increasing of Fe/Co ratio and declined after an initial rise with the increase of urea and cetyltrimethylammonium bromide. The conjoint effect of Fe and Co could improve the catalytic performance and reduce the dissolution loss of catalyzer. The oxidation rate tended to be constant after a 15 % decrease in 7 times experiments.

Ion-Selective Transport Promotion Enabled by Angstrom-Scale Nanochannels in Dendrimer-Assembled Polyamide Nanofilm for Efficient Electrodialysis.

The ion permeability and selectivity of membranes are crucial in nanofluidic behavior, impacting industries ranging from traditional to advanced manufacturing. Herein, we demonstrate the engineering of ion-conductive membranes featuring angstrom-scale ion-transport channels by introducing ionic polyamidoamine (PAMAM) dendrimers for ion separation. The exterior quaternary ammonium-rich structure contributes to significant electrostatic charge exclusion due to enhanced local charge density; the interior protoplasmic channels of PAMAM dendrimer are assembled to provide additional degrees of free volume. This facilitates the monovalent ion transfer while maintaining continuity and efficient ion screening. The dendrimer-assembled hybrid membrane achieves high monovalent ion permeance of 2.81 mol m-2 h-1 (K+), reaching excellent mono/multivalent selectivity up to 20.1 (K+/Mg2+) and surpassing the permselectivities of state-of-the-art membranes. Both experimental results and simulating calculations suggest that the impressive ion selectivity arises from the significant disparity in transport energy barrier between mono/multivalent ions, induced by the "exterior-interior" synergistic effects of bifunctional membrane channels.

Cation-permselective membranes enabled by synergistic ion channels of crown ethers and anionic sites

The specific interaction existing between crown ethers (CEs) and alkali metal ions serves a dual purpose in both facilitating the selective ion transport across polymeric membranes and exerting a significant influence on the microstructure by means of non-covalent interactions among the CEs. In this study, synergistic ion channels featuring a bi-periodic structure are constructed using both CEs and sulfonate (−SO3−) groups. It is observed that the membranes with reduced water uptake demonstrate enhanced ion permselectivity, attributable to the partial dehydration of ions during binding behavior. The bi-functional membranes exhibit excellent permselectivity for alkali metal ions, particularly K+, Na+ and Li+ ions, over Mg2+ ions. The permselectivity sequence of K+>Na+>Li+ and the notably superior K+/Mg2+ permselectivity, reaching up to 244.43, is attributed to the relatively stable CE-K+ complex within the channels, as supported by molecular dynamics simulations. Specifically, the fabricated membrane is successfully utilized in a 4-stage “ion-distillation” process, achieving an impressive separation factor for K+/Mg2+ over 40,000. The investigation of the synergy between CEs and anionic sites provides valuable insights for the development of cation-permselective membranes.

Preparation of Antioxidant and Antifouling Ultrafiltration Membrane by Co-blending Eugenol with Polyethylene Glycol-Modified Polyvinylidene Fluoride

Polyvinylidene fluoride-graft-polyethylene glycol methyl acrylate (PVDF-g-PEGMA) was prepared by grafting PEGMA onto PVDF using a homogeneous irradiation grafting method. After incorporating various concentrations of eugenol, a natural antioxidant component of clove oil, the membranes were fabricated through non-solvent induced phase separation. The results indicated that the addition of eugenol did not alter the inherent properties of the membrane but slightly reduced the pore size and water flux. The cyclic flux test showed that eugenol did not compromise the anti-fouling performance of the membrane, with the flux recovery ratio exceeding 93%. The antioxidant performance test revealed that eugenol enhanced the membrane’s capacity to remove free radicals and imparted oxidation resistance in NaClO solution, making the modified membrane suitable for use in oxidizing environments. This study successfully demonstrated a simple method to prepare a bifunctional membrane with anti-fouling and antioxidant properties, potentially extending its service life and applicability in oxidative contexts.

Bifunctional ratiometric fluorescent membrane containing pyrene-based probe for visual monitoring and efficient removal of Al3+

A bifunctional fluorescent pyrene-based probe, PYR, was designed by incorporating pyridine and phenolic hydroxyl moieties into pyrene fluorophore, which exhibited ratiometric fluorescent response toward Al3+. PYR underwent unique monomer-excimer conversion in ratiometric manner through the formation of a 2:1 coordination complex and accomplished with fluorescent color variation from green to blue. PYR displayed excellent selectivity, high sensitivity (LOD = 0.33 μM), rapid response (<45 s), and good cytocompatibility to Al3+. Notably, a fluorescent cellulose membrane decorated with PYR was successfully developed and applied for accurately quantify of Al3+ in diverse actual samples, and high-efficiency removal (∼96%) of Al3+ from water systems, with sustainable recycling performance up to 10 times. Bifunctional membranes also played an important role in reducing the LOD of Al3+ to 16 nM through the preconcentration process. Therefore, this study is crucial to the development of environmentally sustainable strategy for monitoring and removing pollution.

Iron oxide/poly (vinylidene fluoride-hexafluoropropylene) membranes for lithium-ion battery separator and arsenic removal applications

The here presented experiments report on bi-functional iron oxide (Fe3O4)/poly (vinylidene fluoride-hexafluoropropylene) - PVDF-HFP porous membranes prepared through thermal-induced phase separation (TIPS) for As(III) and As(V) adsorption and posterior second life as a lithium-ion battery (LIB) separator considering a circular economy paradigm. The bi-functional membranes' physical-chemical properties, their ability to remove arsenic species from aqueous solution, and subsequent performance as a battery separator for LIB were assessed. A highly porous structure characterises the membranes, and the incorporation of nanoparticles (NPs) does not change the chemical and thermal properties of the polymeric membrane. The membrane with 10 wt% of Fe3O4 revealed the ability to remove approximately 81% and 82% of arsenite and arsenate from water, presenting equally remarkable reusability after five cycles, with an efficiency loss below 12%. The second life of this material as a battery separator revealed an ionic conductivity of 2.3 mS.cm-1 and a discharge capacity of 60 mAh.g-1 at 2 C-rate. This work proves the multifunctionality of the membranes and the possibility of a second life.

Sulfonated Poly(2,6-dimethyl-1,4-phenylene ether)-Modified Mixed-Matrix Bifunctional Polyelectrolyte Membranes for Long-Run Anthrarufin-Based Redox Flow Batteries.

The resurgence in designing polyelectrolyte membrane (PEM) materials has propound grid-scale electrochemical energy storage devices. Herein, we report on studies corroborating the synergistic influence of ionic domain microstructure modification and intercalation of telechelic bis-piperidinium-functionalized graphene oxide (GO) to fabricate stable bifunctional membranes from sulfonated poly(2,6-dimethyl-1,4-phenylene ether) (sPPE) for efficient anthrarufin-based alkaline redox flow batteries. A critically long-lasting quest on alkaline stability and -OH conductivity dilemma in hydrocarbon-based PEMs is meticulously resolved via a bifunctional ion-conducting matrix. Preferential studies on hydrophilic domain distribution in sPPE suggest that, with high microphase homogeneity, higher specific capacity retentions are achievable during galvanostatic charge-discharge (GCD) analysis. Moreover, the low-capacity issues were overcome by improving the redoxolyte-membrane interface affinities incorporating bis-piperidinium-bearing graphene oxide (bis-QGO). Consequently, at 1.0 and 2.0 wt % intercalation of bis-QGO, the bifunctional polyelectrolyte membranes (BFPMs) impart lowest overpotentials of 93 mV (for BFPM-1.0) and ∼100 mV (for BFPM-2.0) which are ∼43 and 40% lower than that of Nafion-117 (i.e., ∼164 mV). Furthermore, the efficiency of BFPMs, viz., the Coulombic, voltage, and energy efficiencies, was ∼95-98%, ∼85%, and ≥80% at 20 mA cm-2, respectively. In long-cycling operations, the GCD profile evidenced ∼99% efficiency retention over 450 cycles and illustrated reproducible rate capability. Finally, the polarization studies of BFPMs revealed ∼54% higher peak power density (87.5 mW cm-2) delivery than Nafion-117 (∼57 mW cm-2). We believe that this strategic designing approach could offer newer and simple avenues to avail high-performance BFPMs at low intercalation loads for alkaline electrochemical energy storage and related applications.

Designing anti(-bio)fouling membranes with synergistic grafting of quaternized and zwitterionic polymers through surface initiated atom transfer radical polymerization

Membrane-based filtration technologies have significant potential to address the global problem of freshwater scarcity. However, fouling, caused by nonspecific adsorption of foulants and microbiological growth during filtration, remains a considerable concern. To address this, a rational surface design method comprising bifunctional coating with both defensive and attacking techniques has been devised, which can successfully decrease fouling and biofouling. To generate a bifunctional membrane, a single-step surface-initiated atom-transfer radical polymerization (SI-ATRP) of monomers with zwitterionic and quaternized imidazolium moieties was done on a polydopamine (PDA) primed polyvinylidene fluoride (PVDF) membrane. The PDA layer’s catechol functionalities provided abundant anchoring sites, allowing the grafting of a dense polymer layer on the membrane. The addition of active zwitterionic and quaternized imidazolium moieties in the grafted polymer chains resulted in very low fouling and microbiological species death. Extensive antifouling studies revealed that the functionalized membranes have excellent flux recovery (>93%), low irreversible fouling (<8.5%), and long-term filtration stability. This surface functionalization strategy based on a bifunctional unit represents a significant advancement in fouling mitigation by minimizing membrane-foulant interactions and killing adhered bacteria, with the potential to significantly broaden the range of membrane-based filtration applications and contribute to more efficient and sustainable water purification processes.

Reinforcing conversion of polyselenides via a bifunctional blocking layer for efficient Li-Se batteries

Lithium-selenium (Li-Se) batteries possess high volumetric capacity and have attracted considerable attention as a high energy storage system. However, the shuttling of polyselenides seriously worsens the electrochemical performance and retards their application advancement. Herein, we engineered a bifunctional membrane consisted of polyethylenimine derived carbon quantum dots (Cdots) to efficiently restrict the shuttling of polyselenides under a high Se loading (Se≈70 wt%) and promote Li-Se conversion kinetics, which can be accounted by the greatly accelerated transportation of charge carriers and dipole–dipole interactions between polar moieties and long-chain polyselenides (Li2Se4 and Li2Se6) as corroborated by theoretical calculations. Thus, the bifunctional membrane endows Li-Se batteries with a specific capacity of 658.60 mAh g−1 at 0.1 C and coulombic efficiency of 97.8% in average, and demonstrates the effectiveness of defect-rich Cdots on suppressing polyselenides shuttling and reinforcing Li-Se conversion kinetics in augmenting the battery’s durability and efficiency.Graphical

Investigation of the Performance and Durability of Reactive Spray Deposition Fabricated Electrodes on a Bifunctional Membrane for Alkaline Water Electrolysis and CO2 Reduction Reaction

Alkaline water electrolysis (AWE) is a promising technology for carbon capture [1]. Anion exchange membrane water electrolyzers (AEMWEs) utilize low-cost, non-precious metal materials, providing an economically viable alternative to more expensive proton exchange membrane water electrolyzers (PEMWEs). While PEMWEs can operate at much higher current densities, they require noble metal catalysts and titanium components for the high potential environment anode [1]. The implementation of a bipolar membrane (BPM) will allow both HER and OER to occur under kinetically favorable conditions [2, 3] by combining both thin AEM and thin PEM layers within a single membrane. AEMs, PEMs, and BPMs have been tested in CO2RR electrolyzers [4]. The BPM may provide a pathway to combine the advantages of both AEMs and PEMs for CO2 reduction. Altering both the membrane and CCM is a focus in the research and development in CO2RR electrolyzers. Lee et al. [5] explored the use of a porous membrane for CO2 reduction. While work can be done to improve performance and crossover, the porous membrane provided excellent mechanical properties and good economic potential.There has been some work done on developing bifunctional membranes for water electrolysis and CO2 reduction [3, 6, 7]. Two key issues with operation of a CO2RR electrolyzer with a BPM is the reactant CO2 that is lost to the AEM and PEM membrane layer interface and the instability of the cell. Both issues contribute to a significant decrease in performance and faradaic efficiency in product conversion. Development of the BPM, both on the membrane’s fabrication and configuration, and electrode layers, needs to be explored to reach higher performances and longer lifespans.In this work, reactive spray deposition technology (RSDT) was used to fabricate electrodes on a UConn fabricated bipolar membrane. Testing of each configuration was conducted as both an AEM water electrolyzer and CO2RR electrolyzer. Polarization, electrochemical impedance spectroscopy, electrochemical equivalent circuits, and distribution of relaxation times were used to investigate cell performance and durability.

Tuning the reactivity of Ni/MoS2 membrane for efficient methane pyrolysis and hydrogen production: A multi-scale study

This study investigates the performance of a Ni-coated MoS2 membrane for catalysis and separation in the methane pyrolysis process. Bifunctional membranes provide a low-energy and low-emission hydrogen generation and purification production process. To elucidate the reaction mechanism of the prepared membrane, a combined experimental and computational approach was employed using ReaxFF molecular dynamics simulations. The results demonstrate excellent catalytic and separation performance of the membrane, which was achieved through the increased specific surface area and reduced pore size of the MoS2 flower cluster. The Ni coating of MoS2 was found to attract methane, and transfer electrons to destabilize the CH bond, thus enhancing methane deep crack. In addition, the prepared membrane successfully blocked methane through Mo-edge defects, while promoting methane pyrolysis and driving H proton transportation for the H2 formation. The permeation test verified the excellent CH4/H2 separation performance of the ZSM-5 membrane coated with Ni and MoS2. This work provides theoretical and experimental guidance for the development of bifunctional membranes for methane pyrolysis to hydrogen generation, which has potential to reduce energy cost and greenhouse gas emissions.

Bifunctional electrospun poly (L-lactic acid) membranes incorporating black phosphorus nanosheets and nano-zinc oxide for enhanced biocompatibility and antibacterial properties in catheter materials

For several decades, urinary tract infections caused by catheter-associated devices have negatively impacted not only medical device utilization, but also patient health. As such, the creation of catheter materials with both superior biocompatibility and antibacterial properties has become necessary. This study aimed to produce electrospun membranes based on polylactic acid (PLA) with the incorporation of black phosphorus nanosheets (BPNS) and nano-zinc oxide (nZnO) particles, as well as a mixture of both, in order to design bifunctional membranes with enhanced bioactivity and antibacterial features. The optimum spinning process was determined through examination of various PLA mass concentrations, spinning solution propelling speeds, and receiving drum rotating speeds, with emphasis on the mechanical properties of PLA membranes. Additionally, the antibacterial properties and cytocompatibility of the ZnO-BP/PLA antibacterial membranes were explored. Results demonstrated that the ZnO-BP/PLA antibacterial membranes displayed a rich porous structure, with uniform distribution of nZnO particles and BPNS. With the increase of polylactic acid concentration and the decrease of spinning solution advancing and drum rotation speeds, the mechanical properties of the fiber membrane were significantly improved. Furthermore, the composite membranes exhibited remarkable photothermal therapy (PTT) capabilities when aided by the synergistic effect of BP nanosheets and ZnO. This was achieved through near-infrared (NIR) irradiation, which not only dissipated the biofilm but also enhanced the release capability of Zn2+. Consequently, the composite membrane demonstrated an improved inhibitory effect on both Escherichia coli and Staphylococcus aureus. The results of cytotoxicity and adhesion experiments also indicated good cytocompatibility, with cells growing normally on the surface of the ZnO-BP/PLA antibacterial membrane. Overall, these findings validate the utilization of both BPNS and n-ZnO fillers in the creation of novel bifunctional PLA-based membranes, which possess both biocompatibility and antibacterial properties for interventional catheter materials.

Bioinspired hierarchical colloidal crystal paper with Janus wettability for oil/water separation and heavy metal ion removal.

Increasing attention has been paid recently to superwettability and its prospective potential applications in various fields. A new approach towards the establishment of flexible, self-assembled superhydrophobic surfaces with self-reported wettability on a variety of substrates has been advanced. The approach involves the fabrication of a dense monolayer of photonic crystal films that possess a layered structure with superior adhesion at the liquid-gas-solid interface. Thus, the resulting hierarchical photonic crystal film with a structurally hydrophobic surface offers a promising addition to the creation of durable and flexible superhydrophobic surfaces across a variety of substrates that exhibit the self-reported wettability. Furthermore, a bifunctional membrane that can effectively remove oil and adsorb heavy metal ions contained in wastewater has been developed for potential use in large-scale industrial wastewater treatment. This research sheds fresh light on the application of bionics and the lotus and mussel functions in oil/water separation.

Poly(vinyl alcohol) mediated bifunctional ZIF-BN nanocomposite for the high-selectivity H2 separation membrane

We combined the advantages of the 2-methylimidazole zinc salt (ZIF-8) and hydroxylated boron nitride (OH-BN) materials to prepare a new bifunctional separation material, namely ZIF-BN. In this, spherical ZIF-8 materials fill the macroporous structure of OH-BN sheets by coordination bonds due to the edge effect. Furthermore, a series of ZIF-BN/PVA membranes were prepared using the vacuum-assisted filtration of the layer-by-layer for the gas separation study. The trace amounts of PVA connect adjacent ZIF-BN sheets through hydrogen bonds, without covering the pore structures of ZIF-8 materials. Based on this exclusive strategy for preparing membranes, the obtained membranes exhibit superior H2 separation performances. Compared with the pure PVA membrane, the H2 permeability, H2/CO2 selectivity, and H2/N2 selectivity of the ZIF-BN/PVA-8 membrane have increased (54, 13, & 12)-fold, to (600 Barrer, 97.2, & 173.6), respectively. This strategy provides a facile way to design new bifunctional membranes for gas separation applications.

Quantitative assessment and optimization of bi-functional membrane for remediation of Cr(VI) from wastewater

This paper explores the innovative approach of using a green route synthesized cost-effective bi-functional to eliminate toxic hexavalent chromium commonly found in tannery wastewater by using an integrated application of membrane and photocatalyst. Contaminated wastewater is firstly passed through bi-functional ultrafiltration membranes to retain hexavalent chromium and further reducing the toxicity of rejected water having high concentrations of Cr(VI) by photocatalytic reduction into Cr(III) in the presence of sunlight using the same membrane as photocatalyst film. Conditions governing the separation process such as solution pH, nanoparticle loading in polymer matrix, and concentration of Cr(VI) have been optimized to maximize the % rejection and photocatalytic reduction to Cr(III). The purpose of this work was to optimize the process condition through the use of the response surface method (RSM) that governs the process. RSM analysis concludes that excellent rejection of 91.58% and reduction of 87.02% is possible at the predicted pH (5.55), particle loading (2.14%) and Cr(VI) concentration (25 mg/L).

Electrically conductive TiO2/CB/PVDF membranes for synchronous cross-flow filtration and solar photoelectrocatalysis

Combining photocatalysis (PC) and membrane filtration (MF) has emerged as an attractive technology for water purification, however, the water purification efficiency and membrane fouling are still challenging. Herein, we report a novel photoelectrocatalytic (PEC) membrane mediated by a ternary polyvinylidene fluoride (PVDF)-carbon black (CB)–TiO2 composite conductive membrane synthesized by a phase inversion method assisted by the mixed surfactants of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). The resultant electrically conductive TiO2/CB/PVDF membrane features a homogeneous surface with obvious pore size of 20–150 nm, a thickness ∼116 μm, and an average resistivity as low as ∼3.165 Ω∙m. The cooperation of PVP and SDS surfactants dramatically improves the organic-inorganic interactions and thus eventually enhances the porosity, stability of porous structure, mechanical stability, and conductivity and electrochemical properties of the hybrid membrane. Upon the solvent evaperation of the wellblended casting solution and the phase inversion, TiO2/CB preferentially exist on the surface of PVDF membrane, enabling the efficient PEC degradation of organic pollutants. The synergistic coupling of TiO2 and CB in PVDF membrane results in efficient PEC properties with bi-functional membrane antifouling and enhanced water purification in azo dyes decolorization under the stationary mode and in our lab-made continuous cross-flow PEC system, superior to those by photocatalysis and electrocatalysis. The developed synchronous MF and PEC system mediated by the conductive TiO2/CB/PVDF membrane proves to a feasible route to improving the self-cleaning properties of the polymer membrane while simultaneously increasing the water decontaminating efficiency.