Flat Sheet Membranes Research Articles

Effects of Preparation Conditions on Performance of PES:PEG Flat Sheet Membrane for MG Dye Separation

This study deals with the morphology and performance properties of a novel thin flat sheet ultrafiltration membrane; Malachite Green (MG) dye filtration behavior was evaluated in the cross-flow filtration system. The prepared membranes included the incorporation of 16 wt. % of polyether sulfone (PES)/DMF and 5 wt.% of Polyethylene Glycol (PEG) via the phase inversion process. Adding PEG decreased the internal concentration polarization, improved the membrane hydrophilicity, changed pore morphologies, and enhanced membrane performance. The SEM and AFM tests were used to characterize the composition and structure of the membrane. With different casting conditions, the membrane shape changed. The effect of membrane thickness (100, 150, and 200) µm and coagulation bath properties temperature (15, 25, and 35) °C and composition DMF (10, 20, 30 %) in water on the fabricated membrane were investigated. To evaluate the membrane filtration performance, the fabricated membranes were applied in an ultrafiltration system to treat Malachite Green dye solution at a concentration of (10 ppm) as a model pollutant. Based on the obtained results, the ideal membrane parameters were150 µm in thickness, 35°C in temperature, and 10% in composition DMF; the removal efficiency was observed to be (94.5%, 93%, and 99.5%) while the permeate flux (45, 35 and 30) LMH, respectively.

Comparison of Hollow Fiber and Flat Sheet Membranes for Removing TDS and Turbidity of Palm Oil Mill Effluent Wastewater

The most significant pollutant produced from agricultural industry in Kalimantan, Indonesia is Palm Oil Mill Effluent (POME). Due to the high levels of suspended particles and organic matter, POME has become a brownish color with high turbidity, color, chemical oxygen demand, and oil and grease content. To recycle the POME wastewater as clean water, these pollutants must be eliminated. In this study, we compare the effectiveness of hollow fiber (HF) and flat sheet (FS) membrane to remove total dissolved solid (TDS) and turbidity from POME with varied filtration pressure. HF and FS membrane were prepared from PVDF and nylon66 polymer, respectively. The PVDF HF membrane was modified using TiO2 and SBE (spent bleaching earth) to improve HF membrane properties to maintaining fouling. Meanwhile, FS membrane was added by pectin to increase the hydrophilic properties. Overall membrane’s morphology was determined by Scanning Electron Microscopy (SEM) to investigate the membrane structure. Both of HF and FS membrane were operated via ultrafiltration (UF) under cross flow system. The filtration pressures were varied at 1-3 bar and followed by flux and rejection evaluation. The results show both HF and FS membranes has stability flux. In addition, TDS rejection up to 25% while turbidity is excellent high over 95% for all membranes. The fabrication HF membrane has finger like-sponge structure and FS membrane exhibits sponge asymmetric structure. Overall, all membranes perform highest water flux (FS membrane) while highest rejection conducted by HF membrane for POME wastewater treatment.

Characteristics of dissolved organic matter and their role in membrane fouling during simultaneous sludge thickening and reduction using flat-sheet membranes.

Four parallel simultaneous sludge thickening and reduction reactors using flat-sheet membranes were employed for the aerobic digestion of sludge to explore the characteristics of dissolved organic matter and its membrane fouling effect. During the initial 8 days of using flat-sheet membranes for simultaneous sludge thickening and reduction (MSTR), a notable increase was observed in the concentrations of humic acids and compounds that resemble soluble microbial by-products in the effluent. Subsequently, a fluctuating trend in humic acid levels ensued, accompanied by a gradual decline in soluble microbial by-product-like substances. Post the initial 8-day period, the capillary suction time (CST) rose from approximately 400s to over 800s, the viscosity increased from 20mPas to 38mPas, and the membrane resistance increased from roughly 6.0e+11m-1 to approximately 9.0e+11m-1. This phenomenon can be attributed to the clogging of pores by foulants whose size is similar to that of the membrane pores leading to the accumulation and deposition of macromolecules and larger particulates forming gel layers and cake layers. The interplay among diverse microorganisms engenders functional modules, collectively influencing the distribution and characteristics of dissolved organic matter within the MSTR. These microorganisms exert their metabolic effects individually and interact reciprocally, creating synergistic and inhibitory mechanisms. Notably, the synergistic interactions among microorganisms predominated, culminating in an enhanced effluent quality within the system.

Use of green polar aprotic solvents TamiSolve® NxG, DMSO and methyl-THF for the synthesis of asymmetric polyimide-based biogas purification membranes

Valorization of biogas to biomethane through membrane-based purification of its multi-component stream primarily consisting of CH4 and CO2, holds significant potential as a crucial renewable energy source. Industrial membrane units classically comprise of membranes synthesized using non-solvent induced phase separation (NIPS), with polymer processing typically performed using conventional solvents, such as N-N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), etc. However, use and subsequent waste handling of these solvents present significant hazards, due to their toxicological nature, therefore calling for a shift to employ safer and ‘greener’ materials to facilitate sustainable production of these membranes. In current work, a novel and sustainable methodology for synthesis of CO2/CH4 gas separation flat-sheet asymmetric membranes was developed with commercially available Matrimid® 5218 polyimide, using TamiSolve® NxG, dimethylsulfoxide (DMSO) and 2-methyltetrahydrofuran (MeTHF) as green solvent medium. NIPS thermodynamic and kinetic aspects of the novel system were fundamentally analyzed through determination of ternary phase diagrams and viscosity profiles. Membranes were systematically tested for gas separation performance by varying Tamisolve-DMSO-MeTHF solvent ratios. Mixed gas CO2/CH4 separation factors in the range of 13 to 41, along with CO2 permeances upto 186 GPU were achieved. Furthermore, chemical crosslinking was applied in view of plasticization resistance of the membranes. Matrimid® membranes crosslinked with hyperbranched polyethylenimine (PEI) successfully displayed stability against CO2-induced plasticization upto CO2 feed partial pressures of 22 bar. The developed membrane synthesis method provides a sustainable framework for synthesizing polyimide-based membranes with tunable gas separation performances.

Study of Polysulfone-Impregnated Hydroxyapatite for Ultrafiltration in Whey Protein Separation.

Polysulfone (Psf) ultrafiltration flat-sheet membranes were modified with hydroxyapatite (HA) powder during preparation using the wet-phase inversion method. HA was incorporated to enhance the protein separation capabilities. The asymmetric Psf membranes were synthesized using NMP as the solvent. Through Scanning Electron Microscopy (SEM) analysis, it was revealed that HA was distributed across the membrane. Incorporating HA led to higher flux, the improved rejection of protein, and enhanced surface hydrophilicity. The permeability flux increased with HA concentration, peaking at 0.3 wt.%, resulting in a 38% improvement to 65 LMH/bar. Whey protein separation was evaluated using the model proteins BSA and lysozyme, representing α-Lactalbumin. The results of protein rejection for the blend membranes indicated that the rejection rates for BSA and lysozyme increased to 97.2% and 73%, respectively. Both the native and blend membranes showed similar BSA rejection rates; however, the blend membranes demonstrated better performance in lysozyme separation, indicating superior selectivity compared to native membranes. The modified membranes exhibited improved hydrophilicity, with water contact angles decreasing from 66° to 53°, alongside improved antifouling properties, indicated by a lower flux decline ratio value. This simple and economical modification method enhances permeability without sacrificing separation efficiency, hence facilitating the scalability of membrane production in the whey protein separation industry.

Integrated membranes system for water application in microbiology/molecular biology

An integrated membrane filtration system was developed to make water purity suitable for microbiology/molecular biology research. Water samples were collected from outlets in different buildings of the National Research Center and analyzed for their composition before filtration. An integrated membrane system was developed based on mathematical modeling. Flat sheet membranes were produced, including microfiltration, ultrafiltration, and nanofiltration membranes. The flat sheet membranes were converted to a spiral wound module filter to simulate the local market filters and applied in the integrated membrane system that was designed and installed. The produced water was analyzed and compared to molecular-grade water used in different molecular biology/microbiology applications. Both PCR, agarose gel electrophoresis, bacterial liquid cultures, and viral propagation indicated that treated water using the herein-developed system exhibited comparable performance to the molecular grade water provided with imported reagent kits. So, this research can offer a promising solution for producing high-quality water suitable for sensitive laboratory applications.

Wet-coating amino-functionalized PDMS interlayer boosting thin film composite membranes for efficient CO2 separation

Membrane separation is in the spotlight as one of the most cost-effective technologies without chemicals for carbon capture. This work aims to fabricate thin film composite (TFC) membranes for boosting CO2 separation. Commercial polysulfone (PSf) flat sheet membranes pre-treated with ethanol solutions were used as support materials by coating with amino-functionalized cross-linked polydimethylsiloxane (PDMS) interlayer. It is worth noting that the developed amino-functionalized PDMS interlayer based on a novel wet-coating method to avoid the penetration of coating solution, which provides better compatibility with the coated polyamide selective layer and also the facilitated transport for CO2 permeation. A thin CO2-selective layer was obtained by interfacial polymerization (IP) between trimesoyl chloride (TMC) in the organic phase and diethylene glycol bis(3-aminopropyl) ether (DGBAmE or EO3) in the aqueous phase to enhance the CO2/N2 selectivity. Both the IP process and the membrane preparation parameters such as heat-treatment temperature, and monomer concentration were systematically optimized. It was found that the best membrane prepared with 9.9 mmol/L TMC monomer solution presents a CO2 permeance of 81 GPU and a CO2/N2 selectivity of 65, which was significantly enhanced from the non-selective supports. This work provides a facile approach for tuning the TFC membrane performance for CO2 separation and can be extended to make high-performance membranes for industrial CO2 capture by selecting more permeable supports.

Synthesis, characterization, and performance of MXene-modified PVC membranes for organic and inorganic separation

This study explores the transformation of polyvinyl chloride (PVC) flat sheet membranes for the first time using MXene, a hydrophilic two-dimensional (2D) nanosheet, to enhance ultrafiltration (UF) performance for wastewater treatment. The loading of MXene in the PVC solution was adjusted from 0 to 0.5 g in order to create modified membranes. The properties and performance of these membranes were thoroughly analyzed using field emission scanning electronmicroscopy (FESEM), contact angle (CA) measurements, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), water permeation flux, Bovine serum albumin (BSA) rejection, and Pb metal ions removal tests. Among the developed membranes, the N2-modified PVC membrane, with 0.4 g of MXene, exhibited the most favorable characteristics, including a contact angle of 65.77° and a porosity of .84.8 %. This membrane achieved the highest clean water permeation flux of 201.3 LMH, along with a 99.9 %, 91.03 % BSA and Pb metal ions rejection rate respectively, and a flux recovery ratio (FRR) of 90.2 %. The incorporation of MXene nanosheets significantly enhanced membrane efficiency compared to neat PVC membranes, demonstrating the promising capabilities of MXene-modified PVC membranes for effective wastewater treatment.

Removal of emerging organic micropollutants from real hospital wastewater by modified ultrafiltration membranes

Membrane biofouling, characterized by the adherence and growth of microorganisms on the surface of a membrane, poses a significant challenge to the effectiveness of membrane bioreactor (MBR) technology. Enhancing anti-biofouling characteristics, particularly the prevention of bacterial adhesion to the membrane, is crucial for the sustained operation of MBR over the long term. One of the most popular methods for enhancing these characteristics is surface modification. In this study, two distinct concentrations of 150 µM and 300 µM of BisBAL −a chelate derived from bismuth with strong antibacterial action on a variety of microorganisms- were added to polymeric membrane solutions. Using these solutions, flat sheet (FS) and hollow fiber (HF) membranes were produced via the phase inversion method to examine their removal capabilities for micropollutants in a real hospital wastewater. Caffeine (CAF), Paracetamol (APAP) and Ciprofloxacin (CPFX) were observed as target micropollutants during a pilot-scale MBR operation. The chemical modification of the membranes enhanced the characteristics of the membrane material. Pure water flux values increased while contact angles were decreased in modified membranes When compared to bare membranes, BisBAL-added modified membranes were observed to reject CAF, APAP and CPFX more effectively. When 150 and 300 µM BisBAL is added to FS and HF membranes, the rejection efficiencies of CAF and APAP reached their maximums, exceeding 80 %. Remarkably, CPFX rejection in the case of FS membranes added with 300 µM reached about 30 %, whereas it surpasses 80 % in the case of HF membranes added with the same concentration. The mechanism behind the rejection of micropollutants by the membranes was determined to be adsorption. In addition to their enhanced resistance to biofouling, the new potential of these modified membranes was also demonstrated. The results suggested that membranes modified with 300 µM BisBAL were particularly optimal for the pilot-scale MBR operations in the future, with HF membranes generally outperforming FS membranes.

Impact of polyimide on the recycling of waste expanded polystyrene into flat-sheet filtration membrane

Impact of polyimide on the recycling of waste expanded polystyrene into flat-sheet filtration membrane

Scaling and wetting resistant silica nanoparticle grafted multi-scale corrugated omniphobic membranes for membrane distillation

Membrane distillation (MD) is a promising technology for wastewater treatment, but often faces significant challenges of scaling and wetting. Development of advanced omniphobic membranes has been the core research for mitigating scaling and wetting in MD. In this study, a novel fluorinated multi-scale silicon nanoparticle grafted corrugated (FSiC-PVDF) membrane (water contact angle 179.5 ± 0.3°) was prepared and explored for enhancement of anti-scaling performance by calcium sulfate and anti-wetting performance by sodium dodecylsulfate (SDS). Silica nanoparticles (SiNPs) were synthesized and covalently bonded to the surface of the corrugated membrane and the surface energy was further reduced via chemical fluorination. Flat-sheet membrane (F-PVDF) and corrugated membrane (C-PVDF) were compared. Results showed that compared to the previous study of grafting SiNPs on flat membranes directly, FSiC-PVDF exhibited superior flux (21.1 kg/(m2·h)), and it can consistently demonstrate stable water flux and quality even at high calcium sulfate and SDS concentrations. The F-PVDF experienced significant declines in performance, and the C-PVDF showed limited improvement in scaling and wetting resistance. Corrugation pattern contributed to a larger evaporation area and higher velocity near the membrane surface, thus reducing crystal deposition and heterogeneous nucleation on the surface. The combination of corrugation and SiNPs resulted in a stable Cassie-Baxter wetting state, reduced solid-liquid interface areas, and created slippage conditions that minimized the impact of contaminants on MD performance. These findings indicated that FSiC-PVDF membranes offer significant advantages for MD processes, enhancing operational stability and efficiency.

Fabrication of TiO2@ZIF-67 metal organic framework composite incorporated PVDF membranes for the removal of hazardous reactive black 5 and Congo red dyes from contaminated water

Novel application of TiO2@ZIF-67 composite incorporated poly (vinylidene fluoride) (PVDF) mixed matrix flat-sheet membranes for treating the water contaminated with hazardous reactive black 5 and congored dyes was the crux of this work. The composite was characterized by FTIR, BET, XRD, zeta potential and particle size, and TGA. The as-synthesized composite was embedded in the PVDF polymeric matrix and flat-sheet-membranes were fabricated adopting the NIPS method followed by the different characterizations like scanning electron microscopy, EDS, elemental mapping, contact angle, atomic force microscopy, surface energy, and XPS. Results of the performance studies showed an enhanced pure water permeability from 150.99 Lm-2h−1 for neat membrane to 261.39 Lm-2h−1 for TZM-2. The reactive black 5 dye was rejected in 97.4 %, 92.2 %, and 84.84 % in acidic, basic and neutral conditions respectively by TZM-2 membrane. Whereas, the PVDF membranes without the composite showed rejections of 83.19 %, 82.5 %, and 72.1 % respectively in acidic, basic, and neutral conditions. The Congo Red dye was rejected in 89.4 %, 95.68 %, and 92.4 % in acidic, neutral and basic conditions respectively by TZM-2 membranes. Whereas, the PVDF membranes without the composite showed rejections of 82.8 %, 91.9 %, and 85.4 % respectively in acidic, neutral and basic conditions.

Extending the applicability of concentration polarization-enabled “click” hydrogel coating of desalination membranes

Reverse osmosis (RO) systems continually struggle with membrane fouling, leading to diminished membrane permeability and therefore elevated energy requirements. Building on prior own research, this study presents further development of an in situ antifouling coating technique for commercial RO flat sheet membranes and spiral-wound modules, deploying a concentration polarization-driven reactive (“click”) coating formation process. Utilizing this approach, zwitterionic (self-synthesized polyacrylates) and nonionic (functionalized “clickable” poly(vinyl alcohol)) coating materials were employed. Relying on comprehensive statistical analysis and the design of experiments (DOE) framework for lab-scale experiments, essential parameters that dictate the efficiency of the coating process were identified. By modulating the extent of concentration polarization, precise control over the permeance of modified membranes and spiral-wound modules was achieved. A robust correlation emerged between the relative permeance change (RPC) post-modification and the relative end permeance change (REPC) during modification. This correlation serves as basis for the real-time prediction and adjustment of final membrane performance, enabled by online flux monitoring during the modification and stopping it a preset REPC value—a relationship substantiated through extensive experiments on both lab-scale and pilot plant platforms. In performance comparisons, the modified membranes consistently surpassed unmodified variants in both selectivity and antifouling resilience. With successful upscaling to commercial TW30-2521 modules in a pilot plant setting, a significant step toward industrial readiness has been made. Overall, this work introduces a scalable, predictable, and controllable in situ coating method for RO membranes and modules that enables balancing enhanced anti-fouling functionality with preserved flux performance at uncompromised solute rejection.

Easy Fabrication of Ultrafiltration Membrane via Polyethersulfone-Fumed Silica

This study investigated the effect of low-concentration fumed silica (FS) in polyethersulfone (PES) membranes. The PES/FS blend membrane was fabricated using a wet phase inversion technique as a flat sheet membrane. Scanning electron microscopy analysis revealed improved pore connectivity and rounder middle structures due to the addition of fumed silica. The experimental results indicated that the fabricated membranes fell within the ultrafiltration range, with pure water flux increasing as fumed silica concentration rose. The pure water flux improved by 64% compared to the native PES membrane. Furthermore, the blend membranes exhibited better selectivity, rejecting pepsin and lysozyme 11% and 19% more efficiently, respectively. Although the low concentration of fumed silica had minimal impact on the water contact angles of the membrane surface, all membranes demonstrated hydrophilicity. This cost-effective approach enhances permeability while maintaining separation characteristics, making it suitable for clean water applications.

Poly(4-methyl-1-pentene)/ polypropylene alloy hollow fiber membrane with high rigidity for blood oxygenation

The oxygenator with hollow fiber membranes (HFMs) is the key component of the extracorporeal membrane oxygenation which allows the blood to be oxygenated and the carbon dioxide to be removed. The poly(4-methyl-1-pentene) (PMP) is recognized as the optimal oxygenated membrane material with high gas permeability coefficient, and the oxygenated membrane fabricated from it has an asymmetric structure that can resist plasma leakage for a long period of time. However, the relatively low rigidity of PMP oxygenated membrane makes it difficult to be processed in subsequent weaving and applications, during which deformation and fracture of HFMs often happen. In this work, the polymer alloy oxygenated membranes are fabricated by blending polypropylene (PP) as a high rigidity reinforcement agent with PMP via thermally induced phase separation (TIPS). Firstly, the effect of the PP content on phase separation structure and crystallization of alloy flat sheet membrane are investigated. When the PP content is 15 wt%, the rigidity of the alloy membrane reinforces dramatically. The elastic modulus and tensile strength of the PMP-PP-15 alloy membrane is 288.5 ± 12.4 MPa and 8.3 ± 0.4 MPa, respectively, which is 275.7 % and 96.7 % higher than that of the PMP membrane. Furthermore, PMP-PP-15 alloy HFM are fabricated under the optimum polymer composition. The elastic modulus of the PMP-PP-15 alloy HFM is 312.6 ± 16.0 MPa, which is 679.6 % higher than that of the PMP HFM and 40.1 % higher than that of the commercial PMP HFM. Meanwhile, the tensile strength and fracture stress are 15.4 ± 0.7 MPa and 186 ± 12.2 cN, respectively, which are both higher than those of the PMP and commercial PMP HFM. In addition, the PMP-PP-15 alloy HFM shows high gas permeability and oxygenation performance. This study might provide a convenient method to achieve rigidity reinforcement of PMP-based oxygenated membranes with great potential for application.

Dialysis nanocomposite membranes based on carbon nanoforms inhibiting blood plasma protein adsorption.

Protein adsorption on medical devices in contact with blood is a significant issue during renal replacement therapy. Main forces determining fouling are the electrostatic interactions between membrane and charged protein, but the dialysis membrane surface charges can be adjusted by modifying the polymer matrix to decrease the blood plasma protein adsorption. In this study, polysulfone membranes (PSU) were modified by incorporation of carbon nanoparticles such as: multiwall carbon nanotubes (2 wt.% MWCNT), graphene oxide (1 wt.% GO), and graphite (5 wt.% GR) during manufacturing process (nonsolvent-induced phase separation, NIPS). The PSU flat sheet membrane was the reference sample. Observed morphology of nanocomposite membranes was similar (SEM imaging); all of them had finger-like pore structure with unimodal distribution of pore size and similar skin-to-support ratio (1:3). The carbon nanoadditives also influenced the surface wettability: hydrophobicity and surface free energy of membranes increased (polar components of energy were reduced, while the dispersive components were increased). The surface charge of nanocomposite membranes increased, when the polymer matrix has been modified with CNT or GR. This significantly affects the adsorption of proteins such as chicken (CSA) and bovine serum albumin (BSA) and reduces blood clotting on the membrane.

Development of Hollow Fiber Membranes Functionalized with Ionic Liquids for Enhanced CO2 Separation.

The combination of CO2-selective ionic liquids (ILs) with block copolymers, such as Pebax 1657, has demonstrated an enhancement of the gas separation capabilities of polymeric membranes. In the current work, the development of composite membranes by applying a thin, concentrated selective layer made of Pebax/imidazolium-based ionic liquids (ILs) is presented. The objective of the experiments was to determine the optimized IL loading and investigate how the alteration of the anion impacts the properties of the membranes. Two membrane configurations have been studied: coated flat sheet membranes, supported on a porous poly(ether sulfone) (PES) layer, as well as composite hollow fiber membranes, supported on commercial polypropylene (PP) hollow fibers. Coated hollow fiber composites were fabricated using a continuous coating method, offering a straightforward scalability in the manufacturing process. The determined mechanical pressure stability of hollow fiber composites reached up to 5 bar, indicating their potential for various industrial gas separation applications. It was found that the Pebax 1657-based coating containing 40 wt % [C6mim][NTf2] yielded membranes with the best gas separation properties, for both the coated flat sheet and the hollow fiber configurations. The CO2 permeance of hollow fibers reached 23.29 GPU, whereas the CO2/N2 ideal selectivity stood at 8.7, suggesting the necessity of the further enhancement of the coating technique, which can be achieved, for example, through application of multiple coatings. Nonetheless, the superior ideal selectivity of the CO2/CO separation, reaching 12.44, gave a promising outlook for further novel membrane applications, which involve the separation of the aforementioned gases.

Composite flat-sheet membrane adsorbent of Li2TiO3-Ethylene-co-vinyl alcohol (LTO-EVAL) for lithium extraction

Composite bead adsorbents have been prevalent for the extraction of Li+ from brines. However, adsorbent beads generally demonstrate declining adsorption capacity and require extended equilibrium time when used repeatedly in absorption/desorption cycles. To overcome this challenge, a novel composite flat-sheet membrane adsorbent based on ethylene-co-vinyl alcohol (EVAL) and Li2TiO3 (LTO) is reported herein for highly efficient Li+ extraction from a geothermal brine. At an optimal LTO loading and membrane thickness, the resulting LTO-EVAL membrane was characterized by a large open macrovoid structure for fast ion transport, a fast adsorption rate that reached equilibrium in 0.5 h, and a high capacity of 96 % of that of the powder. The new membrane adsorbent showed adsorption behavior consistent with the Langmuir model and pseudo-second-order kinetic model. For a geothermal brine with a low lithium concentration, the LTO-EVAL membrane showed stable performance in 13 rapid adsorption/desorption cycles, with adsorption capacity at an average adsorption capacity of 7.3 mg/g and a 70 % adsorption efficiency. The average dissolution rate of Ti4+ was below 0.6 % in each cycle. The structure of the adsorbent material showed no discernable changes in chemical structure as confirmed by XRD and SEM results. With the improved extraction efficiency, the reusable membrane adsorbents would be economically viable in the long run and could potentially serve as the next generation of scalable Li+ adsorption material for brines. Further utilization of membrane adsorbent would lead to new design of adsorption modules and systems with reduced footprint. We need to further optimize the stability of the membrane adsorbents so that loss of Li2TiO3 remain at low level to reduce the lost for lithium extraction from the geothermal brine.

Performance and Environmental Assessment of Biochar-Based Membranes Synthesized from Traditional and Eco-Friendly Solvents.

Water contamination resulting from coal spills is one of the largest environmental problems affecting communities in the Appalachia Region of the United States. This coal slurry contains potentially toxic substances, such as hydrocarbons, heavy metals, and coal cleaning chemicals, and its leakage into water bodies (lakes, rivers, and aquifers) can lead to adverse health effects not only for freshwater bodies and plant life but also for humans. This study focused on two major experiments. The first experiment involved the use of biochar to create a biochar-polysulfone (BC-PSf) flat-sheet multifunctional membrane to remove organic contaminants, and the other major experiment compared eco-friendly (gamma-valerolactone-GVL; Rhodiasolv® PolarClean-PC) and petroleum-derived solvents (i.e., N-methyl-pyrrolidone-NMP) in the fabrication of the biochar-polysulfone membranes. The resulting membranes were tested for their efficiency in removing both positively and negatively charged organic contaminants from the collected water at varying pH values. A comparative life cycle assessment (LCA) with accompanying uncertainty and sensitivity analyses was carried out to understand the global environmental impacts of incorporating biochar, NMP, GVL, and PC in the synthesis of PSf/NMP, BC-PSf/NMP, PSf/GVL, BC-PSf/GVL, PSf/PC, and BC-PSf/PC membranes at a set surface area of 1000 m2. The results showed that the addition of biochar to the membrane matrix increased the surface area of the membranes and improved both their adsorptive and mechanical properties. The membranes with biochar incorporated in their matrix showed a higher potential for contaminant removal than those without biochar. The environmental impacts normalized to the BC-PSf/GVL membrane showed that the addition of biochar increased global warming impacts, eutrophication, and respiratory impacts by over 100% in all the membrane configurations with biochar. The environmental impacts were highly sensitive to biochar addition (Spearman's coefficient > 0.8). The BC/PSf membrane with Rhodiasolv® PolarClean had the lowest associated global environmental impacts among all the membranes with biochar. Ultimately, this study highlighted potential tradeoffs between functional performance and global environmental impacts regarding choices for membrane fabrication.

Synthesis of a novel polymer and design of carboxylate-terminated hyperbranched PEI-incorporated PVDF membranes for efficient oil-in-water emulsion separation

Polyvinylidene fluoride (PVDF) membranes utilizing ultrafiltration (UF) and microfiltration (MF) configurations have widely been used in many separation processes, including oil/water emulsions. Recently, there have been tremendous research interests in designing PVDF membranes on their structural-property relations as well as high separation performances. Herein we report the synthesis of a novel carboxylate-terminated hyperbranched polyethylenimine (CHPEI) using a facile three-step one-pot strategy to enhance the characteristics of PVDF membranes for oil/water emulsion separation. The first step involved the production of one amide and one carboxylate functional group per maleic anhydride molecule on the outer surface of polyethylenimine (PEI). The second step involved producing two additional carboxylate groups via amine-based Michael addition of alkenes using aspartic acid dimethyl ester hydrochloride, followed by basic hydrolysis. CHPEI-n-PVDF membranes having various CHPEI contents are further fabricated by a phase-inversion process, obtaining as free-stable flat-sheet membranes. The synthesized polymer and membranes were thoroughly characterized by FTIR and 1H NMR, SEM, EDX, mapping, AFM, and contact angle analysis. The incorporation of CHPEI into PVDF positively enhanced the hydrophilicity, and the WCA was significantly reduced from 80.6° to 59.5°. The maximum permeation flux was obtained using CHPEI-3-PVDF membranes, which was 200 % more than that obtained using pristine PVDF. The CHPEI-2-PVDF membranes exhibited a rejection performance of >99 % for separating oil-in-water emulsions. The incorporation of CHPEI into PVDF significantly improved the antifouling characteristics of the membranes. After 5 h of operation in separating oil-in-water emulsions, the flux recoveries of CHPEI-2-PVDF and CHPEI-3-PVDF were found to be 92 % and 97 %, respectively. CHPEI has demonstrated a considerable positive influence in improving the PVDF membrane’s performance, making it an excellent candidate for oily wastewater treatment because of its high rejection performance and excellent flux recovery ratio.