Search Results (333)

Currently, the trade-off between oxygen permeation flux and structural stability in conventional perovskite oxides restricts the practical application of oxygen permeable membranes. In this study, a high-entropy design was applied to the B-site of BSCF matrix materials, resulting in the successful synthesis of a high-entropy perovskite, Ba_0.5Sr_0.5Co_0.71Fe_0.2Ta_0.03Ni_0.03Zr_0.03O_3−δ. The crystal structure, microstructure, and elemental composition of the material were systematically characterized and analyzed. Theoretical analysis and experimental characterization confirm that the material exhibits a stable single-phase high-entropy perovskite oxide structure. Under He as the sweep gas, the membrane achieved an oxygen permeation flux of 1.28 mL·cm⁻²·min⁻¹ and operated stably for over 100 h (1 mm thick, 900 °C). In a 20% CO₂/He atmosphere, the flux remained above 0.92 mL·cm⁻²·min⁻¹ for over 100 h, demonstrating good CO₂ tolerance. Notably, when the sweep gas is returned to the pure He atmosphere, the oxygen permeation flux fully recovers to 1.28 mL·cm⁻²·min⁻¹, with no evidence of leakage. These findings indicate that the proposed B-site doping strategy can break the trade-off between oxygen permeability and structural stability in conventional perovskite membranes. This advancement supports the industrialization of oxygen permeable membranes and offers valuable theoretical guidance for the design of high-performance perovskite materials. Full article

Electrospun nanofiber membranes based on cellulose acetate (CA) have gained increasing attention for wastewater treatment due to their high surface area, tuneable structure, and ease of functionalization. In this study, the performance of CA membranes was enhanced by incorporating aluminum oxide (Al₂O₃) nanoparticles (NPs) at varying concentrations (0–2 wt.%). The structural, morphological, and thermal properties of the resulting CA/Al₂O₃ nanocomposite membranes were investigated through FTIR, XRD, SEM, water contact angle (WCA), pore size measurements, and DSC analyses. FTIR and XRD confirmed strong interactions and the uniform dispersion of the Al₂O₃ NPs within the CA matrix. The incorporation of Al₂O₃ improved membrane hydrophilicity, reducing the WCA from 107° to 35°, and increased the average pore size from 0.62 µm to 0.86 µm. These modifications led to enhanced filtration performance, with the membrane containing 2 wt.% Al₂O₃ achieving a 99% removal efficiency for Indigo Carmine (IC) dye, a maximum adsorption capacity of 45.59 mg/g, and a high permeate flux of 175.47 L·m⁻² h⁻¹ bar⁻¹. Additionally, phytotoxicity tests using Lactuca sativa seeds showed a significant increase in germination index from 20% (untreated) to 88% (treated), confirming the safety of the permeate for potential reuse in agricultural irrigation. These results highlight the effectiveness of Al₂O₃-modified CA electrospun membranes for sustainable wastewater treatment and water reuse. Full article

Sugar production generates wastewater rich in dissolved solids and organic matter, and improper disposal poses severe environmental risks, exacerbates water scarcity, and creates regulatory challenges. Conventional treatment methods, such as evaporation and chemical precipitation, are energy-intensive and often ineffective at removing fine particulates and dissolved impurities. This study evaluates membrane-based separation as a sustainable alternative for water reclamation and sugar recovery from sugar industry effluents, focusing on replacing evaporation with membrane processes, ensuring high permeate quality, and mitigating membrane fouling. Cross-flow filtration experiments were conducted on a lab-scale membrane system at 70 °C to suppress microbial growth, comparing direct reverse osmosis (RO) of the raw effluent to an integrated ultrafiltration (UF)–RO process. Direct RO resulted in rapid membrane fouling. A tight UF (5 kDa) pre-treatment before RO significantly mitigated fouling and improved performance, enabling 28% water recovery and 79% sugar recovery, maintaining permeate conductivity below 0.5 mS/cm, sustaining stable flux, and reducing membrane blocking. Additionally, the UF and RO membranes were tested via SEM, EDS, and FTIR to elucidate the fouling mechanisms. Full article

In this work, hybrid membranes were fabricated by depositing polyvinyl chloride (PVC) fibers onto PET track-etched membranes (TeMs) using the electrospinning technique. The resulting structures exhibited enhanced hydrophobicity, with contact angles reaching 155°, making them suitable for applications in both water–oil mixture separation and membrane distillation processes involving low-level liquid radioactive waste (LLLRW), saline solutions, and natural water sources. The use of hybrids of TeMs and nanofiber membranes has significantly increased productivity compared to TeMs only, while maintaining a high degree of purification. Permeate obtained after MD of LLLRW and river water was analyzed by conductometry and the atomic emission spectroscopy (for Sr, Cs, Al, Mo, Co, Sb, Ca, Fe, Mg, K, and Na). The activity of radioisotopes (for ¹²⁴Sb, ⁶⁵Zn, ⁶⁰Co, ⁵⁷Co, ¹³⁷Cs, and ¹³⁴Cs) was evaluated by gamma-ray spectroscopy. In most cases, the degree of rejection was between 95 and 100% with a water flux of up to 17.3 kg/m²·h. These membranes were also tested in the separation of cetane–water emulsion with productivity up to 47.3 L/m²·min at vacuum pressure of 700 mbar and 15.2 L/m²·min at vacuum pressure of 900 mbar. Full article

With water availability being one of the world’s major challenges, this study aims to propose a Zero Liquid Discharge (ZLD) system for treating saline effluents from an urban wastewater treatment plant (UWWTP), thereby supplementing into the existing water cycle. The system, which employs membrane (nanofiltration and reverse osmosis) and thermal technologies (multi-effect distillation evaporator and vacuum crystallizer), has been installed and operated in Cyprus at Larnaca’s WWTP, for the desalination of the tertiary treated water, producing high-quality reclaimed water. The nanofiltration (NF) unit at the plant operated with an inflow concentration ranging from 2500 to 3000 ppm. The performance of the installed NF90-4040 membranes was evaluated based on permeability and flux. Among two NF operation series, the second—operating at 75–85% recovery and 2500 mg/L TDS—showed improved membrane performance, with stable permeability (7.32 × 10⁻¹⁰ to 7.77 × 10⁻¹⁰ m·s⁻¹·Pa⁻¹) and flux (6.34 × 10⁻⁴ to 6.67 × 10⁻⁴ m/s). The optimal NF operating rate was 75% recovery, which achieved high divalent ion rejection (more than 99.5%). The reverse osmosis (RO) unit operated in a two-pass configuration, achieving water recoveries of 90–94% in the first pass and 76–84% in the second. This setup resulted in high rejection rates of approximately 99.99% for all major ions (Cl⁻, Na⁺, Ca²⁺, and Mg²⁺), reducing the permeate total dissolved solids (TDS) to below 35 mg/L. The installed multi-effect distillation (MED) unit operated under vacuum and under various inflow and steady-state conditions, achieving over 60% water recovery and producing high-quality distillate water (TDS < 12 mg/L). The vacuum crystallizer (VC) further concentrated the MED concentrate stream (MEDC) and the NF concentrate stream (NFC) flows, resulting in distilled water and recovered salts. The MEDC process produced salts with a purity of up to 81% NaCl., while the NFC stream produced mixed salts containing approximately 46% calcium salts (mainly as sulfates and chlorides), 13% magnesium salts (mainly as sulfates and chlorides), and 38% sodium salts. Overall, the ZLD system consumed 12 kWh/m³, with thermal units accounting for around 86% of this usage. The RO unit proved to be the most energy-efficient component, contributing 71% of the total water recovery. Full article

Membrane fouling poses a significant challenge in the widespread adoption and cost-effective operation of membrane technology. Among different strategies to mitigate fouling, dynamic membrane (DM) technology has emerged as a promising one for effective control and mitigation of membrane fouling. Silicon carbide (SiC) membranes have attracted considerable attention as membrane materials due to their remarkable advantages, yet membrane fouling is still inevitable in challenging separation tasks, such as oil-in-water (O/W) emulsion separation, and thus effective mitigation of membrane fouling is essential to maximize their economic viability. This study investigates the use of pre-deposited oxide DMs to mitigate the fouling of SiC membranes during the separation of O/W emulsions. Among five screened oxides (Fe₂O₃, SiO₂, TiO₂, ZrO₂, Al₂O₃), SiO₂ emerged as the most effective DM material due to its favorable combination of particle size, negative surface charge, hydrophilicity, and underwater oleophobicity, leading to minimized oil droplet adhesion via electrostatic repulsion to DM surfaces and enhanced antifouling performance. Parameter optimization in dead-end mode revealed a DM deposition amount of 300 g/m², a transmembrane pressure (TMP) of 0.25 bar, and a backwashing pressure of 2 bar as ideal conditions, achieving stable oil rejection (~93%) and high pure water flux recovery ratios (FRR, >90%). Cross-flow filtration outperformed dead-end mode, maintaining normalized permeate fluxes of ~0.4–0.5 (cf. ~0.2 in dead-end) and slower FRR decline, attributed to reduced concentration polarization and enhanced DM stability under tangential flow. Optimal cross-flow conditions included a DM preparation time of 20 min, a TMP of 0.25 bar, and a flow velocity of 0.34 m/s. The results establish SiO₂-based DMs as a cost-effective strategy to enhance SiC membrane longevity and efficiency in O/W emulsion separation. Full article

Polymer membranes often face challenges of oil fouling and rapid water flux decline during the separation of oil-in-water emulsions, making them a focal point of ongoing research and development efforts. Coating PVDF membranes with a hydrogel layer equips the developed membranes with robust potential to mitigate oil fouling. However, developing a controllable thickness of a stable hydrogel layer to prevent the blocking of membrane pores remains a critical issue. In this work, atmospheric pressure low-temperature plasma was used to prepare the surface of a PVDF membrane to improve its wettability and adhesion properties for coating with a thin hydrophilic film of an AM-NaA copolymer hydrogel. The AM-NaA/PVDF membrane exhibited superhydrophilic and underwater superoleophobic properties, along with exceptional anti-crude oil-fouling characteristics and a self-cleaning function. The AM-NaA/PVDF membrane achieved high separation efficiency, exceeding 99% for various oil-in-water emulsions, with residual oil content in the permeate of less than 10 mg/L after a single-step separation. Additionally, it showed a high-water flux of 5874 L/m²·h for crude oil-in-water emulsions. The AM-NaA/PVDF membrane showed good stability and easy cleaning by water washing over multiple crude oil-in-water emulsion separation and regeneration cycles. Adding CaCl₂ destabilized emulsions by promoting oil droplet coalescence, further boosting flux. This strategy provides a practical pathway for the development of highly reusable and oil-fouling-resistant membranes for the efficient separation of emulsified oily water. Full article

Wood-based membranes have garnered increasing attention due to their structural advantages and durability in the efficient treatment of oily kitchen wastewater. However, conventional fabrication methods often rely on toxic chemicals or synthetic processes, generating secondary pollutants and suffering from fouling, which reduces performance and increases resource loss. In this study, an innovative bilayer membrane was developed from balsa wood by combining a hydrophilic longitudinal layer for water transport with a polydimethylsiloxane (PDMS)-impregnated carbonized transverse layer to enhance hydrophobicity, resulting in increased separation efficiency and a reduction in fouling by 98.38%. The results show a high permeation flux of 1176.86 Lm^–2 h^–1 and a separation efficiency of 98.60%, maintaining low fouling resistance (<3%) over 20 cycles. Mechanical tests revealed a tensile strength of 10.92 MPa and a fracture elongation of 10.42%, ensuring robust mechanical properties. Wettability measurements indicate a 144° contact angle and a 7° sliding angle with water on the carbonized side, and a 163.7° contact angle with oil underwater and a 5° sliding angle on the hydrophilic side, demonstrating excellent selective wettability. This study demonstrates the potential of carbonized wood-based membranes as a sustainable, effective alternative for large-scale wastewater treatment. Full article

Water scarcity has driven the use of wastewater treatment plant (WWTP) effluents as reclaimed water, highlighting the need to overcome challenges such as the presence of emerging contaminants, particularly microplastics (MPs), which WWTPs are unable to effectively remove. Membrane-based processes, such as microfiltration, have demonstrated high efficiency in the removal of suspended solids, and their application for MP removal is currently under investigation. This study assesses the influence of microfiltration membrane spacer size (1 mil and 80 mil) and geometry—diamond and corrugated—on MP recovery performance, using synthetic wastewaters with varying MPs concentrations. The results indicate the superior performance of large corrugated and small diamond-shaped membranes, as both exhibited the highest and comparable permeate flux, with no MP retention within the membrane element. All microfiltration membranes achieved an 80% recovery of the influent as safe reclaimed water and demonstrated an MP recovery efficiency exceeding 99%, with 100% rejection for fragments and up to 98% rejection for fibres. Full article

Background/Objectives: Raynaud’s phenomenon (RP) is characterized by an exaggerated vasoconstrictive response of small blood vessels in the fingers and toes to cold or stress. Oral therapy with tadalafil (TDL), a phosphodiesterase-5 inhibitor, is limited by systemic side effects and reduced patient compliance. This study aimed to develop and evaluate a TDL-loaded nanoemulgel for transdermal delivery as a non-invasive treatment alternative for cold-induced vasoconstriction. Methods: TDL-loaded nanoemulsions were prepared using the aqueous titration method with cinnamon oil as the oil phase and Cremophor RH40 and Transcutol as the surfactant–cosurfactant system. The optimized nanoemulsion was incorporated into a carbopol-based gel to form a nanoemulgel. The formulation was characterized for droplet size, morphology, thermodynamic stability, rheological properties, in vitro drug release, skin permeation, and pharmacokinetic behavior. Infrared thermography was employed to assess in vivo efficacy in cold-induced vasoconstriction models. Results: The optimized TDL nanoemulsion exhibited a spherical morphology, a nanoscale droplet size, and an enhanced transdermal flux. The resulting nanoemulgel displayed suitable physicochemical and rheological properties for topical application, a short lag time (0.7 h), and a high permeability coefficient (Kp = 3.59 × 10⁻² cm/h). Thermal imaging showed significant vasodilation comparable to standard 0.2% nitroglycerin ointment. Pharmacokinetic studies indicated improved transdermal absorption with a higher C_max (2.13 µg/mL), a prolonged half-life (t_1/2 = 16.12 h), and an increased AUC_0–24 compared to an oral nanosuspension (p < 0.001). Conclusions: The developed TDL nanoemulgel demonstrated effective transdermal delivery and significant potential as a patient-friendly therapeutic approach for Raynaud’s phenomenon, offering an alternative to conventional oral therapy. Full article

This study examines the effects of natural organic matter (NOM) and dissolved solids on fluoride (F⁻) retention in polyelectrolyte multilayer-based hollow-fiber nanofiltration membranes (dNF40). Lab-scale filtration experiments were conducted under varying operating conditions (initial salt concentration, NOM concentration, permeate flux, crossflow velocity, and recovery rate). dNF40 membranes exhibited F⁻ retention above 70% ± 1.2 in the absence of NOM and competing ions. However, when filtering synthetic model water (SMW) designed to simulate groundwater contaminated with high total dissolved solids (TDSs) and NOM, F⁻ retention decreased to approximately 60% ± 0.7, which was generally attributed to ion competition. Furthermore, despite limited declines in normalized permeability, the addition of NOM to SMW notably deceased F⁻ retention in the steady state to~20% due to fouling effects. The facilitated transport of the divalent cations Ca²⁺ and Mg²⁺ could be observed, as they accumulated in the organic fouling layer. While SO₄²⁻ retention remained relatively stable, the retention of monovalent anions (NO₃⁻, Cl⁻, and F⁻) decreased substantially due to drag effects. Na⁺ retention improved slightly to maintain electroneutrality. Feed salinity was shown to significantly affect separation efficiency, with PEC layers undergoing swelling and certain structural changes as the ionic strength increased. During batch filtration experiments at varying recovery rates, the retention of monovalent anions further decreased, with F⁻ retention reducing to just ~10% at a 90% recovery rate. This study provides valuable insights into better understanding and optimizing the performance of PEC-based NF membranes across diverse water treatment scenarios. Full article

Vacuum membrane distillation (VMD) is a promising process for water desalination. However, it suffers some obstacles, such as fouling and wetting, due to the inadequate hydrophobicity of the membrane and high vacuum pressure on the permeate side. Therefore, improving surface hydrophobicity and roughness is important. In this study, the effect of 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (PFTES) on the morphology and performance of CNM/PAC/PVDF membranes at various concentrations was investigated for the first time. Membrane characteristics such as FTIR, XRD, FE-SEM, EDX, contact angle, and hydrophobicity before and after modification were analyzed and tested using VMD for water desalination. The results showed that the membrane coated with 1 wt.% PFTES had a higher permeate flux and lower rejection than the membranes coated with the 2 wt.% PFTES. The 2 wt.% PFTES enhanced the contact angle to 117° and increased the salt rejection above 99.9%, with the permeate flux set to 23.2 L/m²·h and at a 35 g/L NaCl feed solution, 65 °C feed temperature, a 0.6 L/min feed flow rate, and 21 kPa (abs) vacuum pressure. This means that 2 wt.% PFTES-coated PVDF membranes exhibited slightly lower permeate flux with higher hydrophobicity, salt rejection, and stability over long-term operation. These outstanding results indicate the potential of the novel CNM/PAC/PVDF/PFTES membranes for saline water desalination. Moreover, this study presents useful guidance for the enhancement of membrane structures and physical properties in the field of saline water desalination using porous CNM/PAC/PVDF/PFTES membranes. Full article

The presence of dissolved sulfides in feed seawater causes severe elemental sulfur fouling in the reverse osmosis (RO) process. However, current pretreatment methods suffer from large footprint, high energy consumption, and limitations in effluent quality. In this study, adsorption and microfiltration are merged into a single process for the pretreatment of sulfide-containing seawater. Powdered activated carbon (PAC) was selected for its superior adsorption capacity (14.6-fold) and faster kinetics (3.9-fold) for sulfide removal compared to granular activated carbon. The high surface area and multiple pore structures of PAC facilitate surface and intraparticle diffusion, as well as anion–π conjugation likely occur between PAC and sulfide. Polypropylene microporous membranes, capable of tolerating high PAC dosages, were used in the hybrid process. Long-term pilot tests demonstrated that the effluent (turbidity < 1 NTU and SDI₁₅ ≈ 2.50) met the quality requirements for RO unit feedwater, achieving 100% sulfide removal efficiency over 101 h, with no risk of PAC leakage throughout the entire operation process. The formation of a loose, porous PAC cake layer alleviates membrane fouling and enhances the retention and adsorption of metal(loid)s and sulfide. Moreover, the low permeate flux of the polymeric membranes significantly mitigates filter cake formation. The hybrid system adapts to variations in feedwater quality, making it highly suitable for desalination plants with limited space and budget. These findings offer valuable insights and practical guidance for advancing seawater desalination pretreatment. Full article

Edge-capping modified MXene membranes with new channels created by lateral nanosheets are of great research significance. After introducing tripolyphosphate (STPP) to Ti edges of Ti₃C₂T_x nanosheets and fabricating the STPP-MXene membranes edge-capping method, this research investigated the performance optimization mechanism of STPP-modified MXene membranes in terms of salt permeability (NaCl, Na₂SO₄, MgCl₂, and MgSO₄) and transmembrane energy barriers (E_salt) through the concentration gradient permeation test. Experimental results demonstrated an approximately 1.86-fold enhancement in salt flux (J_s) compared to the MXene membranes. The solution–diffusion model was also introduced to evaluate the salt solubility (K_s) and diffusivity (D_s) during permeation. Furthermore, analysis of transmembrane energy barriers revealed that STPP modification induced significantly larger reductions in activation energy for magnesium salts (MgSO₄: 55.1%; MgCl₂: 47.4%) compared to sodium salts (NaCl: 30.5%; Na₂SO₄: 30.9%). This phenomenon indicated the weakened electrostatic interactions between high-valent Mg²⁺ and the modified lateral membrane Ti edges, whereas the limited charge density of Na⁺ resulted in relatively modest optimization. The results highlight the contribution of STPP capping on the edges of adjacent lateral nanosheets. Therefore, the modification increased the transportation rate of cations across the MXene membrane by more than twice, thus advancing the application of 2D MXene membranes in resource recovery. Full article

This study examines the treatment of industrial wastewater generated during vibro-abrasive steel and Zn-Al alloy parts machining in a Polish metal-processing plant. The machining process uses grinding fluids, which are sent for disposal after becoming saturated with contaminants, incurring high costs. A two-stage filtration process was investigated: an initial bag filtration (pore size 5 µm) followed by a low-pressure (4 bar) ultrafiltration with polyacrylonitrile membranes (30 kDa cut-off). The studies were carried out on a laboratory scale in a cross-flow system using a batch configuration. The initial filtrate flux was 0.116 mL min⁻¹ cm⁻² and 0.050 mL min⁻¹ cm⁻² for Zn-Al alloy and the steel wastewater, respectively. Key physicochemical parameters, including turbidity, COD, and TOC, were analysed for raw wastewater, feed, retentate, and permeate. Significant reductions in contaminant concentrations were achieved, with comparable total efficiencies for both the wastewaters tested. The reductions in turbidity, COD, TOC, anionic surfactants, total phosphorus and non-ionic surfactants ranged from 80% to almost 100%. A complete removal of total suspended solids was achieved. The novelty of this research lies in applying polyacrylonitrile flat-sheet membranes to treat wastewater from vibratory machining of ferrous and non-ferrous materials and recycle reclaimed water, which has not been systematically explored in previous studies. The study demonstrates the potential of low-pressure membrane filtration for wastewater recycling, offering insights into environmentally friendly and energy-efficient management of industrial wastewater. Full article