Preparation and Characterization of Polymeric-Hybrid PES/TiO2 Hollow Fiber Membranes for Potential Applications in Water Treatment

Polyethersulfone Polymer for Biomedical Applications and Biotechnology

Polymers stand out as promising materials extensively employed in biomedicine and biotechnology. Their versatile applications owe much to the field of tissue engineering, which seamlessly integrates materials engineering with medical science. In medicine, biomaterials serve as prototypes for organ development and as implants or scaffolds to facilitate body regeneration. With the growing demand for innovative solutions, synthetic and hybrid polymer materials, such as polyethersulfone, are gaining traction. This article offers a concise characterization of polyethersulfone followed by an exploration of its diverse applications in medical and biotechnological realms. It concludes by summarizing the significant roles of polyethersulfone in advancing both medicine and biotechnology, as outlined in the accompanying table.

Removal of Scale-Forming Ions and Oil Traces from Oil Field Produced Water Using Graphene Oxide/Polyethersulfone and TiO2 Nanoribbons/Polyethersulfone Nanofiltration Membranes

Treatment of produced water in oil fields has become a tough challenge for oil producers. Nanofiltration, a promising method for water treatment, has been proposed as a solution. The phase inversion technique was used for the synthesis of nanofiltration membranes of polyethersulfone embedded with graphene oxide nanoparticles and polyethersulfone embedded with titanium nanoribbons. As a realistic situation, water samples taken from the oil field were filtered using synthetic membranes at an operating pressure of 0.3 MPa. Physiochemical properties such as water flux, membrane morphology, flux recovery ratio, pore size and hydrophilicity were investigated. Additionally, filtration efficiency for removal of constituent ions, oil traces in water removal, and fouling tendency were evaluated. The constituent ions of produced water act as the scaling agent which threatens the blocking of the reservoir bores of the disposal wells. Adding graphene oxide (GO) and titanium nanoribbons (TNR) to polyethersulfone (PES) enhanced filtration efficiency, water flux, and anti-fouling properties while also boosting hydrophilicity and porosity. The PES-0.7GO membrane has the best filtering performance, followed by the PES-0.7TNR and pure-PES membranes, with chloride salt rejection rates of 81%, 78%, and 35%; oil rejection rates of 88%, 85%, and 71%; and water fluxes of 85, 82, and 42.5 kg/m² h, respectively. Because of its higher hydrophilicity and physicochemical qualities, the PES-0.7GO membrane outperformed the PES-0.7TNR membrane. Nanofiltration membranes embedded with nanomaterial described in this work revealed encouraging long-term performance for oil-in-water trace separation and scaling agent removal.

Novel PVDF-PVP Hollow Fiber Membrane Augmented with TiO2 Nanoparticles: Preparation, Characterization and Application for Copper Removal from Leachate

High proportion of copper has become a global challenge owing to its negative impact on the environment and public health complications. The present study focuses on the fabrication of a polyvinylidene fluoride (PVDF)-polyvinyl pyrrolidone (PVP) fiber membrane incorporated with varying loading (0, 0.5, 1.0, 1.5, and 2.0 wt%) of titanium dioxide (TiO₂) nanoparticles via phase inversion technique to achieve hydrophilicity along with high selectivity for copper removal. The developed fibers were characterized based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), permeability, porosity, zeta potential, and contact angle. The improved membrane (with 1.0 wt% TiO₂) concentration recorded the maximum flux (223 L/m²·h) and copper rejection (98.18%). Similarly, 1.0 wt% concentration of TiO₂ nanoparticles made the membrane matrix more hydrophilic with the least contact angle of 50.01°. The maximum copper adsorption capacity of 69.68 mg/g was attained at 1.0 wt% TiO₂ concentration. The experimental data of adsorption capacity were best fitted to the Freundlich isotherm model with R² value of 0.99573. The hybrid membrane developed in this study has considerably eliminated copper from leachate and the concentration of copper in the permeate was substantially reduced to 0.044 mg/L, which is below standard discharge threshold.

Utilization of Nano-TiO2 as an Influential Additive for Complementing Separation Performance of a Hybrid PVDF-PVP Hollow Fiber: Boron Removal from Leachate

The continuous increase in anthropogenic activities resulting in an increase in boron concentration in the environment is becoming a serious threat to public health and the ecosystem. In this regard, a hybrid polyvinylidene fluoride (PVDF)-polyvinyl pyrrolidone (PVP) hollow fiber was synthesized with hydrophilic nano-titanium oxide (TiO₂) at varied loadings of 0, 0.5, 1.0, 1.5, and 2.0 wt% using the phase inversion technique. The resultant membranes were characterized in terms of Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), contact angle, porosity, and zeta potential. The permeability flux was assessed using both pure water and leachate; also, rejection performance was evaluated based on boron removal from the leachate. The results revealed that the membrane with 1.0 wt% loading had the highest flux alongside an upturn in boron rejection percentage of 223 L/m²·h and 94.39%, respectively. In addition, the lowest contact angle of 50.01° was recorded with 1.0 wt% TiO₂ loading, and this implies that it is the most hydrophilic. Throughout the experiment cycles, the fiber with 1.0 wt% TiO₂ loading demonstrated a high flux recovery varying between 92.82% and 76.26% after 9 h filtration time. The physicochemical analysis of the permeate revealed that the boron concentration was significantly reduced to 0.43 mg/L, which is far lower than the discharge limit of 1.0 mg/L.

Application of Hybrid Membrane Processes Coupling Separation and Biological or Chemical Reaction in Advanced Wastewater Treatment

The rapid urbanization and water shortage impose an urgent need in improving sustainable water management without compromising the socioeconomic development all around the world. In this context, reclaimed wastewater has been recognized as a sustainable water management strategy since it represents an alternative water resource for non-potable or (indirect) potable use. The conventional wastewater remediation approaches for the removal of different emerging contaminants (pharmaceuticals, dyes, metal ions, etc.) are unable to remove/destroy them completely. Hybrid membrane processes (HMPs) are a powerful solution for removing emerging pollutants from wastewater. On this aspect, the present paper focused on HMPs obtained by the synergic coupling of biological and/or chemical reaction driven processes with membrane processes, giving a critical overview and particular emphasis on some case studies reported in the pertinent literature. By using these processes, a satisfactory quality of treated water can be achieved, permitting its sustainable reuse in the hydrologic cycle while minimizing environmental and economic impact.

Polyvinylidene Fluoride-Graphene Oxide Membranes for Dye Removal under Visible Light Irradiation

In this study, polyvinylidene fluoride (PVDF)-graphene oxide (GO) membranes were obtained by employing triethyl phosphate (TEP) as a solvent. GO nanosheets were prepared and characterized in terms of scanning and transmission electron microscopy (SEM and TEM, respectively), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), chemical analysis and inductively coupled plasma mass spectroscopy (ICP). Two different phase inversion techniques, Non-Solvent Induced Phase Separation (NIPS) and Vapour-Induced Phase Separation (VIPS)/NIPS, were applied to study the effect of fabrication procedure on the membrane structure and properties. Membranes were characterized by SEM, AFM, pore size, porosity, contact angle and mechanical tests, and finally tested for photocatalytic methylene blue (MB⁺) degradation under visible light irradiation. The effect of different pH values of dye aqueous solutions on the photocatalytic efficiency was investigated. Finally, the influence of NaCl salt on the MB+ photodegradation process was also evaluated.

Antifouling and antibacterial evaluation of ZnO/MWCNT dual nanofiller polyethersulfone mixed matrix membrane

The aim of this study is to evaluate the performance and antifouling properties of polyethersulfone (PES) membrane incorporated with dual nanofiller, zinc oxide (ZnO) and multi-walled carbon nanotube (MWCNT). The synergistic effect of the these nanofillers in PES membrane is studied by blending different ratio of ZnO/MWCNT nanofiller into the PES membrane. The fabricated membranes were characterized in terms of cross-section and surface morphology, surface hydrophilicity, pore size and porosity. The filtration performance of the membranes was tested using 50 mg/L humic acid (HA) solution as model solution. SEM image and gravimetric evaluation reported that the incorporation of both MWCNT and ZnO into the PES membrane improved porosity significantly up to 46.02%. Lower water contact angle of PES membrane incorporated with equal ratio of MWCNT and ZnO (PES 3) revealed that it has neat PES membrane properties and more hydrophilic membrane surface than single filler. PES 3 outperform other membranes with excellent HA permeate flux of 40.00 L/m².h and rejection of 88.51%. Due to hydrophilic membrane surface, PES 3 membrane demonstrate efficient antifouling properties with lower relative flux reduction (RFR) and higher flux recovery ratio (FRR). PES 3 also showed notable antibacterial properties with less bacterial attached to the membrane compared to neat PES membrane (PES 0).

High-Pressure Aging of Asymmetric Torlon® Hollow Fibers for Helium Separation from Natural Gas

Membrane separation for helium extraction from natural gas gained increased interest recently. Several vendors offer membrane elements for helium extraction, although data on their performance and operating experience are unpublished. The aim of this work was to obtain and study the separation performance of asymmetric hollow-fiber membrane element from commercial polyamide-imide Torlon®, in conditions close to the industrial process of helium extraction from natural gas. A membrane element with an active area of 0.177 m2, a helium permeance of 100 l(STP)/(m2·h·bar), and a selectivity α(He/CH4) = 340 was produced. This corresponds to a selective layer thickness of 82.3 nm, which was confirmed by SEM and resistance model calculations. The obtained membrane element was employed to decrease the concentration of helium in its binary mixture with methane from 0.4% to 0.05%. A relationship of separation characteristics from transmembrane pressure is also presented. At 70 bar and a stage cut of 2.7%, the feed flow rate was 0.16 m3(STP)/h, which yielded a helium permeate concentration of 14.7%. At 80 bar, a decrease in permeance to 60 l(STP)/(m2·h·bar) and in selectivity to 240 was observed. It was shown that the main reason for aging was the increased support resistance, due to a partial compaction of pores with a radius of less than 15 nm.

Novel Photocatalytic PVDF/Nano-TiO₂ Hollow Fibers for Environmental Remediation

Polyvinylidene difluoride (PVDF) mixed matrix membranes loaded with inorganic TiO₂ nanoparticles have received increasing attention in the last few years as self-cleaning membranes for possible application in wastewater treatment and seawater filtration. These novel membranes show increased hydrophilicity, stability and catalytic activity under UV-A irradiation. In this work, PVDF-TiO₂ hollow fibers were prepared by employing new strategies for enhancing the stability of the TiO₂ dispersion, reducing particle agglomeration and improving their distribution. The spinning conditions for producing ultrafiltration hollow fiber membranes from PVDF material and nano-TiO₂ were investigated. Finally, the optimized fibers have been characterized and tested for methylene blue (MB) degradation in water and salty seawater, revealing good permeability, long-term stability under UV-A irradiation, and photo-catalytic activity in both test solutions.

Numerical Comparison of Prediction Models for Aerosol Filtration Efficiency Applied on a Hollow-Fiber Membrane Pore Structure

Hollow-fiber membranes (HFMs) have been widely applied to many liquid treatment applications such as wastewater treatment, membrane contactors/bioreactors and membrane distillation. Despite the fact that HFMs are widely used for gas separation from gas mixtures, their use for mechanical filtration of aerosols is very scarce. In this work, we compared mathematical models developed for the prediction of air filtration efficiency by applying them on the structural parameters of polypropylene HFMs. These membranes are characteristic of pore diameters of about 90 nm and have high solidity, thus providing high potential for nanoparticle removal from air. A single fiber/collector and capillary pore approach was chosen to compare between models developed for fibrous filters and capillary-pore membranes (Nuclepore filters) based on three main mechanisms occurring in aerosol filtration (inertial impaction, interception and diffusion). The collection efficiency due to individual mechanisms differs significantly. The differences are caused by the parameters for which the individual models were developed, i.e., given values of governing dimensionless numbers (Reynolds, Stokes and Peclet number) and also given values of filter porosity and filter fiber diameter. Some models can be used to predict the efficiency of HFMs based on assumptions depending on the conditions and exact membrane parameters.