Surface modification of polyethersulfone ultrafiltration membranes by corona air plasma for separation of oil/water emulsions

Role of plasma process gas on permeate flux augmentation of cellulose nitrate membrane for mud water treatment

A comparative study between Nitrogen (N2) and Argon (Ar) plasma is carried out to investigate its effect on surface morphology, hydrophilicity, permeate flux and ageing of cellulose nitrate polymeric membranes in the present work. Langmuir probe and Optical Emission Spectroscopy are used to characterize the plasma. The SEM analysis reveals the noticeable macro-void creations and pore enlargement for both N2 and Ar plasma. The AFM analysis shows a higher surface roughness for Ar plasma treatment as compared to N2 plasma treatment. XPS analysis confirms the changes in the polymer matrix along with the incorporation of various functional groups on the membrane surface as a result of the plasma treatment. A better hydrophilic nature with prolonged plasma treatment is observed for Ar plasma as compared to N2 plasma treatment. The present results show a higher permeate flux with a high rejection rate for Ar plasma treatment in comparison to N2 plasma, which might be due to the pore size and pore area enlargement of the membrane. The hydrophobic recovery for both the plasma-treated membranes is found significant for the initial ageing period of 7 days and found almost stable in nature after 7 days. A diffusion-based theoretical model is developed to study the hydrophobic recovery of plasma-treated membranes. A strong alignment between experimental and theoretical results is observed in the present work. The Cake Filtration model, derived from the Hermia model, is identified as the most suitable model for describing the fouling mechanisms for the present work.

Antifouling and Water Flux Enhancement in Polyethersulfone Ultrafiltration Membranes by Incorporating Water-Soluble Cationic Polymer of Poly [2-(Dimethyl amino) ethyl Methacrylate]

Novel ultrafiltration (UF) polymer membranes were prepared to enhance the antifouling features and filtration performance. Several ultrafiltration polymer membranes were prepared by incorporating different concentrations of water-soluble cationic poly [2-(dimethyl amino) ethyl methacrylate] (PDMAEMA) into a homogenous casting solution of polyethersulfone (PES). After adding PDMAEMA, the effects on morphology, hydrophilicity, thermal stability, mechanical strength, antifouling characteristics, and filtration performance of these altered blended membranes were investigated. It was observed that increasing the quantity of PDMAEMA in PES membranes in turn enhanced surface energy, hydrophilicity, and porosity of the membranes. These new modified PES membranes, after the addition of PDMAEMA, showed better filtration performance by having increased water flux and a higher flux recovery ratio (FRR%) when compared with neat PES membranes. For the PES/PDMAEMA membrane, pure water flux with 3.0 wt.% PDMAEMA and 0.2 MPa pressure was observed as (330.39 L·m^-2·h^-1), which is much higher than that of the neat PES membrane with the value of (163.158 L·m^-2·h^-1) under the same conditions. Furthermore, the inclusion of PDMAEMA enhanced the antifouling capabilities of PES membranes. The total fouling ratio (TFR) of the fabricated PES/PDMAEMA membranes with 3.0 wt.% PDMAEMA at 0.2 MPa applied pressure was 36 percent, compared to 64.9 percent for PES membranes.

Atmospheric Pressure Plasma-Treated Polyurethane Foam as Reusable Absorbent for Removal of Oils and Organic Solvents from Water

This paper reports the optimization of a two-step atmospheric pressure plasma process to modify the surface properties of a polyurethane (PU) foam and, specifically, to prepare a superhydrophobic/superoleophilic absorbent for the removal of oils and nonpolar organic solvents from water. In particular, in the first step, an oxygen-containing dielectric barrier discharge (DBD) is used to induce the etching/nanotexturing of the foam surfaces; in the second step, an ethylene-containing DBD enables uniform overcoating with a low-surface-energy hydrocarbon polymer film. The combination of surface nanostructuring and low surface energy ultimately leads to simultaneous superhydrophobic and superoleophilic wetting properties. X-ray photoelectron spectroscopy, scanning electron microscopy and water contact angle measurements are used for the characterization of the samples. The plasma-treated PU foam selectively absorbs various kinds of hydrocarbon-based liquids (i.e., hydrocarbon solvents, mineral oils, motor oil, diesel and gasoline) up to 23 times its own weight, while it completely repels water. These absorption performances are maintained even after 50 absorption/desorption cycles and after immersion in hot water as well as acidic, basic and salt aqueous solutions. The plasma-treated foam can remove mineral oil while floating on the surface of mineral oil/water mixtures with a separation efficiency greater than 99%, which remains unaltered after 20 separation cycles.

Simple Fabrication of Polyvinylidene Fluoride/Graphene Composite Membrane with Good Lipophilicity for Oil Treatment

Graphene (GE) is an emerging type of two-dimensional functional nanoparticle with a tunable passageway for oil molecules. Herein, polyvinylidene fluoride (PVDF)/GE composite membranes with controllable pore structure were fabricated with a simple non-solvent-induced phase separation method. The change of crystallinity and crystal structure (α, β, γ, etc.) generated is due to the addition of GE, which benefits the design of a suitable pore structure for oil channels. Meanwhile, the hydrophobicity and thermal stability of the composite membrane were obviously enhanced. With 3 wt % GE, the contact angle was 124.6°, which was increased greatly compared to that of the GE-0 sample. Moreover, the rate of the phase transition process was affected by the concentration of casting solution, temperature, and composition of the coagulation bath. For example, the composite membrane showed better oil-water separation properties when the coagulation bath was dioctyl phthalate. In particular, the oil flux and separation efficiencies were up to 2484.08 L/m²·h and 99.24%, respectively. Consequently, PVDF/GE composite membranes with excellent lipophilicity may have good prospects for oily wastewater treatment.

Investigation and Optimization of Vacuum Plasma Treatment of PA66 Fabric for Reduced Fire Retardant Consumption

Flame retardant (FR) textiles were obtained by surface treatments of polyamide 66 fabrics with microwave (MW) plasma technology in order to reduce the amount of FR involved in the fabric finishing process. More specifically, MW vacuum plasma was employed for polymer surface activation by using a helium/oxygen (He/O₂) gas mixture, evaluating the effect of different treatment parameters on the affinity toward thiourea impregnation. Surface fabric modification was investigated both in terms of uniformity and increased thiourea absorption by infrared spectroscopy, wicking properties, and gravimetric characterization to define an operative window for plasma treatment conditions. According to the results obtained, the dry add-on content of thiourea improved up to 38%, thanks to the increase of the fabric surface activation. The effectiveness of plasma treatment resulted in an absolute increase up to 2% in limiting oxygen index (LOI) performance with respect to untreated fabric. As a consequence, a drastic reduction of 50% in thiourea concentration was required to achieve a similar fire retardant performance for plasma-treated fabric. On the basis of these preliminary results, a design of experiment (DoE) methodology was applied to the selected parameters to build a suitable response surface, experimentally validated, and to identify optimized treatment conditions. At the end, a final LOI index up to 43% has been reached.

Functionalized Nanomembranes and Plasma Technologies for Produced Water Treatment: A Review

The treatment of produced water, associated with oil & gas production, is envisioned to gain more significant attention in the coming years due to increasing energy demand and growing interests to promote sustainable developments. This review presents innovative practical solutions for oil/water separation, desalination, and purification of polluted water sources using a combination of porous membranes and plasma treatment technologies. Both these technologies can be used to treat produced water separately, but their combination results in a significant synergistic impact. The membranes functionalized by plasma show a remarkable increase in their efficiency characterized by enhanced oil rejection capability and reusability, while plasma treatment of water combined with membranes and/or adsorbents could be used to soften water and achieve high purity.

Recent Progress in Microfiltration/Ultrafiltration Membranes for Separation of Oil and Water Emulsions

Oily wastewater has become one of the leading causes of environmental pollution. A massive quantity of oily wastewater is released from industries, oil spills, and routine activities, endangering the ecosystem's sustainability. Due to the enormous negative impact, researchers put strenuous efforts into developing a sustainable solution to treat oily wastewater. Microfiltration/ultrafiltration membranes are considered an efficient solution to treat oily wastewater due to their low cost, small footprint, facile operation, and high separation efficiencies. However, membranes severely fouled during the separation process due to oil's adsorption and cake layer formation, which shortens the membranes' life. This review has critically discussed the microfiltration/ultrafiltration membrane synthesizing methods and their emulsion's separation performance. In the end, key challenges and their possible solutions are highlighted to provide future direction to synthesize next-generation membranes.

Superwetting Bi2MoO6/Cu3(PO4)2 Nanosheet-Coated Copper Mesh with Superior Anti-Oil-Fouling and Photo-Fenton-like Catalytic Properties for Effective Oil-in-Water Emulsion Separation

Superwetting materials with excellent anti-oil-fouling performance for the treatment of oily wastewater are urgently demanded in practice. In this work, aiming at effectively separating diverse oil-in-water emulsions, a multifunctional Bi₂MoO₆/Cu₃(PO₄)₂ nanosheet-coated copper mesh was successfully fabricated by the combination of chemical oxidation and ultrasonic irradiation deposition methods. The resultant copper mesh exhibited superior superhydrophilicity/underwater superoleophobicity and, more importantly, preferable anti-oil-fouling property benefitting from the stable and firm hydration layer. A series of oil/water separation experiments for the highly emulsified surfactant-free and surfactant-stabilized oil-in-water emulsions were conducted, with the respective permeation fluxes of up to 3000 and 700 L·m^-2·h^-1 and the corresponding separation efficiencies of 99.5 and 98.6% solely driven by gravity. Meanwhile, considering the photo-Fenton-like catalytic activity of Bi₂MoO₆, the as-fabricated copper mesh exhibited excellent degradation ability toward organic pollutants under visible light irradiation. More importantly, stability tests were performed to evaluate the ability to cope with the harsh environments for practical applications. With the outstanding performances of high separation efficiency, desirable photo-Fenton-like catalytic capacity, and strong stability, the Bi₂MoO₆/Cu₃(PO₄)₂ nanosheet-coated copper mesh holds promising potential for purifying emulsified wastewater.

Improvement of tangential microfiltration of gelatin solution using a permanent magnetic field

Membrane technology is an interesting alternative to conventional gelatin clarification methods, resulting in the elimination of refining chemical agents. In this work, the application of a permanent magnetic field as a pre-treatment of the gelatin solutions was proposed as a strategy to improve the microfiltration (MF) performance. Filtration tests were performed using a 1.5% swine gelatin solution at 40 °C through cellulose acetate membranes in a tangential flow module. Prior to the filtrations, the feed solutions were pretreated by the circulation of the solution through magnetic fields with different flux densities, 0.7 T and 1.34 T, for 2 h. The magnetic induction of the solution significantly increased the permeate flux and the recovery of hydraulic permeance by 63% and 122%, respectively, showing the application of the magnetic field in the solution of gelatin is an attractive alternative to improve the performance of the process.

Development of Polymeric Membranes for Oil/Water Separation

In this work, the treatment of oily wastewater was investigated using developed cellulose acetate (CA) membranes blended with Nylon 66. Membrane characterization and permeation results in terms of oil rejection and flux were compared with a commercial CA membrane. The solution casting method was used to fabricate membranes composed of CA and Nylon 66. Scanning Electron Microscopy (SEM) analysis was done to examine the surface morphology of the membrane as well as the influence of solvent on the overall structure of the developed membranes. Mechanical and thermal properties of developed blended membranes and a commercial membrane were examined by thermogravimetric analysis (TGA) and universal (tensile) testing machine (UTM). Membrane characterizations revealed that the thermal and mechanical properties of the fabricated blended membranes better than those of the commercial membrane. Membrane fluxes and rejection of oil as a function of Nylon 66 compositions and transmembrane pressure were measured. Experimental results revealed that the synthetic membrane (composed of 2% Nylon 66 and Dimethyl Sulfoxide (DMSO) as a solvent) gave a permeate flux of 33 L/m²h and an oil rejection of around 90%, whereas the commercial membrane showed a permeate flux of 22 L/m²h and an oil rejection of 70%.

Detergent and Water Recovery from Laundry Wastewater Using Tilted Panel Membrane Filtration System

Increasing global concern on clean water scarcity and environmental sustainability drive invention in water reclamation technology. Laundry wastewater reclamation via membrane technology faces the challenge of membrane fouling. This paper assesses a tilting-the-filtration-panel filtration system for the treatment of real laundry wastewater filtration aimed for water and detergent reuse. Results showed that the panel tilting significantly improved fouling control and enhanced permeability due to enhanced contact of air bubbles with the membrane surface, which induced continuous detachment of foulant from the membrane surface. The combination of aeration rate and tilting angle resulted in up to 83% permeability enhancement from 109 to 221.4 ± 10.8 (L/m²·h·bar). The system also offers 32% detergent recovery. Overall findings suggest that the system offers an attractive approach for both fouling management and detergent recovery and can potentially be applied under a simple setup in which filtration can be driven by gravity/hydrostatic pressure.

Biopolymer extracted from Moringa oleifera Lam. in conjunction with graphene oxide to modify membrane surfaces

A novel modification through pressurized filtration technique of commercial polyethersulfone membranes was proposed using a biopolymer extracted from Moringa oleifera Lam. (MO) along with graphene oxide (GO), in order to decrease fouling and improve the membrane selectivity for the removal of methylene blue dye. The effect of these agents over the morphology and performance of the membranes were studied through the evaluation of permeability, dye removal and fouling parameters. The characterization of the membrane indicates a significant decrease in pore size, as confirmed by the filtration experiments. Also, according to FTIR and SEM analysis the modification was effectively accomplished. All modified membranes presented low fouling rates (<10.55%) and high dye removal rates (from 2.85% to 96.73%). Furthermore, it is the first time that MO has been used as a natural polymer to improve and confer new characteristics on membranes, creating new possibilities for further study of this promising environment-friendly biopolymer in membrane separation processes.

Immediate modified prostodontic rehab for tumor of the maxilla: case report

Introduction. Timely maxillofacial orthopedic care is aimed at leveling the message of the oral cavity with the nasal cavity and its paranasal sinuses, orbit, helps to improve swallowing, speech, breathing and salivation. The objective of this work is to demonstrate the possibility of application of a polymethyl methacrylate prosthesis with a superhydrophobic modified surface directly on the operating table, as well as to demonstrate the possibility of using in the shortest postoperative period. Materials and methods. Patient Z., 28 years old, clinical diagnosis: chondrosarcoma of the upper jaw on the right, Т2N0M0, stage 2. A resection of the upper jaw was proposed with simultaneous reconstructive treatment and the application of a dental resection forming denture of the upper jaw. To form a hydrophobic surface, the prosthesis was modified with a high-frequency plasma of sulfur hexafluorides. The study of the quantitative and qualitative composition of microflora on the surface of the resection forming prosthesis was carried out after transportation of the prosthesis from the dental laboratory, after processing of high-frequency plasma of sulfur hexafluoride and before applying the resection forming prosthesis, 3, 7 days after the prosthesis was applied. Results. After modification of sulfur hexafluoride in the medium, the contact angle of contact with distilled water increased, the critical surface tension decreased compared to the initial one, and the hydrophobic properties were increased. Conditionally pathogenic microflora in a diagnostically significant amount was cultivated from the surface of the resection forming prosthesis obtained from the dental laboratory. Bacterial seeding after modification in the plasma of sulfur hexafluoride showed the absence of microflora strains; a slight increase in opportunistic microflora was obtained on days 3 and 7 after application of the prosthesis. In the immediate postoperative period (3 days), the patient complained of pain and discomfort associated with the surgical stage. Conclusions. The presented clinical case indicate that the superhydrophobic surface modified by sulfur hexafluoride contributes to a more stable healing of the postoperative defect.

A Review on Current Development of Membranes for Oil Removal from Wastewaters

The current situation with the problems associated with the removal of oil from wastewaters by membranes is being explored. Many types of membranes have been investigated—organic polymers, inorganic or ceramic species and hybrids of the two. Polymeric membranes can be designed to facilitate the passage of oil, but the more successful approach is with hydrophilic types that encourage the passage of water. Ceramic membranes have an advantage here as they are less often irreversibly fouled and give a higher recovery of oil, with a lower flux decline. Furthermore, they can be cleaned up by a simple heating procedure. More attention should be given to understanding the mechanism of fouling so that operating conditions can be optimised to further reduce fouling and further decrease the flux decline, as well as assisting in the design of antifouling membranes. Another obstacle to ceramic membrane use is the high cost of manufacture. Cheaper starting materials such as clays have been surveyed.

Surface modification of a PES membrane by corona air plasma-assisted grafting of HB-PEG for separation of oil-in-water emulsions

The main goal of this study is to modify a polyethersulfone (PES) membrane by grafting with hyperbranched polyethylene glycol (HB-PEG) using corona air plasma to intensify the anti-fouling properties of the prepared membrane. The separation efficiency and fouling tendency of the modified membranes were evaluated for the treatment of a synthetic oily wastewater. A mechanism was proposed for the HB-PEG grafting on the surface of the corona treated PES membranes and all steps of the grafting were described in detail. The effects of corona treatment operating conditions on the morphology, surface properties, separation performance and anti-fouling efficiency of the modified PES membranes were investigated. Also, the HB-PEG grafted PES membranes were characterized by FTIR, AFM and contact angle analysis. Finally, the HB-PEG grafting on the surface of the PES membranes altered the surface hydrophilicity and led to the improvement of the anti-fouling property and oil–water permeation flux of all modified membranes without any remarkable changes in oil rejection.

The main goal of this study is to modify a polyethersulfone (PES) membrane by grafting with hyperbranched polyethylene glycol (HB-PEG) using corona air plasma to intensify the anti-fouling properties of the prepared membrane.

Fabrication of PES/PVP Water Filtration Membranes Using Cyrene®, a Safer Bio-Based Polar Aprotic Solvent

A more sustainable dialysis and water filtration membrane has been developed, by using the new, safer, bio-based solvent Cyrene® in place of N-methyl pyrrolidinone (NMP). The effects of solvent choice, solvent evaporation time, the temperature of casting gel, and coagulation bath together with the additive concentration on porosity and pore size distribution were studied. The results, combined with infrared spectra, SEM images, porosity results, water contact angle (WCA), and water permeation, confirm that Cyrene® is better media to produce polyethersulfone (PES) membranes. New methods, Mercury Intrusion Porosimetry (MIP) and NMR-based pore structure model, were applied to estimate the porosity and pore size distribution of the new membranes produced for the first time with Cyrene® and PVP as additive. Hansen Solubility Parameters in Practice (HSPiP) was used to predict polymer-solvent interactions. The use of Cyrene® resulted in reduced polyvinylpyrrolidone (PVP) loading than required when using NMP and gave materials with larger pores and overall porosity. Two different conditions of casting gel were applied in this study: a hot (70°C) and cold gel (17°C) were cast to obtain membranes with different morphologies and water filtration behaviours.

Bio-inspired robust superhydrophobic-superoleophilic polyphenylene sulfide membrane for efficient oil/water separation under highly acidic or alkaline conditions

The separation of water-in-oil emulsions in harsh environment (strong acid/alkali) is a challenging subject. In this study, we prepared a superhydrophobic-superoleophilic polyphenylene sulfide (PPS) membrane by the mixture of hydrophobic SiO₂ nanoparticles, diphenyl ketone (DPK), benzoin (BZ) and PPS via thermally induced phase separation (TIPS) technology. This superhydrophobic membrane displayed a lotus leaf-like micro-nano structure, and it could be used for oil/water separation in strong acidic or alkaline environment. The hydrophobic SiO₂ nanoparticles played a key role in the membrane structure evolution and its performance. When SiO₂ content was 4 wt%, the pure water contact angle of the prepared superhydrophobic-superoleophilic membrane reached 156.9° and the oil contact angle achieved 0°. The fluxes of water-in-oil emulsions (kerosene, toluene and chloroform) reached 1926, 3150 and 3416 L/(m²·h), respectively. However, the fluxes of their surfactant-stabilized water-in-oil emulsions declined to 531, 685 and 724 L/(m²·h), respectively, due to the great stability of surfactant-stabilized emulsions. Most importantly, all the water rejection rates exceeded 99.9% when the PPS membranes modified with 4 wt% hydrophobic SiO₂ nanoparticles. In addition, the PPS-SiO₂ hybrid membranes exhibited excellent self-cleaning antifouling performance, cycling performance and superior acid/alkali resistance.

DMSO EVOL™ as novel non-toxic solvent for polyethersulfone membrane preparation

The possibility of replacing traditional toxic solvents normally employed during the preparation of polymeric membranes with greener alternatives represents a great challenge for safeguarding the human health and protecting the environment. In this work, an improved and pleasant-smelling version of dimethylsulfoxide (DMSO), i.e., DMSO EVOL™, was used as "greener solvent" for the preparation of polyethersulfone (PES) microfiltration (MF) membranes using a combination of non-solvent and vapor-induced (NIPS and VIPS, respectively) phase separation technique for the first time. The effect of two different additives polyvinylpyrrolidone (PVP) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronic®) together with polyethylene glycol (PEG) on membrane properties and performances has been also evaluated. The membranes were characterized in terms of morphology, mechanical resistance, pore size, and water permeability. The obtained results show that DMSO EVOL™ is able to replace 1-methyl-2-pyrrolidone (NMP), which is a more toxic solvent normally used for the preparation of PES membranes. Furthermore, it was possible to tune the produced membranes in the range of MF (0.1-0.6 μm).

Membranes with Functionalized Nanopores for Aromaticity-Based Separation of Small Molecules

Membranes that can separate molecules of similar size based on chemical features could transform chemical manufacturing. We demonstrate membranes with functional, 1-3 nm pores prepared using a simple and scalable approach: coating a porous support with random copolymer micelles in alcohol, followed by precipitation in water and functionalization of pore surfaces. This approach was used to prepare membranes that can separate two hormones of similar size and charge, differentiated by aromaticity, mediated through π-π interactions between the aromatic solute and pore walls functionalized with phenol groups. The aromatic molecule permeates more slowly in single-solute experiments. In competitive diffusion experiments, however, it permeates 7.1 times faster than its nonaromatic analogue. This approach can be used to manufacture membranes for complex separations based on various intermolecular interactions.