Membrane Antifouling Properties Research Articles

Separation properties and fouling resistance of polyethersulfone membrane modified by fungal chitosan

This research explores the enhancement of polyethersulfone (PES) membranes through the incorporation of chitosan derived from the lignicolous fungus Ganoderma sp. Utilizing wet phase inversion and solution casting techniques, chitosan was successfully integrated into the PES matrix, as confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), which indicated a high deacetylation degree of 75.7%. The incorporation of chitosan significantly increased the membrane hydrophilicity, as evidenced by a reduction in the water contact angle and a substantial improvement in pure water permeability, from 17.9 L m-2 h-1 bar-1 to 27.3 L m-2 h-1 bar-1. The membrane anti-fouling properties were also notably enhanced, with the Flux Recovery Ratio (FRR) increasing from approximately 60–80%. Moreover, the chitosan-modified PES/CS membrane, particularly at a 5% chitosan concentration, demonstrated exceptional efficacy in pollutant removal, achieving over 90% elimination of total suspended solids, cadmium (Cd), and lead (Pb), alongside a 79% reduction in color during the treatment of textile wastewater.

The Application of TiO2/ZrO2-Modified Nanocomposite PES Membrane for Improved Permeability of Textile Dye in Water.

This study investigates the modification of polyethersulfone (PES) membranes with 1 wt% titanium dioxide (TiO2), zirconium dioxide (ZrO2) and a nanocomposite of TiO2/ZrO2. The aim was to efficiently remove Rhodamine B (RhB) from water using a threefold approach of adsorption, filtration and photodegradation. Among the modified membranes (TiO2, ZrO2 and TiO2/ZrO2), the TiO2/ZrO2-PES nanocomposite membrane showed a better performance in rejection of RhB than other membranes with the rejection efficiency of 96.5%. The TiO2/ZrO2-PES membrane was found to possess a thicker selective layer and reduced mean pore radius, which contributed to its improved rejection. The TiO2/ZrO2 nanocomposite membrane also showed high bulk porosity and a slightly lower contact angle of 69.88° compared to pristine PES with a value of 73°, indicating an improvement in hydrophilicity. Additionally, the TiO2/ZrO2-PES nanocomposite membrane demonstrated a relatively lower surface roughness (Sa) of 8.53 nm, which offers the membrane antifouling properties. The TiO2/ZrO2-PES membrane showed flux recovery ratio (FRR), total fouling (Rt), reversible fouling (Rr) and irreversible fouling (Rir) of 48.0%, 88.7%, 36,8% and 52.9%, respectively. For the photocatalytic degradation performance, the removal efficiency of RhB followed this order TiO2 > TiO2/ZrO2 > ZrO2 (87.6%, 85.7%, 67.8%). The tensile strength and elongation were found to be compromised with the addition of nanoparticles and nanocomposites. This indicates the necessity to further modify and optimise membrane fabrication to achieve improved mechanical strength of the membranes. At low pressure, the overall findings suggest that the TiO2/ZrO2 nanocomposite has the potential to offer significant improvements in membrane performance (water flux) compared to other modifications.

Synergistic effects of PVDF membrane surface functionalization with polydopamine and titanium dioxide for enhanced oil/water separation and photocatalytic behavior

This study investigates the surface modification of poly(vinylidene fluoride) (PVDF) membranes using polydopamine (PDA) and titanium dioxide (TiO2) for effective separation of oily compounds and self-cleaning photocatalytic behavior. The aim was to improve the antifouling properties of the membrane, which was modified by varied PDA and TiO2 concentrations and evaluated regarding the water permeance, total organic carbon (TOC) rejection, and photocatalytic degradation activity. The results demonstrated considerable improvements in the membrane's antifouling properties, achieving a water permeance of 781 kg h−1 bar−1 m−2, TOC rejection of 87%, and methylene blue photocatalytic degradation of 97%, using dopamine (DA) and TiO2 concentration of 0.92 g L−1 and 1.4% (w/w), respectively, and a solution agitation speed of 106 rpm. Additionally, flux recovery reached 86% after the photocatalytic self-cleaning process, indicating that TiO2 improved the membrane's antifouling properties. These findings highlight the potential of PDA and TiO2 as effective surface modifiers for enhancing oil/water separation, reducing fouling, and promoting self-cleaning effect in photocatalytic PVDF membranes. This study’s outcomes provide valuable insights for developing efficient and sustainable membrane-based separation processes for oily wastewater treatment applications.

Fabrication of PVDF membrane loaded with ultra-thin g-C3N4/FeOCl nanomaterials and study on catalytic and antifouling properties

Membrane separation technology has been widely used in the field of water treatment because of its excellent performance, but the inevitable membrane fouling increases the cost of use. Therefore, in this study, ultra-thin g-C3N4/FeOCl was loaded on polyvinylidene fluoride (PVDF) membrane by vacuum-assisted suction filtration for the first time to fabricate photo-Fenton catalytically modified membranes to improve their antifouling performance. The experimental results showed that ultra-thin g-C3N4/FeOCl adhered well to the membrane surface, increasing the modified membrane’s hydrophilicity. In addition, we found that the modified membrane achieved a maximum removal rate of 90% of the fouling. The flux recovery ratio (FRR) increased from 40% to 80% of the original membrane, indicating a significant increase in the membrane's antifouling properties. After 5 cycles, the membrane flux and pollutant removal rate were reduced by only 8%, indicating that the good stability and reusability of the modified membranes. It was experimentally verified that the active species that play a major role in the degradation of pollutants by the modified membranes are •OH and •O2–，the concentration of •OH can reach 5.5 × 10-6 mol/L in 45 min in the presence of hydrogen peroxide and light. In this study, a new modified membrane with good cycling performance is proposed, which provides new insights and ideas for the research of catalytic separation membrane technology.

Anti-fouling and self-cleaning ability of BiVO4/rGO and BiVO4/g-C3N4 visible light-driven photocatalysts modified ceramic membrane in high performance ultrafiltration of oily wastewater

Oily wastewater is one of the most harmful and resistant types of wastewater that cannot be treated with the usual and traditional methods. In this study, the visible light-driven photocatalysts BiVO4/rGO and BiVO4/g-C3N4 were made using the hydrothermal method. After that, a simple sol-gel method was used to make a photocatalytic ultrafiltration membrane with good self-cleaning and anti-fouling properties that can effectively separate oily wastewater. Photocatalyst properties were identified by using XRD, FTIR, DRS, N2 absorption-desorption, and zeta potential analysis. The performance of photocatalytic membranes was then investigated in oily wastewater treatment. Antifouling parameters, underwater oil contact angle, surface roughness, and electrochemical properties were measured to look into the membrane's antifouling properties. The use of a BiVO4/rGO composition with 20 wt% of rGO produced an underwater oil contact angle of 158°. Also, after 3 h of 3000 ppm oily wastewater filtration, the permeate flux was double that of the UF membrane without a photocatalytic coating, and the TOC removal efficiency was more than 99%. Measurement of antifouling parameters revealed that flux recovery was 89% compared to 51% for the UF membrane, and the total fouling ratio was reduced from 57% to 21%.

Photocatalytic membrane coated with α-Fe2O3/Fe3O4 for enhanced filtration performance and antifouling property in surface water treatment

A photocatalytic membrane coated with α-Fe2O3/Fe3O4 nanoparticles has been developed to address the challenges of membrane fouling and organic removal in the treatment of natural surface water. The photocatalytic and filtration properties of the membranes were investigated through a variety of methods. The successful preparation of iron oxide was confirmed by UV–vis diffuse reflectance spectra and X-ray diffractometry, with α-Fe2O3 identified as the primary photocatalytic agent. A commercial ultrafiltration (UF) membrane was employed as a comparison to evaluate the photocatalytic performance and filtration properties of the modified membrane. Results showed that the photocatalytic membrane achieved better removal rates for UV254 (22.0%) and specific fluorescent organic compounds, such as component 2 (19.38%) and component 3 (16.89%), compared to the control group. Furthermore, both irreversible and reversible fouling resistances of the prepared membranes were significantly lower than that of the control group, with reductions of 39.4% and 50.2%, respectively. The membrane coated with α-Fe2O3/Fe3O4 nanoparticles exhibited moderate removal of protein-like and terrestrially derived humic-like fluorescent organics while controlling membrane fouling. Although the α-Fe2O3/Fe3O4 nanoparticles-coated photocatalytic membrane demonstrated good anti-fouling properties, the removals of organic matters were not as effective as anticipated due to the shorter hydraulic retention time. This study provides valuable insights for enhancing pollutant degradation and anti-fouling properties of membranes through the utilization of solar photocatalytic α-Fe2O3/Fe3O4 surface-modified membranes in the treatment of natural surface water.

Dynamic behavior and optimal regulation of seawater desalination by membrane distillation considering the membrane fouling

Membrane distillation (MD) for seawater desalination is a promising technology to solve the shortage of freshwater because of its advantage of low energy consumption. However, membrane fouling is a common challenge that occurs during practical operation, resulting in decreased desalination performance. Since fouling phenomenon is a time-dependent process, a dynamic model of MD desalination considering membrane fouling is developed and experimentally validated in this study. The effects of key parameters on dynamic behavior considering the membrane fouling are investigated by this proposed model. The results indicate that membrane fouling has a significant effect on thin membranes as particles gradually accumulate on the membrane surface. Additionally, the rectangular shaped membrane exhibits better antifouling properties compared to the commonly used square shaped membrane. Inorganic pollution aggregation on the membrane surface is significantly enhanced by high temperature difference between the feed and permeate stream (ΔT), particularly in the initial stage. Increasing the feed stream rate (L) can alleviate organic pollutants and microbes. The model proposes hybrid optimal adjustment of ΔT and L to improve membrane antifouling properties. During the initial 30 h, the proposed approach leads to a 8.87% increase in permeation flux, but with the side effect of a 62.79% increase in energy consumption. The proposed dynamic model provides guidelines for optimizing MD desalination with better antifouling properties.

Fabrication and characterization of dual-layer hollow fiber membranes incorporating poly(citric acid) grafted GO with enhanced antifouling property for water treatment

ABSTRACT Membrane fouling which occurs during filtration process is a perennial issue and could lead to reduced separation efficiency. In this work, poly(citric acid) grafted graphene oxide (PGO) was respectively incorporated into matrix of single-layer hollow fiber (SLHF) and duallayer hollow fiber (DLHF) membranes, aiming to improve membrane antifouling properties during water treatment. Different loading of PGO ranging from 0 to 1 wt% was first introduced into the SLHF in order to identify the best PGO loading for the DLHF preparation with its outer layer modified by nanomaterials. The findings showed that at the optimized PGO loading of 0.7 wt%, the resultant SLHF membrane could achieve both higher water permeability and bovine serum albumin rejection compared to the neat SLHF membrane. This is owing to the improved surface hydrophilicity and increased structural porosity upon the incorporation of optimized PGO loading. When 0.7 wt% PGO was introduced only to the outer layer of DLHF, the cross-sectional matrix of the membrane was altered, forming microvoids and spongy-like structure (more porous). Nevertheless, the BSA rejection of the membrane was improved to 97.7% owing to the presence of inner selectivity layer that was produced from different dope solution (without PGO addition). The DLHF membrane also demonstrated significantly higher antifouling properties compared to the neat SLHF membrane. Its flux recovery rate is 85%, i.e., 37% better than that of neat membrane. By incorporating hydrophilic PGO into the membrane, the interaction of the hydrophobic foulants with the membrane surface is greatly reduced.

Fabrication and characterization of different braid‐reinforced PVC hollow fiber membranes to use in membrane bioreactor for wastewater treatment

AbstractIn this research, polyvinyl chloride (PVC) polymer was applied for the first time in the fabrication of braid‐reinforced hollow fiber membranes for ultrafiltration applications. Different concentrations of PVC solutions were cast on tubular braids and coagulated by the phase inversion method in a pure water bath to produce membranes with various porosities and pore sizes. The characterizations such as scanning electron microscopy, overall porosity, contact angle and mean pore size were done to understand membrane morphology. The antifouling property of membranes was explained using bovine serum albumin (BSA). The contact angles of membranes were increased from 64.9° ± 2.2 to 72.8° ± 2.1, while the overall porosity decreased from 43.8 ± 1.2% and 19.6 ± 3.3% for 11 wt% and 17 wt% PVC membranes, respectively. Permeate flow decreased due to decreased pore size of membranes as a result of increased PVC content. Besides, the flux recovery ratio, reversible and irreversible fouling studies showed that better antifouling characteristics observed with increasing of PVC content. A high removal efficiency of 87.2% for BSA was also demonstrated by the optimal membrane (15 wt% PVC), along with an increased flux recovery ratio of 96.6%. After investigating the rejection of COD in a membrane bioreactor setup, all membranes revealed that they were higher than 98%.

Amphiphilic Grafted Polymers Based on Citric Acid and Aniline Used to Enhance the Antifouling and Permeability Properties of PES Membranes

Water treatment technology based on ultrafiltration (UF) faces the problem of severe membrane fouling due to its inherent hydrophobicity. The use of amphiphilic polymers that possess both hydrophobic and hydrophilic chain segments can be advantageous for the hydrophilic modification of UF membranes due to their excellent combination in the membrane matrix. In the present study, we examined a novel amphiphilic CA-g-AN material, constructed by grafting citric acid (CA) to aniline (AN), as a modified material to improve the hydrophilicity of a PES membrane. This material was more compatible with the polymer membrane matrix than a pure hydrophilic modified material. The polyethersulfone (PES) membranes modified by amphiphilic CA-g-AN demonstrated a higher water flux (290.13 L·m-2·h-1), which was more than eight times higher than that of the pure PES membrane. Furthermore, the flux recovery ratio (FRR) of the modified membrane could reach 83.24% and the value of the water contact angle (WCA) was 76.43°, demonstrating the enhanced hydrophilicity and antifouling ability of the modified membranes. With this study, we aimed to develop a new amphiphilic polymer to improve the antifouling property and permeability of polymer-based UF membranes to remove organic pollutants from water.

Characterization of the Efficiency of Photo-Catalytic Ultrafiltation PES Membrane Modified with Tungsten Oxide in the Removal of Tinzaparin Sodium

One of the polymeric membranes' main limitations is their susceptibility to fouling, lowering the membrane's performance with time. Therefore, incorporating nanomaterials in polymer matrices has attracted great attention in wastewater treatment applications. It's a promising approach for enhancing membrane hydrophilicity and performance. Herein, ultrafiltration nanocomposite membranes were synthesized by applying the phase inversion method through immobilizing (0.1-0.4 wt.%) tungsten oxide (WO2.89) nanoparticles in a polyether sulfone (PES) matrix. Membrane's anti-fouling performance was evaluated against tinzaparin sodium. The data showed that the pure water flux improved with increasing nanoparticle loading, reaching its optimum value of 54.9 kg/m2 h at 0.4 wt.% WO2.89 nanoparticles compared to the neat membrane's 30.42 kg/m2 h. The results also demonstrated that the rejection efficiency and flux recovery ratio (FRR) against tinzaparin sodium was enhanced, by 44.89% and 12.69%, respectively, for the membranes modified with 0.4wt.% WO2.89 nanoparticles loading compared to the neat PES membrane. The data also showed that after exposing the nanocomposite membranes to UV light irradiation (λ=365 nm) and intensity (1200mW/cm2) for 1h, a further enhancement by 8.34% in FRR as compared to the membranes with the same percentage of nanoparticles loading without irradiation. It is concluded that the photocatalytic activity of WO2.89 nanoparticles in the decomposition of organic molecules on/close to the membrane surface was the impact that caused this improvement in membrane anti-fouling property

Zwitterionic liquid hydrogel sustained-release strategy for high-performance nanofiltration membrane

Controlling the diffusion of amine monomers plays a crucial role in fabricating well-defined architecture and high-performance nanofiltration (NF) membranes through interfacial polymerization (IP). Herein, a sustained-release strategy was proposed to regulate the interfacial polymerization through a zwitterionic liquid hydrogel transition layer. The hydrogel (Gel) was fabricated via in-situ one-step UV photo-initiated free-radical polymerization between 1-vinyl-3-ethylimidazolium chloride ([VEIm][Cl]) and 3-sulfopropyl methacrylate potassium salt (SMP) on the polyethersulfone (PES) substrate. The polyamide (PA) layer was then formed on the Gel layer by mitigating the diffusion of amine monomers. Low-field time-domain nuclear magnetic resonance (TD NMR) analysis demonstrated that the Gel layer significantly enhanced the water-absorbing capacity of the composite membrane. Positron annihilation lifetime spectroscopy (PALS) also confirmed the Gel-PA composite membrane possessed enlarged free volumes. The obtained Gel-PA composite membrane displayed a permeance of 13.22 L m−2 h−1 bar−1, a high Na2SO4 rejection of 98.23 %, a favorable NaCl/Na2SO4 selectivity of 49.75, outstanding long-term operational stability, and membrane antifouling properties. This sustained-release strategy provides a facile and feasible approach to controlling the IP process and obtaining high-performance nanofiltration membranes.

Biogenic silver nanoparticles-modified forward osmosis membranes with mitigated internal concentration polarization and enhanced antibacterial properties

Thin-film composite forward osmosis (TFC-FO) membranes show the potential to be applied in water treatment applications. However, the TFC-FO membrane performance was limited by internal concentration polarization (ICP) and membrane fouling. In this study, a well-functioning TFC-FO membrane was produced by embedding biogenic silver nanoparticles (BioAg) into the polysulfone (PSf) substrate of a FO membrane. Effects of BioAg on membrane structure, filtration performance, antifouling, and antibacterial properties of the as-prepared FO membranes were examined. Results indicated that BioAg-modified FO membranes achieved improved surface hydrophilicity, higher porosity, and mitigated ICP, resulting in 2.5–4.4 times higher water flux than the pristine FO membranes. The BioAg-modified FO membrane also showed significantly improved antifouling and antibacterial ability. Moreover, the release velocity of silver nanoparticles in FO membranes was significantly slowed down by the construction of the polyamide layer. After 30 days of immersion in an aqueous solution, 96.5% of silver was retained in the optimized BioAg-modified FO membrane. The study offers an effective approach to simultaneously mitigate ICP and enhance the antifouling property of TFC-FO membranes through substrate modification.

A comprehensive review on water remediation using UiO-66 MOFs and their derivatives.

Metal-organic frameworks (MOFs) are a versatile class of porous materials offering unprecedented scope for chemical and structural tunability. On account of their synthetic versatility, tunable and exceptional host-guest chemistry they are widely utilized in many prominent water remediation techniques. However, some of the MOFs present low structural stabilities specifically in aqueous and harsh chemical conditions which impedes their potential application in the field. Among the currently explored MOFs, UiO-66 exhibits structural robustness and has gained immense scientific popularity. Built with a zirconium-terephthalate framework, the strong Zr-O bond coordination contributes to its stability in aqueous, chemical, and thermal conditions. Moreover, other exceptional features such as high surface area and uniform pore size add to the grand arena of porous nanomaterials. As a result of its stable nature, UiO-66 offers relaxed admittance towards various functionalization, including synthetic and post-synthetic modifications. Consequently, the adsorptive properties of these highly stable frameworks have been modulated by the addition of various functionalities. Moreover, due to the presence of catalytically active sites, the use of UiO-66 has also been extended towards the degradation of pollutants. Furthermore, to solve the practical handling issues of the crystalline powdered forms, UiO-66 has been incorporated into various membrane supports. The incorporation of UiO-66 in various matrices has enhanced the rejection, permeate flux, and anti-fouling properties of membranes. The combination of such exceptional characteristics of UiO-66 MOF has expanded its scope in targeted purification techniques. Subsequently, this review highlights the role of UiO-66 in major water purification techniques such as adsorption, photocatalytic degradation, and membrane separation. This comprehensive review is expected to shed light on the existing developments and guide the inexhaustible futuristic scope of UiO-66 MOF.

Natural deep eutectic solvent modified nanofiltration membranes with superior antifouling properties for pharmaceutical wastewater treatment

Herein, the L-menthol/10-camphorsulfonic acid (L-M/CSA) natural deep eutectic solvent (NDES) was introduced as an innovative modifier for polyethersulfone (PES) nanofiltration (NF) membrane. Four membranes with different L-M/CSA NDES loadings (0, 0.2, 0.6, and 1 wt%) were prepared and characterized to evaluate the influence of L-M/CSA NDES on the properties of the membranes. The modified membrane with 0.2 wt% L-M/CSA NDES (M-0.2NDES) showed the pure water flux (PWF) of 111.5 L/m2h, which was about 7 times higher than that of the control membrane (M-0NDES). Meanwhile, the mean pore radius was increased from 0.7 nm for the M-0NDES membrane to 0.85 nm for the M-0.2NDES membrane, indicating the good pore forming capability of L-M/CSA NDES. Benefiting from L-M/CSA NDES blending, the modified membranes showed excellent removal efficiency to ceftriaxone (CTX) and amoxicillin (AMOX) solutions. Particularly, the M-0.2NDES membrane possessed 99.6 and 99.2% rejection to CTX and AMOX, respectively, with permeated flux up to about 111 L/m2h, which was far better than the data reported in the literature. M-0.2NDES membrane showed 89.1% chemical oxygen demand (COD), 100% turbidity, and 51.6% total dissolved solids (TDS) removal from the industrial pharmaceutical wastewater. Blending with L-M/CSA NDES was also confirmed to be crucial to ameliorate the membrane antifouling properties. The related results revealed that the flux recovery ratio (FRR) of the M-0.2NDES membrane for milk solution reached 90.2%. The facile fabrication method of L-M/CSA NDES from green materials, good pore forming capability, enhanced antifouling properties, together with the efficient pharmaceuticals removal indicated the good prospect of L-M/CSA NDES for membrane separation applications.

Dopamine-triggered one-step codeposition of zwitterionic surfactants for anti-fouling polyethersulfone ultrafiltration membrane modification

We report a facile ultrafiltration (UF) membrane modification strategy to impart anti-fouling properties to a polyethersulfone (PES) membrane via a simple codeposition of polydopamine (PDA) and the zwitterionic surfactant, 3-(N, N-Dimethylmyristylammonio) propane sulfonate (SB3-14). The effect of SB3-14 concentration (from 0.5, 1 to 2 mM) was also studied. The proposed modification notably increased membrane anti-fouling property without compromising membrane transport properties. As demonstrated by dynamic fouling experiments using BSA as a model foulant, the modified membranes presented significantly alleviated flux decline and decreased fouling resistance compared to the pristine membrane. Especially, the membrane modified with low SB3-14 concentration (i.e., 0.5 mM) possessed the optimal antifouling performance compared to those modified with higher concentrations, which may be attributed to reduced efficiency in PDA/SB3-14 aggregates functionalization on membrane surface in the presence of excessive zwitterions. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) results illustrate that Lewis acid-base (AB) played a dominant role during the fouling construction, and the presence of SB3-14 could tremendously decrease AB energy. This codeposition of PDA and non-polymer zwitterionic surfactant could be applied to prepare anti-fouling PES membranes with low reversible and irreversible fouling, which provides a new scope for post modification of UF membranes.

Dual Optimized Sulfonated Polyethersulfone and Functionalized Multiwall Carbon Tube Based Composites High Fouling Resistance Membrane for Protein Separation.

Commercial grade sulfonated-Polyethersulfone (S-PES) and functionalized multiwall carbon nanotube (f-MWCNT)/polyvinylpyrrolidone (PVP) nanocomposites (NCs) were used to enhance and optimize the antifouling, protein resistance and protein separation properties of the S-PES ultrafiltration membranes. The polarities of sulfonic groups of S-PES, carbonyl carbon of pyrrolidone, hydroxyl and carboxyl groups of f-MWCNT in the membrane composition helped to strongly bind each other through hydrogen bonding, as shown by Fourier-transform infrared spectroscopy (FTIR). These binding forces greatly reduced the leaching of NCs and developed long finger-like projection, as confirmed by elution ratio and cross-sectional studies of the membranes via field emission scanning electron microscope (FESEM). The contact angle was reduced up to 48% more than pristine PES. Atomic force microscopy (AFM) was employed to study the various parameters of surface roughness with 3d diagrams, while grain analysis of membrane surface provided a quantitative estimation about volume, area, perimeter, length, radius and diameter. The NCs/S-PES enhanced the flux rate with an impressive (80–84%) flux recovery ratio and (58–62%) reversible resistance (Rr) value in situ, with 60% and 54.4% lesser dynamic and static protein adsorption. The best performing membrane were reported to remove 31.8%, 66.3%, 83.6% and 99.9% for lysozyme-(14.6 kDa), trypsin-(20 kDa), pepsin-(34.6 kDa) and bovine serum albumin (BSA-66 kDa), respectively.

Surface modification of thin-film nanocomposite forward osmosis membrane with super-hydrophilic MIL-53 (Al) for doxycycline removal as an emerging contaminant and membrane antifouling property enhancement

• This work is the first study on the incorporation of MIL-53 (Al) into a TFN-FO membrane. • TFN 0.2 membrane showed the highest water flux without losing the selectivity. • Considerably boosted hydrophilicity (contact angle 20.6° vs. 80.4°) was attained. • Doxycycline rejection was obtained up to 99.73% in 2 h. • 96.67% flux recovery ratio was achieved in the filtration of BSA solution. As a contaminant of emerging concern, doxycycline is an antibiotic that has recently drawn rising attention due to its satisfactory outcomes for the treatment of COVID-19. In this study, a novel metal–organic framework thin-film nanocomposite forward osmosis (MOF-TFN FO) membrane was developed for doxycycline removal. The lack of applied hydraulic pressure in FO suggests an energy-efficient and low-cost process. A total of five composite membranes with different MIL-53 (Al) loadings (0, 0.1, 0.2, 0.3, and 0.5 wt%) were fabricated and characterized to assess the effect of MOF incorporation on the physicochemical properties of TFN membranes. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) analysis implied that incorporating MIL-53 (Al) in the polyamide selective layer affects the membrane morphology. Water contact angle measurements indicated significant augmentation in the hydrophilicity of modified membranes (20.6° for the optimally modified membrane vs. 80.4° for the unmodified membrane) owing to the increased hydroxyl group in the membrane selective layer. Due to the reduced structural parameter, the optimized membrane exhibited 94.31% enhanced water flux than the unmodified membrane without losing the selectivity. Also, the fouling experiments with organic foulant allude to the prominent antifouling property of this modified membrane with a 96.67% flux recovery ratio. More notably, the optimized membrane could maintain a high and stable rejection for doxycycline (>98.5%) for 10 h due to its size exclusion and adsorption properties. Our findings reveal the promising results of TFN FO membranes containing MOFs for antibiotics removal, which is not addressed sufficiently in the literature.

Asymmetrical ultrafiltration membranes based on polylactic acid for the removal of organic substances from wastewater

The continued use of non-biodegradable polymeric-based membranes for water purification has led to an unsustainable accumulation of waste at disposal, resulting in various environmental problems. In this study, eco-friendly asymmetric ultrafiltration (UF) membranes were fabricated from polylactic acid (PLA) with different polymer concentrations using the phase inversion method. The fabricated membranes were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, porosity, and pore size analysis. Permeate flux and organic matter (bovine serum albumin (BSA)) rejection were evaluated using synthetic wastewater. The anti-fouling properties of PLA membranes were investigated through static adsorption and dynamic filtration of BSA. Furthermore, the performance of the best performing PLA membrane was evaluated via chemical oxygen demand (COD) rejection as well as membrane fouling using raw municipal wastewater obtained from a local wastewater treatment plant (WWTP) in Abu Dhabi (UAE). The results indicated that increasing the PLA concentration to 20 wt% improved BSA removal from synthetic and raw wastewaters by up to 92 and 89%, respectively, in addition to improving the membrane anti-fouling property. The post-filtration and after cleaning FT-IR spectra revealed high antifouling property with no detection of BSA peaks, SEM images confirmed the reduction in membrane's pore size as PLA concentration increased, resulting in enhancing the antifouling properties of the membranes. In conclusion, this study demonstrated that PLA-UF membranes could be a viable eco-friendly alternative to traditional crude oil-derived membranes.

Improving antifouling property of alumina microfiltration membranes by using atomic layer deposition technique for produced water treatment

Drinking water supply sustainability is one of the biggest challenge of the century, necessitating efficient and economical technologies for water purification. ZnO atomic layer deposition (ALD) modified membranes were developed for treating produced water from wells in Oklahoma, as a model of produced water, having very high salt and oil content. ZnO ALD membranes increased hydrophilicity with an oil contact angle increasing from 165° for an α-alumina support to 171° for a ZnO ALD membrane (120 cycles), which induced a dramatic rise in the pure water flux from 148 to 192 L m−2 h−1. ZnO ALD on the membranes enhanced Total Organic Carbon (TOC) rejection from 96% to 99% and decreased Total Dissolved Solids (TDS) content from 53,205 ppm to 10 ppm. It was found that the average roughness (Sa) was 509 nm for the pristine α-alumina support and was reduced to 332 nm for the ZnO ALD membrane (120 cycles). Additionally, the anti-fouling property of membranes with flux recovery ratio increased from 93% to 99%. Overall, the ZnO ALD membrane showed great potential to purify produced water.