Polyethersulphone Membrane Research Articles

Performance of Graphene Oxide–Titanium Dioxide, Polyethersulphone Membranes for Industrial Wastewater Treatment

Performance of Graphene Oxide–Titanium Dioxide, Polyethersulphone Membranes for Industrial Wastewater Treatment

Optimization of Chitosan Synthesis Process Parameters to Enhance PES/Chitosan Membrane Performance for the Treatment of Acid Mine Drainage (AMD).

Acid mine drainage (AMD) is an environmental issue linked with mining activities, causing the release of toxic water from mining areas. Polyethersulphone (PES) membranes are explored for AMD treatment, but their limited hydrophilicity hinders their performance. Chitosan enhances hydrophilicity, addressing this issue. However, the effectiveness depends on chitosan's degree of deacetylation (DD), determined during the deacetylation process for chitosan production. This study optimized the chitin deacetylation temperature, alkaline (NaOH) concentration, and reaction time, yielding the highest chitosan degree of deacetylation (DD) for PES/chitosan membrane applications. Prior research has shown that high DD chitosan enhances membrane antifouling and hydrophilicity, increasing contaminant rejection and permeate flux. Evaluation of the best deacetylation conditions in terms of temperature (80, 100, 120 °C), NaOH concentration (20, 40, 60 wt.%), and time (2, 4, 6 h) was performed. The highest chitosan DD obtained was 87.11% at 80 °C, 40 wt. %NaOH at 4 h of chitin deacetylation. The PES/0.75 chitosan membrane (87.11%DD) showed an increase in surface hydrophilicity (63.62° contact angle) as compared to the pristine PES membrane (72.83° contact angle). This was an indicated improvement in membrane performance. Thus, presumably leading to high contaminant rejection and permeate flux in the AMD treatment context, postulate to literature.

Immobilization of novel synthesized phosphobetaine zwitterions on polyethersulphone (PES) hemodialysis membranes to induce hemocompatibility: Experimental, molecular docking, and ex-vivo inflammatory biomarker investigations

Hemodialysis therapy is a crucial life-saving treatment for severe kidney conditions, particularly in cases where organ transplantation is limited. However, the use of polymeric membranes in clinical dialyzers can trigger undesirable reactions in the blood, such as complement, leukocyte, and coagulation activations. These reactions can lead to hypertension, cardiovascular diseases, and even death, due to compatibility issues. This paper presents a study on the development and application of a novel phosphobetaine zwitterion, immobilized on polyethersulphone (PES) clinical hemodialysis membranes, to improve hemocompatibility. The study also introduces a new method for immobilizing a zwitterionic PVP-phosphobetaine polymer on a PES membrane, using a polydopamine (PDA) crosslinker. The synthesized membranes were characterized, and their performance in terms of blood-protein adsorption and subsequent interaction, specifically with fibrinogen, was investigated to evaluate hemocompatibility. The selection of the phosphobetaine polymer was driven by its capacity to form an electrically neutral zwitterionic hydration layer, which serves as a protective barrier, preventing fibrinogen adsorption. Without this zwitterionic polymer, blood proteins interact with the bare membrane, initiating biological processes that lead to inflammation when exposed to uremic blood. Molecular docking studies were conducted to understand the interactions between various ligands and specific serum protein components. The phosphate and carbonyl chemical groups on the pyrrolidinone zwitterionic moiety were found to form polar interactions with specific amino acids. Exvivo investigations involving incubated coated membranes and uremic blood samples from end-stage renal disease (ESRD) patients revealed that they caused weaker complement and coagulation activation compared to bare PES membranes. In addition, the inflammatory biomarkers have been studied to shed light on their potential impact on patients' quality of life. This study contributes to our understanding of the implications of blood-protein fouling and the hemocompatibility challenges faced by blood-contacting devices used in hemodialysis for ESRD patients, who are prone to membrane-related health complications.

Enhanced removal of iron (Fe) and manganese (Mn) ions from contaminated water using graphene oxide-decorated polyethersulphone membranes: Synthesis and characterization.

This study addresses the urgent issue of water pollution caused by iron (Fe) and manganese (Mn) ions. It introduces an innovative approach using graphene oxide (GO) and GO-decorated polyethersulphone (PES) membranes to efficiently remove these ions from contaminated water. The process involves integrating GO into PES membranes to enhance their adsorption capacity. Characterization techniques, including scanning electron microscopy, Fourier-transform infrared, and contact angle measurements, were used to assess structural and surface properties. The modified membranes demonstrated significantly improved adsorption compared to pristine PES. Notably, they achieved over 94% removal of Mn2+ and 93.6% of Fe2+ in the first filtration cycle for water with an initial concentration of 100 ppm. Continuous filtration for up to five cycles maintained removal rates above 60%. This research advances water purification materials, offering a promising solution for heavy metal ion removal. GO-decorated PES membranes may find application in large-scale water treatment, addressing environmental and public health concerns.

Development of a Standardised International Protocol for Evaluation of the Disinfection Efficacy of Healthcare Laundry Wash Processes

This research aims to develop a standardised protocol for monitoring the disinfection efficacy of healthcare laundry processes in view of numerous differential methodologies currently being employed within the healthcare laundry sector, including agitation and surface sampling for post-laundering decontamination assessment and swatch and bioindicator testing for in-wash-process efficacy. Enterococcus faecium as an indicator species within industrial wash systems is preferable due to its high thermal and disinfectant tolerance. Methods for measuring laundry disinfection were compared; commercially available E. faecium bioindicators and contaminated cotton swatches (loose, in cloth bags or within nylon membranes) were laundered industrially at ambient temperature and microbial recovery determined. E. faecium was lost from cotton during laundering but retained by the bioindicator membrane, which allows disinfection efficacy to be measured without loss of microorganisms from the test swatch. Commercially available bioindicators were only permeable to disinfectants and detergents at ≥60 °C. Subsequently, polyethersulphone membranes for enclosing contaminated swatches were developed for low-temperature laundering, with permeability to industrial laundry chemistries at below ≤60 °C. This study demonstrates that bioindicators are the recommended methodology for laundry disinfection validation. The use of a universal healthcare laundry disinfection methodology will lead to standardised microbiological testing across the industry and improvements in infection control.

Removal of endocrine disrupting chemicals from water through urethane functionalization of microfiltration membranes via electron beam irradiation

Polyethersulphone (PES) membranes modified with urethane functional groups were prepared through an interfacial reaction using electron beam irradiation. The removal of eight endocrine disrupting chemicals (EDCs) was studied using both pristine and functionalized PES membranes. The prepared membranes underwent characterization using several techniques, including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy, contact angle analysis, and measurements of pure water flux. Furthermore, dynamic adsorption experiments were conducted to evaluate the adsorption mechanism of the prepared membrane toward the eight EDCs. The urethane functionalized membranes were hydrophilic (52° contact angle) and maintained a high permeate flux (26000 L/h m2 bar) throughout the filtration process. Dynamic adsorption results demonstrated that the introduction of urethane functional groups on the membranes significantly enhanced the removal efficiency of 17β-estradiol, estriol, bisphenol A, estrone, ethinylestradiol, and equilin. The adsorption loading of 17β-estradiol on the functionalized PES membrane was 6.7 ± 0.7 mg/m2, exhibiting a 5-fold increase compared to the unmodified PES membrane. The membranes were successfully regenerated and reused for three adsorption cycles without experiencing any loss of adsorption capacity.

The Functionalization of PES/SAPO-34 Mixed Matrix Membrane with [emim][Tf2N] Ionic Liquid to Improve CO2/N2 Separation Properties

The use of ionic liquid [emim][Tf2N] as an additive in polyethersulphone (PES) and nano-sized silico-aluminophosphate-34 (SAPO-34) mixed matrix membrane was studied through the incorporation of different amounts of [emim][Tf2N] in the membrane composition, as presented in this work, varying from 10 to 40 wt%. Through gas permeation tests using CO2 and N2, the membrane composition containing 20 wt% [emim][Tf2N] led to the highest increase in CO2 permeability and CO2/N2 selectivity. The use of low concentrations of additive (10–20 wt%) promoted a state called antiplasticization; in this state, the permeability was even more regulated by the kinetic diameter of the species which, in this work, permitted achieving a higher CO2/N2 selectivity while increasing the CO2 permeability until an optimal condition. [emim][Tf2N] also promoted a better dispersion of SAPO-34 particles and an increase in the flexibility of the polymeric matrix when compared to a film with the same composition without [emim][Tf2N]. Moreover, the characterizations corroborated that the inclusion of [emim][Tf2N] increased the zeolite dispersion and improved the polymer/zeolite compatibility and membrane flexibility, characterized by a decrease in glass transition temperature, which helped in the fabrication process while presenting a similar thermal resistance and hydrophilicity as neat PES membrane, without affecting the membrane structure, as indicated by FTIR and a contact angle analysis.

Biorefining of liquid insect fractions by microfiltration to increase functionality

Insects are gaining attention as sustainable protein sources, necessitating the evaluation of gentle processing techniques for decontamination and fractionation of edible insects. Microfiltration was shown to be an effective alternative to thermal treatments for microbial decontamination of soluble insect protein. In this study, mealworm and cricket fractions extracted at pH 3 and 8, obtained through a microfiltration (0.2 μm polyethersulphone membrane) process, were assessed. This microfiltration process yielded a cream layer, a retentate containing protein aggregates, and a decontaminated permeate containing smaller-sized proteins (mostly <75 kDa). Microfiltration improved the permeates’ foamability to values higher than whey protein isolate (215–317% vs. 163%), while the retentates retained the gelling properties of up to ≈5000 Pa. Additionally, stable lipid droplets resembling plant-based oleosomes were recovered from the cream layer. This study shows that microfiltration is promising for simultaneous decontamination and fractionation, providing distinct fractions for diverse food applications.

Microfiltration for effective microbiological decontamination of edible insects – Protein hydrolysis, aggregation and pH are critical for protein recovery

During the processing of insects for food and feed applications, thermal treatments are often used for decontamination purposes. However, these treatments denature proteins comprising their functional properties. Milder methods for microbiological decontamination can be used, such as microfiltration. Therefore, in this study dead-end microfiltration (0.2 µm polyethersulphone membrane) was tested for decontamination of soluble fractions of lesser mealworms and house crickets obtained at pH values of 3 and 8. The results showed that dead-end microfiltration was successful in the removal of microorganisms (total viable count), removing the need for thermal treatments for the permeates. Protein recovery in the permeate was relatively low (14–43 %). Lesser mealworms at pH 3 gave the highest protein recovery in the permeate (43 %), as explained by the activity of endogenous proteases producing soluble peptides during microfiltration. Confocal imaging showed that the efficiency of microfiltration was reduced by membrane fouling caused by protein aggregation. The presence of lipids in the pre-filtrate does not hamper the permeate protein recovery. In conclusion, dead-end microfiltration with a 0.2 µm membrane is successful in achieving microbial stability. A pH of 3 is recommended during the extraction process to obtain a higher protein recovery.

Effect of fouling and cleaning upon the surface charge and porosity of polyethersulphone membranes during coffee brew decaffeination

Filtration processes could offer a viable alternative to use of solvents for the production of reduced caffeine coffee beverages (so called ‘half-decaf’) which have recently gained increased commercial attention. However fouling phenomena and membrane deterioration could significantly alter the process performance; hence fouling and cleaning mitigation strategies must be explored by monitoring key membrane properties such as porosity and surface charge. In this study, multiple cycle filtration of coffee brews for the selective reduction of caffeine has been performed. A commercially available synthetic tight ultrafiltration polyethersulphone (PES) membrane (GP95PP – Alfa Laval) and a bespoke loose nanofiltration mixed matrix PES membrane fabricated, were used for three consecutive fouling and cleaning filtration cycles. The impact and mechanisms of fouling and the cleaning protocol effectiveness were investigated using surface charge, porosity, membrane surface and membrane morphology characterization techniques. Streaming potential studies revealed negative surface zeta potential for the membranes in a pH range of ca. 3.5–8.0. The fouled membrane classes exhibited elevated negative charges, which were partially restored to the pristine levels when chemically cleaned, suggesting the presence of residual negatively charged foulants. Porosity studies revealed the presence of a porous cake layer with an increase of average pore size and pore volume, and a decrease of 10–20 % on the BET surface area of the fouled membranes. Presence of key compounds on the membrane surface and structure was confirmed via EDX and FT-IR spectroscopy. Surface roughness along with SEM microscopy verified the uniform deposition of the foulants with absence of bulky particles. The presence of a cake layer was confirmed via SEM cross-sectional images due to selective thick layer thickness increase of the fouled membranes. Flux differences between the membrane classes can be related to the thickness of the top layer. Flux decreases and flux recovery ratios were also reported over multiple cycles and linked with porosity and other surface properties.

Structural and performance variation of PES/PVDF membranes after exposure to the pretreated feed water of CECs

In this study, the removal efficiency of chemicals of emerging concerns (CECs) was evaluated under exposure to various doses of UV/H2O2-based oxidation processes in combination with membrane filtration for three cleaning cycles. Polyethersulphone (PES) and polyvinylidene fluoride (PVDF) materials based membranes were used for this study. The chemical cleaning of the membranes was performed by immersion of the membranes into 1 N HCl followed by adding 3000 mg.L−1 NaOCl for 1hr. Degradation and filtration performance was evaluated using Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) and total organic carbon (TOC) analysis. Membrane fouling analysis for assessing the comparative performance of PES and PVDF membranes was determined by specific fouling and fouling indices evaluation. Membrane characterization results show that the alkynes and carbonyl group formation are due to dehydrofluorination and oxidation of PVDF and PES membranes under the attack of foulants and cleaning chemicals, which resulted in a reduction of fluoride percentage and an increase in sulfur percentage in the PVDF and PES membranes. A decrease in the hydrophilicity of the membranes in underexposed conditions was observed and is consistent with an increase in dose. Degradation results of CECs follow with the highest removal efficiency of chlortetracycline (CTC) followed by atenolol (ATL), acetaminophen (ACT), and caffeine (CAF) degradation due to attack on the aromatic ring and the carbonyl group of CECs by OH exposure. Membrane exposed at 3 mg.L-1 dose of UV/H2O2-based CECs shows minimum alteration with higher filtration efficiency and lower fouling, particularly in PES membranes.

The influence of multiple fouling and cleaning cycles upon the performance of polyethersulphone membrane filters during coffee extract decaffeination

Filtration processes have been applied widely in food processing industry over the recent decades and could offer a viable alternative to the use of solvents in the decaffeination process, comprising low operational costs, high selectivities and mild processing conditions. This paper reports the development and evaluation of the fouling occurring in multiple filtration cycles during the selective reduction of caffeine from coffee brews comparing the performance of (i) a commercially available synthetic tight ultrafiltration (TUF) polyethersulphone (PES) membrane (GP95PP – Alfa Laval) and (ii) a self-made mixed matrix (MMMs) PES membranes (PSCD) fabricated in-house. The effectiveness and performance of the PES MMMs was benchmarked against the commercial 2 kDa PES membranes showing promising results. A cross-flow rig was operated at transmembrane pressures of 2–9 bar and cross-flow velocities (CFV) of 0.04–0.1 m/s at 25 °C. The flux decline and recovery along with changes in the key component rejection and resistances are reported for multiple fouling and cleaning cycles. PSCD exhibited a higher permeate flux of ca. 10.5 L m-2h-1compared to the GR95PP membranes, which exhibited a permeate flux of 6.1 L m-2h-1 over the 29 h filtration period selected, at 9 bar and a CFV of 0.04 m/s. The rejection ratios of the GR95PP and PSCD membranes were monitored for three consecutive filtration cycles, and showed values ca. 30% and 35% for caffeine,> 90% and ∼90% for both polyphenols & proteins, & ∼ 80% for melanoidins, respectively. An effective cleaning protocol was reported, comprised of 0.5 wt% NaOH at 50 °C, exhibiting cleaning efficiencies (CE)> 99%. FT-IR data indicated the presence of key compounds residuals after membrane cleaning. Modification to the membrane surface occurs due to fouling, altering the hydrophobicity. Differences in filtration performance and cleanability between the two classes of membranes are identified and linked to variations in surface and structure properties.

Novel microporous material-induced high selective membrane for acetic acid dehydration: experiments and molecular modelling

ABSTRACT Zeolite Y-doped sulphonated polyethersulphone (SPES) membrane is investigated for acetic acid dehydration by pervaporation. The membrane exhibits desired functional group, semicrystalline nature and high thermal stability with a uniform dispersion of filler. A 15 wt% zeolite Y loading was found to be the most appropriate with a low degree of swelling (30%) and mechanical stability (37 MPa). Molecular dynamic simulation estimates the water and acetic acid which reveals higher diffusivity of water molecules than acetic acid. The RDF analysis shows the high interaction of water molecules towards the zeolite Y and sulphonic group. The simulated diffusivity of acetic acid and water was validated with experimental diffusivity and it was to be in good agreement with an error below ±5%. The effect of different feed water concentrations (3–70 wt %), permeate pressures (1–11 mm Hg) and membrane thicknesses (30–180 μm) was investigated. The synthesised membrane exhibits high selectivity (1261) and optimum flux at a 97:3 ratio of acetic acid:water. The interaction of zeolite Y with SPES induces the hydrophilic nature in the membrane which preferentially improves the diffusion and permeation of water and restricts the acetic acid which causes the optimum water flux with high selectivity.

Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy.

Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation properties. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m2h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.

Synthesis and Characterization of a Polydioxanone-Coated Dipeptide-Functionalized Magnetic γ-Fe2O3 Nanoparticles-Modified PES Membrane and Its Biological Applications

This work is focused on the synthesis of leucyl-glycine-functionalized γ-Fe2O3 magnetic nanoparticles coated by polydioxanone (γ-Fe2O3-CA-Leu-Gly-PDX) as a polyethersulphone (PES) membrane for biotechnological applications. The physicochemical characteristics were investigated by FT-IR, SEM, XRD, a vibrating sample magnetometer (VSM), and ICP-OES. The present investigation also centered on the several biological activities of γ-Fe2O3-CA-Leu-Gly-PDX. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and metal chelating activity was studied for evaluation of its antioxidant activity potential. It exhibited 100% DPPH radical scavenging and 93.33% metal chelating activity. With applicability to antimicrobial photodynamic therapy, DNA cleavage and antimicrobial activity, the cell viability of γ-Fe2O3-CA-Leu-Gly-PDX was investigated in detail. The γ-Fe2O3-CA-Leu-Gly-PDX demonstrated the significant biofilm inhibition activity as being 81.54% and 86.34% for P. aeruginosa and S. aureus, respectively. Moreover, a novel polyethersulphone nanocomposite membrane incorporated with γ-Fe2O3-CA-Leu-Gly-PDX was prepared. The performance of the γ-Fe2O3-CA-Leu-Gly-PDX-blended polyethersulphone (PES) membrane was investigated by measuring the antifouling and E. coli rejection. The nanocomposite membranes demonstrated remarkable antifouling properties in contrast with the pristine PES when BSA (bovine serum albumin) and E. coli were filtrated. A complete rejection was obtained by the composite membrane. After an application of the membrane study, the modified polyethersulphone (PES) membrane blended with γ-Fe2O3-CA-Leu-Gly-PDX removed 100% of the E. coli.

Fouling of polyethersulphone ultrafiltration membranes during the decaffeination of ground coffee brews

The production of reduced caffeine coffee beverages (so called ‘half-decaf’) has recently gained increased commercial attention. Ultrafiltration (UF) can offer a viable alternative to the use of solvents in the decaffeination process, also operating at ambient temperatures, and a low operational cost. This paper reports the development and evaluation of the fouling occurring during the selective reduction of caffeine from coffee brews using a commercially available synthetic tight ultrafiltration (TUF) polyethersulphone (PES) membrane (GP95PP – Alfa Laval) with a 2 kDa molecular weight cut off (MWCO). Performance is reported in terms of fluxes, hydraulic resistances, and component rejection ratios. A cross-flow rig was operated at transmembrane pressures of 2–9 bar and cross-flow velocities of 0.04–0.1 m/s at temperatures in the range 25–50 oC. The process is viable: a retentate is produced with a much reduced caffeine concentration whilst still rich in higher molecular weight bioactives. Commercial PES membranes (GP95PP – Alfa Laval) had a permeate flux of 6.5 L m-2 h-1 and a fouling index (FI) of ca 60%. Rejection ratios were ca 30% for caffeine, ≥ 90% for both polyphenols & proteins, & ≥ 80% for melanoidins, over a 29 hr filtration period. Membrane surface modification due to fouling takes place, altering the hydrophobicity. An effective cleaning protocol is reported comprised of 0.5% w/v NaOH at 500 C. The flux decline and recovery are reported for multiple fouling and cleaning cycles.

A Combination of Aqueous Extraction and Ultrafiltration for the Purification of Phycocyanin from Arthrospira maxima.

The purification of phycocyanin (PC) from Spirulina generally involves a combination of different techniques. Here, we report the results on PC yields from a combined aqueous extraction-ultrafiltration (UF) process of a strain of Arthrospira maxima cultivated in a farm devoted to producing PC with food-grade purity. Samples optimized from different biomass/solvent ratios were purified by using a polyethersulphone (PES) membrane with a molecular weight cut-off (MWCO) of 20 kDa. The UF system was operated at 2.0 ± 0.1 bar and at 24 ± 2 °C up to a volume concentration factor (VCF) of 5. A diafiltration (DF) process was conducted after UF in order to increase the PC recovery in the retentate. Samples were collected during both UF and DF processes in order to evaluate membrane productivity and PC purity. The average permeate fluxes of about 14.4 L/m2h were measured in the selected operating conditions and more than 96% of PC was rejected by the UF membrane independently ofthe extraction yields and times. The concentration of PC in the final retentate was 1.17 mg/mL; this confirmed the observed rejection and the final VCF of the process (about 5-fold when compared to the concentration of PC in the crude extract). In addition, the combination of UF and diafiltration allowed the removal of about 91.7% of the DNA from the crude extract, thereby improving the purity of the phycocyanin in the retentate fraction.

Improvement in performance of g-C3N4 nanosheets blended PES ultrafiltration membranes including biological properties

This study aims to investigate the modification of polyethersulphone (PES) membrane with graphitic carbon nitride (g-C3N4) nanosheets for improving the antifouling and separation performance. The nanocomposite membranes were fabricated with blending of different g-C3N4 nanosheets (0.50, 1.00, and 2.00 wt%) into PES and they were synthesized by the phase inversion method. The fabricated g-C3N4 nanosheets and composite membranes were analyzed for their morphology. Scanning electron microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) mapping were used to detect the distribution of g-C3N4 nanosheets on membrane surface, whereas surface roughness of membrane was evaluated by atomic force microscopy (AFM). The composite membrane surface was found to be hydrophilic (67.54°), while the water flux of the composite membrane was found to be 254.8 L/m2/h for 2.00 wt% g-C3N4/PES membrane. The bovine serum albumin (BSA) separation tests indicated that the composite membrane supplied 98.5% BSA rejection ratio. Moreover, a significant improvement in antifouling characteristics were verified from BSA filtration experiments. g-C3N4 was also investigated for some of its biological properties such as antioxidant, antimicrobial, DNA cleavage, biofilm inhibition, and bacterial viability effect. g-C3N4 showed good free radical scavenging activity and moderate chelating activity at 500 mg/L. It was also determined that single-strand DNA cleavage activities occurred at all tested concentrations. g-C3N4 exhibited significant antibiofilm activity and inhibitory effects on E. coli vitality as 90.9%, 97.1%, and 98.9% at 250, 500, and 1000 mg/L, respectively. This study provides a simple and useful guideline to create a UF membrane resistant against organic fouling and expand its practical applications for wastewater treatment.

Fabrication and characterization of polyethersulfone membranes functionalized with zinc phthalocyanines embedding different substitute groups

In this study, a novel polyethersulphone (PES) composite membrane incorporated with two different zinc phthalocyanines (ZnPc), tetra-iodo and octa(2,6-diphenylphenoxy), was fabricated through the phase inversion approach. Three different concentrations of zinc phthalocyanines (0.5, 1.0, and 2.0 wt.%) were blended into the PES membrane. The morphology and performance of the fabricated composite membranes were systematically studied by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) mapping, atomic force microscopy (AFM), porosity, water contact angle, antifouling, and rejection measurements. Hydrophobicity of the pristine membrane decreased from 79.67° to 77.03° and from 79.67° to 67.57° after blending of 2.0 wt.% tetra-iodo ZnPc (TI-ZnPc) and octa(2,6-diphenylphenoxy) ZnPc (DP-ZnPc), respectively. Furthermore, the porosity and mean pore radius decreased due to the introducing of ZnPc. Porosity of the pristine membrane decreased from 60.60 % to 44.96 % and 42.21 % after blending of TI-ZnPc and DP-ZnPc, respectively. Mean pore size of the pristine membrane decreased from 22.70 nm to 9.11 nm and 17.93 nm after blending of TI-ZnPc and DP-ZnPc, respectively. BSA filtration mostly affected the flux of pristine membrane and caused it to decrease from 133.5 to 87.1 L/m2h (relative flux reduction (RFR) of 34.7 %). RFR decreased up to 19.2 % and 17.3 % for TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes. Pristine PES membrane rejected 45.8 % BSA. However, TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes supplied 91.0 % and 70.6 % BSA rejections, respectively. In comparison to pristine PES membrane, the total resistance (Rt) values of the composite membranes decreased. The pristine PES membrane showed the lowest flux recovery ratio (FRR, 71.89 %) against BSA, while all-composite membranes showed promising antifouling properties. FRR increased up to 97.44 % and 89.06 % for TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes, respectively. The pristine PES membrane showed the lowest FRR against activated sludge, while all composite membranes showed promising antifouling properties. Moreover, ZnPc-embedded PES composite membranes were irradiated with appropriate wavelengths of light in the presence of oxygen to generate reactive oxygen species to clean fouled membranes’ surface. The results showed that photo-cleaning was very effective to recover membrane flux.

Polyethersulfone membranes modified with CZTS nanoparticles for protein and dye separation: Improvement of antifouling and self-cleaning performance

In this study, a novel polyethersulphone (PES) nanocomposite membrane incorporated with copper zinc tin sulfide (Cu2ZnSnS4) nanoparticles (CZTS NPs) was prepared through the phase inversion method. First, the samples containing different copper and zinc ratios in CZTS stoichiometry were prepared and characterized. The effect of copper and zinc ratio changes were examined on the photocatalytic properties of both NPs and nanocomposite membranes. The photocatalytic effect was tested and BR18 dye was degraded at 88.0% efficiency when exposed to visible light for 180 min in the presence of CZTS1.0 NPs catalyst. The results also exhibited that CZTS NPs blended membrane showed good self-cleaning performance. Second, we investigated the antioxidant, DNA cleavage, and biofilm inhibition activities of CZTS NPs. The antimicrobial activities of CZTS NPs were tested against seven microbial strains. The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and chelating activities were found as 81.80 ± 1.75% and 72.19 ± 4.63%, respectively. CZTS NPs exhibited double-strand DNA cleavage activity at 500 mg/L. They showed significant biofilm inhibition as 92.15 ± 5.67% against Staphylococcus aureus. CZTS NPs displayed moderate antimicrobial effects against tested microorganisms. Third, CZTS NPs were blended in polyethersulphone (PES) membrane and the morphology as well as performance of the fabricated nanocomposite membranes were systematically investigated by SEM-EDX, porosity, water contact angle, antifouling, and rejection measurements. The water flux of resulting nanocomposite membranes was markedly enhanced due to the introducing of CZTS NPs. Meanwhile, the nanocomposite membranes demonstrated remarkable antifouling properties (flux recovery ratio ∼94%) in contrast with the bare PES (flux recovery ratio ∼51%) when BSA was filtrated. The high retention of BSA (100%) as well as high permeation flux (73.8 ± 9.8 L/m2/h) of the CZTS2.00 wt% membrane demonstrated that the constructed nanocomposite membrane possessed the characteristics of a promising membrane for purification of proteins.