Toward Sustainable Tackling of Biofouling Implications and Improved Performance of TFC FO Membranes Modified by Ag-MOF Nanorods

In this work, nanorods with high antibacterial properties were synthesized with silver acetate as the metal source and 2-aminoterephthalic acid as the organic linker and were then embedded into thin-film composite (TFC) membranes to amend their performance as well as to alleviate biofouling. Silver metal-organic framework (Ag-MOF) nanorods with a length smaller than 40 nm were incorporated within the polyamide thin selective layer of the membranes during interfacial polymerization. The interaction of the synthesized nanorods with the polyamide was favored because of the presence of amine-containing functional groups on the nanorod's surface. The results of X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy characterizations proved the presence of Ag-MOF nanorods in the selective layer of thin-film nanocomposite (TFN) membranes. TFN membranes demonstrated improved water permeance, salt selectivity, and superior antibacterial properties. Specifically, the increased hydrophilicity and antibacterial potential of the TFN membranes led to a synergetic effect toward biofouling mitigation. The number of live bacteria attached to the surface of the neat TFC membrane decreased by more than 92% when a low amount of Ag-MOF nanorods (0.2 wt %) was applied. Following contact of the TFN membrane surface with Escherichia coli and Staphylococcus aureus, full inactivation, and degradation of bacteria cells were observed with microscopy, colony-forming unit tests, and disc inhibition zone analyses. This result translated to a negligible amount of the biofilm formed on the active layer. Indeed, the incorporation of Ag-MOF nanorods decreased the metal-ion release rate and therefore provided prolonged antibacterial performance

Melatonin protects testes against lithium-pilocarpine-induced temporal lobe epilepsy in rats: a time course study

Male dysfunction is common in patients with temporal lobe epilepsy (TLE). We evaluated whether melatonin, as a supplement, can play a positive role in reducing the epileptogenesis imposing abnormalities of spermatozoa and testes in epileptic rats. Status epilepticus was induced based on the TLE lithium-pilocarpine model. Two patterns of melatonin were administered to the epileptic animals along the mean durations of latent (14days) and chronic (60days) phases. Sperm parameters, different antioxidant enzyme levels, germ cell apoptosis, body and relative sex organ weights were evaluated in all groups 60days following SE induction. Chronic TLE caused a significant reduction in sperm parameters. In the testis, the reduced level of antioxidant enzymes was accompanied by a significant increase in malondialdehyde concentration. The presence of oxidant condition in the testes of epileptic animals caused expanded apoptosis in the germ cell layer. Moreover, the amount of weight gain in epileptic animals was more prominent. Melatonin administration was able to improve sperm motility by increasing the total antioxidant level. There was also a significant reduction in the spermatogenic cell line apoptosis and the extra weight gain of melatonin-treated animals. Melatonin supplementation might be considered as an acceptable cotreatment in epileptic patients

Recent advances in functionalized polymer membranes for biofouling control and mitigation in forward osmosis

Forward osmosis (FO) is an osmotically driven process widely studied for water desalination, wastewater treatment, and water reuse, as well as dilution and concentration of aqueous streams. However, its application is still hampered by the lack of ideal draw solutes, high-performance membranes, and fouling/biofouling. Biofouling is particularly challenging when FO is applied for seawater desalination and wastewater treatment. Over the last decade, many attempts have been made to exploit advances in materials science to obtain membranes with anti-biofouling properties to prevent or to reduce the detrimental effects of this phenomenon. In this review, we address the various approaches of membrane surface functionalization for biofouling control and mitigation. Recent developments in surface modification of thin-film composite and asymmetric membranes using surface coating, surface functionalization, and incorporation of tailored materials for biofouling control in FO are critically discussed. The future perspectives of anti-biofouling materials and FO membranes are reviewed to shed light on the future research directions for developing the true potential surface modification approach for the FO process

Functionalized polyamide membranes yield suppression of biofilm and planktonic bacteria while retaining flux and selectivity

Biofouling is a major challenge for desalination, water treatment, and water reuse applications using polymer-based membranes. Two classes of novel silver-based metal azolate frameworks (MAF) are proposed to decorate polyamide (PA) forward osmosis membranes and to improve numerous aspects of fouling and transport. Membranes functionalized with two concentrations of each MAF are compared with a pristine control material, with results that clearly highlight their tunability and bio-inhibitory effects. We report for the first time PA membranes yielding near complete suppression of a robust biofilm-forming bacterium (Pseudomonas aeruginosa) and inactivation of planktonic bacteria, while maintaining high selectivity. These features improve the long-term water flux performance of the membranes, tested during 24 h of accelerated biofouling and organic fouling conditions, and showing lower than 10% and 20% decline in water flux. These enhancements were achieved with only 0.03–0.06% mass of additives and little generation of hazardous waste products, indicating that low-cost and environmentally benign functionalization can prevent biofouling growth while maintaining selectivity and transport for high-performance desalination, water treatment and reuse

Loose nanofiltration membranes functionalized with in situ-synthesized metal organic framework for water treatment

In this study, modified loose nanofiltration membranes were prepared by in-situ decoration with Zeolitic Imidazolate Framework-7 (ZIF-7) on the surface of porous polyethersulfone substrates functionalized with co-deposited sulfobetaine methacrylate (SBMA) zwitterion (ZW) and polydopamine (PDA). With the aid of ZW/PDA active layer co-deposition under mild conditions, ZIF-7 metal organic framework (MOF) nanocrystals were successfully formed and anchored onto the membrane surface via both non-covalent and covalent bonds to simultaneously achieve the desired selectivity and productivity of the loose nanofiltration membranes. The characterization results confirmed the successful deposition of the ZW/PDA active layer and the consequent decoration with ZIF-7 nanocrystals. The average water contact angle decreased notably from 81.4 to 51.43 degrees upon the formation of ZIF-7. This membrane showed high rejection (~99.9%) of methyl blue and Congo red dyes and high water flux with dye solutions (around 40 L m-2h-1) at a very low applied pressure of 1.5 bar. Moreover, the filtration experiments revealed that functionalized membranes exhibited a significant reduction in fouling and biofouling propensity. Notably, the MOF-SBMA/PDA membrane displayed favorable antifouling behavior associated with a significant ability to recover flux upon simple physical cleaning. The combination of these two properties is possibly the most promising feature of the membrane proposed in this study

Facile Cu-BTC surface modification of thin chitosan film coated polyethersulfone membranes with improved antifouling properties for sustainable removal of manganese

Loose nanofiltration membranes, which have a loose selective layer and desired surface charge, provide highwaterflux and significant retention of low molecular weight molecules. In this study, a thinfilm of copper (II)-benzene-1,3,5-tricarboxylate (Cu-BTC) clusters was anchored on the surface of a chitosan (CS)-coated poly-ethersulfone (PES) membrane to improve the surface properties as well as performance (permeability, heavymetal removal efficiency, and antifouling activity) of the membrane. Characterization techniques, such as FE-SEM, EDX, XPS and AFM, zeta potential and water contact-angle measurements, verified that Cu-BTC wassuccessfully anchored on the CS layer. The Cu-BTC/CS membrane exhibited higher surface hydrophilicity androughness compared to the pristine one. It also demonstrated a waterflux of 44 L m−2h−1and a manganeseremoval efficiency of 86%, while the membrane coated only with CS had an average waterflux of 39 L m−2h−1and a manganese removal efficiency of 78%. Compatibility and interfacial interactions between the Cu-BTCclusters and the CS layer were investigated using molecular dynamics (MD). MD simulations indicated that theCu-BTC clusters increased the affinity of the membrane for water molecules. The anchored Cu-BTC clusters alsoimproved the antibacterial activity of the membrane; the Cu-BTC/CS membrane inactivated 83% ofEscherichiacolibacteria, while the pristine CS membrane 47% of the bacteria. The Cu-BTC/CS membrane also demonstratedinteresting anti-fouling properties against both organic and biological foulants

Improved antifouling and antibacterial properties of forward osmosis membranes through surface modification with zwitterions and silver-based metal organic frameworks

This study investigates the effect of surface functionalization of a thin-film composite forward osmosis membrane with zwitterions and silver-based metal organic frameworks (Ag-MOFs) to improve the antifouling, anti-biofouling, and antimicrobial activity of the membrane. Two types of zwitterions, namely, 3-bromopropionic acid and 1,3-propane sultone, are chemically bonded, with and without incorporation of Ag-MOFs, over the surface of a polyamide membrane. Spectroscopy measurements indicate successful grafting of the modifying agents on the membrane surface. Contact angle measurements demonstrate a notable improvement in surface wettability upon functionalization. The performance of the membranes is evaluated in terms of water and salt fluxes in forward osmosis filtrations. The transport data show demonstrably increased water flux of around 300% compared to pristine membranes, with similar or slightly reduced salt reverse flux. The antifouling and anti-biofouling properties of the modified membranes are evaluated using sodium alginate and E. coli, respectively. These experiments reveal that functionalized membranes exhibit significant antifouling and anti-biofouling behavior, with high resilience against flux decline

Tailoring the Biocidal Activity of Novel Silver-Based Metal Azolate Frameworks

The synthesis of nanostructures with tunable antibacterial properties using green solvents at room temperature is of environmental interest, and antibacterial nanomaterials are used in the fabrication of biofouling-resistant membranes for water purification and wastewater treatment. In this study, we investigate the effect of organic ligands on the antibacterial and structural properties of silver-based metal-azolate frameworks (Ag-MAFs). Three new Ag-MAFs were synthesized with silver, as the metal center, and imidazole-based linkers having different chemistries via a facile and environmentally friendly method conducted at room temperature. The coordination of silver ions with the linkers resulted in the formation of Ag-imidazole, Ag-2 methylimidazole, and Ag-benzimidazole complexes with octahedral, hexagonal nanosheet, and nanoribbon morphologies, respectively. The Ag-MAFs exhibited excellent antibacterial activity (up to 95% die-off of bacteria at a short exposure time of 3 h) in colloidal forms against both Gram-negative Escherichia coli (E. coli) and Gram-positive Bacillus subtilis (B. subtilis) because of synergetic effects of silver and the imidazole-based linkers. Ag-2 methylimidazole showed the highest antibacterial activity, owing to its high silver concentration and special nanocrystal structure that provides better contact with bacteria. This work indicates that the antibacterial activity of Ag-MAF nanostructures can be tailored by changing the organic linker, allowing for creating nanostructures with desired biocidal properties