Oleic acid-functionalized TiO2 nanoparticles for fabrication of PES-based nanofiltration membranes

Grafting Buffer Layer Strategy onto the Nanofiltration Membrane to Enhance Antifouling Properties toward Highly Efficient Desalination

Water treatment and seawater desalination are two areas in which nanofiltration (NF) membranes have gained significant attention. The permeability and contamination resistance of NF membranes are crucial for their application in ion separation. Herein, a zwitterion monomeric N-sulfobutylpiperazine (PIPBS) was designed and synthesized through an in situ ring-opening reaction between 1,4-butylsulfonic acid lactone and piperazine. A new hydrophilic structure is formed when PIPBS is chemically grafted with piperazine-trimesoyl chloride (PIP-TMC) onto the surface of the NF membrane, increasing the water flux and improving antifouling properties. NF performance was systematically investigated with respect to both the PIPBS concentration and reaction time. In addition to higher salt retention for NaSO4 (97.3%) and MgSO4 (94.1%), the optimized PTPM also displayed better ion selectivity for Na2SO4/NaCl. Sulfonic acid groups make membranes more hydrophilic, reducing contamination, deposition, and membrane pore plugging by direct contact with contaminants. In comparison to untreated NF membranes, due to the hydration of PIPBS on the membrane surface, the water flux increased by 2.3 times with a 13.6% grafting ratio for PTPM-1. Furthermore, PTPM had superior protein fouling resistance and an excellent ability to recover flux after contamination experiments and could withstand continuous filtration operations for 60 h with a stable flux of 10.98 L m-2 h-1 bar-1. The as-prepared NF membrane's excellent water flux, selective rejection of salts, and outstanding fouling resistance make it ideal for efficient desalination, and it also provides novel insights into the design of antifouling membranes.

Emerging Nanomaterials for Drinking Water Purification: A New Era of Water Treatment Technology

The applications of nanotechnology in the field of water treatment are rapidly expanding and have harvested significant attention from researchers, governments, and industries across the globe. This great interest stems from the numerous benefits, properties, and capabilities that nanotechnology offers in addressing the ever-growing challenges related to water quality, availability, and sustainability. This review paper extensively studies the applications of several nanomaterials including: graphene and its derivative-based adsorbents, CNTs, TiO2 NPs, ZnO NPs, Ag NPs, Fe NPs, and membrane-based nanomaterials in the purification of drinking water. This, it is hoped, will provide the water treatment sector with efficient materials that can be applied successfully in the water purification process to help in addressing the worldwide water scarcity issue.

Biomass-Derived Cellulose Acetate Membranes Modified with TiO2/Graphene Oxide for Oil-In-Water Emulsion Treatment

Considering the environmental impact and health risks caused by oily wastewater in the petrochemical industry, it is crucial to develop more efficient separation techniques than traditional methods, such as membrane separation, for treating stable emulsions enriched with natural surfactants. This study investigated the preparation of dense cellulose acetate membranes from a low-cost biomass precursor (Luffa cylindrica) and their modification with graphene oxide (GO) and TiO2 nanoparticles, aiming to obtain a polymeric nanocomposite with good flux characteristics and selectivity for the treatment of oil/water emulsions. The materials obtained were characterized using techniques such as X-ray diffraction, nuclear magnetic resonance spectroscopy, infrared absorption spectroscopy, along with optical and scanning electron microscopy, among others. The membranes were prepared by the casting technique and modified with the above-mentioned nanostructured materials. Flux analyses with petroleum emulsion revealed that membranes modified with GO and TiO2 nanoparticles showed significant improvements in antifouling resistance compared to unmodified membranes. These enhanced properties highlight the potential of modified cellulose acetate membranes for application in industrial wastewater treatment.

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver-graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm^-1 of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe²⁺) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10-100 mg L^-1 towards purification of groundwater for safe drinking water.

Nano-enhanced sulfonated poly(arylene ether sulfone) composite membranes and their characterization

Chlorine is a widely used oxidizing agent in desalination to control bacteria that cause biofouling. The lack of chlorine resistance in commercial desalination membranes urged the development of an alternate polymer material. In this study, commercially available copolymer (SES0005, AquafoneTM), resistant to dissolved chlorine in water, has theoretical IEC of 2.08 meq.g-1 is blended with 0.5-15 %(w/w) TiO2 nanoparticles of <25 nm diameter and 45-55 m2.g-1 surface area by using ball milling device. SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy) result supports TiO2 content and uniform distribution. The chlorine stability of membranes was evaluated in sodium hypochlorite solution from 100 to 2000 ppm (pH 9). TGA and FT-IR analysis were performed for these membranes. The 1.5 %(w/w) TiO2 nano-enhanced membrane water retention is 23 % which is ∼53 % higher than that of pristine (15 %) membrane. Tensile strength of pristine and 0.5 %(w/w) TiO2 nano-enhanced membrane is 23, and 44 MPa, respectively. TiO2 nanoparticle addition improved dimensional and mechanical properties. This study attempts to correlate the SES polymer-TiO2 interactions with the characterization techniques.

Performance study of fouling resistant novel ultrafiltration membranes based on the blends of poly (ether ether sulfone)/poly (vinyl pyrrolidone)/nano-titania for the separation of humic acid, dyes and biological macromolecular proteins from aqueous solutions

This study explains the use of a ultrafiltration membrane made of polyvinyl pyrrolidone (PVP) and poly(ether ether sulfone) (PEES)/Nano-titania (n-TiO₂) for the separation of organic compounds. The results of the tests for porosity, water content, surface chemistry, membrane morphology, and contact angle demonstrated that the developed membranes have more hydrophilicity than PEES membranes due to the redundant hydrophilic nature of PVP and n-TiO₂. The membrane pure water flux, which contains 5 wt% PVP and 1.5 wt% n-TiO_2, was 312.76 Lm^-2h^-1, about three-fold higher than that of pristine membrane (95.71 Lm^-2h^-1). Employing bovine serum albumin as a model foulant, the fouling resistance of the PEES/PVP/n-TiO₂ membrane was examined. According to the analysis of flux recovery ratio and irreversible resistance, modified membranes were less likely to foul, and the PEES/n-TiO₂ membrane with 5% PVP addition was recommended as optimal. The fabricated membranes effectively removed more than 95% of various organic compounds such as humic acid, safranin O, egg albumin, pepsin, and trypsin from aqueous solution. Permeability of safranin O and humic acid of PEES/PVP/n-TiO₂ membranes was about 118 Lm^-2h^-1 and 138 Lm^-2h^-1, respectively.

Planning of smart gating membranes for water treatment

The use of membranes in desalination and water treatment has been intensively studied in recent years. The conventional membranes however have various problems such as uncontrollable pore size and membrane properties, which prevents membranes from quickly responding to alteration of operating and environmental conditions. As a result the membranes are fouled, and their separation performance is lowered. The preparation of smart gating membranes inspired by cell membranes is a new method to face these challenges. Introducing stimuli-responsive functional materials into traditional porous membranes and use of hydrogels and microgels can change surface properties and membrane pore sizes under different conditions. This review shows potential of smart gating membranes in water treatment. Various types of stimuli-response such as those of thermo-, pH-, ion-, molecule-, UV light-, magnetic-, redox- and electro-responsive gating membranes along with various gel types such as those of polyelectrolyte, PNIPAM-based, self-healing hydrogels and microgel based-smart gating membranes are discussed. Design strategies, separation mechanisms and challenges in fabrication of smart gating membranes in water treatment are also presented. It is demonstrated that experimental and modeling and simulation results have to be utilized effectively to produce smart gating membranes.