Second interfacial polymerization on polyamide surface using aliphatic diamine with improved performance of TFC FO membranes

Recent advances in surface tailoring of thin film forward osmosis membranes: A review

The recent advancements in fabricating forward osmosis (FO) membranes have shown promising results in desalination and water treatment. Different methods have been applied to improve FO performance, such as using mixed or new draw solutions, enhancing the recovery of draw solutions, membrane modification, and developing FO-hybrid systems. However, reliable methods to address the current issues, including reverse salt flux, fouling, and antibacterial activities, are still in progress. In recent decades, surface modification has been applied to different membrane processes, including FO membranes. Introducing nanochannels, bioparticles, new monomers, and hydrophilic-based materials to the surface layer of FO membranes has significantly impacted their performance and efficiency and resulted in better control over fouling and concentration polarization (CP) in these membranes. This review critically investigates the recent developments in FO membrane processes and fabrication techniques for FO surface-layer modification. In addition, this study focuses on the latest materials and structures used for the surface modification of FO membranes. Finally, the current challenges, gaps, and suggestions for future studies in this field have been discussed in detail.

Arginine-Functionalized Thin Film Composite Forward Osmosis Membrane Integrating Antifouling and Antibacterial Effects

Membrane fouling is an inevitable obstacle of polyamide composite forward osmosis (FO) membranes in oily wastewater treatment. In this study, zwitterionic arginine (Arg) is grafted onto nascent self-made FO polyamide poly(ether sulfone) (PA-PES) membrane, imparting superior hydrophilic, antifouling, and antibacterial properties to the membrane. Detailed characterizations revealed that the Arg-modified (Arg-PES) membrane presented obviously surface positively charged and unique morphology. Results showed that our strategy endowed the optimized membrane, the water flux increased by 113.2% compared to the pristine membrane, respectively, meanwhile keeping high NaCl rejection > 93.9% (with DI water as feed solution and 0.5 M NaCl as draw solution, FO mode). The dynamic fouling tests indicated that the Arg-PES membranes exhibited much improved antifouling performance towards oily wastewater treatment. The flux recovery ratios of the membrane were as high as 92.0% for cationic emulsified oil (cetyl pyridinium chloride, CPC), 87.0% for neutral emulsified oil (Tween-80), and 86.0% for anionic emulsified oil (sodium dodecyl sulfate, SDS) after washing, respectively. Meanwhile, the Arg-PES membranes assembled with guanidine cationic groups exhibited an enhanced antibacterial property against E. coli, which exhibited a high antibacterial efficiency of approximately 96%. Consequently, the newly arginine functionalized FO membrane possesses impressive antifouling performance, while simultaneously resisting bacterial invasion, thus rendering it an ideal alternative for oily wastewater treatment in the FO process.

Surface modification of thin film composite forward osmosis membrane using graphene nanosheets for water desalination

In this study, the main motivation of this work is desalination of water for irrigation arid area such as Sidri- Baba basins- south Sinai, Egypt. Also, the novelty of this work is modification of TFC surface membrane by mix of HA, DA and GO to get high performance of FO technique. Interfacial polymerization was employed to modify a thin-film composite (TFC) membrane for forward osmosis (FO) applications; moreover, graphene oxide (GO) nanosheets (GONs), a dopamine solution (DA), and naturally accessible humic acid (HA) were modified on a polyethersulfone (PES) substrate. The effects of the different quantities of GO, HA, and DA on the membrane surfaces, as well as their various cross-sectional morphologies and FO-desalination capabilities, were investigated. The integrated TFC membrane containing appropriate GO, HA, and DA blends outperformed the control membrane, obtaining high water flux, and high salt rejection. Furthermore,.

Improved Forward Osmosis Performance of Thin Film Composite Membranes with Graphene Quantum Dots Derived from Eucalyptus Tree Leaves

The major challenges in forward osmosis (FO) are low water flux, high specific reverse solute flux (SRSF), and membrane fouling. The present work addresses these problems by the incorporation of graphene quantum dots (GQDs) in the polyamide (PA) layer of thin-film composite (TFC) membranes, as well as by using an innovative polyethersulfone nanofiber support for the TFC membrane. The GQDs were prepared from eucalyptus leaves using a facile hydrothermal method that requires only deionized water, without the need for any organic solvents or reducing agents. The nanofiber support of the TFC membranes was prepared using solution blow spinning (SBS). The polyamide layer with GQDs was deposited on top of the nanofiber support through interfacial polymerization. This is the first study that reports the fouling resistance of the SBS-nanofiber-supported TFC membranes. The effect of various GQD loadings on the TFC FO membrane performance, its long-term FO testing, cleaning efficiency, and organic fouling resistance were analyzed. It was noted that the FO separation performance of the TFC membranes was improved with the incorporation of 0.05 wt.% GQDs. This study confirmed that the newly developed thin-film nanocomposite membranes demonstrated increased water flux and salt rejection, reduced SRSF, and good antifouling performance in the FO process.

Metal organic framework UiO-66 incorporated ultrafiltration membranes for simultaneous natural organic matter and heavy metal ions removal

In this work, a new type of UiO-66 incorporated polysulfone (PSf) ultrafiltration (UF) membranes was fabricated to enhance antifouling properties and heavy metal ions removal efficiency. The UF membranes incorporating different loadings of the UiO-66 filler were prepared via the classical phase inversion process. These membranes unveiled enhanced hydrophilicity, porosity, water uptake, zeta potential, mechanical strength, permeability, and HA removal ratios due to the incorporation of hydrophilic UiO-66 fillers. Particularly, HA rejection ratios were observed to be approximately 93% for all the modified membranes, which was attributed to electrostatic repulsion interactions between the hydrophilic groups of HA and UiO-66. Moreover, the antifouling abilities of the modified membranes were evaluated and found to be much better with a high flux recovery ratio (FRR) of about 88% when compared to the blank PSf membrane (only around 34%). Moreover, the UiO-66 incorporated membranes were highly-effective in the removal of contaminants like heavy metal ions (Sr²⁺, Pb²⁺, Cd²⁺, and Cr⁶⁺) and HA at the same time. Overall, the PSf UF membranes incorporating UiO-66 opened up a new avenue to enhance the membrane hydrophilicity, permeability, antifouling properties as well as heavy metal ions removal abilities.

Enhancing Chlorine Resistance and Water Permeability during Forward Osmosis Separation Using Superhydrophilic Materials with Conjugated Systems

Poor resistance to free chlorine severely impairs the service of conventional polyamide (PA) membrane in water treatment. Here we design a series of superhydrophilic aromatic sulfonate materials (ASMs) comprising successively increasing conjugated systems and ionizable groups (ASM-1, ASM-2, ASM-3) to develop a chlorine-resistant membrane via chemical modification. By altering the membrane physicochemical properties and surface structure, ASMs substantially improve the chlorine resistance and water permeability of membrane. With 0.5 M NaCl as the draw solution, all ASMs enhance membrane water fluxes by more than 60% relative to those of the nascent PA membrane in forward osmosis (FO) processes. After exposed to a 1000 ppm sodium hypochlorite solution for 2-8 h, the modified membranes exhibit smaller variations in FO performance than the PA membrane. Having the largest conjugated system and the most sulfonate groups, ASM-3 enables the membrane to sustain a chlorination strength of up to 8000 ppm·h with an insignificant NaCl loss during the FO process, surpassing other recently developed PA membranes in chlorine resistance. These results manifest that the combination of a large conjugated system and ionizable group is key for imbuing membrane with excellent chlorine resistance and water permeability.

Graphene Oxide Incorporated Forward Osmosis Membranes With Enhanced Desalination Performance and Chlorine Resistance

In this work, grapheme oxide (GO) nano-sheets were synthesized and dispersed in the aqueous phase for the interfacial polymerization (IP) process to develop a new type of thin-film composite (TFC) membranes for forward osmosis (FO) applications. The effects of the GO concentrations on the membrane surfaces and cross-sectional morphologies and FO desalination performances of the as-prepared TFC membranes were investigated systematically. Compared with the control membrane, the optimal GO-incorporated TFC membrane displayed higher water flux, less specific reverse solute flux (SRSF) and lower structure parameter. Moreover, the optimized membrane showed 75.0 times higher chlorine resistance than the control membrane. In general, these new type of membranes could be an effective strategy to fabricate high-performance FO membranes with good desalination performance and chlorine resistance.

Tris(hydroxymethyl)aminomethane-grafted polyamine nanofiltration membrane: enhanced antifouling and pH resistant properties

In this study, to fabricate a pH resistant membrane with antifouling properties, a Tris-grafted polyamine thin film composite (TFC) membrane has been synthesized.

A Bifunctional Zwitterion That Serves as Both a Membrane Modifier and a Draw Solute for Forward Osmosis Wastewater Treatment

Producing clean water and simultaneously recovering valuable compounds are a big challenge in wastewater treatment. Here we designed a bifunctional zwitterion of (1-(3-aminopropyl)imidazole) propanesulfonate (APIS) for membrane modification and being a draw solute as well for water production and protein enrichment via forward osmosis (FO). Immobilized to the membrane surface by a fast amidation reaction, APIS endows the membrane with favorable properties benefiting the FO process. The APIS-modified sulfonated poly(ether sulfone) (APIS-sPES) membrane produces a water flux 101% higher than that of the nascent membrane (from 9.3 to 18.7 LMH) with 0.5 M NaCl as the draw solution. The APIS-sPES membrane also exhibits higher fouling resistance with a much smaller decline in water permeation and stronger renewability with the flux restored to 88% of the original value compared to a 59% recovery rate of the nascent membrane after 20-h experiments against a 200 ppm ovalbumin solution. APIS produces a fair good water flux coupled with negligible reverse diffusion when used as a draw solute and can be readily regenerated via pH regulation. Unlike the conventional NaCl draw solute, APIS does not contaminate or damage protein structure. The APIS-sPES membrane and APIS draw solute prove a perfect match in protein-containing wastewater treatment and protein enrichment.

Membrane Surface Engineering with Bifunctional Zwitterions for Efficient Oil-Water Separation

Chemical modification provides a solution to the membrane fouling problem in oily water purification. However, complicated synthesis processes and harsh reaction conditions are frequently encountered with this approach. Here we developed two bifunctional zwitterionic materials, i.e., n-aminoethyl piperazine propanesulfonate (P-SO₃-NH₂) and 1,4-bis (3-aminopropyl) piperazine propanesulfonate (P-2SO₃-2NH₂), by a clean method and grafted them onto membrane surface via a fast single-step reaction. These materials endow the resultant membrane a more hydrophilic and smoother surface, significantly improving the water permeability, fouling resistance and recyclability of membrane in forward osmosis oily water reclamation. The water fluxes produced by the P-2SO₃-2NH₂ modified membrane are 47% (from 20.0 to 29.3 LMH) and 60% (from 16.0 to 25.6 LMH) higher than those of the unmodified membrane when DI water and an oily emulsion (1500 ppm) as the respective feeds. A higher water flux recovery is also achieved for the P-2SO₃-2NH₂ modified membrane (94%) than that of the nascent membrane (82%) after a 12-h experiment. These promising findings coupled with a facile and efficient membrane modification approach provide inspiration for both membrane exploration and oily water treatment.

Characteristics and influencing factors of organic fouling in forward osmosis operation for wastewater applications: A comprehensive review

Wastewater reuse is considered one of the most promising practices for the achievement of sustainable water management on a global scale. In the context of the safe reuse of water, membrane filtration is a competitive technique due to its superior efficiency in several processes. However, membrane fouling by organics is an inevitable challenge that is encountered during the practical application of membrane processes. The resolution of the membrane fouling challenge requires an in-depth understanding of many complex interactions between organic foulants and the membrane. In the last few decades, the forward osmosis (FO) membrane process, which exploits osmosis as a driving force, has emerged as an effective technology for water production with low energy consumption, thus leveraging the water-energy nexus. However, their successful application is severely hampered by membrane fouling, which is caused by such complex fouling mechanisms as cake enhanced osmotic pressure (CEOP), reverse salt diffusion (RSD), internal, and external concentration polarization as well as by the traditional fouling processes encompassing colloids, microbial (biofouling), inorganic, and organic fouling. Of these fouling types, the fouling potential of organic matter in FO has not been given sufficient attention, in particular, when FO is applied to wastewater treatment. This paper aims to provide a comprehensive overview of FO membrane fouling for wastewater applications with a special focus on the identification of the major factors that lead to the unique properties of organic fouling in this filtration process. Based on the critical assessment of organic fouling formation and the governing mechanisms, proposals were advanced for future research aimed at the mitigation of FO membrane fouling to enhance process efficiency in wastewater applications.

Novel Ionic Grafts That Enhance Arsenic Removal via Forward Osmosis

Current forward osmosis (FO) membranes are unsuitable for arsenic removal from water because of their poor arsenic selectivity. In this study, we designed and synthesized a series of novel imidazolium-based ionic liquids via one-step quaternization reactions and grafted these novel compounds on to conventional thin-film composite FO membranes for treatment of arsenic-containing water. The newly developed ionic membranes contained a functionalized selective polyamide layer grafted with either carboxylic acid/carboxylate or sulfonate groups that drastically enhanced membrane hydrophilicity and thus FO water permeation. Ionic membranes modified with sodium 1-ethanesulfonate-3-(3-aminopropyl) imidazolium bromide (NH₂-IM-(CH₂)₂-SO₃Na) outperformed pristine membranes with higher water recovery efficiency. Exceptional performance was achieved with this ionic membrane in FO arsenic removal with a water flux of 11.0 LMH and a rejection higher than 99.5% when 1000 ppm arsenic (HAsO₄^2-) as the feed with a dilute NaCl solution (0.5 M) as the draw solution under the FO mode. Ionic membranes developed in this work facilitated FO for the treatment of arsenic-containing water while demonstrating its superiority over incumbent technologies with more efficient arsenic removal.

In Situ Surface Modification of Thin-Film Composite Polyamide Membrane with Zwitterions for Enhanced Chlorine Resistance and Transport Properties

High-performance chlorine-resistant thin-film composite (TFC) membranes with zwitterions were fabricated by in situ surface modification of polyamide with 2,6-diaminopyridine and the subsequential quaternization with 3-bromopropionic. The successful modification of the TFC polyamide surface with zwitterions was confirmed by various characterizations including surface chemistry, surface hydrophilicity, and surface charge. The transport performance of the membrane was measured in both of the cross-flow reverse osmosis (RO) and forward osmosis processes, and the results showed that the modified TFC membrane improved both of its water permeability and perm-selectivity with the increased A and A/ B ratios upon modification with zwitterions. The chlorination challenging experiments were performed to demonstrate that the modified membrane enhanced its chlorine resistance without affecting its salt rejection upon 16 000 ppm·h chlorination exposure. A chlorination mechanism study illustrated that the modified membrane with zwitterions could prevent the Orton rearrangement of the benzene ring of the polyamide layer. Importantly and excitingly, the optimal chlorinated TFC membrane with zwitterions achieved a very high water flux of 72.15 ± 2.55 LMH with 99.67 ± 0.09% of salt rejection in the cross-flow RO process under 15 bar.

A polyethersulfone-bisphenol sulfuric acid hollow fiber ultrafiltration membrane fabricated by a reverse thermally induced phase separation process

A novel antifouling polyethersulfone (PES) hollow fiber membrane was modified by the addition of bisphenol sulfuric acid (BPA-PS) using a reverse thermally induced phase separation (RTIPS) process. BPA-PS was synthesized by click chemistry and was blended to improve the hydrophilicity of PES hollow fiber membranes. The performance of PES/BPA-PS hollow fiber membranes, prepared with different contents of BPA-PS and at different temperatures of the coagulation water bath, was characterized by scanning electron microscopy (SEM), pure water flux (J w), BSA rejection rate (R), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and water contact angle measurements. SEM morphologies revealed that a finger-like cross-section emerged in the hollow fiber membrane by a non-solvent induced phase separation (NIPS) mechanism while a sponge-like cross-section appeared in the hollow fiber membrane via the RTIPS method. Both FTIR and XPS analysis indicated that the sulfate group in BPA-PS was successfully blended with the PES membranes. The results from AFM and water contact angle measurements showed that the surface roughness increased and the hydrophilicity of the PES/BPA-PS hollow fiber membrane was improved with the addition of BPA-PS. The results demonstrated that the PES/BPA-PS membrane with 1 wt% BPA-PS via RTIPS exhibited optimal properties.

Synthetic polymer materials for forward osmosis (FO) membranes and FO applications: a review

Forward osmosis (FO) has played an important role in alleviating the problems caused by freshwater shortage and water contamination in recent years. However, issues of low water permeability, reverse solute diffusion, concentration polarization and membrane fouling are still widely present in FO processes. These challenges are the current research focus in exploring novel FO membranes. Fabricating FO membranes from chemically modified commercial polymers is a relatively novel approach and has proven effective in obtaining appropriate FO membranes. This paper focuses on the progress of FO membranes made specially from chemically modified polymer materials. First of all, a brief overview of commercial polymers commonly used for FO membrane fabrication is provided. Secondly, the chemical modification strategies and synthesis routes of novel polymer materials as well as the resultant FO membrane performance are presented. The strengths and weaknesses of chemical modifications on polymer materials are assessed. Then, typical FO applications facilitated by the FO membranes made from modified polymer materials are exemplified. Finally, challenges and future directions in exploring novel polymers through chemical modifications for FO membrane fabrication are highlighted. This review may provide new insights into the future advancement of both novel membrane materials and FO membranes.

Dopamine incorporating forward osmosis membranes with enhanced selectivity and antifouling properties

A new type of polyamide thin-film composite forward osmosis (FO) membranes were prepared by controlling dopamine self-polymerization in the aqueous phase during interfacial polymerization. The as-prepared membranes were investigated by attenuated total reflection Fourier transform infrared, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, atomic force microscopy and water contact angle measurements. The influence of the dopamine self-polymerization degree with different polydopamine particle sizes on membrane morphologies and chemical properties was studied by regulating dopamine concentrations in the aqueous phase. FO performance of the membrane was evaluated under two different modes, i.e. active layer facing draw solution (AL-DS) and active layer facing feed solution (AL-FS). The optimized FO membranes achieved a doubly enhanced water flux (22.08 L m⁻² h⁻¹) compared with the control membrane without dopamine incorporation, and a half-reduced reverse salt flux (32.77 mmol m⁻² h⁻¹) with deionized water as the feed and 1 M NaCl as the draw in the AL-FS mode. The optimized FO membrane showed a significantly reduced structural parameter (176 μm) compared with the control membrane (635 μm), indicating the minimised internal concentration polarization. Moreover, the new FO membranes had less flux decline than the control membrane, suggesting the improved antifouling performance of the membrane. Incorporation of dopamine during interfacial polymerization can be an effective strategy to fabricate high-performance FO membranes with excellent antifouling properties.

Incorporation of dopamine enhanced selectivity and antifouling properties of novel TFC polyamide FO membranes.

Synthesis and Application of Organic Phosphonate Salts as Draw Solutes in Forward Osmosis for Oil-Water Separation

The development of suitable draw solution in forward osmosis (FO) process has attracted the growing attention for water treatment purpose. In this study, a series of organic phosphonate salts (OPSs) are synthesized by one-step Mannich-like reaction, confirmed by FTIR and NMR characterizations, and applied as novel draw solutes in FO applications. Their solution properties including osmotic pressures and viscosities, as well as their FO performance as a function of the solution concentration are investigated systematically. In FO process, a higher water flux of 47-54 LMH and a negligible reverse solute flux can be achieved in the PRO (AL-DS) mode (active layer faces the draw solution) using a homemade thin-film composite membrane (PSF-TFC) and deionized water as the feed solution. Among all OPS draw solutes, the tetraethylenepentamine heptakis(methylphosphonic) sodium salt (TPHMP-Na) exhibits the best FO flux at 0.5 mol/kg concentration, which is further applied for the separation of emulsified oil-water mixture. The recovery of diluted OPS solutions is carried out via a nanofiltration (NF) system with a rejection above 92%. The aforementioned features show the great potential of OPS compounds as a novel class of draw solutes for FO applications.

Layered double hydroxide/graphene oxide hybrid incorporated polysulfone substrate for thin-film nanocomposite forward osmosis membranes

Herein, we report the use of a layered double hydroxide/graphene oxide (LDH/GO) hybrid as a nanofiller for a polysulfone (PSf) substrate in the fabrication of a thin film nanocomposite (TFN) forward osmosis (FO) membrane.