Polyethyleneimine, an effective additive for polyethersulfone ultrafiltration membrane with enhanced permeability and selectivity

CoFe2O4 modified bentonite-based mixed matrix loose nanofiltration membranes for effective wastewater treatment

Mixed-matrix membranes (MMMs) with an ideal polymer/hydrophilic flux enhancer interface considerably recuperates the separation and purification performance of membrane. In this direction, a novel CoFe2O4 functionalized natural clay-bentonite (CoFe2O4@BT) material as a compatible flux enhancer was synthesized for preparation of mixed matrix based in polyethersulfone (PES) matrix. Here, the influences of CoFe2O4@BT on the morphology and performance of the MMMs membranes were systematically investigated using various analytical techniques. Meanwhile, the water flux and sepration eficiency of the CoFe2O4@BT-PES membranes significantly enhanced due to the incorporation of CoFe2O4@BT that altered hydrophilicity, pore and surface characteristic features. The water flux as well as separation efficiency range up to 95%, 94.69%, 94.16% of Congo red (CR), Crystal violet (CV), and humic acid (HA) respectively. Meanwhile, the fouling parameters demonstrated that the CoFe2O4@BT-PES membranes exhibited better antifouling property in the long term experiment comparing with commercial polyamide membrane. CoFe2O4@BT material incorporated membranes showed less decline ratio and a better recovery ratio. The high rejection of dyes with a high permeation flux of the newly designed membranes indicated an amazing possibility for dye purification. In this study, a potential dye mechanism for composite membranes impacted by synthetic CoFe2O4@BT was also put forth. Within the context of application considerations for environmental protection, new materials stock in membranes show good potential for the separation of different organic contaminants.

Synchronous Engineering for Biomimetic Murray Porous Membranes Using Isocyanate

Highly permselective and durable membranes are desirable for massive separation applications. However, currently most membranes prepared using nonsolvent-induced phase separation (NIPS) suffer from low permeability and a high fouling tendency due to the great challenges in a rational design and also practical approach for membrane optimization. Inspired by the natural Murray network from vascular plants, we developed a hierarchical membrane via a straightforward yet robust strategy, using isocyanate as a multifunctional additive. Thanks to the integrated functions of a phase separation regulator, blowing agent, cross-linker, and functionalization anchor of isocyanate, our strategy is featured as a perfect combination of a phase separation and chemical reaction, and it enables synchronous engineering of the membrane hierarchy on porosity and components. The representative membrane exhibits superior water permeance (334 L/m²·h·bar), protein retention (>98%), and antifouling ability (flux recover ratio ∼ 98%). This work highlights a versatile path for pursuing a highly enhanced performance of NIPS-made membranes, from the fancy perspective of Murray bionics.

Open-Celled Foams of Polyethersulfone/Poly(N-vinylpyrrolidone) Blends for Ultrafiltration Applications

Since membranes made of open porous polymer foams can eliminate the use of organic solvents during their manufacturing, a series of previous studies have explored the foaming process of various polymers including polyethersulfone (PESU) using physical blowing agents but failed to produce ultrafiltration membranes. In this study, blends containing different ratios of PESU and poly(N-vinylpyrrolidone) (PVP) were used for preparation of open-celled polymer foams. In batch foaming experiments involving a combination of supercritical CO2 and superheated water as blowing agents, blends with low concentration of PVP delivered uniform open-celled foams that consisted of cells with average cell size less than 20 µm and cell walls containing open pores with average pore size less than 100 nm. A novel sample preparation method was developed to eliminate the non-foamed skin layer and to achieve a high porosity. Flat sheet membranes with an average cell size of 50 nm in the selective layer and average internal pore size of 200 nm were manufactured by batch foaming a PESU blend with higher concentration of PVP and post-treatment with an aqueous solution of sodium hypochlorite. These foams are associated with a water-flux up to 45 L/(h m2 bar). Retention tests confirmed their applicability as ultrafiltration membranes.

Fabrication of an antifouling PES ultrafiltration membrane via blending SPSF

Sulfonated polysulfone (SPSF) with different sulfonation degrees (10%, 30%, and 50%) was added to polyethersulfone (PES) to improve the separation and antifouling performance of polyethersulfone ultrafiltration membranes. The PES/SPSF blend ultrafiltration membrane was prepared by the non-solvent induced phase inversion method (NIPS), and the effect of sulfonation degree on the ultrafiltration performance was studied. The compatibility of SPSF and PES was calculated by the group contribution method, and confirmed by differential scanning calorimetry (DSC). The morphology and surface roughness of the membrane were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), the chemical composition of the membrane was analyzed by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR), and the permeability and anti-fouling performance of the blend membrane were studied through filtration experiments. The research shows that the flux and anti-fouling performance of the blend membrane have been improved after adding SPSF. When the sulfonation degree of the SPSF is 30%, the pure water flux of the blend membrane can reach 530 L m⁻² h⁻¹, the rejection rate of humic acid (HA) is 93%, the flux recovery rate of HA increases from 69.23% to 79.17%, and the flux recovery rate of BSA increases from 72.56% to 83%.

The chemical structures of (a) PES and (b) SPSF.

Preparation and adsorption properties of hyperbranched polyethyleneimine-cellulose nanofiber aerogel

A novel cellulose-based aerogel was prepared by a chemical cross-linking reaction and hydrogen bonding between cellulose nanofibers (CNF), polyethylene glycol diglycidyl ether (PEGDE), and hyperbranched polyethyleneimine (HPEI).

Fabrication of Polysulfone-Surface Functionalized Mesoporous Silica Nanocomposite Membranes for Removal of Heavy Metal Ions from Wastewater

Membranes are an efficient way to treat emulsified heavy metal-based wastewater, but they generally come with a trade-off between permeability and selectivity. In this research, the amine and sulphonic groups on the inner and outer surface of mesoporous silica nanoparticles (MSNs) were first modified by a chemical approach. Then, MSNs with amine and sulphonic groups were utilized as new inorganic nanofiller to fabricate mixed matrix polysulfone (PSU) nanocomposite membranes using the classical phase inversion approach. The resultant nanoparticles and membranes were characterized by their physico-chemical characteristics as well as determination of pure water permeability along with cadmium and zinc ion removal. Embedding nanoparticles resulted in a significant rise in the water permeability as a result of changes in the surface properties and porosity of the membrane. Furthermore, the efficiency of developed membranes to remove cadmium and zinc was significantly improved by more than 90% due to the presence of functional groups on nanoparticles. The functionalized-MSNs/PSU nanocomposite membrane has the potential to be an effective industrial effluent removal membrane.

Fabrication of a hybrid ultrafiltration membrane based on MoS2 modified with dopamine and polyethyleneimine

The hydrophobicity of ultrafiltration membranes is the main cause of membrane fouling and reduced permeability, so it is necessary to improve the hydrophilicity and anti-fouling performance of ultrafiltration membrane materials. MoS₂ nanoparticles that were modified with polydopamine (PDA) and polyethyleneimine (PEI), named MoS₂-PDA-PEI, were added to fabricate a polyethersulfone ultrafiltration membrane (PES/MoS₂-PDA-PEI) for the first time. The effects of modified MoS₂ nanoparticles on membrane performance were clarified. The results indicated that the permeability, rejection, and anti-fouling capability of the hybrid PES/MoS₂-PDA-PEI membrane have been improved compared with the pristine PES membrane. When the content of MoS₂-PDA-PEI nanoparticles in the membrane is 0.5%, the pure water flux of the hybrid membrane reaches 364.03 L m⁻² h⁻¹, and the rejection rate of bovine serum albumin (BSA) and humic acid (HA) is 96.5% and 93.2% respectively. The flux recovery rate of HA reached 97.06%. As expected, the addition of MoS₂-PDA-PEI nanoparticles promotes the formation of the porous structure and improves the hydrophilicity of the membrane, thereby improving its antifouling performance.

The hydrophobicity of ultrafiltration membranes is the main cause of membrane fouling and reduced permeability, so it is necessary to improve the hydrophilicity and anti-fouling performance of ultrafiltration membrane materials.

A review on surface modification methods of poly(arylsulfone) membranes for biomedical applications

Considerable methods have so far been used for the surface modification of biomedical membranes. Several reviews and articles have been published on the improvements achieved in the field of poly(arylsulfone) membranes subjected to various surface modification methods and used in biomedical applications. This review concentrates on the surface modification, biological applications and future perspective of the poly(arylsulfone) biomedical membranes. Different surface modification procedures employed for the poly(arylsulfone) membranes have been classified, studied and compared. Diverse surface modification techniques include surface coating, chemical modification and immobilization/cross-linking, grafting, surface zwitterionicalization, mussel-inspired coating and layer-by-layer assembly. Furthermore, we review the recent research studies performed on the surface modification of the poly(arylsulfone) biomedical membranes. Meanwhile, the properties of biomedical membranes are also discussed in each section. At last, the future perspective and challenges of the strategies utilized for the surface modification of poly(arylsulfone) biomedical membranes are presented.

Evaluation of the formation and antifouling properties of a novel adsorptive homogeneous mixed matrix membrane with in situ generated Zr-based nanoparticles

In situ generation is a powerful technique used to prepare homogenous adsorptive mixed matrix membranes (MMMs) containing functional nanoparticles, although the mechanism of formation of the membranes is not yet clear and there have been few published evaluations of membrane fouling. We therefore used this method to prepare a novel homogeneous adsorptive Zr-based nanoparticle–polyethersulfone (PES) MMM and systematically studied the mechanism of membrane formation at the atomic level. As the amount of ZrOCl₂·8H₂O in the casting solution increased, the phase inversion kinetics changed from instantaneous demixing due to the thermodynamic enhancement effect to a delayed demixing process caused by viscosity hindrance. The in situ generation of nanoparticles in these MMMs can be divided into three stages: the migration stage, the exfoliation stage and the stable stage. Our findings provide a fundamental understanding of the interface chemistry in the development of in situ generated MMMs. M2 showed a higher adsorption of As(v) than the pure PES membrane and could be reused after regeneration. The removal of As(v) from the M2 filtration system mainly took place via adsorption rather than size exclusion, as confirmed by EDS and experimental data. The presence of humic acid slightly inhibited the removal of As(v) during the filtration process as a result of the barrier effect caused by the formation of a filter cake via humic acid fouling. The filtration of a bovine serum albumin solution showed that the MMM with in situ generated nanoparticles had better antifouling properties than the PES membrane alone in multiple applications as a result of the enhanced hydrophilic surface.

A homogeneous in situ generated Zr-based NPs/PES mixed matrix membrane with enhanced adsorptive and antifouling performance was developed.

Low pressure operated ultrafiltration membrane with integration of hollow mesoporous carbon nanospheres for effective removal of micropollutants

An effective way to remove micropollutants is desirable for water purification. In this work, a dual-functional ultrafiltration (DFUF) membrane was fabricated by loading hollow mesoporous carbon nanospheres (HMCNs) into the finger-like support layer pores of the polymeric ultrafiltration (UF) membrane. The designed DFUF membrane combines the high selectivity of ultrafiltration that removes macromolecules based on size exclusion mechanism, and excellent adsorption capacity of HMCNs towards micropollutants in water. When tetracycline (TCN) and 17β-Estradiol (E2) were selected as model micropollutants, corresponding 97 % and 94 % removal were achieved at a low pressure less than 0.15 bar and a flux of 50 and 64 L h^-1 m^-2 (estimated residence time less than 6 s), respectively. Moreover, simultaneous removal of multiple pollutants was demonstrated by filtering a mixture containing TCN and polyethylene glycols (PEG) 600 kDa macromolecules. Over a long filtration period (more than 60 h) that produced 3180 L/m² of permeate, the TCN concentration reduced from 100 μg/L in the feed to less than 10 μg/L in the permeate. The above results indicate that the DFUF membrane is capable of removing the small molecular and macromolecular pollutants simultaneously at low pressure, and hence offers remarkable potential in water treatment applications.

Improved filtration performance and antifouling properties of polyethersulfone ultrafiltration membranes by blending with carboxylic acid functionalized polysulfone

Ultrafiltration membranes with improved filtration performance and antifouling properties have been synthesized through blending polyethersulfone with carboxylic acid functionalized polysulfone.

A synergetic analysis method for antifouling behavior investigation on PES ultrafiltration membrane with self-assembled TiO2 nanoparticles

Fouling of ultrafiltration (UF) membranes is a major impediment for their use in drinking water production. Mixed matrix membranes (MMMs) may have great opportunities in dealing with this challenge due to their hierarchical structures and multiple functionalities. In this study, a synergetic analysis method based on intermolecular adhesion force measurement and fouling process simulation was applied to investigate the fouling mechanism of polyethersulfone (PES) UF membranes containing in situ self-assembled TiO2 nanoparticles (NPs). The fouling resistance behavior and antifouling mechanism of the newly developed composite membranes were investigated with sodium alginate (SA), bovine serum albumin (BSA) and humic acid (HA) as model organic foulants. An improved antifouling effect was conspicuously observed for the composite membranes, expressed by a lower flux decline and significantly better cleaning efficiency. A strong correlation between the self-assembled structure of TiO2 NPs and the antifouling behavior of the composite membrane was observed. A lower magnitude and a narrower distribution of adhesion forces for the composite membrane suggest the effective suppression of foulants adsorption on the clean or fouled membrane. The simulation analysis indicates that the main fouling mechanism was standard blocking and cake filtration, further confirming the superiority of the NPs self-assembled structure in mitigating membrane fouling. This dual analysis method may provide a promising technological support for the application of modified UF membranes with self-assembled NPs in drinking water production.

Recovery of chemically degraded polyethyleneimine by a re-modification method: prolonging the lifetime of cation exchange membranes

Recovery of chemically degraded cation exchange membranes in a cyclic process.

Fouling behavior of polyethersulfone ultrafiltration membranes functionalized with sol–gel formed ZnO nanoparticles

The addition of sol–gel formed ZnO nanoparticles endows the PES membrane with an improved antifouling performance, which expands the potential application of UF membrane in drinking water treatment and wastewater reuse.