Fabrication of chitosan-aminopropylsilane graphene oxide nanocomposite hydrogel embedded PES membrane for improved filtration performance and lead separation

Biopolymeric Nanocomposites for Wastewater Remediation: An Overview on Recent Progress and Challenges

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications enhancing adsorbent efficacy against persistent waterborne pollutants. This review delves into recent advancements (2020-2023) in sustainable biopolymeric nanocomposites, spotlighting the applications of biopolymers like chitosan in wastewater remediation, particularly as adsorbents and filtration membranes along with their mechanism. The advantages and drawbacks of various biopolymers have also been discussed along with their modification in synthesizing biopolymeric nanocomposites by combining the benefits of biodegradable polymers and nanomaterials for enhanced physiochemical and mechanical properties for their application in wastewater treatment. The important functions of biopolymeric nanocomposites by adsorbing, removing, and selectively targeting contaminants, contributing to the purification and sustainable management of water resources, have also been elaborated on. Furthermore, it outlines the reusability and current challenges for the further exploration of biopolymers in this burgeoning field for environmental applications.

MOF@Polydopamine-incorporated membrane with high permeability and mechanical property for efficient fouling-resistant and oil/water separation

Metal organic frameworks (MOFs) have demonstrated great potential for their favorable impacts on the performance of water treatment membranes. Herein, the novel nanoparticles based on both nanoporous MOFs and organic PDA layer was exploited as a novel dopant for the fabrication of PES ultrafiltration (UF) membranes. The PDA was synthesized via oxidative self-polymerization under alkaline conditions and formed adhesive coatings on dispersed MOF. The properties of resulting membranes on the porosity, membrane morphology, hydrophilicity, permeability and anti-fouling performance were adequately investigated. The membranes incorporated with MOF@PDA exhibited exceptionally high permeability (209.02 L m-2·h-1), which is approximately 6 times higher than that of the pure PES membrane, and high BSA rejection (99.12%). Notably, the mechanical property and hydrophilicity of the PES membrane were both enhanced by MOF@PDA, and it has been demonstrated that greater hydrophilicity prevents fouling under practical conditions, which results in significant improvements in flux recovery ratio (FRR) (82%). In addition, the modified PES membranes were used to purify the oil/water emulsion, and the results indicates that the membranes have high permeability and rejection of oil/water emulsion, showing its great promise in practical oily sewage remediation.

Antifouling thin-film nanocomposite NF membrane with polyvinyl alcohol-sodium alginate-graphene oxide nanocomposite hydrogel coated layer for As(III) removal

Removal of As(III) from the polluted waters is a challenge. It should be oxidized to As(V) for increasing its rejection by RO membranes. However, in this research, As (III) is directly removed by a high permeable and antifouling membrane prepared through the surface coating and in-situ crosslinking procedure of polyvinyl alcohol (PVA) and sodium alginate (SA) as coating materials containing graphene oxide as a hydrophilic additive on a polysulfone support with glutaraldehyde (GA) chemical crosslinking agent. The properties of the prepared membranes were evaluated through contact angle, zeta potential, ATR-FTIR, SEM, and AFM. The addition of GO in the polymeric networks of SA and PVA hydrogel coating layers led to a better hydrophilicity and a smoother surface and a higher negative surface charge resulted in improvment of permeability and rejection of membranes. Among the prepared hydrogel-coated modified membranes, SA-GO/PSf indicated the highest pure water permeability (15.8 L m^-2 h^-1 bar^-1) and BSA permeability (9.57 L m^-2 h^-1 bar^-1), respectively. The best desalination performance (NaCl, MgSO₄, and Na₂SO₄ rejections of 60.0%, 74.5%, and 92.0%, respectively) and As(III) removal (88.4%) along with satisfactory stability and reusability in cyclic continuous filtration was reported for PVA-SA-GO membrane. In addition, the PVA-SA-GO membrane indicated improved fouling resistance toward BSA foulant with the lowest flux decline of 7%.

Modification of reinforced hollow fiber membranes with WO3 nanosheets for treatment of textile wastewater by membrane bioreactor

In this study, performance of braid reinforced hollow fiber membrane containing polyvinylidene fluoride (PVDF) embedded with tungsten trioxide (WO₃) nanosheets in a membrane bioreactor (MBR) was examined for textile wastewater treatment. The WO₃ nanosheets was synthesized and blended at different concentrations (0.1-0.02 wt%) in casting solutions of the membranes. The WO₃ nanosheets characterized using various tests such as XRD, FTIR, SEM, EDS, dot-mapping, and TEM. Furthermore, the effects of the increased WO₃ nanosheets into the PVDF matrix on the membrane morphology, hydrophilicity, permeability, antifouling, and COD and color removal efficiency was investigated. The addition of 0.1 wt% of the nanosheets reduces the water contact angle from 69.3° to 62.5° while increasing overall porosity from 37.5 to 43.2%. COD and color removal for PVDF/0.10 wt% WO₃ membrane was between 86-89% and 72-76%, respectively. While the TMP of modified WO₃ membranes did not significantly increase due to antimicrobial properties of the WO₃ nanosheets, the TMP of the pure PVDF membrane increase, indicating considerable cake layer fouling. The results of this study showed that modification of PVDF braid reinforced hollow fiber membrane using WO₃ nanosheets is promising membrane for MBR systems.

Construction of self-healing polyethersulfone ultrafiltration membrane by cucurbit[8]uril hydrogel via RTIPS method and host-guest chemistry

In this work, the self-healing polyethersulfone ultrafiltration membrane constructed by host-guest chemistry between cucurbit [8]uril (CB [8] is a family of macrocyclic compounds comprising 8 glycoluril units) and two guest molecules based on reverse thermally induced phase separation (RTIPS) method was developed, which had excellent self-healing performance, better mechanical properties, and high permeation flux and BSA rejection rate. The membrane autonomously restored it BSA rejection rate up to about 89% from rejection rate levels as low as 21% after damage. The observed self-healing performance were attributed to the swelling of pore-filled CB [8] hydrogel into the damage position, the molecular interdiffusion of the hydrogel chains, the strong hydrogen bond of the hydrogel chains and the host-guest interaction between CB [8] and two guest molecules (HEC-Np and PVA-MV). SEM morphologies illustrated that the prepared pore-filled membrane via the RTIPS method had homogeneous and porous skin surface and sponge-like cross-section, which imparted the prepared membranes with improved permeability and better mechanical properties. Properties of MR-CB [8] membranes, which varied with increased content of CB [8], were evaluated by permeability, water contact angle, thermogravimetric analysis (TGA), mechanical properties, FRR, scanning electron microscope (SEM) and atomic force microscopy (AFM). The contact angle water showed that CB [8] hydrogel enhanced the surface hydrophilicity of the prepared membrane. TGA illustrated that the thermal stability improved with the increased content of CB [8]. The optimal pore-filled CB [8] hydrogel membrane (MR-CB [8]₂) exhibited that the pure water flux reached 2100.5 L/m² h, while the BSA rejection rate remained at 86.0%. The results of this work suggested pore-filled CB [8] hydrogel membrane was a more promising way to develop polyethersulfone ultrafiltration membranes with self-healing performance.

Polyvinyl alcohol and sodium alginate hydrogel coating with different crosslinking procedures on a PSf support for fabricating high-flux NF membranes

Polyvinyl alcohol (PVA) and sodium alginate (SA) hydrogel-coated nanofiltration (NF) membranes with high-flux and permselectivity were prepared. The coating of PVA and SA hydrogel selective layer on a porous polysulfone (PSf)/non-woven fabric ultrafiltration substrate membrane was conducted through different three procedures including pre-crosslinking, in-situ crosslinking, and immersing crosslinking and the use of glutaraldehyde as a crosslinking agent. The properties and performances of all types of the prepared membranes were evaluated through ATR-FTIR spectroscopy, AFM, SEM, zeta potential, contact angle, and cross-flow permeation tests. The immersing technique resulted in the formation of TFC membranes with higher hydrophilicity, smoother surface layer, higher negative charge, higher permeation flux, higher salt rejection and better anti-fouling performance. Also, the higher negative surface charge of the immersing coated TFC membranes due to dissociation of hydrophilic functional groups of the PVA and SA hydrogel selective layer resulted in higher As(III) rejection. SA coated NF membrane through immersing method exhibited a higher pure water permeability of 11.2 L m^-2 h^-1 bar^-1, NaCl, MgSO₄, and Na₂SO₄ rejection of 38.2%, 55.1%, and 70.4%, respectively with As(III) rejection of 60.6%. All types of the PVA and SA hydrogel-coated PSf membranes possessed improved fouling resistance to BSA aqueous solution, superior anti-fouling performance was obtained with SA hydrogel coating through immersing method. Such optimum membranes indicated high stability in the long-term experiments. This study showed that the coating of the SA hydrogel layer on a PSf support through immersing method could be a promising candidate for fabricating high-flux NF membranes.

Graphene based composite membranes for environmental toxicology remediation, critical approach towards environmental management

Graphene-based composite membranes, as laminated, stacked, and assembled architectures of graphene, have surpassed other conventional membranes with their advanced and preeminent structural specialization and potential use in a wide range of sustainable and environmental applications. The characteristic membrane features such as distinct laminar morphology, tailored physicochemical properties, as well as extraordinary molecular properties have fascinated scientists. Due to remarkable mechanical properties, these membranes can be easily fabricated. Recent progress has been achieved by graphene and its derivatives-based membranes to purify water and gases for environmental remediation. This review explained the latest and groundbreaking advances in chemical design, fabrication, and application of graphene-based membranes. Special attention is paid to the recent developments on graphene-based composites into membranes with various forms: free-standing, layered, and graphene-based nanocomposite membranes. Furthermore, a unique approach on environmental management with as-fabricated membranes is provided by discussing the effect of physicochemical properties. Consequently, their full-scale use for environmental management, water purification, gas purification, and biological treatments will pave the way for their promising features and realize their future prospects.

Hyaluronic Acid Methacrylate Hydrogel-Modified Electrochemical Device for Adsorptive Removal of Lead(II)

This paper presents the development of a compact, three-electrode electrochemical device functionalized by a biocompatible layer of hyaluronic acid methacrylate (HAMA) hydrogel for the adsorptive removal of detrimental lead (Pb(II)) ions in aqueous solutions. An adsorption mechanism pertaining to the observed analytical performance of the device is proposed and further experimentally corroborated. It is demonstrated that both the molecular interactions originating from the HAMA hydrogel and electrochemical accumulation originating from the electrode beneath contribute to the adsorption capability of the device. Infrared spectral analysis reveals that the molecular interaction is mainly induced by the amide functional group of the HAMA hydrogel, which is capable of forming the Pb(II)–amide complex. In addition, inductively coupled plasma mass spectrometric (ICP-MS) analysis indicates that the electrochemical accumulation is particularly valuable in facilitating the adsorption rate of the device by maintaining a high ion-concentration gradient between the solution and the hydrogel layer. ICP-MS measurements show that 94.08% of Pb(II) ions present in the test solution can be adsorbed by the device within 30 min. The HAMA hydrogel-modified electrochemical devices exhibit reproducible performance in the aspect of Pb(II) removal from tap water, with a relative standard deviation (RSD) of 1.28% (for n = 8). The experimental results suggest that the HAMA hydrogel-modified electrochemical device can potentially be used for the rapid, on-field remediation of Pb(II) contamination.

Different metal-doped ZnS quantum dots photocatalysts for enhancing the permeability and antifouling performances of polysulfone membranes with and without UV irradiation

In this study, the effect of three different transition metal ion dopants (Mn²⁺, Fe^2+, and Co²⁺) on the characteristics of zinc sulfide (ZnS) quantum dots (QDs) was investigated and the obtained QDs photocatalysts were applied for the modification of polysulfone (PSf) mixed matrix membranes to reduce membrane fouling. The synthesized QDs and fabricated membranes were fully identified with SEM, TEM, AFM, FTIR analyses, and also underwent porosity and contact angle tests. Flux recovery ratios (FRR) significantly increased from 69.8% (bare) to 85.0% (1% Fe-doped ZnS QDs) after modification of membranes with metal-doped QDs. The contact angles of the prepared membranes decreased with doping of dissimilar metals, therefore hydrophilicity increased, and reversible/non-reversible blockages were improved. Besides, the use of UV irradiation during the washing of the membranes increased the FRR of the photocatalytic activated membranes to 91.2%. Compared to the bare PSf membrane in dye solution filtration, 1% Fe-doped ZnS QDs membrane yielded twice as much flux and 15% higher FRR results. Therefore, the results proved that metal-doped QDs can be used in the modification of PSf membranes with high efficiency.

Sustainable Modification of Polyethersulfone Membrane with Poly(Maleic Anhydride-Co-Glycerol) as Novel Copolymer

This work presented an endeavour to fabricate sustainable and eco-friendly polyethersulfone (PES) ultrafiltration membranes. A novel and graft copolymer (Poly(Maleic Anhydride-Co-Glycerol)) (PMG) have been synthesized via a facile and rapid route to impart their hydrophilic features onto the final PES membrane. A series of characterization tools, for both nanoadditives and nanocomposite membranes, have been harnessed to confirm their successful fabrication processes. These include Fourier Transform Infrared Spectroscopy (FT-IR), scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), and contact angle measurements (CA). Results disclosed the successful synthesis of PMG nanoparticles that manifested a smooth homogenous surface with an average molecular size of 88.07 nm. The nanocomposite membrane structure has witnessed a gradual development upon each increment in the nanoparticle content ratio along with relatively thicker pore walls. The size and shape of figure-like micropores exhibited critical visible structural changes following the nanoadditive incorporation into the PES polymeric matrix. For the nanocomposite membrane, the SEM imaging indicated that a thicker active layer and less finger-like micropores were formed at higher PMG NP content within the membrane matrix. Hydrophilicity measurements disclosed a reversible correlation with the NP content where the CA angle value was at a minimum at the higher PMG loading content. Compared to the pristine membrane, a considerable enhancement in the performance of the modified membranes was witnessed. The membrane prepared using 2.5 g PMGNPs showcased six times higher pure water flux than neat PES membrane and maintained the highest retention (98%) against BSA protein solution. Additionally, the nanocomposite revealed promising antifouling and self-cleaning characteristics.

Application of polysaccharide-based metal organic framework membranes in separation science

Polysaccharide/MOF composite membranes have captured the interests of many researchers during decontamination of polluted environments. Their popularity can be attributed to the relatively high chemical and thermal stabilities of these composite membranes. Chitosan is among the polysaccharides extensively used during the synthesis of hybrid membranes with MOFs. The applications of chitosan/MOF composite membranes in separation science are explored in detail in this paper. Researchers have also synthesised mixed matrix membranes of MOFs with cellulose and cyclodextrin that have proved to be effective during separation of a variety of materials. The uses of cellulose/MOF and cyclodextrin/MOF membranes for the removal of environmental pollutants are discussed in this review. In addition, the challenges associated with the use of these mixed matrix membranes are explored in this current paper.