Magnetic field induced orderly arrangement of Fe3O4/GO composite particles for preparation of Fe3O4/GO/PVDF membrane

Fabrication of nanocomposite membranes containing Ag/GO nanohybrid for phycocyanin concentration

In this research, silver/graphene oxide (Ag/GO) nanohybrid was first synthesized and used in production of polysulfone (PSF) ultrafiltration (UF) membranes via phase inversion method for concentrating phycocyanin (PC) and treating methylene blue (MB) dye effluent. Designing the experiment (DOE) using Box-Behnken method by Design Expert software helped to calculate the optimal values of the variables under study. The studied variables included PSF polymer concentration, polyvinyl pyrrolidone (PVP) pore-former concentration and Ag/GO nanohybrid content, which were investigated for their effects on pure water flux (PWF) and MB pigment rejection. According to the results of the DOE, the membrane containing 19.485 wt% PSF, 0.043 wt% PVP and 0.987 wt% Ag/GO was selected as the optimal membrane. Due to the high price of PC as drug, and the importance of removing MB pigment from the effluent of dyeing and textile industries, the membranes were first optimized with MB pigment and then the optimal membrane was used for concentrating PC. The results showed that PWF reaches from 40.05 L.m- 2.h- 1 (LMH) for the neat membrane to 156.73 LMH for the optimized membrane, which shows about 4 times improvement. Compared to the neat membrane, flux recovery ratio (FRR) of the optimized membrane increased by about 20% and its total fouling (Rt) decreased by about 10%. Also, the results showed that the optimized membrane can remove 81.6% of MB, as well as to reject 93.8% of PC.

Effect of chitosan crosslinking time on the structure and antifouling performance of polyvinylidene fluoride membrane by surface gelation-immersion precipitation phase inversion

Polyvinylidene fluoride (PVDF) porous membrane was prepared by a two-step method of surface gelation-immersion precipitation phase inversion. Chitosan/acetic acid solution and glutaraldehyde aqueous solution were sequentially sprayed onto the surface of the PVDF solution film, with chitosan crosslinking and gelation occurring simultaneously on the film surface. The solution film was then immersed in a coagulation bath to obtain a modified PVDF porous membrane. The effect of the crosslinking time of chitosan and glutaraldehyde on the structure and properties of the PVDF porous membrane was discussed. The results showed that with the prolongation of crosslinking time, the surface structure of the membrane changed from a dense skin layer to a porous structure; the porosity and the mean pore size of the modified PVDF membranes increased first and then decreased, and the contact angle gradually decreased. When the crosslinking time extended to 15 min, the water flux of modified membrane (M153) reached a maximum value. BSA dynamic cyclic filtration experiment showed that the retention rate (R) of the modified membrane was significantly improved, compared to 68.3% retention rate of the blank membrane (M000), but the crosslinking time had little effect on the retention rates of the four modified membranes. The antifouling data showed that the flux recovery rate of the blank membrane was 73.0%, while the flux recovery rate of the modified membrane can reach as high as 84.40%, and the irreversible pollution rate of the blank membrane was 27.7%, while the irreversible pollution rate of the modified membrane reduced to 15.6%. These results indicated that, after surface chitosan crosslinking, the hydrophilicity and antifouling properties of PVDF membranes were improved. PRACTITIONER POINTS: Modified PVDF membranes with crosslinking CS coating were prepared by a two-step method of surface gelation-immersion precipitation phase inversion. -OH groups and -NH2 groups of CS coating improve the hydrophilicity and the antifouling property of modified PVDF membranes. Modified PVDF membranes had larger mean pore size and higher porosity than unmodified membrane. Flux recovery rates of the modified membranes were higher than that of unmodified membrane. Pollution degree, reversible pollution rate, and irreversible pollution rate of modified membranes were lower than those of unmodified membrane.

Facile Preparation of PVDF/CoFe2O4-ZnO Hybrid Membranes for Water Depollution

In this investigation, CoFe2O4-PVDF and CoFe2O4-ZnO-PVDF hybrid membranes were prepared using a modified phase inversion method in which a magnetic field was applied during the casting process to ensure a uniform distribution of nanomaterials on the membrane surface. Thus, better absorption of light and increased participation of nanoparticles in the photodegradation process is ensured. The influence of nanomaterials on the crystalline structure, surface morphology, and hydrophilicity properties of the PVDF membrane was investigated. The obtained results indicated that the hybrid membrane exhibited significant differences in its intrinsic properties due to the nanomaterials addition. The hydrophilicity properties of the PVDF membrane were improved by the presence of nanoparticles. The photocatalytic decomposition of aqueous Rhodamine B solution in the presence of the prepared membrane and under visible light irradiation was tested. The hybrid membrane containing CoFe2O4-ZnO on its surface exhibited a high removal rate.

Effect of spraying polyvinyl alcohol solution on the surface of liquid film on the structure and antifouling properties of polyvinylidene membrane

Polyvinylidene fluoride (PVDF) membrane was prepared by a two-step method of surface gelation-immersion precipitation. The surface of the scraping solution film was sprayed with polyvinyl alcohol (PVA) aqueous solution to gel the film surface first, and then the liquid film was immersed in a coagulation bath for phase transformation to obtain the surface modified PVDF membrane. The effects of PVA solution with different mass fraction on the structure and properties of PVDF membrane were studied. The results showed that with the increase of spraying PVA mass fraction, the contact angle of the upper surface of PVDF membranes gradually decreased, the porosity and mean pore size of PVDF membranes gradually increased, and the crystallinity of PVDF membranes gradually decreased. The pores on upper surface of the membranes first increased and then decreased, and the finger-like macropore structure appeared inside the membranes, the water flux first increased and then decreased, and the rejection rate increased. Dynamic cycle filtration experiment of bovine serum protein (BSA) solution showed an increase in membrane flux recovery from 68.31 to 95.08% and a decrease in the irreversible fouling rate from 31.69 to 4.92%, indicating an improvement in the hydrophilicity and antifouling properties of the modified PVDF membrane.

Next-generation graphene oxide additives composite membranes for emerging organic micropollutants removal: Separation, adsorption and degradation

In the past two decades, membrane technology has attracted considerable interest as a viable and promising method for water purification. Emerging organic micropollutants (EOMPs) in wastewater have trace, persistent, highly variable quantities and types, develop hazardous intermediates and are diffusible. These primary issues affect EOMPs polluted wastewater on an industrial scale differently than in a lab, challenging membranes-based EOMP removal. Graphene oxide (GO) promises state-of-the-art membrane synthesis technologies and use in EOMPs removal systems due to its superior physicochemical, mechanical, and electrical qualities and high oxygen content. This critical review highlights the recent advancements in the synthesis of next-generation GO membranes with diverse membrane substrates such as ceramic, polyethersulfone (PES), and polyvinylidene fluoride (PVDF). The EOMPs removal efficiencies of GO membranes in filtration, adsorption (incorporated with metal, nanomaterial in biodegradable polymer and biomimetic membranes), and degradation (in catalytic, photo-Fenton, photocatalytic and electrocatalytic membranes) and corresponding removal mechanisms of different EOMPs are also depicted. GO-assisted water treatment strategies were further assessed by various influencing factors, including applied water flow mode and membrane properties (e.g., permeability, hydrophily, mechanical stability, and fouling). GO additive membranes showed better permeability, hydrophilicity, high water flux, and fouling resistance than pristine membranes. Likewise, degradation combined with filtration is two times more effective than alone, while crossflow mode improves the photocatalytic degradation performance of the system. GO integration in polymer membranes enhances their stability, facilitates photocatalytic processes, and gravity-driven GO membranes enable filtration of pollutants at low pressure, making membrane filtration more inexpensive. However, simultaneous removal of multiple contaminants with contrasting characteristics and variable efficiencies in different systems demands further optimization in GO-mediated membranes. This review concludes with identifying future critical research directions to promote research for determining the GO-assisted OMPs removal membrane technology nexus and maximizing this technique for industrial application.

Highly efficient recovery of heavy rare earth elements by using an amino-functionalized magnetic graphene oxide with acid and base resistance

In the application of various magnetic materials for water treatment, control of surface resistance to acid and alkali corrosion remains largely overlooked, which could greatly extend their service life. We herein prepare amino grafted magnetic graphene oxide composites using a simple one-step cross-link reaction between the graphene oxide and magnetic Fe₃O₄/C nanoparticles. The as-prepared magnetic graphene oxide composites have long-term stability under acid and alkali solutions and shows an excellent performance in removing Ho(III), a representative rare earth element (REE) from water. The observed adsorption capacity of 72.1 mg Ho(III)/g exceeded that of most magnetic materials previously reported. Regeneration of the magnetic composites was realized in acid and alkali solutions but their structural integrity and physicochemical properties retained even after 18 adsorption-desorption cycles. The current adsorbent also shows excellent adsorption performance for other heavy REEs, such as Er(III), Eu(III), Lu(III), Tm(III), Y(III) and Yb(III). This work can provide a new strategy for constructing an acid and base resistance magnetic graphene oxide for the high-efficient recovery of heavy REEs from aqueous solution.

Magnetic field-influenced nanofiltration membrane blended by CS-EDTA-mGO as multi-functionality green modifier to enhance nanofiltration performance, efficient removal of Na2SO4/Pb2+/RR195 and cyclic wastewater treatment

Magnetic field-influenced nanofiltration membrane by blending of magnetic multi-functionality green modifier (CS-EDTA-mGO) was fabricated via phase inversion processes. Migration of superparamagnetic nanofiller particles into top surface layer of M6 NF-membrane by incorporating external magnetic-filed during casting phase improved the hydrophilicity, as well as formation of large pores diameters (1.57 nm) which offer a flux enhancement (84.2 kg/m²h), excellent fouling resistance (R_r of 26.4%, R_t of 39.4% and R_ir of 25.0%) and highest flux recovery ratio (75.9%). The order of salt rejection for all modified NF-membranes was Na₂SO₄ > MgSO₄ > NaCl and the efficiency of the membranes to reject salts follows the order of M6 > M4 > M0. The performance of M6 as magnetic field-influenced membrane in rejection of RR195 and MB was 21% and 42% higher than unblended membrane (M0), respectively. The highest removal efficiency of Pb²⁺ and Cd²⁺ observed for M6 (98.2% and 93.6%, respectively). M6 was more efficient in concurrent removing pollutants from mixed-solute feed. In this case, the existing of Na₂SO₄ enhanced the retention of RR195 from 97.2% to 99.3%. Long-term operation tests demonstrated the excellent stability of M6 for 18 h filtration with a limited reduction in rejection and water flux of single salt solution. M6 membrane has found potential application in cyclic textile wastewater treatment which the water flux was found to be constant over 3-repeated filtration cycles.

Magnetic MBR technology: from the fabrication of membrane to application in wastewater treatment

The aim of this study is to synthesize a magnetic nanocomposite membrane using iron oxide and alumina nanoparticles and employing it in magnetic membrane bioreactors (MBRs) for oily wastewater treatment. Al₂O₃ and Fe₃O₄ nanoparticles with approximate sizes of 20 and 30 nm respectively, were settled into a polysulfone (PSf) membrane matrix via magnetic casting method. The concentration of alumina and iron oxide nanoparticles were 0-0.25 wt% and 0.03 wt%, respectively. Compared with the blank membrane, an increase in the concentration of Fe₃O₄ up to 0.2 wt%, led to the flux as much as 70% and mitigated total resistance by 70%. The presence of the magnetic field around the bioreactor increased the flux significantly and reduced the cake resistance by 93%. Moreover, by applying the static magnetic field to MBR, the Chemical Oxygen Demand (COD) removal rate was increased to 93%, while in the MBR without the magnetic field the COD removal rate was 80%. Our investigation illustrated that the magnetic casting is an effective method to improve the flux and mitigate the fouling of the magnetic nanocomposite membrane. The output of this research indicates that the magnetic casting method enhance the magnetic MBRs performance for wastewater treatment.

Preparation of magnetized iron oxide grafted on graphene oxide for hyperthermia application

Magnetic hyperthermia therapy (MHT) is a highly promising therapeutic modality for the treatment of different kinds of cancers and malignant tumors. The therapy is based on the concept that; iron oxide nanoparticles deposited at cancer sites can generate heat when exposed to an alternating current magnetic field or near infrared radiation and consequently destroying only the cancer cells by exploiting their vulnerability to heat. The fact that the treatment is at molecular level and that iron oxide nanoparticles provide more guided focus heating justifies its efficacy over treatment such as surgery, radiation therapy and chemotherapy. Nevertheless, the spread of MHT as the next-generation therapeutics has been shadowed by insufficient heating especially at the in vivo stage. This can be averted by modifying the iron oxide nanoparticle structure. To this end, various attempts have been made by developing a magnetic hybrid nanostructure capable of generating efficient heat. However, the synthesis method for each component (of the magnetic hybrid nanostructure) and the grafting process is now an issue. This has a direct effect on the performance of the magnetic hybrid nanostructure in MHT and other applications. The main objective of this review is to detail out the different materials, methods and characterization techniques that have been used so far in developing magnetic hybrid nanostructure. In view of this, we conducted a comprehensive review and present a road map for developing a magnetic hybrid nanostructure that is capable of generating optimum heat during MHT. We further summarize the various characterization techniques and necessary parameters to study in validating the efficiency of the magnetic hybrid nanostructure. Hopefully, this contribution will serve as a guide to researchers that are willing to evaluate the properties of their magnetic hybrid nanostructure.

A novel polyethersulfone/modified activated carbon fiber composite membrane: potential for removal micropollutants from water under the electric field

This study aimed to develop a novel composite membrane based on polyethersulfone (PES) and modified activated carbon fibers (ACFs) to remove of sulfamethoxazole (SMZ) from water. The modification of ACFs was conducted by using acid, Fe, and Mn and was confirmed by Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), and water contact angle measurement. Later on, the composite membranes were prepared using PES (9 wt%), N-N-dimethylacetamide (DMAc) (75 wt%), polyethylene pyrrolidone (PVP) (5 wt%), anhydrous lithium chloride (LiCl) (1 wt%), and various types of modified ACFs (0.8 wt%) as additives. It was found that the contact angle of the membrane decreased by more than 20°, and the zeta potential decreased by more than 10 mV. ACF modified by Fe was used as an admixture, membrane obtained the high comprehensive performance. Especially bovine serum albumin (BSA) rejection rate and flux recovery ratio (FRR) reached 98.8% and 98.4%, respectively. And the removal rates of SMZ increased by 24.6% under the electric field. The degradation products were detected by high-performance liquid chromatography/mass spectrometry (HPLC/MS). Based on this result, the possible degradation pathways of SMZ are proposed.

2D Nanocomposite Membranes: Water Purification and Fouling Mitigation

In this study, the characteristics of different types of nanosheet membranes were reviewed in order to determine which possessed the optimum propensity for antifouling during water purification. Despite the tremendous amount of attention that nanosheets have received in recent years, their use to render membranes that are resistant to fouling has seldom been investigated. This work is the first to summarize the abilities of nanosheet membranes to alleviate the effect of organic and inorganic foulants during water treatment. In contrast to other publications, single nanosheets, or in combination with other nanomaterials, were considered to be nanostructures. Herein, a broad range of materials beyond graphene-based nanomaterials is discussed. The types of nanohybrid membranes considered in the present work include conventional mixed matrix membranes, stacked membranes, and thin-film nanocomposite membranes. These membranes combine the benefits of both inorganic and organic materials, and their respective drawbacks are addressed herein. The antifouling strategies of nanohybrid membranes were divided into passive and active categories. Nanosheets were employed in order to induce fouling resistance via increased hydrophilicity and photocatalysis. The antifouling properties that are displayed by two-dimensional (2D) nanocomposite membranes also are examined.

Multifunctional Core-Shell Zwitterionic Nanoparticles To Build Robust, Stable Antifouling Membranes via Magnetic-Controlled Surface Segregation

Novel multifunctional core-shell nanoparticles (Fe₃O₄@PSBMA NPs) with magnetic and zwitterionic properties were first synthesized and efficiently incorporated into the poly(vinylidene fluoride) (PVDF) membranes via magnetically controlled surface segregation toward the better water-energy-food nexus. The combination of zwitterionic polymers poly(sulfobetaine methacrylate) (PSBMA) and Fe₃O₄ particles can improve the compatibility of additives with the PVDF matrix and significantly improve the migration of Fe₃O₄@PSBMA NPs onto membrane surfaces under magnetic fields during nonsolvent-induced phase separations. The modified membrane with surface-enriched multifunctional zwitterionic NPs had an enhanced water flux (168%, ∼630.5 L m^-2 h^-1), excellent fouling resistance (∼93.8%), and increased rejection to bovine serum albumin (94.1%). Most importantly, the PVDF/M-Fe₃O₄@PSBMA membrane had excellent stability under the long-term filtration test for practical water-treatment applications.