Unmodified Membrane Research Articles

Clarification of Apple Juice Using New Generation Nanocomposite Membranes Fabricated with TiO2 and Al2O3 Nanoparticles

To enhance anti-fouling properties of polymeric membranes during apple juice clarification, PSF/PEI (20/2 wt%) ultrafiltration (UF) membranes were modified with TiO2 and Al2O3 nanoparticles using the phase inversion method. Turbid apple juice samples were clarified using cross-flow membrane filtration system. All fabricated nanocomposite UF membranes had higher apple juice flux values than PSF/PEI membrane. Membrane prepared with 0.01% TiO2 (UFT1) had the highest apple juice flux (at steady state, 44.6 L/m2h). The FRR (%) value of TiO2 and Al2O3 incorporated UF membranes was between 90.9–94.0% and 79.6–97.6%, respectively, and these FRR values were higher than that of PSF/PEI membrane (UF2, 60.3%). Porosity and hydrophilicity of the UF membranes significantly increased with the addition of nanoparticles and the highest porosity and hydrophilicity was achieved in the 0.01% TiO2 incorporated UF membrane (UFT1) membrane. Higher flux recovery ratio (FRR) and lower relative flux reduction (RFR) values of Al2O3 and TiO2 incorporated nanocomposite membranes, compared with the unmodified membrane, demonstrated the enhancement in the anti-fouling properties of the PSF/PEI membrane. SEM images of the nanocomposite membranes also proved the nanoparticle incorporation to the PSF/PEI matrix. Color, turbidity, total soluble solid, total phenolic content, and antioxidant capacity of the samples using nanocomposite membranes were better than that of clarified using both commercial and unmodified membranes. TiO2 incorporated nanocomposite membranes had superior performance than Al2O3 incorporated nanocomposite membranes and among these membranes, the ones prepared with the addition of 0.01 wt% TiO2 exhibit the best performance in terms of clarification of apple juice.

Thermally stable core-shell star-shaped block copolymers for antifouling enhancement of water purification membranes

Star-shaped block copolymers (SPs), consisting of a hydrophobic core and hydrophilic arms, are a new material architecture introduced to the area of antifouling coatings for water filtration membranes. The unique self-assembly behavior of these SPs on hydrophobic membranes surface allows the formation of an ultrathin coating (less than 15 nm), rendering a highly hydrophilic antifouling membrane surface. Here, we have judiciously examined several important structural and process parameters, such as the chemical composition of SPs and surface properties (e.g., surface potential, coverage, and wettability) driven by a mono- or bi-layered assembly of SPs, to acquire a highly hydrophilic and thermally stable antifouling coating on a hydrophobic ultrafiltration (polysulfone, PSF) membrane for oil sands produced water treatment. Among three types of SPs (e.g., SP1 with 100% amine, SP2 with 55% amine/45% PEG, and SP3 with 35% carboxylic acid/65% PEG moieties in the arms) and their variable coating conditions, the bilayer coating comprised of SP3 top-layer and SP1 bottom-layer exhibited the best hydrophilicity and anti-oil fouling efficiency showing 2–4 times higher water flux compared to an unmodified PSF membrane during the filtration of synthetic oil-water emulsions conducted in both constant flux mode and constant pressure mode. Outstanding antifouling efficiency of the bilayer coating toward natural organic matters (NOMs) was also verified by using bovine serum albumin (BSA) and humic acid (HA) as the model foulants. The bilayer-coated membrane retained more than 80% and 90% (for nano and micron size oil emulsion, respectively) of its initial antifouling efficiency even after rigorous thermal treatment for an extended period (80 °C for 1 week), which demonstrates its feasibility for high-temperature membrane operation.

β-Cyclodextrin-based star polymers for membrane surface functionalization: Covalent grafting via “click” chemistry and enhancement of ultrafiltration properties

This work provides the proof-of-concept that surface functionalization of porous membranes with well-defined star-like polymers of varied number of arms and arm length leads to a tunable effective thickness of grafted layers and a specific influence on size-selective sieving through ultrafilter pores. Alkyl-brominated β-cyclodextrine with either 7 or 21 initiator sites per molecule was synthesized and further used for controlled atom transfer radical polymerization of copolymers of 2-dimethylamino(ethyl) methacrylate (DMAEMA) and propargyl methacrylate (PgMA), leading to star polymers with either 7 or 21 arms. Alkyne-containing PgMA segments enable the “click” coupling while DMAEMA segments provide the bulk of the polymer. Star polymers were characterized with respect to chemical structure and molecular weight (M). During ultrafiltration (UF) through cellulose membranes with different molecular weight cut-off, rejection was not simply correlated with star polymer M but was governed by macromolecular architecture, i.e. the smaller colloidal diameter for macromolecules of same M but 21 instead of 7 arms. Azide-functionalized poly(ethylene terephthalate) (PET) track-etched (TE) membranes and cellulose UF membranes were prepared by polymer-analogous surface functionalization so that the alkyne-substituted star polymers could be “click”-grafted. Isoporous PET TE membranes with a nominal pore diameter of 200 nm were used as model system to study the grafting and its effects onto pore size via the reduction of hydraulic permeability. Effective grafted layer thickness in the range of 10–50 nm correlated with macromolecular structure and architecture. For “click”-functionalized cellulose UF membranes, the effective pore size in the barrier layer was influenced by grafted star polymers, and a pronounced additional influence of the architecture and arm length of the grafted star polymer on macromolecular sieving was observed. Of particular interest are results with the more flexible 7-armed star polymers (compared to 21-armed counterparts); their grafting at the UF membrane pores of similar dimension leads to a large increase of test solute rejection at very low reduction of convective water flux, both compared to the unmodified membrane.

A facile coating to intact SAPO-34 membranes for wet CO2/CH4 mixture separation

The excellent performance of SAPO-34 membranes for CO2/CH4 separation is detracted by the water interaction, resulting in membrane instability and low durability. Herein, a new facile coating strategy using α, ω-dihydroxypolydimethylsiloxane (PDMS) has been developed for surface protection of SAPO-34 membranes by dip-coating. The fabrication of coating layer was optimized by finely tailoring the coating solution parameters, such as the viscosity and PDMS concentration. The developed membranes were evaluated under dry and wet CO2/CH4 mixture systems with effect of temperature and pressure. PDMS/SAPO-34 membrane could provide high separation performance in both systems. The separation selectivity of 68 and CO2 permeance of 1.41×10−7molm−2s−1Pa−1 was achieved for wet mixture of CO2/CH4 at 80°C during 120h continuous operation. Furthermore, the PDMS/SAPO-34 membrane showed a wonderful performance after half a year storage, with 5–8% changes of CO2 permeance and selectivity for the dry CO2/CH4 mixtures, while for un-modified SAPO-34 membrane, a decline of 71% in CO2 permeance and 85% in CO2/CH4 separation selectivity was observed. The results demonstrated that the PDMS-coated SAPO-34 membrane could be a promising candidate for natural gas purification.

Synthesis and characterization of nanocomposite ultrafiltration membrane (PSF/PVP/SiO2) and performance evaluation for the removal of amoxicillin from aqueous solutions

Abstract The presence of antibiotics in drinking water sources indicates the inefficiency of their removal using common water treatment process. Removal of these micro-pollutants from water requires more advanced and efficient processes. The purpose of this study was to synthesize a nanocomposite ultrafiltration membrane (Polysulfone/Polyvinylpyrrolidone/SiO2) and to evaluate for removal of amoxicillin from aqueous media. Ultrafiltration membranes were synthesized using phase inversion method. SiO2 nanoparticles ( ∼ 10-20 nm) were used in the range of 0 to 4 wt% as a hydrophilic agent for membrane modification. The characterizations of the membranes were determined using FTIR, water contact angle, AFM and SEM techniques. Also, the performance of synthesized membranes was evaluated in terms of pure water flux, amoxicillin separation efficiency and fouling parameters analysis. The results of FTIR analysis and contact angle measurement indicated that the hydrophilicity of nanocomposite membranes has increased significantly due to the presence of hydroxyl group in SiO 2 structure. The results of AFM images also showed that with increasing the addition of nanoparticles, the average surface roughness of the synthesized membranes increased negligibly. Also, FE-SEM micrographs showed that with increasing SiO2 concentration, the porous structure of the membranes changes from a spongiform and tear-like to a canal-shaped, finger-shaped and macro-void structures. This change in the structure increased the porosity and then the membrane flux, so that the pure water flux was 6.6 L/m2.h for the unmodified membrane to 42.28 L/m2.h for the membrane with 3 wt% of nanoparticles. The evaluation of membrane performance showed that with increasing SiO2 nanoparticles from 0 to 4 wt%, the amoxicillin separation performance increased from 66.52% to 89.81%. In addition, the analysis of the membrane fouling parameters showed that the addition of SiO2 nanoparticles also improved the membrane resistance against fouling, so that the relative flux reduction ratio (RFR) from 57.03% ( R r e v e r s i b l e r = 9 . 9 and R i r r e v e r s i b l e = 47 . 13 ) for the unmodified membrane reduce to 22.89% ( R r e v e r s i b l e r = 16 . 10 and R i r r e v e r s i b l e = 6 . 79 ) for the modified membrane with 3 wt% of nanoparticles. The results of this study showed that the use of nanocomposite membranes is promising for the removal of biodegradable resistant pollutants such as amoxicillin antibiotics from water resources.

Custom-Made Ion Exchange Membranes at Laboratory Scale for Reverse Electrodialysis.

Salinity gradient power is a renewable, non-intermittent, and neutral carbon energy source. Reverse electrodialysis is one of the most efficient and mature techniques that can harvest this energy from natural estuaries produced by the mixture of seawater and river water. For this, the development of cheap and suitable ion-exchange membranes is crucial for a harvest profitability energy from salinity gradients. In this work, both anion-exchange membrane and cation-exchange membrane based on poly(epichlorohydrin) and polyvinyl chloride, respectively, were synthesized at a laboratory scale (255 2) by way of a solvent evaporation technique. Anion-exchange membrane was surface modified with poly(ethylenimine) and glutaraldehyde, while cellulose acetate was used for the cation exchange membrane structural modification. Modified cation-exchange membrane showed an increase in surface hydrophilicity, ion transportation and permselectivity. Structural modification on the cation-exchange membrane was evidenced by scanning electron microscopy. For the modified anion exchange membrane, a decrease in swelling degree and an increase in both the ion exchange capacity and the fixed charge density suggests an improved performance over the unmodified membrane. Finally, the results obtained in both modified membranes suggest that an enhanced performance in blue energy generation can be expected from these membranes using the reverse electrodialysis technique.

Hydrogen permeation and chemical stability of Ni–BaCe0.7In0.2Ta0.1O3−δ cermet membrane

With its good mechanical strength, high hydrogen permeability, and low price, the dense metal ceramic hydrogen separation membrane has attracted increasing attention. The conductivity of perovskite–type proton conductors can be greatly improved by rare–earth doping. In this study, a new nickel/barium cerate cermet Ni–BaCe0.7In0.2Ta0.1O3–δ electron–proton mixed conducting membrane was prepared and its hydrogen permeability, proton conductivity, and chemical stability were tested. Hydrogen permeability was controlled by the bulk diffusion when the thickness was >0.8 mm, but controlled by both the surface exchange and the bulk diffusion when the thickness was <0.8 mm. Ni paste and Pt paste were coated on the surface of the membrane to a thickness of 0.6 mm. After surface modification with the Pt and Ni, the hydrogen permeability of the membrane surface was greatly improved compared with that of the unmodified membrane, owing to better hydrogen catalytic performance of Pt than Ni. Under different CO2 concentrations, the hydrogen penetration flux quickly decreased and then remained nearly stable. The degree of reduction increases with the carbon dioxide concentration increasing. When the CO2 was turned off, the hydrogen permeation rate was restored, and recyclability decreased with increasing CO2 concentration. The changes in phase composition and microtopography implied the reaction between the sample and the CO2. Therefore, these results showed that hydrogen permeability was further improved, not only by reducing the membrane thickness, but also by catalyzing the membrane surface.

Bio-inspired anchoring of amino-functionalized multi-wall carbon nanotubes (N-MWCNTs) onto PES membrane using polydopamine for oily wastewater treatment

The major problem that limits the utilization of PES membranes in treatment of oily wastewater is the drastic irreversible membrane fouling due to the attachment of oil droplets onto the membrane surface. The goal of this study was to develop a novel, fast and facile post-functionalization of polydopamine (PDA) coated membranes using pre-synthesized nanoparticles for fabrication of novel organic-inorganic hybrid recoverable membranes with high hydrophilicity and underwater oleophobicity. Here, bio-inspired technique was studied because the membrane technology could separate small oil droplets (even <10 µm) with high performance if faced little fouling phenomena during the treatment process.The amino-functionalized multi-wall carbon nanotubes (N-MWCNTs) were anchored onto the PDA coated PES membranes. The membranes characteristics, with specific focus on surface morphology and wettability were investigated. The newly developed PES/PDA/N-MWCNTs membranes showed an enhanced flux (~1086%) compared to the unmodified PES membrane. This enhancement was attributed to the high hydrophilic and underwater oleophobic properties, which were found to alleviate the effect of fouling. The total fouling ratio (Rt) of the PES/PDA/N-MWCNTs membrane was 22.35%, which was far lower than that of the unmodified PES membrane (98.38%). Meanwhile, most of the fouling was reversible for the former with the remaining (irreversible fouling) of 18.08%. It was concluded that cake filtration is the dominant fouling mechanism of the PES/PDA/N-MWCNTs membranes due to their average pore diameter. The modified membranes showed high oil rejection (>99%) so that the obtained clean water with oil concentration lower than 5 ppm met the wastewater discharge standard recommendations. Also, evaluation of the PES/PDA/N-MWCNT membrane in cross-flow filtration showed its antifouling properties in the long-term application (16 h).

Performance evaluation of modified nanohybrid membrane polyethersulfone-nano ZnO (PES-nano ZnO) using three combination effect of PVP, irradiation of ultraviolet and thermal for biodiesel purification

The main problems in biodiesel purification using membrane are low selectivity and fouling issue. Therefore, this research was developed on the modification polyethersulfone nanohybrid membranes which have excellent selectivity performance and anti-fouling behavior. The PES-nano ZnO nanohybrid membrane was fabricated by preparing dope solution composed of PES, nano ZnO and N-methyl Pyrrolidone as a solvent. UV irradiation, PVP addition, and thermal treatments were conducted to modify fabricated nanohybrid membranes. The modified membrane exhibited significant enhancement of hydrophilicity by lowering the water contact angle value from 66.17° to 52.33°. The initial flux of modified membrane increased up to 200% of the unmodified membrane’s initial flux. Both of modified and unmodified membranes have rejection more than 91% that can lowering the glycerol content from 3.98 to 0.34 wt-%. The modified membrane presented less foulant deposition on the membrane surface. This membrane also performed excellent stability in term of permeate flux and rejection efficiency. It is verified that the concept of modified PES-nano ZnO membrane can achieve a higher membrane performance for biodiesel purification such as increased of flux, lowering the glycerol content, better anti-fouling behavior and excellent stability.

An Effect of the Nature of Immobilized Components on the Adsorption and Mass Transfer Properties of Ultrafiltration Membranes Based on Sulfonate-containing Сopolyamide

Ultrafiltration membranes based on aromatic copolyamide, comprising 10% of units with sulfonate groups were produced. The possibility of their use as a matrix for the immobilization of ligands used in affinity chromatography: metal cations, amino acids, and dyes, is shown. The components of immobilization were copper(II) ions, histidine, lysine, and 3,6-diamino-10-methylacridine chloride. It was found that immobilization mainly occurs due to the electrostatic interaction of the corresponding functional groups of the component and copolyamide and is not accompanied by a decrease in the specific membrane productivity in water. The investigations of adsorption (under static conditions and ultrafiltration of protein solutions) were performed as well as mass transfer properties of modified membranes. The nature of the effect of the modification was revealed on the mass transfer characteristics of the obtained materials. For an unmodified membrane, the optimal combination of selectivity and specific productivity was realized at pH of the protein solution above its isoelectric point. Depending on the nature of the immobilized component, selectivity of 0.96–0.99 can be achieved at the pH below or equal to the isoelectric point of the protein.

Formulation and Evaluation of Novel Thiolated Intra Pocket Periodontal Composite Membrane of Doxycycline.

Localized intra-pocket, retentive, biodegradable, prolonged release thiolated membrane can provide an improved therapeutic efficacy of doxycycline at the site of action with evading off target side effects. To this end, thiolated chitosan-hyaluronic acid composite polymeric complex next-generation of the periodontal membrane was manufactured by solvent casting method. FTIR spectroscopic analysis displayed successful immobilization of thiol groups on the manufactured thiolated periodontal membrane. Moreover, XRD, DSC, AFM and TGA of the membrane confirmed the compatibility of ingredients and modifications in surface chemistry. The thiolated periodontal film was also investigated in terms of thickness, weight uniformity, water-uptake capacity, drug content, pH, entrapment efficiency, lysozymal degradation and release patterns. Also, mucoadhesion profile was explored on gingival mucosa. The immobilized thiol groups on thiolated chitosan and thiolated hyaluronate were found to be 168 ± 11μM/g (mean ± SD, n= 3) and 189 ± 8μM/g (mean ± SD, n = 3) respectively. Swelling capacity of the thiolated periodontal membrane was significantly ∼2-fold higher (p< 0.05) as compared to unmodified membrane. The obtained thiolated membrane depicted 3 -old higher mucoadhesive features as compared to the un-modified membrane. In vitro release kinetics indicated approximately more than 80% prolonged release within 7days. Mechanical strength of the Thiolated bandage was also significantly ∼2-fold higher (p < 0.05) as compared to unmodified membrane. Ex-vivo retention study revealed enhanced retention of thiolated membrane as compared to unmodified membrane. In-vitro antimicrobial studies demonstrated that thiolated membrane could efficiently kill Porphyromonas gingivalis cells as compared to the native membrane. Moreover, ex-vivo biodegradation results indicated that 90% of the thiolated membrane was biodegradable in 28days. Based on these findings, thiolated next-generation of the periodontal membrane seems to be promising for periodontitis therapy.

Enhanced transport and antifouling properties of polyethersulfone membranes modified with α-amylase incorporated in chitosan-based polymeric micelles

The objective of this study is related to the modification of polyethersulfone membranes with α-amylase incorporated into chitosan-based polymeric micelles in order to reduce the membrane fouling. Amphiphilic chitosan derivatives have been synthesized through grafting of palmitic (PA) and stearic (SA) acids onto low-molecular weight chitosan. CMC values of palmitoyl and stearoyl derivatives of chitosan are equal to 5.7·10−2 mg/mL and 3.9·10−2 mg/mL, respectively. Whereas, the size of polymeric micelles amounted to 707 ± 64 nm and 609 ± 57 nm for Chit-g-PA and Chit-g-SA, accordingly. The obtained micelles with enzyme have been adsorbed onto the surface of polyethersulfonic membranes. Modified membranes are characterized by high stability of the coating over time, thanks to the surface-active properties of chitosan derivatives and electrostatic interactions. The antifouling biocatalytic properties of modified membranes were studied in the process of starch filtration. The unmodified membrane showed the lowest permeability with an increase in the concentration of starch solutions due to dramatically increased cake formation. The permeability of modified membranes has been improved remarkably compared to the pristine one during starch ultrafiltration. The cake resistance of modified membranes decreases 6-fold, compared to the unmodified PES one. Furthermore, the effect of concentration polarization is attenuated owing to starch hydrolysis by α-amylase incorporated into polymeric micelles. The maximum activity of α-amylase immobilized on PES membrane is observed in the pH range of 6.5–7.5 and the higher resistance of enzyme to acidic media compared to the native one has been shown. High stability and reusability of immobilized α-amylase has been demonstrated. The degree of starch conversion reduces by 35% and 30% after 10 cycles for a membrane modified with Chit-g-PA and Chit-g-SA, respectively.

PVDF/Fe2O3 mixed matrix membrane for oily wastewater treatment

Oily wastewater has been recognized as one of the most concerned environmental pollutions that comes from a variety of sources. The increasing of these uncontrollable oily wastewater discharges had consequently led to environmental problems. The current barrier in this situation is when dealing with finely emulsified oily wastewater streams with small droplet size (< 20 μm in diameter). To tackle this issue, it was found that the utilization of the membrane technology was most effective due to its highly effective separation process and its simplicity. Nevertheless, traditional filtration membranes are mostly afflicted with low flux and rejection rate as a consequence of easy fouling caused by the plugging of oil and surfactant. Thus, the wettability and antifouling properties of the membrane play an important role in dealing with this issue. The aim of this study is to evaluate the performance and operation of the membrane when treating oily wastewater. PVDF was chosen as the host polymer based on its outstanding properties and 0.2 wt% of Fe 2 O 3 loading was utilized to enhance the hydrophilicity of the membrane. The effect of mixed matrix membrane (MMM) and neat poly(vinylidene fluoride) (PVDF) membrane relating to their differences in the SEM images, water flux and oil rejection was studied. The presence of additive in the polymeric composition has helped to achieve 40 % higher flux increment with an oil removal efficacy of ~97 %, as compared to the unmodified PVDF membrane.

Improvement of performance and fouling resistance of polyamide reverse osmosis membranes using acrylamide and TiO2 nanoparticles under UV irradiation for water desalination

ABSTRACTThe purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV‐initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results demonstrated the enhanced hydrophilicity of modified membranes and confirmed the presence of acrylamide and nanoparticles on the membranes surface. Acrylamide‐grafted membranes could reach to higher water flux than pristine membrane with little reduction in salt rejection. Moreover, TiO2‐coated membranes indicated enhancement of water flux continuously with increase in nanoparticles concentration and irradiation time and rejection of membranes was slightly decreased at low irradiation times. Also, RO membranes modified simultaneously with acrylamide and TiO2 nanoparticles under UV irradiation exhibited improved water flux up to 18%, slightly higher rejection, and considerable better fouling resistance compared with pristine one. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48461.RESEARCH HIGHLIGHTS Aromatic polyamide thin film composite reverse osmosis (RO) membranes fabricated through interfacial polymerization process between m‐phenylenediamine and trimesoyl chloride on the porous polysulfone support. The desirable UV irradiation time for surface modification of RO membranes was up to 90 s. Modification of RO membranes surface was carried out by UV‐initiated grafting of acrylamide, coating of membranes surface with TiO2 nanoparticles followed by the UV irradiation, and grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. ATR‐FTIR, SEM, EDX, and AFM confirmed modification of membranes surface with acrylamide, TiO2 nanoparticles, and both of them. All modified membranes had lower contact angle than unmodified one indicating enhanced surface hydrophilicity. Acrylamide‐grafted membranes could result in higher water flux than unmodified membrane with little reduction in salt rejection. TiO2‐coated membranes indicated improvement of water flux with increase in nanoparticles concentration and irradiation time and rejection of membranes was decreased slightly at low UV irradiation times. RO membranes modified simultaneously with acrylamide and TiO2 nanoparticles under UV irradiation had improved water flux, slightly higher rejection, and considerable enhanced antifouling property compared with unmodified one.

Surface modification of polysulfone ultrafiltration membranes by free radical graft polymerization of acrylic acid using response surface methodology

In this research, polysulfone (PSf) ultrafiltration (UF) membranes were prepared by a phase inversion method. Surface modification of the PSf membranes was carried out via grafting of acrylic acid as a hydrophilic monomer by free radical graft polymerization initiated by redox reaction. A central composite design (CCD) of response surface methodology (RSM) was applied to design the experiments. The process variables were acrylic acid concentration (CAA), redox system contact time (T1), and acrylic acid polymerization time (T2), while the contact angle (CA), pure water flux (PWF), and flux recovery ratio (FRR) were considered as the responses. Analysis of variance (ANOVA) demonstrated that the second-order polynomial models were appropriate and significant. The optimal conditions for variables was found to be CAA of 1.6 mol/L, T1 of 41.9 min, and T2 of 101.7 min. The predicted responses were 52.9° for CA, 149 L/m2 h for PWF, and 74.5% for FRR, which were in good agreement with the results obtained from the confirmation experiments, with values of about 53.2°, 145.3 L/m2 h, and 74.3%, respectively. A comparison of the results between the optimized and unmodified membranes indicated that the CA of the modified membrane was reduced significantly, about 30.5%, and FRR was increased considerably, about 32.2%, indicating that the modified membranes possessed enhanced fouling resistance, while the PWF declined 40%. Membrane characterization also revealed that acrylic acid was grafted uniformly on the membrane surface, and the modified membranes became smoother, as observed by SEM and AFM. Moreover, the pore size of the modified membranes as measured by MWCO was smaller than that of the unmodified membrane.

Ferrous sulfide and carboxyl-functionalized ferroferric oxide incorporated PVDF-based nanocomposite membranes for simultaneous removal of highly toxic heavy-metal ions from industrial ground water

The deterioration of the aquatic environment by the heavy metal ions contamination causes serious threat to environment and human beings. However, the treatment of complex industrial wastewater by simultaneous removal of multiple heavy metal ions via a one-step method is still extremely challenging. To this end, we synthesize ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide (CFFO) nanoparticles, which were introduced into polyvinylidene fluoride (PVDF) matrix (individually/mixed together in an optimum ratio) through phase inversion technique. Three types of mixed matrix membranes (MMMs) were developed, viz. FeS/PVDF, CFFO/PVDF and FeS/CFFO/PVDF. The prepared membranes were characterized by SEM, TEM, AFM, FTIR, XRD, BET, and XPS techniques. The properties of the membranes were also examined for pure water flux, hydrophilicity, water uptake capacity, mechanical and thermal property, salt separation and simultaneous separation of toxic heavy metal ions such as lead, (Pb), cadmium (Cd), and chromium (Cr) from industrial ground water. The resultant membranes exhibited relatively high water flux (340–1266 L/m2h) than the unmodified PVDF membrane, due to changes in the porosity and hydrophilicity of the membranes. FeS/CFFO/PVDF membrane showed that it could effectively treat Pb, Cd, Cr and As contaminated industrial ground water, simultaneously with a high removal efficiency of about 88% for Cr(VI), 99% for Cd2+, 99% for Pb2+ and 95% for As in a single filtration process. In addition, the developed membranes conspicuously reduce their concentrations below the maximum contaminant level of WHO and BIS (India). The probable mechanism of separation of heavy metal ions through MMMs could be understood through FTIR and XPS techniques. The results of this study inferred that FeS/CFFO/PVDF membrane is a potential candidate for the simultaneous separation of Pb, Cd, Cr, and As.

Robust Polymer Nanocomposite Membranes Incorporating Discrete TiO2 Nanotubes for Water Treatment.

Polyethersulfone (PES) is a polymeric permeable material used in ultrafiltration (UF) membranes due to its high thermomechanical and chemical stability. The hydrophobic nature of PES membranes renders them prone to fouling and restricts the practical applications of PES in the fabrication of water treatment membranes. The present study demonstrates a non-solvent-induced phase separation (NIPS) approach to modifying PES membranes with different concentrations of discrete TiO2 nanotubes (TNTs). Zeta potential and contact angle measurements showed enhanced hydrophilicity and surface negative charge in TNTs/PES nanocomposite membranes compared to unmodified PES membranes. To discern the antifouling and permeation properties of the TNTs/PES membranes, steam assisted gravity drainage (SAGD) wastewater obtained from the Athabasca oil sands of Alberta was used. The TiO2 modified polymer nanocomposite membranes resulted in a higher organic matter rejection and water flux than the unmodified PES membrane. The addition of discrete TNTs at 1 wt% afforded maximum water flux (82 L/m2 h at 40 psi), organic matter rejection (53.9%), and antifouling properties (29% improvement in comparison to pristine PES membrane). An enhancement in fouling resistance of TNTs/PES nanocomposite membranes was observed in flux recovery ratio experiments.

Modification of regenerated cellulose membrane by impregnation of silver nanocrystal clusters

ABSTRACTRegenerated cellulose forms a very important class of basic material with diverse applications because of its hydrophilicity and insolubility in water. Thus, one of the applications of regenerated cellulose is used to fabricate membranes. However, short operational lifetime is one of the disadvantages of the regenerated cellulose. In this research, surface modification of the cellophane membrane was carried out by silver nanoclusters. Silver colloids were formed in situ by chemical and photochemical reduction, and then, silver particles were deposited uniformly onto the surface of the cellophane membrane. The maximum amount of silver deposition was found to be 2.55% by weight in this modification. The modified and unmodified membranes were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy‐dispersive X‐ray analysis to indicate silver nanocrystalline cluster particles on the modified membrane. SEM images indicate well‐dispersed silver particles with an average size of 0.65 μm on the membrane. XRD patterns showed that the size of the silver crystals was 3.9 nm. The surface properties of modified and unmodified membranes were studied by the contact angle. Water absorption, oxidative resistance, salt permeability, and thermal stability were investigated. This study revealed that the modified membrane is more resistant against the oxidative cleavage than the unmodified one moreover, the salt permeability increased after the treatment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48292.

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.

MODIFICATION OF TUBULAR CERAMIC MEMBRANES BY PYROCARBON FROM CARBONIZED POLYMERS

The tubular ceramic membranes of clay minerals were modified with pyrocarbon, which was obtained by carbonizing of polymer precursors at 750 ° С in an argon flow. The precursor to carbonization of membrane II was polyurethane, obtained from laprol and polyisocyanate. A precursor to carbonization of the membrane III was a mixture of polymers formed by the reaction of components of an aqueous solution of a dry solution with NCO-groups of polyisocyanate. As a result of the modification, the membranes became black with a metallic luster. The composition and structure of the membranes were studied by XRF and SEM. The modifier of the membrane II is located in the pore space in the form of sintered agglomerates. The modifier of the membrane III is represented not only by the same agglomerates, but also envelops the structural elements of the membrane material. The apparent density and open porosity for the unmodified membrane are 1.80 g/cm3 and 44.9 %, for membrane II - 1.67 g/cm3 and 39.9 %, for membrane III - 1.68 g/cm3 and 38.3 %. Testing of modified membranes was carried out by water purification from Ca2 + and Fe3 + using the baromembrane method. The concentration of Ca2 + and Fe3 + in aqueous solutions of CaCl2 and FeCl3 was 100 mg/dm3. The period of time until the establishment of dynamic equilibrium in systems during water purification is (1–3 h). After reaching equilibrium the retention factor (R) of Ca2 + during water purification with membrane II is 30% at a pressure of 0.6 MPa, and at a pressure of 1.1 MPa – 18 %. The specific productivity increases with increasing pressure from 10 to 18 dm3/(m2×h). The R of Ca2 + in water purification with membrane III is 22 % at a pressure of 0.4 MPa, and the specific productivity is 47 dm3/(m2×h). The unmodified membrane does not inhibit Ca2 + at all, and its specific productivity at a working pressure of 0.7 MPa decreases from 755 to 500 dm3/(m2×h) in 2-3 hours. The coefficient of retention of Fe3 + by membrane III after 5 hours at a working pressure of 0.4 MPa is 98 % The specific productivity in this case is 8 dm3/(m2×h).