Cellulose Acetate Ultrafiltration Membranes Research Articles

Novel ethylenediamine-β-cyclodextrin grafted membranes for the chiral separation of mandelic acid and its derivatives.

In the present study, flat cellulose acetate ultrafiltration membranes were prepared first by nonsolvent induced phase separation method. Then chiral membranes for separating the enantiomers were prepared by grafting the ultrafiltration membranes using ethylenediamine-β-cyclodextrin as the chiral selector and epichlorohydrin as the spacer arm. The pure water permeability of the ultrafiltration membrane was around 115 L·m-2·h-1·bar-1. The properties of the chiral membranes were characterized using infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The chiral membrane performance in enantiomer separation was evaluated with racemates, such as mandelic acid (MA), 2-chloromandelic acid (2-ClMA), 4-chloromandelic acid (4-ClMA), and methyl mandelate (MM). The influence of feed concentration on the separation efficiency was also investigated. The results indicated that the enantiomeric excess percentages (e.e%) of the racemic mixtures for these four chiral compounds were up to 31.8%, 25.4%, 17.8%, and 32.6%, respectively. The binding free energy of the chiral selector with the (S)-enantiomer calculated by molecular dynamics simulations was stronger than that with the (R)-enantiomer, which was consistent with the experimental results (higher concentration of (R)-enantiomer in the permeate). This supports the affinity absorption-separation mechanism.

Separation of oil-water emulsion by cellulose acetate ultrafiltration membranes

ABSTRACT This study reports the separation of oil from water using cellulose acetate (CA) ultrafiltration (UF) membranes. The CA membranes were fabricated by varying bath temperatures such as 5 ± 2°C, 25 ± 2°C and 45 ± 2°C using the phase inversion technique and assess their performance based on the oil removal efficiency. Changing the coagulation bath temperature (CBT) at that stage of membrane formations affects the porosity, pore size, hydraulic resistance, morphological structure and performance of membranes. The obtained results revealed increased porosity and pore size and also decreased hydraulic resistance of the membranes as the CBT increases. Field Emission Scanning Electron Microscopy (FESEM) images indicate that a large number of surface pores are visibly found at the higher bath temperature. Atomic force Microscopy (AFM) images show increased average roughness (R a) of the membrane as the CBT of the membrane increases. The water flux and permeate flux of all the membranes tend to increase with an increase in CBT. From Chemical Oxygen Demand (COD) studies, the oil removal efficiency was maximum for the lower bath temperature membrane. The results indicate that conditions of the coagulation bath significantly affect the porous structure, morphology and performance of the membrane.

Fabrication and characterization of cellulose acetate ultrafiltration membrane and its application for efficient bovine serum albumin separation

AbstractTo solve the easy contamination problem of ultrafiltration membranes during protein separation, a series of cellulose acetate (CA) ultrafiltration membranes with different pore morphology and structure were successfully prepared by combining solution casting, non‐solvent‐induced phase inversion, and pore‐forming agent leached out technologies. The effects of molecule weight and the content of porogen polyethylene glycol (PEG) on the pore morphology, chemical composition, and wettability of the CA ultrafiltration membrane were systematically studied. The feed permeability, bovine serum albumin rejection, and anti‐fouling ability were also investigated. The results showed that the CA10k membrane has the highest pure water flux of 877.5 L/m2h.bar, largest bovine serum albumin (BSA) rejection of 96.5% and flux recovery rate of 90.9% when the PEG molecule weight and content are 10 kDa and 10 wt%. Those results showed that the CA ultrafiltration membranes have great application prospects in the BSA separation area.

Enhanced permeability of cellulose acetate ultrafiltration membrane by incorporation of cellulose graft copolymer

Enhanced permeability of cellulose acetate ultrafiltration membrane by incorporation of cellulose graft copolymer

Ti2AlN MAX phase as a modifier of cellulose acetate membrane for improving antifouling and permeability properties

The development of novel materials for the modification of filtration membranes is necessary to enhance their performance. In this study, the application of MAX phase-based material in the modification of cellulose acetate (CA) ultrafiltration membrane is reported to improve hydrophilicity, permeability, dye rejection and antifouling properties. Firstly, the Ti2AlN MAX phase was synthesized and exfoliated under ultrasonic to obtain nanosheets with an average width of 35 nm. Then, the influence of the prepared MAX phase on the CA membrane performance was assessed by blending different concentrations of it (0–1 wt%). The flux of pure water and bovine serum albumin protein solution was improved 27.5 % and 37.5 % by blending 0.5 wt% of the MAX phase into the matrix of the membrane. Moreover, the 0.5 wt% MAX/CA nanocomposite membrane represented ameliorated antifouling property with a flux recovery ratio of 86.3 %. This study showed that the MAX phase could be considered propitious additives to modify polymeric membrane performance.

TEMPO-mediated oxidation as surface modification for cellulosic ultrafiltration membranes: Enhancement of ion rejection and permeability

In membrane technology, rejection of dissolved salts often requires the use of nanofiltration or reverse osmosis membranes due to their sufficiently dense structure and favourable charge effects. In this work, the concept of charge-based salt rejection is extended to the more open ultrafiltration class. Surface charge of a commercial regenerated cellulose acetate ultrafiltration membrane is enhanced with TEMPO-mediated oxidation. With the modification, a membrane whose properties lie between the traditional nanofiltration and ultrafiltration classes is obtained. Moreover, a purely charge-based salt rejection mechanism is introduced to an ultrafiltration membrane.Increasing hypochlorite exposures are found to induce successively increasing surface carboxylate densities, negative zeta potentials, permeabilities and molecular weight cut-off values. In the low exposure region, the treatment mostly affects surface charge, whereas high exposures begin to open the membrane pores. Ultimately, the pH 7 zeta potential is increased from −30 up to −100 mV, and 500 ppm Na2SO4 rejections increase from an initial 4% to 36%. At the same time, pure water permeability is doubled, and cut-off value increased from 2.8 to 8.0 kDa. The reactions causing the change in membrane performance seem to take place almost exclusively on the membrane surface, while the bulk material appears unchanged.

2‐(N‐3‐Sulfopropyl‐N,N‐dimethyl ammonium)ethyl methacrylate modified graphene oxide embedded into cellulose acetate ultrafiltration membranes for improved performance

AbstractN‐(3‐sulfopropyl)‐N‐(methacryloxyethyl)‐N,N‐dimethylammonium betaine (SBMA) modified graphene oxide composite used as a filler in the fabrication of a nanocomposite cellulose acetate membrane was grafted through reverse atom transfer radical polymerization (RATRP) technique from a GO‐Br precursor. All the prepared materials (GO, GO‐Br, PSBMA@GO) were characterized using a combination of FTIR, BET, TEM, TGA, RAMAN, and XRD. The effect of different GO and PSBMA@GO contents on cellulose acetate membranes was investigated using AFM, contact angle measurements and SEM techniques. The surface hydrophilicity of the fabricated membranes increased with increasing content of PSBMA@GO filler through the water contact angle method. The relative flux of the base membrane at 900 kPa was 66.6 L.m−2.h−1 compared to that of PSBMA@GO composite membrane (0.5 wt%) at 117.67 L.m−2.h−1. The addition of the PSBMA@GO composites resulted in increased fouling resistance with high‐flux recovery (93%) and low‐overall flux decrease ratios (0.01%). Furthermore, nanocomposite membranes exhibited higher dye rejections for Congo Red (CR, 99.1% hence confirming their UF nature), methyl orange (MO, 84.2%) and methylene blue (MB, 95.3%) dyes compared with unmodified CA membranes. Overall, these nanocomposite membranes showed promising properties as potential candidates for dye removal in textile wastewater.

The influence of membrane charge and porosity upon fouling and cleaning during the ultrafiltration of orange juice

The ultrafiltration of orange juice has been performed to separate phytosterols from proteins. Commercial regenerated cellulose acetate (RCA) ultrafiltration membranes of different molecular weight cut offs (MWCOs) of 10 kDa, 30 kDa and 100 kDa were fouled with orange juice and cleaned with Ultrasil 11 over two operational cycles. Fouling and cleaning mechanisms were investigated by using surface zeta potential, Brunauer-Emmet-Teller (BET) analysis and Fourier transform infrared (FTIR) analysis. The RCA conditioned membranes displayed zeta potential values of −0.2 to −31.5 mV. Fouling caused RCA membranes to have a greater magnitude of negative surface charge and cleaning restored the membrane surface charges close to its pristine state. Fouling increased both the total surface area and the total pore volume of all membranes. The total surface area and total pore volume for RCA 100 kDa after fouling increased by 102% and 185%, respectively. Pore area and volume distributions revealed that the porosities were returned close to the original level after cleaning. The recovery flux ratios of RCA 10, RCA 30 and RCA 100 decreased after fouling by 27%, 6% and 10% respectively; and changes were 25%, 9% and 1% respectively after cleaning. The charge of membrane surfaces after two operational cycles and the IR intensity of RCA membrane deposits, varied with MWCO such that RCA 30 > RCA 100 > RCA 10. Ultrafiltration using RCA 10 kDa membrane displayed the best separation efficiency, with 32 ± 4% rejection of phytosterols. and 96 ± 1% rejection of proteins. Changes in membrane surface charge and porosity have been found to affect the RCA membrane performance due to fouling and cleaning during the isolation of phytosterols from orange juice.

Morphology and water flux of produced cellulose acetate membranes reinforced by the design of experiments (DOE)

Cellulose acetate (CA) ultrafiltration membranes were successfully prepared using the non-solvent induced phase separation (NIPS) methodology. This technique is used to produce porous membranes for a large variety of applications. However, the formation of a dense skin during the process reduces membrane pure water flux (PWF). To overcome this issue, three parameters were investigated: CA/NMP (N-methyl-2-pyrrolidone) ratio in the casting solution, acetone (Ac)/water (W) ratio in the precipitation bath composition (PBC) and support material (glass/polyethylene). The effect of each factor on the mean pore size, water contact angle, porosity and PWF was supported by Taguchi design. The increase in the CA/NMP ratio reduced mean pore size and porosity. In contrast, there was an increase in porosity and hydrophilicity with increasing Ac/W ratio. The maximum value of PWF was obtained for membranes prepared using a PE support. ANOVA showed that most, but not all, factors had significant effects on the parameters measured.

Cellulose acetate ultrafiltration membranes customized with copper oxide nanoparticles for efficient separation with antifouling behavior

AbstractCellulose acetate (CA) nanocomposite ultrafiltration membranes are fabricated with copper oxide (CuO) nanoparticles with the aim of improving efficient protein separation and antifouling performance. CuO nanoparticles are synthesized from cupric nitrate using a wet precipitation method and characterized by FTIR and XRD. CA/CuO nanocomposite membranes fabricated using 0.5, 1.0, and 1.5 wt% of CuO nanoparticles individually by simple phase inversion technique. The CA nanocomposite membrane with 0.5 wt% of hydrophilic CuO exhibited enhanced PWF of 118.6 Lm−2 h−1 due to the improvement in porosity and water uptake. This is in good agreement with the enhanced hydrophilicity of the CA/CuO nanocomposite membranes results observed in surface contact angle and morphological investigations. Further, 95.5% of BSA separation and 94.7% of flux recovery ratio (FRR) indicates its superior antifouling potential caused due to the presence of the hydration layer at the CA/CuO membrane surface. Among all the fabricated membranes, the CA‐0.5 nanocomposite membrane with 0.5 wt% of CuO exhibited superiorly improved hydrophilicity, water permeation, BSA separation, and antifouling performance indicates its potential use in water and wastewater treatment applications.

Development and investigation of novel antifouling cellulose acetate ultrafiltration membrane based on dopamine modification

In this contribution, a novel cellulose acetate modified with dopamine (CA-DA) membrane material was designed and prepared by a two-step route consist of chlorination and further substitution reactions. The chemical structure of the prepared CA-DA material was determined by FTIR and 1H NMR, respectively. The CA-DA ultrafiltration membrane was subsequently fabricated by the scalable phase inversion process. Compared with cellulose acetate membrane as the control sample, the introduction of dopamine improved the porosity, pore size and hydrophilicity of the CA-DA membrane, which was helpful to the water permeability (181.2 L/m2h) without obviously affecting the protein rejection (93.5%). According to the static protein adsorption and dynamic cycle ultrafiltration experiments, the CA-DA membrane displayed persistent antifouling performance, which was verified by flux recovery ratio, flux decline ratio and filtration resistance. Moreover, the water flux recovery ratio of the CA-DA membrane was retained at 97.3% after three-cycles of BSA solution filtration, which was much higher than that of the reference CA membrane. This new approach provided a long life and excellent ultrafiltration performance for polymer-based membranes, which has potential application prospects in the field of separation process.

Membrane fouling mitigation for enhanced water flux and high separation of humic acid and copper ion using hydrophilic polyurethane modified cellulose acetate ultrafiltration membranes

The presence of both copper ion (Cu (II)) from industry and humic acid (HA) in natural waters may generate Cu (II)–HA complex, which is a non-biodegradable and toxic organic pollutant in the water. Removal of such toxic substance is of great importance and environmental significance. Although membrane technology provides a solution for the removal via the filtration, fouling still presents a major challenge for the effective separation. In this study, polyurethanes endcapped with β-cyclodextrin and lactic acid were synthesized and used as additives to be blended with cellulose acetate membranes, which possessed enhanced hydrophilicity, permeability and antifouling property for the removal of Cu (II) and HA. As an example, the polyurethane endcapped with lactic acid (LPU-CA) membrane exhibited high pure water flux (PWF) of 648 L m−2 h−1, as well as high flux recovery ratios (FRRs) of 97.8% and 92% and low irreversible fouling rate (Fir) of 2.2% and 7.8% for the ultrafiltration (UF) of HA and Cu (II)–HA complex, respectively, showing excellent anti-fouling performance. In addition, the Cu (II) and HA rejection was greatly enhanced by the HA enhanced complexation process. These results indicated that the polyurethanes modified cellulose acetate membrane provided enhanced separation with good antifouling property, which can be potentially used for the cleaning of the toxic metal-organic pollutants in wastewaters.

Enhanced permeability, mechanical and antibacterial properties of cellulose acetate ultrafiltration membranes incorporated with lignocellulose nanofibrils

Cellulose acetate (CA) ultrafiltration membranes are attracting more attention in wastewater purification due to its biodegradability and eco-friendly. The application of CA membranes, however, is limited by high susceptibility to bacterial corrosion and lack of mechanical tolerance that results in loss of life. To solve the above problems, we first fabricated the CA-based composite membranes incorporated with bamboo-based lignocellulose nanofibrils (LCNFs) by a strategy of phase inversion. LCNFs was prepared by using a combined method of one-step chemical pretreatment and acid hydrolysis coupled with high-pressure homogenization. The as-prepared CA/LCNFs composite membranes with 4 wt% lignin in the LCNFs exhibited high tensile strength of 7.08 MPa and strain-at-break of 12.21%, and high filtration permeability of 188.23 L·m−2·h−1 as ultrafiltration membranes for wastewater treatment, which could obviously inhibit the growth of Escherichia coli.

Effects of GO and MOF@GO on the permeation and antifouling properties of cellulose acetate ultrafiltration membrane

Cellulose acetate (CA) has been used to prepare ultrafiltration membranes because of its excellent properties, especially its biodegradability. To enhance the performance of the CA membrane, the excellent CA ultrafiltration membrane was synthesized by blending with graphene oxide (GO) and HKUST-1 (a metal–organic framework) @GO through the typical phase inversion process. The effects of the different fillers (GO and HKUST-1@GO) on the membrane properties were investigated. Firstly, the fabricated nanocomposites were analyzed through X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then, the action of the fillers on the membrane morphology, permeability, separation performance, and antifouling properties were studied. Compared with CA/GO membranes, the CA/MOF@GO membranes exhibit higher hydrophilicity and pure water flux. This is because HKUST-1 can fully exploit the structure advantages of GO and prevent the stacking of GO layers, introducing unique properties to the HKUST-1@GO composite. The CA/MOF@GO0.12 membrane has the highest water permeate flux of 183.51 L m−2 h−1 and also exhibits better antifouling performance than the CA membrane, which possesses a flux recovery ratio of 88.13% and a total fouling ratio of 40.32%. Hence, HKUST-1@GO shows potential as a filler in ultrafiltration membranes to improve their performance for water purification applications.

The effect of poly ethylene glycol additive on the characteristics and performance of cellulose acetate ultrafiltration membrane for removal of Cr(III) from aqueous solution

The effect of polyethylene glycol (PEG) additive on the characteristics and performance of the cellulose acetate ultrafiltration membrane to chromium metal removal has been studied using some variation of concentration in the casting solution. The concentration of cellulose acetate polymer was 17.5%, whereas the variations of PEG concentration were regulated at 0, 2.5, 5, 7.5 and 10% by weight. Dimethyl formamide (DMF) was used as a solvent. Pure water flux, membrane morphology test, functional group analysis, and molecular weight cut off (MWCO) were investigated to characterize of the prepared membranes. Membrane performance was tested against Cr(III) metal removal. The results confirmed that the pure water flux improved with the increasing of additive concentration. The maximum improvement occurred at membrane with modification using 7.5% PEG. At this PEG concentration, the pure water flux elevated from 49.5 L/m2.h to 62.2 L/m2.h. The addition of PEG successfully improved the membrane flux because the role PEG plays as a pore-forming agent. Membrane with addition of 7.5% PEG showcased rejection result for chromium metal of 31.89%. This value is lower than that of pure CA membrane which rejection value against Cr(III) metal amounted to 35.72%.

Cellulose acetate composite membranes tailored with exfoliated tungsten disulfide nanosheets: Permeation characteristics and antifouling ability

An attempt has been made to demonstrate the effects of exfoliated tungsten disulfide (E-WS2) nanosheets on the fabrication, permeation and anti-fouling performance of cellulose acetate (CA) ultrafiltration membranes. The E-WS2 was prepared and characterized in terms of energy dispersive X-ray spectroscopy (EDXS) and X-ray diffraction spectroscopy (XRD). Pure and composite CA membranes were methodically characterized for its surface, chemical and morphological structure using FT-IR, XRD, SEM and water contact angle analysis. Filtration characteristics of membranes such as pure water flux, porosity and hydraulic resistance were also studied. The addition of E-WS2 nanosheets exhibited significant improvement in the surface hydrophilicity of composite membranes than the control CA membrane and are evidenced by the observed contact angle and porosity values. However at 1 wt% E-WS2 concentration, CA membrane showed lower water flux (92.3 ± 0.5) due to the pore plugging effect. The flux recovery ratio (FRR), bovine serum albumin (BSA) rejection, reversible and irreversible fouling experimental results suggested that CA/E-WS2 (1 wt%) UF membranes possess better fouling resistance potential than control CA membrane as a result of enhanced hydrophilicity. This study emphasizes the strong interplay between CA and E-WS2 nanosheets which play a significant role in altering the permeation and antifouling characteristics of nanocomposite membranes.

Cork processing wastewaters components fractioned by ultrafiltration membranes – studies of antioxidant and antitumoral activity

AbstractBACKGROUNDCork processing wastewater is an environmental problem due to its high content of organic matter, such as sugars and non‐biodegradable compounds such as polyphenols (PPs), namely tannins. Membrane technology aimed at valorisation of the wastewaters components, concentrate stream, and simultaneously offer a pre‐treatment of the wastewater, permeate stream. In this work, the identification of bioactive PPs was also envisaged. Several fractions of cork processing wastewaters were generated using two cellulose acetate ultrafiltration membranes of 3 kDa and 74 kDa for PPs isolation according to nature and molecular weights. The membranes were prepared by the phase inversion method and fractionation was made in concentration and diafiltration modes. The wastewater and the fractions were analyzed in terms of total organic carbon, total phenols, tannins and total polysaccharides content and the compounds present were identified by FTIR, LC–MS and quantified by HPLC‐DAD.RESULTSCompounds such as quinic, gallic, protocatechuic, brevifolin carboxylic and ellagic acids were identified as the major compounds in cork wastewater. The wastewater and the fractions were tested for antioxidant activity and for capacity to inhibit the proliferation of the growth of human breast carcinoma cell lines, MCF‐7. The fractions revealed high antioxidant activity with EC50 values ranging from 1.174 ± 0.069 to 1.943 ± 0.179 mg/mgDPPH. The fractions demonstrated to be efficient as cell proliferation inhibitors, with values of IC50 ranging from 0.20 ± 0.003 to 0.46 ± 0.02 mg mL‐1.CONCLUSIONThe process reported demonstrates that PPs compounds can be recovered from cork effluent and further reused as high‐value bioactive compounds. © 2017 Society of Chemical Industry

Exploration of permeability and antifouling performance on modified cellulose acetate ultrafiltration membrane with cellulose nanocrystals

Cellulose nanocrystals (CNCs) were introduced into cellulose diacetate (CDA) matrix via immerged phase-inversion process, aiming to improve the filtration and antifouling performance of CNCs/CDA blending membrane. The effects of CNCs on membrane morphologies, hydrophilicity, permeability and antifouling property were investigated. Results showed that the incorporation of CNCs into CDA membrane could effectively enhance the permeability and antifouling property of CNCs/CDA blending membrane by optimizing membrane microstructure and improving membrane hydrophilicity. A high pure water flux of 173.8L/m2h was achieved for the CNCs/CDA blending membrane at 200KPa, which is 24 times that of the CDA membrane (7.2L/m2h). The bovine serum albumin (BSA) adsorption amount of the CNCs/CDA blending membrane decreased about 48% compared to that of the CDA membrane. Additionally, the CNCs/CDA blending membrane exhibited better antifouling performance with the flux recovery ratio (FRR) of 89.5% after three fouling cycles, compared to 59.7% for the CDA membrane.

Removal of bovine serum albumin from wastewater using fouling resistant ultrafiltration membranes based on the blends of cellulose acetate, and PVP-TiO2 nanoparticles

Fouling resistant ultrafiltration membranes based on the blends of polyvinylpyrrolidone (PVP), TiO2 nanoparticles and cellulose acetate, CA-PVP-TiO2 (CATP), for removal of bovine serum albumin (BSA) were prepared by using phase inversion process. The influences of PVP and TiO2 on the preparation of phase inverted cellulose acetate (CA) ultrafiltration membrane were explored in terms of morphology study, equilibrium water content (EWC), hydraulic resistance, permeability performance, hydrophilicity, and thermal stability. After the introduction of PVP and TiO2 to the ternary (polymer-solvent-non-solvent) system, the formations of finger-like structures and macro-voids were reduced significantly. An improvement in porosity, average pore size, and hydrophilic nature of the CA membranes were detected after the introduction of PVP and TiO2 into the polymer matrix. The interaction between TiO2 and CA was confirmed and the degradation temperature of the CA membrane was significantly improved. BSA protein removal efficiency, anti-fouling performance, and recycling potential of the UF membranes were investigated. The CATP membrane (10.5 wt % CA: 4 wt % PVP: 2 wt % TiO2) has displayed high BSA removal efficiency and flux recovery ratios (NFR) with enhanced anti-fouling performances for the three fouling/rinsing cycles.

Facile Synthesis of Cellulose Acetate Ultrafiltration Membrane with Stimuli‐Responsiveness to pH and Temperature Using the Additive of F127‐b‐PDMAEMA

AbstractWe fabricate a novel cellulose acetate (CA) ultrafiltration membrane modified by block copolymer F127‐b‐ PDMAEMA, which is synthesized using F127 and DMAEMA via the ARGET ATRP method. Compared to conventional ultrafiltration membranes, the incorporation of both F127 and PDMAEMA can not only readily increase the hydrophilicity of the membrane, but also exhibit stimuli‐responsiveness to temperature and pH. Fourier transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC) are employed to analyze the structure of the F127‐b‐PDMAEMA. The membrane properties are evaluated via scanning electron microscope (SEM) imaging, porosity test, automatic target recognition Fourier transform infrared spectroscopy (ATR‐FTIR), water contact angle test and permeation test. The results indicate that the F127‐b‐PDMAEMA is an excellent pore agent, which contributes to an enhancement of the membrane in sensitivity to temperature and pH. The modified membrane also exhibits lower water contact angle (64.5°), which is attributed to the good anti‐fouling performance and high water permeation.