Modified Cellulose Acetate Membranes Research Articles

Hydrophylicity Enhancement of Modified Cellulose Acetate Membrane to Improve the Membrane Performance in Produced Water Treatment

Produced water is a wastewater generated from petroleum industry with high concentration of pollutants such as Total Dissolved Solid, Organic content, and Oil and grease. Membrane technology has been currently applied for produced water treatment due to its efficiency, compact, mild and clean process. The main problem of produced water using membrane is fouling on the membrane surface which causes on low permeate productivity. This paper is majority focused on the improvement of anti-fouling performance through several modifications to increase CA membrane hydrophilicity. The membrane was prepared by formulating the dope solution consists of 18 wt-% CA polymer, acetone, and PEG additive (3 wt-%, 5 wt-%, and 7 wt-%). The membranes are casted using NIPS method and being irradiated under UV light exposure. The SEM images show that parepared membrane has asymmetric structure consist of dense layer, intermediete layer, and finger-like support layer. The filtration test shows that PEG addition increase the membrane hydrophilicity and the permeate flux increases. UV light exposure on the membrane improves the membrane stability and hydrophilicity. The imrpovement of membrane anti-fouling performance is essential to achieve the higher productivity without lowering its pollutants rejection.

Removal of chromium (VI) ions from aqueous solutions using amine-impregnated TiO2 nanoparticles modified cellulose acetate membranes

In this work, TiO2 nanoparticles (NPs) were modified using tetraethylenepentamine (TEPA), ethylenediamine (EDA), and hexamethylenetetramine (HMTA) amines using impregnation process. The prepared amine modified TiO2 samples were explored as an additive to fabricate ultrafiltration membranes with enhanced capacity towards the removal of chromium ions from aqueous solution. Modified membranes were prepared from cellulose acetate (CA) polymer blended with polyethylene glycol (PEG) additive, and amine modified TiO2 by using phase inversion technique. Fourier transform infrared spectroscopy (FTIR), zeta potential (ζ), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), water contact angle (WCA), and atomic absorption spectrophotometer (AAS) studies were done to characterize the membranes in terms of chemical structure, electric charge, thermal stability, morphology, hydrophilicity, and removal performance. The pure water permeability and Cr (VI) ion removal efficiency of the unmodified (i.e. CA/U-Ti) and the amine modified (CA/Ti-HMTA, CA/Ti-EDA, and CA/Ti-TEPA) membranes were dependent on pH and metal ion concentration. Incorporation of amine modified TiO2 composite to the CA polymer was found to improve the fouling and removal characteristics of the membranes during the chromium ultrafiltration process. The maximum removal efficiency result of Cr (VI) ions at pH of 3.5 using CA/Ti-TEPA membrane was 99.8%. The washing/regeneration cycle results in this study described as an essential part for prospect industrial applications of the prepared membranes. The maximum Cr (VI) removal results by using CA/Ti-TEPA membrane for four washing/regeneration cycles are 99.6%, 99.5%, 98.6% and, 96.6%, respectively.

Role of layered materials in emulsified oil/water separation and anti-fouling performance of modified cellulose acetate membranes with hierarchical structure

Membranes with hierarchical architectures consisted of 1D and 2D materials have shown excellent performance in emulsified oil/water separation, but the roles of 2D layered materials in oil/water separation and anti-fouling performance are still to be clarified. Here, we used a facile layer-by-layer assembling approach to fabricate 3D hierarchical membranes using a porous cellulose acetate support membrane coated with graphene oxide (GO) or layered double hydroxides (LDH) grafted with sepiolite (SeP), and then the roles of GO and LDH in oil/water separation and anti-fouling performances of these hierarchically modified membranes were investigated. Results of characterization experiments showed that these membranes were successfully fabricated. Wetting behavior of these membranes indicated that the hierarchical structure can provide high permeate flux and underwater superoleophobic properties. Though the fabrication processes were similar, the surface of SeP + GO and Sep + LDH coated membrane showed different morphologies. After cyclic oil/water separation experiments we found that SeP + GO coated membranes exhibited higher flux and slower decline of permeation than SeP + LDH coated membranes due to its unique properties. Our research demonstrated that the properties of 2D layered materials play important roles in determining water permeability and anti-oil-fouling performance of modified membranes with hierarchical structure.

Separation of macromolecular proteins and removal of humic acid by cellulose acetate modified UF membranes

Surface modifying macromolecules (SMMs) were synthesized with various polyurethane pre polymers end-capped with different groups and blended into the casting solution of cellulose acetate (CA) to prepare surface modified ultra-filtration (UF) membranes for water filtration applications. The surface modification of the CA membranes was confirmed by the FTIR and static contact angle (SCA) measurements. The membranes so prepared had the typical characteristics of UF membranes as confirmed by scanning electron microscopy (SEM). Membrane properties were studied in terms of membrane compaction, percentage water content (%WC), pure water flux (PWF), membrane hydraulic resistance (Rm), molecular weight cut-off (MWCO), average pore size and porosity. The result showed that PWF, %WC, MWCO and pore size increased whereas the Rm decreased by the addition of SMMs. The significant effect of SMMs on the fouling by humic acid (HA) was also observed. It was found that the cSMM-3 membrane, in which SMM was synthesized with diethylene glycol (DEG) and hydroxyl benzene sulfonate (HBS) was blended, had the highest flux recovery ratio FRR (84.6%), as well as the lowest irreversible fouling (15.4%), confirming their improved antifouling properties. Thus, the SMM modified CA membranes had proven, to play an important role in the water treatment by UF.

Fabrication of Potentiometric Cholesterol Biosensor by Crosslinking of Cholesterol Oxidase and Carbon Nanotubes Modified Cellulose Acetate Membrane

Fabrication of Potentiometric Cholesterol Biosensor by Crosslinking of Cholesterol Oxidase and Carbon Nanotubes Modified Cellulose Acetate Membrane

Influence of bentonite in polymer membranes for effective treatment of car wash effluent to protect the ecosystem

In this study, modified polyethersulfone (PES) and cellulose acetate (CA) membranes were used in the treatment of car wash effluent using ultrafiltration. Hydrophilic sulfonated poly ether ether ketone (SPEEK) and bentonite as nanoclay were used as additives for the PES and CA membrane modification. Performances of modified membranes were compared with commercial PES membrane with 10kDa molecular weight cut off (MWCO). The influencing parameters like stirrer speed (250–750rpm) and transmembrane pressure (100–600kPa) (TMP) were varied and their effects were studied as a function of flux. In the treatment of car wash effluent, a higher permeate flux of 52.3L/m2h was obtained for modified CA membrane at TMP of 400kPa and stirrer speed of 750rpm. In comparison with modified PES membrane and commercial PES membrane, modified CA membranes showed better performance in terms of flux and flux recovery ratio. The highest COD removal (60%) was obtained for modified CA membrane and a lowest COD removal (47%) was observed for commercial PES membrane. The modified membranes were better at removing COD, turbidity and maintained more stable flux than commercial PES membrane, suggesting they will provide better economic performance in car wash effluent reclamation.

Preparation of modified cellulose acetate membranes using functionalized multi-walled carbon nanotubes for forward osmosis

AbstractNovel modified cellulose acetate (CA) membranes using functionalized multi-walled carbon nanotubes (MWCNTs) were synthesized by phase inversion via immersion precipitation technique. Carboxylated functionalized MWCNTs (F-MWCNTs) were used as additives into the casting solution of CA, 1, 4-dioxane, acetone, lactic acid, and methanol to enhance the forward osmosis (FO) membranes performance. Different contents of F-MWCNTs (0.01, 0.05, and 0.1 wt.%) were added into the casting solution. The novel synthesized CA/F-MWCNTs membranes were characterized by various methods in terms of membranes structure and surface properties, as well as FO performance, and then compared with traditional CA membrane and commercial FO membrane. The surface hydrophilicity, porosity, and tensile strength of CA/F-MWCNTs membranes were improved with the increment of the content of F-MWCNTs in the casting solution. The morphological studies showed that the addition of F-MWCNTs significantly changed the surface properties of the...

Preparation, characterization and performance of cellulose acetate ultrafiltration membranes modified by charged surface modifying macromolecule

A charged surface modifying macromolecule (cSMM) was synthesized, characterized by FT-IR spec- troscopy and blended into the casting solution of cellulose acetate (CA) to prepare surface modified UF membranes by phase inversion technique. With an increasing cSMM additive content from 1 to 4 wt%, pure water flux (PWF) and water content (WC) were increases whereas the hydraulic resistance decreases. Surface characteristic study reveals that the surface hydrophilicity increased in cSMM modified CA membranes. The pore size and surface porosity of the 4 wt% cSMM blend CA membranes increases to 41.26 A and 0.015%, respectively. Similarly, the molecular weight cut-off (MWCO) of the membranes ranged from 20 to 45 kDa, depending on the various compositions of the prepared membranes. Lower flux decline rate (47.2%) and higher flux recovery ratio (FRR) (89.0%), exhibited by 4 wt% cSMM blend membranes demonstrated its fouling resistant characteristic compared to pristine CA membrane.

Effect of Membrane Preparation Methods on the Release of Theophylline through CA Membranes at In-Vitro Conditions

In this study the effect of the membrane preparation methods on the release of theophylline through cellulose acetate (CA) membranes was studied at in vitro conditions. CA/acetone binary and CA/acetone/water ternary systems were used as casting solutions and poly(ethylene glycol) (PEG) was used as the pore forming, plasticizing agent in the study. Membranes were characterized by FTIR, SEM, and DSC analysis. It was determined that pH, temperature and drug concentration affected the release of theophylline. A decrease in pH, increase in temperature and drug concentration increased the permeated amount of theophylline through the membranes. In addition, receiver solution circulation at a capillary blood rate increased the permeation of theophylline. As a result of the study, it was concluded that the release of theophylline could be controlled for a prolonged period of time and modified CA membranes prepared in the study could be as an advisable membrane material for potential release of theophylline at transdermal conditions.

Preparation and applications of poly vinyl alcohol (PVA) modified cellulose acetate (CA) membranes for forward osmosis (FO) processes

Polyvinyl alcohol (PVA)-coated cellulose acetate (CA)-based flat-sheet membranes have been fabricated and tested in the forward osmosis (FO) process. PVA was used as a surface modifying agent. CA membranes prepared by conventional immersion precipitation were treated in an aqueous solution of PVA and tested water flux and salt rejection. The effects of PVA concentration, treatment time on the hydrophilicity of membrane surface, water permeability, and salt retention property of the membrane were estimated. The modified membrane was characterized by X-ray photoelectron spectroscopy and contact angle measurement. A hydrophilicity of membrane surface was observed in longer modification times and the higher PVA solution concentration accounted for a attaching of the PVA chains by glutaraldehyde as cross-linking agent. The best condition of salt rejection and permeability performance was obtained by using 1 wt% PVA solution and treatment time of 2 min. In the FO process, modified CA membrane exhibited water flux 20% higher than unmodified CA membrane without salt leakage. This result indicated that PVA coating improved water flux performance for FO processes.

Pharmaceutical and personal care products removal from drinking water by modified cellulose acetate membrane: Field testing

To maximize the removal of charged pharmaceutical and personal care products (PPCPs), modified cellulose acetate (CA) nanofiltration (NF) membranes were developed by incorporating charged surface modifying macromolecules (CSMM) to increase their surface charge. The objective of this study was to evaluate their removal of trace levels of PPCPs at two water treatment plants. This new membrane and a commercial thin-film composite (TFC) NF membrane (Filmtec NF-270) were tested simultaneously in the field using two SEPA cells. The testing was conducted at the Britannia Water Treatment Plant (Ottawa, ON) and the Walkerton Clean Water Centre (Walkerton, ON). The challenge waters were filter effluents spiked with ppt and ppb levels of carbamazepine (CBZP), ibuprofen (IBUP) and sulfamethazine (SFMZ). The new experimental modified CA membrane achieved very good IBUP removals, good SFMZ removals and poor CBZP removals. The commercial TFC NF membrane (NF-270) had better removals and significantly higher fluxes than the modified CA membrane. The larger removals are not surprising given that the commercial membrane is the result of extensive development and optimization, while the modified CA membrane has undergone very limited optimization. The larger flux of the NF-270 membrane is also expected given that this is a TFC membrane, while the experimental modified membrane was prepared via a single casting step via the phase inversion technique which produces a thicker skin layer.

Cellulose acetate hollow fiber nanofiltration membrane with improved permselectivity prepared through hydrolysis followed by carboxymethylation

Cellulose acetate (CA) hollow fiber membrane with improved permselectivity for nanofiltration was developed by hydrolysis and carboxymethylation of an original cellulose triacetate semi-permeable membrane. The effects of these modifications on the structure and surface properties were characterized by ATR-FTIR, XRD, SEM and measurements of streaming potential and contact angle. The permeation attributes of the obtained membrane were evaluated through cross-flow permeation tests and the improved permselectivity was also demonstrated through dye removal tests. The results showed that hydrolysis greatly increased the membrane pore size and surface hydrophilicity, but decreased the membrane surface charge, while carboxymethylation had little effect on the membrane pore size, but increased the membrane surface hydrophilicity and negative charge. CA hollow fiber nanofiltration membrane with a pure water permeability of 5.2l/m2hbar, NaCl rejection of 66.4% and Na2SO4 rejection of 95.4% could be obtained through modification an original CA semi-permeable membrane having a pure water permeability of 2.3l/m2 h bar, NaCl rejection of 90.8% and Na2SO4 rejection of 91.5%. Additionally, in treating Congo red and Methyl blue aqueous solutions, the modified CA membrane exhibited improved dye removal rates and higher water fluxes of more than two times compared with the original membrane.

XPS and contact angle characterization of surface modified cellulose acetate membranes by mixtures of PMHS/PDMS

A mixture of polymethylhydrosiloxane (PMHS) and polydimethylsiloxnae (PDMS) is used for modifying the surface of reverse osmosis and nanofiltration membranes. The porous substructure made of cellulose acetate (CA) was obtained by a phase separation process from acetone/formamide (2/1wt/wt) casting solutions. Two polymer concentrations (22 and 25wt.%) were used with a heat post-treatment temperature (80°C) in order to produce membranes with pore sizes responding to nanofiltration and reverse osmosis needs. Overcoating the CA substructure with a PMHS–PDMS thin layer gave rise to the composite membranes.Surface characterization with X-ray Photoelectron Spectroscopy (XPS) indicates the success of modifying the CA membrane surface with PMHS–PDMS. Contact angle measurements showed an increase in hydrophilicity of the modified membrane surface. Tensile strength measurements indicate that modification by a mixture of PMHS–PDMS has an insignificant decrease in Young's modulus. The pure water flux measurements reveal that layer modification by PMHS–PDMS show an improvement in water permeability which is in agreement with contact angle results.

Bufferless lysis of erythrocytes for isolation of hemoglobin using modified cellulose acetate membranes

This paper presents a modified cellulose acetate membrane prepared using a dry casting technique that can be used to perform lysis of erythrocytes and isolation of hemoglobin. Isolation of hemoglobin is thus achieved without the use of lysis buffers. Cellulose acetate (CA) membranes are embedded with ammonium chloride (NH4Cl) and potassium bicarbonate (KHCO3), which act as lysing agents. The presence of embedded salts is confirmed using EDS analysis. The pores in the CA membrane act as filters. The average pore size in these membranes is designed to be 1.5 μM, as characterized by SEM analysis, so that they allow hemoglobin to pass through and block all other cells and unlysed erythrocytes present in blood. When a drop of blood is added to the membrane, the NH4Cl and KHCO3 embedded in the membrane dissolve in plasma and lyse the erythrocytes. The filtered hemoglobin is characterized using UV-Vis Spectroscopy. The results indicate extraction of higher concentration of hemoglobin compared with conventional methods.

Modeling kinetics and thermodynamics of Cs+ and Eu3+ removal from waste solutions using modified cellulose acetate membranes

Removal of Cs+ and Eu3+ ions using cellulose acetate (CA) and modified CA was studied. Cellulose acetate was modified using acrylamide (AAm) and polyethylene glycol (PEG). Specifically, CA, CA/AAm, and CA/PEG were used to remove Cs+ and Eu3+ from aqueous waste solutions. The CA-metal and modified CA-metal interactions were studied under different conditions such as concentration of metal ions and temperature in the range 298K–333±1K. Experimental equilibrium sorption data were analyzed using Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. These data were better fitted to both Langmuir and D–R isotherms compared to Freundlich model. On the other hand the sorption processes were better represented by pseudo-second order kinetic model. The sorption processes were endothermic with ΔHo values 16.20, 23.55, and 21.70 (kJ/mol) for sorbed Cs+ ions onto CA, CA/AAm, CA/PEG, whereas that for sorbed Eu3+ are 21.79, 23.87 and 75.34 (kJ/mol), respectively. The entropy values ΔSo for Cs+ ion sorbed onto CA, CA/AAm, and CA/PEG are 50.72, 80.15, and 77.10 (J/molK), whereas that for the sorbed Eu3+ ion are 75.0, 87.30 and 256.10 (J/molK) respectively. The activation energy, Ea, for Cs+ and Eu3+ ions sorbed onto all studied sorbent materials lies in the range 8.73–26.32 (kJ/mol) and 24.27–78.11 (kJ/mol), respectively. The negative values of Gibbs free energy, ΔGo, confirm the feasibility and the spontaneous nature of both Cs+ and Eu3+ ions sorption removal using CA and AAm and PEG modified CA and indicating that the sorption processes are chemi-sorption mechanisms. The sorption removal capacities of both Cs+ and Eu3+ were in the order CA/PEG>CA/AAm>CA. The batch and dynamic sorption results show that the modified CA/PEG, CA/AAm, and CA membranes can be used to remove Cs+ and Eu3+ ions from wastewater.

The effects of urease immobilization on the transport characteristics and protein adsorption capacity of cellulose acetate based hemodialysis membranes

In this study, cellulose acetate (CA) based hemodialysis membranes were prepared by a dry phase inversion method and the influences of urease immobilization on the clearing performance and protein adsorption capacity of the membranes were investigated. Permeation experiments have shown that modification of CA membranes with urease immobilization not only enhanced the transport rate of urea but also increased the permeation coefficients of uric acid and creatinine by changing the structure of the membrane. Furthermore, the protein adsorption capacity of the CA membranes decreased. On the other hand, the mechanical strength of the modified CA membrane did not change significantly compared with that of the unmodified one. A mathematical model was derived to determine the rate of mass transfer of urea through modified CA membranes. Model predictions along with the experimental data suggest that urease immobilization can be used as an alternative method in preparing CA based hemodialysis membranes with improved transport characteristics and biocompatibility through reduced protein adsorption capacities.

Concentration and detection of Salmonella in mung bean sprout spent irrigation water by use of tangential flow filtration coupled with an amperometric flowthrough enzyme-linked immunosorbent assay.

The development of a culture-free method for Salmonella screening of spent irrigation water derived from sprouting mung bean beds is described. The system used tangential flow filtration (TFF) to nonspecifically concentrate cells from large (2- to 10-liter) sample volumes. The retentate (100 ml) from the TFF was then flowed over an anti-Salmonella antibody-modified cellulose acetate membrane. The captured Salmonella was detected by reacting with a secondary anti-Salmonella and goat anti-rabbit biotin labeled antibody, followed by avidin-tagged glucose oxidase. The hydrogen peroxide generated from the enzymic oxidation of glucose was amperometrically detected at an underlying platinum electrode. It was found that 10 liters of Salmonella suspensions of 2 log CFU/ml could be concentrated to 4 log CFU/ml with 60% recovery regardless of the flow rate (112 to 511 ml/min) or transmembrane pressure (0 to 20 lb/in2) applied. The solids content of spent irrigation water negatively affected the filtration rate of TFE. This was most evident in spent irrigation water collected in the initial 24 h of the sprouting period, where the solids content was high (4,170 mg/liter) compared with samples collected at 96 h (560 mg/ liter). Trials were performed using mung bean beds inoculated with different Salmonella levels (1.3 to 3.3 log CFU/g). By using the optimized TFF and flowthrough immunoassay it was possible to detect Salmonella in spent irrigation water at levels of 2.43 log CFU/ml within 4 h. The integrated concentration and detection system will provide a useful tool for sprout producers to perform in-house pathogen screening of spent irrigation water.

Heat and moisture transfer in application scale parallel-plates enthalpy exchangers with novel membrane materials

Parallel-plates enthalpy exchangers are one of the most commonly encountered energy recovery devices that are used to simultaneously transfer both sensible heat and moisture between fresh air and exhaust ventilation air. For such equipments, the water vapor sorption properties of the plate materials have tremendous impacts on system performance. In this investigation, three different materials, namely, common paper, CA (cellulose acetate) membrane and a modified CA membrane) are selected as the plate materials for three enthalpy exchangers. Sorption curves and contact angles of these three materials are measured to reflect their hydrophilicity. The steady-state sensible and latent effectiveness of the three exchangers are tested in a special test rig, and the test results are compared with the model predictions. A heat and moisture transfer model for the enthalpy exchangers is proposed. The effects of the varying operating conditions like air flow rates, temperature, and humidity on the sensible and latent effectiveness are evaluated. Both the numerical and experimental results indicate that the moisture resistance through plates is co-determined by thickness, sorption slope, and sorption potential. Moisture diffusivity in various materials is in the same order. So when the plate thickness is fixed, the higher the sorption slopes are, the higher the latent performance is. Of the three exchangers, the exchanger with the modified CA membrane material has the highest performance due to small thickness, steep sorption slope, and large sorption potentials. The paper exchanger has a latent effectiveness of 0.4, while the membranes have latent effectiveness of greater than 0.7.

Adsorption and electrochemical studies on surfactant modified cellulose acetate membranes

The possibility of the modification of a cellulose acetate membrane upon adsorption of ionic surfactants, cetyl pyridinium chloride and sodium dodecyl sulphate has been investigated on the basis of membrane potential studies. For the estimation of the extent of adsorption, surface tension measurements were carried out in the presence and absence of cellulose acetate membrane using surfactant solutions of variable compositions. The results have also been used for the characterization of the thermodynamic equilibrium, which the membrane surfactant system attains upon surfactant adsorption, in terms of the immobilization constant.

Physicochemical characterization of a modified cellulose acetate membrane for the design of oil-in-water emulsion disruption devices

In this paper, a new membrane separation process is presented. This process is based on a multiple chamber cell that allows the separation of oil from water by placing two membranes of different hydrophobicity in contact with the emulsion. Further chemical modifications of the membranes have been performed in order to vary their hydrophobicity in the perspective of optimizing the fractionation process via specific interactions between membrane and emulsion components. For this purpose, methylcellulose was modified with 1,2-epoxydodecane and incorporated in the membrane elaboration process. The modification of membrane surface chemical structure was demonstrated by ATR-FTIR and XPS experiments. Preliminary filtration tests are presented as well as future perspectives to optimize the membrane modification procedure.