Enhanced performance of cellulose triacetate membranes using binary mixed additives for forward osmosis desalination (original) (raw)
Related papers
Jurnal Teknologi, 2017
Osmotically-driven forward osmosis (FO) has gained significant attention in the last decade due to its potential application in various disciplines. Draw solution serves as the driving force in FO process for inducing water transport across the membrane. FO technology can be used to reject or concentrate high valuable products in the chemical and bioprocess industries which often encounter great challenge in terms of dilute product formation. In this study, commercial cellulose triacetate (CTA) flat sheet FO membrane was investigated using several types of inorganic draw solute. Pure water fluxes ranged from 5.20 to 6.30 L.m-2 .h-1 were achieved for selected draw solutes. The reverse solute leakage was shown by the increment of conductivity in the feed solution. Among the draw solutes, NaCl demonstrated highest reverse solute leakage (72.45 µS cm-1) attributed to its relatively smaller molecular size. The water fluxes at feed to draw solution volume ratios of 1:2 and 1:3 were found to be slightly lower than that to the volume ratios of 1:0.6 and 1:1. With respect to sodium succinate feed solution, MgCl2 was capable of generating higher osmotic pressure and thus higher water flux was observed compared to NaCl draw solute. Overall, the selected inorganic draw solutes demonstrated encouraging FO performances and could be used for concentrating sodium succinate solution.
Preparation of cellulose triacetate/cellulose acetate (CTA/CA)-based membranes for forward osmosis
Journal of Membrane Science, 2013
Cellulose triacetate/cellulose acetate (CTA/CA)-based membranes for forward osmosis (FO) were prepared by immersion precipitation. Casting composition and preparation conditions-1,4-dioxane/ acetone ratio, CTA/CA ratio, substrate type, casting thickness, evaporation time and annealing temperaturewere tested for their effects on formation and subsequent performance of membranes. Membranes were characterized by various methods, and their performances were tested against commercially available membranes. The FO membrane prepared under optimized composition and conditions had a smooth surface and showed higher water flux and salt resistance than the commercial membranes. Annealing improved the membrane performance by removing residual additives and solvents. The computerized image processing of optical microscopy images was shown to be useful for assessing the membrane substrates.
Improvement of cellulose acetate forward osmosis membrane performance using zinc oxide nanoparticles
DESALINATION AND WATER TREATMENT
With the continual progress in developing the forward osmosis (FO) membrane, in both industry and academia, it is prospected to remain the best alternative technique for the production of freshwater. The current paper focuses on the preparation and characterization of FO membranes and ZnO nanoparticles (ZnO NPs) that can be used for membrane modification to enhance its performance. FO membranes are fabricated in our labs from the cellulose acetate (CA) polymer by phase inversion methods. These membranes are easy to prepare, stable against bacterial attack, chemical, and mechanical changes, as well as showing excellent performance and superior economics. The optimum conditions for preparing forward osmosis cellulose acetate (FO-CA) membranes are; 7 wt.% CA, 92.75 wt.% acetone, and 0.25 wt.% ZnO NPs per unit percentage of CA in aqueous solution. A new approach for the modification of CA membranes using the synthesized ZnO NPs was shown to enhance the performance of membranes for forward osmosis water desalination process. We study the effect of polymer concentration, membrane thickness, and membrane modification by ZnO NPs on membrane performance. The fabricated membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy, and the mechanical properties were studied in order to expose the best membrane for water desalination and also the synthesized ZnO NPs were characterized by XRD and SEM. The performance of the CA/ZnO NPs membranes were examined using parameters, such as contact angle, surface area and pore size, water flux (J w), and salt rejection (R%). Compared with the pure CA membrane, the CA membrane modified with ZnO NPs was more hydrophilic, with an improved water contact angle (~47.6 ± 2°) over the pure CA membrane (~63.85 ± 2°) and it showed improving in water flux (26.57 L h −1 m −2) over the pure CA membrane (19.42 L h −1 m −2), also it showed salt rejection 99.5% of Na + , 100% of Cl-, and 99.6% of Mg 2+. The water flux increased in the case of CA membrane modified with ZnO NPs is due to increasing in surface area and total pore volume than the pure CA membrane by 23% and 20%, respectively. This demonstrates that the CA membrane modified with ZnO NPs can significantly improve the membrane performances and was suitable to enhance the selectivity, and water flux of the membranes for water desalination.
6TH INTERNATIONAL CONFERENCE ON ENVIRONMENT (ICENV2018): Empowering Environment and Sustainable Engineering Nexus Through Green Technology, 2019
Forward osmosis (FO) membrane was fabricated from acetylated nata de coco (NDC). Acetylation of NDC was done by subjecting it to dissolution by 2 concentrations (1% and 2%) of methylene chloride for 72-hours prior to solvent evaporation to form the FO membrane. Membranes were characterized in terms of thickness, hydrophilicity, morphology, and tensile strength. A laboratory-scale FO system was used to test the performance of modified NDC FO membrane in desalination by determination of water flux, salt flux, and salt rejection. The FO system employs three kinds of feed solutions (deionized (DI) water, 0.6 M NaCl, and seawater) and 2M sucrose as draw solution. The water permeability coefficient was also determined. The dried unmodified NDC sheet was used as control to check if the modified NDC can function as FO membrane. The DI water fluxes of 1.19 L/m 2-h (LMH) and 0.67 LMH were recorded for 1% and 2% modified-NDC membranes, respectively. These values are lower compared to the 6.24 LMH observed with the dried unmodified NDC sheet. Water fluxes of 0.6 M NaCl solution and seawater are similar for both 1% and 2% modified-NDC membranes that ranges from 0.51 to 0.56 LMH. High salt rejections were observed for all feed solutions ranging from 91% to 97.9%. The tensile strengths of the membranes are 54.30 and 117.88 N/mm 2 for the 1% and 2% modified-NDC membrane, respectively. These suggest that the modified FO-NDC membrane is suitable for FO process.
Membranes having high water flux and minimum reverse solute flux at low operating pressures are the ideal membranes for the forward osmosis (FO) process. In this work, we report the use of a LbL surface modification strategy to fabricate a novel positively charged FO membranes. The main purpose of this work was to fabricate an effective selective layer onto a commercial PES ultrafiltration membrane, which functioned as a support layer, to provide the best performance for treatment of brackish water by FO. The new membranes containing a mixing ratio of 0.1 MPDADMAC: 0.001 MCMCNa in the polyelectrolyte complex exhibited the best performance in terms of minimum reverse solute flux and acceptable water flux as compared to that for membranes containing a mixing ratio of 0.1 MPDADMAC: 0.01 MCMCNa. The improved performance and physicochemical properties of the new membranes were explored by various analytical techniques and were compared to the pristine membrane. Firstly, structural characterization revealed that the new selective layer was homogenous, uniform and strongly adhered to the substrate resulting in excellent water permeability and acceptable reverse solute flux. Secondly, it was found that the optimal curing temperature was 60 O C for 4 h that contributed to enhanced membrane performance. Lastly, the developed ranking protocol was adopted to optimize the membrane performance in terms of the water permeability coefficient (A) and solute permeability coefficient (B). According to this optimization procedure, the best performing membrane was membrane coated 2.5 bilayers which had water permeability and solute permeability coefficients of 23.1 L m −2 h −1 bar −1 and 1.54 L m −2 h −1 respectively.
Environmental Technology, 2019
In order to enhance characteristic performance of cellulose acetate (CA) membranes, a novel nanofiller synergy is adopted herein for desalination purpose. Activated zinc oxide and aerosilica synergy in seven different ratio based combinations were introduced into CA matrix adopting solution mixing technique. The functionalized nanofillers loading impact on membranes surface texture, crystalline structural difference, functional groups presence, thermal decomposition and phase transition temperatures were scrutinized. The solely membranes were practically employed to determine salts (NaCl and MgCl2) rejection tested by dead end filtration system. Time dependent flux rate and fouling study was performed to decide the reuseability of 2 nanocomposite membranes. The results validate a remarkable improvement by idiosyncratically synthesized nanocomposite membranes.
Nanotechnology for Environmental Engineering (Published by: Springer), 2021
This study was conducted to develop ultrathin forward osmosis (FO) membrane by phase inversion process. Hydrophilic cellulose acetate (CA) polymer and titanium dioxide (TiO 2) nanoparticles were used to form a highly water permeable and stable FO membrane. The physical characteristics of prepared nanomaterial and membrane were characterized by scanning electron microscopy, elemental mapping and x-ray diffraction. The FO performance of the developed membrane was evaluated in terms of pure osmotic water flux and reverse salt flux. A consistent water flux was observed during a long-term experiment with the help of the fabricated membrane. Average water flux of 33.63 L/m 2 /h and reverse salt flux of 10.34 g/ m 2 /h were achieved due to extensive hydrogen bonding between cellulose ester and titania particles. The resultant membrane was found to be highly efficient in terms of FO performance and can be utilized for efficient desalinization of water.
Impacts of operating conditions and solution chemistry on osmotic membrane structure and performance
Desalination
Herein, we report on changes in the performance of a commercial cellulose triacetate (CTA) membrane, imparted by varied operating conditions and solution chemistries. Changes to feed and draw solution flow rate did not significantly alter the CTA membrane's water permeability, salt permeability, or membrane structural parameter when operated with the membrane skin layer facing the draw solution (PRO-mode). However, water and salt permeability increased with increasing feed or draw solution temperature, while the membrane structural parameter decreased with increasing draw solution, possibly due to changes in polymer intermolecular interactions. High ionic strength draw solutions may de-swell the CTA membrane via charge neutralization, which resulted in lower water permeability, higher salt permeability, and lower structural parameter. This observed trend was further exacerbated by the presence of divalent cations which tends to swell the polymer to a greater extent. Finally, the calculated CTA membrane's structural parameter was lower and less sensitive to external factors when operated in PRO-mode, but highly sensitive to the same factors when the skin layer faced the feed solution (FO-mode), presumably due to swelling/ de-swelling of the saturated porous substructure by the draw solution. This is a first attempt aimed at systematically evaluating the changes in performance of the CTA membrane due to operating conditions and solution chemistry, shedding new insight into the possible advantages and disadvantages of this material in certain applications.
Forward osmosis (FO) is a promising alternative to reverse osmosis (RO) in membrane-based water desalination. In the current study, carboxylated multiwalled carbon nanotubes (MWCNTs) were incorporated in a polyamide (PA) layer formed on top of a polysulfone porous support, resulting in a thin film nanocomposite (TFN) membrane. The amount of MWCNTs was varied (0.01, 0.05, 0.1, and 0.2 wt/vol %). The FO performance was investigated using deionized water as the feed solution and 2 M NaCl as the draw solution. It was found that the carboxylated MWCNTs enhanced the membrane hydrophilicity, surface roughness, and porosity. Such combined effects are believed to have led to enhanced FO water flux. TFN 0.2 showed the highest FO water flux of 73.15 L/m 2 h, an improvement of 67% compared to the blank thin-film composite (TFC) membrane and significantly better than the values reported in the literature. Direct observation by transmission electron microscopy revealed the presence of some open-ended CNTs favorably oriented across the PA layer. Those are believed to have facilitated the transport of water through their inner cores and contributed to the increase in water flux. However, this was at the expense of salt rejection and reverse solute flux performance. The best performing membrane was found to be TFN 0.01. It exhibited a salt rejection of 90.1% with a FO water flux of 50.23 L/m 2 h, which is 13% higher than the TFC membrane, and a reverse solute flux of 2.76 g/m 2 h, which is 21% lower than the TFC membrane. This TFN 0.01 membrane also outperformed the TFN membranes reported in the literature.