Preparation and assessment of polyvinylidene fluoride hollow fiber membrane for desalination by membrane distillation (original) (raw)
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Membranes, 2021
Hollow fiber membranes of polyvinylidene fluoride (PVDF) were prepared by incorporating varying concentrations of hydrophilic surface-modifying macromolecules (LSMM) and a constant amount of polyethylene glycol (PEG) additives. The membranes were fabricated by the dry-wet spinning technique. The prepared hollow fiber membranes were dip-coated by hydrophobic surface-modifying macromolecules (BSMM) as the final step fabrication. The additives combination is aimed to produce hollow fiber membranes with high flux permeation and high salt rejection in the matter of seawater desalination application. This study prepares hollow fiber membranes from the formulation of 18 wt. % of PVDF mixed with 5 wt. % of PEG and 3, 4, and 5 wt. % of LSMM. The membranes are then dip-coated with 1 wt. % of BSMM. The effect of LSMM loading on hydrophobicity, morphology, average pore size, surface porosity, and membrane performance is investigated. Coating modification on LSMM membranes showed an increase in ...
Separation and Purification Technology, 2009
The mixture of inorganic salt LiCl and soluble polymer polyethylene glycol (PEG) 1500 as non-solvent additive was introduced to fabricate hydrophobic hollow fiber membrane of polyvinylidene fluoride (PVDF) by phase inversion process, using N,N-dimethylacetamide (DMAc) as solvent and tap water as the coagulation medium. Compared with other three membranes from PVDF/DMAc, PVDF/DMAc/LiCl and PVDF/DMAc/PEG 1500 dope solution, it can be observed obviously by scanning electron microscope (SEM) that the membrane spun from PVDF/DMAc/LiCl/PEG 1500 dope had longer finger-like cavities, ultra-thin skins, narrow pore size distribution and porous network sponge-like structure owing to the synergistic effect of LiCl and PEG 1500. Besides, the membrane also exhibited high porosity and good hydrophobicity. During the desalination process of 3.5 wt% sodium chloride solution through direct contact membrane distillation (DCMD), the permeate flux achieved 40.5 kg/m 2 h and the rejection of NaCl maintained 99.99% with the feed solution at 81.8 • C and the cold distillate water at 20.0 • C, this performance is comparable or even higher than most of the previous reports. Furthermore, a 200 h continuously desalination experiment showed that the membrane had stable permeate flux and solute rejection, indicating that the as-spun PVDF hollow fiber membrane may be of great potential to be utilized in the DCMD process.
Development of antifouling thin-film-composite membranes for seawater desalination
Journal of Membrane Science, 2011
The present contribution provides detailed information about the development of antifouling novel thin-film-composite (TFC) membranes for mostly water purification with special emphasis on seawater desalination in particular. The novel membranes were prepared by incorporating in-situ hydrophilic surface modifying macromolecules (iLSMM) into the TFC membranes, rendering the surface of the TFC membranes significantly more hydrophilic. The prepared membranes were then subjected to long term fouling studies using model foulants, including sodium humate (SH), silica particles (SPs), and chloroform (CF) spiked in the feed NaCl solution. The biofouling effect of silver salts was also studied by incorporating some silver salts (silver citrate hydrate, SCH; silver lactate, SL; and silver nitrate, SN) simultaneously with iLSMM into the TFC membranes. Halo test was conducted with Escherichia coli to examine the antibiofouling performance of the silver incorporated TFC membranes. It can be concluded by this work that iLSMM incorporated TFC membranes have performed excellently for the desalination of salty water (3.5 wt% NaCl), especially when the solution was spiked with typical foulants such as SH, SPs, and CF. The flux reduction was reduced significantly when iLSMM was incorporated in the TFC membranes by a newly developed technique. The antimicrobial fouling intensity of the studied membrane was in the order of: SN (ring width 0.55 mm) > SL (0.27 mm) > SCH (0.19 mm).
2019
This research aimed to improve the hydrophobic polyvinylidene fluoride (PVDF) membrane for direct contact membrane distillation (DCMD) desalination by mixing various additives (dibutyl phthalate and glycerol) in polymer solution via twostage/dual coagulation bath (CB) system. The effect of each additive on the surface and cross-sectional morphology of PVDF membrane was investigated. The addition of additives showed increased in membranes porosity, but the water contact angle was less than 90° when immersed in single CB (distilled water). Membrane prepared with two-stage CB system immersed into methanol CB for 20 min and transferred into distilled water CB for 24 h exhibited high water contact angle of 114.2°, 142.6° and 120.1° for membrane M-3, M-4 and M-5, respectively. The porosity of membrane significantly increased when incorporated with additives. The membrane was further evaluated in DCMD operation for separation performance. The DCMD tested using distilled water and 35 g l–1 ...
Chemical Engineering and Processing - Process Intensification, 2020
Cellulose acetate based membranes are used for water desalination. Cellulose diacetate (CDA) was prepared from cellulose powder. Reverse osmosis (RO) membranes were prepared on polyester sheets using CDA based through phase inversion technique. The structural, morphological and hydrophilic properties of the prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), Nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and contact angle measurements. The FTIR and NMR revealed the presence of the carbonyl groups and degree of substitution (DS) in CDA. Modified membranes by Grafted to improve the performance and the anti-biofouling properties of cellulose acetate reverse osmosis (RO) membranes. The antibiofouling properties were studied by measurements of static protein adsorption. The effect of grafting the membrane on the salt rejection and water flux was studied using a cross flow RO unit. The results indicated that 15 wt% of 2-acrylamido-2-methylpropanesulfonic acid (AMPS)Grafted membranes have lower adsorption of protein and microbes, in addition to increased salt rejection to 99.24 % and water flux to 17.12 l/m 2 h.
Biofouling in reverse osmosis membranes for seawater desalination: Phenomena and prevention
2011
Reverse osmosis membranes are becoming increasingly popular for water purification applications that require high salt rejection such as brackish and seawater desalination. However, due to fouling by microorganisms, they have been unable to realize their full potential as of yet. Biofouling leads to the use of higher operating pressure, more frequent chemical cleaning, and shorter membrane life. This paper reviews the causes, consequences and control of biofouling in RO membranes used for seawater desalination. After a brief introduction, the fundamentals of biofouling are discussed in some detail: biofilm formation, role of EPS, and sequence of events leading to biofouling. This is followed by a section on consequences of biofouling on membrane processes with particular emphasis on water permeability and salt rejection. The mechanisms of performance degradation are discussed in some detail for both of these parameters. The last section of this paper reviews the different antifouling strategies that have recently gained more attention with special emphasis on membrane surface modification. A brief conclusion with some recommendations and suggestions is presented at the end of the article.
Membranes
In this work, the efficiency of a conventional chlorination pretreatment is compared with a novel modified low-fouling polyethersulfone (PES) ultrafiltration (UF) membrane, in terms of bacteria attachment and membrane biofouling reduction. This study highlights the use of membrane modification as an effective strategy to reduce bacterial attachment, which is the initial step of biofilm formation, rather than using antimicrobial agents that can enhance bacterial regrowth. The obtained results revealed that the filtration of pretreated, inoculated seawater using the modified PES UF membrane without the pre-chlorination step maintained the highest initial flux (3.27 ± 0.13 m3·m−2·h−1) in the membrane, as well as having one and a half times higher water productivity than the unmodified membrane. The highest removal of bacterial cells was achieved by the modified membrane without chlorination, in which about 12.07 × 104 and 8.9 × 104 colony-forming unit (CFU) m−2 bacterial cells were ret...
Desalination Performance of Antibiofouling Reverse Osmosis Membranes
Modern Environmental Science and Engineering
The use of reverse osmosis membranes (RO) is the most used technology for water desalination; however, membrane biofouling is considered a critical issue affecting desalination plants. The incorporation of nanoparticles with antimicrobial properties into RO membranes has been reported as an effective route for enhancing the antibiofouling properties but could diminish the performance of desalination. The aim of this work was to study the performance of antibiofouling of thin film composite (TFC-RO) membrane by incorporating antimicrobial copper-oxide (CuO) nanoparticles. These nanoparticles were incorporated within the structure of the membrane during the interfacial polymerization process. The membranes were characterized by scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscope (EDX) and atomic force microscopy (AFM) in order to observe the morphology and verify the incorporation of nanoparticles within them. Bactericidal tests were performed using Escherichia coli. Anti-adhesion on the membranes was confirmed using epifluorescence microscopy. Membranes performance were evaluated in terms of permeate flux and salt rejection by using a cross flow test cell. FESEM and EDX analyses confirmed the incorporationof nanoparticles into the membrane. These membranes showed significant anti-bacterial and excellent anti-adhesion effect attributed to the copper toxicity. Desalination performance of modified membranes showed an important salt rejection of about 98% with stable water flux about 36 L.m −2 .h −1 and a recovery of 50%. Measure copper concentrations in the permeate water shows to be negligible, indicating that the copper is not leached. In conclusion, the incorporation of CuO nanoparticles into TFC-RO membranes improves the antibiofouling capacities without impairing the performance of the membrane.
Journal of Membrane Science, 2010
In order to evaluate the effect of membrane surface properties on the initial stage of biofouling, in the reverse osmosis (RO) membrane process, initial bacterial adhesion and biofilm formation experiments were performed under no filtration condition. In this study, five commercialized polyamide thin-film composite RO membranes (SW30HRLE, SW30HR (Dow FilmTec Co., USA), TM820 (Toray Co., Japan), RE-BE, RE-FE (Woongjin Chemical Co., Korea)) were chosen and their surface properties such as surface charge, roughness, hydrophobicity and surface morphology were measured. For examining initial bacterial adhesion, a flow channel reactor was employed for 3 h, while for examining a biofilm formation, the CDC reactor was employed for 48 h. Pseudomonas aeruginosa PAO1 tagged with GFP was selected as a model bacterial strain. Major findings in this study indicate that although the initial bacterial cell adhesion in a flow channel reactor indicated more bacterial cells attachment on the membrane surface with higher hydrophobicity, the extent of biofilm grown in CDC reactor for 48 h became similar regardless of the difference of the membrane surface properties, indicating that the membrane surface properties become a less important factor affecting the biofilm growth on the membrane surface. This finding will be helpful in improving the understanding of biofouling issue occurring in the real RO membrane system, although practical implication is somewhat limited since this study was performed under no filtration condition.
Surface Treatment of Polymer Membranes for Effective Biofouling Control
Membranes
Membrane biofouling is the consequence of the deposition of microorganisms on polymer membrane surfaces. Polymeric membranes have garnered more attention for filtering and purifying water because of their ease of handling, low cost, effortless surface modification, and mechanical, chemical, and thermal properties. The sizes of the pores in the membranes enable micro- and nanofiltration, ultrafiltration, and reverse osmosis. Commonly used polymers for water filter membranes are polyvinyl chloride (PVA), polyvinylidene fluoride (PVDF), polyamide (PA), polyethylene glycol (PEG), polyethersulfone (PES), polyimide (PI), polyacrylonitrile (PAN), polyvinyl alcohol (PA), poly (methacrylic acid) (PMAA), polyaniline nanoparticles (PANI), poly (arylene ether ketone) (PAEK), polyvinylidene fluoride polysulfone (PSF), poly (ether imide) (PEI), etc. However, these polymer membranes are often susceptible to biofouling because of inorganic, organic, and microbial fouling, which deteriorates the mem...