Improved desalination by polyamide membranes containing hydrophilic glutamine and glycine (original) (raw)
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A variety of polyamide thin film composite (PA-TFC) membranes was synthesized via interfacial polymerization (IP) technique. IP was carried out between aqueous solution of m-phenylene diamine (MPD) and trimesoyl chloride (TMC) in dodecane as organic solvent onto polysulfone (PSf) supporting membrane. The characterization of synthesized membranes was conducted using attenuated total reflection Fouier transform infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM) and contact angle measurement. Reverse osmosis performance included permeate flux (L/m2.hr) and salt rejection (%) was evaluated as a function of the synthesis conditions to investigate the optimum conditions that give the best performance membrane. The optimum conditions of synthesized membranes included MPD (1.5 wt.%) for 5 min. soaking time, TMC (0.05 wt. %) in dodecane for 30 sec. reaction time. The best synthesized membrane exhibited high salt rejection (99.81%) with high permeate flux (36.15 L/m2.h). Also, the concentration polarization modulus (M) and the true salt rejection (%) were measured using pure water with different salinities up to ≈ 10000 ppm NaCl feed solution. The obtained results showed that the concentration polarization modulus (M) ranged from 1.06 to 1.29 according to the salinity range.
Advances and challenges in tailoring antibacterial polyamide thin film composite membranes for water treatment and desalination: A critical review, 2024
Thin film composite (TFC) polyamide membranes have been predominantly utilized in water treatment and desalination and play a significant role in the separation processes. However, the occurrence of fouling, especially biofouling, has a detrimental effect on the efficiency of the membrane. The introduction of nanostructures and other surface modification strategies has paved the way for developing antibacterial TFC membranes, aiming to control and mitigate biofouling to achieve a rational design for practical applications. This comprehensive review introduces and discusses novel antibacterial TFC membranes, including their structure, composition, and performance. Additionally, particular attention is given to understanding the antibacterial mechanism of nanomaterials. To this end, various emerging and prevalent antibacterial nanomaterials are introduced, and their role in the fabrication of TFC membranes is overviewed. Moreover, versatile modification strategies are outlined to impart antibacterial activity into TFC membranes. Finally, the review proposes current challenges and prospects of antibacterial TFC membranes, aiming to provide valuable insights for developing advanced TFC membranes with optimal resistance against biofouling and improved separation performance. This critical review serves as a fundamental guide for designing strategies that surpass the current limitations of TFC membranes' antibacterial agents and nanomaterials, thereby mitigating the tendency of biofouling through tailored membrane surface properties.
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.
Drinking Water Engineering and Science
The forward osmosis (FO) process has been considered for desalination as a competitive option with respect to the traditional reverse osmosis process. The interfacial polymerization (IP) reaction between two monomers (i.e., m-phenylenediamine, MPD, and 1,3,5-benzenetricarbonyl chloride, TMC) is typically used to prepare the selective polyamide layer that prevents salts and allows water molecules to pass. In this research, we investigated the effect of preparation conditions (MPD contact time, TMC reaction time, and addition of an amine salt) on the FO performance in terms of water flux and salt flux. The results showed that increasing MPD contact time resulted in a significant increase in the water flux and salt flux. However, increasing TMC reaction time caused a decline in both the water flux and the salt flux. The optimum condition that gave the highest water flux (64 L m −2 h −1) was found to be as 5 min for MPD and 1 min for TMC. The addition of an amine salt of camphorsulfonic acid-triethylamine (CSA-TEA) was able to have an apparent effect on the FO process by increasing the water flux (74.5 L m −2 h −1).
Environmental Science & Technology, 2012
Carboxyls are inherent functional groups of thin-film composite polyamide nanofiltration (NF) membranes, which may play a role in membrane performance and fouling. Their surface presence is attributed to incomplete reaction of acyl chloride monomers during the membrane active layer synthesis by interfacial polymerization. In order to unravel the effect of carboxyl group density on organic fouling, NF membranes were fabricated by reacting piperazine (PIP) with either isophthaloyl chloride (IPC) or the more commonly used trimesoyl chloride (TMC). Fouling experiments were conducted with alginate as a model hydrophilic organic foulant in a solution, simulating the composition of municipal secondary effluent. Improved antifouling properties were observed for the IPC membrane, which exhibited lower flux decline (40%) and significantly greater fouling reversibility or cleaning efficiency (74%) than the TMC membrane (51% flux decline and 40% cleaning efficiency). Surface characterization revealed that there was a substantial difference in the density of surface carboxyl groups between the IPC and TMC membranes, while other surface properties were comparable. The role of carboxyl groups was elucidated by measurements of foulant-surface intermolecular forces by atomic force microscopy, which showed lower adhesion forces and rupture distances for the IPC membrane compared to TMC membranes in the presence of calcium ions in solution. Our results demonstrated that a decrease in surface carboxyl group density of polyamide membranes fabricated with IPC monomers can prevent calcium bridging with alginate and, thus, improve membrane antifouling properties.
Polyamide/polyacrylonitrile thin film composites as forward osmosis membranes
Thin film composites (TFCs) as forward osmosis (FO) membranes for seawater desalination application were prepared. For this purpose, polyacrylonitrile (PAN) as a moderately hydrophilic polymer was used to fabricate support membranes via nonsolvent-induced phase inversion. A selective thin polyamide (PA) film was then formed on the top of PAN membranes via interfa-cial polymerization reaction of m-phenylenediamine and trimesoyl chloride (TMC). The effects of PAN solution concentration, solvent mixture, and coagulation bath temperature on the morphology, water permeability, and FO performance of the membranes and composites were studied. Support membranes based on low PAN concentrations (7 wt %), NMP as solvent and low coagulation bath temperature (0 8C) demonstrated lower thickness, thinner skin layer, more porosity, and higher water permeability. Meanwhile, decreasing the PAN solution concentration lead to higher water permeance and flux and lower reverse salt flux, structural parameter, and tortuosity for the final TFCs. Composites made in N,N-dimethylformamide presented lower permeance and flux for water and salt and higher salt rejection, structural parameter, and tortuosity. FO assay of the composites showed lower water permeance values in saline medium comparing to pure water. V
Journal of Environmental Chemical Engineering, 2017
Membrane fouling is a persistent problem in reverse osmosis (RO) process which leads to higher operating pressure, quality deterioration, and frequent chemical cleaning of the membranes. The objective of this paper is to prepare a fouling-resistant RO desalination membrane while keeping high salt rejection and permeate flux. Polyamide (PA) membranes were prepared and modified using spin assisted Layer-by-Layer assembly of polyelectrolytes (PEI/PAH), characterized and tested in a cross-flow desalination setup. The effect of preparation conditions (number of coating layers, concentration and pH of the polyelectrolyte solutions) on the performance of the membrane was also investigated. SEM micrographs showed that the surface of the PA membrane is rough and has typical ridge and valley structure. However, images of the modified membranes showed smoother surfaces as the number of polyelectrolyte bilayers was increased which was verified using the AFM analysis. In addition, contact angle measurements suggested that the surfaces of the modified membranes became more hydrophilic due to the presence of hydrophilic hydroxyl and amine groups. Permeation results showed comparable salt rejection under saline feed water of 2000 ppm. 50 bilayer modified membrane having 110 mg/L of polyelectrolyte solution, possess permeability of 0.83 L/m 2 h bar with 95% salt rejection. However, 27 bilayer modified membrane having 200 mg/L of polyelectrolyte solution, possess greater permeability of 1.78 L/ m 2 h bar with 96% salt rejection. Fouling experiments showed that after three hours of filtration, functionalized membranes retained more than 88% of water flux compared to pristine polyamide membrane which suffered from more than 42% flux drop.
Polymers, 2017
Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200-35,000 g/mol). This alteration facilitated the formation of a thin polyamide layer on the PSf surface during the interfacial polymerization reaction involving an aqueous solution of piperazine containing 4-aminobenzoic acid and an organic solution of trimesoyl chloride. Attenuated total reflectance-Fourier transform infrared validated the presence of PEG in the membrane support. Scanning electron microscopy and atomic force microscopy illustrated that the thin-film polyamide layer morphology transformed from a rough to a smooth surface. A cross-flow filtration test indicated that a thin-film composite polyamide membrane comprising a PSf support (TFC-PEG20k) with a low surface porosity, small pore size, and suitable hydrophilicity delivered the highest water flux and separation efficiency (J = 81.1 ± 6.4 L•m −2 •h −1 , R Na2SO4 = 91.1% ± 1.8%, and R NaCl = 35.7% ± 3.1% at 0.60 MPa). This membrane had a molecular weight cutoff of 292 g/mol and also a high rejection for negatively charged dyes. Therefore, a PSf support exhibiting suitable physicochemical properties endowed a thin-film composite polyamide membrane with high performance.
Development of novel thin film composite reverse osmosis membranes for desalination
PROCEEDINGS OF THE 2ND INTERNATIONAL CONFERENCE ON BIOSCIENCES AND MEDICAL ENGINEERING (ICBME2019): Towards innovative research and cross-disciplinary collaborations
Microporous Polyetherimide (PEI) membranes were prepared by wet phase inversion at different temperatures. The thin film composites (TFC) of polyamide on microporous PEI were prepared using meta-Phenylenediamine (MPD) and 1,3,5-Benzenetricarbonyl chloride (BTC). The ATR FTIR characterization showed the formation of polyamide (PA) on microporous PEI membrane, whereas scanning electron microscopy (SEM) revealed that a thin film of polyamide is formed on microporous PEI. The cross-sectional SEM of PEI prepared at 60 °C, showed finger like morphology and sparingly distributed balloon like morphology for PEI synthesized at 80 °C. The performance of PEI membranes and PA TFCs were ascertained by studying permeation of water and rejection of sodium chloride by reverse osmosis. The polyamide TFC with hydrophobic PEI support structures exhibited permeation of 28 to 50 lm-2h-1, with 98-95 % 2000 ppm NaCl rejection at 60 bar pressure.
Journal of Membrane Science, 2011
Nanofiltration polyamide membranes obtained by interfacial polymerization possess skin layers containing amine and carboxylic acid groups that are distributed in an inhomogeneous fashion, leading to a bipolar fixed charge distribution (i.e. the sign of the surface charge density changes over the skin layer thickness). In this work we have modified the standard NF model (based on steric/Donnan exclusion and the extended NernstPlanck equation) so as to account for the spatial variations of the fixed charge inside pores. The retention performances 1 of NF membranes having bipolar charge distributions that capture the main electrostatic features of polyamide membranes have been investigated by considering 12, 21 and 11 electrolytes. In the range of volume fluxes usually obtained with NF polymer membranes, calculations show that the theoretical retention sequence of polyamide membranes for the abovementioned electrolytes is 12 > 21 > 11, in agreement with experimental data available in the literature. This retention sequence has been shown to be specific of membranes with bipolar charge distributions since both homogeneously charged membranes and membranes with unipolar charge distributions (i.e. the concentration of charged surface groups can vary over the skin layer thickness but the sign of surface groups remains the same) would be more permeable to asymmetric electrolytes having divalent counterions than to symmetric monomonovalent electrolytes.