Effect of salt type on mass transfer in reverse osmosis thin film composite membranes (original) (raw)
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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).
Scaling prevention of thin film composite polyamide Reverse Osmosis membranes by Zn ions
Desalination, 2019
On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn 2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn 2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L•m −2 •h −1) and zinc (30.80 L•m −2 •h −1) ions anti-scalant was higher than the untreated membrane flux (25.56 L•m −2 •h −1), which decreased continuously. membranes, called scaling, as a major concern in water purification processes [4-7]. Scaling occurs when minerals constituents of the feed water precipitate on the surface of the membrane [6,8,9] after they have reached a state of saturation [10,11]. Both mechanisms, participate in the scaling process [3]. Various studies have shown that ionic constituents in feed water in desalination processes may combine under suitable conditions to form salts as CaCO 3 , CaSO 4 , Mg(OH) 2 , BaSO 4 ,
Desalination, 2018
The present paper describes the desalination performance of reverse osmosis (RO) membranes of multi-walled carbon nanotube-polyamide complex (CNT-PA) and commercial polyamide membranes in NaCl, MgCl 2 , MgSO 4 and Na 2 SO 4 aqueous solutions. The permeate flux, salt rejection, and salt flux were determined in a cross-flow experiment. The CNT-PA and commercial RO (PA) membranes (SWC5, Nitto Denko Co.) showed 96.0% and 99.7% salt rejection, respectively, for 0.2% NaCl aqueous solution at 0.7 MPa. The calculated salt flux was 0.38 g•m −2 •h −1 (CNT-PA) and 0.07 g•m −2 •h −1 (SWC5). The salt rejection increased with increasing running pressure and decreasing salt concentration. The zeta potential measurement of CNT-PA demonstrated that it is negatively charged due to the presence of CNT. Accordingly, it showed salt rejection performances against the four salt solutions (Na 2 SO 4 > MgSO 4 > NaCl > MgCl 2) that differed from that of the usual PA membranes (Na 2 SO 4 > MgSO 4 > MgCl 2 > NaCl). These data are explained based on the Donnan model (CNT-PA) and steric hindrance pore model (SWC5), except for the case of chlorides under low-flux or high ionic strength conditions, where the diffusion and molecular size exclusion of the salts dominate over their mas-transport. Positron annihilation lifetime spectroscopy (PALS) enabled the estimation of the pore diameters of these membranes: 0.55 nm (CNT-PA) and 0.58 nm (SWC5).
2019
In this work, we investigate the effect of varying the concentration of sodium chloride up to 70 g.L-1-equivalent to a recovery of approximately 50% in seawater desalination-on the transport properties of different reverse osmosis membranes. The study was performed using five commercial thin film composite (TFC) membranes and an analogue TFC membrane fabricated via the interfacial reaction of m-phenylenediamine and trimesoyl chloride. The surface properties of the membranes as measured by atomic force microscopy (AFM), zeta potential, and X-ray photoelectron spectroscopy (XPS) are presented. The solution diffusion model coupled with film theory was used to calculate the permeance of water and salt through the membranes, to account for the effect of concentration polarisation. The mass transfer coefficient in the test cells was estimated independently using the dissolution rate of benzoic acid; and was found to be approximately 1 × 10 −4 í µí±. í µí± −1. A linear reduction in salt permeance was observed in some of the RO membranes, while it remained constant for other membranes, including the analogue membrane. All the tested membranes maintained constant water permeance below 45 g.L-1 NaCl. However, when the salt concentration at the membrane surface exceeded 45 g.L-1 , water permeance either increased, remained constant or decreased. The results demonstrate the dependence of water and salt transport on the concentration of sodium chloride at the membrane surface. 1. Introduction Thin film composite (TFC) membranes formed via the interfacial polymerisation of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on a polysulfone or polyethersulfone ultrafiltration support are the most widely used membranes in water treatment and desalination. This is due to the reliability and relatively low-cost of the interfacial polymerisation technique in producing membranes with excellent separation properties and a wide variety of surface properties [1]. This enables the utilisation of TFCs in reverse osmosis water desalination systems with feed solutions ranging from low-salinity fresh and brackish water (~2-10 g.L-1 NaCl) to high-salinity seawater (~35 g.L-1 NaCl). Since, it is common to operate RO plants with overall recoveries around 50% [2], the membrane elements in a seawater reverse osmosis (SWRO) plant are subjected to salt concentrations in the feed between 35 to 70 g.L-1 from the entry point until the solution exits the RO spiral wound elements.
Desalination, 2012
Thin film composite (TFC) polyamide membranes for reverse osmosis (RO) were successfully prepared via interfacial polymerization of m-phenylenediamine (MPD), 2,2′-benzidinedisulfonic acid (BDSA) and trimesoyl chloride (TMC) on a polysulfone support. The physico-chemical characteristics of the membranes were determined using ATR-FTIR, XPS, zeta potential measurement, SEM and AFM. Membrane performance experiments were investigated using NaCl and MgCl 2 salt solutions. The near region spectra show that the active layer of TFC membrane is an aromatic polyamide, with carboxyl and amino groups, as seen in the ATR-FTIR result. The sulfonyl group addition from the BDSA monomer is evident from the higher sulfur concentration as illustrated in the XPS results and due to more negative zeta potential values. Also, the SEM and AFM pictures show that the surface morphology became smoother as the BDSA content was increased. Due to the modification of the active layer, pure water permeability and rejection of NaCl and MgCl 2 salts were significantly enhanced.
Thin film composite reverse osmosis membrane development and scale up at CSMCRI, Bhavnagar
Desalination, 2011
Thin film composite (TFC) reverse osmosis membrane containing polyamide active layer on porous polysulfone support was developed at the scale of 1 m width × 100 m long in a batch using semi-automated mechanical casting and coating machines. The polysulfone support was made according to phase inversion method at the rate of 3−6 m/min., and the polyamide active layer on the polysulfone support was prepared by interfacial polymerization method at the rate of 0.3−0.5 m/min under different conditions. Since desalination of brackish water does not require the membrane with very high salt rejection efficiency, emphasis was placed on increase in the flux while maintaining the salt rejection at 94± 2%. The membrane preparation conditions and structure−performance relationships were correlated by different techniques like porometry, infrared spectra, scanning electron microscopy and atomic force microscopy. The TFC membranes exhibited 94−96% salt rejection with water flux of 50− 65 L/m 2 .h when tested with 5000−1500 ppm salt solution at 250 psi. Surface modification of the TFC membrane with polymers containing hydrophilic groups was carried out to impart fouling resistance. Spiral modules of 4040 and 8040 size were made and tested them extensively in the field conditions in 500−2000 LPH brackish and sea water desalination plants.
Salt and water transport in reverse osmosis thin film composite seawater desalination membranes
Desalination, 2015
• Reverse osmosis (RO) desalination • Transport through RO membranes, solution diffusion model • Concentration polarization in RO Thin film composite membranes • Salt and water transport mechanisms in RO membranes a b s t r a c t Over several decades, membrane transport has developed into established field in membrane science and technology. Two different approaches i.e., irreversible thermodynamic model (ITM) and solution diffusion model (SDM) has been thoroughly discussed in the literatures however due to its simplicity and applicability in the area of reverse osmosis desalination membrane, only SDM is chosen and discussed in this work. Recent experimental works are systematically presented for directly or indirectly validating the model.
Desalination, 2008
Water scarcity is becoming a serious problem in the Mediterranean countries. To minimize negative effects, wastewater reclamation can be one of the possible solutions. Reverse osmosis (RO) is the process that ensures the highest water quality. Thus, the required quality goal can be reached adjusting the wastewater portion to be treated and the portion directed to the blending tank. In this work, a study with a low-pressure RO pilot plant was conducted in the laboratory. A spiral wound composite polyamide membrane (ESPA1-2540, Hydranautics) with an active area of 2.59 m 2 was tested for increasing volume concentration factors (VFC). Thus, the membrane elements behaviour within a pressure vessel in a full-scale plant was simulated. The experiments were run three times to confirm statistically the results. These ones showed an almost constant permeate flux (17 L m −2 h −1) while keeping the transmembrane pressure constant at 6.8 bar with a VCF of 2.5. Concerning the salt retention, it was observed a slightly reduction on increasing the VFC. However, the permeate conductivity was lower than 80 µS/cm in all cases.
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 and Research, 2019
During interfacial polymerization (IP) reaction between m-phenylenediamine (MPDA) and trimesoyl chloride (TMC), a by-product, i.e. hydrochloric acid can produce. This produced acid diffuses back in aqueous phase and protonates MPDA and reduces its reactivity that results in lowering of polymer yield and performance of membrane. Further, for getting consistency in reverse osmosis membranes formation, different acid acceptors (AAs) can investigate in the IP to form polyamide-made barrier layer formation. The main objective was to scavenge hydrochloric acid produced during IP and to fabricate membrane having high flux and salt rejection ability. AAs (of varying concentrations) tested were triethylamine-camphorsulfonic acid (TEACSA), triphenyl phosphate (TPP), sodium hydroxide (SH) and trisoduim phosphate (TSP) for studying structure and performance of membranes. The membrane samples were then characterized using surface proflometer, scanning electron microscopy (SEM), Energy-dispersive X-...