Nanofiltration of highly concentrated salt solutions up to seawater salinity (original) (raw)
Related papers
Rejection of salt mixtures from high saline by nanofiltration membranes
Korean Journal of Chemical Engineering, 2009
Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated (NaCl) salt solutions up to 25,000 ppm, a salinity level similar to that of seawater. The membranes were firstly characterized using the Atomic Force Microscopy (AFM) technique. Pore size and pore size distribution obtained from AFM measurements were used to analyse both experimental data of pure water permeation and data obtained from salt rejection. The main parameters studied in this paper are feed pressure and salt concentration. The experimental data of this work was correlated and analysed using the Spigler-Kedem model. In particular, the reflection coefficient () of all studied membranes and the solute permeability of the salt (P s ) have been determined for all membranes and at all salinity levels studied. For a salinity of 5000 ppm and a pressure of 9 bars, the experimental results showed that NF90 could achieve a salt rejection up to 95%, whereas its rejection dropped to 41% at a salinity of 25,000 ppm and the same pressure. Rejection levels achieved by NF270 have been in range of 11-29%, while N30F gave the lowest rejection in the range of 3-6%.
NF Membrane Characterization for Hybrid Desalination Applications
Doosan is in the process of evaluating the performance of Nano-Filtration (NF) membranes for pre-treatment applications in tri-hybrid desalination systems (NF/RO/Thermal). The interest in NF stems from its potential for removing polyvalent ions and uncharged solutes, including sulfates and salinity and in reducing seawater desalination costs. Potential applications include hybrid configurations such as NF/RO, NF/NF, NF/MSF, NF/MED or a combination thereof. In order to assure efficient utilization of NF membranes, proper understanding of their characteristics and performance is needed. This paper reviews the fundamental theories and driving mechanisms behind NF operation and presents some recent test results on NF solute reject characteristics. Lab-scale tests were conducted on GE-Osmonics membranes, using sodium and magnesium chloride, representing charged solutes, and Glucose representing uncharged solutes. The results show a strong pH effect on solute rejection. It is also argued ...
Alfarama Journal of Basic & Applied Sciences, 2021
In view of the typical results obtained from pilot plan unit, a trial on the nanofiltration (NF) demonstration unit is not only logical but also essential to determine the conditions of the operations such as feed pressure and permeate TDS. A significant progress is made in understanding the effect of the feed temperature on the nanofiltration performance by using different concentrations of saline water that cover both high salinity brackish water and the seawater range 10K ppm, 20K ppm, 30K ppm and 40K ppm. A complete demonstration unit is constructed in this research applying a NF spiral wound membrane manufactured by Filmtec company type NF90-2540 that shows a high salt rejection. The simulation' runs by the latest simulation software; WAVE by Filmtec company were compared with the experimental results. The permeability percentage of the nano polymer for both monovalent ions such as sodium and chloride ions and the divalent ions such as calcium, magnesium and sulphate ions are discussed in this study as well. It was observed that feed pressure decreased with increasing feed temperature and decreasing feed TDS. Moreover, the salt rejection decreased with increasing feed temperature and feed TDS. The feed pressure results of NF90-2540 proved that the NF power consumption is lower than RO.
Intrinsic properties and performances of NF270 and XLE membranes for water filtration
Water Supply, 2011
Nanofiltration and low pressure reverse osmosis membranes are well-known in the field of drinking water production and their separation performance is very strongly related to their intrinsic characteristics. The membrane characterization (scanning electron microscopy (SEM), atomic force microscopy (AFM), zeta potential …) was realized on a NF270 and extra-low energy (XLE) membrane. SEM results of virgin NF270 and XLE membranes show that both are about the same thickness whereas that of the active layer of NF270 membrane is weaker than that of the XLE. The AFM measurements show that the roughness of the low pressure reverse osmosis membrane (XLE) is almost 20 times as high as that of nanofiltration (NF270). Zeta potential measurements showed that both membranes are negatively charged in pH (4–12) range. An increase in permeability by increasing feed pressure and temperature was also noted for the two types of membrane; but the permeability evolution for XLE membrane according to the...
Effect of feed temperature on the performance and properties of the NF270 membrane
2016
An experimental study was done to explore the effect of feed water temperature on the properties and performance of nanofiltration membranes. The NF270 membrane was selected for this study, in which two temperatures of feed solution were passed through the membrane and water flux and salt rejection were measured. Results from fitting with experimental data show that water flux increased 23% and salt rejection changed minimally from 25*C to 40'C. A numerical fitting method used the experimental data to determine the parameters of the membrane: pore radius, effective active layer thickness, and volumetric charge density. From 25'C to 40*C, the fitted parameters showed a 29% increase in pore size, and an 84% increase in effective active layer thickness; volumetric charge density increased in magnitude by approximately 64%. Pre-compaction and pre-soaking the membrane in alcohol are two separate membrane pretreatment procedures that showed significant effects on the performance o...
DESALINATION AND WATER TREATMENT, 2021
The objective of this manuscript is to investigate experimentally and theoretically the effect of ion (cation and anion) valence and concentration on the rejection coefficient and solute permeability of NF270 membrane. The experimental data of solute rejection vs. permeate flux is usually fitted to Spiegler-Kedem equation to determine the reflection coefficient and the solute permeability. In doing so, many problems may arise such as inaccurate numerical fitting, the discrepancy in the results when the different initial guess is made and sometimes no result is obtained. The current research work overcomes these problems by transferring the Spiegler-Kedem equation to a one-parameter equation. This is done by first using the flux equation to determine the rejection coefficient and use this data in the Spiegler-Kedem equation to determine the solute permeability. The success of this procedure was confirmed by comparing its results with those available in open literature where an excellent agreement was found. Moreover, the values of the reflection coefficient and the solute permeability that some researchers could not determine were found. The interaction between the solutes especially at high concentrations was taken into account when the osmotic pressure was calculated. The experimental results showed that σ is inversely proportional to the concentration. P s , however, are proportional to the concentration until a certain concentration is reached after which the effect diminishes. The results also show that as the valence of the cation increases both σ and P s increase. The results showed that AlCl 3 has the highest value of σ and NaCl has the lowest value. The values of σ follow the following order: σ σ σ σ AlCl MgCl Na SO NaCl 2 4 3 2 > > >. The dependence of P s on the solute type follows the following order P s,NaCl > P s,Na 2 SO 4 > P s,MgCl 2 > P s,AlCl 3 .
Desalination, 2015
Applicability of NF as a pre-treatment of SWRO desalination process • The highest permeate flux with NF90 + SW30-RO combination • The lowest permeate flux with NF270 + SW30-RO combination • The best permeate quality with NF90 + SW30-RO combination a b s t r a c t In this study, the applicability of nanofiltration (NF) was investigated as a pre-treatment stage of reverse osmosis (RO) process for seawater desalination. The desalination performance of such integrated system was checked. Previously, NF (NF90 and NF270) and SWRO (SW30) membranes were used individually in the close-loop operation. Next, the NF permeate was collected using NF membrane by a continuous operation and then this permeate was used as a feed for a closed-loop SWRO system. The performances of single SWRO, NF and NF + RO integrated systems were compared in terms of permeate qualities and quantities. The results showed that permeate recovery of NF270 membrane was higher than that of NF90 membrane. However, the salt rejection of NF90 membrane was better than that of NF270. The single SW30-RO membrane showed an average rejection of 98.2% for salinity, while the permeate recovery value was only 28% at 55 bar. Also the average permeate flux of single SW30-RO membrane was 30.1 L/h m 2 . For the integrated system experiments, the highest permeate flux was found with NF90 (30 bar) + SW30-RO (40 bar) combination. Similar permeate flux values were obtained with single SW30-RO and NF90 (30 bar) + SW30-RO (30) bar combination. The lowest permeate flux was found with NF270 (30 bar) + SW30-RO (40 bar) combination. Salinity was also highly rejected by all integrated system combinations. Permeate recovery values of integrated system combinations showed similar trend with permeate flux. Regarding permeate quality, it was seen that all integrated system combinations were better than single SW30-RO membrane. It was obtained that the permeate quality with NF90 + SW30-RO combination was better than that with NF270 + SW30-RO combination.
Journal of Membrane Science and Research, 2020
In this study, the applicability of nanofiltration (NF) membranes as a pretreatment prior to reverse osmosis (RO) in seawater desalination was investigated. The membranes used wereNF270 and NF90 as the NF membranes, while the brackish water (BW) RO membrane BW30 was used as the RO membrane. In desalination tests, permeates of the NF membraneswere collected and used as the feed to the BW30 membrane. The calculated permeate fluxes were 6.7 L/h.m2, 11.3 L/h.m2, 24.3 L/h.m2, and 36.6 L/h.m2 for single BW30-35 bar,NF270-30 bar + BW30-35 bar, NF90-30 bar + BW30-25 bar and NF90-30 BW30-35 bar, respectively. The calculated water recovery and rejected salt values were 51.6%, 41.4%,24.8%, 15.4% and 98.2%, 98.2%, 96.0%, 91.0% for NF90-30 bar + BW30-35 bar, NF90-30 bar + BW30-25 bar, NF270-30 bar + BW30-35 bar and single BW30-35 bar, respectively.The qualities of the product waters of integrated systems (NF+BWRO) and the single BWRO system were also investigated. Boron rejection was fairly well...
Desalination, 2004
Nanofiltration membranes (NF) have applications in several areas. One of the main applications has been in water treatment for drinking water production as well as wastewater treatment. NF can either be used to treat all kinds of water including ground, surface, and wastewater or used as a pretreatment for desalination. The introduction of NF as a pretreatment is considered a breakthrough for the desalination process. NF membranes have been shown to be able to remove turbidity, microorganisms and hardness, as well as a fraction of the dissolved salts. This results in a significantly lower operating pressure and thus provides a much more energy-efficient process. Similar to other membrane processes, a major problem in NF membrane applications is fouling. Several studies have investigated the mechanisms of fouling in NF membranes and suggested methods to minimize and control the fouling of NF membranes. For NF membrane characterizations and process prediction, modeling of NF processes and the use of atomic force microscopy (AFM) are very important. The ability to predict the performance of NF processes will lead to a lower number of experiments, saving of time and money, and help to understand the separation mechanisms during NF. A comprehensive review of NF in water treatments is presented including a review of the applications of NF in treating water as well as in the pretreatment process for desalination; the mechanism as well as minimization of NF membrane fouling problems; and theories for modelling and transport of salt, charged and noncharged organic compounds in NF membranes. The review will also address the application of AFM in studying the morphology of membrane surfaces as part of the NF membrane characterization.