An Overview on the Use of Electrolyte Solution as a Strong Osmotic Agent in Forward Osmosis (original) (raw)
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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.
Comparative Study for Organic and Inorganic Draw Solutions in Forward Osmosis
Al-Khwarizmi Engineering Journal, 2017
The present work aims to study forward osmosis process using different kinds of draw solutions and membranes. Three types of draw solutions (sodium chloride, sodium formate, and sodium acetate) were used in forward osmosis process to evaluate their effectiveness with respect to water flux and reverse salt flux. Experiments conducted in a laboratory-scale forward osmosis (FO) unit in cross flow flat sheet membrane cell. Three types of membranes (Thin film composite (TFC), Cellulose acetate (CA), and Cellulose triacetate (CTA)) were used to determine the water flux under osmotic pressure as a driving force. The effect of temperature, draw solution concentration, feed and draw solution flow rate, and membrane types, were studied with respect to water flux. The results showed an increase in water flux with increasing feed temperature and draw solution concentrations In addition, the flux increased with increasing feed flow rate while the flux was inversely proportional with the draw so...
Osmotic's potential: An overview of draw solutes for forward osmosis
Forward osmosis (FO) is a membrane separation process using a highly concentrated draw solution with high osmotic potential to draw water across a semi-permeable membrane from a feed source. This feed source may be seawater, wastewater or other natural or contaminated water sources. Unlike other membrane driven purification processes, the product is not clean water, but a diluted draw solution. As a result a second step is often needed to produce a pure water product. A major advantage of FO is that the low hydrodynamic pressure involved leads to lowered fouling of membranes and greater flux recovery after cleaning, as well as often providing a low energy process which can recover clean water from difficult or highly fouling sources. Selection of an appropriate and effective draw solution is essential for the practical operation of an FO process. This review will give an overview of the theoretical underpinnings of draw solution performance and a comprehensive summary of the current literature regarding the different types of draw solutions which have been investigated and their respective benefits and detriments.
Forward Osmosis Process: State-Of-The-Art of Membranes
Separation & Purification Reviews, 2019
Forward osmosis (FO) is a membrane-based process that explores the osmotic pressure difference between a feed solution and a draw solution to induce water transport across a semipermeable membrane. Water transport results in the dilution of the draw solution which is reconcentrated using a recovery process. Different from the reverse osmosis process, FO requires lower grade energy and has other advantages, namely, a wide range of applications and a reversible fouling phenomenon of FO membranes. In spite of its many advantages, the FO process is facing drawbacks among which the lack of high-performance membranes. Today, the development of improved FO membranes, capable of achieving a high water flux with a very low reverse salt flux is one of the biggest concerns of membrane scientists. This paper summarizes the basic principle of the FO process, some modern applications, and the main challenges related to membranes. It also describes the progresses in FO membrane development, particularly regarding the membrane manufacturing techniques, commercially available, and R&D membranes.
Effect of Surfactant Properties on the Performance of Forward Osmosis Membrane Process
Journal of Ecological Engineering, 2020
Wastewater treatments such as forward osmosis (FO) can be widely applied to separate or the reject substances from secondary treated effluents. Experimental studies have investigated the influence of membrane fouling and operating conditions. The performance of FO is affected by membrane fouling characteristics, composition of the feed solution and operating conditions. The experiments were performed using an osmotic membrane (FO-4040) to investigate the influences of operating conditions on water flux and reverse salt selectivity. The surfactant content, cross-flow velocity, and pH of the feed solution were systematically investigated for their effects on FO performance. The results showed that higher cross-flow velocities, increase of the pH of the feed solution, and adding surfactant into the feed solution yielded higher water fluxes. Reverse salt selectivity also increased after adding a surfactant to the feed solution but showed no significant increase at higher surfactant conc...
Journal of Membrane Science, 2015
The application of semipermeable membranes for dewatering of complex oil and gas wastewaters continues to be a topic of increasing interest. Several studies have explored the fouling propensity and contaminant rejection of osmotically driven membranes during forward osmosis (FO) treatment of produced waters; however, none have investigated changes in membrane transport and physiochemical properties after exposure to these feed streams. In this study we discuss the impacts of produced water exposure on the transport and active layer surface properties of cellulose triacetate (CTA) and polyamide thin-film composite (TFC) FO membranes. While produced water exposure yields some, albeit minor changes to the membrane performance and surface characteristics of the CTA and the traditional TFC membranes, close to 50% reduction in reverse salt flux and contaminant transport was observed for a surface-modified TFC FO membrane; only minimal changes in water permeability were recorded. Results of this study demonstrate the chemical and physical robustness of FO membranes for treatment of oil and gas wastewaters, and they highlight a knowledge gap that exists in membrane polymer selection and contaminant interactions with the membrane polymer matrix that should be further addressed in future membrane fouling studies.
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.
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: Principles, applications, and recent developments
Journal of Membrane Science, 2006
Osmosis is a physical phenomenon that has been extensively studied by scientists in various disciplines of science and engineering. Early researchers studied the mechanism of osmosis through natural materials, and from the 1960s, special attention has been given to osmosis through synthetic materials. Following the progress in membrane science in the last few decades, especially for reverse osmosis applications, the interests in engineered applications of osmosis has been spurred. Osmosis, or as it is currently referred to as forward osmosis, has new applications in separation processes for wastewater treatment, food processing, and seawater/brackish water desalination. Other unique areas of forward osmosis research include pressure-retarded osmosis for generation of electricity from saline and fresh water and implantable osmotic pumps for controlled drug release. This paper provides the state-of-the-art of the physical principles and applications of forward osmosis as well as their strengths and limitations.
Osmotically Driven Membrane Processes - Approach, Development and Current Status
2018
Forward osmosis (FO) is a technical term describing the natural phenomenon of osmosis: the transport of water molecules across a semi-permeable membrane. The osmotic pressure difference is the driving force of water transport, as opposed to pressure-driven membrane processes. A concentrated draw solution (DS) with osmotic pressure draws water molecules from the feed solution (FS) through a semi-permeable membrane to the DS. The diluted DS is then reconcentrated to recycle the draw solutes as well as to produce purified water. As a major disadvantage, nature of FO membranes (asymmetrical structure) causes international concentration polarization (ICP) which promotes the decrease in water flux. Therefore, the number of studies related to improving both active and support layers of FO membranes is increasing in the applications. The purpose of the chapter is to bring an overview on the FO membrane manufacturing, characterizing and application area at laboratory or full scales. This chapter is published in two parts. In the first part, which appears here, the overview of membrane technologies and the definition of forward osmosis process are stated. The manufacturing methods of support and active layers forming FO membranes are described with common and/or new modification procedures.