Behavior of Volatile Compounds in Membrane Distillation: The Case of Carboxylic Acids (original) (raw)
Related papers
Journal of Molecular Liquids, 2017
Separation of carboxylic acids from aqueous solutions using synthetic membranes has been investigated within the context of this study. Formic, glycolic, malic, and citric acid aqueous solutions were prepared in the experiments as mixtures to be separated. Nanofiltration (NF) and reverse osmosis (RO) membranes were used for the separation of acid solutions. The experiments were carried out on a pilot scale membrane unit allowing the use of membranes with a surface area of 140 cm 2. Experiments were performed by using different initial acid concentrations (5-15 % w.) at 10, 20, 30 bar and 20 o C. Thus, the effects of pressure, the type of membrane and acids were analysed on the separation performance by using single acid solutions, and model equations were formed with the help of response surface methodolgy (RSM) in the case of citric acid, which has the highest rejection ratio. As a result of the experimental studies carried out, very high rejection values (max. 98.36 %) were obtained and it was seen that the carboxylic acids were successfully separated from the aqueous media.
Air gap membrane distillation technique (AGMD) was applied for removal of ethanol, butanol and acetone–butanol–ethanol mixture from water. The influence of various parameters (feed temperature, cooling wall temperature) on pure water transport in AGMD was determined and the efficiency of organic solvents removal from water through two porous membranes (PTFE and PP) was investigated in the detail. Selectivity of organic components recovery did not change significantly with an increase of feed temperature from 41 °C to 63 °C in case of AGMD applied for ethanol and butanol recovery, however significantly higher fluxes were obtained at higher feed temperature. Slightly higher fluxes were obtained during experiments performed with PTFE membrane comparing with PP one. It was found that both PTFE and PP membranes are wetted during AGMD process of water–butanol feed mixture if organic concentration exceeds 2.5 wt% (PTFE) and 1 wt% (PP) at 63 °C feed temperature. This fact limits the possibility of wider AGMD application in organic solvent recovery. The comparison of the efficiency of AGMD with the efficiency of thermopervaporation (TPV) was also performed. In case of 1 wt% ethanol feed mixture it was found that AGMD seems to be more suitable due to higher process separation index value (PSI in the range of 6 kg m À 2 h À 1) than in the case of TPV (PSI in the range of 3 kg m À 2 h À 1). On the contrary, in the case of water–butanol or water–ABE systems TPV is much more efficient method for organics recovery from aqueous mixtures than AGMD. In contact with 3 wt% ABE mixture PSI is equal to 28 and 9 kg m À 2 h À 1 for TPV and AGMD processes, respectively.
Membrane distillation: A comprehensive review
Desalination
Membrane Distillation (MD) is a thermally-driven separation process, in which only vapour molecules transfer through a microporous hydrophobic membrane. The driving force in the MD process is the vapour pressure difference induced by the temperature difference across the hydrophobic membrane. This process has various applications, such as desalination, wastewater treatment and in the food industry. This review addresses membrane characteristics, membrane-related heat and mass transfer concepts, fouling and the effects of operating condition. State of the art research results in these different areas will be presented and discussed.
Evolution of Membrane Surface Properties for Membrane Distillation: A Mini Review
Journal of Applied Membrane Science & Technology
To date, the membrane development for membrane distillation (MD) application is growing in line with the increasing volume of various types of wastewaters discharged into environment. MD is a liquid-vapor separation process and a hydrophobic membrane is used to retain the liquid. Theoretically, the hydrophobic membrane can achieve 100% rejection of non-volatile components that dissolved in feed liquids. As a result, MD has received significant attention in water recovery from saline water as well as wastewaters. Nevertheless, in addition to the scaling problem due to salts, the hydrophobicity property of membrane becomes a concern when dealing with challenging wastewaters which contain various types of low surface tension components such as oils, grease, alcohols, organics and surfactants. The membrane pore wetting due to salts deposition fouling and low surface tension components subsequently reduces the flux and even fails the liquid-vapor separation process. This article briefly ...
Potential of membrane distillation - a comprehensive review
International Journal of Water, 2013
Membrane distillation (MD) is a recent and unique separation technology, in use in the process industry. The process of separation in MD involves the simultaneous heat and mass transfer through a hydrophobic semi permeable membrane, using thermal energy. Consequently a separation of the feed solution into two components-the permeate or product and the retentate or the return stream occurs. MD utilises low grade or alternative energy, e.g., solar energy, geothermal energy, etc., as a source and is the most cost effective separation technology. Hence the process has come to acquire the attention and interest of researchers, experimentalists and theoreticians all over the world. This article is a comprehensive review of the prominent research in the field of MD technology, including its basic principle, MD configurations, area of applications, membrane characteristics and modules, experimental studies involving the effect of main operating parameters, MD energy and economic, fouling and long-term performance.
Vacuum membrane distillation: Experiments and modeling
AIChE Journal, 1997
Vacuum membrane distillation is a membrane-based separation process considered here to remove volatile organic compounds from aqueous streams. Microporous hydrophobic membranes are used to separate the aqueous stream from a gas phase kept under vacuum. The evaporation of the liquid stream takes place on one side of the membrane, and mass transfer occurs through the vapor phase inside the membrane. The role of operative conditions on the process performance is widely investigated in the case of dilute binaly aqueous mixtures containing acetone, ethanol, isopropanol, ethylacetate, methylacetate, or methylterbutyl ether. Temperature, composition, flow rate of the liquid feed, and pressure downstream the membrane are the main operative variables. Among these, the vacuum-side pressure is the major design factor since it greatly affects the separation eficiency. A mathematical model description of the process is developed, and the results are compared with the experiments. The model is finally used to predict the best operative conditions in which the process can work for the case of benzene removal from waste waters.
Membrane Distillation for Desalination and Other Separations
Recent Patents on Chemical Engineering, 2010
Membrane distillation is an emerging membrane technology used for desalination of seawater or brackish water, solution concentration, recovery of volatile compounds from aqueous solutions and other separation and purification processes. Membrane distillation differs from other membrane technologies in that the driving force for separation is the difference in vapor pressure of volatile compound across the membrane, rather than total pressure. The main advantage of membrane distillation over the conventional thermal distillation is that membrane distillation could occur at a much lower temperature than the conventional thermal distillation. The membranes used in membrane distillation are hydrophobic, which allow water vapor to pass through but not liquid solution. The vapor pressure gradient is created by heating the feed solution and cooling/purging the condensate in the permeate side. Therefore, membrane distillation enables separation to occur below the normal boiling point of the feed solution and could utilize low-grade heat from alternative energy sources. The objective of this review is to cover the basic principles and configurations of membrane distillation process, membrane physical characteristics, heat and mass transfer characteristics, and the effect of operating conditions. Also, major applications of this new technology in desalination, food industry and environmental protection, and latest patent developments and future trend in membrane distillation are presented.
Membrane distillation: theory and experiments
Journal of Membrane Science, 1996
A theoretical approach is presented that describes membrane distillation processes due to the simultaneous action (in a proactive or in a counteractive way) of temperature and concentration differences through porous hydrophobic membranes. The model developed emphasizes the importance of the boundary layers, shows the existence of a coupling term between the two thermodynamic forces acting on the system, and permits the definition and characterization of the so-called steady states. In order to check the model, two membranes have been studied in different experimental conditions. The influence of some relevant parameters, such as solution concentration, stirring rate, mean temperature and temperature difference has been considered and the theoretical predictions of the model have been applied to the obtained results. The accordance may be considered good.
Membrane Distillation: A cost effective process’
Membrane Distillation (MD) is a thermally-driven separation process, in which only vapour molecules transfer through a microporous hydrophobic membrane. The driving force in the MD process is the vapour pressure difference induced by the temperature difference across the hydrophobic membrane. This process has various applications, such as desalination, wastewater treatment and in the food industry. This review addresses membrane characteristics, membrane-related heat and mass transfer concepts, fouling and the effects of operating condition. State of the art research results in these different areas will be presented and discussed.
Effect of surfactant hydrophobicity and charge type on membrane distillation performance
Journal of Membrane Science, 2019
Highlights • Five surfactants with different hydrophobicities and charge types were investigated • Molecular dynamics simulations were carried out to explain experimental MD results • Most hydrophobic surfactant gave worst performance due to surfactant-PVDF affinity • For different charges, worst MD performance was tied to water-membrane affinity • Effect of NaCl depended on surfactant type