No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Ionic liquids as a carrier for chloride reduction from brackish water using hollow fiber renewal liquid membrane
Abstract
High concentration of chloride ions in continental water is a great problem for the exploitation of these natural
resources. In industry, the use of thiswater involves additional conditioning steps. For drinking water and irrigation uses, the Cl− must be reduced by conventional water treatment processes, like ion exchange or reverse osmosis, but for large scale production these techniques could be very expensive due to resin regeneration or energy costs. The possibility of using supported liquid membranes (SLM) with ionic liquids (IL), Aliquat 336, Cyphos IL 101 and Cyphos IL 167, as carriers to exchange Cl− for HCO3− anion has been shown to work. The reversibility of this anion exchange was corroborated by solvent extraction experiments and implemented in flat sheet supported liquid membrane (FSSLM) and hollow fiber renewal liquid membrane technologies (HFRLM).
About double transport values have been obtained in HFRLM compared to SLM and 1 h is the time enough to reduce the chloride concentration up to 250 mg/L using HFRLMat the best experimental condition. The results obtained allow us to be optimistic about the implementation of this technology on a large scale to chloride
reduction in drinking water when the source is inadequate for direct use.
Supplementary resource (1)
... Yaftian et al. reported the separation of 95.4% of Th(IV) through the bulk liquid membrane (BLM) after 8 h (Yaftian et al., 2006), but due to low mass transfer rate of BLM, application of this method has been restricted to the laboratory scale. El-Reefy et al. compared the performance of spray column and batch liquid emulsion membrane techniques for isolation of 234 Th from natural uranium (El-Reefy et al., 1996) and concluded the simplicity and high efficiency in separating or enriching of thorium from liquid mixtures by using the ELM process. The process gave a high degree of concentration of metal ions in fewer stages while maintaining the high selectivity of the solvent extraction. ...
... Kedari et al. proposed supported liquid membrane (SLM) technique (Kedari et al., 2013) in which the organic membrane phase immobilizes within a porous solid membrane and could be appropriate for the practical applications. Although the flat sheet geometry of SLM is restricted for laboratory uses, the spiral wound and hollow fiber modules which provide high surface area to volume ratio, have developed for industrial application (Ura et al., 2006;Gabelman and Hwang, 1999). In addition, in order to maximize the efficiency of the process with long-term stability, different configurations of membrane contactors have utilized including the dispersion free solvent extraction (NDSX) (Patil et al., 2008), pseudo-emulsion-based hollow-fiber strip dispersion (PEHFSD) (Roy et al., 2008) and hollow fiber renewal liquid membrane (HFRLM) (Zhang et al., 2005;Allahyari et al., 2016). ...
... Thus the main advantages of HFRLM than the conventional types of extraction, especially SLM system are the intensification of mass transfer rate, the long-time stability of the liquid membrane, the higher membrane surface area, the possibility to use the expensive extractants due to lower consumption of LMs, the creation of no secondary pollution and lower capital, maintenance and operation cost, lower energy consumption and more easily scale-up the process due to the compact and modular devices, and wide range of operation region (Ren et al., 2007a). HFRLM have many potential application including removal of organic pollutants, aroma recovery, pharmaceuticals extraction (Ren et al., 2009a(Ren et al., , 2014(Ren et al., , 2009b and metallic compounds recovery from industrial wastewaters (Ren et al., 2007a;Ren et al., 2009c;Weidong et al., 2010;Fortuny et al., 2014). ...
In this study, continuous extraction and back extraction of Th(IV) is carried out in the hollow fiber renewal liquid membrane (HFRLM) process. The organic solution of bis(2,4,4-trimethylpentyl) phosphininc acid (Cyanex 272) diluted in kerosene is used as a liquid membrane phase which could transport thorium ions from the aqueous nitrate solution of donor phase to the acceptor phase containing H2SO4. The experiments are performed in the fashion that a mixture of aqueous and organic phase in the volume ratio of (A/O) 20 flows through the lumen side while the aqueous acceptor phase is pumped through the shell side. Results indicate the satisfactory stability of HFRLM process during 10 h of continuous operation. In addition, results show that the increase in the velocity of fluid in the lumen side, concentration of cyanex 272 in the liquid membrane phase, and pH of the feed leads to increase the mass transfer flux. However, increase in the H2SO4 concentration of acceptor phase from 0.2 to 1 mol.L⁻¹ and initial concentration of thorium (IV) has no significant effect. In addition the overall mass transfer coefficient are calculated in the range of to m/s.
... 11 As a result, the HFRLM process would have potential applications, which include the removal of the organic pollutants, the aroma recovery, 12,13 the pharmaceuticals extraction, 14 the recovery of metallic compounds from industrial wastewaters and hydrometallurgical processes. [15][16][17][18][19] In order to provide an appropriate tool to consider some engineering issues like the detailed design, the estimation of cost, the scale up and optimization of the HFRLM process, it is necessary to develop a simple and precise mathematical model. Bringas et al. reported an overview on the different approaches of the mathematical modeling of hollow ber liquid membrane contactors. ...
... The recovery efficiency R (%) of the system has been calculated by eqn (18). ...
In the present work, the experimental investigation and mathematical modelling of Th(IV) recovery has been carried out by using the recycling mode of the hollow fiber renewal liquid membrane (HFRLM) process. Experiments were done at various operational conditions: the concentrations of TBP (tri-butyl phosphate) diluted in kerosene as a liquid membrane (LM), the nitrate and thorium(IV) ions concentration in the feed and flow rates of the feed and strip phases in the membrane module. The results indicate that practically more than 96% of thorium can be removed from an aqueous phase containing 198 ppm Th(IV) and 2 M NO3⁻ by using the LM comprising of 30% (v/v) of TBP while the feed and stripping solutions were being circulated at the flow rates of 5.6 mL min⁻¹ within 7 hours. In addition, a rigorous mathematical model has been developed to predict the experimental data. For this purpose, one-dimensional time dependent mass conservation equations in the longitude direction of the shell and lumen sides and in the radial direction of liquid membrane are numerically solved. The reasonable agreement between the experimental and the predicted data suggests the validity of the developed model. Therefore, this model might be useful for the design and optimization of the recovery of Th(IV) in the HFRLM process in the recycling mode.
... For example, adding 2-nitrophenyl-octyl ether to [A336] [SCN] extractant in a PVDF support demonstrated stable performance over nine days [232]; sandwiching the liquid organic phase between dense IEMs may improve the LM stability and allow its application in the ED process [233]. Furthermore, development of low-cost and environmentally friendly solvents such as sunflower oil [234] and mineral oil [17] could reduce the cost and safety risks of LMs; a strategy of regularly refilling the organic phase in LMs [235] helps maintain continuous operation. Regardless, improving LM stability remains a critical research need in order to take advantage of their unrivalled selectivity in practical water treatment applications. ...
Membrane separation has enjoyed tremendous advances in relevant material and engineering sciences, making it the fastest growing technology in water treatment. Although membranes as a broad-spectrum physical barrier have great advantages over conventional treatment processes in a myriad of applications, the need for higher selectivity and specificity in membrane separation is rising as we move to target contaminants at trace concentrations and to recover valuable chemicals from wastewater with low energy consumption. In this review, we discuss the drivers, fundamental science, and potential enabling materials for high selectivity membranes, as well as their applications in different water treatment processes. Membrane materials and processes that show promise to achieve high selectivity for water, ions, and small molecules—as well as the mechanisms involved—are highlighted. We further identify practical needs, knowledge gaps, and technological barriers in both material development and process design for high selectivity membrane processes. Finally, we discuss research priorities in the context of existing and future water supply paradigms.
... In addition, recent studies have demonstrated the potential of ionic liquids as desalination solvent due to their design flexibility and low volatility. However, their exceptionally low yield results in a low water production rate and a relatively high energy consumption [14][15][16]. In our previous study, we showed that molecular dynamics (MD) simulations can demonstrate experimentally observed desalination qualitatively [17]. ...
Desalination by solvent extraction is a simple and cost-effective technology to replace current ones. Although desalination solvents are continually developed, there is still a lack of understanding of the mechanism. In this study, we elucidate the solvent extraction desalination mechanism at the atomic level using molecular dynamics(MD) simulations. Three organic solvents octylamine(8A), dibutylamine(DBA), and 2-ethylhexylamine(EHA), which all have the same chemical composition but the amine group at different positions, were used. We simulated the desalination process from the brine-and-organic-solvents-mixing step to the brine-separation step. The MD simulations showed that DBA and EHA formed planar clusters while 8A formed gel clusters. By analyzing MD trajectories, we identified two types of water recovery mechanism, in which DBA and EHA clusters selectively absorb water and 8A traps brine by forming a gel structure. The polar interactions between water molecules and solvents are important driving forces for the absorption of water. To explain the desalination performances of DBA and EHA, morphological characteristics and surface polarity of the clusters were measured. It was found that a higher surface polarity facilitates more water absorption. Partial recovery of the salt ions was attributed to the surface polarity of the organic solvent clusters.
... However, large scale production of these techniques could potentially be very expensive due to resin regeneration or high energy costs. The possibility of using SLM with ionic liquids (IL), Aliquat 336, Cyphos IL 101, and Cyphos IL 167, as carriers to exchange Cl − for the HCO 3 − anion, has been reported on with positive results [184]. The reversibility of this anion exchange was corroborated by solvent extraction experiments and implemented in flat sheet SLM and hollow fiber renewal liquid membrane technologies. ...
The present review is mainly focused on the overview of carrier mediated extraction (principles and applications) being reported over the last two decades and discusses the extraction process through carriers in various extraction methods such as Bulk liquid membranes, supported liquid membranes, emulsion liquid membranes and polymer inclusion membranes. Several types of carriers such as neutral, anionic, cationic, macrocyclic and supramulecular carriers are discussed. Also their application for metal, anions, drugs and environmental compounds are investigated. Carriers have been demonstrated to be useful for the selective extraction and recovery of numerous cations and anions enhancing the extraction properties of traditional solvent extraction and ion-exchange processes. Several types of carriers have different transport mechanisms. In these mechanisms, transport configurations are addressed and emphasized and the detailed information on the type of carrier are presented along with their specific separation modes. The performance of different carriers in terms of selectivity as well as efficiency are also discussed. Finally, the application of different carriers for the extraction of various compounds are compared and reviewed. To our best knowledge no reviews have been published on carrier-mediated extraction methods.
... Among the various types of the supported liquid membranes, (hollow fiber contactors) HFCs have some advantages such as high surface to volume ratio, less amount of extractant, long lifetime and low energy consumption [24][25][26], several new HFC configurations have been explored including hollow fiber contained liquid membrane (HFCLM) [27], non-dispersive solvent extraction (NDSX) [28], pseudo-emulsion based hollow fiber strip dispersion (PEHFSD) [29,30] and hollow fiber renewal liquid membranes (HFRLM) [31]. In the HFRLM technique, the LM formation is performed in accordance with the theory of surface renewal and the HFRLM offers comparatively low mass transfer resistance [32][33][34][35]. In this technique, the porous hydrophobic hollow fibers are used. ...
In this study the application of various surfactant agents on the performance of HFRLM for uranium transfer was investigated. Using Taguchi experimental design in recycling mode of HFRLM, maximum uranium recovery of 63.17% was obtained at 0.15 mol L⁻¹ H2SO4, 0.0125 mol L⁻¹ Alamine 336 and 0.25 mol L⁻¹ NH4Cl in the donor, liquid membrane and acceptor phase, respectively. Also, the continuous mode experiments were conducted and HFRLM stability was compared with HFSLM. The uranium transfer would be improved by adding 0.05 mmol L⁻¹ of SDS, CTAB and LAE-7 to the donor phase and 10 mmol L⁻¹ of CTAB and LAE-7 to the acceptor phase.
... In the past few years, in order to overcome the low stability of HFSLM, the hollow fiber renewal liquid membrane (HFRLM) process has been developed [13][14][15][16][17][18][19][20][21][22][23]. HFRLM technique is based on the surface renewal theory and integrates advantages of the hollow fiber membrane extraction process, liquid film permeation process, and other liquid membrane systems. ...
The performance of the hollow fiber renewal liquid membrane (HFRLM) in the continuous and recycling modes for the extraction of uranium(VI) from the acidic sulfate solution has been investigated. Alamine 336 diluted in kerosene was used as a carrier in liquid membrane (LM) phase. In the batch experiments, the effects of sulfuric acid, extractant and uranium(VI) concentration were studied and the optimum concentration of the donor and LM phases were determined 0.15 mol L⁻¹ and 0.0125 mol L⁻¹, respectively. Various parameters affecting the HFRLM performance including the lumen and shell side flow rate, organic/aqueous volume ratio, acceptor phase type and concentration of carrier and acceptor phase were studied. The mass transfer flux increases with increasing the lumen side flow rates and the shell side flow rate did not have any significant effect. The uranium transfer flux increases with increasing O/A ratio, acceptor and Alamine 336 concentration, and reaches a maximum value at 1/20, 0.5 mol L⁻¹ and 0.0125 mol L⁻¹, respectively. Further increase in these parameters result in uranium transfer decrement. The results show that liquid membrane phase is a rate-controlling step. Among the investigated acceptor phases, 0.5 mol L⁻¹ NH4Cl result in 60.35% uranium(VI) recovery in the recycling mode.
... Among them, Ionic Liquids (ILs) have been used as task specific solvents or in the preparation of task specific materials for the effective extraction of pesticides. Although variety of extraction strategies, such as aqueous biphasic systems [23], liquid membranes [24,25] and adsorption [26,27], have been tested, ILs's high cost and difficult purification, and thus recycling, hinder their application in wastewater treatment. ...
Wastewater treatment plants do not properly address the removal of emerging micropollutants, such as pesticides, and thus these compounds contaminate water sources of public drinking water systems. In this context, this work focuses on the development of hydrophobic deep eutectic solvents (DESs), as cheap extractants for the removal of four neonicotinoids, Imidacloprid, Acetamiprid, Nitenpyram and Thiamethoxam, from diluted aqueous solutions. In particular, two different families of DESs, one based on natural neutral ingredients (DL-Menthol and natural organic acids) and the other based on quaternary ammonium salts and organic acids were prepared and their water stability carefully studied through ¹H NMR. Only the chemically stable DESs were selected to be used as solvents in the extraction of the four neonicotinoids so that no contamination of the water cycle is attained, while reuse of the DES is possible. The final results were compared with those obtained for liquid-liquid extraction using hydrophobic imidazolium-based ionic liquids as solvents.
... By using this system, separation and removal of a large number of cations as well as a number of anions have been investigated. Some of the anions include chloride [18], nitrite [19], nitrate [20], bromide [21], chromate [22] and iodide [23]. ...
A bulk liquid membrane (BLM) containing dimethyldioctadecylammonium chloride (DODMAC) as the carrier reagent was developed for the removal of nitrate from water. DODMAC was found to be an efficient carrier for the nitrate transport through a solvent membrane containing 10 vol% chloroform and 90 vol% n-hexane. The optimum conditions of operation were found as: concentrations of feed, carrier and strip reagents of 0.00145, 0.012 and 0.8 M, respectively, and stirring speed of agitation of 250 rpm. At optimum conditions the extraction reached 99% after 7 h of operation while the stripping was also 97%. The latter reveals the high efficiency of the stripping phase in releasing the carrier. The long-term performance of the developed system was also appropriate where after 60 h of operation the extraction of nitrate was more than 92%. Effects of other parameters including the feed/membrane and membrane/strip phase ratios (v/v), nitrate salt, and type of strip reagent on the mass transfer of membrane system were also studied. The small amounts of remained chloroform in water were removed using air stripping method. Comparison between this work and other BLM works confirms the priority of developed system in removing nitrate from contaminated water.
Ionic liquids (ILs) play a crucial role in modern chemistry and chemical engineering. They remain more desirable than conventional volatile solvents and catalysts in many physical and chemical processes, often exhibiting green and designer properties for various applications.
Examining the unique contribution of ILs towards current environmental challenges, this book addresses the importance of their role in the detection of micropollutants and decontamination processes in air and water compartments.
It also presents a detailed review of how ILs impact the environment once released, a topic seldom covered in other books, and highlights novel chemoinformatic tools used to predict their fate, showing how advanced oxidation processes help in remediation.
This is an ideal book for researchers in both academia and industry, and postgraduate students in environmental chemistry, chemical engineering and analytical chemistry looking at the potential applications of ionic liquids in addressing several environmental problems.
The multimembrane hybrid system (MHS) was proposed for the separation and recovery of Zn²⁺ cations from a multi ionic feed phase. The composition of the aqueous solution used as the feed phase simulates qualitatively wastewater from either hydrometallurgical or electroplating processes. The effect of various physicochemical and operational parameters was investigated. It was found that Zn²⁺ cations can be effectively separated from multi ionic solution (according to the carrier properties) and concentrated in the stripping solution with the quasi–stationary fluxes attaining 6 × 10⁻¹⁰ mol/cm²s. The sufficient selectivity and fluxes of Zn²⁺ ions are observed for carrier concentration in the liquid membrane varied between 0.05 and 0.1 M D2EHPA, the feed solution concentration varied between 2 × 10⁻³ M and 0.01 M, the striping solution concentration equals 1 M, and initial pH of the feed solution higher than 2. It was also experimentally confirmed that the cation–exchange membranes enable a long–term and continuous operation of the system.
Novel processes based on SIMALE have been proposed as effective methods for the selective separation of different chemical species such as metal ions, organic/biologically important compounds and gas mixtures from different waste streams including nuclear waste. The industrial use of supported liquid membranes based on conventional liquids is limited by their relative instability and short lifetime. Under SIMALE techniques, the stability of the SLM is ensured by a modified SLM with pseudo emulsion based hollow fiber strip dispersion or non-dispersive solvent extraction techniques. In order to promote operational stability, SIMALE, using ionic liquids, as a liquid membrane phase could overcome these inconveniences due to their negligible vapour pressure and the possibility of minimizing their solubility in the surrounding phases. SIMALE studies on membrane-based dense gas extraction reported higher extraction efficiencies when the near critical or supercritical solvent is used. This review also discuss important applications including scale up, process intensification aspects, current status of the technology and future directions.
In this study, Th(IV) is transported through a hollow fiber renewal liquid membrane (HFRLM) in the system containing tributyl phosphate (TBP) and 0.1 mol L⁻¹ HNO3 as the carrier and the acceptor phases, respectively. The effects of operating mode, flow rates of the lumen and the shell sides and volume ratio of the organic to the aqueous phase on the mass transfer performance of HFRLM process are scrutinized. Experimental results indicate a satisfactory stability of HFRLM process during 12 h of continuous operation. Moreover, the mass transfer rate of Th(IV) in the operating mode in which a stirred mixture of feed and organic phases passes through the lumen side is higher than the mode in which a stirred mixture of the acceptor and the organic phases flows through it. In addition, the correlations used for calculation of local mass transfer coefficients of the renewal layer and the shell side are modified. Furthermore, the mass transfer rate in the HFRLM system was about twice more than that in the hollow fiber supported liquid membrane.
In this work transport of Zn(II), Fe(II) and Fe(III) ions from chloride aqueous solutions across polymer inclusion membranes (PIMs) and supported liquid membranes (SLMs) containing one of three phosphonium ionic liquids: trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) and tributyl(tetradecyl)phosphonium chloride (Cyphos IL 167) as ion carrier was reported. The results show that Zn(II) and Fe(III) are effectively transported through PIMs and SLMs, while Fe(II) transport is not effective. The highest values of initial flux and permeability coefficient of Zn(II) were noticed for SLM containing Cyphos IL 167. Cyphos IL 101-containing SLM is more stable than PIM.
The feasibility of cascade process for penicillin G recovery utilizing hollow fiber renewal liquid membrane (HFRLM) technique was investigated and the optimal conditions were determined. Cascade process of HFRLM was carried out to recover penicillin G from the aqueous solution using di-n-octylamine in iso-octanol and kerosene as the liquid membrane phase and K2CO3 aqueous solution as the stripping phase. The mass transfer performance of the process was evaluated in a hollow fiber module with 1000 microporous and hydrophobic polypropylene (PP) hollow fibers. The cascade process of HFRLM was feasible for penicillin G recovery and the enrichment factor, extraction and recovery efficiency were larger than that of single-stage process. The stripping phase of 0.5 mol L−1 K2CO3 solution could not only keep the efficiency of re-extraction, but also ensure the stability of penicillin G. Besides, the results indicated that 0.2 mol L−1 potassium dihydrogen phosphate solution as the buffer solution in the feed solution could greatly reduce the loss of penicillin G due to the pH fluctuation. In the cascade mode operated at the flow rates of 45 mL min−1 in the shell side and 20 mL min−1 in the tube side, the extraction and recovery efficiency of 97% and 82% for penicillin G were achieved after 7 stages respectively. The cascade process of HFRLM for penicillin G recovery exhibits good potential in industrial application.
For bio-butanol to be competitive with other commercially available fuels like gasoline, the development of energy-efficient technologies for its separation from dilute fermentation broth is necessary. Due to their special properties as extractants, the suitability of selected ammonium and phosphonium cation-based room temperature ionic liquids (RTILs) for butanol separation is investigated in this work. Determination of the RTIL extractants’ partition coefficients (KP) for butanol and other broth components is accomplished. To tune butanol extractability, RTIL–RTIL and RTIL–organic solvent blends are also tested. In addition, the toxicity of the extractants to Clostridium acetobutylicum and Clostridium beijerinckii is studied. Results indicated that KP for butanol is more controlled by RTIL anion moieties with the trend: dihexylsulfosuccinate ([DHSS])>dicyanamide ([DCN])>bis(trifluoromethylsulfonyl)imide; while the alkylammonium cation showed stronger effect on KP than the alkylphosphonium cation counterpart. All extractants showed the same KP trend for typical fermentation products: butanol>acetone>ethanol. [DHSS] and [DCN] anion-based RTILs exhibited pH dependence for acetic and butyric acids partitioning. Butanol affinities in extractant blends exhibit strong dependence on blend composition. The extractants’ cytotoxic effect varied according to their concentration, the type of exposed bacterial strain and fermentation conditions.
Ionic liquids are good solvents for catalytic reactions. The rational selection of the appropriate ionic liquid solvent for a particular reaction requires general knowledge of the properties of ionic liquids, and the details of some properties of the specific ionic liquid solvents being considered. The solvent properties of ionic liquids that are relevant to catalysis are discussed, and sources of the values of those properties for ionic liquids are identified. A roadmap for the literature values of density, viscosity, melting and glass transition temperatures, thermal stability, empirical solvent parameters, absorption, toxicity, surface tension, heat capacity, and thermal conductivity is provided.
Previously, we reported on using room temperature ionic liquids (RTILs) in place of traditional solvents in liquid membranes and showed that stabilized RTIL-membranes outperformed standard polymers for the separations of CO2/CH4 and CO2/N2 (considering ideal gas permeabilities). Here, we report on mixed-gas permeances and selectivities for the gas pairs CO2/CH4 and CO2/N2 using continuous flows of the mixed gases at various carbon dioxide concentrations (up to 2 bars of CO2 partial pressure). Under mixed-gas test conditions, three of the tested membranes still operated with commercially attractive mixed-gas selectivity combined with CO2-permeability for CO2/CH4 separations. In addition, one of the tested membranes is, potentially, economically viable for CO2 capture from flue gas. We answer three objections to reduction-to-practice of RTIL-membranes for gas separations; namely, mixed-gas operations did not reduced the gas selectivities, membranes give advantageous performance even under dry gas feed conditions, and we achieved long-term stability in continuous operation, up to 106 days, without performance degradation. Furthermore, the RTIL-membranes operated under CO2-partial pressures of at least 207 kPa without decrease in separation ability. The RTIL-membranes tested include [emim][BF4], [emim][dca], [emim][CF3SO3], [emim][Tf2N], and [bmim][BETI].
Desalination, other than the natural water cycle, is hailed as the panacea to alleviate the problems of fresh water shortage in many water stressed countries. However, the main drawback of conventional desalination methods is that they are energy intensive. In many instances, they consumed electricity, chemicals for pre- and post-treatment of water. For each kWh of energy consumed, there is an unavoidable emission of Carbon Dioxide (CO2) at the power stations as well as the discharge of chemically-laden brine into the environment. Thus, there is a motivation to find new direction or methods of desalination that consumed less chemicals, thermal energy and electricity.This paper describes an emerging and yet low cost method of desalination that employs only low-temperature waste heat, which is available in abundance from either the renewable energy sources or exhaust of industrial processes. With only one heat input, the Adsorption Desalination (AD) cycle produces two useful effects, i.e., high grade potable water and cooling. In this article, a brief literature review, the theoretical framework for adsorption thermodynamics, a lumped-parameter model and the experimental tests for a wide range of operational conditions on the basic and the hybrid AD cycles are discussed. Predictions from the model are validated with measured performances from two pilot plants, i.e., a basic AD and the advanced AD cycles. The energetic efficiency of AD cycles has been compared against the conventional desalination methods. Owing to the unique features of AD cycle, i.e., the simultaneous production of dual useful effects, it is proposed that the life cycle cost (LCC) of AD is evaluated against the LCC of combined machines that are needed to deliver the same quantities of useful effects using a unified unit of $/MWh. In closing, an ideal desalination system with zero emission of CO2 is presented where geo-thermal heat is employed for powering a temperature-cascaded cogeneration plant.
High productivity reverse osmosis membrane developed under the Office of Naval Research Expeditionary Unit Water Purification Program was evaluated at the Bureau of Reclamation Brackish Groundwater National Desalination Research Facility (BGNDRF). Performance of the new membrane was evaluated in comparison to two other commercial high productivity or low pressure reverse osmosis membranes using a high productivity test system designed and built to take best advantage of high flux membrane through either lower operating pressure or greater productivity. Membranes were evaluated with brackish groundwater over a range of cross flow velocities and recovery rates. Experimental membrane water transport was approximately twice two to three times that of the commercial membrane and salt transport was an order of magnitude less than commercial membrane at 20% recovery for three modules of four inches by forty inches in series tested at a range of feed flow rates.
Reverse osmosis (RO) membranes have been widely applied to seawater desalination and wastewater reclamation. Since 2000, large RO plants (100,000 m3/day plants) have been constructed. However, much larger plants will be required in the near future because of its worsening situation of water problems. Energy efficiency is indispensable for the larger plants, especially mega plant (1,000,000 m3/day plant). “Mega-ton Water System” project which consists of eight themes believes that there is plenty of room for improvement as well as optimum layout of each component used in the mega plant. In order to reduce energy demand in RO operation, high efficient RO membrane is studied in the project. The relationships between RO membrane structure and its performance were investigated by transmission electron microscope–tomography. The utilizing of pressure retarded osmosis (PRO) energy recovery is one of a solution for energy-saving and defusing the environmental impact caused by concentrated brine. A PRO hollow fiber membrane module was newly developed and a practical continuous operation has been examined at a prototype plant for 1 year. The concept of the project will be established by combining the results of eight themes as competing with other membrane and its process studies.
Membrane distillation (MD) is a hybrid membrane-evaporative process which has been of interest for desalination. MD requires two types of energy, namely, low temperature heat and electricity. Solar collectors and PV panels are mature technologies which could be coupled to MD process. The interest of using solar powered membrane distillation (SPMD) systems for desalination is growing worldwide due to the MD attractive features. Small scale SPMD units suitable to provide water for human needs in remote areas where water and electricity infrastructures are currently lacking have been developed and tested by a number of researchers. The combination of solar energy with MD has proven technically feasible; however, the cost of produced water is relatively high compared with that produced from the commercial PV–RO process. The production of commercial, reliable, low cost and long lasting MD modules will put this process on the front edge of desalination technologies. The aim of this article is to present the main features of MD along with its basic principles. Efforts of researchers in coupling MD with solar energy and their cost estimates are reviewed as well.
Energy or heat recovery schemes are keys for the performance improvement of any heat-activated cycles such as the absorption and adsorption cycles. We present two innovative heat recovery schemes between the condensing and evaporating units of an adsorption desalination (AD) cycle. By recovering the latent heat of condenser and dumping it into the evaporative process of the evaporator, it elevates the evaporating temperature and hence the adsorption pressure seen by the adsorbent. From isotherms, this has an effect of increasing the vapour uptake. In the proposed configurations, one approach is simply to have a run-about water circuit between the condenser and the evaporator and a pump is used to achieve the water circulation. This run-around circuit is a practical method for retrofitting purposes. The second method is targeted towards a new AD cycle where an encapsulated condenser–evaporator unit is employed. The heat transfer between the condensing and evaporative vapour is almost immediate and the processes occur in a fully integrated vessel, thereby minimizing the heat transfer resistances of heat exchangers.
The extraction behavior of (152+154)Eu(III) and 241Am(III) in a solution of bis(2-ethylhexyl)phosphoric acid (D2EHPA) or bis(2-ethylhexyl)diglycolamic acid (HDEHDGA) in the ionic liquid, 1-octyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide (omimNTf2), was studied at 298K. The extractant HDEHDGA was synthesized and characterized by IR, 1H NMR and mass spectroscopy. The effect of various parameters such as the concentrations of nitric acid, D2EHPA, HDEHDGA and diethylenetriaminepentaacetic acid (DTPA) on the extraction behavior of 241Am(III) and (152+154)Eu(III) was studied and the results are reported in this paper. Superior extraction of the target metals and excellent separation factors achieved with the use of the ionic liquid diluent indicates the feasibility of separating lanthanides from actinides present in high-level liquid waste (HLLW).
Ionic liquids are good solvents for catalytic reactions. The rational selection of the appropriate ionic liquid solvent for a particular reaction requires general knowledge of the properties of ionic liquids, and the details of some properties of the specific ionic liquid solvents being considered. The solvent properties of ionic liquids that are relevant to catalysis are discussed, and sources of the values of those properties for ionic liquids are identified. A roadmap for the literature values of density, viscosity, melting and glass transition temperatures, thermal stability, empirical solvent parameters, absorption, toxicity, surface tension, heat capacity, and thermal conductivity is provided.
Trihexyl(tetradecyl)phosphonium chloride (Cyphos®IL 101) and bis(trifluoromethylsulphonyl)imide (Cyphos®IL 109) – phosphonium ionic liquids – were used as novel reagents mixed with toluene to extract zinc(II) from chloride media. Extraction of zinc(II) was very fast and efficient (EZn over 95%) for molar ratio of Cyphos®IL 101/Zn(II) more than 2. It was found that the presence of HCl in the feed enhanced Zn(II) extraction. The reactions of Zn(II) extraction mechanism were proposed. The values of ΔH° were estimated to be 32.93 (standard deviation (s.d.)=2.81) and 52.85 (s.d.=1.90)kJmol−1 and ΔS° amounted to 120.65 (s.d.=8.84) and 182.13 (s.d.=6.02)Jmol−1K−1 for reaction without HCl and with 0.58M acid, respectively. The extraction of zinc(II) with Cyphos®IL 101/toluene mixture is an endothermic reaction. Successful stripping of zinc(II) from the loaded organic phase was achieved with 1M sulphuric acid. Cyphos®IL 101 can be reused at least in 3 cycles of extraction-stripping process. Due to low extraction of Zn(II) Cyphos®IL 109 cannot be considered as effective extractant in the studied system.
Tetraalkylphosphonium ionic liquid (IL) with a bis 2,4,4-trimethylpentylphosphinic anion (Cyphos IL-104) is an effective extractant of lactic acid (LA) achieving at low LA concentrations the distribution coefficients for aqueous systems above 40. L/L equilibrium data for pure Cyphos IL-104 and its solutions in n-dodecane have been measured. With increasing acid concentration the value of the distribution coefficient of LA decreases. Cyphos IL-104 extracts only undissociated molecules of lactic acid (LAH) via H-bonding. Increase in the concentration of IL-104 in n-dodecane results in increasing distribution coefficient of LA and the water solubility. The high water content in the solvents with Cyphos IL-104 is connected with the formation of reverse micelles. An interesting phenomenon of the liberation of water from the solvent in extraction of LA has been observed. It is suggested that splitting of the reverse micelles due to the formation of LAH/IL complexes occurs. With increasing temperature the values of the distribution coefficients of LA practically does not change or only slightly increases. In contrary to this, the increase in temperature decreased the water solubility in solvents containing IL-104. This is interpreted by the lower stability of reverse micelles at higher temperatures. Based on experimental equilibrium data the formation of stoichiometrically defined complexes with the structure (LAH)p(IL)(H2O)2 and (p, 1, 2) stoichiometry, where p is in the interval from 1 to 3, is suggested. The proposed model fits the equilibrium data well and indicates the domination of the (2, 1, 2) complex at medium aqueous acid concentrations in the interval from 0.2 to 2kmolm−3. There are two mechanisms of water extraction into the solvents with Cyphos IL-104: the formation of reverse micelles, and the formation of hydrated complexes of LAH with IL. A sharp decrease in the viscosity of solvents with IL-104 with increasing concentration of water or LA was observed.
Nafion composite membranes for CO2 separation with good CO2/CH4 separation factors were developed using ionic liquids (ILs) and Nafion. Three ionic liquids containing the 1-n-hexyl-3-methylimidazolium ([hmim]) cation with different anions were characterized by the measurement of the CO2 separation performance using supported ionic liquid membranes in a polysulfone asymmetric support. Two different Nafion membrane-containing ILs for CO2 separation membranes were prepared by the adsorption of IL on a dense and electrospun Nafion/polyethyleneoxide composite membrane in order to improve the stability of the liquid membrane. The electrospun Nafion layer containing polyethyleneoxide was prepared by the electrospinning technique in order to affix [hmim][BF4] (or [hmim][PF6]) on the porous polysulfone asymmetric support. The ideal CO2/CH4 separation factor of electrospun Nafion composite membranes with [hmim][BF4] was consistent with that of [hmim][BF4]. The ideal CO2/CH4 separation factor was 26 for the Nafion composite membranes containing both [hmim][BF4] and [hmim][PF6] in the dense Nafion layer, implying a change in the microdomain of Nafion in the presence of IL and the facilitation effect of ILs for CO2 separation through the IL-swollen Nafion membrane.
Nowadays, more than 110 cities of China confront the serious problem of fresh water shortage, and more than 70% of the rivers and lakes are contaminated to some extent. About 38 million people are depending on brackish water for life. Desalination of seawater and brackish water is one of the ways to solve the potable water shortage problem of the people living in arid areas or by the sea. A solar-heated hollow fiber vacuum membrane distillation (VMD) system for potable water production from underground water was designed. The solar radiation time and mean temperature of different months in Hangzhou area in 2005 were analyzed. The performance of the system for potable water production was tested. The experiment results showed that the pure water flux of the system could reach 32.19 kgm−2 h−1 (per square meter membrane area with the 8m2 solar energy collector) in October 2006 in Hangzhou area, south of China. The daily cumulated permeation flux could be more than 170 kgm−2 (membrane area) in October 2006 under good weather conditions, and more than 50 kgm−2 in cloudy weather in Hangzhou area of China. The influence of the feed flow rate on the permeate flux is analyzed. The results show that the higher the feed temperature, the lesser the temperature polarization influence on the permeate flux of the VMD. The construction of the presented system is simple and compact with operation, and maintenance costs mainly for pumps. The feasibility of the hollow fiber vacuum MD module coupled with a solar energy collector to produce potable water from underground water has been proven.
Ionic liquids can be used in various morphologies and configurations as membrane systems including supported liquid membranes, membrane contactors, and mixed matrix membranes. In each case, the negligible vapor pressure can lead to a highly stable structure since the ionic liquid is non-volatile. This perspective is meant to provide some background information on the use of ionic liquids in membrane systems and a discussion of future opportunities for this technology. Ionic liquids with different physical properties can be synthesized in a wide range of structures. In addition, this platform provides an opportunity to “tune” the physical/chemical properties such as density, viscosity, hydrophobicity, and chemical affinity for specific applications. The use of ionic liquids in membrane systems should see continued growth in the future.
The effect of water content in 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) on CO2/N2 separation performance of polyethersulfone supported ionic liquid membrane has been investigated theoretically and experimentally. A small addition of water in [bmim][BF4] obviously improves the performance of the membrane. CO2 permeance increases from 11.5 to 13.8GPU and CO2/N2 selectivity increases from 50 to 60, where the water molar fraction increases from 0 to 0.10 at the cross-membrane pressure difference of 0.24MPa. The improvement of the CO2 permeance at low water content can be attributed to the increase of CO2 diffusivity due to the decrease of viscosity with increasing the water content. While, the CO2 permeance decreases at high water content because of the decreasing CO2 solubility, which is mainly caused by the hydrogen bond interaction between water and [bmim][BF4]. A corrected solubility coefficient model of CO2 in ionic liquid is proposed to evaluate the influence of water–[bmim][BF4] interaction on CO2 solubility. The comparison of CO2 permeance between theoretical values and experimental ones demonstrates that the number of water molecule bound to a [BF4]− is between 1 and 2 in the range of the water content in our research.
A process to remove and recover cadmium from wastewater has been developed which includes solvent extraction and supported liquid membrane transport for Cd(II) using Cyanex 923 as an extractant/carrier. The influence of acid and chloride ion concentration on the extraction of Cd(II) was studied. In acidic medium, the appearance of a third phase was observed and the limiting organic concentration for Cd(II) in 5 and 10% Cyanex 923/Exxsol D100 at different concentrations of H+ ions were determined. The effect of aliphatic and
aromatic diluents on the extraction and permeation of Cd(II) in neutral and acidic medium was studied and
permeation coefficients were evaluated, together with the influence of third phase and pore size on transport
of Cd(II) through microporous membrane. It was found that the appearance of a third phase in acidic medium
could be avoided by using an aromatic diluent. In order to improve the stability of supported liquid membrane and to scale up for continuous operation, the performance of hollow fiber strip dispersion (HFSD) technique for the extraction/recovery of Cd(II) from acidic as well as neutral chloride media was examined.
This study emphasizes the potential of a HFSD system to be a part of sustainable wastewater treatment
technologies, enabling the separation/recovery of cadmium.
Ionic liquid (IL)-based extraction is a promising high-efficiency and environmentally benign separation technology. Imidazolium ILs lose their cations or anions to aqueous phase during extraction, the release lead to water pollution. To develop sustainable IL-based extraction system, we firstly investigate quaternary ammonium nitrate IL-based extraction strategy. Alkylated phosphine oxides (Cyanex925) in tricaprylmethylammonium nitrate ([A336][NO3]) are studied for separating Sc from Y and lanthanides. Distribution ratio and separation factor of the Cyanex925–[A336][NO3] system for Sc3+ are by far larger than those achieved using Cyanex925–[C8mim][PF6] system. The stability and solvating mechanism of Cyanex925–[A336][NO3] extraction system can avoid release of [A336][NO3] to aqueous phase. The novel quaternary ammonium nitrate IL-based extraction system is an efficient and sustainable separation strategy.Graphical abstractHighlights► The solubility of [A336][NO3] is low in acidic aqueous phase. ► Extractability and selectivity of Cyanex925 in [A336][NO3] for Sc3+ are large. ► Solvating mechanism of [A336][NO3] system avoid the loss of IL. ► Cyanex925–[A336][NO3] system maintains high extractability after five cycles.
Carbon dioxide (CO 2) emissions have to be controlled and reduced in order to avoid environmental risks. Membrane processes in combination with the use of ionic liquids are recently under research and development in order to demonstrate a zero solvent emission process for CO 2 capture. In this work, the application of a cross-flow membrane contactor is studied for CO 2 absorption when the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is used as solvent. A mathematical model considering a parallel flow configuration is applied for a cross-flow system in order to describe the mass transfer rate. At a macroscopic level, K overall a is calculated considering different mixing models corresponding to plug flow and continuous stirred models and a first order mass transfer rate. A microscopic model based on laminar flow has been applied, obtaining a membrane mass transfer coefficient of k m) 3.78 × 10 -6 m · s -1 , which is about five times higher than that obtained in the macroscopic model. The interfacial area, a, allows the comparison of efficiencies between cross-flow and parallel membrane contactor systems in terms of the product (K overall a).
Transport of salicylic acid (SA) through flat-sheet supported liquid membrane (SLM) was investigated using as liquid membrane the ionic liquids 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]) or ethylammonium nitrate (EAN). Using [C6mim][PF6], it has been observed that the transport efficiency decreases with increasing pH, indicating that the un-dissociated form of SA is mainly extracted. On the other hand, the ionic dissociated form of salicylic acid is mostly extracted via the anion exchange mechanism between nitrate and salicylate anions when EAN is used as liquid membrane. Parameters such as nature and concentration of the strippant in the receiving phase and concentration of the SA in the feed phase were studied. By comparing the SLM transport efficiency of SA (initial flux) of the two used ionic liquids, EAN appears to be slight efficient than [C6mim][PF6].Despite the use of different stripping solutions (NaCl, NaOH and Na2CO3) and even with pH maintenance around initial values, uphill transport driven by pH difference was not observed using both ionic liquids. The absence of uphill transport has been attributed to the formation, along the course of the experiment, of water microenvironments (aggregates) inside the ionic liquid. SA transport through these water microenvironments inside the liquid membrane becomes the main mechanism. The main feature of SLMs based on ionic liquids is their higher stability compared to classical SLMs. In fact, our SLM system retained its stability and initial performance during the 9 days long experiment.
Liquid membranes have traditionally been employed for liquid/liquid mass transfer and have found applications in industrial, biomedical and analytical fields as well as in hydrometallurgical processes, wastewater treatment and remediation of polluted groundwater. However, in spite of the known advantages of liquid membranes, there are few examples of industrial application. The development of reliable mathematical models and design parameters (mass transport coefficients and equilibrium or kinetic parameters associated with the interfacial reactions) is a necessary step for design, cost estimation, process optimisation and scale-up. This work reports an overview of the different approaches that have been proposed in the literature to the mathematical modelling of liquid membrane separation processes in hollow fibre contactors providing, at the same time, a useful guideline to characterise the mass transport phenomena and a tool for the optimal design and intensification of separation processes. Copyright © 2009 Society of Chemical Industry
OVERVIEW: During the past two decades, liquid membrane technology has grown into an accepted unit operation for a wide variety of separations. The increase in the use of this technology owing to strict environmental regulations and legislation together with the wider acceptance of this technology in preference to conventional separation processes has led to a spectacular advance in membrane development, module configurations, applications, etc.
IMPACT: Liquid membrane technology makes it possible to attain high selectivity as well as efficient use of energy and material relative to many other separation systems. However, in spite of the known advantages of liquid membranes, there are very few examples of industrial applications because of the problems associated with the stability of the liquid membrane.
APPLICATIONS: Liquid membrane technology has found applications in the fields of chemical and pharmaceutical technology, biotechnology, food processing and environmental engineering. On the other hand, its use in other fields, such as in the case of hydrogen separation, the recovery of aroma compounds from fruits, the application of ionic liquids in the membrane formulation, etc., is increasing rapidly. Copyright © 2009 Society of Chemical Industry
This report describes for the first time that the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide can be used as effective solvents in extractive distillation for the separation of an azeotropic mixture containing tetrafluoroethylene and carbon dioxide. The solubility of tetrafluoroethylene was measured at isothermal conditions (about 283–348 K) over a range in pressure from 0 to 1.4 MPa using a volumetric view cell. The solubility of carbon dioxide was measured at four isothermal conditions (about 283–348) K from 0 to 2.0 MPa using a gravimetric microbalance. The binary data were correlated and the feasibility of the extractive distillation process was modeled using ASPEN Plus® simulator. The tetrafluoroethylene and carbon dioxide were efficiently separated using a single absorption column and flash tank. The purity of the tetrafluoroethylene distillate from the top of the absorption column and the purity of the carbon dioxide from the flash tank exceed 99 mol%.Graphical abstractHighlights► Separation of an azeotropic mixture containing TFE and CO2. ► Solubility of TFE in ionic liquids. ► Solubility of CO2 in ionic liquids. ► Extractive distillation process modeled using ASPEN Plus® simulator.
Pseudomonas cepacia lipase supported in the 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid is an alternative “green” method for the production of biodiesel from the alcoholysis of soybean oil. The transesterification reaction catalyzed by this ionic liquid-supported enzyme can be performed at room temperature, in the presence of water and without the use of organic solvents. It is also compatible with various alcohols (including isoamyl alcohol). The biodiesel is separated by simple decantation and the recovered ionic liquid/enzyme catalytic system can be re-used at least four times without loss of catalytic activity and selectivity.
Lipids from algal biomass were extracted using mixtures of ionic liquids (ILs) and methanol, and fatty acid profiles of the extracted lipids were characterized in this work. Mixtures of ILs and methanol successfully dissolved biomass leaving lipids insoluble. The total contents of lipids extracted from commercial and cultivated Chlorella vulgaris were 10.6% and 11.1%, respectively, by the conventional Bligh and Dyer's method, while a mixture of [Bmim][CF(3)SO(3)] and methanol extracted 12.5% and 19.0% of the lipids, respectively. Multi-parameter regression by the linear solvation energy relationship showed that dipolarity/polarizability and hydrogen bond acidity of ILs are more important than their hydrogen bond basicity for effectively extracting lipids from algal biomass. Fatty acid profiles of the lipids extracted using IL-methanol mixtures showed that C16:0, C16:1, C18:2, and C18:3 fatty acids were dominant. This suggests that the lipids extracted from C. vulgaris can be used as a source of biodiesel production.
Supported ionic liquid catalysis is a concept which combines the advantages of ionic liquids with those of heterogeneous support materials. The viability of this concept has been confirmed by several studies which have successfully confined various ionic phases to the surface of support materials and explored their potential catalytic applications. Although the majority of the evaluated supports were silica based, several studies focused on polymeric materials including membranes. The preparation of these materials was achieved by using two different immobilization approaches. The first approach involves the covalent attachment of ionic liquids to the support surface whereas the second simply deposits the ionic liquid phases containing catalytically active species on the surface of the support. Herein recent advances made in this area are described.
Wilkes, properties of ionic liquid solvents for catalysis
J.S. Wilkes, properties of ionic liquid solvents for catalysis, J. Mol. Catal. A Chem. 214
(2004) 11–17.
Treating ground water contaminated with high perchlorate concentrations by an ion exchange membrane bioreactor
- Fox