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Mass-transfer in hollow-fiber modules for extraction and back-extraction of copper(II) with LIX64N carriers
Abstract
The extraction of Cu2+ ions from sulfate solutions across a hollow-fiber membrane containing LIX64N carriers dissolved in kerosene has been studied, in which Cu(II) was then back-extracted to a stripping-phase containing HCl. Experiments were conducted as a function of the initial feed concentration of Cu2+ (1–10 mol/m3), feed pH (2–6), the carrier concentration (0.1–0.4 mol/dm3), and stripping acidity (0.4–4 mol/dm3). A mass-transfer model was developed to predict the extent of Cu2+ extraction from aqueous feed in hollow-fiber contactors. The calculated time profiles of Cu2+ concentrations were in reasonable agreement with the experimental data (average standard deviation 9% in both extraction and back-extraction modules). The rate-controlling step(s) of such dispersion-free extraction processes were identified. It was shown that the extraction was governed by combined interfacial reaction and aqueous diffusion under the ranges studied, whereas the back-extraction was limited by combined membrane diffusion and aqueous diffusion.
... Mass Transfer in the Extraction Module. The reaction between Cu 2+ and LIX65N (RH) in kerosene is given by 14,15 In addition, the reaction between CuL 2in the solution pH range 3-7 and Aliquat 336 (RCl) in kerosene can be expressed as 12 Under the conditions studied, Aliquat 336 cannot extract Cu 2+ because the anionic ligand's chloride ions are not present in sufficient excess over Cu 2+ . Figure 1 shows the concentration profiles of the various species around the fiber considering that the organic solvents can readily wet the hydrophobic microporous membranes. ...
... The pseudo-first-order rate constants are k′ 1 ) k 1 -[RH] fi /[H + ] f and k′ -1 ) k -1 [H + ] f in eq 4, and k 1 and k -1 are 1.5 × 10 -8 m/s and 1.8 × 10 -8 m 2 /(mol s) at 298 K, respectively. 14,15 In the description of mass transfer, the following assumptions have been made: (1) The diffusion of species through the membrane pores is much slower than that through the organic stagnant layer; 16 If the transport parameters are known, then we can calculate the extraction rate J Cu,E by solving the system of eqs 3-8 with the additional condition of eq 9. ...
... The dashed curves are calculated from the proposed models of the individual extraction systems Cu 2+ -LIX64N-HCl and CuL 2--Aliquat 336-HCl. 15,21 The solid curves are obtained by assuming that the amount of Cu(II) extracted is the sum of the amounts of Cu 2+ and CuL 2-; that is Evidently, this "additive" concept is not valid. On the basis of the color change of the feed phase during the experiment, it is proposed that Cu 2+ ions are preferentially extracted by LIX64N rather than CuL 2by Aliquat 336. ...
The simultaneous extraction recovery of free Cu2+ ions and ethylenediaminetetraacetic acid (EDTA)-chelated anions from chloride solutions into a stripping HCl solution with a mixture of LIX64N and Aliquat 336 was studied in two hollow-fiber modules. A kinetic model is presented that considers possible mass transfer steps, including aqueous-layer diffusion, interfacial chemical reaction, membrane diffusion, and organic-layer diffusion. In particular, the effects of the preferential extraction of one metallic species and the mutual interaction of the two extractants were also corrected in this model on the basis of the results for individual extraction systems. The calculated time profiles of the total Cu(II) concentrations were in reasonable agreement with the experimental data (standard deviations of 11% in both the extraction and back-extraction modules). Finally, the rate-controlling mechanisms of such nondispersive extraction processes were quantitatively identified and are discussed in terms of a comparison of the resistance of each mass transfer step.
... In addition to the reaction kinetics and diffusibility, the new insights are also valuable for other applications. For instance, the simulations can be extended to model novel processes, such as microchannel [34] and hollow-fibre membrane [35]. In comparison with conventional extraction circuits, micro-reactors have enhanced mass transfer and lower energy consumption. ...
... This new process can be applied on a smaller scale than in a typical metallurgical plant. In this process, the interfacial reaction plays a more critical role [35]. One of the potential applications of this study is that cashew-based hydroxyoxime can be incorporated within membrane extraction. ...
... In addition to the reaction kinetics and diffusibility, the new insights are also valuable for other applications. For instance, the simulations can be extended to model novel processes, such as microchannel [34] and hollow-fibre membrane [35]. In comparison with conventional extraction circuits, micro-reactors have enhanced mass transfer and lower energy consumption. ...
... This new process can be applied on a smaller scale than in a typical metallurgical plant. In this process, the interfacial reaction plays a more critical role [35]. One of the potential applications of this study is that cashew-based hydroxyoxime can be incorporated within membrane extraction. ...
Solvent extraction has been ubiquitously used to recover valuable metals from wastes such as spent batteries and electrical boards. With increasing demands for energy transition, there is a critical
need to improve the recycling rate of critical metals, including copper. Therefore, the sustainability of reagents is critical for the overall sustainability of the process. Yet, the recycling process relies on functional organic compounds based on the hydroxyoxime group. To date, hydroxyoxime extractants
have been produced from petrol-based chemical feedstocks. Recently, natural-based cardanol has been used to produce an alternative hydroxyoxime. The natural-based oxime has been employed to recover valuable metals (Ga, Ni, Co) via a liquid/liquid extraction process. The natural compound has a distinctive structure with 15 carbons in the alkyl tail. In contrast, petrol-based hydroxyoximes have only 12 or fewer carbons. However, the molecular advantages of this natural-based compound over the current petrol-based ones remain unclear. In this study, molecular dynamics simulation was employed to investigate the effect of extractant hydrocarbon chains on the extraction of copper ions.
Two hydroxyoxime extractants with 12 and 15 carbons in the alkyl chain were found to have similar interactions with Cu2+ ions. Yet, a slight molecular binding increase was observed when the carbon chain was increased. In addition, lengthening the carbon chain made the extracting stage easier and the stripping stage harder. The binding would result in a lower pH in the extraction step and a lower pH in the stripping step. The insights from this molecular study would help design the extraction circuit
using natural-based hydroxyoxime extractants. A successful application of cashew-based cardanol will improve the environmental benefits of the recycling process. With cashew-producing regions in developing countries, the application also improves these regions’ social and economic sustainability.
... In addition to the reaction kinetics and diffusibility, the new insights are also valuable for other applications. For instance, the simulations can be extended to model novel processes, such as microchannel [34] and hollow-fibre membrane [35]. In comparison with conventional extraction circuits, micro-reactors have enhanced mass transfer and lower energy consumption. ...
... This new process can be applied on a smaller scale than in a typical metallurgical plant. In this process, the interfacial reaction plays a more critical role [35]. One of the potential applications of this study is that cashew-based hydroxyoxime can be incorporated within membrane extraction. ...
Solvent extraction has been ubiquitously used to recover valuable metals from wastes such as spent batteries and electrical boards. With increasing demands for energy transition, there is a critical need to improve the recycling rate of critical metals, including copper. Therefore, the sustainability of reagents is critical for the overall sustainability of the process. Yet, the recycling process relies on functional organic compounds based on the hydroxyoxime group. To date, hydroxyoxime extractants have been produced from petrol-based chemical feedstocks. Recently, natural-based cardanol has been used to produce an alternative hydroxyoxime. The natural-based oxime has been employed to recover valuable metals (Ga, Ni, Co) via a liquid/liquid extraction process. The natural compound has a distinctive structure with 15 carbons in the alkyl tail. In contrast, petrol-based hydroxyoximes have only 12 or fewer carbons. However, the molecular advantages of this natural-based compound over the current petrol-based ones remain unclear. In this study, molecular dynamics simulation was employed to investigate the effect of extractant hydrocarbon chains on the extraction of copper ions. Two hydroxyoxime extractants with 12 and 15 carbons in the alkyl chain were found to have similar interactions with Cu 2+ ions. Yet, a slight molecular binding increase was observed when the carbon chain was increased. In addition, lengthening the carbon chain made the extracting stage easier and the stripping stage harder. The binding would result in a lower pH in the extraction step and a lower pH in the stripping step. The insights from this molecular study would help design the extraction circuit using natural-based hydroxyoxime extractants. A successful application of cashew-based cardanol will improve the environmental benefits of the recycling process. With cashew-producing regions in developing countries, the application also improves these regions' social and economic sustainability.
... NDSX using membrane contactors and ELM have demonstrated a great potential in a wide variety of applications involving recovery and/or removal of many species from aqueous solutions. Concerning the extraction of copper from aqueous solutions, most of the studies have been focused on the treatment of acidic feed solutions (Valenzuela et al., 1999(Valenzuela et al., , 2005Lin and Juang, 2001;Sengupta et al., 2006). Recently, Kocherginsky (2006, 2007) developed a hollow fibre supported liquid membrane system for recovering copper from spent ammoniacal etching solutions. ...
... Hu and Wiencek (1998) reported the extraction of copper from acidic solutions using LIX 84 as extractant and the resistance due to chemical reaction was found dominant in most cases. In addition, Lin and Juang (2001) showed that the extraction of copper in acidic medium with LIX 64N was governed by the aqueouslayer diffusion or chemical reaction depending on the concentration of carrier. ...
This work aims to study the recovery of copper from ammoniacal aqueous solutions using hydrophobic propylene membrane contactors. The hydroxyoxime LIX 84-I and the β-diketone LIX 54 (both from Cognis) were used as extractants. The results obtained showed that practically all the copper content was removed from the ammoniacal feed solutions. The recovery of copper reached nearly 100% in several extraction-stripping experiments. The results were compared with the ones obtained by applying the emulsion liquid membranes (ELM) technique.
... The diffusion of species through the membrane can be approximated by the diffusion through a cylindrical wall. The individual mass transfer coefficient k m can be expressed as [48,49]: ...
... Results of these studies varied significantly due to more complex geometry of the system, the influence of module wall, the irregularity of fiber spacing and diameters, the fiber movement during operation, the inlet and outlet effects [52], possible channeling between fibers [54] and deformation of fibers during process. Nevertheless, the value of k o in the shell side is around 10 −3 cm/s [38,49,51,52] and can be additionally improved by a more efficient fiber arrangement and improved liquid flow patterns inside the module. ...
Supported liquid membranes (SLM) are studied in various fields like analytical, inorganic and organic chemistry, chemical engineering, biotechnology and biomedical engineering. This technique offers the advantages of active transport, possible usage of expensive carriers, high selectivity, easy scale-up, low energy requirements, low capital and operating costs, etc. This paper gives a brief overview of mechanism and kinetic studies of SLM based separations. The problems with stability and possible applications of SLM are also reviewed.
... Besides TFA, other studies reported that LIX64N [222] and di (2-ethylhexyl)phosphoric acid (D2EHPA) [223] which are dissolved in kerosene could also be potentially employed to extract Cu(II) ions from aqueous solution via MLLE process. Both studies indicated the experimental data agreed reasonably with the calculated time profiles of aqueous metal concentrations based on the principles of extraction reactions and transport properties of the relevant geometry (hollow fiber). ...
Membrane contactor as a high-performance and cost-effective separation technology has attracted considerable attentions for environmental protection. It offers promising advantages as it can combine with absorption, desorption, extraction and even distillation in one equipment. In this article, the membrane contactor processes are briefly introduced followed by comprehensive review on the latest progresses for environmental applications. Greenhouse gas capture by membrane gas absorption and the membrane development are critically reviewed. In addition, water and wastewater treatments through various membrane contactor processes are discussed for applications such as oil and dye removal, heavy metal ions and radioactive materials separation, ammonia recovery as well as degasification. This article also highlights the current status and future direction of the technology to provide indications for industrial implementation. Although there are not many pilot/full-scale plants using membrane contactor technology in operation, an increasing interest is expected in near future due to strong potential of the technology for environmental applications.
... There are some theoretical approaches to predict the performance of membrane process. These approaches are based on some models such as mass transfer model (Bhattacharjee and Datta 1997;Lin and Juang 2001), gel-polarization model (Palacios et al. 2002), osmotic pressure model (Wijmans et al. 1984;Ghose et al. 2000), Brownian diffusion model (Samuelsson et al. 1997), and shear-induced diffusion model (Kromkamp et al. 2002;Vincent Vela et al. 2007). The complexity of these mathematical models and their nonuniversality would limit their application. ...
In this study, a hydrophilic polyethersulfone membrane was used to modify the expensive and low efficient conventional treatment method of wheat starch production that would result in a cleaner starch production process. To achieve a cleaner production, the efficiency of starch production was enhanced and the organic loading rate of wastewater that was discharged into treatment system was decreased, simultaneously. To investigate the membrane performance, the dependency of rejection factor and permeate flux on operative parameters such as temperature, flow rate, concentration, and pH of feed were studied. Response surface methodology (RSM) has been applied to arrange the experimental layout which reduced the number of experiments and also the interactions between the parameters were considered. The maximum achieved rejection factor and permeate flux were 97.5% and 2.42 L min−1 m−2, respectively. Furthermore, a fuzzy inference system was selected to model the non-linear relations between input and output variable which cannot easily explained by physical models. The best agreement between the experimental and predicted data for permeate flux was denoted by correlation coefficient index (R2) of 0.9752 and mean square error (MSE) of 0.0072 where defuzzification operator was center of rotation (centroid). Similarly, the maximum R2 for rejection factor was 0.9711 where the defuzzification operator was mean of maxima (mom).
... Ölçülen kütle aktarımı katsayıları ile hesaplanan değerler genelde aynı eğilime sahiptir, fakat ölçülen değerler %30-45 daha yüksektir. Sonuç olarak, bu çalışmada kütle aktarımı katsayılarının hesabında daha uygun korelasyonların kullanılması, modelin doğruluğu ve geçerliliği hususunda uygun olacaktır[101].Bir başka kütle aktarımı çalışması, Lin ve Juang tarafından gerçekleştirilmiştir. Bu çalışmada, boşluklu fiber modüller kullanılarak bakır (II) ekstraksiyonu gerçekleştirilmiştir. Araştırmacılar elde ettikleri deneysel sonuçları, kütle aktarımı modelinden elde ettikleri sonuçlarla karşılaştırmışlar ve sonuç olarak deneysel verilerin modelden elde edilen verilerle oldukça yakından örtüştüğünü bulmuşlardır[102].Nagaraj ve arkadaşları, ozmotik membran distilasyon prosesinde meydana gelen kütle transferini incelemişler ve bu çalışmada düz levha membran modülünü kullanmışlardır. Kullanılan membranın gözenek boyutları 0.05 µm ve 0.2 µm olup, ortalama membran kalınlığı 150 µm'dir. ...
Membranlar, son yıllarda oldukça popüler arıtım sistemleri arasında ön planda yer almaktadır. İçme suyu arıtımı, atıksu arıtımı ve deniz suyundan içme suyu eldesi gibi birçok alanda membranların kullanımı yaygınlaşmıştır. Özellikle membranların atıksuların arıtımı konusunda klasik sistemlere karşı olan üstünlükleri ve gün geçtikçe düşüş gösteren membran materyali maliyetleri, bu sistemlerin tercih edilebilir seçenekler arasına girmesini sağlamıştır. Membranların oldukça farklı türleri bulunmaktadır. Bunlar arasında mikrofiltrasyon (MF), ultrafiltrasyon (UF), nanofiltrasyon (NF) ve ters osmoz (RO) en fazla ilgi çeken proseslerdir. Membran proseslerde en önemli hususlardan biri, membrandan geçen ve membranda tutulan bileşen miktarlarıdır. Burada kütle aktarımı kavramı ortaya çıkmaktadır. Kütle aktarımı, arıtım sistemlerinin projelendirilmesinde ve verimlilik hesaplarının yapılmasında oldukça büyük önem taşıyan bir olaydır. Membranlarda gerçekleşen kütle aktarımının incelenmesi, yukarıda söz edilen konulara ek olarak, farklı membran tiplerinin karşılaştırılması açısından da önem taşımaktadır. Bu derleme makalesi kapsamında, membranlar ile ilgili genel bilgilere, membranların türlerine, kullanım alanlarına ve modül tasarımlarına yer verilmiş, kütle aktarımı kavramı incelenmiş ve membran arıtım sistemlerinde gerçekleşen kütle aktarımı işlemleri değerlendirilmiştir.
... In this section the equations are further expanded to describe the situation with two different stagnant layers in contact with the membrane phase (Fig. 4). This kind of mass transfer is important, for example , in non-dispersive membrane extraction sys- tem [14,35], where organic phase containing extracted species is pumped on one side of a membrane and an aqueous stripping solution is supplied to the other side of the membrane. If a hydrophobic membrane is used, the membrane pores could be filled with organic phase. ...
... These results are in agreement with those previously obtained with PEHFSD tests (Agarwal et al., 2013). Lin and Juang (2001), who reported the extraction of Cu(II) from a sulphate medium with LIX64N, also concluded that the extraction process was controlled by aqueous-layer diffusion and interfacial reaction, but that the limiting step might shift to the aqueous-layer diffusion at pH > 4. Fig. 6 shows the plot of the resistance of the chemical reaction against the activity of the hydrogen ions, obtained under constant ionic strength (i.e. approximately 0.5 M). ...
The extraction of copper from sulphuric/sulphate solutions using a hollow fibre module as contactor was studied. The aldoxime Acorga M5640 was used as an extractant. The effects on the extraction rate of the flow-rates, the concentrations of copper and extractant, pH, and the presence of Na2SO4 in the feed phase were investigated. The overall mass transfer coefficient for copper extraction was calculated from the experimental data and was compared with the value evaluated by the resistance in the series model. The extraction process was found to be governed by the diffusion in the boundary aqueous layer and also by the chemical reaction. The kinetic data obtained were used to simulate the extraction of copper with the pseudo-emulsion-based hollow fibre with strip dispersion technique. The accordance between the results thus calculated and the experimental data was found to be satisfactory, particularly for dilute feed solutions. (C) 2014 Institute of Chemistry, Slovak Academy of Sciences
... Recently, the use of a hollow-fiber supported liquid membrane (HFSLM) has come to be regarded as an effective method for the simultaneous extraction and recovery of components of interest from a very dilute solution in the feed, by means of a single-unit operation [23][24][25]. The advantages of HFSLM over traditional separation techniques include lower capital and operating costs, lower energy consumption, low diluent usage, and high selectivity [26][27][28]. These advantages make HFSLM particularly suitable for application in the enantioseparation of compounds in pharmaceutical industrial wastewater. ...
Pharmaceutical wastewater may contain high-value pharmaceutically active compounds such as amlo-dipine. A hollow-fiber supported liquid membrane (HFSLM) process was developed and applied in the pretreatment of pharmaceutical wastewater for (S)-amlodipine recovery. The HFSLM system contained O,O 0 -dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) in the liquid membrane phase and b-cyclodextrin in the stripping phase. The effects of various chemical parameters, including the concentration of the chiral selector in the stripping phase, as well as the type of organic diluent and the carrier concentration in the membrane, were also investigated. Several diluents – hexane, 1-decanol, chlorobenzene, benzene, dichloromethane, ethylene dichloride, and chloroform – with different polarity indexes, from 0.1 to 4.1, were used. The results found that the polarity of the diluents was the main factor influencing the extraction performance and stability of the liquid membrane. Decreasing the polarity of the diluent could prolong membrane stability, but the percentages of extraction and stripping decreased as well. The longest lifetime (150 min) was obtained by using 1-decanol, with a polarity index of 1.8, as a diluent. Ó 2013 Elsevier B.V. All rights reserved.
... phobic hollow fibers (HF) allow circulation of two fluid phases whereas the organic extractant phase is also embedded in the pores of the HFs. Many works have reported the analysis of different process configurations, including supported liquid membranes [1][2][3], non-dispersive solvent extraction and contained liquid membranes [4,5], as well as different applications of this technology that range from the recovery of inorganic species [6][7][8][9][10][11][12], as in the cases of Cr(VI) and Cu recoveries, to the separation and concentration of organic compounds [13][14][15]. ...
This works reports on the separation and recovery of copper cations from water streams from the wet peroxide oxidation process (WPO) using emulsion pertraction technology (EP) in hollow-fiber contactors as separation technology. The separation of the metal was enhanced by using LIX622N as a selective extractant, and its concentration took place in a sulphuric acid phase. The ecotoxicity characterization, according to the Vibrio fischeri bioassay of the waters coming from the WPO process, revealed that the presence of a residual copper catalyst gave the oxidized waters the character of being ecotoxic. Nevertheless, the subsequent removal of copper in the EP process produced non-ecotoxic oxidized water. Finally, the recovered copper catalyst obtained as concentrated copper sulphate solution in the emulsion pertraction process was recycled to the oxidation reactor, checking experimentally that the oxidation efficiency was maintained.
... In recent years there has been signiÿcant interest in studying the non-dispersion membrane extraction process. Membrane extraction using microporous polymer as a barrier between the aqueous and organic phases has been used successfully for the removal and concentration of di erent compounds such as metals (Kim, 1984;Yang & Cussler, 2000;Lin & Juang, 2001), organic compounds (Stevanovic, Mitrovic, & Korenman, 1999;Wang, Luo, Cai, Wang, & Dai, 2002) and fermentation products (Tong et al., 1998;Tong, Hirata, Takanashi, & Hano, 1999). ...
Using di-(2-ethylhexyl) phosphoric acid (D2EPHA)/cadmium ion/water as an experimental system, the mass transfer characteristics in hollow fiber modules (HFMs) were studied by Voronoi tessellation method based on normal distribution function, in which the standard variance could be correlative with the packing irregularity of fibers. The theoretical results showed that not only the packing density but also the packing irregularity significantly influenced the mass transfer characteristics in HFMs. For modules with the same densities, the different packing irregularity led to different mass transfer efficiency. The efficiency of modules with moderate packing density was the lowest because of their most serious packing irregularity. Compared with the exponent distribution function used in previous studies, the normal distribution function can determine the effect of packing irregularity on mass transfer performance accurately. The experimental results also showed a high extraction efficiency of cadmium ion from the wastewater by HFMs.
... J/ mol K), A is the frequency factor, E a is the activation energy and T is the absolute temperature. According to the definition of flux given by Lin and Juang[63], the flux of (S)-amlodipine can be presented as: ...
Chiral separation of enantiomers of amlodipine, one of the most commonly prescribed antihypertensive drugs, was examined using the hollow fiber supported liquid membrane (HFSLM) extraction technique. The influence of temperature on enantioseparation of (R,S)-amlodipine via a HFSLM containing the chiral selector O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) was systematically investigated. The parameters affecting the mass transfer such as distribution ratio and flux were determined at different temperatures ranging from 278.15 K to 313.15 K. The thermodynamic parameters, ΔH and ΔG, were determined, and an interesting relationship with stoichiometric value was found: higher temperatures lead to an increase in distribution ratio but a decrease in enantioselectivity. The activation energy (Ea) of the (S)-amlodipine extraction reaction was 71.10 kJ/mol. The chemical reaction between (S)-amlodipine and (+)-DBTA is the mass transfer-controlling step for the enantioseparation of (S)-amlodipine by a hollow fiber supported liquid membrane system.
... The membrane separates both phases and thus eliminates equilibrium limitations, high efficiency is obtained and organic loss can be reduced. 13,14 HFMC-based separation units are very compact and energy efficient. Fast mass transfer is achieved compared to conventional extraction units. ...
In this work, we present the dispersion-free liquid–liquid extraction of copper from aqueous streams in a hollow fiber membrane contactor (HFMC). Copper has been transferred from aqueous solutions to heptane using LIX 84-I (2-hydroxy-5-nonylacetephenone oxime) as extracting agent. In a first step, batch experiments have been performed to identify the extraction kinetics and to measure the partition coefficient of copper aqueous-organic phase system. Then, the continuous recycled-base extraction process has been performed in a HFMC Liqui-Cel® module. The module has been modeled from resistance in series concept to gain the exit concentrations, which are used to develop a dynamic model to calculate the exit concentration of copper from the output of storage tanks. The model has been validated with experimental data at various operating conditions. The integrated process model algorithm was scripted in MATLAB® 7.4 R (a). Simulations have been made for a range of different operating parameters to determine the optimum criterion conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010
... Lin and Juang 82 analysed the mass transfer in hollow fibre contactors for extraction and back-extraction of copper with LIX64N carriers. Two overall mass transport coefficients for the extraction and back-extraction steps were defined by the authors. ...
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
There is a growing environmental and health concern associated with contamination by heavy metals. It has also been intensified due to an increase of the exposure to such pollutants as a result of industrial and technological growth. Therefore, it is necessary to remove heavy metals in contaminated water to eliminate the associated risks. This study focused on the removal of heavy metal ions using silica sulfuric acid (SSA). A comprehensive study was conducted to assess the effect of different factors on the adsorption by SSA as well as selectivity properties of the adsorbent, kinetic and thermodynamic studies of the adsorption process. A batch test was used to remove heavy metals from a multi-element solution containing Ni(II), Pb(II), Mn(II), Cu(II), and Cd(II). The results showed that removal rate reached its peak at pH, string time, and adsorbent amount equal to 8, 60 min, and 0.04 g/mL of solution, respectively. The removal efficiency of Ni2+, Cd2+, Mn2+ dropped by increasing the volume of solution and smoothed at 150 mL while the removal of Pb2+ and Cu2+ did not vary with the volume. The removal efficiency by SSA was decreased as Pb > >Mn > >Ni ≥ Cu > Cd. In general, SSA successfully removed heavy metals from contaminated water. HIGHLIGHTS
The first study of heavy metal removal using SSA as an adsorbent.;
A comprehensive study of adsorption by SSA including mechanism, thermodynamics, and kinetics.;
The effect of different factors on the adsorption has been investigated.;
Adsorption of heavy metals has been achieved for both synthetic and real samples.;
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.
RESUMO – O processo de extração por solventes utilizando contactores com membranas tem se mostrado eficaz em processos hidrometalúrgicos, sobretudo pela capacidade de separar íons metálicos seletivamente de soluções aquosas, utilizando membranas do tipo fibra oca como suporte sólido entre as fases, evitando a formação de emulsões, proporcionando uma grande área superficial de contato, reduzindo o consumo de reagentes. O trabalho simulou a extração de íons cobre utilizando LIX84I® como extrator e querosene como solvente orgânico. As simulações foram realizadas no software COMSOL Multiphysics, baseadas na modelagem computacional para análise da transferência de massa e fluidodinâmica em todos os subdomínios da membrana: fase aquosa, no interior da fibra, fase poro e fase orgânica, no exterior da membrana. Os resultados foram bastante satisfatórios, proporcionando boa predição na distribuição da concentração, fluxo total de transferência de massa e perfil de escoamento. 1. INTRODUÇÃO A extração de metais por membranas é estudada desde os anos 70, com bons resultados, com vantagens sobre o processo de extração tradicional por solvente, pois efetua a separação de maneira econômica, evita a formação de emulsões, reduz o consumo de reagentes e não produz efeitos tóxicos ou reações prejudiciais para os produtos (Kolev et al., 1997; Pabbly et al., 2009). O termo " contactor com membrana " é usado para identificar os sistemas de membranas que são empregados para manter duas fases em contato. Ao contrário da ideia tradicional de membranas como sendo um meio para realizar operações de separação, graças à sua seletividade, contactores com membranas porosas não oferecem seletividade para uma determinada espécie em relação à outra, mas simplesmente agem como uma barreira entre as fases envolvidas, permitindo o seu contato em uma área interfacial correspondente bem definida. Sendo as duas fases separadas por uma membrana, não há mistura entre elas e o fenômenos de dispersão não ocorre. As espécies são transferidas de uma fase para a outra apenas por difusão. (Criscuoli, 2009; Reed et al., 1995).
The separation of Hg(II) and As(V) from produced water by hollow fiber contactors was investigated. Two identical hollow fiber modules were employed. The first module was used for extraction, while the second module was used for stripping. The optimum conditions achieved were 14% (v/v) of Aliquat336, 0.07 M thiourea, volumetric flow rate of 100 mL/min for aqueous solution and 0.02 M HCl of stripping solution. At such conditions, the maximum extraction of Hg(II) and As(V) attained 100% and 78.78%, respectively. Concurrently, the maximum stripping of Hg(II) and As(V) reached 47.88% and 6.66%, respectively. The overall mass transfer coefficients of Hg(II) and As(V) extraction were 2.31×10−6 and 1.15×10−6m/s, while the Hg(II) and As(V) stripping exhibited the overall mass transfer coefficients of 8.37×10−7 m/s and 9.05×10−7 m/s, respectively. Mass transfer coefficients of the organic layer diffusion (k0) had the most effect on the overall mass transfer coefficients.
This article gives a general outline on membrane contactors, providing basic information on how these systems work, the unit operations that they can cover, the membranes used, the main advantages and disadvantages with respect to conventional devices, as well as the most studied applications. The aspects of these membrane operations that still need to be improved for enlarging and consolidating their areas of application are also reported. The goal is to furnish a general knowledge on the subject, underlining potentialities, problems, and research trends in the field.Keywords:membrane contactors;microporous membranes;contact between phases;gas–liquid operations;liquid–liquid operations;distillation
This study aimed to recover and remove copper from industrial model wastewater solution by
non-dispersive solvent extraction. Two mathematical models have been developed to simulate the
performance of an integrated extraction – stripping process based on the use of hollow fiber contactors
by response surface method. The models allow one to predict the time dependent efficiencies of the
two phases involved in an individual extraction or stripping processes. The optimal recovery efficiency
parameters were determined as 227 g/L of H2SO4 concentration, 1.22 feed/strip ratio, 450 mL/min flow
rate (115.9 cm/min. flow velocity) and 15 volume % LIX 84-I concentration in 270 min by central
composite design. At these optimum conditions, the experimental value of recovery efficiency was
95.88% which was in close agreement with the 97.75% efficiency value that predicted by the model. At
the end of the process, almost all of the copper in the model wastewater solution was removed and
recovered as CuSO4.5H2O salt which can be reused in the copper electroplating industry
The separation experiments of amoxicillin via hollow fiber supported liquid membrane (HFSLM) were performed under various operating conditions to find the optimal parameters i.e. pH, feed concentration, carrier concentration, and flow rates of feed and stripping solution. Percentages of extraction and recovery of amoxicillin from the feed phase reached 85.21% and 80.34%, respectively. The aqueous-phase mass transfer coefficient (kf) and organic-phase mass transfer coefficient (km) were reported to be 3.57 × 10−2 and 0.70 × 10−2 cm/s, respectively. Furthermore, a mathematical model was developed to predict the concentration of amoxicillin at different times. The results showed promising agreement with experimental data.
Waste printed circuit boards (WPCBs) have an inherent value because of nonferrous metal copper and noble metals. From the viewpoint of resource recycling and environmental protection, it is significant to recover metal materials from WPCBs. In this study, metal powders recovered from WPCBs were used to prepare ultrafine copper oxide powders using a microemulsion reaction. First, WPCBs were pretreated to obtain the metal powders with a copper content of 86.1% using a mechanical physical method. The leaching of the metal powders was carried out in a sulfuric acid solution by adding chloride and copper ions under aeration condition. By a solvent-extraction technology, copper ions in the leaching solution were extracted by N902 extractant and the raffinate was used to leach metal powders again. The loaded organic phase (N902 extractant) was stripped by an oxalic acid solution to form a microemulsion system. Ultrafine copper oxalate precipitations were produced in the microemulsion interfaces, and then calcined to form ultrafine copper oxide powders. X-ray diffraction and transmission electron microscopy results showed that the ultrafine copper oxide powders had an average size of approximately 100 nm.
The generation of liquid effluents containing organic and inorganic residues from industries present a potential hazardousness for environment and human health, being mandatory the elimination of these pollutants from the respective solutions containing them. In order to achieve this goal, several techniques are being used and among them, supported liquid membranes technologies are showing their potential for their application in the removal of metals contained in liquid effluents. Supported liquid membranes are a combination between conventional polymeric membranes and solvent extraction. Chemical and metallurgical industries are the main producers of metal-bearing liquid effluents that due to the toxic character of metals. Several drawbacks of the often known as classical removal or separation technologies reduced the grade of effectiveness in the elimination of metals, principally when the aqueous solution is complex in its composition or when the metal is presented in the liquid solution at very low concentrations. Industrial processing of chemicals almost invariably leads to streams with multiple components that must then be subjected to a train of separation or purification operations to isolate the desired product. As an alternative method to wastewater pretreatment technology, supported liquid membrane (SLM) has been paid extensive attention due to its specific characteristics. As a result, SLM has been considered as a promising technology. The future of these technologies seems to be highly exciting and promising.
The aim of this study was to check the feasibility of non-dispersive solvent extraction to recover copper from ammoniacal solutions using hollow fibres as contactors. Data of mass transfer using the ®-diketone LIX 54 as an extractant was obtained. The influence of tube and shell hydrodynamics on the extraction rate of copper was studied. The overall mass transfer coefficient of copper was calculated from the experimental data by performing steady state material balance. Simultaneous extraction and stripping experiments were carried out using different volume ratios of feed phase to stripping phase. The results obtained showed that practically all the copper content was removed from the ammoniacal feed solutions. The recovery of copper reached nearly 100% in several extraction-stripping experiments.Le but de cette étude était de vérifier la faisabilité d’extraction par solvant non-dispersif pour la récupération du cuivre de solutions ammoniacales en utilisant des fibres creuses comme contacteurs. On a obtenu les données de transfert de masse en utilisant la dicétone-® LIX 54 comme agent d’extraction. On a étudié l’influence de l’hydrodynamique du tube et de l’enveloppe sur la vitesse d’extraction du cuivre. On a calculé le coefficient global de transfert de masse du cuivre à partir des données expérimentales en effectuant une balance de matériel en régime permanent. On a effectué des expériences simultanées d’extraction et de lavage en utilisant différentes proportions de phase d’alimentation et de lavage. Les résultats obtenus montraient que pratiquement tout le cuivre était enlevé des solutions ammoniacales d’alimentation. La récupération du cuivre atteignait presque 100% dans plusieurs expériences d’extraction-lavage.
The separation of Co(II) from Ni(II) in H2SO4 solution across a hollow fiber membrane containing D2EHPA carriers dissolved in kerosene was studied. The Co(II) was simultaneously re-extracted to a strip phase containing H2SO4. Experiments were conducted to determine the effects of the feed pH (4–5), carrier concentration (0.1–0.5 mol/dm3), strip acidity (0.1–2 mol/dm3), and flow rates of the three phases (200–600 cm3/min). The extraction efficiency for each metal ion was found to increase with increasing flow rate of the feed phase, feed pH, and D2EHPA concentration in the extraction module. Co(II) was preferentially extracted over Ni(II) by D2EHPA under the same extraction conditions. In the extraction module, the separation factor βCo/Ni increased with increasing flow rate of the feed phase and D2EHPA concentration but decreased with increasing feed pH. In the re-extraction module, the recovery of Co(II) increased with increasing the feed pH, D2EHPA concentration, and flow rate of the strip phase but decreased with increasing the strip acidity. At a feed pH of 4, the percent extraction and recovery of Co(II) were 81% and 26.4% (Ni/Co–11% in strip phase), respectively. The percent extraction and recovery for Co(II) using one-stage HFMCs were better than those using two-stage HFMCs.
The influence of temperature on the separation of amoxicillin via HFSLM containing the carrier Aliquat 336 was systematically investigated. Mass-transfer parameters including distribution ratio and flux as well as thermodynamic properties namely ΔH and ΔG were also determined at different temperatures ranging from 278.15 K to 318.15 K. The positive value of the enthalpy change (24.5778 kJ/mol) indicated that the extraction process is endothermic reaction. Further, the positive value of the entropy change (112.0145 J/mol K) and the negative value of the Gibbs free-energy indicated that the extraction process is forward reaction. It was found that by increasing the temperature of the system from 278.15 to 318.15 K, extraction of amoxicillin increased from 81.81% to 89.65% and the stripping of amoxicillin increased from 76.63% to 84.70% respectively. Activation energy (Ea) of amoxicillin extraction was found to be 44.28 kJ/mol. This implied that the chemical reaction was the mass transfer controlling step. The mass transfer coefficients in the membrane phase were found to be less than the mass transfer coefficients in the feed phase within the range of temperatures i.e. 278.15–318.15 K. This implied that the mass transfer process in the membrane phase was the rate controlling step.
An elliptical hollow fiber membrane bundle (EHFMB), which is installed in a shell to form a counter flow tube-and-shell heat exchanger like hollow fiber membrane contactor, is commonly used for air humidity control. EHFMB is usually randomly packed in practical applications because of the randomness in the assembly process. The longitudinal transport phenomena between a randomly distributed elliptical hollow fiber membrane bundle (REHFMB) are studied. To disclose the effects of the random distributions on the transport phenomena, a unit cell containing 20 fibers based on Voronoi tessellation technology and the air flowing axially between the REHFMB is selected as the calculating domains. The governing equations governing the fluid flow and heat transfer between the REHFMB are established and numerically solved. The friction factor and Nusselt number in the unit cell under various fiber distributions, packing fractions (φ), rotation angles (β) and semiaxis ratios (b/a) are then obtained, analyzed, and experimentally validated. It can be found that the elliptical semiaxis ratios, the random distribution in positions, and rotation angles all have effects on the axial transport phenomena between the REHFMB. Further, the random distribution in positions is the dominant factor.
The separation of Co(II) from Ni(II) in a sulfate solution across a hollow fiber membrane containing the sodium salt of Cyanex 302 dissolved in kerosene was studied. The Co(II) was simultaneously re-extracted into a strip phase containing H2SO4 in another hollow fiber membrane. Experiments were conducted to determine the effects of the feed pH (4.55.5), carrier concentration (0.10.4mol/dm3), strip acidity (0.12mol/dm3), and flow rates of the three phases (200 approximate to 600cm3/min). The percent of each metal ion extracted was found to increase with increasing feed pH, Na-Cyanex 302 concentration, and feed flow rate in the extraction module. Na-Cyanex 302 extracted Co(II) preferentially over Ni(II) under identical extraction conditions. Increasing the strip acidity and strip phase flow rate increased the recovery of Co(II) by the re-extraction module. The effect of the flow rate of the organic phase on the percent extraction and re-extraction of Co(II) were negligible. The separation of Co(II) from Ni(II) in sulfate solution was achieved using 0.3mol/dm3 Na-Cyanex 302 as extractant and 2mol/dm3 H2SO4 as stripping solution in HFMCs during a 2h extraction. At a feed pH of 5, the percent extraction and recovery of Co(II) were 84.6% and 43.7% (Ni/Co<0.05 in strip phase), respectively. The extraction efficiency and recovery of Co(II) using one-stage HFMC experiments were better than those using two-stage HFMC experiments.
The role of cations H+ and Na+ on the transport of Nd3+ ions was investigated using microporous Hollow Fiber Supported Liquid Membrane (HFSLM) contactor. Extractant N,N,N′,N′-tetraoctyl diglycolamide (TODGA) diluted with n-dodecane was used as the membrane phase. Di-n-hexyl octanamide (DHOA) was used as a phase modifier for the extractant. Transport of Nd3+ ions and HNO3 was studied at varying concentrations of NaNO3 and HNO3 while keeping total nitrate () concentration nearly constant at 3 M. The extraction equilibrium constant (K ex ) for the complexation reaction was experimentally measured for various conditions. The maximum rate of extraction of Nd3+ ions was observed at an equimolar concentration (1.5 M each) of HNO3 and NaNO3 in feed solution under otherwise identical conditions. A mathematical model has also been developed to simulate this system. Mass balance equations for both acid (HNO3) and TODGA were also incorporated in the model. It was observed that the model results are in good agreement with the experimental data when diffusivity of metal-complex (D m ) and acid-complex (D hm ) through the membrane phase in the pore is 6 × 10−12 m2/s and 1.2 × 10−10 m2/s. Once the values of D m and D hm are estimated by simulation for one set of data, there are no further fitting parameters in the model. The model can then be used in a truly predictive mode for all the remaining data sets.
Hollow fiber supported liquid membrane (HFSLM) is a favorable technique for the pertraction of metal ions, especially at a very low concentration. In this work, the pertraction of silver ions from acidic pharmaceutical wastewater via HFSLM was investigated. Pharmaceutical wastewater containing 30 mg/dm3 of silver ions and 120 mg/dm3 of ferric ions was subjected to HFSLM as a feed solution. LIX 84-I dissolved in kerosene together with sodium thiosulphate solution were selected for use as the liquid membrane and receiving solution, respectively. The influence of ferric ions on the pertraction of silver ions was studied firstly using wastewater with normal ferric ion concentration and secondly using wastewater with ferric ion precipitation in phosphoric acid solution. The highest pertraction of silver ions was achieved by using 0.1 M LIX 84-I and 0.5 M of sodium thiosulphate solution at pH 3.5 of feed and 2 of sodium thiosulphate solution. The flow rates of feed and sodium thiosulphate solutions were 0.2 dm3/min. 0.6 mg/dm3 of silver ions that remained in the wastewater was below the mandatory discharge limit. No effect of normal ferric ion concentration in the wastewater on silver ion pertraction was observed. Crucial parameters were defined to confirm the efficiency and reliability of the system. Finally, the controlling transport regime of silver ion pertraction across HFSLM was determined by the diffusion flux and reaction flux models.
The extraction and stripping of silver ions by hollow fiber supported liquid membrane (HFSLM) was examined. Pharmaceutical wastewater containing 30 mg/dm3 of silver ions was used as the feed solution. LIX 84-I dissolved in kerosene, and sodium thiosulfate pentahydrate solution were used as the liquid membrane and stripping solution, respectively. The influences of several variables on the extraction and stripping of silver ions were investigated. Fluid-flow models for greater accuracy in describing the transport of silver ions from feed phase to stripping phase were developed. The models were calculated by linear algebra. The investigated parameters in the models were axial convections and axial diffusions on both sides, chemical reactions at the feed-liquid membrane and liquid membrane-stripping interfaces as well as the accumulation of silver ions in the system. The mass transfer coefficient in the liquid membrane (km) was determined for use in the models. The final predicted concentrations of silver ions in feed and stripping phases were successfully in agreement with the experimental data. It indicates that the fluid-flow model can accurately estimate the transport of silver ions inside and outside the hollow fibers corresponding to the axial convections, axial diffusions, reactions at the feed-liquid membrane and liquid membrane-stripping interfaces. In accordance with this investigation, the HFSLM shows a practical implication for the use in pharmaceutical wastewater treatment.
Reactive solvent extraction is commonly used in industries to extract organic and inorganic products. In such a process, the solute present in an aqueous solution is extracted into an immiscible solvent containing a specific extracting agent. These experiments are usually carried out in conventional dispersion-based contacting devices such as colunm or mixer-settlers. Under this configuration, two problems arise: the extracting agent (usually a toxic or environmentally harmful compound) is dispersed into the medium and later in the environment and/or permanent emulsions are formed. To overcome these drawbacks, the introduction of a solid membrane between the two fluid phases using a hollow fibre liquidliquid contactor in order to keep a large surface of contact between the two media represents a good alternative. Two selected examples will be shortly presented in this article to illustrate the interest of this technology that uses the same membrane for the extraction of organic and inorganic compounds from aqueous solutions.
Extraction of copper from nitrate/nitric acid aqueous solutions was studied using a HF Membrane Module and four LIX reagents (LIX® 860N-I, LIX® 984N, LIX® 84-I, and LIX® 65N) containing different active compounds (ketoximes and/or salicylaldoximes). Kinetic experiments varying the flow rates of both phases, aqueous and organic, and the extractant concentration were carried out to compare the extraction rate and efficiency from nitrate-aqueous media. A mathematical model based on the “aqueous extraction mechanism” in which the chemical reaction takes place in an aqueous-reaction zone was applied to determine the individual resistances of the copper mass-transfer process. It was found that the fractional resistance due to chemical reaction in the aqueous reaction zone, which varied from 92.5% to 95.8% in the order LIX® 860N-I < LIX® 984N < LIX® 84-I < LIX® 65N, controlled the total rate of the hollow-fiber copper extraction from nitrate aqueous media.
Extraction separation of Cu(II) and Co(II) from sulfuric wastewater is studied with hollow fiber renewal liquid membrane (HFRLM) technique. The organic solution of LIX 984N in kerosene is used as the liquid membrane phase to selectively separate and concentrate Cu(II) from aqueous solution; and the extractant of CYANEX 272 is used as carrier to remove and concentrate Co(II) from aqueous solution. In the selective separation process, LIX 984N has good selectivity on Cu(II); the interactions among metal ions can be negligible; the pH in the feed aqueous solution has significant influence, while the influence of hydrogen ion concentration in the stripping phase is slight. The removal efficiency of Cu(II) increases with the increasing flow rate on lumen side, while decreases with the increasing flow rate on shell side. The results of lab-scale cascade experiments show that the HFRLM technique is a promising treatment method for simulated sulfuric wastewater containing copper and cobalt with separation factor higher than 100. The Cu(II) and Co(II) concentrations in the raffinate are lower than 0.50mgL−1 and 1.0mgL−1, respectively, which are both below the standard of wastewater discharge in China. Based on the surface renewal theory, resistance-in-series model and mass balance law, a corresponding mass transfer mathematical model is developed; and the calculated results are in good agreement with experimental data.
To develop an efficient extractor, a falling-film contactor with polypropylene hollow fibers as packing materials was used to extract phenol and acrylic acid from an aqueous phase with kerosene containing 30% (v/v) tributyl phosphate (TBP). The two fluids were added to the top of the extractor and due to the different affinity of the two phases, the organic phase would spread to a thin film on the fiber surface and the aqueous phase would spread on the organic phase, mass transfer could occur during the falling process. The flow characteristics in the extractor were studied with a theoretical model, by which the flow status in the module can be predicted and provide a way to select suitable membrane materials for a specified extraction system. Studies on the mass transfer characteristics showed that falling-film extractor using hollow fiber as packing is highly efficient because of a very large mass transfer area and can be operated at extreme phase ratios in comparison with an extraction column.
The recovery of copper from ammoniacal medium using non-dispersive solvent extraction (NDSX) with hollow fibres as contactors was studied. The β-diketone LIX 54 was used as an extractant. The influence of the flow rates, initial concentration of copper in the aqueous feed phase and concentration of extractant on the extraction rate was examined. The experimental values of the overall mass transfer coefficients for extraction were compared with the ones predicted by the resistance in series model. Simultaneous extraction and stripping experiments were carried out using two hollow fibre modules under several operating conditions. The results obtained showed that practically all the copper content was removed from the ammoniacal feed solutions. The recovery of copper attained 96–100% and concentration ratios of about 40-fold could be achieved. These results were then compared with the ones obtained by applying the emulsion liquid membranes separation technique.
The residence time distribution (RTD) curves were measured to observe the shell-side flow status in hollow fiber modules (HFMs) with different packing densities, and with 30%TBP in kerosene/phenol/water as experimental system, the membrane extraction was carried out in three polypropylene HFMs in counter-current flow. A random distribution model described by the Voronoi tessellation method based on normal distribution function was proposed to determine the effect of random packing on the flow status and mass transfer characteristics. The standard deviation in normal distribution function represented the packing irregularity in commercial HFMs. So the random distribution model related the packing irregularity with the flow status and mass transfer performance in random packing modules. The theoretical calculation and experimental results indicated that the random packing of fibers caused the non-ideal flow and significant decrease in mass transfer performance; furthermore, the non-ideal flow in shell side had an influence not only on the mass transfer performance in shell side but also on that in lumen side.
The removal and recovery of copper from aqueous solutions using hollow‐fiber membrane contactors were studied. Single extraction was performed at different flow rates of phases, the concentrations of LIX 84‐I in the membrane, the contents of copper in the feed phase, and the aqueous media. The overall mass transfer coefficient for copper extraction was calculated from the experimental data and was also evaluated by the conventional resistance in series model. The relative contribution of the resistance due to the chemical reaction to the overall resistance to mass transfer was found significant. The integration of the extraction and stripping stages was carried out in two hollow‐fiber modules. A few tests were also carried out with LIX 54 as a carrier for comparison. The results obtained showed that practically all the copper content was removed and recovered from the ammoniacal and sulfuric feed solutions. The results were then compared with the ones obtained by applying the emulsion liquid membranes technique. Finally, the emulsion phase with LIX 84‐I was used in a single hollow‐fiber module to perform an extraction‐stripping experiment.
This work focuses on the analysis of the long-term performance of a non-dispersive extraction process applied to the separation and concentration of hexavalent chromium contained in ground waters using Aliquat 336 as a extractant. Working with raw ground waters of high Cr(VI) concentration (700mg/l), the influence of the temperature (20, 40 and 60°C) and the influence of those interferences caused by the presence of competitive anions in the ground waters were studied in discontinuous mode. In continuous mode, the performance of the system for long periods of time was analysed and it was observed that the system is stable since the outlet concentration of Cr(VI) in the ground water and in the back-extraction solution (10–20g/l) remains constant. Finally, the kinetic model of the separation is included at 40°C and the value of the diffusivity and mass transport constants (Km=1.47×10−7m/s and D=6.66×10−11m2/s) are calculated using equations from the literature and the values of the extraction equilibrium parameter (0.035) and repart constant in the back-extraction (13) were obtained by a comparison of experimental and simulated data.
The enantioselective separation of levocetirizine via a hollow fiber supported liquid membrane was examined. O,O′-dibenzoyl-(2R,3R)-tartaric acid ((−)-DBTA) diluted in 1-decanol was used as a chiral selector extractant. The influence of concentrations of feed and stripping phases, and extractant concentration in the membrane phase, was also investigated. A mathematical model focusing on the extraction side of the liquid membrane system was presented to predict the concentration of levocetirizine at different times. The extraction and recovery of levocetirizine from feed phase were 75.00% and 72.00%, respectively. The mass transfer coefficients at aqueous feed boundary layer (kf
) and the organic liquid membrane phase (km
) were calculated as 2.41×102 and 1.89×102 cm/s, respectively. The validity of the developed model was evaluated through a comparison with experimental data, and good agreement was obtained.
The well-documented metal cation selectivity of macrocyclic ligands makes them excellent candidates for incorporation into Liquid Membranes (LMs). There is still much interest from researcher in this association because the improvement of the selectivity is one of the main areas of interest. This review aims to provide informations about the improvements in terms of selectivity, transport rates and stability of LM in metals separation in the recent past. The number of polymer inclusion membrane investigations with macrocycle carrier concerns firstly the morphology of the membrane to know the microstructure of the membrane. It is noticed that there is an increased interest in the incorporation of calixarene compounds in supported LM to improve the selectivity. A hollow fiber-supported LM module impregnated with calyx [4] napthaocrown-6 has been investigated for the separation of Cs (I) from simulated High Level Waste. The bulk LM proved to be an essential tool to investigate the performances of novel macrocyclic carriers. Few investigations have been carried out to incorporate hollow fiber LM module and macrocyclic extractant. The major drawbacks are the cost of macrocycle carriers and their difficult use with membrane module. This review of 88 publications shows that the knowledge gained in each technique must be considered as growing.
A hollow fiber supported liquid membrane (HFSLM) containing the chiral selector O,O -dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) was characterized for the enantioseparation of (R,S)-amlodipine. The influence of various chemical parameters, including the concentration of feed and receiving phases, as well as the carrier concentration in the membrane, were also investigated. Valuable knowledge on the transport mechanisms within this system was thus attained. Furthermore, a mathematical model focusing on the extraction side of the liquid membrane system was presented in order to predict the concentration of (S)-amlodipine at different times. The extraction and recovery of (S)-amlodipine from feed phase were 77.50% and 72.50%, respectively. Extraction equilibrium constant (K ex), distribution ratio (D), perme-ability (P) and mass transfer coefficients were determined. The aqueous-phase mass-transfer coefficient (k f) and organic-phase mass-transfer coefficient (k m) were reported to 2.74 × 10 −2 and 2.52 × 10 −2 cm/s, respectively. The results showed promising agreement with the experimental data.
The transport behavior of Hg2+ from aqueous solution through a flat‐sheet supported liquid membrane has been investigated by the use of calix[4]arene derivatives (1 and 2) as carriers and Celgard 2400 and Celgard 2500 as the solid support. The effect of solvent type and anions such as chloride and nitrate ions on the transport of Hg2+ was examined. A Danesi mass transfer model was used to calculate the permeability coefficients for each parameter studied. The highest values of permeability were obtained with 2‐nitrophenyloctyl‐ether (NPOE) solvent and the influence was found to be in the order of NPOE>chloroform>xylene. The transport efficiency on the liquid membrane transport was dependent on the type of solvent, anion, and carrier.
Hollow fiber supported liquid membrane (HFSLM) is a favorable method to extract both valuable compounds and heavy metal pollutants such as chromium, copper, and nickel at a very low concentration. In this work, the extraction of Cu(II) by LIX84I dissolved in kerosene was theoretically and experimentally investigated. A model to estimate the percentage of extraction of copper ions from synthetic water considering the effect of reaction flux in membrane phase of the HFSLM system was studied. H2SO4 solution was used as the stripping solution. The facilitated transport mechanism of the chemical reaction at the feed-membrane interface was taken into account in the model equations. The percentage of copper ion extraction was plotted against its initial concentration in feed and also feed flow rate. Subsequently, the separation time and separation cycle were determined in accordance with the simulated values of copper ion concentration and the feed flow rate from the model. The modeled results were in good agreement with the experimental data at the average percentage of deviation about 2%.
In this paper, hollow fiber renewal liquid membrane (HFRLM) and hollow fiber supported liquid membrane (HFSLM) were used to simultaneously remove and recover copper(II) from aqueous solutions, and the transport performance of these two techniques were compared under the similar conditions for the system of CuSO4 +D2EHPA in kerosene +HCl. The results showed that the HFRLM process was more stable than the HFSLM process. The HFRLM process had a higher overall mass transfer coefficient than that of HFSLM process in single-pass experiments. These were because the renewal effect of the liquid membrane layer could reduce the mass transfer resistance of the lumen side and replenish the loss of the membrane liquid in the HFRLM process. The transport results were better in the HFRLM process than that in the HFSLM process with recycling experiments. Therefore, HFRLM technique is a promising method for simultaneous removal and recovery of heavy metal from aqueous solutions.
Equilibrium at an interface is a key assumption in the traditional theory, describing a relationship of a time lag and diffusion coefficients during nonsteady-state transport through a membrane. Recent experiments demonstrated that this assumption is not always valid. Interfacial resistance has been identified in several separation processes, such as gas, vapor permeation, solvent extraction, liquid membrane, drug control release, etc. Role of non-equilibrium interface in the overall mass transfer is addressed in this paper and expanded equations for the time lag are derived. Analytical expressions allow the utilization of transient state information for the evaluation of interfacial resistance. It is demonstrated theoretically that ignorance of the interfacial resistance could decrease the estimated diffusion coefficient by a factor of 3.A concept of interfacial resistance index (IR index) is proposed, which allows the evaluation of interfacial resistance in the overall mass transfer process. For a given system the possible role of interfacial resistance in the overall mass transfer can be evaluated even before the actual interfacial transfer rate is known.
This paper outlines the requirements for metal recovery from wastewater, with particular reference to electroplating. The technical features of three alternative membrane processes arc described. Nanofiltration is shown to separate ionic species on the basis of coulombic interactions or hydrated ion size, which leads to either a 'charge' pattcm or a 'hydration' paaem of rejection. These rejection pattems provide ion selectivity. Ultrafiltration 0. coupled with ion-complexing polymers or ion exchange resin, also provides efficient removal of metal ions, at high flux. The effectiveness of the UF-resin process is considerably increased as the resin size is decreased. Solvent extraction in a Liquid Membrane Contactor (LMC), which is based on microporous hollow fibre modules with aqueous and organic phases circulating through the shell or fibre lumens, achieves high fluxes of metal ions. A limitation of the LMC is the need to avoid phase leakage. The factors goveming the critical displacement pressure and the effective transmembrane pressure are discussed. An LMC with a high packing density of fibres in the shell is preferred. Fmally, the paper discusses critcria for selection of 'user friendly' technologies for the electroplating industry. The membme technologies, particularly in combined form, score highly except in t e m of simplicity. This aspect needs I I further development.
A membrane contactor is a device that achieves gas/liquid or liquid/liquid mass transfer without dispersion of one phase within another. This is accomplished by passing the fluids on opposite sides of a microporous membrane. By careful control of the pressure difference between the fluids, one of the fluids is immobilized in the pores of the membrane so that the fluid/fluid interface is located at the mouth of each pore. This approach offers a number of important advantages over conventional dispersed phase contactors, including absence of emulsions, no flooding at high flow rates, no unloading at low flow rates, no density difference between fluids required, and surprisingly high interfacial area. Indeed, membrane contactors typically offer 30 times more area than what is achievable in gas absorbers and 500 times what is obtainable in liquid/liquid extraction columns, leading to remarkably low HTU values.Although a number of membrane module geometries are possible, hollow fiber modules have received the most attention. In general, tube side mass transfer coefficients can be predicted with reasonable accuracy; on the other hand, shell side coefficients are more difficult to determine, and several research groups are currently addressing this problem.Membrane contactor technology has been demonstrated in a range of liquid/liquid and gas/liquid applications in fermentation, pharmaceuticals, wastewater treatment, chiral separations, semiconductor manufacturing, carbonation of beverages, metal ion extraction, protein extraction, VOC removal from waste gas, and osmotic distillation. This paper provides a general review of hollow fiber membrane contactors, including operating principles, relevant mathematics, and applications.
Kinetics of membrane-based extraction can be controlled by the boundary layers and/or by the membrane transfer resistance, depending on the flow configuration and the nature of the membrane. While the mass transfer coefficients on a tube side of hollow-fiber contactors are well defined, there is a need to establish a suitable correlation to predict the coefficients on a shell side. Using several commercial hollow-fiber modules the extraction of ethanol from aqueous solution into n-octanol has been investigated experimentally. The effect of liquid flow rates, membrane type and packing density of modules on the extraction kinetics has been studied. Experimental results have been correlated by a new dimensionless equation for the shell side mass transfer, valid for low Reynolds numbers and high packing densities.
Relatively stable liquid membranes were easily and reproducibly prepared by impregnating commercial porous polytetrafluoroethylene or polypropylene membranes with solutions of commercial chelating extractants. When such membranes were placed between aqueous solutions of copper(II) sulfate at pH 1–4 and of sulfuric acid at pH 0.5, transfer of copper(II) ion from the less acidic to the more acidic solution took place simultaneously with an equivalent proton transfer in the opposite direction. The copper(II) ion moved selectively with respect to iron(III) ion and against a twenty-fold concentration gradient. The mechanistic and practical implications of these results are discussed.
The kinetic mechanism was elucidated for metal extraction with hydroxyoximes. The reaction of the 1:2 metal–chelating agent complex formation determines the rate of copper extraction with the chelating agents, which are surface-active and less soluble in the aqueous phase. It is found from the results about the diluent’s effect on the rate that this complex is formed at the interface through the reactions between the adsorbed 1:1 complex and the chelating agent dissolved in the aqueous phase, and also between the adsorbed chelating agent and the 1:1 complex in the aqueous phase. The overall rate constant of this interfacial reaction can be related to the pKa value of the chelating agent. The 1:1 complex formation in the stagnant film of the aqueous phase controls the rate of copper extraction with the chelating agent, which is surface-inactive and soluble in the aqueous phase. The catalysis of α-hydroxyoxime in the copper extraction with β-hydroxyoxime is caused by the fast reaction between the 1:1 copper–β-hydroxyoxime complex adsorbed at the interface and the α-hydroxyoxime dissolved in the aqueous phase. The question of increasing the rate of extraction is examined by focusing on the physical properties, the partition coefficient of the chelating agent between the aqueous and the organic phases, and the surface activity of the chelating agent. Modification of the substitutional group in the hydroxyoximes is also examined as a means of increasing the rate.
The versatility of the phenomenon of dispersion-free solvent extraction through immobilized aqueous-organic interface in a microporous hydrophobic membrane is demonstrated here. This technique has been used here for an organic-organic interface to extract aromatics from a hydrocarbon feedstock by a polar organic solvent. The phenomenon has been studied further with micropor-ous hydrophilic and composite hydrophobic-hydrophilic membranes. Operational modes and the influence of the membrane and boundary layer resistances for various solvent-solute-membrane systems have been studied for a CELGAKD (hydrophobic) and a CUPROPHAN (hydrophilic) membrane. Limited performance data for microporous hydrophobic CELGARD hollow fibers (X-20) are also presented.
A mathematical model describing the selective extraction of gold(III) from hydrochloric acid solution into a membrane consisting of Aliquat 336 chloride immobilized in poly(vinyl chloride) (PVC) is developed. The extraction rate is assumed to be governed by both the rate of chemical reactions occurring at the interface and the diffusion of the Aliquat 336 chloride species within the membrane. The fairly good agreement between the model and experimental results confirms its validity and shows that the model can be used successfully for the mathematical description and optimisation of membrane extraction utilised in analytical and process systems as well as in environmental chemistry.
The kinetics of liquid membrane extraction of copper using LIX-860 as a carrier was studied. It was found that the salicylaldoxime molecules are present in the organic (C10–C13 normal paraffins) membrane solution in the form of dimmers and that the distribution coefficient of copper does not depend on temperature within the range of 273–293 K. The kinetic studies of copper transport in the liquid membrane system studied point out that the rate of the first transfer step - copper transfer from the aqueous feed solution to the bulk of the membrane solution - is controlled by the solute diffusion across the first interface. The second step - copper transfer from the bulk of the membrane liquid to the aqueous sulphuric acid solution - is controlled not only by diffusion, but also by the rate of the chemical reaction between the copper-LIX-860 complex and the hydrogen ions present in the stripping solution.
Microporous hollow fibers have been used in the extraction of gold from aqueous solutions into an organic extractant and in the stripping of gold from the organic extractant into an aqueous stripping solution. The extraction process displayed little membrane resistance to mass transfer while the stripping process appeared to be dominated by membrane resistance. As a result, overall mass transfer coefficients for stripping were approximately an order of magnitude smaller than those found for extraction. The results support previous work suggesting that liquid-liquid extractions with microporous membranes will be more rapid when the membrane is wetted by the phase having the higher solubility for the solute being transferred.
Liquid—liquid extractions in microporous hollow fiber modules are unusually fast because of the large surface area per volume in these modules. Extractions of p-nitrophenol into amyl acetate show no membrane resistance, and hence are especially rapid. Extractions of acetic acid into methyl amyl ketone are controlled by the membrane resistance. The results show that extractions in hollow fibers will be fastest when the fibers are wet by the fluid in which the solute is more soluble. They also show when fiber modules are a sound inexpensive alternative to centrifugal extractors.
A new process for separating and concentrating metals is described. It is based on the principle of coupled transport. Metal ions such as copper can be “chemically pumped” across a membrane against large concentration gradients by allowing the counterfiow of a coupled ion such as hydrogen ion. The process is carried out within a microporous merebrane containing within its pores an organic, water-immiscible complexing agent. The complexing agent acts as a shuttle, picking up metal ions on one side of the membrane, carrying them across the membrane as a complex, and preserving electrical neutrality by carrying hydrogen ions in the opposite direction. Because the flows of metal and hydrogen ions are coupled, the metal ion can be “chemically pumped” from a dilute into a concentrated solution. The energy for the process derives from the flow of hydrogen ions in the opposite direction. The process could find application, for example, in the purification of dump leach liquors in the hydrometallurgical processing of low grade oresCoupled transport of cupric ion was demonstrated with a Celgard 2400/LIX 64N membrane. Under favorable conditions, copper was concentrated against a 4000-fold concentration difference, and copper was separated from iron with a separation factor greater than 1000. A pH difference of one to two units is sufficient to drive the copper through the membrane at a high rate and separate it from iron. For a given pH gradient across the membrane, the flow of metal ion initially varies linearly with the metal ion concentration gradient, but at high metal ion gradients the flow reaches a limiting value. This appears to be the result of the limited solubility of the metal complex in the organic phase.Typical transport rates are on the order of 3 μg/cm2-min or 3 lb/ft2-year. A short economic assessment based on this flux indicates that processing with coupled transport membranes should be competitive with the best current technology
Kinetic experiments on the extraction of Cr(VI) with Aliquat 336 performed in hollow fiber modules and in the 1% (v) less than or equal to Aliquat 336 less than or equal to 10% (v) and 10 g/m(3) less than or equal to Cr(VI) less than or equal to 500 g/m(3) range of concentrations have been successfully modeled by means of the integration of the mass conservation equation and associated boundary conditions. Different values of the mass transport coefficient through the organic membrane have been obtained depending on the total carrier concentration.
A rotating diffusion cell was used to study the chemical reaction in which copper is transferred from an aqueous sulfate phase to an organic phase containing a copper-complexing agent (purified anti-2-hydroxy-5-nonylbenzo-phenone oxime) dissolved in n-decane. A mathematical model was developed to describe the contributions of the kinetic and diffusive resistances to the overall resistance to mass transfer. Application of this model to the experimental data enabled an overall rate equation for the reversible copper extraction reaction to be written. The active oxime species in the extraction reaction was found to be the monomer with first-order kinetics. The extraction reaction rate was also found to be dependent on aqueous phase hydrogen ion concentration with negative first-order kinetics. The extraction rate constant was determined as 1.3 × 10 cm/s. Assumption that the reverse rate is dependent on hydrogen ion concentration with first-order kinetics enabled the reverse rate constant to be calculated as 6.8 × 10 cm/mol·s.
The extraction of Cu(II) from an equimolar EDTA ethylenediaminetetraacetic acid (EDTA) solution across microporous hollow fibers to an organic phase containing Aliquat 336 (a quaternary amine) was studied. It was shown that the resistance of interfacial chemical reaction could be neglected. A mass-transfer model was proposed considering aqueous-layer diffusion, membrane diffusion, and organic-layer diffusion on the basis of a good knowledge of extraction chemistry and the transport properties of the relevant geometry. The calculated time profiles of Cu(II) concentrations were in reasonable agreement with the measured ones (average standard deviation, 12%). The mass-transfer mechanism of this membrane extraction process was finally identified and discussed.
This study is concerned with the applications of the immobilized interface-based techniques to reversible chemical complexation-based solvent extraction of toxic heavy metals from industrial wastewaters using microporous hydrophobic hollow fiber (MHF) modules. Toxic heavy metals studied were copper and chromium(VI). Each metal was individually removed in separate once-through experiments from a synthetic wastewater by organic extractants flowing in the shell-side countercurrent to wastewater flowing in the fiber bore. The organic extractant used for copper extraction was 5-20 % v/v LIX 84 diluted in n-heptane, and that for chromium extraction was 30 % v/v TOA (tri-n-octylamine) diluted in xylene. A mathematical model was developed to predict the extent of copper extraction from the aqueous synthetic wastewater by the MHF module. The equilibrium constant for copper was determined to be 1.7 from experimental partitioning data. The experimental data on copper extraction in the MHF module are described well by the model if the forward interfacial chemical reaction rate constant is 9.0 X 10[sup [minus]6] cm/s.
The kinetics of the extraction of Cu(II) into CHCl3, solutions of 2-hydroxy-5-nonylbenzophenone oxime, a high molecular weight hydroxyoxime chelating agent, has been found to be first order in metal ton, second order in extrcatant, and inverse first order in hydrogen ion. The results are consistent with a mechanism in which the rate-determining step Involves chemical reactions in the aqueous phase, as was found in other chelate extraction systems we have studied. Interfacial reactions, invoked by earlier workers for such extractions, are not required by this mechanism.
The presence of complexing agents in waste solutions increases the difficulty of removing heavy metals, such as copper. This fact is of vital importance to the metal finishing industry because of the growth in the use of printed circuit boards for consumer products and telecommunications equipment, and to the growing utilization of plated plastics for shielding electronic enclosures such as office equipment and personal computers. Treatment methods for electroless copper rinse waters depend greatly on the particular copper complexing agent used in the electroless copper process. Treatment methods to be discussed are grouped into three categories, chemical, physical, and electrochemical.
Copper can be selectively separated and concentrated by diffusion across liquid membranes. These membranes are effective either as thin films supported by porous polymer sheets or as liquid microcapsules or liquid surfactant membranes.
Preface 1. Models for diffusion Part I. Fundamentals of Diffusion: 2. Diffusion in dilute solutions 3. Diffusion in concentrated solutions 4. Dispersion Part II. Diffusion Coefficients: 5. Values of diffusion coefficients 6. Diffusion of interacting species 7. Multicomponent diffusion Part III. Mass Transfer: 8. Fundamentals of mass transfer 9. Theories of mass transfer 10. Absorption 11. Absorption in biology and medicine 12. Differential distillation 13. Staged distillation 14. Extraction 15. Absorption Part IV. Diffusion Coupled with other Processes: 16. General questions and heterogeneous chemical reactions 17. Homogeneous chemical reactions 18. Membranes 19. Controlled release and related phenomena 20. Heat transfer 21. Simultaneous heat and mass transfer Problems Subject index Materials index.
A novel extraction technique using an emulsion liquid membrane within a hollow-fiber contactor was developed and utilized to extract copper using LIX 84 extractant. Emulsion liquid membranes are capable of extracting metals from dilute waste streams to levels much below those possible by equilibrium-limited solvent extraction. Utilizing an emulsion liquid membrane within a hollow-fiber contactor retains the advantages of emulsion-liquid-membrane extraction, namely, simultaneous extraction and stripping, while eliminating problems encountered in dispersive contacting methods, such as swelling and leakage of the liquid membrane. Mathematical models for extraction in hollow-fiber contactors were developed. The models satisfactorily predict the outcome of both simple solvent extraction and emulsion-liquid-membrane extraction of copper by LIX 84 in a hollow-fiber contactor over a wide range of conditions. Emulsion-liquid-membrane extraction performs exceptionally well when the extraction is close to equilibrium limit. It is also capable of extracting a solute from very dilute solutions. Stability of the liquid membrane is not crucial when used in hollow-fiber contactors; the surfactant in liquid membrane can be reduced or even eliminated without severely impairing the performance.
The use of liquid ion exchangers in a supported liquid membrane process with two capillary membrane modules seems an attractive technique for the extraction of metal ions from waste water. This paper presents a mass transfer model for the extraction of copper ions with LIX 84 that may easily be extended to describe the extraction of other metal ions. The effect of the hydrogen and copper ion concentrations on the copper flux through the membrane was measured for the diffusion and for a reaction-limited case to determine the rate parameters in the mass transfer model. The regeneration of the liquid ion exchanger (carrier) was found to be slow compared with the formation of the chelate complex. It is shown that the extraction experiments can be simulated by using the proposed mass transfer model.
A new technique for solvent extraction with immobilized interfaces in a hydrophobic microporous membrane is described. No dispersion or coalescence is necessary. Extraction of acetic acid from aqueous solutions of different concentrations into either methyl isobutyl ketone or xylene through a fiat thin Celgard® 2400 microporous polypropylene film has been studied in a flow-type test cell primarily at an aqueous phase pressure 40 psi (2.75 x 105 Pa) greater than an essentially atmospheric organic phase pressure. Studies over a range of 20 to 60 psi (1.378 x 105 to 4.134 x 105 Pa) did not indicate any significant pressure effect for extraction with methyl isobutyl ketone. Extraction rates reported as an overall organic phase based mass transfer coefficient are influenced by the boundary layer resistances on the organic and aqueous sides. Boundary layer resistance free overall transfer coefficients have been used to obtain the intrinsic membrane transfer coefficient. A description of this intrinsic membrane transfer coefficient for acetic acid extraction using the notion of a simple unhindered diffusion of a solute through a solvent-filled tortuous porous medium of uniform pore size yields realistic estimates of the tortuosity factor of the membrane used. The potential of this new technique has been described and compared with conventional extraction techniques if hollow microporous hydrophobic fibers are utilized.
In this work the mass transfer analysis and modeling of the hollow fiber non-dispersive liquid—liquid extraction of Cr(VI) with Aliquat 336 is reported. Experimental results corresponding to different values of the initial concentration of Cr(VI) in the aqueous phase in the range 50 g/m3 ⩽ C0 ⩽ 500 g/m3 showed three different diffusional regimes depending on both the initial concentration of Cr(VI) and the linear velocities of the aqueous phase: (i) kinetic control of the mass transport in the aqueous phase, (ii) kinetic control of the mass transport through the membrane fiber wall and (iii) an intermediate region where the control is shared between the aqueous and the membrane phases. The integration of the mass conservation equation with a nonlinear equilibrium condition at the fiber wall agrees satisfactorily with the results of experiments performed at different initial concentrations of Cr(VI) and different values of the linear velocity of the aqueous phase in the range C0 ⩾ 50 g/m3 and 2.95 × 10−3 m/s ⩽ v ⩽ 1.18 × 10−2 m/s. An optimization of the parameters D, solute diffusivity in the aqueous phase, and Keq, equilibrium constant of the extraction chemical reaction, with all the experimental results, using as criterion the minimum weighted standard deviation, gave as a result the value of the parameter D = 2.3 × 10−9 m2/s and values of Keq dependent upon the initial concentration of Cr(VI) in the feed solution. The mass transfer model and parameters reported in this work are useful for the design and optimization of the nondispersive extraction of Cr(VI) in a hollow fiber module.
Copper, cadmium and lead were extracted through a hollow fiber supported liquid membrane with Lix 84-i as copper extractant and Alamine 304-i as extractant for cadmium and lead. The mass transfer rate, expressed as permeability P, was limited by the diffusion through the aqueous stagnant films in the module for copper extraction. A characteristic permeability of 6.9×10−6 m s−1 was measured at a flow rate of 0.076 m s−1 through the fibers. The measured permeabilities were compared to generally accepted mass transfer correlations. For a feed flowing on the tube side, these correlations predicted a three times higher permeability than was measured, while at the shell side, the permeabilities predicted from these accepted correlations were up to a factor of 8 lower than the measured ones. The extraction rate of cadmium from chloride solutions was limited by membrane diffusion. At 0.2 M Alamine 304-i, a permeability of 4·10−6 m s−1 was measured. Higher extraction rates were found when cadmium was extracted from chloride-containing mixtures of phosphoric and sulfuric acid. The extraction rate of lead was a factor of 20 lower than that of cadmium. This was due to the fact that the extractant had a lower affinity for lead.
This work has been focused to the determination of the membrane mass transport coefficient in the simultaneous non-dispersive extraction and back-extraction of Cr(VI). Following the methodology previously reported by the authors for the kinetic modelling of hollow fiber extraction and back-extraction processes, considering the assumption that the overall mass transport resistance is dominated by the resistance in the organic membrane, when Aliquat 336 is used as carrier, and after the description of the interfacial chemical equilibrium in the extraction process (non-linear model, Keq = 0.35) and in the back-extraction process (linear model, Hr = 3.6), it has been possible to describe successfully the experimental results obtaining the optimum value for the membrane mass transport coefficient, KM = 2.2 × 10−8 m/s, which allows the design and optimization of the recovery of Cr(VI).
A group contribution method for the prediction of the molar volume at the normal boiling point has been developed. The method can be used for organic and inorganic compounds. It cannot be used for elements and diatomic molecules. Group contributions are shown for a wide variety of hydrocarbons, organic halogen compounds, organic oxygen compounds, organic nitrogen compounds, organic sulfur compounds, organic boron compounds, organic silicon compounds, miscellaneous organics, and many inorganic compounds.Contrary to the corresponding states methods for the prediction of molar volumes, knowledge of critical properties, acentric factors, and reference volumes is not needed.
The transfer and separation of Cu(II), Co(II), Ni(II) and Zn(II) ions across a hollow fiber supported liquid membrane containing LIX 864 as the mobile carrier dissolved in kerosene solvent has been investigated. The flux and selectivity for copper has been studied as a function of the feed flow, the carrier concentration in the liquid membrane and the extraction solution acidity. A maximum copper recovery at 30% of LIX (v/v) in the diluent was obtained. The permeation experiments showed that at pH 2 in the extraction solution a highly selective separation of Cu over the other cations can be achieved. Increasing the acidity of the extraction solution copper selectivity decrease and the grade of recuperation sequence is Cu>Co>Ni>Zn. These results suggest that in selected situations, this membrane system can be competitive with the conventional liquid-liquid extraction process, in particular in leaching solutions with low metal concentration.
Extraction of copper with liquid surfactant membranes containing chelating reagent in a stirred tank
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- K Knodo
- F Nakashio
M. Matsumoto, K. Knodo, F. Nakashio, Extraction of copper
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- G M Ritcey
G.M. Ritcey, A.W. Ashbrook, Solvent Extraction, Part I, Elsevier, Amsterdam, 1984.
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- G M Ritcey
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Liquid-liquid extractions with microporous hollow-fiber
- N A Delia
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N.A. Delia, L. Dahuron, E.L. Cussler, Liquid-liquid
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Extraction of metals from wastewater. Modeling of the mass-transfer in a supported liquid-membrane process
- A B De Haan
- P V Bartels
- J De Graauw
A.B. de Haan, P.V. Bartels, J. de Graauw, Extraction of metals
from wastewater. Modeling of the mass-transfer in a supported
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