Flat Sheet Supported Liquid Membrane Research Articles

Ionic liquids as a carrier for chloride reduction from brackish water using hollow fiber renewal liquid membrane

High concentration of chloride ions in continental water is a great problem for the exploitation of these natural resources. In industry, the use of this water involves additional conditioning steps. For drinking water and irrigation uses, the Cl− must be reduced by conventional water treatment processes, like ion exchange or reverse osmosis, but for large scale production these techniques could be very expensive due to resin regeneration or energy costs. The possibility of using supported liquid membranes (SLM) with ionic liquids (IL), Aliquat 336, Cyphos IL 101 and Cyphos IL 167, as carriers to exchange Cl− for HCO3− anion has been shown to work. The reversibility of this anion exchange was corroborated by solvent extraction experiments and implemented in flat sheet supported liquid membrane (FSSLM) and hollow fiber renewal liquid membrane technologies (HFRLM). About double transport values have been obtained in HFRLM compared to SLM and 1h is the time enough to reduce the chloride concentration up to 250mg/L using HFRLM at the best experimental condition. The results obtained allow us to be optimistic about the implementation of this technology on a large scale to chloride reduction in drinking water when the source is inadequate for direct use.

Recovery of acetaminophen from aqueous solutions using a supported liquid membrane based on a quaternary ammonium salt as ionophore

AbstractA flat sheet-supported liquid membrane (FSSLM) system, consisting of an ionic liquid, tricapryl-methylammonium chloride (Aliquat 336®) in octan-2-ol, is proposed as a means of recovering acetaminophen (Ac) from aqueous solutions; Ac is an active ingredient widely used in many pharmaceutical preparations. Several parameters which could affect the transport efficiency were examined, i.e., the strippant nature and concentration in the receiving solution, the diluent nature, carrier concentration, initial acetaminophen concentration in the feed solution, and the polymeric support type. A facilitated transport was obtained by impregnating the polymeric support with 10 vol. % of Aliquat 336® in octan-2-ol, 1 M NaOH as a receiving solution, and a feed solution of Ac dissolved in ultrapure water. The study was completed by using the FSSLM thus developed for extracting Ac from some drugs in frequent use in Tunisia (Analgan®, Doliprane®, and Fervex®).

Transportation of bioactive (+) catechin from its aqueous solution using flat sheet supported liquid membrane

Transport of (+) catechin through a flat sheet Supported Liquid Membrane (SLM) has been investigated and reported in this paper. Liquid membrane (LM) was composed of carrier, tributyl phosphate (TBP) dissolved in aliphatic n-decane. Aqueous feed solution containing catechin was maintained at acidic (pH=4) condition using 0.1N HCl whereas ethanol was used as stripping agent. The SLM operation yielded 53% extraction and 49% recovery of the catechin at the optimum operating conditions viz. 100mgL−1 initial feed concentration, 1.2M TBP in the membrane phase, 0.4M ethanol as stripping agent, 200rpm stirring speed and 25°C temperature. The SLM method was found reasonably stable using polyvinylidene difluoride (PVDF) as a support material that allows repeatability of use of same support-LM combination. Further, the above transport method was tested for the recovery of catechin compounds present in hot water extract of green tea leaves which contains mainly (+) catechin (65.6%) and (-) epigallocatechin (EGC) (33.8%). Thirty six percent of catechin compounds initially present in the tea leaves extract (269.3mgL−1) was recovered at the optimum conditions which were slightly different from the optimum conditions achieved for synthesized catechin solution. Initial flux of transport for catechin compounds from tea leaves extract was found to be 19.17×10−9gcm−2s−1.

Membrane-based extraction with strip/organic dispersion methodologies for metals removal and recovery from wastewaters

Abstract The generation of liquid effluents containing organic and inorganic residues from industries presented 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. Several configurations are used: flat-sheet supported liquid membranes, spiral wounds and hollow fiber modules. In order to improve their effectiveness, smart operations have been developed: pseudo-emulsion membrane based strip dispersion (PEMSD), pseudo-emulsion based hollow fiber strip dispersion (PEHFSD), hollow fiber renewal liquid membrane (HFRLM) and double strip dispersion hybrid liquid membrane (SDHL...

Selective separation of cobalt and nickel by flat sheet supported liquid membrane using Alamine 300 as carrier

Cobalt and nickel are among the most important nonferrous metals. The using of flat sheet supported liquid membranes (FSSLMs) to remove metals from wastewaters has been used actively by the scientific and industrial communities. In this study, the selective separation of cobalt from thiocyanate solutions containing cobalt and nickel by FSSLM was examined using tri-n-octylamine (Alamine 300) as carrier. The FSSLM was consisted of extractant, flat sheet support and organic solvent. The various parameters were studied to determine the optimum extraction and striping conditions of cobalt and nickel. These parameters were stirring speeds of phases, NH4SCN concentration, pH, diluent type, extractant concentration, stripping reagent concentration and modifier concentration. Concentration of cobalt and nickel were determined by Shimadzu AA-6701GF spectrophotometer. In the optimum conditions, selective separation of cobalt was achieved with an efficiency of 98.4% within 8h, for equimolar feed mixtures, 400mg/L Co+400mg/L Ni, and the separation factor of Co(II) over Ni(II) was 234.4. In addition, for nonequimolar feed mixtures, 500mg/L Co+1000mg/L Ni, Ni in excess, selective separation of cobalt was 99.9%, and the separation factor of Co was 506 in the same time.

A supported liquid membrane system for efficient extraction of vanillin from aqueous solutions

The paper presents an experimental study on the extraction of vanillin from aqueous solutions through a flat-sheet supported liquid membrane (FSSLM) system. Thereby, the best organic solvent and the operating conditions that would yield optimum performance of the developed SLM system have been identified. Tributyl phosphate (TBP) is used as carrier. Among various solvents, tested for the above purpose, kerosene is found to be the best. The effects of operating conditions, viz. TBP concentration, pH of feed and receiving solutions, initial vanillin concentration, feed dose and stability of the membrane are investigated. Under optimum conditions, an initial flux value around 4 × 10 −6 mol m −2 s −1 has been determined and more than 60% of the initial vanillin concentration can be extracted. The main feature is that the elaborated FSSLM system retained its stability and initial performance during the experiment that lasted for 13 days. After 24 h of extraction, 84.5% and 64.5% of initial vanillin concentration can be removed from vanilla sugar and vanilla liquor real samples, respectively. The present study shows that the developed SLM system can be auspiciously applied to extract vanillin from aqueous solutions.

Extraction of phenol from aqueous solutions by means of supported liquid membrane (MLS) containing tri- n-octyl phosphine oxide (TOPO)

This paper deals with the liquid–liquid extraction and the facilitated transport through a supported liquid membrane (SLM) system of aqueous phenol using tri -n-octyl phosphine oxide (TOPO) dissolved in an appropriate organic solvent. Phenol has been quantitatively extracted from aqueous acidic solutions using TOPO dissolved in kerosene as organic phase. The effect of TOPO concentration dissolved in kerosene on the extraction efficiency reveals that TOPO combined with phenol in the ratio of 1:1. Using a flat-sheet SLM (FSSLM) system, more than 65% of the initial phenol content in the feed phase was extracted and stripped in a NaOH aqueous receiving phase. The important operational variables affecting the facilitated transport of phenol through the FSSLM system studied are concentration of TOPO, membrane viscosity, feed phase pH, initial phenol concentration, polymeric support type and membrane stability. Regardless of its comparatively low extraction efficiency of phenol, the SLM based on TOPO exhibits higher long-term stability as compared to tributyl phosphate (TBP). Elaborated SLM system retained its stability and initial performance during the 5 days long experiment contrary to the TBP-SLM system where a time dependent negative tendency (transport efficiency decline) was observed.

The Extraction of Cr(VI) by a Flat Sheet Supported Liquid Membrane Using Alamine 336 as a Carrier

Chromium compounds have received considerable attention because they have been used extensively in such industrial applications as electro-plating, steelmaking, tanning of leather goods, and as corrosion inhibitors. The use of flat sheet supported liquid membranes (FSSLMs) to remove metals from wastewaters has been actively undertaken by both the scientific and industrial communities. The present work deals with carrier-facilitated membrane transport of Cr(VI) from acidic media across a FSSLM using the organic extractant reagent Alamine 336. The efficiency of the membrane transport was optimized as a function of pH, diluent type, strip phase (NaOH) concentration, feed and strip phase mixing speed, extractant type and concentration, and support type. Various initial feed phase Cr(VI) concentrations were studied under the optimum conditions. At a 2,000 ppm optimum feed phase concentration, the FSSLM showed no significant loss in permeability and retained the same transport ability over 49 h. Under that condition, the extraction of Cr(VI) was found to be > 99% and the mass flux and permeation coefficient were calculated using related equations as 7.35 × 10−6 kg m−2 s and 7.88 × 10−6 m s−1, respectively.

Supported liquid membranes technologies in metals removal from liquid effluents

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. Several configurations are used: flat-sheet supported liquid membranes, spiral wounds and hollow fiber modules. In order to improve their effectiveness, smart operations have been developed: non-dispersive solvent extraction, non-dispersive solvent extraction with strip phase dispersion and hollow fiber renewal liquid membrane. This paper overviewed some of these supported liquid membranes technologies and their applications to the treatment of metal-bearing liquid effluents.

Separation of Carrier Free 90Y from 90Sr by Hollow Fiber Supported Liquid Membrane Containing Bis(2-ethylhexyl) Phosphonic Acid

The present article gives a comparative account of the efficiency of carrier-free 90Y separation from 90Sr by solvent extraction, flat sheet-supported liquid membrane (FSSLM) and hollow fiber-supported liquid membrane (HFSLM) methods using bis(2-ethylhexyl) phosphonic acid (PC88A) as the carrier extractant. The major focus of this work has been to develop the HFSLM method for the separation of Y(III) on a relatively large scale. The feed and receiver phase conditions were optimized by carrying out batch solvent-extraction studies. The extraction of Sr(II) by PC88A was negligible in the acidity range of 0.01–3 M HNO3, whereas the extraction of Y(III) was significantly large at lower acidity (≤0.1 M HNO3) with a separation factor (SF = DY/DSr) of 8.5 × 104. HFSLM studies suggested selective and efficient transport of Y(III) into 3 M HNO3 from a feed solution containing a mixture of Y(III) and Sr(II) at 0.1 M HNO3. On the other hand, transport of Sr(II) was negligible in the receiver phase. The purity of the separated 90Y was ascertained by paper chromatography and by half-life measurement. The radiation stability of the carrier was excellent as studied up to 1000 KGy dose.

Prediction of Ionic Cr (VI) Extraction Efficiency in Flat Sheet Supported Liquid Membrane Using Artificial Neural Networks (ANNs)

Artificial neural networks (ANNs) are computer techniques that attempt to simulate the functionality and decision-making processes of the human brain. In the past few decades, artificial neural networks (ANNs) have been extensively used in a wide range of engineering applications. There are only a few applications in liquid membrane process. The objective of this research was to develop artificial neural networks (ANNs) model to estimate Cr (VI) extraction efficiency in feed phase.Data set (413 experiment records) were obtained from a laboratory scale experimental study. Various combinations of experimental data, namely % (w/w) extractant Alamine 336 concentration in membrane phase, stirring speed in feed and stripping phase, flat sheet support type, stripping phase NaOH concentration, feed phase pH, diluents type, % (w/w) diluents concentration, polymer support type, extractant type, and time are used as inputs into the ANN so as to evaluate the degree of effect of each of these variables on Cr (VI) extraction efficiency in feed phase. The results of the ANN model is compared with multiple linear regression model (MLR). Mean square error (MSE), average absolute relative error (AARE) and coefficient of determination (R2) statistics are used as comparison criteria for the evaluation of the model performances. Based on the comparisons, it was found that the ANN model could be employed successfully in estimating the Cr (VI) extraction efficiency.

Liquid–liquid extraction and transport across supported liquid membrane of phenol using tributyl phosphate

In the present work, the extraction of phenol by liquid–liquid extraction procedure and by supported liquid membrane (SLM) system using tributyl phosphate (TBP) has been explored. Firstly, the liquid–liquid extraction of phenol with mixture of TBP and hexane, 2-octanol, or kerosene was investigated. The addition of TBP improves the extraction efficiency and more than 90% of phenol was extracted after only 3 min of contact with tested mixtures. Secondly, taking into consideration the obtained results, the transport of phenol across a flat-sheet SLM (FSSLM) containing 20% (v/v) TBP in kerosene as liquid membrane phase was studied. Several operational variables such as TBP concentration, source solution pH, initial phenol concentration, stripping reagent (NaOH) concentration and polymeric support type were examined. Under optimum conditions, an initial flux value of 1.4 × 10 −5 mol m −2 s −1 has been determined. Finally, the stability of the SLM system was checked. The system can be considered as stable using polyvinylidene difluoride (PVDF) as a polymeric support since only a 17% decline in the transport efficiency was observed after 3 days of continuous run.

Studies on the transport of chromium(III) through a supported liquid membrane containing D2EHPA as carrier

The facilitated transport of chromium(III) through a flat-sheet supported liquid membrane (FSSLM) containing di(2-ethylhexyl) phosphoric acid (D2EHPA) as ionophore is studied. A buffered Cr(III) solution was used as a source phase, whereas HCl solution was used as a receiving phase. The incidence of several parameters such as feed phase pH, carrier concentration, polymeric support nature and diluent chemical nature on the transport efficiency has been investigated. Overall experiments, a feed pH decrease has been observed due probably to proton permeation. Therefore, pH was manually maintained during the run at the initial value by adding NaOH concentrated solution to the feed phase. After 48 h transport, a trivalent chromium transport efficiency of almost 67% has been obtained through a D2EHPA-2-octanol based SLM when source pH was maintained constant around 4.5. Under the optimum experimental conditions an initial flux value of 4×10-6 mol.m-2.s-2 has been estimated. Transport of hexavalent chromium across the D2EHPA based FSSLM was also examined, and a very slight amount not exceeding 5% was transported.

Facilitated transport of Am(III) through a flat-sheet supported liquid membrane (FSSLM) containing tetra(2-ethyl hexyl) diglycolamide (TEHDGA) as carrier

Facilitated transport of Am(III) in nitric acid medium using tetra(2-ethyl hexyl) diglycolamide (TEHDGA) in n-dodecane as carrier was studied. It was aimed at finding out the physico-chemical model for the transport of Am(III) using TEHDGA/ n-dodecane as carrier under various experimental parameters like feed acidity, carrier concentration, varying strippant, varying membrane pore size, etc. The feed acidity and carrier concentrations were varied from 1 M to 6 M HNO 3 and 0.1 M to 0.3 M TEHDGA/ n-dodecane, respectively. The transport of Am(III) increased with increase in feed acidity and carrier concentration reaching maximum at 3 M HNO 3 and 0.2 M TEHDGA/ n-dodecane, respectively. Several stripping agents were tested and 0.1 M HNO 3 was found to be the most suitable stripping agent for this system. Almost quantitative transport of Am(III) was observed at about 180 min with feed acidity of 3 M HNO 3, 0.1 M HNO 3 as strippant and 0.2 M TEHDGA/ n-dodecane as carrier. The pore size of the membrane support was varied from 0.20 μm to 5 μm and the permeation coefficient increased with increase in pore size up to 0.45 μm (2.43 × 10 −3 cm/s), and then decreased with further increase in pore size. The plot between permeation coefficient vs. (membrane thickness) −1 was linear which showed that the Am(III) transport was membrane diffusion limited. The membrane diffusion coefficient calculated from the graph was found to be 1.27 × 10 −6 cm 2/s and its theoretical value was 1.22 × 10 −6 cm 2/s. The stability of the carrier against leaching out of the membrane support as well as the integrity of membrane support was studied over a period of 30 days and was found to be satisfactory within the studied time period.

Carrier-mediated transport of Cr(III) across Lasalocid A-NPOE supported liquid membrane

A weak amount of Cr(III), not exceeding 5%, was transported through a flat sheet supported liquid membrane (FSSLM) using Lasalocid A as carrier and nitric acid as stripping agent. This inefficient transport was mainly due to a driving force disappearance caused by a nitric acid leakage through the flat sheet membrane and then a feed pH decrease. Three experimental solutions have been proposed to overcome, at least partially, this hindrance. Firstly, Cr(III) was transported across a hollow-fiber supported liquid membrane (HFSLM) working as a column system, i.e., by recirculating the feed solution and the stripping solution separately and successively. A transport rate of 19% has been found when each solution was recirculated for 24 h. Secondly, tributyl phosphate (TBP) was used as modifier of the organic membrane solution to accelerate reaction kinetics to interfaces. The addition of TBP permits the transport of 17% of the initial Cr(III) amount in feed after 79 h of the transport process. Thirdly, the feed pH was kept constant by the addition of concentrated NaOH solution. This addition led to a complete Cr(III) transport and an initial flux of 4.1×10 −7 mol.m −2.s −1 was obtained.

Selective separation and preconcentration studies of chromium(VI) with Alamine 336 supported liquid membrane

Chromium compounds have received considerable attention because these are used extensively in such industrial applications as electroplating, steelmaking, tanning of leather goods, and corrosion inhibition. The use of supported liquid membranes (SLMs) to remove metals from wastewaters has actively been pursued by the scientific and industrial community. In the present work, the selective separation and preconcentration of Cr(VI) ions has been studied by using a commercial amine as the membrane liquid on the porous polypropylene support. Permeation experiments were conducted on a laboratory scale batch reactor made up of perspex, with a memberane fixed amid the two chambers. The flux of Cr(VI) ions was found to be maximum (3.15 × 10−5 mol cm−2 s−1) around pH 1. Above and below this pH the flux decreases. Distribution studies show that an increase in the amine concentration leads to higher distribution coefficients at fixed pH values. At pH around unity, the distribution of Cr(VI) ions into the organic phase was found to be maximum, of the order of 56.3. The Cr(VI) transport through the membrane increases with rise in temperature. In order to check the long-term efficiency of the flat sheet SLM, an experiment was conducted with higher Cr(VI) concentration (5000 ppm) for 24 h, at optimised parameters. It was observed that in 24 h, about 1/5th of the feed Cr(VI) is left over while the rest is transported. However, minute organic droplets were also seen in the feed and strip compartments, after 1 day. This observation suggested the loss of membrane liquid. The feasibility of preconcentration of Cr(VI) by using the proposed SLM parameters, was also studied by using the hollow fibre (HF) system. Highest enrichment factor (E.F) value was obtained for 50 mg L−1 whereby all of the metal was transported to the stripping phase and the resulting Cr concentration was 688 mg L−1 (E.F = 13.8). It was observed that while treating more diluted solutions, the enrichment factor decreases. The values of E.F equal to 8.9 and 11.3 were found for initial Cr concentration of 10 and 30 mg L−1.

Facilitated supported liquid membrane transport of gold (I) and gold (III) using Cyanex ® 921

The commercially available extractant Cyanex ® 921 (phosphine oxide) was studied to be applied in the carrier-facilitated transport of gold (I) (cyanide media) and gold (III) (chloride media), across a flat-sheet supported liquid membrane (FSSLM). Gold (I) is transported from alkaline pH values. The presence of lithium salts in the aqueous media improves the transport. In chloride media, the carrier is able to transport gold (III), decreasing the permeability as the initial HCl concentration is increased. From both aqueous media, a model is presented that describes the transport mechanism, consisting of diffusion through a feed side aqueous layer, a fast interfacial chemical reaction, and diffusion of carrier and metal complexes through the organic membrane. The organic membrane diffusional resistance ( Δ o), aqueous diffusional resistance ( Δ a) were calculated from the proposed model, and their values were 1.1 × 10 4 and 9.1 × 10 8 s/cm ( Δ o, cyanide and chloride media) and 5.3 × 10 2 and 2.6 × 10 2 s/cm ( Δ a, cyanide and chloride media). The values of the bulk diffusion coefficient ( D o,b) and diffusion coefficient ( D o) calculated from the model were D o,b (cyanide) = 4.1 × 10 −6 cm 2/s, D o,b (chloride) = 5.2 × 10 −11 cm 2/s; D o (cyanide) = 1.1 × 10 −6 cm 2/s, D o (chloride) = 1.4 × 10 −11 cm 2/s.

Mathematical modelling and simulation of cotransport phenomena through flat sheet-supported liquid membranes

A mathematical model of cotransport phenomena of metal ions across flat sheet-supported liquid membranes (FSSLM) is developed in the transient. The initial conditions of the FSSLM system, the physical characteristics of the membrane (porosity, tortuosity and thickness), the kinetics of the chemical reaction in the feed–membrane interface and the diffusion in the membrane phase are taken into account by the model. By using the electroneutrality principle, an expression of the concentration of cotransport species with the metal is deduced in terms of the temporal variation of the metal concentration in the feed phase. From the proposed model, the maximum percentage of metal transported is derived. Finally, a simulation is performed for the case of the transport of metal anions in alkaline solution and is checked against experimental data corresponding to the transport of Au(CN) 2 − in alkaline solution by LIX 79. The proposed model reproduces this transport phenomenon with great accuracy.

Chromium(VI) removal through facilitated transport using CYANEX 923 as carrier and reducing stripping with hydrazine sulfate.

The transport of chromium(VI) through a flat-sheet supported liquid membrane (FSSLM) containing CYANEX 923 (mixture of phosphine oxides) as a carrier has been studied. The permeation of the metal is investigated as a function of various experimental variables: hydrodynamic conditions, concentration of chromium(VI) and HCI in the feed phase, CYANEX 923 concentration and diluent in the membrane, and strippant concentration in the receiving phase. By using hydrazine sulfate in the receiving phase, chromium(VI) is immediately reduced to the less toxic chromium(III). The aqueous mass transfer coefficient and the thickness of the aqueous boundary layer were calculated from the experimental results. The selectivity of CYANEX 923-based FSSLM toward different metal ions and the behavior of the system against other carriers is presented.

Simulation of Non-Linear Flow Density in Transition State from the Mathematical Model of the Diffusion of Metal Anions Through a Flat Sheet Supported Liquid Membrane

A mathematical model is developed for the carrier facilitated transport of metal ions through a flat sheet support liquid membrane (FSSLM) in transition state from Fick's second law. From this model, and from Fick's first law, the flow density is derived as a non-linear concentration gradient. Both expressions, concentration and flow density, depend on the thickness of the membrane and on time. Since the rate constant plays an important role in the model, it is considered as the parameter that controls the system and an equation for it is obtained. This equation explains the velocity of the co-transport process. The proposed model takes into account the species co-transported together with the metal ions. An equation for the number of moles of this species is obtained as a function of the metal species. The concentration gradient of this species explains the behaviour of pH in the feed phase during the process. The model is tested against experimental data corresponding to the transport of metal anions in acidic solution and it is shown that the co-transport process is reproduced with high accuracy.