Mass transfer modeling of membrane carrier system for extraction of Ce(IV) from sulfate media using hollow fiber supported liquid membrane

A theoretical and experimental study on the extraction and stripping of Ce(IV) ions from sulfate media using microporous hydrophobic hollow fiber supported liquid membrane has been performed. The experiments were made in the recycling mode. Tri-n-octylamine (TOA) was used as extractant diluted in kerosene and sodium hydroxide was use as strip solution. The mathematical model focused on the extraction side of a liquid membrane system. The aqueous feed mass transfer coefficient (k_i) and the organic mass transfer coefficient (k_m) which were calculated from the model were 9.47 X 10^-2 and 6.303 cm/s, respectively. Therefore, the rate controlling step is the diffusion of the cerium complex across a liquid membrane. In addition, the mass transfer modeling was performed and the validity of the developed model was evaluated with experimental data and found to tie in well with the theoretical value when the concentration of TOA was higher than 5% (v/v).     

Separation of As(III) and As(V) by hollow fiber supported liquid membrane based on the mass transfer theory

Separation of As(III) and As(V) ions from sulphate media by hollow fiber supported liquid membrane has been examined. Cyanex 923 was diluted in toluene and used as an extractant. Water was used as a stripping solution. The extractability of As(V) was higher than As(III). When the concentration of sulphuric acid in feed solution and Cyanex 923 in liquid membrane increased, more arsenic ions were extracted into liquid membrane and recovered into the stripping solution. The mathematical model was focused on the extraction side of the liquid membrane system. The mass transfer coefficients of the aqueous phase (k _i ) and organic phase (k _m ) are 7.15×10⁻³ and 3.45×10⁻² cm/s for As(III), and 1.07×10⁻² and 1.79×10⁻² cm/s for As(V). Therefore, the rate-controlling step for As(III) and As(V) in liquid membrane process is the mass transfer in the aqueous film between the feed solution and liquid membrane. The calculated mass transfer coefficients agree with the experimental results.     

Separation of Zinc Ions from an Acidic Mine Drainage using a Stirred Transfer Cell–Type Emulsion Liquid Membrane Contactor

Abstract

This is a report on the separation and recovery of zinc ions from an acidic mine drainage using a stirred transfer cell‐type emulsion liquid membrane contactor. Di(2‐ethylhexyl) phosphoric acid was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. A study was made of the effect on the extraction extent and initial extraction rate of the following variables: pH and initial metal concentration of the feed phase, carrier content in the organic solution, a stripping agent concentration in the receiving phase, and stirring speed in the transfer cell. The content of sulfuric acid as a stripping agent did not show in the studied range any significant influence on metal permeation through the SLM, although a minimum hydrogen ion concentration of 100 g/L is suggested in the internal aqueous solution to ensure an acidity gradient between both aqueous phases to promote the permeation of metal ions toward the strip liquor. Results show that using a pH of 4.0 in the feed acid solution, a concentration of 3% w/w_o of phosphoric carrier in the organic phase and a H₂SO₄ content of 100 g/L in the strip liquor, the extent and rate of extraction through the liquid membrane can be highly favored, pointing to the potential of this method for extracting heavy metals from many kinds of dilute aqueous solutions.     

Coupled transport of Pb2+ through tri‐n‐octylamine‐xylene‐polypropylene supported liquid membranes

Transport of Pb²⁺ was carried from acidic solution into alkaline stripping phase through tri‐n‐octylamine‐xylene‐polypropylene supported liquid membrane. The transport of Pb²⁺ through the membrane was studied by varying the concentration of Pb²⁺ and HNO₃ in feed solution, NaOH concentration in strip solution and TOA concentration in membrane phase. The flux data obtained has been used to study the stoichiometry of complex Pb(NO₃)_n+2(HNR₃)_n. The supported liquid membrane (SLM) has been found stable for 10 runs with 24 h between each run. This SLM has been used effectively to extract lead ions along with chromium, copper and zinc ions from aqueous acidic leached solution of paint and industrial effluents. © 2012 Canadian Society for Chemical Engineering     

Separation of radioactive metal ions by hollow fiber-supported liquid membrane and permeability analysis

Extraction and stripping of uranium ions from nitrate media using a hollow fiber liquid membrane contactor was studied. In this study, tri-butyl phosphate (TBP) diluted in kerosene was used as extractant and sodium hydroxide was applied as a stripping solution. Uranium ions were extracted using TBP 5%(v/v) by rejecting thorium ions into raffinate with a maximum percentage of extraction for the uranium being 67%. The mathematical model was focused on the extraction side of the liquid membrane system. The permeability for each concentration of HNO₃ was investigated by mass transfer theory. When the concentration of HNO₃ increased, more uranium ions were extracted; however, when the concentration of uranium and thorium in the feed solution was increased, the percentage of extraction and stripping slightly decreased because the permeability decreases when the concentration of the feed solution increases due to membrane fouling and concentration polarization.     

New liquid membrane technology for simultaneous extraction and stripping of copper(II) from wastewater

In this paper, a new liquid membrane technique, hollow fiber renewal liquid membrane (HFRLM), is presented, which is based on the surface renewal theory, and integrates the advantages of fiber membrane extraction, liquid film permeation and other liquid membrane processes. The results from the system of CuSO₄+D2EHPA in kerosene+HCl show that the HFRLM process is very stable. The liquid membrane is renewed constantly during the process, the direct contact of organic droplets and aqueous phase provides large mass transfer area. These effects can significantly reduce the mass transfer resistance in the lumen side. Then the mixture of feed phase and organic phase flowing through the lumen side gives a higher mass transfer rate than that of stripping phase and organic phase, because the aqueous layer diffusion of feed phase is the rate-controlling step. The overall mass transfer coefficient increases with increasing flow rates and D2EHPA concentration in the organic phase, and with decreasing initial copper concentration in the feed phase. The overall mass transfer coefficient also increases with increasing pH in the feed phase, and reaches a maximum value at pH of 4.44, then decreases. Also, there is a favorable w/o volume ratio of 20:1 to 30:1 for this process. Compared with hollow fiber supported liquid membrane and hollow fiber membrane extraction processes, HFRLM process has a high mass transfer rate. Mathematical model for the HFRLM process based on the surface renewal theory is developed. The calculated results are in good agreement with experimental results under the conditions studied.     

The extraction of lactic acid by emulsion type of liquid membranes using alamine 336 in escaid 100

The extraction of lactic acid from aqueous solutions through an emulsion liquid membrane containing Alamine 336 as carrier was investigated. The influence of mixing speed, diluent type, surfactant concentration, extractant concentration, feed solution pH, stripping concentration, phase ratio, and feed concentration were examined. Liquid membrane consists of a diluent (n‐heptane, toluene, kerosene, Escaid 100, and Escaid 200), a surfactant (Span 80) and an extractant (Alamine 336), and Na₂CO₃ were used as a stripping solution. It is possible to extract 91% of lactic acid from aqueous solutions using Alamine 336 in Escaid 100, as an extractant and a diluent respectively.     

磷酸三丁酯/煤油支撑液膜体系中苯酚的传质分离

研究了苯酚在以多孔聚丙烯平板膜(Celgard2500)为支撑体、磷酸三丁酯(TBP)为膜载体和煤油为膜溶剂的支撑液膜体系中的传质过程;用传统萃取法测定了TBP/煤油体系中苯酚络合物摩尔比为1∶1,同时得到25.0℃萃取平衡常数为96.72;考察了原料相pH值、初始质量浓度、膜二侧转速、载体浓度和反萃取相碱浓度对苯酚传质的影响,确定了该体系分离苯酚的最佳条件:原料相pH<9,苯酚初始质量浓度<1 000 mg/L,膜二侧转速>300 r/m in,载体浓度为0.55 mol/L,反萃取相碱浓度0.10 mol/L;根据双膜理论提出苯酚的传质动力学方程,采用直线斜率法计算了苯酚在TBP/煤油支撑液膜体系中的扩散层厚度和膜内扩散系数,计算结果表明动力学方程计算值能较好地与实验值吻合,平均相对误差在2%以内。     

Supported Liquid Membranes Extraction of W(VI) Ions from HCL Solutions Containing Tartaric Acid

Abstract

A transport study of W(VI) ions across tri-n-octylamine (TOA) xylene-based supported liquid membranes from aqueous solutions containing tartaric acid (TA) has been carried out. TA complexes with W(VI) ions to keep them in solution and enhance flux. The optimum conditions of transport found are 0.132 M TA and 0.001 M HCl in the feed, 3.7 M NaOH in the strip, and 0.66 M TOA in the membrane. Beyond these TA and TOA concentrations, there is a decrease in flux and permeability values which are 4.76 × 10^?5 mol/m²/s and 9.15 × 10^?10 m²/s, respectively. NaOH is a better stripping agent than NH₄OH for these metal ions. Increases in membrane phase viscosity and temperature reduce the values of these transport parameters.     

Extraction and pertraction of phenol through bulk liquid membranes

The extraction and pertraction of phenol through a bulk liquid membrane (BLM) with Cyanex^® 923, Amberlite^® LA‐2 and trioctylamine (TOA) as carriers were studied. Cyanex^® 923 was selected as the best carrier for pertraction. The distribution coefficient of phenol for solvents with carrier and pure n‐alkanes, the individual mass‐transfer coefficient at the extraction interface and the initial flux of phenol through the extraction interface (J_Fo) decreased in the order: Cyanex^® 923 > Amberlite^® LA‐2 > TOA ? pure n‐alkanes. The opposite order was observed for the value of the mass‐transfer coefficient in BLM and the maximum flux of phenol through the stripping interface (J_Rmax). At constant driving forces the maximum fluxes through the extraction and stripping interfaces were similar when amine carriers were used. However, J_Rmax was lower than J_Fo for Cyanex^® 923. Although the kinetics of stripping was the rate‐determining step, the flux of phenol was significantly higher than in pertraction with amine carriers. The adsorption of the carrier at aqueous phase/membrane interfaces was probably responsible for the rapid and slow transfer of phenol through the extraction and stripping interface, respectively. Copyright © 2004 Society of Chemical Industry     

Selective enantioseparation of levocetirizine via a hollow fiber supported liquid membrane and mass transfer prediction

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 (k _f ) and the organic liquid membrane phase (k _m ) 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.     

MASS TRANSFER OF SULFURIC ACID BY TRIOCTYLAMINE THROUGH A SUPPORTED LIQUID MEMBRANE

The extraction of sulfuric acid in a supported-liquid membrane (SLM) process, and the kinetics of extraction and stripping of sulfuric acid in a cell of constant interfacial area by trioctylamine (TOA)/kerosene solvent were investigated. The kinetics of extraction and stripping were determined by examining the effects of the operating variables. The extraction rate is a function of the activity of sulfuric acid and the concentration of TOA; the stripping rate is a function of the concentration of trioctylamine sulfate salts in the organic solution. A generalized transport model, which included the film diffusion of sulfuric acid in the aqueous phase, the membrane diffusion within the SLM, and the interfacial chemical reaction, was built. The permeability of sulfuric acid through the SLM using TOA as a mobile carrier was determined. The rate-determining step of the extraction of sulfuric acid through a SLM was analyzed using the data obtained from the experiments of extraction kinetics and the mass transfer in the aqueous phase. Diffusion within the membrane dominates the process of extraction process of sulfuric acid by TOA through a SLM.     

Response Surface Modelling and Optimization of Mercury Extraction through Emulsion Liquid Membrane

Mercury(II) is a very harmful metal, highly toxic, and carcinogenic in nature. Experiments were carried out using the emulsion liquid membrane (ELM) technique in order to evaluate the maximum extraction of mercury(II) from aqueous solutions of mercuric chloride using 3³ factorial design. The ELM consisted of di-2-ethylhexylphosphoric acid as a carrier, toluene as an organic solvent, span 80 as a surfactant, and sulphuric acid with thiourea solution as stripping phase. The three factors for the factorial design were mercury(II) concentration in the aqueous solution, that is, feed phase concentration, carrier concentration in the membrane phase, and sulphuric acid concentration in the stripping phase. The study has also highlighted the effects of various other parameters, such as pH of the feed phase and thiourea concentration on mercury(II) extraction. The optimization of the factors to obtain maximum extraction were carried out by incorporating main effect plots, interaction plots, analysis of variance (ANOVA), normal probability plots, residual plots, surface plots, and contour plots. A reduced model developed by regression analysis was suggested in which the experimental data were fitted very well. The results showed that it is possible to extract mercury(II) up to 98% from aqueous solutions at the optimum conditions.     

Synergistic extraction and separation of mixture of lanthanum and neodymium by hollow fiber supported liquid membrane

Separation of lanthanum and neodymium by supported liquid membrane has been studied. Synergistic extraction and recovery of lanthanum and neodymium with thenoyltrifluoroacetone (HTTA) in benzene have been found by the addition of Trioctylamine (TOA). Results indicate that percentage of extraction is highly dependent on pH of feed solution, which the maximum value is 2.5. When TOA was added to HTTA, the percentage of extraction and recovery considerably increased due to synergism. Lanthanum can be extracted and recovered more than neodymium because of the adduct formation constant,β ₁ . Theβ ₁ values decreased with an increase in atomic number of lanthanide and showed a difference between lanthanum and neodymium. Percentage of extraction and recovery is enhanced when the HTTA concentration is increased, but its difference is larger when TOA concentration is increased. Finally, multi-column module of supported hollow fiber membrane was used and the percentage and difference of extraction and recovery was found to be more increased due to resident time.     

Selective Transport of Bismuth Ions through Supported Liquid Membrane

A new supported liquid membrane (SLM) system was prepared for the selective transport of bismuth ions from the aqueous feed into the aqueous permeate phase. The support of the SLM was a thin porous polypropylene or polyvinylidene fluoride membrane impregnated with diisooctyldithiophosphinic acid (Cyanex 301) as mobile carrier in 4‐chloroacetophenon as organic solvent. Cyanex 301 acts as a highly selective carrier for the uphill transport of bismuth ions through the SLM. In the presence of HNO₃ as a metal ion acceptor in the strip solution, the transport of bismuth ions into the strip side reached 70 % of the initial feed concentration after 3.5 hours. The selectivity and efficiency of bismuth transport from aqueous solutions containing different mixtures of cations were investigated. In the presence of P₂O₇^2– ions as suitable masking agent in the feed solution, the interfering effects of other cations were completely eliminated. The selective transport of bismuth through SLM is superior to liquid‐liquid extraction or through bulk liquid membranes. This is due to the high efficiency. The SLM reduces the solvent requirements, combines extraction and stripping operations in a single process and allows the use of highly selective extractants. The system may be applied to samples containing very low bismuth concentrations.     

Pseudo-Emulsion Based Hollow Fiber Strip Dispersion Technique (PEHFSD): Optimization,Modelling and Application of PEHFSD for Recovery of U(VI) from Process Effluent

Abstract

Pseudo emulsion based hollow fiber strip dispersion technique (PEHFSD) is the first of its kind ever explored in radioactive environment for the extraction of uranium from acidic process streams. Permeation of U(VI) was investigated as a function of various experimental variables such as hydrodynamic conditions (flow rates of pseudo-emulsion and feed phase), concentration of U(VI) in the feed phase, concentration of tri-n-butylphosphate (TBP), HNO₃ concentration in feed phase, O/A ratio and 0.01 M HNO₃ as stripping agent in pseudo-emulsion phase. The mass transfer coefficient was calculated from the experimental results and a model has been presented for determining mass transfer characteristics. PEHFSD has been demonstrated for separation/recovery of uranium from oxalate supernatant waste generated during plutonium precipitation by oxalic acid. PEHFSD and HFSLM (hollow fiber supported liquid membrane) performance has been compared in order to analyze the efficiency of the technique.     

Recovery of Phenols Using Liquid Surfactant Membranes Prepared with Newly Synthesized Surfactants

Abstract

Extraction and stripping equilibrium of phenol, p-cresol, and p-chlorophenol were studied with an organic solution containing a newly synthesized surfactant and an aqueous alkaline solution as a stripping phase. A cationic surfactant showed the highest extraction ratio of phenol among several surfactants used in this study. The magnitude of phenol extracted from water was in the order phenol < p- chlorophenol < p-cresol. The stripping of phenol extracted in the organic solution was quantitatively accomplished with an alkaline solution of high concentration except for the case of cationic surfactants. Extraction of phenol and its derivatives by liquid surfactant membranes containing a newly synthesized surfactant as an emulsifier was carried out in a stirred cell. The effects of various parameters (such as a surfactant and alkaline concentration, the kind of surfactant, and the alkali composition) on the extraction efficiency of phenol were examined along with demulsification of W/O emulsions. On the basis of the stability of surfactants against alkaline solutions used as a receiving phase, cationic surfactants which did not involve an ester or amide bond in their molecule appeared to be among the best surfactants available for phenol removal in liquid membrane operations. The efficiency of phenol recovery with sodium hydroxide as a stripping agent was much higher than that with sodium carbonate; however, the demulsification efficiency of the emulsions decreased with an increase in the content of sodium hydroxide in the mixed alkaline solutions of sodium hydroxide and sodium carbonate. In the design of an efficient recovery process of phenols by LSMs, the composition of the alkaline solution was one of the key factors. Under optimal conditions, phenolic derivatives could be recovered in a few minutes.

     

Supported Liquid Membrane Extraction Study of (MoO4)2- Ions using Tri-n-octylamine as Carrier

Abstract

The transport of (MoO₄)^2- ions across a tri-n-octylamine (TOA) xylene-based supported liquid membrane has been studied at various HCl concentrations in the feed, TOA concentrations in the membrane, and NaOH concentrations in the strip solution. The distribution coefficient and flux of the Mo(VI) ion species vary with the HCl concentration, indicating that different polymeric species of this metal ion are present in the aqueous solution. A TOA concentration increase of up to 1.308 mol/dm³ enhances flux and permeability of this metal ion, which beyond this concentration is reduced due to an increase in carrier liquid viscosity. An increase in NaOH solution concentration has been found to increase flux and permeability values. The continuous increase in pH of the feed with the transport of metal ions indicates that the (MoO₄)^2- transport does not involve a decrease or increase in concentration as a result of association of lower to higher or decomposition of higher to lower metal ions polymeric species. The optimum conditions of transport of Mo(VI) metal ions across these membranes have been found to be HCl = 0.01, [NaOH] = 1, and [TOA] = 1.308, furnishing flux and permeability values of the order of 2.49 × 10^?4 mol·m^?2·s^?1 and 2.32 × 10^?10 m²·s^?1, respectively.     

KINETICS OF PHENOL EXTRACTION FROM AQUEOUS PHASE BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

The kinetics of the extraction of phenol from the aqueous phase by sulfuric acid salts of trioctylamine (TOA salts) in kerosene and the stripping of phenol from the organic phase by sodium hydroxide solution were studied using a constant interfacial area cell. Measurements of the extraction and stripping rates were made by measuring the time-dependent phenol concentrations in the aqueous phase. It is found that the extraction rate of phenol is strongly dependent on the initial concentration of phenol in the aqueous phase and on the initial concentration of TOA salts in the organic solvent. However, the effect of the total sulfate concentration and the acidic concentration on the extraction rate are not significant. The stripping rate is only a function of the initial concentration of phenol in the TOA salt-organic phase. By analyzing the experimental data, it was recognized that the extraction of phenol occurs at the interface, rather than in the bulk of the solution. The diffusion resistance, rather than the resistance of chemical reaction, is the rate-controlling step for the phenol extraction. Based on the experimental data, simple expressions of the extraction rate and stripping rate of phenol were obtained.     

Extraction of Platinum(IV) with Trioctylamine and its Application to Liquid Membrane Transport

Abstract

The extraction and stripping behavior of platinum(IV) between trioctylamine (TOA) in kerosene and different aqueous media has been investigated. Perchlorate anion was found to be most effective for the stripping of platinum under acidic and neutral conditions. The transport of platinum was performed through a supported liquid membrane (SLM) impregnated with TOA as a mobile carrier. Platinum was almost quantitatively transported from the hydrochloric acid solution to the stripping solutions containing perchlorate anion against its large concentration gradient without accumulation in the liquid membrane layer. The transport behavior of platinum was greatly improved by the addition of 1-octanol in SLM, and the permeation rate was mainly controlled by diffusion in the aqueous boundary layer.