Optimum Transport Conditions Research Articles

Transport behavior of actinides and lanthanides across a supported liquid membrane using an unexplored monoamide, N,N′-bis(2-ethyl hexyl) α-hydroxy acetamide (BEHGA)

Abstract An unexplored novel monoamide N,N′-bis(2-ethyl hexyl) α-hydroxy acetamide (BEHGA) was used as a carrier for transport of Am(III), Eu(III), Pu(IV/VI) and U(VI) from HNO3 medium across a supported liquid membrane (SLM). Various parameters were investigated to obtain the optimum transport conditions. Transport rates followed the trend Pu(IV)>Am(III)≥Eu(III)>U(VI)> Pu(VI). The effects of macro concentrations of U(VI) and Nd(III) on the transport rate of Am(III) were studied. The diffusion coefficient value for the Am(III)-BEHGA system in HNO3 medium was found to be ~1.8×10−6 cm2/s. The standard deviation of the results obtained from transport experiments by this extractant was found to be ±5%. The membrane was found to be highly selective for actinides and lanthanides with respect to different fission products.

Extraction and Transport of Humic Acid using Supported Liquid-Membrane Containing Trioctyl Phosphine Oxide (TOPO) as the Carrier

or liquids of percolation from the discharges (leachates) are charged bacteriologically and especially chemically of mineral substances (mineral ions and heavy metals) and organic (volatile fatty acids, humic substances), which can contaminate soil, surface waters and ground waters. The humic substances, called also refractories, are not easily biodegradable and require concentrating them and/or adsorbing them by implementation of expensive processes. Scientists are looking for alternatives to eliminate or recover these substances. The present study investigates the elimination of humic acid from waste water using supported liquid membrane containing trioctyl phosphine oxide (TOPO) in toluene, as extractant. The supported liquid membrane is composed of a flat sheet of cross-linked polydimethylsiloxane (PDMS). In this study we have: (i) optimized the conditions for humic acid species transfer from feed aqueous phase to stripping phase across PDMS/TOPO/toluene supported liquid membrane; (ii) characterized the membrane by using FTIR technique and by determining the flux J, permeability P and diusion coecient of the complexed species D. Speciation of the humic acid species in the membrane organic carrier (extractant) phase has also been carried out using theoretically derived equations to elucidate the stoichiometry and mechanism of transport of humic acid across the PDMS/TOPO/toluene supported liquid membrane. Optimum conditions of transport for humic acid have been found to be: pH=3, [NaOH]=0.4 M, Eextraction = 94:67%, Ediusion = 32:5%, J = 1:34 10 4 mgcm 2 s 1 , D = 1:16 10 2 cm 2 s 1 and P = 2:64 cms 1 . Kinetic parameters calculated from the experimental data have been determined. Thermodynamic functions of the several species transfer from the feed solution to the stripping one through the supported liquid membrane, such us enthalpy, entropy and Gibbs free energies, were determined. Positive values of H and negative values of G indicate respectively the endothermic and the spontaneous nature of the humic acid extraction in aqueous solution.

Selective transport of Cu(II) ions from a mixture of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) cations through a bulk liquid membrane using benzyl bis(thiosemicarbazone) as carrier

A dichloromethane membrane system incorporated with benzyl bis(thiosemicarbazone) (LH2) as carrier is introduced for the selective transport of Cu(II) ion from an aqueous source solution containing Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) metal cations to a receiving aqueous phase. The optimum transport conditions were established by studding the composition of receiving phase, time of transport, stirring rate, pH of source phase, presence of fatty acid in the membrane as a phase modifier, type and concentration of surfactant, and concentration of mineral acid in the receiving phase, carrier concentration, and temperature. A kinetic model was also used to describe the Cu(II) ion transport behavior, assuming that it obeys the kinetic laws of two consecutive irreversible first-order processes. Under the optimal conditions, 43% of the initial concentration of Cu(II) ion from the aqueous source phase was extracted into the receiving phase through the bulk liquid membrane.

Selective Transport of Palladium through a Hollow Fiber Supported Liquid Membrane and Prediction Model Based on Reaction Flux

This paper describes the application of hollow fiber supported liquid membranes for the simultaneous extraction and recovery of low-concentration palladium from waste aqua regia solutions. A mathematical model to predict the palladium transport was also developed and verified. We found that the optimum conditions for transport of palladium were pH 2 in the feed with 0.005 M thioridazine and 0.05 M oleic acid in liquid membrane, 0.03 M NaNO2 in the stripping solution, and an operating flowrate of 100 mL/min. With thioridazine and oleic acid as the extractant carrier, a synergistic enhanced extraction was observed. By employing a 3-cycle operation in repeated operating cycle mode, the cumulative palladium extraction and recovery was 82% and 78% respectively. Our mathematical model was developed based on reaction flux. The reaction order and the rate constant were determined. It revealed that the first order rate law governed the reaction system for both the extraction and the recovery. The extraction rate constant (k f ) and the stripping rate constant (k s ) were calculated to 0.0140 s−1 and 0.0248 s−1, respectively. The model was set up for a scenario based on a varying flowrate and a repeated operating cycle mode. The results showed good agreement with theoretical data (curve fittings gave R2 > 0.9).

Study on Transportation of Cu(II) by Dispersion Supported Liquid Membrane System

The transportation and separation of Cu(Ⅱ) through a dispersion supported liquid membrane(DSLM) consisting of 2-ethylhexyl Phosphonic Mono-(2-Ethylhexyl) in kerosene, supported on the polyvinylidene fluoride membrane(PVDF), is studied. The effects of pH value in the feed phase, volume ratio of liquid membrane phase and hydrochloric acid, concentrations of HCl in the strip phase and initial concentration of Cu(Ⅱ) in the feed phase are also researched. The results show that copper ion can be transported effectively when pH =5.25 in the feed phase, the volume ratio is160:40, concentrations of HCl in the strip phase is 4.0mol/L. Under the optimum transport conditions, when initial concentration of Cu(Ⅱ) was 2.00×10-4mol/L, the transport rate of Cu(Ⅱ)was up to 94.7% in 130 min.

Calix[4]arene derivative bearing imidazole groups as carrier for the transport of palladium by using bulk liquid membrane

The carrier activity of calix[4]arene containing imidazole groups towards the facilitated transport of palladium(II) through dichloromethane bulk liquid membrane has been studied. The optimum transport conditions were established by the studies on the effect of pH, feed concentration, carrier concentration, receiver phase concentration and transport time. A solution of 1M hydrochloric acid (HCl) served as receiving phase for maximum transport of the metal ion. Maximum transport efficiency was observed for Pd(II) ion when it was present in the concentration of 10−3M and the transport efficiency after 24h was found as 95%.

Study on supported combined liquid membrane containing HEH(EH)P and HNO3 for trivalent gadolinium transfer

A novel kind of supported combined liquid membrane (SCLM) has been studied for the Gd(III) transfer. SCLM contained polyvinylidene fluoride membrane (PVDF) as the liquid membrane support and renewal solution including HNO(3) solution as the stripping solution and 2-ethyl hexyl phosphonic acid-mono-2-ethyl hexyl ester (HEH(EH)P) as the carrier dissolved in kerosene. The mixed solution of carrier and kerosene was membrane solution. The optimum transport conditions of Gd(III) were that concentration of HNO(3) solution was 4.00 mol/L, concentration of carrier was 0.16 mol/L, and volume ratio of membrane solution to stripping solution was 30:30 of the renewal phase, and pH value was 4.80 of the feed phase. Under the optimum condition studied, when initial concentration of Gd(III) was 1.00 x 10(-4) mol/L, the transfer rate of Gd(III) was 96.8% during 130 min. (C) 2011 Liang Pei. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Stripping dispersion hollow fiber liquid membrane containing PC-88A as carrier and HCl for transport behavior of trivalent dysprosium

The transport of Dy 3+ through stripping dispersion hollow fiber liquid membrane system (SDHFLM) containing dispersion phase with HCl solution as stripping solution and 2-ethyl hexyl phosphoric acid-mono-2-ethyl hexyl ester (PC-88A) dissolved in kerosene as membrane solution, has been studied. Many factors of the interface chemical reaction and composition of the liquid membrane including pH value, initial concentration of Dy 3+, different ionic strength of feed phase, volume ratio of membrane solution to stripping solution (O/W), HCl concentration, carrier concentration, different stripping agents of dispersion phase, hydrodynamic characteristic (flow rates, stability) and hollow fiber structure parameters (inner diameter of fibers, membrane thickness, porosity, etc.) on Dy 3+ transport with SDHFLM were investigated. The advantages of SDHFLM compared to the traditional HFLM was investigated too. Experimental results indicated that the optimum transport conditions of Dy 3+ were that HCl concentration was 4.00 mol/L, PC-88A concentration was 0.150 mol/L, O/W was 0.5 in the dispersion phase, and pH value was 5.00 in the feed phase. Ionic strength had no obvious effect on transport of Dy 3+. When initial Dy 3+ concentration was 1.50 × 10 −4 mol/L, the transport efficiency of Dy 3+ was up to 95.4% in 170 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The results were in good agreement with the literature data.

A Novel Application of Supported Liquid Membrane Based on Hydrophobic Ionic Liquids to the Selective Transport of Phenol and p-Nitrophenol

The transport of phenol (Ph-OH) andp-nitrophenol (p-NP) through a supported liquid membrane system based on hydrophobic ionic liquids ([BEIM][PF6]) (SILMs) consisting of polyvinylidene fluoride membrane (PVDF) as the liquid membrane support and sodium hydroxide solution as the strippping phase, has been studied. The effects of pH, ionic strength, initial concentration of phenol (orp-NP) in feed phase, concentration of sodium hydroxide in the stripping phase have also been investigated, respectively. The optimum transport conditions of phenol in the SILMs were that pH 3.5, ionic strength 0.2 mol/L, initial concentration of phenol 1.31×10-3mol/L in feed phase, concentration of sodium hydroxide in stripping phase was 0.2 mol/L. The permeability value of phenol under above conditions was 2.0×10-5m/s during the transport time of 120 min. The optimum transport conditions ofp-NP in the SILMs were that pH 5.5, ionic strength 0.2 mol/L, initial concentration ofp-NP 4.90×10-4mol/L in feed phase, concentration of sodium hydroxide in stripping phase was 0.15 mol/L.The permeability value under above conditions was 8.6×10-6m/s during the transport time of 120 min. The kinetic equations that can describe transport of phenol andp-NP through the SILMs were also obtained.

Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M2Q3 (M = Sb, Bi, Q = Se, Te)

AbstractThermodynamic modelling of the ternary systems M/Q/I (M = Sb, Bi, Q = Se, Te) indicated solid‐gas equilibria suitable for chemical vapour transport of bismuth and antimony chalcogenides. The predictions of the modelling were confirmed by transport experiments on a transport balance. The optimum transport conditions using iodine as transport agent were determined for all systems to: ϑsource = 500 °C and ϑsink = 450 °C. For ΔT > 50 K the sequential transport of chalcogenide iodides MQI followed by M2Q3 occurs. Thermodynamic standard data of the gas species SbI(g) were concluded from equilibrium calculations: ΔH0f,298(SbI(g)) = 106 ± 3 kJ·mol–1; S0298(SbI(g)) = 255 ± 3 J·mol–1·K–1; Cp(SbI(g)) = 37 ± 1 J·mol–1·K–1

Facilitated transport of cationic dyes through a supported liquid membrane with D2EHPA as carrier

The transport of cationic dyes methyl violet and rhodamine B from aqueous synthetic dye solution through flat type supported liquid membranes (SLM) using di (2-ethylhexyl) phosphoric acid (D2EHPA) as carrier was studied and the parameters affecting the dyes transport were determined. The extraction was carried out from the aqueous feed phase with pH 4 ± 0.2 to a more acidic strip phase of acetic acid (AcOH) with pH 2.5. The proton gradient between the feed and the strip phase was the main driving force of the mass transfer in this system. The influence of various parameters such as pH of the feed phase, strip phase concentration, carrier concentration, stirring speed and the concentration of dyes on the extraction efficiency was studied. Kinetics of transport was also studied. The optimum conditions of transport are feed phase pH 4 ± 0.2, acetic acid as stripping phase with pH 2.5, stirring speed at 600 rpm. The maximum recovery under optimum conditions was observed as 94.2% for methyl violet and 90.0% for rhodamine B.

Analysis of Extraction of Cu(II) by Strip Dispersion Hybrid Liquid Membrane (SDHLM) using PMBP as Carrier

A liquid membrane system, denoted a strip dispersion hybrid liquid membrane (SDHLM) containing 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazolone –5 as carrier in xylene, was reported for the transport and separation of Cu(II) from Zn (II) ions. The effects of various factors on the transport of copper(II) ions through SDHLM were systematically investigated by orthogonal tests. The optimum transport conditions of copper ions were summarized. In the overall mass transfer process the mass transfer resistance due to the aqueous boundary layer diffusion and diffusion in the microporous membrane is dominant. The accumulation of the Cu(II)‐carrier coordination compound in the membrane shows that the transfer in SDHLM possesses the characteristic of nonequlibrium mass transfer in this study. The rheologic experiments verified that the organic phase in the SDHLM system was the non‐Newtonian fluid and the organic phase after transport of 6 hr was a system of thixotropy in our experimental conditions. The lag ring experiments proved that the thixotropy of the organic phase in the SDHLM system was relevant to the composition of the membrane. In the experimental comparison of two types of liquid membrane, SDHLM has superiority over SLM in respect of transport flux, permeability coefficient, recovery percentage or concentration of solute in the stripping solution, efficiency of uphill transport, loss of membrane solution, and the separation efficiency of the membrane.

Quantitative Recovery of Listeria monocytogenes and Select Salmonella Serotypes from Environmental Sample Media

Environmental sampling has become increasingly important in the food industry for monitoring the presence of specific pathogens such as Listeria monocytogenes and Salmonella enterica. Several microbiological media are available for storage and transport of environmental samples from the processing plant to the test laboratory. In this study, we quantified the survival of L. monocytogenes, S. Typhimurium, S. Enteritidis, and S. Typhi in environmental sampling media over several time and temperature combinations to determine optimum conditions for transport and storage. A cocktail of L. monocytogenes strains and Salmonella serotypes was separately added to tubes of Dey-Engley (D/E) Neutralizing Broth, Copan SRK solution, and Neutralizing Buffer and incubated at either -4, 4, 10, or 15 degree C. Counts were made of the bacterial load after 0, 12, 24, and 48 h. Neutralizing Buffer and Copan SRK solution were best at maintaining bacterial concentrations at all temperatures. D/E Neutralizing Broth, at 10 and 15 degrees C, allowed significant bacterial growth. This study helped validate the use of these 3 media for environmental sample transport and storage at cold holding temperatures and demonstrated that, at elevated temperatures (>4 degrees C), it is preferable to use Neutralizing Buffer or Copan SRK solution for quantifying microbial recovery.

Coupled transport of chromium(III) ions across triethanolamine/cyclohexanone based supported liquid membranes for tannery waste treatment

Coupled transport of Cr(III) ions across TEA–cyclohexanone has been studied with respect to triethanolamine (TEA) concentration in the microporous polypropylene film, sulphate ions in the feed and H 2SO 4 concentrations in the stripping phase, respectively. Optimum conditions of transport are TEA concentration (5.26 mol/dm 3) in the liquid membrane, 1.5 mol/dm 3 concentrations of both sulphate ions in the feed and 1.5 mol/dm 3 H 2SO 4 concentrations in the stripping phase. Ten times decrease in concentration level of Cr(III) ions has been observed practically in the feed solution. The flux has been found to increase with Cr(III) concentration increase in the feed. With sulphate ions increase in the feed, the permeability and distribution coefficient of Cr(III) ions has been found to increase; while, diffusion coefficient and mobility of TEA–Cr(III) complex have been found to decrease. The study indicates the practical aspect of direct transport of Cr(III) ions, without its reduction to Cr(VI). Supported liquid membranes (SLM) technique has been applied to remove Cr(III) ions from tannery effluents, where chromium is present in effluents in the third oxidation state.

Litopenaeus vannamei (Boone) post-larval survival related to age, temperature, pH and ammonium concentration

Transport of post-larvae shrimp used in aquaculture is an important element of successful cultivation because of the potential for stress during stocking procedures. To find optimum transport conditions, several bioassays were performed in the laboratory to evaluate survival of whiteleg shrimp Litopenaeus vannamei 5–30-day-old postlarvae under conditions similar to those encountered during transport from the hatchery to nursery and shrimp ponds. Postlarvae were exposed for 4 h to different temperatures and pH levels ammonia concentrations. Survival was significantly reduced after a 4 h exposure to pH 9 and was inversely related to temperature with or without 7 mg L−1 of ammonia. The 15- and 20-day-old postlarvae had higher survival rates than other ages. The lowest survival occurred in alkali conditions (pH 9), with 7 mg L−1ammonia at 30 and 32°C. To assure optimal survival of postlarvae during transfer from the hatchery to the nursery and shrimp ponds, we recommend temperatures below 28°C, pH no higher than 8, no ammonia and post-larval age at least 15 days.

Extraction of Pd(II) ions using tri-n-octylamine xylene base supported liquid membranes

Membranes, based on tri-n-octylamine (TOA) xylene liquid, supported in hydrophobic microporous films have been used to study the transport of Pd(II) ions, after extraction into the membrane. Various parameters, such as the effect of hydrochloric acid concentration in the feed solution, TOA concentration in the membrane phase, effect of stripping agent like nitric acid concentration, and temperature on the flux of Pd(II) ions across the liquid membranes have been investigated. The optimum conditions of transport for these metal ions determined are, TOA concentration, 1.25 mol·dm−3, HCl concentration in the feed solution, 5 mol·dm−3, and concentration of nitric acid used as a stripping, agent 5 mol·dm−3. The maximum values of the flux and permeability determined under the optimum condition are 23·10−6 mol·m−2·s−1 and 2.40·103 m2·s−1 at 25°C. The results obtained have been used to elucidate the mechanism of palladium transport.

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 stripping study of strontium ions across D2EHPA-TBP-kerosene oil based supported liquid membranes

A Sr ion transport study across D2EHPA-TBP kerosene oil based liquid membranes supported on microporous polypropylene film has been performed. The parameters studied were the effect of di(2-ethylhexyl)phosphoric acid (D2EHPA) and TBP concentration variation in the membrane liquid, HNO3 concentration variation in the stripping phase and citric acid concentration variation in the feed solution. The optimum conditions of transport are 0.3 mol/dm3 D2EHPA, 0.1 mol/dm3 TBP, 0.01 mol/dm3 citric acid in feed and 2 mol/dm3 HNO3 in the stripping phase. The mechanism of transport observed is counter-ion coupled transport. The coupling ions are protons. The maximum flux for Sr ion transport observed is 5.33·10−5 mol·m−2·s−1 and maximum permeability under optimum conditions observed is 8.08·10−11 m−2·s−1.

Transport of99mTc across TBP-kerosene oil supported liquid membranes

Transport of99mTc across tri-n-butylphosphate (TBP) kerosene oil supported liquid membranes (SLM) has been studied under various conditions. Presence of dichromate ions helps avoid activity scavenging effects. Concentration increase of TBP, the complexing carrier used in the present study has a positive effect on flux (J) and permeability (P) of these ions, as up to 2.87M there is an increase in J and P values. HCl concentration in the feed solution increases J and P with their maximum values at 2.5–3.0M HCl in the feed. Above this concentration there is a decrease in flux and permeability of99mTc(VII) ions. The given ions are stripped with LiCl or NaCl solutions but more with NaOH. The optimum conditions of transport of the given ions are 2.5M HCl concentration in the feed, 2.87M TBP concentration in the membrane and 1M NaOH concentration in the strip solution. Equations have been developed to indicate the relation between flux, J, viscosity, ν of TBP in organic membrane phase, temperature, T, [H+], in the aqueous feed solutions and Tc ion concentration in the feed solution. Based on P, the values determined from liquid membrane experiments, the quantitative flux values of Tc(VII) ions were also determined as a function of TBP concentration in the membranes, and HCl and Tc concentration in the feed solution using the given equations. This experimental technique provides quantitative results from trace level activity transfer experiments.

Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm−3 (TOA); HF concentration in the feed solution, 0.01 mol·dm−3 and concentration of NaOH used as stripping agent 2.5 mol·dm−3. The maximum flux and permeability determined under optimum conditions are 3.06·10−5 mol·m−2·s−1 and 8.44·10−11 mol· ·m2·s−1 at 25±2°C and 4.21·10−5 mol·m−2·s−1 and 11.55·10−11 mol·m2·s−1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10−11 mol·m2·s−1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.