Performance of hollow fiber supported liquid membrane on the extraction of mercury(II) ions

The extraction and recovery or stripping of mercury ions from chloride media using microporous hydrophobic hollow fiber supported liquid membranes (HFSLM) has been studied. Tri-n-octylamine (TOA) dissolved in kerosene was used as an extractant. Sodium hydroxide was used as a stripping solution. The transport system was studied as a function of several variables: the concentration of hydrochloric acid in the feed solution, the concentration of TOA in the liquid membrane, the concentration of sodium hydroxide in the stripping solution, the concentration of mercury ions in the feed solution and the flow rates of both feed and stripping solutions. The results indicated that the maximum percentages of the extraction and recovery of mercury ions of 100% and 97% were achieved at the concentration of hydrochloric acid in the feed solution of 0.1 mol/l, the concentration of TOA at 3% v/v, the concentration of sodium hydroxide at 0.5 mol/l and the flow rates of the feed and stripping solutions of 100 ml/min. However, the concentration of mercury ions from 1–100 ppm in the feed solution had no effect on the percentages of extraction and recovery of mercury ions. Thus, these results have identified that the hollow fiber supported liquid membrane process has high efficiency on both the extraction and recovery of mercury (II) ions. Moreover, the mass transfer coefficients of the aqueous phase (k _i ) and membrane or organic phase (k _m ) were calculated. The mass transfer coefficients of the aqueous phase and organic phase are 0.42 and 1.67 cm/s, respectively. The mass transfer coefficient of the organic phase is higher than that of the aqueous phase. Therefore, the mass transfer controlling step is the diffusion of the mercury ions through the film layer between the feed solution and the liquid membrane.     

Mass transfer of cadmium ions in a hollow-fiber module by pertraction

The facilitated transport of Cd(Il) ions through a hollow-fiber-supported liquid membrane with bis-2-ethylhexyl phosphoric acid as carrier was studied. The mass transfer rate, expressed as permeability P, was measured as a function of mean aqueous solution velocity and carrier concentration. Characteristic ion permeabilities of 10-26 × 10⁻⁷ m/s were measured at feed velocities between 1 × 10⁻²−19 × 10⁻² m/s at stripping velocities between 0.22 × 10⁻²−7x 10⁻² m/s with constant feed flow. The measured permeabilities were compared to generally accepted mass transfer correlations. The predicted permeabilities adequately fit the experimental data, indicating that the rate limiting step in the transport of the ion was the diffusion through both aqueous films, feed and stripping, whereas the organic resistance of the membrane was negligible. Furthermore, the proposed model allowed the prediction of the permeability of cadmium for different experimental conditions, which is useful to perform experiments to reduce metal levels in water or other effluents.     

Facilitated Transport of Gold through a Membrane via Complexation to Thiourea-Based Reagents

Abstract

The facilitated transport of Au(III) from hydrochloric acid solutions through double solid supported liquid membranes (SSLMs) is reported. The organic phase consisted of a chloroform solution of thiourea-based extraction reagents, dodecyl-thiourea (DTH) or nonylthiourea (NTH), physically absorbed onto microporous polypropylene films, Celgard 2500 or Celgard 2400 (Celanese Plastic Inc.). A cell composed of three compartments, including a reservoir of organic solution, with double SSLM was used in this study. Aqueous solutions of thiourea, KSCN, or Na₂S₂O₃ were used for removing Au(III) from the membrane phase. The permeability coefficient, P, of the SSLM was determined from the slope of Iog[Au]/[Au]_o or log A/A_o vs time plot. The influences of the stirring rate in aqueous feed and organic solutions, of the stripping reagents and their concentration, of the carrier concentration, and of the concentration of HCl in the aqueous feed on the permeability coefficient were determined. A model describing the transport mechanism consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion through the membranes is reported. The study also demonstrates the suitability of the liquid membrane technique to use reagents with low solubility in organic solutions for the permeation of Au³⁺ without problem of solid-phase formation.

     

Facilitated Transport of Cd(II) Through a Supported Liquid Membrane with Aliquat 336 as a Carrier

Selective removal of cadmium from wastewaters is very important, because cadmium is toxic for the environment and for human health. This work is a comprehensive study on the selective removal of Cd(II) from aqueous solutions by using a co-current flow flat sheet supported liquid membrane system. 4.4 × 10^?4 M Cd(II) concentration was used as a feed solution in the experiments. Toluene containing Aliquat 336 was used as the membrane liquid in the membrane system. Parameters such as the properties of feed and stripping solutions, carrier concentration, and flow rate, which have roles in transport of Cd(II) ions, were optimized. The efficiency of the system is expressed in terms of permeability and flux values, and transport efficiency. The optimum process conditions for the Cd(II) transport are experimentally found as follows: The feed solution as 2 M HCl, the carrier concentration as 0.1 M Aliquat 336, the stripping solution as 0.06 M EDTA, and the flow rates for the feed and stripping solutions as 50 mL/min and 80 mL/min, respectively. Under these conditions, the Cd(II) transport efficiency is found to be 82%.     

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.     

Transport of cationic dye by supported liquid membrane using D2EHPA as the carrier

The transport of cationic dye from an aqueous feed solution through a flat‐type supported liquid membrane containing di‐(2‐ethylhexyl)phosphoric acid as a carrier was studied. The influence of pH on the source phase, the effect of the concentration of the receiving phase, the stirring speed, the effect of the initial dye concentration, the feed‐to‐strip ratio and the influence of the support characteristics were studied. A polytetrafluoroethylene membrane with a 1.0‐μm pore size was found to have more permeability than that with a pore size of 0.5 μm. The results indicated that the aqueous feed solution at an alkaline pH has high permeability. The initial feed phase dye can be completely extracted and stripped with a stripping solution within 7 h.     

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。     

La(III) Transport in Dispersion Supported Liquid Membrane Including PC-88A as the Carrier and HCl Solution as the Stripping Solution

The transport of La(III) through a dispersion supported liquid membrane with polyvinylidene fluoride membrane as the liquid membrane support and dispersion solution including HCl solution as the stripping solution and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in kerosene as the membrane solution, was studied. As a result, the optimum transport conditions of La(III) were obtained as that concentration of HCl solution was 4.0 mol/L, concentration of PC-88A 0.16 mol/L, and volume ratio of membrane to stripping solution 30:30 in the dispersion phase, and pH value 4.0 in the feed phase. Ionic strength had no obvious effect on the transport of La(III). Under the optimum conditions, when initial concentration of La(III) was 0.8′10-4 mol/L, the transport rate was up to 96.3% during the transport time of 125 min. The kinetic equation was developed based on the law of mass diffusion and theory of interface chemistry. The diffusion coefficient of La(III) in the membrane and the thickness of diffusion layer between feed and membrane phases were obtained as 3.20′10-7 m2/s and 3.22′10-5 m, respectively. The calculated results were in good agreement with experimental results.     

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.     

组合液膜分离镉锌的动力学分析

采用膜相和反萃相分别为三正辛胺的煤油溶液和醋酸胺的水溶液的组合液膜体系,研究了氯化物料液中镉、锌离子的分离.结果发现,传质过程主要由料液相侧水扩散层和膜相的扩散过程控制;迁移20 h后,镉离子迁移率可达98.3%,锌离子迁移率只有2%,分离系数为49.2.组合液膜能很好地分离镉、锌.流失到料液相和反萃相的载体浓度测试表明,组合液膜中,双固体膜能阻止膜相中载体的流失,提高膜的稳定性,延长膜寿命.改变三正辛胺浓度,对镉离子传输的动力学过程进行了分析,建立了镉离子传输的动力学方程.     

Transport of mercury(II) ion through a supported liquid membrane containing a triisobutylphosphine sulfide (Cyanex 471X) as a mobile carrier

Carrier‐facilitated transport of mercury(II) against its concentration gradient from aqueous 0.1 mol dm^?3 hydrochloric acid solution across a flat‐sheet supported liquid membrane (SLM) containing triisobutylphosphine sulfide (Cyanex 471X) as the mobile carrier in kerosene as diluent has been investigated. Dilute sodium thiocyanate solution (0.11 mol dm^?3) was the most efficient stripping agent among several aqueous reagents tested. Various parameters such as stirring rate, concentration of HCl in the feed solution, concentration of NaSCN in the strippant, concentration of Cyanex 471X in the membrane, and contact time were investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is about 100% after 6 h. The carrier, Cyanex 471X, selectively and efficiently transported Hg(II) ions in the presence of other associated metal ions. The method has been demonstrated to recover selectively mercury from waste samples and mercurochrome solution. © 2002 Society of Chemical Industry     

两相更新支撑液膜中金属二价镍的迁移行为研究(英文)

A novel disphase supplying supported liquid membrane(DSSLM),containing supplying feed phase and supplying stripping phase for transport behavior of Ni(II),have been studied.The supplying supported feed phase included feed solution and di(2-ethyhexyl) phosphoric acid(HDEHP) as the carrier in kerosene,and supplying stripping phase included HDEHP as the carrier in kerosene and HCl as the stripping agent.The effects of volume ratio of membrane solution to feed solution(O/F),pH,initial concentration of Ni(II) and ionic strength in the feed solution,volume ratio of membrane solution to stripping solution(O/S),concentration of H2SO4 solution,HDEHP concentration in the supplying stripping phase on transport of Ni(II),the advantages of DSSLM compared to the traditional supported liquid membrane(SLM),the system stability,the reuse of membrane solution and the reten-tion of membrane phase were studied.Experimental results indicated that the optimum transport of Ni(II) was ob-tained when H2SO4 concentration was 2.00 mol·L-1,HDEHP concentration was 0.120 mol·L-1,and O/S was 4:1 in the supplying stripping phase,O/F was 1︰10 and pH was 5.20 in the supplying feed phase.The ionic strength in supplying feed phase had no obvious effect on transport of Ni(II).When initial Ni(II) concentration was 2.00×10?4 mol/L,the transport percentage of Ni(II) was up to 93.1 % in 250 min.The kinetic equation was deduced in terms of the law of mass diffusion and the interface chemistry.     

静电式准液膜分离技术

静电式准液膜分离技术是由本实验室最近发展起来的一种新型化工分离技术,它是在溶剂萃取、液膜和静电技术的交叉点上产生的边缘技术.该技术能用于分离、纯化和浓缩水溶液中的特定溶质,适用于水法冶金过程中(包括核燃料循环)从水溶液中提取有用金属,并适用于废水处理等过程.本文讨论了这一新型分离技术的基本原理,并以D_2EHPA萃取Co~(2+)为例,研究了电场强度、萃取剂浓度以及料液与反萃液的流比等对金属提取率的影响.实验表明,Co~(2+)的一次提取率可达99%以上,与此同时,浓缩液中的Co~(2+)可以一次浓缩至40—50g/L.     

Simulation of ammonia removal from industrial wastewater streams by means of a hollow-fiber membrane contactor

The performance of a hollow-fiber membrane contactor in removing ammonia from aqueous solution was simulated. An unsteady state 2D mathematical model was developed to study the ammonia stripping in the hollow-fiber membrane contactor. Two sets of equations were considered for the membrane contactor and the feed tank. CFD technique was applied to solve the model equations in which concentration distribution was determined using continuity equation. Velocity field is also determined using Navier–Stokes equations for the contactor. The model was implemented in linked MATLAB–COMSOL Multiphysics. COMSOL software was applied to solve the model equations for the contactor while MATLAB software was employed to consider changes in the concentration of the feed tank. Predictions of the model were then validated against experimental data which were found to be in good agreement. The assumption of Knudsen diffusion for the transport of ammonia molecules through the membrane pores increased the accuracy of the model. The effect of different parameters including feed velocity, feed concentration and pH on the removal of ammonia was investigated. The results of simulation revealed that the developed model can be used to evaluate the effective parameters which involve in the ammonia removal by means of membrane contactors.     

Simultaneous Transport and Separation of Cu(II) and Zn(II) in Cu-Zn-Co Sulfate Solution by Double Strip Dispersion Hybrid Liquid Membrane (SDHLM)

A double strip dispersion hybrid liquid membrane (SDHLM) was successfully used in the simultaneous extraction and separation of Cu(II), Zn(II), and Co(II) from Cu-Zn-Co dilute feed phase. In the double SDHLM system, Acorga M5640-loaded membrane was placed between the 1st and the 2nd compartment, whereas the mono(2-ethylhexyl) 2-ethylhexyl phosphonate [HEH(EHP)]-loaded membrane was placed between the 1st and the 3rd compartment of the transport cell. The feed solution was filled in the central feed compartment(1st compartment) of the transport cell. The effect of the different experimental variables on separation was examined. The optimum separation conditions were summarized.

An analysis of mass transfer resistances in the double SDHLM system shows that the mass transfer resistance for the diffusion of Zn(II) ions in the microporous membrane phase is dominant and the mass transfer resistances for the diffusion of copper (II) ions in the aqueous boundary layer and in the microporous membrane phase are dominant in comparison with the overall mass transfer resistance. The experiments verify that the double strip dispersion hybrid liquid membrane (SDHLM) possesses the nonequlibrium mass transfer characteristic.     

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.     

Separation of mercury and arsenic from produced water via hollow fiber contactor: Kinetic and mass transfer analysis

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.     

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.     

FACILITATED TRANSPORT OF HNO3 THROUGH A SUPPORTED LIQUID MEMBRANE CONTAINING A TERTIARY AMINE AS CARRIER

ABSTRACT

The facilitated transport of HN0₃ through a supported liquid membrane consisting of a porous polypropylene film containing a solution of trllaurylamine 1n diethyl benzene as carrier was studied as a function of the stirring speed of the aqueous solutions and the membrane composition. A physico-chemical model which takes Into account diffusion through an aqueous boundary layer, a fast Interfaclal chemical reaction leading to the formation of a membrane soluble alkylammonium salt and diffusion through the membrane was proposed. In this way, equations were derived which describe how composition changes, occurring In the course of the permeation process, Influence the membrane permeability. The experimental data were quantitatively explained by the derived equations. The results indicate that the monomerlc form of the trllaurylammonium nitrate salt 1s the species which 1s mainly responsible for the acid transport through the membrane. The diffusion coefficient of the permeating species and the order of magnitude of the thickness of the aqueous boundary layer were evaluated.     

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.