Comparison between supported gas membrane process and supported liquid membrane process for the separation of NH3 from aqueous media containing NH3 and CO2

A comparison between the hollow fibre supported gas membrane (SGM) process and the hollow fibre supported liquid membrane (SLM) process for the separation of NH₃ from aqueous solutions containing NH₃ and CO₂ was performed. The experimental data as well as the model simulation demonstrate that the SLM process can remove NH₃ from aqueous solutions of NH₃ and CO₂ at a higher rate than the SGM process when the NH₃ loading is low or the ratio of NH₃ to CO₂ is low. This study suggests that the proper combination of the SGM process and the SLM process can strip NH₃ more effectively from aqueous solutions containing NH₃ and CO₂.     

Cobalt removal from waste‐water by means of supported liquid membranes

BACKGROUND: Supported liquid membranes (SLM) are an alternative technique to remove and recover metals from diluted process solutions and waste‐water. In the present work, the removal of Co(II) from a synthetic CoSO₄ solution containing initial amounts of cobalt(II) in the range 100–200 ppm (0.1–0.2 g dm^?3) has been studied on a pilot scale. By performing batch equilibrium experiments, the optimal settings, i.e. the composition of the organic phase, the pH of the feed, the type and concentration of the stripping agent were determined. RESULTS: It is shown that the equilibrium characteristics of a synergistic extractant mixture containing di‐2‐ethyl‐hexylphosphoric acid (D2EHPA) and 5‐dodecylsalicylaldoxime (LIX 860‐I) are superior to D2EHPA. Both hydrochloric acid and sulfuric acid have been evaluated as stripping solutions in liquid–liquid extraction tests and as the receiving phase in a SLM configuration. Although equilibrium tests showed no difference in stripping characteristics between both chemicals, it was observed that in a SLM configuration the stability of the system when hydrochloric acid is used is poor. With a commercially available SLM module (Liqui‐Cel Extra‐Flow 4 × 28) having a surface area of 19 m², a steady Co(II) flux of 0.140 gm^?2h^?1 has been obtained at influent concentrations of cobalt between 100 and 200 ppm with 3 mol dm^?3 sulfuric acid as stripping phase. CONCLUSIONS: The results obtained show that a supported liquid membrane containing a synergistic mixture of LIX 860‐I and D2EHPA gives the possibility of recovering cobalt from dilute solutions. Copyright © 2008 Society of Chemical Industry     

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.     

Studies on the Recovery of Uranium from Phosphoric Acid Medium by D2EHPA/n-Dodecane Supported Liquid Membrane

Abstract

Present studies deal with the application of supported liquid membrane (SLM) technique for the separation of uranium (VI) from phosphoric acid medium using Di-2 ethyl hexyl phosphoric acid (D2EHPA)/n-dodecane as a carrier and ammonium carbonate as a receiving phase. The studies involve the investigation of process controlling parameters like feed acidity of phosphoric acid, carrier concentration, stripping agents, and the effect of thickness and the pore size of the membrane. The transport of uranium decreases with increase in the concentration of phosphoric acid in feed solution whereas it increases with increase in carrier concentration in supported liquid membrane. More than 90% uranium (VI) is recovered in 360 minutes using 0.5 M D2EHPA/dodecane as carrier and 0.5 M ammonium carbonate as stripping phase from the 0.001 M H₃PO₄ feed. Lower concentration of phosphoric acid and higher carrier concentration is found to be the most suitable condition for maximum transport of uranium (VI) from its lean sources like commercial phosphoric acid and analytical wastes generated from the analysis of uranium by Volumetric (Davis-Gray) method.     

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.     

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.     

Studies on permeation of uranium (VI) from phosphoric acid medium through supported liquid membrane comprising a binary mixture of PC88A and Cyanex 923 in n-dodecane as carrier

Present studies deal with the application of supported liquid membrane (SLM) technique for the separation of uranium (VI) from phosphoric acid medium using a binary mixture of 2-ethyl hexyl phosphoric acid-mono-2-ethyl hexyl ester (PC88A) and neutral donor which is a mixture of four tri-alkyl phosphine oxide better known as Cyanex 923 in n-dodecane as a carrier and (NH₄)₂CO₃ as a receiving phase. Various parameters like feed acidity, nature of strippant, carrier concentration, membrane pore size, membrane thickness etc. which affect the transport of U(VI) have been studied in detail. Experiments have also been carried out to see the transport behaviour of different fission products from a diluted High Level Waste (HLW) solution. Stability of the membrane against the leaching of the extractant and stability of the membrane support have also been investigated. We have tried to model the physicochemical transport of U(VI) in SLM as well as establishing the mechanism (Diffusion controlled) of transport. More than 95% uranium (VI) is recovered in 360 min using a binary mixture of 0.60 M PC88A and 0.15 M Cyanex 923 in n-dodecane as carrier and 0.5 M (NH₄)₂CO₃ as stripping phase from the 0.5 M H₃PO₄ feed. Lower concentration of H₃PO₄ (0.5 M) and optimum carrier concentration (0.60 M PC88A + 0.15 M Cyanex 923) in the mole ratio of 4:1 is found to be the most suitable condition for maximum transport of uranium (VI). The optimum conditions obtained from this study was also applied to recover uranium from analytical waste in phosphoric acid medium generated in the laboratory.     

Extraction of strontium ion from sea water by contained liquid membrane permeator

To develop a liquid membrane permeator that extracts strontium ion from sea water effectively and continuously, we investigated the extraction of strontium ion from artificial and natural sea water in a contained liquid membrane permeator. The permeator consists of a liquid membrane and two cells for aqueous solutions. The liquid membrane containing D₂EHPA(di-2-ethylhexyl-phosphoric acid) and DCH18C6(dicyclohexano-18-crown-6) is trapped between two hydrophobic microporous polyethylene films and separates sea water and the 0.2 M H₂SO₄ aqueous stripping solution. The effects of various operating parameters on the extraction of strontium ion were experimentally examined. The extractant of DCH18C6 -D₂EHPA mixture in kerosene had a synergistic effect on the extraction of strontium ion. The permeator extracted strontium ion from sea water effectively and continuously with long membrane lifetime.     

Column Design for Recovery of NH3 and CO2 from Wastewater in a Urea Plant

Abstract

The stripping of CO₂ and NH₃ from chemically reactive dilute aqueous solution in a packed column is modeled using a section-to-section calculation procedure. Equilibrium chemical reaction is accounted for by correcting the liquid film mass transfer coefficient through enhancement factors for the transferring species. Comparison with pilot scale stripping experiments shows that the packed height required for a given separation can be predicted to within 7% on average.     

Absorption of NO from simulated flue gas by using NaClO2/(NH4)2CO3 solutions in a stirred tank reactor

Experiments were performed in a stirred tank reactor to study the absorption kinetics of NO into aqueous solutions of NaClO₂/(NH₄)₂CO₃ solutions. The absorption process is a fast pseudo-reaction, and the reaction was found to be second-order with respect to NO and first-order with respect to NaClO₂, respectively. The frequency factor and the average activation energy of this reaction were 4.56×10¹¹ m⁶/(mol² s) and 33.01 kJ/mol respectively. The absorption rate of NO increased with increasing reaction temperature, but decreased with increasing (NH₄)₂CO₃ solution.     

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.     

Carrier Mediated Transport of Thorium from Nitric Acid Medium using 2-Ethyl Hexyl Hydrogen 2-Ethyl Hexyl Phosphonate (PC88A)/N-Dodecane as Carrier

The present study deals with the application of supported liquid membrane (SLM) technique for the separation of thorium from nitric acid medium using 2-ethyl hexyl hydrogen 2-ethyl hexyl phosphonate (PC88A) as a carrier and aqueous ammonium carbonate as a receiving phase. The effects of feed acidity, nature of strippant, and membrane pore size and membrane thickness on the transport of thorium have been studied in detail. Transport behavior of uranium (²³³U) and fission products from a radioanalytical laboratory waste is also studied. Stability of the membrane against the leaching of the extractant and stability of the membrane support have been investigated. An attempt has been made to model the physicochemical transport of thorium in SLM and establish the mechanism of thorium transport. Transport of thorium increased from 25% to about 96% using 0.75 M PC88A in n-dodecane as carrier and 2 M ammonium carbonate as stripping phase as the feed acidity decreased from 4 M HNO₃ to 0.5 M HNO₃. Optimum conditions obtained from this study were applied to recover thorium and ²³³U from analytical waste generated in the laboratory.     

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     

Transport of Palladium(II) through Trioctylamine Liquid Membrane

Abstract

The permeation behavior of palladium(II) through a supported liquid membrane (SLM) impregnated with trioctylamine (TOA) in kerosene has been investigated. By selecting perchloric or nitric acid as a stripping agent, Pd(II) was transported through the SLM containing 0.5 M TOA and 20% 1-octanol without remaining in the liquid membrane. The permeation rate (k _{f. obs}) of Pd(II) for HNO₃ was faster than that for HClO₄. Palladium(II) was concentrated across the SLM from the 0.5 M CHI solution into the HClO₄ or HNO₃ solution.     

Analysis of the mechanism of rare earth metal permeation through a liquid membrane with a chelating agent in the

The effect of adding a water-soluble chelating agent, diethylenetriaminepentaacetic acid (DTPA), to the feed phase was studied on the selective permeation of rare earth metal ions (Ln³⁺) through a supported liquid membrane (SLM) containing 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (PC-88A). High selectivity of Pr to Nd was observed at a pH of 2.0 in the stripping phase, and selective permeation of La was observed at higher pH values. The permeation mechanism of the Ln³⁺ was analyzed, and the above results were explained by the change in the concentrations of free Ln³⁺ in the feed phase and Ln³⁺/PC-88A complexes in the SLM with pH.     

The Hafnium-Selective Extraction Fom a Zirconium(Hafnium) Heptafluoride Ammonium Solution Using Organophosphorus-Based Extractants

ABSTRACT

The suitability of the organophosphorus-based extractants, DiOPA, Ionquest 801 and D2EHPA was evaluated for the selective extraction of Zr and Hf from an (NH₄)₃Zr(Hf)F₇ acidic solution using both dispersive and pertraction solvent extraction (SX). A stock solution of (NH₄)₃Zr(Hf)F₇ was dissolved in either HCl or H₂SO₄ (0.1–8 M). The following extraction variables were investigated: type and concentration of the acidic solution, the contact time, and extractant to metal ratio. Subsequently, the stripping was investigated using (NH₄)₂CO₃, CaCl₂, H₂SO₄ and C₂H₂O₄ in the concentration ranges of 0–2 M. During extraction, scrubbing and stripping using D2EHPA, CaCl₂ and C₂H₂O₄, the Zr purity was increased from 97.2% to 99.0%. When extracting from 4 M H₂SO₄ with 9 wt% D2EHPA, a Hf selectivity of 32% was observed where after stripping with C₂H₂O₄ resulted in a 98.7% recovery of Zr. With 1.2 M CaCl₂ as stripping liquor, almost no Hf and 75% Zr stripping was obtained. During the pertraction 72% Hf and 44% Zr extraction was achieved after 180 min when extracting with 9 wt% D2EHPA from 4 M H₂SO₄. Pertraction based stripping with 1.2 M C₂H₂O₄ yielded 75% of both Zr and Hf, while stripping with 2 M CaCl₂ resulted in 58% Hf stripped with almost no Zr stripping.     

Liquid Membrane Permeation with Supported Liquid Membranes and their Application in Li-ion Battery Recycling

A study of liquid membrane permeation with supported flat sheet membranes was performed. The goal of the project was to improve the stability and accuracy of supported liquid membranes (SLM) by avoiding short circuiting of phases with technical measures. Mass transfer and stability tests were carried out with the test system Zn²⁺|HDEHPA|H⁺. The effect of operation conditions on mass transfer and accumulation of Zn²⁺ in the stripping phase was investigated. A process for the recycling of Li-ion batteries including two SLM separation stages was developed. Experimental findings confirmed the feasibility of this process, yielding high purity streams of aqueous copper, cobalt, and lithium solutions.     

Specific membrane transport of silver and copper as Ag(CN)3 and Cu(CN)4 ions through a supported liquid membrane using K-crown ether as a carrier

Facilitated transport of silver and copper from cyanide solutions through a supported liquid membrane (SLM) containing K⁺-crown ether as a carrier is described. The SLM used is a thin porous polypropylene (Celgard 2500, 2400) membrane impregnated with dibenzo-18-crown-6 (DB18C6), diaza-18-crown-6 (DA18C6), hexathia-18- crown-6 (HT18C6) and hexaaza-18-crown-6 (HA18C6) dissolved in a mixture of ethanol/chloroform (v/v). K₋⁺-crown ether showed a high efficiency to carry silver and copper as Ag(CN)₃²⁻ and Cu(CN)₄³⁻ species through the SLM. However, the mass flux of both silver and copper ions decreases when concentration of cyanide ions in the feed phase increases due to the difference in stability of the complexes M(CN)_nⁿ⁻(M=Ag, Cu) when n increases from 2 to 4. This was related to the partition of the species in the aqueous phase using a theoretical model.     

A fixed-site carrier composite membrane for NH3/N2 separation

The use of a composite membrane for NH₃ separation is presented. A polyethylene/polyetherimide/ carrier composite is shown to permeate NH₃ selectively from NH₃/N₂ mixture at ambient conditions, attaining a maximum selectivity of 480 at 1% NH₃ feed concentration. Experimental data indicate facilitated-transport-mode membrane function.     

萃取凝胶膜过程工艺条件对镍离子传质效率及稳定性增进

利用交联反应在PVDF超滤膜表面创新性的构建含有萃取剂磷酸二异辛酯的聚二甲基硅氧烷-正硅酸乙酯体系萃取凝胶膜（EGM）;并对其基本物理化学性质进行了表征。研究了EGM过程中料液相循环方式、料液相及反萃相浓度与流量、水相温度、组件装填密度等工艺条件对镍离子传质性能及EGM运行稳定性的影响规律。9 h实验结果表明在室温水相温度为22℃条件下,当工艺运行条件为料液相流量1900 ml·min^-1、反萃相流量93 ml·min^-1、组件装填密度14%、料液相循环于壳程时,EGM对镍离子的萃取性能及稳定性达到最佳值。在此基础上,对该系统进行了60 h稳定性实验,并与传统支撑液膜进行了对比。结果显示传统支撑液膜持续运行35 h后通量降为0,衰减率为100%;而EGM持续运行60 h后通量衰减率仅为27.1%;同时EGM初始传质通量相比于传统支撑液膜提高了6.8倍,体现了EGM过程在传质通量大幅提升和长期运行稳定性显著增进方面具有双重优势。