Microporous Hydrophobic Hollow Fiber Research Articles

Iron Control in Liquid Effluents: Pseudo-Emulsion Based Hollow Fiber Membrane with Strip Dispersion Technology with Pseudo-Protic Ionic Liquid (RNH3+HSO4-) as Mobile Carrier.

The transport of iron(III) from aqueous solutions through pseudo-emulsion-based hollow fiber with strip dispersion (PEHFSD) was investigated using a microporous hydrophobic hollow fiber membrane module. The pseudo-protic ionic liquid RNH3HSO4- dissolved in Solvesso 100 was used as the carrier phase. This pseudo-protic ionic liquid was generated by the reaction of the primary amine Primene JMT (RNH2) with sulphuric acid. The aqueous feed phase (3000 cm3) containing iron(III) was passed through the tube side of the fiber, and the pseudo-emulsion phase of the carrier phase (400 cm3) and sulphuric acid (400 cm3) were circulated through the shell side in counter-current operational mode, using a single hollow fiber module for non-dispersive extraction and stripping. In the operation, the stripping solution (sulphuric acid) was dispersed into the organic membrane phase in a tank with a mixing arrangement (a four-blade impeller stirrer) designed to provide strip dispersion. This dispersed phase was continuously circulated from the tank to the membrane module in order to provide a constant supply of the organic solution to the fiber pores. Different hydrodynamic and chemical parameters, such as feed (75-400 cm3/min) and pseudo-emulsion phases (50-100 cm3/min) flows, sulphuric acid concentration in the feed and stripping phases (0.01-0.5 M and 0.5-3 M, respectively), metal concentration (0.01-1 g/L) in the feed phase, and PPILL concentration (0.027-0.81 M) in the carrier phase, were investigated. From the experimental data, different diffusional parameters were estimated, concluding that the resistance due to the feed phase was not the rate-controlling step of the overall iron(III) transport process. It was possible to concentrate iron(III) in the strip phase using this smart PEHFSD technology.

Analysis of adiabatic heat and mass transfer of microporous hydrophobic hollow fiber membrane-based generator in vapor absorption refrigeration system

A microporous hydrophobic hollow fiber membrane-based generator (HFM-G) is expected to be an alternative type of generator in vapor absorption refrigeration system, which can be compact and lightweight with the enhanced heat and mass transfer. This paper pursues a comprehensive understanding of a detailed desorption mechanism of the proposed HFM-G, and suggests the feasible configuration for the practical use. A theoretical HFM-G mechanism is first introduced to gain an understanding of the adiabatic heat and mass transfer. A gas permeation test determines the nominal pore size of the membrane, which characterizes the mass transfer across the membrane. Transient experiments demonstrate the characteristics of the adiabatic desorption process on the HFM-G for wide range of feed solution concentrations under various practical operating conditions. A comparison shows that the experimental heat and mass transfer results are consistent with the theoretical values of adiabatic desorption heat and mass transfer on the HFM-G.

Mass Transfer and Fluid Hydrodynamics in Sealed End Hydrophobic Hollow Fiber Membrane Gas-liquid Contactors

Hollow fiber membrane modules have been extensively used as gas-liquid contactor devices to provide a high surface area within a small volume. Hollow fiber membrane contactors have been demonstrated in a wide range of application such as in gas stripping and gas absorption. In this study the performance of sealed end hydrophobic microporous hollow fiber membranes contactors were evaluated to remove dissolved oxygen from water via vacuum degassing process. Hollow fibers membranes used in the experiment were hydrophobic microporous polypropylene of 650 μm in outer diameter, 130 μm wall thickness and nominal pore size of 0.2 μm. Based on the experimentalresult the sealed end membrane contactor can remove oxygen from water as high as 3.4-gram oxygen per square meter of membrane area per hour. The oxygen flux decreases with increasing module-packing density for the same water velocity. The same effect also occurred for the mass transfer coefficient of the membrane contactors. The mass transfer coefficients were independent of fiber length within the range of study. Hydrodynamics analysis of the contactors showed that at the same Reynolds number pressure drops increase with increasing packing density due to an increase in friction between fibers and water.

Experimental And Mathematical Modeling Studies Of Liquid-Liquid Membrane Contactor

Experimental and modeling studies of the effect of tempetarature on liquid-liquid membrane contactor (LLMC) have been done. The experiments were conducted by varying temperature of 25 up to 80 0C, cross flow velocity from 0.02 to 0.05 m/s and feed concentration of 0, 5000 and 30,000 mg/l. In these experiments microporous hydrophobic hollow fiber polypropylene membrane with 0.2 μm was used as a contacting device. The modeling has been done by compiling mathematic equation of mass and heat transfers in liquid-liquid membrane contactor. Both the experimental and modeling result show, the increase in feed temperature increase the flux of pure water exponentially, whereas the flux decrease with increasing the permeate temperature. The feed temperature increase at higher temperature result in hogher flux increase. The concentration of pure water result in the range of 1.8 to 5.6 mg/l depending on feed concentration.Keywords : membrane contactor, modeling

Novel absorption refrigeration system with a hollow fiber membrane-based generator

Vapor absorption refrigeration systems using the LiBr–water pair can be an alternative to existing automobile air-conditioning systems. To this purpose, the new system must be compact enough to fit into automobiles, and robust against sloping roads and unexpected vibrations while driving. The system uses a micro-porous hydrophobic hollow fiber membrane-based generator (HFM-G) instead of the conventional generator in the absorption cycle. HFM-G extracts water vapor from the LiBr solution that is mechanically constrained by a hydrophobic membrane. This paper presents the results of a parametric steady-state simulation investigating how the HFM-G affects the proposed absorption cooling cycle. We first describe the mechanism of the HFM-G, and the system performance of the proposed cycle under various operating conditions is examined. Simulation results show that the proposed system can achieve a cooling capacity and COP of approximately 2.88 kW and 0.63, respectively, by incorporating the solution recirculation process.

Effect of selected spinning parameters on PVDF hollow fiber morphology for potential application in desalination by VMD

Poly(vinylidene fluoride) microporous hydrophobic hollow fibers were prepared using N-methyl pyrrolidone (NMP) as solvent, and water and low molecular weight poly(vinyl pyrrolidone) (PVP K-17) as pore forming additives. The effect of selected spinning parameters, i.e. composition and flow rate of the inner coagulant (bore fluid), on fiber properties was carefully investigated, keeping constant all the other parameters (composition and temperature of the polymeric dope, spinning rate, outer coagulant composition and temperature). It was found that fiber properties, in particular thickness and porosity, are strongly influenced by the composition and flow rate of the bore fluid. Fiber thickness decreases as bore fluid flow rate increases, as a consequence of enlargement of fiber inner diameter. While fiber porosity, expressed as void fraction, decreases when the liquid/liquid demixing rate decreases during coagulation, due to the reduction of macrovoids. The produced hollow fibers were tested using a vacuum membrane distillation (VMD) setup, both feeding double distilled water and synthetic seawater. The fibers produced reached average transmembrane water vapor fluxes as high as 19.50 (pure water) and 14.46kg/m2h (synthetic seawater), coupled with solute separation factors of about 99.99%. By analyzing the relationship between the fiber VMD performance, morphology and properties, it has been confirmed that VMD flux has strong dependence on porosity, which influences both the space available for evaporation and the thermal insulation during the process. This systematic study allowed us to show how fiber properties can be tailored by carefully acting on spinning parameters, in order to obtain high VMD performance both in terms of flux and salt rejection.

Application of hollow fiber membrane contactor for the removal of carbon dioxide from water under liquid–liquid extraction mode

In this study, we investigate the application of a hollow fiber membrane contactor operated in the LLE mode for the removal of dissolved CO 2 from water. The membrane contactor consists of hydrophobic polypropylene microporous hollow fibers. Experiments are performed to determine the extent of CO 2 removal from the feed water flowing through the lumens of the hollow fibers. The feed at different concentration levels of dissolved CO 2 was extracted using aqueous diethanolamine solution flowing on the shell side of the contactor. A mathematical model was developed, incorporating radial and axial diffusion of solute CO 2 in the lumen and its permeation through the pores of the membrane. The governing second order partial differential equation of species balance was numerically solved using the alternate direction implicit technique. The developed mathematical model was used to predict the concentration profiles of CO 2 and study its transport through water and membrane pores. The numerical value of the permeation coefficient obtained for CO 2 in the hollow fiber membrane was found to be in good agreement with the data in literature.

Modeling of a hollow fiber membrane biofilm reactor for nitric oxide removal: model development and experimental validation

AbstractBACKGROUND: A diffusion and reaction model was developed for a hollow fiber membrane biofilm reactor (MBfR) to control nitric oxide (NO) emissions. In the MBfR, waste gases containing biodegradable compounds pass through the lumen of microporous hydrophobic hollow fiber membranes. Soluble, biodegradable compounds diffuse through the membrane pores and partition into a biofilm attached to the membranes where they are biodegraded. The membranes serve as a support for the microbial population and provide a large surface area for mass transfer. A dynamic model was developed for the MBfR which assumed biodegradation via Monod kinetics and constant biofilm thickness and density. The model was validated using experimental data from a study of NO removal (100 ppm) from a combustion gas mixture in a bench‐scale MBfR with an acclimatized nitrifying population.RESULTS: NO gas was treated in a bench‐scale MBfR at varying liquid recirculation velocities of 0.8 to 2.0 cm s−1. The gas residence time (τ), calculated as the membrane lumen volume divided by the gas flow rate, was 1.9 s. NO removal efficiency for synthetic combustion gas ranged between 68% and 73% at room temperature (20 °C).CONCLUSION: The MBfR shows promise for treatment of waste gases from combustion processes. The model predicted an optimal liquid recirculation velocity of 1.5 cm s−1 for NO removal, which is in good agreement with experimental data. Sensitivity experiments with the numeric model indicated that removal was a strong function of the biofilm density and the Monod maximum specific growth rate (µmax). Copyright © 2010 Society of Chemical Industry

Synergistic separation of yttrium ions in lanthanide series from rare earths mixture via hollow fiber supported liquid membrane

Separation of yttrium ions from the mixture of rare earths in lanthanide series has been examined by a microporous hydrophobic hollow fiber supported liquid membrane. Cyanex 272 and TBP in kerosene are used separately as an extractant. Nitric acid solution is used as a stripping solution. Increasing the concentration of Cyanex 272 increases the percentages of extraction and stripping of yttrium from rare earths but slightly percentages are obtained by TBP. Interestingly, when TBP is added with Cyanex 272, the percentages of extraction and stripping increases. This is due to the synergistic effect of the extractants. Moreover, yttrium can be selectively extracted and stripped more than other lanthanide ions because the equilibrium constant decreases with an increase in atomic number or decreases with the ionic radius of the lanthanides. In other words, yttrium is separated selectively due to the smallest ionic radius while other lanthanides are separated with a decrease in ionic radius or an increase in atomic number.

Selective recovery of nickel ions from wastewater of stainless steel industry via HFSLM

High concentration of heavy metal ions in all kinds of effluents, especially in wastewater is of great concern for hazardous pollution due to their high toxicities and wide environmental spreading. The selective stripping or recovery of nickel ions from wastewater of the stainless steel-cold rolled plate process by hollow fiber supported liquid membrane was studied. The optimum conditions were examined in a batch process. The pH of feed, types and concentrations of the extractants, concentration of the stripping solution (sulfuric acid), flow rates of feed and stripping solutions, and volumetric ratio of feed to stripping solutions were investigated. The extractants, i.e., D2EHPA, Cyanex 301, Cyanex 272 and LIX 860-I were dissolved in kerosene as a membrane solution, which was supported by a microporous hydrophobic hollow fiber membrane extractor. Consequently, two consecutive modules of hollow fiber were applied to recover more nickel ions. The results showed that LIX 860-I was the most effective to selectively retrieve nickel ions from wastewater at a feed pH of 4. The percentage of the recovery and selectivity of nickel ions increased in accordance with an increase in the concentration of LIX 860-I and decreased after the concentration of LIX 860-I was higher than 0.8 M. It was found that the percentage of recovery of nickel ions increased with sulfuric acid concentration and lower flow rates of feed and stripping solutions. Higher nickel ions were obtained at the flow rates of feed and stripping solutions of 100 ml/min and reduced when the flow rates increased. In addition, in this study it is recommended to use equal volume of feed and stripping solutions of 3500:3500 (ml:ml) to attain more nickel ions recovery. For a single-module operation, the percentage of recovery of nickel ions was 58%, and 87% by double-module operation.

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 (ki) and membrane or organic phase (km) 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.

AUGMENTATION OF ABSORPTION AND DESORPTION RATES IN A HYDROPHOBIC MICROPOROUS HOLLOW FIBER CONTAINED CONTACTOR BY ADJUSTING OUTLET GAS PRESSURE

The absorption of dilute CO 22 into aqueous solutions of sterically hindered 2-methyl aminoethanol (MAE) and the desorption of CO 22 from CO 22 loaded MAE solutions into N2 stream were investigated separately for the various combinations of operational variables, using a hydrophobic microporous hollow-fiber (polytetrafluoroethylene, PTFE) contained gas-liquid contactor (HFCC) with aqueous solutions of MAE as liquid media in the shell side at 30°C. The absorption of CO2 from the lumen side in this contactor is governed by the resistance in the liquid and hollow-fiber phases. The resistance to diffusion in the hollow-fiber phase (membrane resistance) amounted to 78–83% of the total resistance. Such a high membrane resistance was believed to be caused by some liquid penetration into the pores of hydrophobic microporous hollow fibers. Thus, the outlet gas pressure in the lumen side of the contactor was raised above an atmospheric pressure or adjusted at 0.1017 to 0.1019 MPa (i.e., 0.0004–0.0006 MPa over-pressure) so that the pore penetration of the aqueous solution might be suppressed. By such an adjustment of outlet total gas pressure, the total resistance and the membrane resistance were shown to be decreased on average to 28% and 12%, respectively. By adjusting the outlet total gas pressure, the total resistances to mass transfer during desorption of CO2 from aqueous CO2-loaded MAE solutions could also be decreased on average to about 21%. For the simultaneous absorption-desorption operation in a single unit, both absorption and desorption fluxes approached the respective constant values or the steady state was attained, as the process time had elapsed. Both absorption and desorption fluxes at the steady state were augmented by adjusting the outlet total gas pressure. In addition, both absorption and desorption processes approached the steady state faster by adjusting the outlet total gas pressure. At the constant flux periods, the absorption flux was about ten times higher than the desorption flux whether the outlet total gas pressure was adjusted or not. Because the desorption-part area here is designed as ten times the absorption-part area, the total absorption rate (= absorption flux × absorption-part area) is believed to be almost balanced with the total desorption rate (= desorption flux × desorption-part area) at the constant flux periods.

Development and application of microporous hollow fiber protected liquid-phase microextraction via gaseous diffusion to the determination of phenols in water

A new organic solvent-free microextraction technique termed liquid–gas–liquid microextraction (LGLME) was developed. In this technique, a small amount (6 μl) of aqueous acceptor solution (0.5 M NaOH) is introduced into the channel of a 2.65 cm polypropylene hollow fiber. The hollow fiber is then immersed in an aqueous sample donor solution. The aqueous acceptor phase in the channel of the hollow fiber is separated from the sample solution by the hydrophobic microporous hollow fiber wall with air inside its pores. The analytes (phenols) passed through the microporous hollow fiber membrane by gas diffusion and were then trapped by the basic acceptor solution. After extraction, the acceptor solution was withdrawn into a microsyringe and injected into a capillary electrophoresis sample vial for subsequent analysis. Limits of detection of between 0.5 and 10 μg/l for eight phenols could be achieved. The relative standard deviations ( n = 6) of this technique between 2.7 and 7.6%. The technique also provides good enrichment factors for all the eight analytes.

Gas absorption in a hollow-fiber membrane contactor with pseudo-plastic liquid as an absorbent

Gas/liquid mass transfer characteristics of a membrane contactor with hydrophobic microporous hollow fibers were investigated under laminar flow conditions. Physical absorption of oxygen in a pseudo-plastic non-Newtonian liquid was studied. The experiments were carried out with aqueous solution of sodium carboxymethylcellulose. For comparison, the experiments with water as an absorbent were carried out as well. The influence of physical characteristics of liquids and operating conditions on oxygen absorption was examined. The results show that hydrophobic membrane contactors can be efficiently used for gas absorption in a pseudo-plastic liquid, especially when membrane resistance can be neglected.

ABSORPTION OF CO2 INTO AQUEOUS SOLUTIONS OF STERICALLY HINDERED METHYL AMINOETHANOL USING A HYDROPHOBIC MICROPOROUS HOLLOW FIBER CONTAINED CONTACTOR

ABSTRACT The absorption of dilute CO2 into aqueous solutions of sterically hindered 2-methyl aminoethanol (MAE) and the desorption of CO2 from CO2-loaded MAE solutions into N2 stream were investigated separately for the various combinations of operational variables, using a hydrophobic microporous hollow fiber (polytetrafluoroethylene, PTFE) contained gas-liquid contactor with aqueous solutions of MAE as liquid media in the shell side at 30°C. The absorption of CO2 in this contactor is governed by resistance in the liquid and hollow fiber phases. The resistance to diffusion in the hollow fiber phase amounts to 76–80% of the total resistance. Nevertheless, the absorption rates of CO2 into aqueous MAE solutions in this contactor are higher than those into aqueous solutions of sterically hindered 2-amino-2-methyl-1-propanol (AMP) in the stirred tank with a plane unbroken gas-liquid interface. The process of desorption of CO2 from CO2-loaded MAE solutions can be regarded as being controlled by diffusion and chemical reaction in both the stagnant film of the liquid phase and the liquid-filled pore of the hollow fiber phase under the slow or intermediate reaction regime. Both absorption and desorption rates under the simultaneous absorption-desorption operation in a single unit tend to approach the respective constant values as process time elapses. The total absorption rate here seems to be almost balanced with the total desorpion rate at the constant mass transfer rate periods.

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 (ki) and the organic mass transfer coefficient (km) 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).

Application of Hollow Fiber Contactor in Nondispersive Solvent Extraction of Pu(IV) by TBP

Data on dispersion‐free solvent extraction (DFSX) of Pu(IV) from acidic nitrate media using microporous hydrophobic polypropylene hollow fiber membrane contactor with tri‐n‐butylphosphate (TBP) employing as an extractant are being presented. The DFSX operation was carried out with various concentration of TBP in n‐dodecane by passing acidic feed containing Pu (IV) through the tube side at the flow rate of 5.83 cm3 s−1 and organic extractant through the shell side at the flow rate of 1.53 cm3s−1. Extraction studies were performed under different hydrodynamic conditions and the overall mass‐transfer coefficient was evaluated with countercurrent flow condition. It was possible to extract and concentrate Pu(IV) from aqueous phase by employing this technique. For back extracting the Pu, uranous nitrate and hydroxylamine hydrochloride solution as strippants were examined, which flowed through the tube side (flow rate: 6.11 cm3 s−1) and the loaded organic was passed through the shell side with the flow rate of 1.66 cm3s−1. Results revealed that ∼80% of Pu(IV) from oxalate supernatant waste could be extracted by utilizing this technique.

A study on the PP hollow fiber membrane contactor and its performances for removing ammonia from wastewater or mixed gas: I. Removal and recovery of ammonia from wastewater

Recent research indicated that hydrophobic microporous hollow fiber membrane Contactor could be used to separate volatile contaminants from wastewater efficiently. The factors that influence the effect of separation of NH3/H2O are investigated carefully. It is found that the average diameter of micropores, porosity and gas penetration rate of polypropylene (PP) hollow fiber membrane are maximized synchronously at draw elongation 260%. The modules assembled with this PP hollow fiber membrane have good performance for separation of NH3/H2O. It is found that the overall mass transfer coefficient (K) only is dependent on the temperature and flux of ammonia solution and independent of the pressure and concentration of ammonia solution. Concentration of absorbing acid influences slightly the overall transfer coefficients K while the absorbent supply is sufficient. Under this condition, the relationship between transfer coefficient and raw ammonia water flow rate can be described using the Sieder and Tate equation. K is directly proportional to v1/3 (v stands for the flow rate of ammonia solution). The removal rate of NH3 was about 96-98% in the lab. Further industrial tests have been carried out individually in catalyst and chemical fertilizer factories to treat wastewater containing ammonium, whose concentration ranged from 1000-10,000g/m3. Wastewater treatment amount was 9.6 m3/day and 24 m3/day in catalyst and chemical fertilizer factories respectively. Average removal rate of NH3 was 93.5% during 5 months of continuous operation in the catalyst factory. The fouling is not heavy because the wastewater containing ammonia did not pass through the membrane wall. It is efficient to get rid of membrane fouling by washing the membrane with dilute acid and the cleanout period was 3 days. PP hollow fiber membrane can be produced by the melt-spinning and drawing method. This paper also investigates the relationship between processing condition of PP hollow fiber membrane and its structure and performance.

ABSORPTION AND DESORPTION OF CO2 BY AQUEOUS SOLUTIONS OF STERICALLY HINDERED 2-AMINO-2-METHYL-1-PROPANOL IN HYDROPHOBIC MICROPOROUS HOLLOW FIBER CONTAINED CONTACTORS

To understand the behavior of separation of CO2 from CO2-N2 mixtures using a hydrophobic microporous hollow fiber (polytetrafluoroethylene) contained gas-liquid contactor with aqueous solutions of 2-amino-2-methyl-l-propanol (AMP) as liquid media in the shell side, first, the absorption of dilute CO2 into aqueous AMP solutions and the desorption of CO2 from CO2-loaded AMP solutions into N2 stream were investigated separately for various combinations of operational variables. Secondly, the simultaneous absorption and desorption in a single unit was performed to check the possibility of a long-term continuous operation. The resistance to diffusion in the hollow fiber phase during absorption amounted to ca. 86% of the total resistance, and slightly decreased with increasing AMP concentration. The AMP solution partially leaks into pores of the hollow fiber, and both the diffusion and chemical reaction of dissolved CO2 in the liquid-filled pores under the slow-reaction regime mainly control the overall absorption rate. If the physical diffusion in the liquid-filled part of the pore completely controlled the absorption process in the present hollow fiber contactor, the length of the liquid-filled part would be evaluated to be 72 ˜ 108 urn as compared to the total pore length of 500 um. The desorption rate was found to be independent of the gas velocity in the lumen side. The desorption process can be regarded as being controlled by diffusion and chemical reaction in both the stagnant film of the liquid phase and the liquid-filled pore of the hollow fiber phase under the slow or intermediate reaction regime. Simultaneous absorption and desorption process in a single contactor was found to be kept in a stable state at least until 20 h.

Use of modified membrane carrier system for recovery of gold cyanide from alkaline cyanide media using hollow fiber supported liquid membranes: feasibility studies and mass transfer modeling

This investigation is concerned with the applications of hollow fiber supported liquid membranes for the recovery of gold(I) (Au(CN) 2 −) from alkaline cyanide media using microporous hydrophobic hollow fiber with modified membrane extractant (carrier). The organic extractant used for gold(I) permeation was LIX79 alone and mixture of TOPO+LIX79 diluted with n-heptane. The mixture of LIX79+TOPO affords better performance than LIX79 alone. P Au value was 2.8×10 −5 cm/s with LIX79 alone, whereas P Au value was found to be 9.5×10 −5 cm/s with only TOPO membrane carrier. Transport of Au(CN) 2 − from alkaline cyanide solutions with TOPO alone was also observed indicating gold(I) complexation takes place most likely by solvation reaction mechanism (M +…Au(CN) 2·S n ). The permeability of Au(I) was enhanced by 220 folds by using mixture of TOPO+LIX79 with respect to only LIX79 and 57 times with respect to only TOPO while maintaining aqueous feed at pH 10.3. A model is presented which describes the transport mechanism, indicating different rate-controlling steps. The validity of this model was evaluated with experimental data and found to tie in well with theoretical values. In addition, selectivity of Au(I) with respect to Zn(II) and Ag(I) cyanide salts was improved. It was possible to recover Au(I) in presence of other metal cyanide salts of Fe(II), Cu(I), Ni(II), Ag(I) and Zn(II) which approves the potential of mixture of extractants (TOPO+LIX79) for hydrometallurgical solutions.