Aqueous Stripping Solution Research Articles

Removal of anionic dye from aqueous solution using a cationic carrier

Background The transport of Cibacron Red FN-R (Sigma-Aldrich, MO, USA) anionic dye through a methylene chloride (Merck, India) bulk liquid membrane containing a tetrabutylammonium bromide (TBAB; Merck, India) as an excellent carrier was studied. The extracted dye simultaneously stripped into aqueous stripping solution.

Use of bulk liquid membrane for the removal of Cibacron Red FN-R from aqueous solution using TBAB as a carrier

The transport of Cibacron Red FN-R anionic dye through a methylene chloride bulk liquid membrane (BLM) containing a tetra butyl ammonium bromide (TBAB) as an excellent carrier was studied. The extracted dye simultaneously stripped into aqueous stripping solution. The basic fundamental parameters were determined. These include pH of the feed, nitric acid concentration in the strip solution, TBAB concentration in the membrane phase, initial dye concentration in the feed phase and rate of stirring. The transport efficiency of dye increased with increasing carrier concentration from 6.06±0.1×10−6 to 3.85±0.1×10−4M. The transport study was highly selective for anionic dye and efficiency of transport was not affected by the presence of electrolytes such as sodium chloride and sodium sulphates in feed solution. The percentage of dye transported across the liquid membrane after 70min, was 95±0.1%. When the optimum parameters were used for real textile dyeing effluent for recovery of dyes, the results were found to be satisfactory.

Protein extraction by Winsor‐III microemulsion systems

Proteins (bovine serum albumin (BSA), α-chymotrypsin, cytochrome c, and lysozyme) were extracted from 0.5 to 2.0 g L(-1) aqueous solution by adding an equal volume of isooctane solution that contained a surfactant mixture (Aerosol-OT, or AOT, and a 1,3-dioxolane (or cyclic ketal) alkyl ethoxylate, CK-2,13-E5.6), producing a three-phase (Winsor-III) microemulsion with a middle, bicontinuous microemulsion, phase highly concentrated in protein (5-13 g L(-1)) and small in volume (12-20% of entire volume). Greater than 90% forward extraction was achieved within a few minutes. Robust W-III microemulsion systems were formulated at 40°C, or at 25°C by including a surfactant with shorter ethoxylate length, CK-2,13-E3 , or 1.5% NaCl (aq). Successful forward extraction correlated with high partitioning of AOT in the middle phase (>95%). The driving force for forward extraction was mainly electrostatic attractions imposed by the anionic surfactant AOT, with the exception of BSA at high ionic strength, which interacted via hydrophobic interactions. Through use of aqueous stripping solutions of high ionic strength (5.0 wt %) and/or pH 12.0 (to negate the electrostatic attractive driving force), cytochrome c and α-chymotrypsin were back extracted from the middle phase at >75% by mass, with the specific activity of recovered α-chymotrypsin being >90% of its original value.

Cobalt(II) membrane-extraction by DP-8R/Exxsol D100 using pseudo-emulsion based hollow fiber strip dispersion (PEHFSD) processing

The transport of cobalt(II) from acidic sulphate solutions through PEHFSD was investigated using the extractant DP-8R in Exxsol D100. The acidic feed solution containing Co(II) was passed through the tube side, and pseudo-emulsions of DP-8R/Exxsol D100 and sulphuric acid was passed through the shell side in counter-current mode, using a single microporous hydrophobic polypropylene hollow fiber contactor for extraction and stripping. In PEHFSD the aqueous strip (sulphuric acid) solution was dispersed in the organic membrane solution in a reservoir tank with an impeller stirrer to form a strip dispersion. This pseudo-emulsion phase is circulated from the tank to the membrane module to provide a constant supply of the carrier solution to the membrane micropores. Several hydrodynamic and chemical parameters, such as variation in feed pH (3–7), cobalt concentration in feed (0.17–1.7 × 10 −3 M), carrier concentration (0.16–1.28 M), etc., were investigated. Mass transfer modelling was performed and the validity of the model was evaluated with experimental data. Moreover, the system was applied in the cobalt purification of synthetic lithium solutions derived from the processing of rechargeable batteries, with cobalt/lithium separation factor values around 25.

In situ removal of Cephalexin by supported liquid membrane with strip dispersion

Cephalexin is an important and widely used semi-synthetic antibiotic. Cephalexin is traditionally produced by a 10-step chemical synthesis. An enzymatic synthesis for Cephalexin has been developed, and offers several advantages over the classical route. 7-Amino-3-desacetoxicephalosporanic acid and d-phenylglycine amide were used as initial substrates for the enzymatic synthesis of Cephalexin with liquid penicillin G acylase. In situ extraction was achieved with a supported liquid membrane (SLM) with strip dispersion system that used commercially available hollow fiber modules and the carrier Aliquat 336. The maximum yield of Cephalexin was increased from 32% to 42% when in situ removal was conducted using two hollow-fiber modules and an organic membrane solution containing 10 wt% Aliquat 336. Enzyme stability experiments were preformed and showed that the organic membrane solution did not significantly deactivate the enzyme. The final recovery of Cephalexin from aqueous stripping solutions was achieved using complexing agents. The combination of SLM and complexation can prevent enzyme deactivation, which commonly occurs when complexation is conducted in enzymatic reaction mixtures.

A study on separation and extraction of four main alkaloids in Macleaya cordata (Willd) R. Br. with strip dispersion hybrid liquid membrane

A technique based on strip dispersion hybrid liquid membrane was developed for the separation and extraction of four main alkaloids from fruits of Macleaya cordata (Willd) R. Br. A microporous polypropylene membrane impregnated with an organic membrane solution comprised the heart of the strip dispersion hybrid liquid membrane system. The membrane solution was made by dissolving a cationic carrier, di-(2-ethylhexyl) phosphoric acid in an inexpensive, less toxic membrane solvent, kerosene. The transport of alkaloids from an aqueous feed solution through the membrane to a strip dispersion phase was driven by the concentration gradient of H(+) and facilitated by di-(2-ethylhexyl) phosphoric acid. The effects of the extraction time and reuse times of the membrane, the strip solution composition, the carrier concentration, the volume ratio of the aqueous strip solution to the organic membrane solution, and the flow rates of the feed solution and the strip dispersion phase on the transport of alkaloids were investigated. Under the optimal conditions, the permeability coefficients obtained for the four main alkaloids allocryptopine, protopine, sanguinarine, and chelerythrine were 1.66, 1.99, 2.98, and 3.06 x 10(-4) cm/s, and the transport efficiencies were as high as 68, 77, 83, and 85%, respectively.

Supported liquid membranes with strip dispersion for the recovery of Cephalexin

The removal and recovery of Cephalexin from aqueous solutions by supported liquid membranes (SLMs) with strip dispersion has been studied. Experiments used a Liqui-Cel ® hollow-fiber module as a mircoporous support and an organic membrane solution consisting of Aliquat 336, Isopar L (isoparaffinic hydrocarbon solvent), and 1-decanol. The aqueous strip solution was composed of potassium chloride and citrate buffer. The presence of the strip dispersion, formed by dispersing the aqueous strip solution in the organic membrane solution with a mixer, on the shell-side of the hollow-fiber module ensures SLM stability. Various experimental parameters such as strip dispersion mixing rate, Aliquat 336 concentration in the organic membrane phase, KCl and citrate buffer concentrations in the aqueous strip solution, volume of aqueous strip solution, and feed and strip dispersion flow rates were investigated. High extraction and recovery rates were achieved when maintaining a proper pH in the aqueous strip solution combined with an excess of KCl. Typical results using an Aliquat 336 concentration of 2.5 wt% (48 mM) have shown >99% extraction, recovery rates of 96–98%, and enrichment ratios of 1.6–3.3 from a feed solution containing 15 mM of Cephalexin. Mass transfer resistances were analyzed, showing the resistance from the extraction reaction to be dominant.

Au(I) extraction by LIX-79/ n-heptane using the pseudo-emulsion-based hollow-fiber strip dispersion (PEHFSD) technique

The extraction of Au(I) from alkaline cyanide solutions through PEHFSD was conducted in a microporous hydrophobic polypropylene hollow-fiber membrane contactor. The organic extractant LIX-79 ( N, N-bis(2-ethyl hexyl)guanidine) in n-heptane was used. The alkaline cyanide feed solution containing Au(I) was passed through the tube side, and pseudo-emulsions of LIX-79/ n-heptane and NaOH were passed through the shell side in counter-current mode, using a single microporous hydrophobic polypropylene hollow-fiber contactor for extraction and stripping. In PEHFSD the aqueous strip (0.2 M NaOH) solution is dispersed in the organic (12% LIX-79/ n-heptane) membrane solution in a container with a mixing arrangement (impeller stirrer) designed to form a strip dispersion. The strip dispersion is circulated from the mixer to the membrane module to provide a constant supply of the LIX-79/ n-heptane solution to the membrane pores. Various hydrodynamic and chemical parameters, such as variation in feed pH; gold cyanide concentration in feed; variation in concentrations of NaOH, LIX-79/ n-heptane and Au(I); variation in feed, strip and LIX-79/ n-heptane volume ratios and variation in feed and strippant flow rates, were investigated. Mass transfer modeling was performed and the validity of the model was evaluated with experimental data and found to tie in well with theoretical values. It was possible to concentrate Au(I) in product (NaOH) using the PEHFSD technique.

Pseudohydroxide Extraction from Aqueous Sodium Hydroxide Solutions with 3,5‐di‐tert‐Butylphenol in Isopar® L Modified with 1‐Octanol

Pseudohydroxide extraction (PHE) was investigated for recovering sodium hydroxide (NaOH) from alkaline process solutions. PHE relies on the deprotonation of a lipophilic weak acid by hydroxide ion with concomitant transfer of sodium ion into an organic phase. Contact of the sodium‐loaded organic phase with water results in the reconstitution of the extractant in the organic phase and NaOH in the aqueous phase, thus leading to a process in which NaOH equivalents are transferred from an alkaline feed solution to an aqueous stripping solution. In this work, we investigated PHE using a process‐friendly diluent—Isopar® L. The lipophilic cation exchanger 3,5‐di‐tert‐butylphenol (35‐DTBP) was used as the extractant. The Isopar® L diluent was modified with 1‐octanol to improve its solvation properties and the solubility of 35‐DTBP so that practical Na+ concentrations could be achieved in the process solvent. The PHE mechanism at process‐relevant conditions was explored by Raman and Fourier transform infrared spectroscopic measurements. Complementary electrospray ionization mass spectrometry studies were also performed. Equilibrium computer modeling suggested that the Na+ extraction behavior can be largely explained by the formation of 1∶1 and 1∶2 Na/35‐DTBP species in the organic phase. Extraction isotherms obtained using simulated caustic leaching solutions indicate the potential utility of this approach for recycling NaOH from complex alkaline mixtures.

Selective ω-thiocaprolactam-based recovery of Au(III) from chloride media in solvent extraction and polymer inclusion membrane systems

The selective transport of Au(III) over Cu(II) and Hg(II) using ω-thiocaprolactam as extractant and carrier in solvent extraction and polymer inclusion membrane transport experiments is discussed. Solvent extraction experiments were carried out using the extractant dissolved in chloroform to establish the chemical equilibria involved in the Au(III)-ω-thiocaprolactam separation system. Au(III) is extracted into the organic phase quantitatively ( E (%) > 99%) at low extractant concentrations from aqueous HCl solutions. Cu(II) extraction kinetics is slow compared to Au(III) extraction, allowing for the efficient separation of both metals. Polymer inclusion membranes (PIMs) are designed as alternatives to the use of high amounts of hazardous and expensive reagents. Several stripping phases were tested. Up to 70% of Au(III) can be recovered from 1 M HCl feed aqueous phase solutions. Interference from Cu(II) or Hg(II) is negligible at short times (160 min) in competitive ([M(II, III)] 0,feed = 0.1 mM) membrane transport experiments using a cellulose triacetate/NPOE/ω-thiocaprolactam PIM and a potassium iodide–hydrochloric acid aqueous stripping solution. Apparent diffusion coefficients in the membrane for Au(III) and Hg(II) in the system were estimated to be 2.2 × 10 −11 and 3.4 × 10 −15 m 2 s −1, respectively.

Permeation study on the hollow-fiber supported liquid membrane for the extraction of Cobalt(II)

The transport of Co(II) through hollow-fiber-supported liquid membrane containing di-(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in kerosene was examined. The mass transfer rate, expressed as permeability, P, focused on diffusion through the aqueous layer in the feed solution, the organic layer and the aqueous layer in the stripping solution. Experiments were performed as a function of aqueous feed solution velocity (100-500 ml/min), carrier concentration (0.1-20% v/v), aqueous stripping solution velocity (100-1,000 ml/min) and feed concentration (100-1,000 ppm) with 0.1 M HCl in the product phase. pH of the feed solution was 5.0. The measured permeabilities were compared to generally accepted mass transfer correlations. The validity of the prediction was evaluated with the experimental data, and the data were found to tie in well with the theoretical values. The model is the reported describing 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. From this study, the model has good potential for the prediction of permeability of Co(II).

Separation of Drug Traces from Water with Particular Membrane Systems

The purpose of the present project is to examine the applicability of certain natural biological and liquid membranes for the separation of drugs of environmental concern such as ibuprofen, diclofenac, carbamazepine, and sulfamethoxazol from dilute aqueous solutions. Different types of intestine parts of cattle, sheep, and pig were applied as biological flat sheet membranes after different modes of pretreatment. Best results were obtained with special parts of cattle appendix. The concentration of each drug in the aqueous feed phase was in the range of 0.1–10 mg (cm3)−1, the pH-values adjusted between 8 and 10. Pure water was used as the permeation phase. The influence of experimental parameters such as stirring velocity, temperature, pH-value, salt concentration, and the presence of surfactants as well as humic substances was studied. Under all conditions chosen the combined drugs permeate simultaneously through the natural membranes as the permeation kinetics of the individual compounds are very similar, while humic compounds were retained. Additional treatment of the permeate with liquid or solid phase extraction techniques increases crucially the depletion of the drugs from the feed. The mass transfer of the pharmaceuticals through the liquid membranes was carried out in three-compartment transport cells and supported liquid membrane-chambers. The three-phase liquid bulk membrane systems consisted of an aqueous feed solution, an organic solvent (dihexyl ether, decane, undecane, or decanol) with and without a dissolved sulfonic acid, tertiary amine or Cu(II)-chelate compound as a liquid bulk membrane and an aqueous stripping solutions containing dilute solutiuons of Na2CO3, NaOH, HCl, or HClO4. The transport of the drugs shows some differences, which can be attributed to their acid/base-behavior and partition coefficients log K ow. High extraction yields were obtained for sulfamethoxazol and carbamazepine by using polar organic solvents. Maximum transport efficiencies were obtained for the acidic compounds ibuprofen and diclofenac. They were completely extracted by using dihexyl ether loaded with octane sulfonic acid. A pH-gradient between feed and strip increases the efficiency of the transport. Certain three-phase compositions were successfully utilized in supported liquid membrane systems (SLM) so that high enrichment factors (˜75) were achieved for traces of diclofenac and ibuprofen. The solid and liquid membrane systems employed aim for technical as well as analytical purposes, such as sample pretreatment prior to HPLC-UV or LC-MS analysis of drug traces.

Extraction of l-phenylalanine in hollow fiber membrane

Dispersion free reactive extraction of l-phenylalanine has been studied using a hollow fiber (HF) membrane module. l-Phenylalanine could be extracted from an aqueous solution having a pH above the p K a2 value to an organic phase containing Aliquat-336 as the extractant and xylene as the solvent. The solute could be stripped from the organic phase to another aqueous stripping solution of pH maintained below the isoelectric point of l-phenylalanine. The extraction cum stripping process appear to rely on pH dependence of the distribution coefficient of phenylalanine in the reactive extraction system. The solute recovery and mass transfer rate were found to be appreciable and the experimentally observed low value of height of transfer unit (HTU) indicates good prospect of HF membrane for commercial exploitation.

Ce(III) recovery by supported liquid membrane using polyethylene hollow fiber prepared via thermally induced phase separation

High-density polyethylene (HDPE) hollow fiber membranes were prepared via thermally induced phase separation (TIPS). The pore size at the outer surface was quite smaller than that at the inner surface and the membrane structure was asymmetric. A membrane module was prepared by the obtained hollow fiber membranes. Experiments on the carrier-mediated transport of Ce(III) through supported liquid membranes (SLMs) were performed using the membrane module. The SLMs consisted of organic solutions of octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and tributyl phosphate (TBP) in dodecane absorbed into the microporous HDPE hollow fiber membrane. Effect of the aqueous strip solution flow rate on the membrane performance was investigated.

Removal and recovery of metals and other materials by supported liquid membranes with strip dispersion.

This paper reviews recent advances in supported liquid membranes (SLMs) with strip dispersion for removal and recovery of metals including chromium, copper, zinc, and strontium; it also discusses potential applications of SLMs for removal and recovery of other materials, including cobalt and penicillin G. The technology for chromium that we developed, not only removes the Cr(VI) from about 100-1,000 ppm to less than 0.05 ppm in the treated effluent allowable for discharge or recycle, but also recovers the chromium product at a high concentration of about 20% Cr(VI) (62.3% Na(2)CrO(4)) suitable for resale or reuse. In other words, we have achieved the goals of zero discharge and no sludge. The stability of the SLM is ensured by a modified SLM with strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution in a mixer. The strip dispersion formed is circulated from the mixer to the membrane module to provide a constant supply of the organic solution to the membrane pores. The copper SLM system that we have identified, not only removed the copper from 150 ppm in the inlet feed to less than 0.15 ppm in the treated feed, but also recovered the copper at a high concentration of greater than 10,000 ppm in the strip solution. For the zinc SLM system identified, zinc at an inlet feed concentration of 550 ppm was removed to less than 0.3 ppm in the treated feed, whereas a high zinc concentration of more than 17,000 ppm was recovered in the strip solution. For strontium removal, we synthesized a family of new extractants, alkyl phenylphosphonic acids. The SLM removed radioactive (90)Sr to the target of 8 pCi/L or lower from feed solutions of 300-1,000 pCi/L. The SLM removed cobalt from about 525 ppm to 0.7 ppm in the treated feed solution, concentrating it to at least 30,000 ppm in the aqueous strip solution. Concerning penicillin G recovery, the SLM removed penicillin G from a feed of 8,840 ppm and concentrated it to a high concentration of 41,011 ppm in the aqueous strip solution with a high recovery of about 93%.

Removal and Recovery of Copper and Zinc by Supported Liquid Membranes with Strip Dispersion

We have developed and scaled up effective supported liquid membrane (SLM) systems with strip dispersion for the selective removal and recovery of copper and zinc from he Berkeley Pit water containing about 150 ppm copper, 550 ppm zinc, and other metals. The stability of the SLM has been ensured by an improved SLM with strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution in a mixer. The strip dispersion formed is circulated from the mixer to the membrane module to have a constant supply of the organic solution to the membrane pores. The copper SLM system using nonylsalicyl aldoxime and ketoxime not only removed removed the copper to less than 0.1 ppm in the treated feed allowable for discharge or reuse, but also recovered the copper at a high concentration of greater than 10,000 ppm in the strip solution suitable for resale or reuse. For he zinc SLM system with di(2,4,4-trimethylpentyl) dithiophosphinic acid, the zinc was removed to less than 0.3 ppm in the treated feed while a high zinc concentration of more than 17,000 ppm was recovered in the strip solution. The scale-up results from pilot runs agreed reasonably well with the laboratory results. Both the copper and zinc concentrations in the treated feed met the target specifications for discharge whereas both the strip solutions recovered ad high purity for reuse. Thus, the goals of zero discharge and no sludge have been achievable.

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.

Supported liquid membranes for removal and recovery of metals from waste waters and process streams

AbstractSupported liquid membranes (SLMs) are very effective for the removal and recovery of metals from waste waters and process streams since they combine extraction and stripping, into one step. The one‐step membrane process provides the maximum driving force for the separation of a targeted metal, leading to the best possible clean‐up and recovery rates. The stability of the SLM has been ensured with strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution in a mixer. The strip dispersion formed is circulated from the mixer to the membrane module to provide a constant supply of the organic solution to the membrane pores. We have identified effective SLM systems, operating at a feed pH < 3 for the removal and recovery of copper, zinc, and nickel. Goals of zero discharge and no sludge are achievable.

New membrane technology for removal and recovery of chromium from waste waters

AbstractWe have developed new supported liquid membrane (SLM) technology for removal and recovery of chromium from waste waters. The technology not only removes the Cr (VI) to less than 0.05 ppm in the treated effluent allowable for discharge or recycle, but also recovers the product at a high concentration of about 20% (62.3% Na2CrO4) suitable for resale or reuse. In other words, we have achieved the goals of zero discharge and no sludge. The chromium flux in its entire range from low Cr (VI) concentrations in the feed solution to high feed concentrations, at which the carrier saturation of the facilitated transport mechanism occurs, has been in good agreement with a film model. The stability of the SLM has been ensured by strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution in a mixer. The strip dispersion formed is circulated from the mixer to the membrane module providing a constant supply of the organic solution to the membrane pores.

Backward extraction of reverse micellar encapsulated proteins using a counterionic surfactant

The back-extraction of proteins encapsulated in AOT reverse micelles was performed by adding a counterionic surfactant, either TOMAC or DTAB. This novel backward transfer method gave higher backward extraction yields compared to the conventional method with high salt and high pH of the aqueous stripping solution. The protein activity was maintained in the resulting aqueous phase, which in this case had a near neutral pH and low salt concentration. A sharp decrease of the water content was observed in the organic phase corresponding to protein back-extraction using TOMAC. The backward transfer mechanism was postulated to be caused by electrostatic interaction between oppositely charged surfactant molecules, which lead to the collapse of the reverse micelles. The back-extraction process with TOMAC was found to be very fast; more than 100 times faster than back-extraction with the conventional method, and as much as 3 times faster than forward extraction. The formation of 1:1 complexes of AOT and TOMAC in the solvent phase was observed, and these hydrophobic complexes could be efficiently removed from the solvent using adsorption onto Montmorillonite in order for the organic solvent to be reused. A second cationic surfactant, DTAB, confirmed the general applicability of counterionic surfactants for the backward transfer of proteins.