Predispersed Solvent Extraction Research Articles

Selective removal of copper and nickel ions from synthetic process water using predispersed solvent extraction

AbstractSelective predispersed solvent extraction and the stripping of copper and nickel ions from synthetic process water containing calcium ions was investigated, and the effect of four experimental parameters on extraction efficiency was studied. The extraction process was performed in two stages. In the first stage, maximum copper extraction was targeted with nickel extraction minimized. During the second stage, nickel was extracted from the remaining copper‐free aqueous solution and optimum experimental conditions for maximum nickel recovery were determined. In order to investigate the effect of experimental parameters (extractant concentration, phase volume ratio (PVR), equilibrium pH, and calcium concentration) on the nickel extraction, response surface methodology (RSM) was used. It was found that equilibrium pH, extractant concentration, and calcium concentration were the most significant factors on nickel extraction. While the first two factors had a positive effect, the latter one negatively affected the response. In order to selectively extract copper, the optimum range for the maximum extraction of copper with minimum nickel extraction was determined, which for any level of calcium concentration is an extractant concentration of 0.2–0.3 % (w/v), phase volume ratio of 2, and equilibrium pH of 2.5. Once copper ions were selectively removed from the process water, the optimum conditions for maximum nickel concentration were determined at three levels of calcium concentrations. Stripping experiments were also carried out, and the optimum acid concentrations of 10 and 5 g/L were determined for the stripping of copper and nickel, respectively.

An investigation into predispersed solvent extraction of nickel (II) ions from dilute aqueous solutions

Abstract This work investigated the extraction of nickel ions from dilute aqueous solutions using colloidal liquid aphrons. The effect of four experimental parameters (extractant concentration, phase volume ratio (PVR), water soluble surfactant concentration and equilibrium pH) on the extraction process at three different nickel concentrations was studied. Response surface method was used to determine the significance of various experimental parameters. The most significant factors were shown to be different for the various metal ion concentrations tested, which may have implication for industrial practice. The equilibrium pH of 5 was found to be optimum point for all concentrations studied. The recyclability of organic phase also shown through the reuse of stripped organic in a new extraction process. Reusing recycled organic in PDSE resulted in more than 99% nickel extraction, thus indicating the potential sustainability of a CLA-based extraction process.

AN APPLIED COMPARISON BETWEEN CONVENTIONAL PRE-DISPERSED SOLVENT EXTRACTION (PDSE) CONTACTORS AND NEW DISSOLVED NITROGEN PDSE (DNPDSE) ONES

Efforts to increase the mass transfer coefficient, enhance the contact area, and decrease the power input of contractors have given risen to the development of the pre-dispersed solvent extraction (PDSE) contactor and the devise of the new dissolved nitrogen PDSE (DNPDSE) contactors. The studies conducted after the design of the new contactor to determine the working conditions for its suitable performance (2.5-3.5 bar pressure, 0.1 L/min sparger flow rate, and 1.5 L of the aqueous phase) showed that for all the evaluated conditions (i.e. the pressure, polyaphron type, and dilution percentage), the recovery in the DNPDSE contactor was higher than that in the PDSE one. In addition, pictures of the performance modes of the two contactor indicated the presence of the organic phase in the form of colloidal gas aphrons (CGAs) in the DNPDSE contactor and of polyaphron aggregations in the PDSE one. This is a good reason for the increased copper recovery in the DNPDSE contactor. The best recovery for the extraction process in the DNPDSE contactor was achieved using the anionic polyaphron of sodium dodecylbenzene sulphonate (NaDBS) with five-fold dilution at 3.5 bar.

Copper ion removal from dilute solutions using colloidal liquid aphrons

The extraction of copper (II) from dilute aqueous solution by predispersed solvent extraction (PDSE) using colloidal liquid aphrons (CLAs) is described. The CLAs were made of LIX 984N as an extractant and an anionic, cationic, and nonionic surfactant. It was observed that the CLAs were in the micrometer size range, and that their size was controlled by the phase volume ratio. The phase volume ratio and extractant concentration in CLAs structure are the most effective parameters in this extraction process. CLAs were able to remove copper ions in less than one minute, and they remained stable for more than two months. The effect of surfactant type and concentration was also investigated, with the anionic surfactant found to produce the best results.

Continuous predispersed solvent extraction process for the downstream separation of 2,3-butanediol from fermentation broth

2,3-Butanediol (BDO) offers the possibility of expanding the list of value-added chemicals produced from the biorefinery platform. However, a major challenge and technical bottleneck for an efficient biological production in a large scale is the separation of BDO from the fermented broth system. The use of colloidal liquid aphrons (CLAs) in pre-dispersed solvent extraction (PDSE) is considered as an emerging technique for the recovery of bio-based compounds. Herein, we describe the application of an environment friendly PDSE system using CLAs for the recovery of (BDO). Continuous mode of countercurrent extraction employing CLAs is demonstrated for the extraction of synthetic as well as fermented BDO in a bubble column apparatus. For the first time, the use of centrifugal contactor (CCS) is established for the formation of stable CLAs. The optimum system parameters required for the CLA formation using CCS method were: 0.25wt% sodium dodecyl sulfate (SDS) as ionic surfactant, 0.5wt% Tween 80 as non-ionic surfactant in butanol–water system having a flow ratio of 2 with agitation of 2000rpm. Compared to the traditional liquid–liquid extraction (LLE) process, PDSE method provided 35–85% increase in mass transfer coefficient and about 30% reduction in overall solvent loading. In the presence of CLAs, the distribution coefficient (Kd) of BDO was found to be similar for all the concentrations of BDO. The results of this work open up the scope of PDSE–CLAs for the downstream processing of other biorefinery products.

New Dissolved Nitrogen Predispersed Solvent Extraction Method, 2: Selectivity

Dissolved Nitrogen Predispersed Solvent Extraction (DNPDSE) is a new method in which the two-phase mixture operation is based on bubble dispersion of the organic phase, instead of its drop dispersion into the aqueous phase. This substitution is intended to increase the two-phase contact area (to improve recovery of metal ions from the dilute solutions) and also to enhance the buoyancy force of organic phase (to improve separation of two phases). However, the performance mode of this method can increase the recovery of interfering elements, because of increased surface contact, entrainment, and precipitate flotation, and thus have an unfavorable effect on the selectivity of this method. Therefore, selectivity of this innovative method was compared with the conventional solvent extraction (SX) method. The results of experiments conducted on the dilute and dense copper, zinc, and iron synthetic solutions within the copper extraction pH values (1.2–2.1) showed a lack of zinc recovery (i.e., no effect on total selectivity) in both methods and increased iron recovery (i.e., effect on partial selectivity) only in the DNPDSE method. The results also showed that increased iron recovery was not just dependent on increased contact area of the two phases, and gel-like precipitates observed on the surface of organic phase indicated precipitation of Fe ions and their transfer onto the surface by bubble entrainment and precipitate flotation.

New Dissolved Nitrogen Predispersed Solvent Extraction Method, 1: Performance

The new Dissolved Nitrogen Predispersed Solvent Extraction (DNPDSE) method was invented for promoting the operational power and improving the equipment performance used in the conventional solvent extraction (SX) method, especially for dilute solutions. The main difference between this method and the SX method is in the mixing mode of aqueous and organic phases. The mixing operation in the SX method is performed with drop dispersion of one phase into another phase; however, in the DNPDSE method, it is carried out with bubble dispersion of organic phase into the aqueous phase. As a result, the performance of the method is improved due to the increase in the contact area of the two phases, thus enhancing in the buoyancy force of the organic phase. The performance comparison of the two methods in similar conditions showed that the copper recovery in the DNPDSE method compared with the SX method in dilute (128 mg Cu/L) and dense (2000 mg Cu/L) synthetic solutions was increased by 22% and 2.5% (on average), respectively.

Removal of chromium(III) from aqueous waste solution by predispersed solvent extraction

The extraction experiments of chromium(Ш) from aqueous waste solution by predispersed solvent extraction (PDSE) process with extractant (HEHPEHE) and its mixture, including acidic extractant (D2EHPA), alkaline extractant (TOA) and neutral extractant (TBP) were carried out respectively. It is found that the extractant HEHPEHE exhibited high extraction selectivity to chromium(III) from aqueous waste solution. The colloidal liquid aphrons (CLAs) were successfully generated using kerosene as a solvent, HEHPEHE as an extractant, sodium dodecyl benzene sulphate (SDBS) as a surfactant in aqueous phase and polyoxyethylene sorbitol anhydride monolaurate (Tween-20) in oil phase. To study the extraction efficiency and advantages of the PDSE process in the removal of chromium(Ш), the effects of major factors, such as initial chromium(Ш) concentration, volume of colloidal gas aphrons (CGAs), HEHPEHE volume fraction, phase ratio (solvent phase to water phase), mass fraction of dodecyl trimethylammonium bromide (HTAB), mass fraction of SDBS, mass fraction of Tween-20 and initial pH of aqueous waste solution were also investigated and the appropriate process conditions were obtained. Under the appropriate conditions, the extraction efficiency of chromium(III) above 99.9 % can be achieved and the treated aqueous waste solution can be discharged directly without polluting the environment.

Study on Mg2+ Removal from Ammonium Dihydrogen Phosphate Solution by Predispersed Solvent Extraction

The predispersed solvent extraction (PDSE) is a new method for separating solutes from aqueous solution, and for its high extraction ratio, the PDSE presents huge potential for the extraction from dilute solution. In the present paper, colloidal liquid aphrons are successfully generated using kerosene as a solvent, di(2-ethylhexyl)phosphoric acid (D2EHPA) as an extractant, sodium dodecyl benzene sulfate (SDBS) as surfactant in the aqueous phase, and polyoxyethylene sorbitol anhydride monolaurate (Tween-20) in oil phase. The extraction of Mg2+ from ammonium dihydrogen phosphate solution is studied by using colloidal liquid aphrons (CLA) and colloidal gas aphrons (CGA) in a semibatch extraction column. To study the extraction ratio and advantages of the PDSE process in the removal of Mg2+, various parameters, initial Mg2+ concentration, D2EHPA volume fraction, reaction temperature, phase volume ratio, mass fractions of dodecyl trimethylammonium bromide (HTAB), mass fractions of SDBS, mass fractions of Tween-20, and initial pH of NH4H2PO4 solution, are studied and optimized. The results show that Mg2+ in NH4H2PO4 solution can be effectively removed by the PDSE process. An extraction ratio of more than 86.3% is attained at the optimized parameters, and superior-grade NH4H2PO4 (MAP) can be obtained by two levels of extraction.

Predispersed solvent extraction of succinic acid aqueous solution by colloidal liquid aphrons in column

A study of the PDSE (predispersed solvent extraction) for succinic acid by colloidal liquid aphrons was conducted. The organic phase contaning TOA (tri-n-octylamine) and 1-octanol permits a selective extraction of succinic acid from its aqueous solution. There was no difference of the extractability of PDSE and that of conventional mixer-settler type extraction. Taking into account the no mechanical mixing in PDSE, it was concluded that the PDSE process is more adaptive than the conventional mixer-settler type extraction process. From mass transfer analysis at the various concentration of TOA in counter-current continuous operation, the concentration of TOA had no influence on the mass transfer coefficient. The loading values in continuous PDSE were almost same as those in batch operation.

Effect of salts on the extraction characteristics of succinic acid by predispersed solvent extraction

Predispersed solvent extraction (PDSE) of succinic acid with Tri-n-octylamine (TOA) dissolved in 1-octanol from aqueous solutions of 50 g/L succinic acid was examined. It was found that the equilibrium data in PDSE was equal to that in conventional solvent extraction in spite of the lack of mechanical mixing in PDSE. The influence of salts on succinic acid extraction and the stability of colloidal liquid aphrons (CLAs) were also investigated. Results indicated that in the presence of sodium chloride, less succinic acid was extracted by CLAs and the stability of CLAs decreased. However, the stability of CLAs was sufficient to make PDSE practically applicable to real fermentation broth, considering the concentration range of salts in the fermentation process for succinic acid.

Predispersed solvent extraction of negatively complexed copper from water using colloidal liquid aphron containing a quaternary ammonium salt

Negatively complexed copper ion by complexing agent like EDTA (Ethylenediaminetetraacteic acid) was removed by predispered solvent extraction (PDSE) using colloidal liquid aphrons (CLAs) made out of Trioctylmetylammonium chloride (Aliquat 336) diluted with nonpolar kerosene. PDSE was found to have higher mass transfer rate than conventional solvent extraction under experimental conditions without mechanical mixing. The effect of type of water-soluble surfactants, phase volume ratio (PVR), concentration of anionic Sodium Dodecyl Benzene Sulfonate (SDBS) on PDSE was investigated. In addition, the effect of anionic SDBS on back extraction in PDSE was also studied. Under experimental conditions with enough mechanical mixing, the amount of copper transferred to Aliquat 336 core from the pregnant phase was compared in both PDSE by using anionic SDBS and conventional solvent extraction. It is concluded that PDSE using Aliquat 336 CLA can be used for treatment of negatively complexed copper without the influence of surfactant. To optimize CLAs-based process, stability of CLAs containing a quaternary ammonium salt Aliquat 336 diluted with kerosene in the continuous phase was investigated by measuring the volume released to surface. To destabilize CLAs, H+, OIL were added. Stability of CLAs was estimated by comparing the half-life obtained. Break-up of destabilization follows pseudo-first-order reaction kinetics at low ionic strength. But, pseudo-first-order model cannot be applied to a region of high ionic strength.

Effect of ph on the extraction characteristics of succinic acid and the stability of colloidal liquid aphrons

Predispersed solvent extraction (PDSE) by colloidal liquid aphrons (CLAs) was used for the extraction of succinic acid from aqueous solution. The loading values for succinic acid in PDSE by CLAs increased with increasing pH values in aqueous phase. This was due to increasing of the concentration of the undissociated succinic acid. The extractability of PDSE was higher than that of conventional contacting type extraction because of the interaction between factant and acid molecule. The stability of CLAs increased with increasing of the pH values in aqueous phase and decreasing of trioctylamine (TOA) concentration in organic phase. However, the structure of CLAs was stable at all the pH range except very low pH condition.

Extraction of lactic acid with colloidal liquid aphrons and comparison of their toxicities with solvents without surfactant on the viability of Lactobacillus rhamnosus

Colloidal liquid aphrons (CLAs) are surfactant-stabilized solvent droplets which have recently been explored for predispersed solvent extraction (PDSE). We have compared the equilibrium distribution of lactic acid with solvent alone and with CLAs. In spite of the short contact time in the PDSE process with CLAs, there was little difference in equilibrium distribution with solvent alone. The toxicity of extractants and diluents on Lactobacillus rhamnosus was measured for in situ extraction. Long chain alcohols such as 1-octanol and 1-decanol were less toxic among diluents. CLAs reduced the toxicity of solvents on Lactobacillus rhamnosus.

Extraction of erythromycin-A using colloidal liquid aphrons: Part II. Mass transfer kinetics

An emerging technique for the recovery of microbial secondary metabolites, such as antibiotics, is the use of colloidal liquid aphrons (CLAs) in pre-dispersed solvent extraction (PDSE) processes. Knowledge of the extraction kinetics and the limiting mass transfer resistances will be vital for efficient process design and operation. In this work, the rates of erythromycin extraction using CLAs and conventional aqueous–organic, two-phase systems have been investigated. The CLAs used were formulated from 1% w/v Softanol 120 in decanol and 0.5% w/v SDS in water. The rate of erythromycin extraction with CLAs dispersed in well-mixed systems was found to be extremely rapid with equilibrium being achieved within 15 s or less. Overall erythromycin mass transfer coefficients, K o , were typically 6.3×10 −6 m s −1 for extraction experiments, and 1.0×10 −6 m s −1 for stripping experiments. The rapid rates of erythromycin transfer were attributed to the small size of the dispersed CLAs, typically 5 μm diameter, and hence the large interfacial area available for mass transfer of around 15×10 3 m 2 m −3 . Experiments over a range of Reynolds numbers indicated that both the extraction and stripping processes were probably under mixed control of an interfacial resistance and boundary-layer diffusion. To investigate the influence of the surfactants used for aphron formulation on erythromycin extraction, further experiments were performed using aqueous–organic, two-phase systems in a non-dispersive stirred cell. The measured K o values were of the same order of magnitude as in the case of experiments with dispersed CLAs. When present individually, or together with SDS, the non-ionic Softanol surfactant was seen to retard erythromycin extraction rates in all cases. In contrast, the presence of SDS was found to enhance K o values by a factor of 2–4 compared to surfactant-free systems. This may be attributed to a specific interaction between individual SDS and erythromycin molecules and/or the generation of interfacial turbulence at a microscopic level. Further investigations are underway to elucidate the mechanism responsible. The concentration of either surfactant was also found to significantly affect the measured K o values. The prediction of K o values using existing correlations, and the implications of the experimental results on contactor design and operation are also discussed.

Removal of an Organic Dye from Water Using a Predispersed Solvent Extraction

The removal of Solvent Yellow 1 in a range from 0.25 to 10 ppm by weight from an aqueous solution using a predispersed solvent extraction (PDSE) was investigated and compared with conventional solvent extractions in batch mode. Colloidal liquid aphrons (CLAs) made out of kerosene were used as a predispersed organic solvent. To form CLAs, Tergitol 15-S-3 and sodium dodecylbenzene sulfonate were used as oil-soluble and water-soluble surfactants, respectively. The ratio of solvent volume to pregnant solution volume was less than 0.025. The efficiency of the extraction with CLAs can be higher than that of a single-staged conventional extraction process with a shorter contact time. The recovery of used CLAs with a colloidal gas aphrons (CGAs) flotation was measured using different surfactants. CLAs with an extremely large surface area can also reduce processing time and energy cost. PDSE is therefore a promising process for the removal of organic materials from water.

Extraction of erythromycin-A using colloidal liquid aphrons: I. Equilibrium partitioning

Colloidal liquid aphrons (CLAs) are surfactant-stabilised solvent droplets which have recently been explored for use in pre-dispersed solvent extraction (PDSE). In this work, the equilibrium partitioning of a microbial secondary metabolite, erythromycin, has been studied using both CLAs (formulated from 1% (w/v) Softanol 120 in decanol and 0.5% (w/v) SDS in water) and surfactant-containing, two-phase systems. The equilibrium partitioning of erythromycin was found to be strongly influenced by the extraction pH, and exhibited a marked change either side of the pKa of the molecule. A modified form of the Henderson–Hasselbach equation could be used as a simple design equation to predict the equilibrium partition coefficient (meryt = Corg /Caq) as a function of pH. For extraction experiments with dispersed CLAs where pH > pKa, meryt values as high as 150 could be obtained and the erythromycin could be concentrated by factors of up to 100. Experiments were also carried out in surfactant-containing, two-phase systems to determine the effect of individual surfactants used for aphron formulation on erythromycin partitioning. For extraction at pH 10 neither the Softanol (a non-ionic surfactant) nor SDS (an anionic surfactant) had any influence on the equilibrium erythromycin partition coefficients. For stripping at pH 7, however, it was found that recovery of erythromycin from the organic phase decreased with increasing concentration of SDS, although again the Softanol had no influence on the equilibrium. The effect of SDS was attributed to a specific electrostatic interaction between individual erythromycin and SDS molecules under stripping conditions. The meryt values and concentration factors achievable in the two-phase systems were considerably less than those for the PDSE experiments. The physical properties of the two-phase systems, ie density, viscosity, interfacial tension, etc, and the equilibrium distribution of the surfactants were also determined in relation to subsequent studies on the kinetics of erythromycin extraction. © 2000 Society of Chemical Industry

The influence of system parameters on the stability of colloidal liquid aphrons

An investigation was carried out on the effect of process parameters involved in Pre-Dispersed Solvent Extraction (PDSE) on the stability and interactions in dilute dispersions of Colloidal Liquid Aphrons (CLAs). The aim of this work was to derive empirically-based engineering relationships that could be used in the design of PDSE processes. For this investigation, CLAs were formulated with an Aliquat 336/n-octanol/Softanol 120 solvent phase, and a Synperonic A20 aqueous phase. These CLAs were intended for use in the reactive pre-dispersed solvent extraction of polar solutes such as phenylalanine. Light scattering measurements over a range of continuous aqueous and CLA phase conditions were used as a method of obtaining a measure of the rate of disappearance of CLAs from dispersion (a measure of stability), and a comparison of stability under different conditions. Two forms of CLA interaction occurring by independent mechanisms were identified – CLA break-up, and CLA flocculation. Break-up was found to be a first order process, allowing CLA stability to be characterised by a first order half-life (typical half-life 15–40 min). This was proposed to occur on collision of CLAs with sufficient energy to overcome the stabilising forces provided by the surfactants at the interfaces of the CLAs. It was shown that flocculation occurred at high ionic strengths (>0.1 M NaCl), and that it was not part of the break-up mechanism. An apparent size dependent CLA half-life was proposed to be due to smaller particles having a lower collision energy on average. The data suggested that the resistance to CLA break-up was not charge repulsion, but derived from an interaction between molecules of one of the surfactants making up the aqueous ‘shell’ of the CLAs (Synperonic A20). Finally, the basis for a semi-empirical design equation for prediction of CLA half-life developed from the Arrhenius equation was proposed. © 1999 Society of Chemical Industry

The influence of system parameters on the stability of colloidal liquid aphrons

An investigation was carried out on the effect of process parameters involved in Pre-Dispersed Solvent Extraction (PDSE) on the stability and interactions in dilute dispersions of Colloidal Liquid Aphrons (CLAs). The aim of this work was to derive empirically-based engineering relationships that could be used in the design of PDSE processes. For this investigation, CLAs were formulated with an Aliquat 336/n-octanol/Softanol 120 solvent phase, and a Synperonic A20 aqueous phase. These CLAs were intended for use in the reactive pre-dispersed solvent extraction of polar solutes such as phenylalanine. Light scattering measurements over a range of continuous aqueous and CLA phase conditions were used as a method of obtaining a measure of the rate of disappearance of CLAs from dispersion (a measure of stability), and a comparison of stability under different conditions. Two forms of CLA interaction occurring by independent mechanisms were identified – CLA break-up, and CLA flocculation. Break-up was found to be a first order process, allowing CLA stability to be characterised by a first order half-life (typical half-life 15–40 min). This was proposed to occur on collision of CLAs with sufficient energy to overcome the stabilising forces provided by the surfactants at the interfaces of the CLAs. It was shown that flocculation occurred at high ionic strengths (>0.1 M NaCl), and that it was not part of the break-up mechanism. An apparent size dependent CLA half-life was proposed to be due to smaller particles having a lower collision energy on average. The data suggested that the resistance to CLA break-up was not charge repulsion, but derived from an interaction between molecules of one of the surfactants making up the aqueous ‘shell’ of the CLAs (Synperonic A20). Finally, the basis for a semi-empirical design equation for prediction of CLA half-life developed from the Arrhenius equation was proposed. © 1999 Society of Chemical Industry

Studies in Solvent Extraction Using Polyaphrons. II. Semibatch and Continuous Countercurrent Extraction/Flotation of a Hydrophobic Organic Dye from Water

Abstract Transport mechanisms and a mathematical model for a continuous, countercurrent predispersed solvent extraction (PDSE) process are proposed in this paper. Solvent extraction using polyaphrons provides enhanced mass transfer (extraction) of solute through larger interfacial areas of micron-sized predispersed solvent. Increased rise velocity is needed for subsequent phase separation (flotation) of dispersed polyaphrons through attachment onto micron-sized gas dispersions called colloidal gas aphrons (CGAs). PDSE experiments were conducted in both batch and continuous countercurrent modes to remove a hydrophobic organic dye (Solvent Red 27) from water into kerosene. Sodium dodecylbenzenesulfonate was used as the water-soluble surfactant and Tergitol-15-S-3 as the kerosene-soluble surfactant to form polyaphrons. The CGAs were prepared using hexadecyltrimethyl ammonium bromide in water. Results from batch experiments showed that the efficiency of dye removal depended not only on the duration of flotati...