ELECTROPHORETIC MOBILITY OF OIL DROPS IN THE PRESENCE OF SOLVENT EXTRACTION REAGENTS

Abstract

The electrophoretic mobility (EM) of hexane and toluene droplets dispersed in aqueous solution has been investigated as a function of pH in the presence and absence of 5,8-diethyl–7–hydroxy–6–dodecanone oxime (the active extractant in the Henkel reagent, LIX63), Dinonylnaphthalene sulfonic acid (HDNNS), di(2-ethylhexyl) phosphoric acid (HDEHP) and tricaprylyl methyl ammonium chloride (Aliquat 336). Both hexane and toluene droplets were found to be negatively charged at pH > 3, with the absolute EM increasing with pH; the toluene droplets were more negatively charged than the hexane droplets. The hydroxyoxime reagent had no significant effect on the EM, whereas the addition of HDNNS and HDEHP dramatically enhanced the negative charge at the organic/ water interface. In the presence of 1·5 × 10^?4 kmol m^?3 Aliquat 336, the organic drops became less negatively charged and eventually acquired a positive charge at pH < 9. The results are explained In terms of the preferential adsorption of the aqueous phase hydroxyl ions and the polar groups of the various extractants at the organic/water interface.     

Studies on Micellar Behavior of PEO‐PBO or PEO‐PBO‐PEO Copolymers,or Surface Active Amphiphilic Ionic Liquids in Aqueous Media and Exploration of the Micellar Solutions for Solubilization of Dexamethasone and its Delayed Release

The aggregation behavior of a di‐ and tri‐block copolymers of type PEO‐PBO, PEO‐PBO‐PEO, surface‐active ionic liquid (SAIL) of type 4‐dodecyl‐4‐methylmorpholinium chloride [C₁₂mmor][Cl], and 1‐dodecyl‐1‐methylpyrrolidinium chloride [C₁₂mpyrr][Cl]) in water as well as in 10 mM of a poorly water soluble dexamethasone (dex) aqueous solution was studied by determining the critical micelle concentrations using drug solubilization, surface tension, and isothermal titration calorimetry (ITC) methods. ITC measurements were also made on solutions prepared by mixing the micellar aqueous solutions of copolymers and simple aqueous solutions of SAIL across the mole fractions at three different temperatures (298.15, 308.15, and 318.15 K). The thermodynamic parameters, namely Gibbs free energy (ΔG_m), enthalpy (ΔH_m), and entropy (ΔS_m), of micellization were calculated, and it was observed that the negative ΔG_m and positive ΔS_m for the mixture solutions increase with the increase in mole fraction of SAIL. Otherwise, the micellization is reported to be a spontaneous and highly entropy‐driven process. The dex‐solubilized micellar solutions were mixed with agar to obtain standing gels. The gel samples were dry‐cast into thin films, and the release of dex from films by simple dilution was monitored by UV measurements. The drug release data was fitted to several mechanistic models, and it was inferred that the release mechanism for dex from thin films is non‐Fickian for mixtures and Fickian in copolymer or SAIL micellar aqueous solutions. The transport of dex is diffusion‐controlled with diffusivities of 5.8–12 × 10^?11 m² s^?1 for copolymer micelles, 5–11 × 10^?11 m² s^?1 for micelles of SAIL, and 3–14 × 10^?11 m² s^?1 for the mixed micelles of copolymer and SAIL in aqueous media.     

Reaction kinetics of 2‐((2‐aminoethyl) amino) ethanol in aqueous and non‐aqueous solutions using the stopped‐flow technique

Observed pseudo‐first‐order rate constants (k_o) for the reaction between CO₂ and 2‐((2‐aminoethyl) amino) ethanol (AEEA) were measured using the stopped‐flow technique in an aqueous system at 298, 303, 308 and 313 K, and in non‐aqueous systems of methanol and ethanol at 293, 298, 303 and 308 K. Alkanolamine concentrations ranged from 9.93 to 80.29 mol m^?3 for the aqueous system, 29.99–88.3 mol m^?3 for methanol and 44.17–99.28 mol m^?3 for ethanol. Experimentally obtained rate constants were correlated with two mechanisms. For both the aqueous‐ and non‐aqueous‐AEEA systems, the zwitterion mechanism with a fast deprotonation step correlated the data well as assessed by the reported statistical analysis. As expected, the reaction rate of CO₂ in the aqueous‐AEEA system was found to be much faster than in methanol or ethanol. Compared to other promising amines and diamines studied using the stopped‐flow apparatus, the pseudo‐first‐order reaction rate constants were found to obey the following order: PZ (cyclic‐diamine) > EDA (diamine) > AEEA (diamine) > 3‐AP (primary amine) > MEA (primary amine) > EEA (primary amine) > MO (cyclic‐amine). The reaction rate constant of CO₂ in aqueous‐AEEA was double that in aqueous‐MEA, and the difference increased with an increase in concentration. All reaction orders were practically unity. With a higher capacity for carbon dioxide and a higher reaction rate, AEEA could have been a good substitute to MEA if not for its high thermal degradation. AEEA kinetic behaviour is still of interest as a degradation product of MEA. © 2012 Canadian Society for Chemical Engineering     

Modelling of Cr(VI) removal from polluted groundwaters by ion exchange

This work reports the viability and modelling of the removal of Cr(VI) from polluted groundwaters by means of ion exchange using the resin Lewatit MP‐64. Feed groundwaters that contained Cr(VI) at an average concentration of 2431 mg dm^?3 and 1187 mg dm^?3 of chloride and 1735 mg dm^?3 of sulfate as main anions were acidified to a pH of 2.0 prior to the removal process. Dynamic experiments were carried out in a fixed bed column with feed waters at flow rates in the range of 2.78 × 10^?7 m³ s^?1 to 5.55 × 10^?7 m³ s^?1. Regeneration was achieved with NaOH (2 mol dm^?3). From the experimental results, the equilibrium of the ion exchange reaction was successfully modelled, obtaining an equilibrium constant (K′_AB) = 44.90. Finally, a mass balance that included mass transfer resistances in the liquid and solid phases was developed and from the comparison between simulated and experimental data the value of the effective intraparticle diffusivity (D_s) was determined as 1.43 × 10^?12 m² s^?1. Copyright © 2004 Society of Chemical Industry     

Separation of phenylacetic acid using tri-n-butyl phosphate in hexanol: Equilibrium and kinetics

Equilibrium and kinetics studies are required to design the continuous extraction process for the acid-extraction system. In the present study, an attempt has been made to investigate the equilibrium and kinetics parameters for the reactive extraction of phenylacetic acid (PAA) with tri-n-butyl phosphate (TBP) in hexanol. The equilibrium results show that the formation of the (1:1) PAA–TBP complex in the organic phase with an overall equilibrium complexation constant (K_e) was 78.74 and 29.15 m³.kmol^?1 for TBP concentrations of 0.734 and 1.464 kmol.m^?3, respectively. The mass transfer coefficients (k_L) for PAA were found to be in the range of 3.7 × 10^–5–6.2 × 10^–5 m.s^?1. Based on the Hatta number (H_a = 8.48), the reaction was found to be fast chemical reaction (regime 3) with the order of reaction as 0.77 and 0.36 with respect to PAA and TBP, respectively. The rate constant of the reaction was obtained as 0.017 kmol.m^?3.s^?1.     

Equilibria and Kinetics of Extraction of Citric Acid from Aqueous Solutions in Alamine 336–Cyclohexanone System

Abstract

Equilibria and kinetics for the extraction of citric acid by Alamine 336 in cyclohexanone as diluent are reported. The theory of extraction accompanied by a chemical reaction has been used to obtain the intrinsic kinetics of extraction of citric acid by Alamine 336 in cyclohexanone. The reaction has been found to be first order in both Alamine 336 and citric acid with a rate constant of 8.8×10^?3 m³ kmol^?1 s^?1.     

Electrical conduction mechanism in plasma polymerized 2‐(diethylamino)ethyl methacrylate thin films

Thin films of different thicknesses were prepared through glow discharge of 2‐(diethylamino)ethyl methacrylate (DEAEMA) using a capacitively coupled reactor. Current density–voltage (J–V) characteristics for plasma polymerized (PP) DEAEMA thin films of thicknesses 100, 200, 250, and 300 nm in aluminum/PPDEAEMA/aluminum sandwich configuration were studied over the temperature range from 298 to 423 K. J–V curves reveal that in the low‐voltage region, the conduction current obeys Ohm's law while in the high‐voltage region the behavior attributed to be space charge‐limited conduction in PPDEAEMA thin films. The carrier mobility was calculated to be about 6.80 × 10^?19 to 2.38 × 10^?18 m^?2 V^?1s^?1 for various thicknesses. The free carrier density was found to be about 1.78 × 10²³ to 2.04 × 10²³ m^?3, and the trap density was found to be about 6.93 × 10²³ to 15.9 × 10²³ m^?3 for different thicknesses. The activation energies were estimated to be about 0.005–0.016 eV for 2 and 30 V of PPDEAEMA thin films of different thicknesses. The low‐activation energies indicate that the thermally activated hopping conduction is operative in PPDEAEMA thin films. POLYM. ENG. SCI., 55:2729–2734, 2015. © 2015 Society of Plastics Engineers     

Equilibria,Kinetics, and Modeling of Extraction of Citric Acid from Aqueous Solutions with Alamine 336 in 1-Octanol

Experimental equilibrium and kinetic data on the extraction of citric acid from aqueous solutions using Alamine 336 in 1-octanol have been determined. The distribution coefficient has increased from 0.029 to 71.727 with increase of Alamine 336 concentration from 0 to 30% (v/v). The chemical equilibria was interpreted as a result of consecutive formation of acid-amine species with 1:1 stoichiometry and the equilibrium complexation constant, K _E1 , has been estimated as 20.186 m³ kmol^?1. The mass-transfer coefficients of citric acid, Alamine 336, and 1:1 acid-alamine complex in 1-octanol were calculated from acetic acid mass-transfer coefficient, which was determined by measuring its fluxes of simple diffusion from kerosene to water. Based on the Hatta number and the criterion given by Doraiswamy and Sharma, the reaction regime has been found to be instantaneous reaction regime occurring at the interface on the organic phase side. An extraction model comprising 1:1 equilibrium complextion constant, K _E1 , and complex mass-transfer coefficient, k _BA (3.79 × 10^?6 m s^?1), has been developed, and it explained the present system satisfactorily.     

Removal of anionic pollutants from groundwaters using Alamine 336: chemical equilibrium modelling

This work reports the study of the chemical equilibrium of the extraction of chromium(VI) anions from groundwaters where other anionic species are present, mainly sulfate and chloride anions, using Alamine 336 as extractant. The analysis was performed working with two different systems: (i) a binary system (sulfate and chloride anions) and, (ii) a tertiary system (chromium, sulfate and chloride anions) with a composition of 9.6–15.4 mol Cr⁶⁺ m^?3, 5.2–16.7 mol SO₄^2? m^?3 and 4.2–13.5 mol Cl^? m^?3 respectively. A careful experimental design was performed and the data were correlated to the mathematical models obtaining the equilibrium parameters of the extraction reactions in both systems. Copyright © 2006 Society of Chemical Industry     

Kinetic study on biphasic recognition chiral extraction for separation of α‐cyclohexyl‐mandelic acid enantiomers

BACKGROUND: Chiral solvent extraction is a potentially attractive chiral separation technique. It is essential to know the intrinsic complexation kinetics for selection, design and operation of reactive extraction equipment and for reliable scale‐up. The objective of this research is to study the kinetics of biphasic recognition chiral extraction of α‐cyclohexyl‐mandelic acid (α‐CHMA) enantiomers using a modified Lewis cell. RESULTS: The experimental results demonstrate that the extraction reaction kinetics is fast, and the reactions are first order with respect to α‐CHMA and second order with respect to D‐IBTA, with forward rate constants of 6.54 × 10^?4 mol^?2 m⁶ s^?1 for S‐α‐CHMA and 6.84 × 10^?4 mol^?2 m⁶ s^?1 for R‐α‐CHMA. With increase of HP‐β‐CD concentration in aqueous phase, enantioselectivity increases, while the overall mass transfer coefficients decrease. CONCLUSIONS: Sufficient enantioselectivity and fast kinetics of extraction can be obtained in the BRCE system at HP‐β‐CD concentration of 0.1 mol L^?1 and D‐IBTA concentration of 0.2 mol L^?1. These data will be useful in the design of extraction processes. Copyright © 2012 Society of Chemical Industry     

The extraction of platinum from Pt(II) chloride solution by a quaternary ammonium compound

The fundamental aspects of the extraction and stripping of platinum (II) from its chloride solution by Aliquat 336 diluted with toluene have been studied. The extraction and stripping was at 99.5 and 97.6% equilibrium within 30 s and 20 min respectively. The percentage extraction increased slightly with decreasing hydrochloric acid concentration. In 0.1 mol dm^?3 hydrochloric acid, 1.0 volume percent Aliquat 336 in toluene could load 9.8 mmol dm^?3 of platinum (II). The percentage stripping of platinum (II) from Pt(II)-load organic solvent increased with increasing sodium bisulphite concentration. The enthalpy changes of extraction and of stripping were 12.8 and 114.9 kJ mol^?1 respectively. Both of the reactions were endothermic.     

Synthesis of a new rhodamine‐containing block copolymer for highly selective and sensitive detection of Cu2+ and CN− ions in aqueous media

Development of new chemosensors that are selective and sensitive to Cu²⁺ and CN^? ions, especially in aqueous media, is of tremendous importance. We report the synthesis of a new block copolymer that is capable of highly selective and sensitive detection of Cu²⁺ and CN^? ions in aqueous media. Poly(t‐butylacrylate)‐block‐poly(3‐bromopropylacrylate) was prepared using the reversible addition–fragmentation chain transfer polymerization technique. This block copolymer was reacted with 2,4‐dihydroxybenzaldehyde followed by reaction with rhodamine B hydrazide for successful incorporation of the desired rhodamine units into the block copolymer structure. Cu²⁺‐induced opening of the spirolactam ring of the rhodamine units resulted in rapid and easily noticeable colour change, thus enabling a highly selective detection of Cu²⁺ ions in aqueous media for concentrations as low as 2 µmol L^?1. We further demonstrate that this Cu²⁺ bound polymer complex can further act as a selective and sensitive sensing platform for CN^? in aqueous media with concentrations <1 µmol L^?1 (0.06 ppm). Moreover, the polymer can also be used to remove Cu²⁺ from aqueous media. © 2014 Society of Chemical Industry     

Rates of acetate extraction from simulated waste streams in chloromycetin production

The kinetics for extraction recovery of acetate ions from simulated waste streams in chloromycetin production by Aliquat 336 (a quaternary amine) and tri‐n‐butylphosphate (TBP) in xylene were examined using a microporous membrane‐based stirred cell. The waste stream typically contained 15.4% acetic acid, 8.8% sodium acetate, and 4.7% (w/w) NaCl. The stirred cell could give intrinsic rates for formation of the complex occurring at or near the organic–aqueous interface. It was shown that the extraction rate with TBP was higher than that with Aliquat 336. The effect of temperature (288–318 K) on the reaction rate with TBP was also examined and the activation energy (54.5 kJ mol⁻¹) was obtained. © 1999 Society of Chemical Industry     

Ion‐exchange adsorption of calcium ions from water and geothermal water with modified zeolite A

The modified zeolite A was prepared by a two‐step crystallization method to remove scale‐forming cations from water and geothermal water. The adsorption kinetics, mechanism and thermodynamics were studied. The calcium ion adsorption capacity of the modified zeolite A was 129.3 mg/g (1 mg/g = 10^?3 kg/kg) at 298 K. The adsorption rate was fitted well with pseudo‐second‐order rate model. The adsorption process was controlled by film diffusion at the calcium ion concentration less than 250 mg/L (1 mg/L = 10^?3 kg/m³), and it was controlled by intraparticle diffusion at the concentration larger than 250 mg/L. The calculated mass‐transfer coefficient ranged from 2.23 × 10^?5 to 2.80 × 10^?4cm/s (1 cm/s = 10^?2m/s). Dubinin–Astakhov isotherm model could appropriately describe the adsorption thermodynamic properties when combined with Langmuir model. The adsorption process included not only ion exchange but also complexation between calcium and hydroxyl ions. The adsorption was spontaneous and endothermal. The high adsorption capacity indicates that the modified zeolite A is a suitable adsorption material for scale removal from aqueous solution. © 2014 American Institute of Chemical Engineers AIChE J, 61: 640–654, 2015     

One pot synthesis of xanthan gum‐g‐N‐vinyl‐2‐pyrrolidone and study of their metal ion sorption behavior and water swelling property

In this article, graft copolymerization of N‐vinyl‐2‐pyrrolidone onto xanthan gum initiated by potassium peroxydiphosphate/Ag⁺ system in an aqueous medium has been studied under oxygen free nitrogen atmosphere. Grafting ratio, grafting efficiency, and add on increase on increasing the concentration of potassium peroxydiphosphate (2.0 × 10^?3 to 12 × 10^?3 mol dm^?3), Ag⁺(0.4 × 10^?3 to 2.8 × 10^?3 mol dm^?3), and hydrogen ion concentration from 2 × 10^?3 to 14.0 × 10^?3 mol dm^?3. Maximum grafting has been obtained when xanthan gum and monomer concentration were 0.4 g dm^?3 and 16 × 10^?2 mol dm^?3, respectively, at 35°C and 120 min. Water swelling capacity, swelling ratio, metal ion uptake, and metal retention capacity have also been studied, and it has been found that graft copolymer shows enhancement in these properties than pure xanthan gum. The graft copolymer has been characterized by FTIR and thermal analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Equilibria and kinetics for reactive extraction of lactic acid using Alamine 336 in decanol

Lactic acid is an important commercial product and extracting this from aqueous solution is a growing requirement in fermentation‐based industries. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid–amine (solvent) system used. The equilibrium complexation constants for ratios of (1:1) and (2:1) have been estimated. The kinetics of extraction of lactic acid by Alamine 336 in decanol has also been determined. The reaction between lactic acid and Alamine 336 in decanol in a stirred cell falls in Regime 3, ie extraction accompanied by a fast chemical reaction occurring in the diffusion film. The reaction has been found to be zero order in Alamine 336 and first order in lactic acid with a rate constant of 0.21 s^?1. These data will be useful in the design of extraction processes. © 2002 Society of Chemical Industry     

Preparation and coordination behavior of cellulose beads derivative modified by 1,5‐diaminoethyl‐3‐hydroxy‐1,5‐diazacycloheptane

Cellulose derivative (MPCN) modified by 1,5‐diaminoethyl‐3‐hydroxy‐1,5‐diazacycloheptane (DADN) was prepared and characterized by scanning electron microscopy and elemental, and infrared analysis. MPCN and its Cu²⁺, Pb²⁺ complexes were characterized by thermogravimetric and differential thermal analysis. The coordination adsorption behavior of MPCN with divalent copper and lead ions was determined. The effects of temperature, initial pH value, and the concentration of MPCN ligand to the equilibrium adsorption were discussed. The optimum pH range of the coordination adsorption of MPCN with Cu²⁺ and Pb²⁺ is 5–6. The rate constants of the coordination reaction were found. At 323 K, the rate constant is 1.0 × 10⁻³ and 7.0 × 10⁻⁴ s⁻¹ for Cu²⁺ and Pb²⁺, respectively. The thermodynamic parameters of the coordination reaction were obtained based on the experiment data of the adsorption isotherms. The coordination reaction was performed spontaneously from the data of ΔG, as follows: −21.65 and −19.41 kJ/mol and ΔS, 87.06 and 67.92 J/mol K for Cu²⁺ and Pb²⁺, respectively. The coordination ratio of DADN coordination group immobilized on cellulose beads with either metal ion is about 1 : 2 from the plot of the relation of lgD versus lgL and the capacity of saturation adsorption. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1278–1285, 1999     

Aqueous dispersion polymerization of acrylamide with quaternary ammonium cationic comonomer

Using aqueous solution of ammonium sulfate as medium, acrylamide (AM) and dimethylaminoethyl methacrylate methyl chloride (DMC) as main raw materials, poly(dimethylaminoethyl methacrylate methyl chloride) (PDMC) as stabilizer and 2,2′‐azobis (2‐amidinopropane) dihydrochloride (V‐50) as initiator, the cationic polyelectrolyte of P(DMC‐AM) was synthesized by aqueous dispersion polymerization. The effects of the major reaction variables on synthesis conditions, product characteristics (particle size and molecular weight), and polymerization rate were investigated. The polymerization was retarded by the presence of the ammonium sulfate. The optimum reaction conditions for obtaining a stable aqueous dispersion were concentrations of 1.8 × 10^?4–7.0 × 10^?4 mol L^?1 for V‐50, 1.5–3.5% for stabilizer, and 23.2–30.0% for salt. The molecular weight of PDMC formed was 1.5 × 10⁵ to 7.0 × 10⁵. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Liquid membrane transport and separation of Zn2+ and Cd2+ from sulfate media using organophosphorus acids as mobile carriers

The transport and separation of Zn²⁺ and Cd²⁺ from binary sulfate solutions in a supported liquid membrane using di(2‐ethylhexyl)phosphoric acid (D2EHPA) and 2‐ethylhexylphosphonic acid mono‐2‐ethylhexyl ester (PC88A) as mobile carriers was studied. Batch solvent extraction experiments were conducted to obtain the reaction stoichiometries. Experiments were performed at different metal concentrations (1.4–14.5 mol m^?3), metal concentration ratios (0.4–9.2), pH (2–5), and carrier concentrations (0.1–0.6 mol dm^?3). A mass transfer model was proposed that considers diffusion in the aqueous feed and strip stagnant layers, and within the membrane. The interfacial reactions were assumed to approach equilibrium instantaneously. It was shown that the proposed model was applicable for binary Zn²⁺/Cd²⁺ systems (standard deviation, 5%). The larger separation factors of Zn²⁺ over Cd²⁺ with PC88A than D2EHPA under equilibrium (batch solvent extraction) and non‐equilibrium (liquid membrane) conditions were also evaluated and discussed. Copyright © 2003 Society of Chemical Industry     

Extraction rates of amino acids by an emulsion liquid membrane with tri-n-octylmethylammonium chloride

The extraction rates of amino acids from alkaline aqueous solution into an emulsion liquid membrane containing tri-n-octylmethylammonium chloride as a carrier and Paranox 100 as an emulsifier were measured using a stirred transfer cell. The effects of agitation speed (0·33–0·66 rev s⁻¹), amino acid concentrations (0·5–50 mol m⁻³) and temperature (10–45°C) on the extraction rates were examined. The results were analyzed by a double-film model. The mass transfer coefficients of amino acids (0·26–1·58×10⁻⁵ m s⁻¹) and their complexes (0·60–1·72×10⁻⁵ m s⁻¹) were found to correlate well with the hydrophobicities of the amino acids. It was found that the surfactant layer influenced the mass transfer processes of both amino acids in the aqueous film and their complexes in the organic film. The permeation of amino acids with a large hydrophobicity through the emulsion liquid membrane was promoted by both high distribution and larger mass transfer rates. © 1998 Society of Chemical Industry