Lewis-type Cell Research Articles

Kinetics of Liquid/Liquid Extraction of Europium(III) Cation by Two Malonic Diamides

In the framework of the DIAMEX separation process, the kinetics of extraction of Eu(III) ion by two diamides, DMDBTDMA and DMDOHEMA, have been studied using the rotating membrane cell technique. The kinetics with DMDBTDMA from a nitric acid solution were found to be very fast, in keeping with a previous work using the Nitsch cell, and in disagreement with another work using a Lewis-type cell. A simple model for turbulent transport in the latter cell is proposed to interpret this result. The extraction kinetics with DMDOHEMA was found to be slower than with DMDBTDMA at 22°C. The activation energy of the interfacial reaction was deduced from experiments at 11°C, 22°C, and 33°C. The activation energy of the distribution ratio is shown to have a particular effect on that of the overall kinetic rate constant in the general case.

Relationship Between pH and Carbonation Ratio to Measure CO2 Capture Efficiency by NH3 Solvent

This paper presents an established relationship between the pH of ammonia solution and its carbonation ratio (α). The aim of this correlation is to track the amount of CO2 absorbed or the amount of CO2 released from ammonia solvent. Furthermore, this paper studies the evolution of density and viscosity of ammonia solution with the carbonation ratio because those physical properties can significantly affect liquid side mass transfer coefficient. Experiments have been carried out in a thermoregulated Lewis-type cell reactor and the measures have been done using three concentrations of ammonia (3, 5 and 7 wt %) and temperatures (293, 303 and 313 K). Results show that the estimated function has a high correlation coefficient which indicates a relationship between variables. All results show a linear correlation between viscosity and carbonation ratio, and between density and carbonation ratio.

Measurement and Calculation for CO2 Solubility and Kinetic Rate in Aqueous Solutions of Two Tertiary Amines

Absorbing CO2 with amine solutions is one of the most promising methods of CCS and has been widely applied. In order to improve efficiency and reduce costs, new solvents need to be selected. In this work, two amine solvents, N,N-dimethylethanolamine(DMEA) and Triethylene diamine (TEDA), have been characterized, with the use of gas- liquid reactor for CO2 solubility and kinetic rate measurements. Solubility of CO2 has been measured for amine concentrations of 1.0, 2.5 and 4.0mol/L at temperatures of 313.2K, 343.2K, 373.2K, and 393.2K while partial pressure of CO2 varies from 1 to 300kPa. The e-NRTL model has been used for these amine-water-CO2 systems in order to calculate CO2 solubility. Meanwhile the thermo-regulated constant interfacial area Lewis-type cell was also operated to obtain absorption kinetic data for CO2 absorption in 0.5M and 1.0M amine solutions.

Synthesis and characterization of neodymium phosphate powder resulted from neodymium loaded-HDEHP organic solutions by a stripping–precipitation process using a Lewis type cell

The solvent extraction process of neodymium(III) from aqueous solution by di(2-ethylhexyl) phosphoric acid (HDEHP) in kerosene has been performed as a first step to accomplish the homogeneous precipitation of neodymium phosphate by stripping from an organic metal loaded HDEHP solution using phosphoric acid solutions. In this study, stripping–precipitation approach was proposed to synthesize powders of neodymium phosphate using a modified Lewis cell. The effects of extractant, organic phase, neodymium concentration, stripping phase, phosphoric acid content and temperature were separately investigated. The neodymium precipitate was characterized by X-ray diffractometry, scanning electron microscopy, particle size measurement, thermogravimetric analysis and infrared spectroscopy. The results showed that the powder precipitated with 3 M H 3PO 4 showed more regular and slightly larger particles than those obtained by 5 M H 3PO 4 while the precipitate with 8 M H 3PO 4 gave highly agglomerated particles. Increasing the HDEHP concentration from 0.25 M to 0.75 M gave an increase of the particle size of the precipitate. As the temperature increases (10–45 °C), the formed particles appeared to be more crystalline and smaller in size.

Comparison of absorption rates and absorption capacity of ammonia solvents with MEA and MDEA aqueous blends for CO2 capture

In this work we present the experimental results of absorption rates and absorption capacity for the CO2 absorption by ammonia (NH3) aqueous solutions. Experiments are carried out in a thermoregulated Lewis-type cell reactor and are achieved in temperature and concentration ranges of 278–303K and 2–5wt.% NH3 respectively. The obtained values for absorption kinetic rates and absorption capacity are compared with those available for alkanolamine solvents, commonly used to absorb CO2. In order to achieve this comparison, data available in studies about alkanolamine solvents at 303–333K and 5–50wt.% for alkanolamines solutions were considered. Results show that CO2 absorption by NH3 is faster than the one carried out by MDEA, except for 2wt.% NH3 at 288K. At 278K and using aqueous solutions of 3wt.% NH3, the absorption rate is almost identical to the one reached with MDEA solvent. The highest absorption capacity, also compared with alkanolamine solution, is reached with aqueous solutions of 5wt.% NH3 at 278K and 303K.

Reactive extraction of N-acetylneuraminic acid—Kinetic model and simulation of integrated product removal

The reactive extraction of N-acetylneuraminic acid with phenylboronic acid (PBA) and trioctylmethylammoniumchloride (TOMAC) is a new method to recover neuraminic acid from reaction solutions. We describe a kinetic model which is suitable to describe the extraction of pure compounds as well as mixtures of the reactants, which are N-acetyl- d-glucosamine (GlcNAc), N-acetyl- d-mannosamine (ManNAc), sodium pyruvate (Pyr) and neuraminic acid (Neu5Ac). For the extraction a two-step mechanism is assumed and the ion exchange at the interface was determined to be the rate-limiting step. Kinetic measurements were performed in a Lewis-type cell. The first reaction step is included in the model by a parameter σ which describes the extractable amount of carbohydrate. The extraction model is combined with a model describing the enzymatic synthesis of Neu5Ac from GlcNAc to simulate the integration of reaction and extraction. The integrated process was simulated with varying substrate concentrations, carrier concentrations, phase ratios and interfacial area. A batch reaction with concurrent extraction and continuous renewal of the organic phase was developed. Under optimised conditions neuraminic acid is produced with the same space–time yield as without extraction and the product is accumulated in the organic phase, which facilitates further downstream processing. The developed model is feasible to analyse and evaluate integrated product removal as well as separately operated reaction and extraction.

A study of the formation of acid and neutral yttrium oxalate powders from precipitation-stripping reaction in a Lewis-type cell

In a previous paper, a kinetic study of the precipitation stripping of yttrium oxalate powders from yttrium-loaded HDEHP solution was conducted using a Lewis-type cell. The variation in yttrium content in organic phase versus time with a constant liquid-liquid interfacial area allowed the determination of the initial precipitation stripping rate. The work reported here has used these experimental results and observations to investigate mechanisms for the precipitation of YH(C 2O 4) 2 · 3H 2O(s) and Y 2(C 2O 4) 3 · 10H 2O(s) salts. The precipitation of the acid salt is assumed to be based on a fast nucleation step followed by a continuous growth process. The rate-controlling step is the displacement of organic dimers H 2L 2 from the intermediate complex Y(HL 2) 2 + adsorbed onto a free site of the salt located at the liquid-liquid interface by oxalic acid. The precipitation of the neutral salt can be analysed by a model based on nucleation and agglomeration, assuming that there is negligible growth. In the mechanism considered the rate-controlling step is the first step of the stripping reaction of yttrium.

Precipitation-stripping of yttrium oxalate powders from yttrium-loaded HDEHP organic solutions using an ultrasonic stirrer

In previous papers, a kinetic study on the precipitation-stripping of yttrium oxalate powders from yttrium-loaded HDEHP solution had been conducted using a Lewis-type cell. In the present work, the precipitation-stripping of yttrium oxalate has been investigated in a reactor with an ultrasonic stirrer. This study shows the influence of several parameters on the precipitation yield, the solubility of yttrium in the aqueous phase, the nature, and the size distribution of the precipitated salt. The parameters which could vary were: initial concentrations of nitric (0–5 mol L −1) and oxalic (0.15–0.75 mol L −1) acids in the aqueous phase, initial concentrations of Y(HL 2) 3 (0.075–0.10 mol L −1) and HL (0.8–2.2 mol L −1) in the organic phase, nature of the organophosphorus acid used ((RO) 2PO 2H, R(RO)P0 2H with R = 2-ethylhexyl), temperature (24–60°C), ratio of the volumes of phases ( r = V o V a varying from 0.5 to 4). The nature of the precipitated salt depended on the concentrations of oxalic and nitric acids. At ambient temperature, neutral salt Y 2(C 2O 4) 3 · 10H 2O(s) was precipitated as aggregated platelets, the median diameter of which could vary from I to 4 μm according to the experimental conditions. Acidic salt YH(C 2O 4) 2 · 3H 2O(s) was precipitated in concentrated acidic aqueous media as platelets with a median diameter which could vary from 4 to 7 μm.

Kinetics of Absorption of CO2 in Concentrated Aqueous Methyldiethanolamine Solutions in the Range 296 K to 343 K

The kinetics of CO2 absorption by aqueous solutions of methyl diethanol amine (MDEA) were measured in the temperature range (296−343) K and MDEA concentration range (830−4380) mol·m-3 (10−50 mass %). A thermoregulated constant interfacial area Lewis-type cell was operated by recording the pressure drop during batch absorption. The kinetic results are in agreement with a fast regime of absorption according to film theory. MDEA depletion at the interface has a significant effect on the kinetics at the CO2 pressures (100 to 200 kPa) studied in this work, especially at low temperatures and low MDEA concentrations. Considering only the reaction between CO2 and MDEA, the CO2 absorption appears as a first-order reaction with respect to MDEA. The activation energy found for the reaction between CO2 and MDEA is 45 kJ·mol-1, but this value depends significantly (by about 10% in the worst case) on the vapor−liquid equilibrium data used.

Development of kinetic equations for the extraction of copper by LIX65N based on interfacial reaction mechanism

Although a number of kinetic studies on the extraction of copper with chelating reagents have been reported they contain contradictory views on the location of chelate formation in solvent extraction and on the rate-controlling steps. In the present work a kinetic study of the extraction of copper from aqueous solutions with 5-nonyl 2 hydroxy benzophenone oxime (LIX65N) was carried out. This was achieved through the development of kinetic equations based on the interfacial reaction model as well as experiments using the Lewis type cell. The overall rate of extraction was found to be dominated both by two interfacial reactions forming the copper-oxime complex and by mass transfer in the aqueous phase. The fact that diffusional or mass transfer resistance played an important role could also be supported by the occurrence of interfacial turbulence at the initial stage of extraction, in addition to the low activation energy of the rate constant. The rate of backward reaction was proportional to [H +] and [CuR 2], respectively, and almost independent of [H 2R 2].

Kinetics of the extraction of phenylalanine and glutamic acid by ion-exchange carriers

Biological transport of amino acids is usually mediated by carrier proteins buried in biomembranes. The application of models to such transport systems has long been desired in the separation science and technology of amino acids and is an active area of research. Recently, the application of commercial metal extractants as mobile carriers in the liquid membrane technology has attracted increasing attention due to their potential capability in the field of bioseparation. In the development of such a novel separation technique, knowledge of the extraction kinetics is necessary in addition to knowledge of the extraction equilibrium. Due to their zwitterionic character, it is possible to extract amino acids with ion-exchange carriers by controlling the pH of aqueous amino acid solutions. A modified Lewis-type cell experiment was used to study the extraction kinetics of glutamic acid (system I) and phenylalanine (system II) by naphthenic acid, and that of phenylalanine by a quarternary ammonium salt, Aliquat 336 (system III). The effects of agitation, interfacial area, carrier concentration, pH, and initial concentration of amino acids on the extraction rate were discussed. A rate equation involving the mass transfer terms was derived, based on an interfacial chemical reaction mechanism. It was found that the limiting case, based on an interfacial reaction rate-determining mechanism, was in good agreement with the experimental results. The intrinsic chemical reaction is controlled by the formation of an amino acid/ carrier complex at the interface. The mechanism of extraction proposed in this study is applicable to both glutamic acid and phenylalanine in the two ionic carrier systems.

EXTRACTION OF ORGANIC SOLUTES BY LIQUID MEMBRANES

Abstract The kinetics of liquid membrane extraction of organic solutes (phenol, pyridine,m-toluidine, phenylalanine) from aqueous solution is studied. The experiments were carried out in a Lewis-type cell and in a liquid membrane device with flowing aqueous films and a circulating organic membrane liquid. From the results it can be concluded that when the goal is to obtain a more concentrated stripping solution, higher flow rates of the feed should be used; when a more complete recovery or separation of different organic solutes is aimed at, lower flow rates should be used.

Kinetic Study of the Extraction of Glutamic Acid by Naphthenic Acid in a Modified Lewis-Type Cell

Abstract Due to the zwitterionic character, we may extract amino acids with ion-exchange carriers by controlling the pH of aqueous amino acid solutions. A modified Lewis-type cell experiment was conducted to study the extraction kinetics of glutamic acid by naphthenic acid, a cation-exchange carrier. The effects of agitation, interfacial area, carrier concentration, pH, and initial concentration of amino acid on the extraction rate were discussed. By comparison of the experimental results with the proposed interfacial extraction mechanism, it was found that the extraction equilibrium constant, K cx, is 1.62 × 10−2, the apparent forward extraction rate constant, k 1, is 0.63 cm4/mol·s, and the reverse rate constant, k −1, is 38.9 cm4/mol·s. The intrinsic chemical reaction is controlled by the formation of an amino acid/carrier complex at the interface. The extraction mechanism proposed was successfully correlated with the experimental results.

Mechanism and kinetics of palladium extraction with .BETA.-hydroxyoxime.

Extraction rates of palladium(II) with 2-hydroxy-5-nonyl acetophenone oxime were measured by use of a Lewis-type cell to elucidate the extraction mechanism. It was found that the rate of complex formation both at the interface and in the aqueous phase was determined by the 1:1 complex formation between trihalo complex of palladium, PdX3(H2O)– and the neutral species of β-hydroxyoxime, HR. The extraction rate of the bromo complex of palladium was faster than that of the chloro complex. The rate constants for the complex formation obtained from the extraction rate were compatible with those obtained in an 80 wt% ethanol–water mixture.

Kinetic study of the extraction of copper(ii) by di(2-ethylhexyl)phosphoric acid in a Lewis-type cell

The rate of extraction of copper from aqueous nitrate media by di(2-ethylhexyl)phosphoric acid (D2EHPA) has been studied both theoretically and experimentally. A kinetic equation involving the diffusional or mass transfer resistance term was developed. The mass transfer resistance was found to have a significant influence on the overall rate of the extraction system. It could be inferred that a second intermediate complex was formed by the reaction of CuR i + with extractant in the organic bulk phase and also that the intrinsic chemical reaction was controlled by this step. A similarity between the Szyszkowski equation and the “interface saturation model” could be observed in the evaluation of the interfacial population of extractant.