Studies on Complexation and Supercritical Fluid Extraction of Cd2+ with Calixarenes (original) (raw)
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Review on solvent extraction of cadmium from various solutions
Hydrometallurgy, 2000
Cadmium has wide application in the manufacturing of alloys, batteries, pigments and metal plating. The solid and liquid waste is generated during the production and at the end of service life. The recovery and recycling of cadmium from these waste materials is necessary to gain the metal values and protect the environment from hazard. In hydrometallurgical processes, solvent extraction is an important process for the recovery of non-ferrous metals from different aqueous leach liquor and waste effluent/solutions. In present paper, the solvent extraction processes for the extraction and recovery of hazardous metal cadmium from aqueous solutions associated with commonly metallic and non-metallic ions, such as sulfate, chloride, nitrate and phosphate have been reviewed. Different process parameters, viz. pH, organic- to -aqueous ratio, kinetics of extraction and stripping to establish the conditions required for the extraction of cadmium and formation of a complex in the organic phase from different solutions, have been reported. The studies show the possibility of extraction and separation of cadmium from different solutions containing other metallic ions using anionic, cationic, solvating or mixed extractants. However, further attempts are also being made to develop selective organic extractants to recover cadmium efficiently on a commercial scale. The findings of these studies are also reported.► SX is potential tool for separation/ purification of Cd from aq. solutions. ► Based on solution composition, the extractant or mixed extractants can be selected. ► Cyanex 302, Cyanex 923, PC 88A and D2EHPA are found effective. ► D2EHPA has commercial potential for extracting Cd from solution.
Journal of Hazardous Materials, 2010
This paper describes experimental work and the mathematical modeling of solvent extraction of cadmium(II) from neutral and acidic aqueous chloride media with a Cyanex 923 extractant in Exxol D-100. Solvent extraction experiments were carried out to analyze the influence of variations in the composition of the aqueous and organic phases on the efficiency of cadmium(II) extraction. In neutral and acidic chloride conditions, the extraction of cadmium(II) by the organophosphorous extractant Cyanex 923 (L) is based on the solvation mechanism of neutral H n CdCl (2+n) species and the formation of H n CdCl (2+n) L q complexes in the organic phase, where n = 0, 1, 2 and q = 1, 2. The mathematical model of cadmium(II) extraction was derived from the mass balances and chemical equilibria involved in the separation system. The model was computed with the Matlab software. The equilibrium parameters for metal extraction, i.e. the stability constants of the aqueous Cd-Cl complexes, the formation constants of the acidic Cd-Cl species and the metal equilibrium extraction constants, were proposed. The optimized constants were appropriate, as there was good agreement when the model was fitted to the experimental data for each of the experiments.
The Liquid-Liquid Extraction of Toxic Metals (Cd, Hg and Pb) by Calixarenes
2009
Toxic metals (Cd, Hg and Pb) are mostly present in the environment due to natural phenomenon and human activities as well. Exposure of these non-essential elements in the environment causes severe effects. They are known to cause problems in humans as well as in aquatic life. In this work, we demonstrate various studies regarding liquid-liquid extraction of selected ions with different functionalized calixarenes. This review article briefly discusses several molecular designs of calixarenes for divalent ion (Cd 2+ , Hg 2+ and Pb 2+) recognition; as well as the relationship between structure and selectivity of the macrocycles is elaborated. The article does not, however, attempt to cover all of the different approaches to these toxic metal ions extraction.
Chemical Engineering Journal, 2001
In this paper, the kinetics of the non-dispersive extraction and back-extraction of cadmium from high concentration aqueous solutions using D2EHPA as selective extractant are reported. Batch experiments were performed in order to analyse the influence of the initial Cd concentration in the feed, organic and back-extraction phases. The proposed kinetic model consists of a system of partial differential and algebraic equations describing the mass balances of Cd in the fluid phases of the hollow-fibre contactors and homogenisation tanks. The main hypothesis is that membrane mass transport controls the extraction kinetics. Two design parameters K m , membrane mass transport coefficient, and K eq , equilibrium parameter of the extraction reaction have been calculated from the correlation of the experimental results by the reported model. The comparison of experimental and simulated data confirmed the validity of the kinetic analysis.
Oriental Journal of Chemistry, 2016
The solvent extraction of cadmium (II) from phosphoric acid 2.5M by 3-methyl-2 (1H)quinoxaline-thione (C 9 H 8 N 2 S) is investigated in various experimental conditions. Obtained results show a variation of extraction of Cd with pH, and concentration. The conventional methods of slope analysis can't be performed successfully for understanding interaction mechanisms. A technique combining slope analysis with the variation of overall extraction constant with pH is performed in this case. There is no predominant removal mechanism, cadmium is extracted as complexes in Cd: : H 3 O + (OH-) stoichiometry varying between 1:1:0 and 1:3:3. The extraction reaction is a complex process including ion exchange-ion pair formation, organic and inorganic complexation, H 3 PO 4 deprotonation and solvatation phenomena. A best recovery of 43 to 60% is achieved in acidic conditions with C LH = 0.26M.
Extraction of cadmium by TODGA–dodecane and TBP–dodecane: A comparative study by MD simulation
Molecular dynamics (MD) simulation of [Cd(II)] along with nitrate ions and water in dodecane was carried out for different nitric acid concentrations. The extraction process using N,N,N’,N’-tetraoctyldiglycolamide (TODGA) and tributyl phosphate (TBP), in biphasic systems, is also simulated at three nitric acid concentrations. In the TBP-based system, the formation of a third phase was observed at 3 M nitric acid concentration. Cd(II) ions form reverse micelles-like clusters with TODGA as an extractant in dodecane. The mass percentage of TODGA in these clusters decreases with increase in the acid concentration while increasing the size of the aggregates at the same time.