Solvent Extraction Of Cadmium Research Articles

Modelling and Optimizing the Solvent Extraction of Cadmium from Phosphoric Acid using Experimental Design

The removal of cadmium from phosphoric acid was carried out using the solvent extraction process, taking into account factors such as pH, concentration of the extracting agent [EA], organic phase/aqueous phase (O/A) ratio, stirring time and stirring rate. In order to study the effect of these involved factors and their interactions on the extraction percentage of cadmium, a composite central design (CCD) of 24 experiments was adopted. An empirical model was developed and validated by applying ANOVA analysis. The graphical representation of this model in the variable space allowed to determine the optimal conditions of these factors. The extraction of cadmium from phosphoric acid reached a percentage of the order of 98%, under the following conditions: pH = 3, [EA] = 10-2 M, O/A = 1.1, stirring time 90 min, stirring rate 800 rpm.

Solvent extraction of cadmium and zinc from sulphate solutions: Comparison of mechanical agitation and ultrasonic irradiation

This research was conducted to evaluate the potential of ultrasonic irradiation during the solvent extraction of metals, and comparing its efficiency with a mechanically stirred system (MSSX). The simultaneous extraction of zinc and cadmium from sulphate solutions was investigated by di-(2-ethylhexyl) phosphoric acid (D2EHPA) as an organic extractant which was diluted (20%) in kerosene at the organic: aqueous phase ratio of 1:1 and the temperature of 25°C. The influence of some critical parameters, including contact time, solution pH, ultrasonic power, and zinc/cadmium ratio were investigated on the extraction of the metals. Results show that D2EHPA selectively extract zinc rather than cadmium in both mechanically and ultrasonically mixed systems. It was also found that increase of ultrasonic power from 10 to 120W cause a small decrease in zinc extraction; while, at low and high levels of the induced power, cadmium extraction was significantly decreased. Results also show that maximum extraction amounts of zinc (88.7%) and cadmium (68.2%) by the MSSX system occurred at the pH of 3 and the contact times of 3 and 20min, respectively. Although capability of extraction in the ultrasonically assisted solvent extraction (USAX) system for both metals was higher, the selectivity was lower than that of MSSX system under different conditions especially in high zinc/cadmium ratios. It can be concluded that physical effects (i.e. mixing) inducing at low ultrasonic powers (below 60W) mainly results in increasing solvent extraction rate, while the chemical actions applied at the higher powers have a negative outcome on the extraction rate particularly for cadmium.

Highly Efficient Extraction of Cadmium(II) in Nitrate Medium by Quarternary Ammoniums

The solvent extraction of cadmium(II) from nitrate medium was studied. The using extractants were quaternary ammonium-based room temperature ionic liquid Aliquat 336 in either the chloride [(C8H17)3 CH3N+·Cl-], thiocyanate [(C8H17)3CH3N+·SCN-] and hydrogenophosphate forms, diluted in the kerosene. The effects of different parameters such as equilibration time, initial pH, O/A molar ratio (nextractant/nCd), initial extractant concentration and ionic strong on extraction of cadmium(II) were investigated. The extraction yields of cadmium(II) increase with increasing initial pH and initial extractant concentration. The stoichiometry of the extracted species was determined on the basis of slope analysis. The effect of various salts such as KSCN and NaNO3 in the feed solution within the concentrations of 10 to 100 mM on extraction of cadmium(II) was studied at optimal initial pH = 6.2. The relation between the percentages of the extracted species () and the extraction yields were investigated by a calculation program using CHEAQS V. L20.1. The results showed that the decrease of the extraction yield of Cd(II) was related with the decrease gradually of percentage of cadmium(II) free and the increase of percentage of and species with the addition of KSCN. More the hydrophobic character of the extractant is high, more the extraction is better. The metal ion was stripped out satisfactorily using nitric acid as stripping agent, in one step.

Solvent extraction of cadmium(II) from chloride solutions by pyridyl ketoximes

The solvent extraction of cadmium(II) from chloride solutions using 1-(2-pyridyl)-tridecane-1-one (2PC12), 1-(2-pyridyl)-pentadecane-1-one (2PC14), 1-(4-pyridyl)-tridecane-1-one (4PC12) and 1-(4-pyridyl)-pentadecane-1-one (4PC14) oximes has been investigated. The influence of extractant concentration, metal concentration, chloride ion concentrations and of various polar and non-polar diluents was studied. The results indicate that only 2-pyridyl ketoximes extract cadmium(II) from chloride solutions as a solvating dimer complex (CdCl 2(2PC12 or 14) 2) and the extraction depends on the diluent, reagent concentration and chloride ion concentration. Cadmium(II) was effectively extracted using a chloroform and hydrocarbons mixed with decan-1-ol as diluents and stripped from the loaded organic phase with water and ammonia aqueous solutions.

Solvent extraction of cadmium from sulfate solution with di-(2-ethylhexyl) phosphoric acid diluted in kerosene

In the present paper, solvent extraction process has been used for extraction of cadmium from sulfate solution using di-(2-ethylhexyl) phosphoric acid (D2EHPA) with 1% isodecanol in kerosene diluent expected from industrial effluents or leaching of ores/secondary materials. Different process parameters such as pH, contact time, extractant concentration, O/A ratio etc. were investigated. Results demonstrated that quantitative extraction of cadmium was feasible from 4.45 mM cadmium feed solution in single stage at equilibrium pH 4.5, time 2 min and O/A ratio 1:1 with 0.15 mM D2EHPA. The extraction mechanism of cadmium from sulfate solution by D2EHPA in kerosene could be represented at equilibrium by Cd 2 + + 3/2 (H 2A 2) org ⇔ CdA 2(HA) org + 2H +. The loading capacity of 0.15 mM D2EHPA in sulfate solution was determined to be ∼ 8.9 mM cadmium. The loaded cadmium was effectively stripped using 180 g/L sulfuric acid. The metal or salt could be produced by electrolysis or crystallization from the stripped solution.

Chloride leaching and solvent extraction of cadmium, cobalt and nickel from spent nickel–cadmium, batteries using Cyanex 923 and 272

Studies are conducted on the leaching and solvent extraction separation of metals from chloride leach liquor of spent nickel–cadmium batteries with Cyanex 923 and 272 diluted in kerosene as the extractants. Dissolution of the metals increases with increase in acid concentration and time but decreases with the solids-to-liquid ratio. Complete dissolution of Cd, Co and Ni can be achieved with 1.5 M HCl at 85 °C for 8 h and a solids-to-liquid ratio of 4. Treatment of leach liquor for the separation of metals with Cyanex 923 shows that increase of extractant and chloride ion concentration increases the percentage extraction of cadmium. The plot of log[distribution coefficient] versus log[extractant]/[Cl −] is linear with a slope of 2, which indicates that the extraction follows a solvation mechanism with the extracted species as CdCl 2·2S (S, Cyanex 923). Moreover, Cyanex 923 enables a clear separation of Cd from Co and Ni. Extraction of cobalt with Cyanex 272 involves a cation-exchange mechanism with the formation of a 1:2 metal-to-ligand complex in the organic phase. Based on the distribution data, extractant concentration and equilibrium pH of the aqueous phase, a possible separation process is proposed for the recovery of cadmium, cobalt and nickel with >99% efficiency.

Ion-pair extraction of cadmium complex anions from hydrochloric acid media using oxonium ion-dicyclohexyl-18-crown-6 complex

Solvent extraction of cadmium from aqueous hydrochloric acid media (1–11 mol dm −3) into dichloromethane solution of 18-crown-6, dibenzo-18-crown-6 and dicyclohexyl-18-crown-6 (DC18C6) has been studied at 25 °C. The highest extraction abilities have been found by DC18C6 in the range of 6–7 mol dm −3 hydrochloric acid. The conventional log–log plot analysis of the extraction equilibrium data at 3 and 8 mol dm −3 of the acid revealed that the cadmium ions were extracted as ion-pairs [ H L + ] [ CdC l 3 − ] and [ H L + ] 2 [ CdC l 4 2 − ] (L = DC18C6), respectively. The effect of diluent has been investigated using chloroform, dichloromethane, 1,2-dichloroethane, carbon tetrachloride and toluene. The extraction of the cadmium increased with diluent polarity. The ability of DC18C6 to separate cadmium from binary mixtures of Cd and M (M = Ni, Mn, Co, Zn, Pb and Fe) has been evaluated. The efficiency and selectivity of the method allow to propose it for the recovery of cadmium from consumed Ni–Cd rechargeable batteries.

Solvent extraction of cadmium (II) from sulphate solutions using TOPS 99, PC 88A, Cyanex 272 and their mixtures

Extraction of cadmium (II) from sulphate solutions using organophosphorous-based extractants—TOPS 99, PC 88A and Cyanex 272 has been studied. Percent extraction of cadmium (II) increased with increasing equilibrium pH of the aqueous phase and extractant concentration. Extraction of Cd (II) by organophosporus extractants involves cation exchange mechanism with the formation of 1:3 metal to reagent complex. Characterization of the solid complex of cadmium with TOPS 99 by FTIR, 31P NMR supported metal complex formation with the phosphorus-hydroxyl (P-OH) group. Finally, the extraction behavior and possible separation of cadmium and nickel from the mixture of metals was studied.

Solvent extraction of cadmium (II) from acidic media by Cyanex 302

The extraction of Cd (11) from chloride media of 1.0 M ionic strength by the commercial extractant Cyanex 302 in kerosene has been studied over a range of pH and reagent concentrations. The data have been analyzed both graphically and numerically to determine the stoichiometry of the extracted complexes and their extraction constants. The species CdR 2(HR) and CdR 2(HR) 2, HR being the active component in the commercial extractant, bis(2,4,4-trimethylpentyl)thiophosphinic acid, have been found to be responsible for the extraction behaviour observed.

THE SOLVENT EXTRACTION OF CADMIUM AND ZINC BY MIXTURES OF CARBOXYLIC ACIDS AND ALKANETHIOLS

ABSTRACT The effect of some aliphatic sulphur-containing compounds on the solvent extraction of cadmium and zinc by representative carboxylic acids (HA) is described. Alkanethiols (RSH) were found to cause large synergistic shifts in the pH0.5 values for the extraction of cadmium (up to 2.85 pH units for the addition of 0.25 M thiol to 0.25 M carboxylic acid), with much smaller shifts for zinc (up to 0.84 pH unit). With the isomeric C8-thiols, the extent of the shifts for both metals is greater for the straight-chain compound (R = n-octyl) than for branched-chain analogues (R = 2-ethylhexyl or 2-octyl). Smaller synergistic shifts were obtained with dialkyl sulphides (RSR), whereas with dialkyl disulphides (RS.SR) slight antagonistic shifts were found. Slope analysis studies suggest that for mixtures of 3,5-diisopropylsalicylic acid (HA) and 1-octanethiol (RSH), the extracted cadmium species has the stoichiometryCdA(HA)Cd4(RS)10)CdA(HA), for which two possible structures are suggested. With these extractan...

Solvent Extraction of Cadmium as a Previous Step for its Determination in Biological Samples by Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract A method is proposed for the solvent extraction of cadmium using 1,5-bis[1-(2-pyridyl)ethylidene] thiocarbonohydrazide (APTH) as extractant. The optimum extraction conditions were evaluated from a critical study of the effect of pH, concentration of extractant, shaking time and ionic strength. The maximum volume ratio of the aqueous to organic phase was 25:1 for a single-stage extraction of 99-100 % of the metal ion. The detection limit is 0.15 ng/ml cadmium, and the calibration is linear from 0.2 to 500 ng/ml. The effect of interferences was studied and no interferences from the elements commonly found in biological materials were observed. The extraction method was applied to the determination of cadmium in some biological materials using inductively coupled plasma atomic emission spectrometry (ICP-AES).

The influence of aqueous chloride media on the solvent extraction of cadmium by trilaurylammonium chloride in toluene

The extraction of Cd(II) from chloride solutions by trilaurylammonium chloride, TLAHCl, dissolved in toluene has been studied by means of metal distribution measurements. The experimental data have been obtained at different chloride concentrations of the aqueous phase (ranging from 1.0 to 3.0 mol dm −3) and applying the constant ionic medium method. The results show an enhancement of the cadmium extraction when the aqueous chloride concentration is increased. The extraction process is explained by assuming that the species CdCl 2(TLAHCl) 2 and CdCl 2(TLAHCI) 3 are formed in the organic phase, and the corresponding extraction reactions are: C d 2 + + 2 C l - + 2TLAHCl ( org ) ⇌ C d C l 2 ( TLAHCl ) 2 ( org ) ; K 2 C d 2 + + 2 C l - + 3TLAHCl ( org ) ⇌ C d C l 2 ( TLAHCl ) 3 ( org ) ; K 3 This model has been found to be independent of the chloride concentration in the aqueous phase. However, the values of their extraction constants K 2 and K 3 are different for the various chloride concentrations used. The values of K 2 and K 3 at a different chloride concentration, I, have been correlated by using the specific-interaction theory (S.I.T.), and the interaction coefficient for the Cd 2+, Cl − ions, as well as, the thermodynamic constants, K n o, have been determined.

Solvent extraction of cadmium by di (2-ethylhexyl) phosphoric acid.

Solvent extraction of cadmium by di (2-ethylhexyl) phosphoric acid.

Solvent extraction of cadmium(II) from thiocyanate solutions with methylisobutylketone and trioctylphosphine oxide in hexane.

Solvent extractions of cadmium(II) in aqueous sodium thiocyanate solution and 1 mol dm-3 Na(SCN, C104) constant ionic media have been studied at 298 K. The extraction with methylisobutylketone(4-methy1-2-pentanone) was poor but that with trioctylphosphine oxide in hexane was effective if the concentration was above 1×10-2 mol dm-3. By a chelate extraction method, the stability constants of the thiocyanate complexes were determined and the extraction equilibria with these solvating type extractants were analyzed by using these constants. From a comparison of the results with those of zinc(II), it was concluded that though cadmium(II) complexes are more stable than those of zinc(II), their extractability is much inferior to that of the latter.

Solvent extraction of cadmium from alkaline cyanide solutions with quaternary amines.

Quaternary amines are unique in their ability to extract metal cyanides from highly alkaline solutions. Cadmium cyanide extracts essentially quantitatively at both the subnanogram and macro levels. Regeneration of the amine solvent is achieved by stripping the cadmium with sodium hydroxide, sodium hypochlorite, or alkaline or acidic formaldehyde solutions. Because they readily extract free cyanide as well as anionic metab cyano complexes, the high-molecular-weight quaternary amines show considerable promise for industrial pollution abatement applications.

Solvent Extraction of Cadmium(II) from Aqueous Chloride and Bromide Solutions by Tri-n-octylamine

Abstract The distribution of cadmium(II) between dilute hydrochloric or hydrobromic acid solution and tri-n-octylamine dissolved in a number of diluents has been measured for several cadmium (II) loadings and amine concentrations. Diluents investigated are n-hexane, cyclohexane, benzene, xylene, toluene, carbon tetrachloride, chloroform, chlorobenzene and o-dichlorobenzene. The results show that all the species extracted into various diluents are present in the form of bis(tri-n-octylammonium)tetrahalocadmium(II). The specific ability of each diluent in extracting cadmium(II) from acidic halide solutions is approximately correlated with the dielectric constant of the pure diluent, suggesting that the dissociation of ion paired alkylammonium salt in the organic phase is responsible for the extraction.