Man-Seung Lee

Recovery of copper, tin and lead from the spent nitric etching solutions of printed circuit board and regeneration of the etching solution

Abstract In order to recover valuable metals and regenerate the etching solution from the spent nitric etching solutions of printed circuit board (PCB), solvent extraction, stripping, electrowinning, precipitation and cementation experiments have been performed. Nitric acid was selectively extracted by TBP from the spent etching solution and pure nitric acid solution was stripped by distilled water. After extracting nitric acid, pure copper metal was obtained by electrowinning and tin ions were precipitated by adjusting the pH of solution with Pb(OH)2. Lead metal with purity of 99% was obtained by cementation with iron powder.

Solvent extraction separation of indium and gallium from sulphate solutions using D2EHPA

Abstract Solvent extraction and stripping experiments have been performed to separate indium from gallium in sulfuric acid solutions. In the extraction process, the separation factor between indium and gallium decreased with pH and a maximum value of the separation factor was obtained by extracting metals from the mixed solutions with stoichiometric concentration of di-2-ethyl-hexylphosphoric acid (D2EHPA) to extract both metals. It was found that aliphatic kerosene was superior to benzene as a diluent in respect of loading capacity. In the stripping process, the stripping percentage of indium decreased from 95% to 5% with pH in the pH range of 0.2–1.4, while separation factors increased with the pH of the stripping solutions. From simulation experiments for multistage countercurrent extraction, nearly complete separation of indium and gallium would be accomplished by a two-stage extraction.

Determination of Pu and U isotopes in safeguard swipe sample with extraction chromatographic techniques.

A simple and reliable separation method of plutonium and uranium was developed using extraction chromatographic techniques. Using the separation method of plutonium and uranium developed in this study, recoveries of plutonium and uranium were compared with those by commercial separation methods of Pu and U. The redox reactions of hydrogen peroxide with plutonium in a nitric acid medium were investigated by UV-vis-NIR absorption spectroscopic techniques. The separation method of Pu and U isotopes with the UTEVA resin updated in this study could be effective to measure quantitatively nano- and picogram amounts of uranium and plutonium in swipe samples using isotope dilution thermal ionization mass spectrometry (ID-TIMS).

Use of the bromley equation for the analysis of ionic equilibria in mixed ferric and ferrous chloride solutions at 25 °C

The ionic equilibria in the mixed ferric and ferrous chloride solution were analyzed by considering the complex formation reactions as well as the mass and charge balance equations. The activity coefficients of the ions were calculated using the Bromley equation. The equilibrium constants for the formation of ferrous complexes were determined from the reported thermodynamic data. The interaction parameters of the ferric species were estimated from the reported values of FeCl3 in an HCl solution. By applying the ionic equilibria, the speciation of the ferric and ferrous species with the composition was obtained. The predicted pH values of the FeCl3-FeCl2-HCl-H2O system agreed well with the measured values at 25 °C in the ionic strength range of up to 9.34 m.

Solvent Extraction of Sn(IV) from Hydrochloric Acid Solution by Alamine 336

The solvent extraction behavior of Sn(IV) from hydrochloric acid was investigated using Alamine336 (Tri-n-cotylamine) as an extractant. The experimental parameters of the concentration of the HCl solution, chloride ions, extractant, and Sn(IV) were assessed. The results showed that the extraction percentage of Sn(IV) was more than 95% in our experimental range and was only slightly affected by the HCl concentration. The extraction reaction of Sn(IV) by Alamine 336 from the chloride solution was identified as follows: SnCl6 +2R3NHCl(org)=(R3NH)2SnCl6(org)+2Cl −, and K=6.3×10. Stripping experiments of Sn(IV) from the loaded organic phase were done by using several stripping agents. A stripping percentage of 90% was obtained with a 2.0 M NaOH solution. (Received May 6, 2010)

Solvent extraction separation of Zr and Hf from nitric acid solutions by PC 88A and its mixture with other extractants

Solvent extraction for the separation of zirconium and hafnium from strong nitric acid solution has been investigated by using several organophosphorous acids (D2EHPA, PC 88A and Cyanex 272) and its mixture. Among the single extractants, PC 88A showed the best performance for the extraction and separation of the two metals. Mixtures of PC 88A with neutral, cationic and anionic extractants were tested in order to improve the separation between Zr and Hf. Mixtures of PC 88A with TBP or Versatic 10 or TOA did not show much influence on the extraction and separation of the two metals. Extraction efficiency of both Zr and Hf was markedly enhanced by using the mixture of PC 88A and TOPO. The mixture of PC 88A and LIX 63 led to synergism in the extraction of Zr, while antagonism occurred in the extraction of Hf. The highest separation factor of 46 was obtained from 2 M HNO3 solution by the mixture of PC 88A and LIX 63.

Solvent Extractive Separation of Zirconium and Hafnium from Hydrochloric Acid Solutions by Organophosphorous Extractants and Their Mixtures with Other Types of Extractants

From 1 to 4 M HCl medium, zirconium was selectively extracted over hafnium by organophosphorous extractants (D2EHPA, PC88A, Cyanex 272). In order to increase the separation factor Zr/Hf, mixtures of organophosphorous extractants with amines (Alamine 336, Aliquat 336) or cationic extractants (Versatic acid 10, LIX 63) were employed in 1–4 M HCl medium. Mixtures with Versatic acid 10 and LIX 63 led to depression in the extraction percentages. But the mixture with LIX 63 was found to be the most effective in separating the two metals among the extractant systems tested in this study. The highest separation factor of around 9.5 was obtained with a mixture of 0.01 M LIX 63 + 0.05 M Cyanex 272 at HCl concentration of 2–4 M. The Zr and Hf were effectively stripped from the loaded mixture of LIX 63 + Cyanex 272 by sulfuric acid solution.

Chemical equilibria in ferrous chloride acid solution

Ionic equilibria of ferrous chloride solutions were analyzed by considering chemical equilibria, mass, and charge balance equations. The activity coefficients of solutes and water activity were calculated with the Bromley equation. The equilibrium constants for the formation of Fe(II) complexes were determined from the reported thermodynamic data. The effects of HCl and FeCl2 concentration on the distribution of Fe(II) species and on the activity of HCl were estimated by applying ionic equilibria. The solvent extraction behavior of FeCl2 with Alamine 336 was explained with the distribution of Fe(II) species. The predicted pH values for FeCl2-HCl-H2O system agreed well with those experimentally measured at 25°C.

Prediction of hydrogen ion activity in the ZnSO4-Na2SO4-H2SO4-NaOH-H2O system at 25 °C

Abstract For the ZnSO4–Na2SO4–H2SO4–NaOH–H2O system, a chemical model was developed to predict the hydrogen ion activity at 25 °C. This chemical model consisted of chemical equilibria, and mass and charge balance equations. The activity coefficients of solutes and the activity of water were calculated by using the Pitzer equation. The distribution of sulfate species as a function of the electrolyte concentration was obtained from the model. In the range of 0.5–4.3 m ionic strength of the solution, the experimental pH values were in good agreement with the predicted pH values. The mean activity coefficients of NaOH calculated by the Pitzer equation agreed well with the experimental values obtained from the literature.

Chemical model for the solvent extraction of GdCl3 from a chloride solution with saponified PC88A

Solvent extraction experiments of Gd with 40% saponified PC88A have been conducted from a chloride solution under different extraction conditions. The effect of saponification of an acidic extractant on the extraction of Gd was investigated. To analyze the ionic equilibria of a GdCl3 solution, we estimated the necessary thermodynamic properties from reported values. Moreover, when applying the chemical model developed in this study, we used experimental data to estimate the equilibrium constant for the extraction of Gd with partially saponified PC88A.