C. Caravaca

Considerations about the recycling of EAF flue dusts as source for the recovery of valuable metals by hydrometallurgical processes

Abstract The present work takes an EAF flue dust to research its possibilities as resource from which to recover valuable base metals, principally zinc, by means of hydrometallurgical processes. At the same time this approach renders a recycle of the flue dust and thus decreases its environmental impact. The EAF flue dust is leached by different leaching reagents: acid, basic and complexing, and from the different pregnant solutions several approaches were proposed to obtain the most valuable metals contained in it. These approaches included the application of solvent extraction and other hydrometallurgical techniques.

The phosphine oxides Cyanex 923 and Cyanex 925 as extractants for gold(I) cyanide aqueous solutions

Abstract The behaviour of the phosphine oxides Cyanex 923 and Cyanex 925 in the recovery of gold(I) from cyanide solutions is described. Extractions are studied as a function of several variables such as temperature, diluent aromaticity, ionic strength and extractant concentration. Gold(I) stripping can be accomplished effectively with low aqueous ionic strength solutions and at high temperatures. From the experimental results it is seen that Me+-Au(CN)2−·3R3PO, where Me+=Li+ and R3PO=the phosphine oxide, is extracted into the organic phase. The extracted species is probably solvated by water.

The extraction of gold(I) from cyanide solutions by the phosphine oxide Cyanex 921

Abstract The extraction of gold from cyanide solutions by the commercially available phosphine oxide, Cyanex 921, is described. The effect of several variables, such as equilibration time, temperature, diluent aromaticity, extractant concentration and the ionic strength of the aqueous phase is discussed. An IR spectroscopy study showed that the Au (CN) 2 − complex and the extractant did not form a discrete compound, supporting a solvating mechanism of extraction. Results showed that the phosphine oxide could effectively extract gold(I) cyanide from alkaline solutions. Stripping was accomplished by low ionic strength aqueous solutions and enhanced by high temperatures.

Study of the extraction of zinc(II) in aqueous chloride media by Cyanex 302

Abstract The partition of zinc(II) between aqueous hydrochloric acid/chloride solutions and solutions of Cyanex 302 (bis (2,4,4-trimethylpentyl] monothiophosphinic acid), in kerosene was studied at various aqueous pH values, extractant and zinc concentrations, different temperatures and equilibration times. The behaviour of the extraction system with different organic diluents and aqueous ionic strengths, in relation to other organophosphorus extractants and to the selectivity of the extractant in systems containing zinc(II) and other metallic ions was also investigated. The zinc(II) extraction mechanism is discussed on the basis of the experimental results.

Study of the ZnSO4-Cyanex 302 extraction equilibrium system

Abstract The application of the new extractant Cyanex 302 (Cyanamid), bis (2,4,4-trimethylpentyl) monothiophosphinic acid, as an extraction agent of zinc(II) from sulphate medium is studied. The extraction system is studied as a function of several variables, such as the diluent of the organic phase, temperature, metal concentration in the aqueous phase, etc., along with the zinc(II) stripping stage by sulphuric acid. The behaviour of Cyanex 302 has been studied with respect to other organophosphorous extractants and also the selectivity of the reagent in the system zinc(II) versus iron (III).

The use of primary amines in gold (I) extraction from cyanide solutions

Abstract The application possibilities of gold(I) extraction from cyanide media by three primary amines, Primene 81R, Primene JMT and tridecylamine, has been studied taking in account several variables such as temperature, amine and initial metal concentrations, aqueous ionic strength and organic phase diluent; the selectivity of the extraction systems is also described. On the basis of graphical and numerical treatment an extraction mechanism for gold has been proposed.

Study of gold (III)-HCl-amine Alamine 304 extraction equilibrium system

Abstract The extraction of gold (III) from hydrochloric acid solutions using solutions of the tertiary amine Alamine 304 in xylene was studied as a function of several variables, such as the hydrochloric acid concentration and ionic strength of the aqueous solution. The extraction of hydrochloric acid by Alamine 304 in xylene has also been studied. A mechanism for the extraction of gold (III) is suggested from the results obtained.

Solvent extraction of Au(CN)2−1 with mixtures of the amine Primene JMT and the phosphine oxide Cyanex 923

Abstract The partition of gold(I) between aqueous cyanide solutions and organic phases of the mixture of the amine Primene JMT and the phosphine oxide Cyanex 923 in xylene was studied at various aqueous pH values, extractant mixtures and gold concentrations, different temperatures and equilibration times. The behaviour of the extraction system with different organic diluents, aqueous ionic strengths and the selectivity of the system with respect to the extraction of different metal-cyano complexes was also investigated. The gold(I) extraction mechanism is discussed on the basis of the experimental results and numerical treatment of the experimental data, the species formed in the organic phase having the probable stoichiometry HAu(CN)2RNH2(R3PO)n, n being 1 (log Kext 11.94 ± 0.07) or 2 (log Kext 12.45 ± 0.I5). Stripping of gold from loaded organic solutions was also studied using low ionic strength alkaline solutions (NaCN at 50°C or NaOH at 40°C).

Synergistic extraction of gold(I) cyanide with the primary amine Primene JMT and the phosphine oxide Cyanex 921

Abstract The extraction of gold(I) from aurocyanide solutions has been studied by means of the synergic mixture of the primary amine Primene JMT and the phosphine oxide Cyanex 921. Different variables that could affect the solvent extraction system were evaluated: equilibration time, temperature, aqueous pH, metal concentration, extractant mixture concentration, organic phase diluent and aqueous ionic strength. The system is selective with respect to the extraction of other metal-cyano complexes. On the basis of the experimental data, treated both graphically and numerically, the extraction mechanism and the stoichiometry of the extracted species were proposed. Stripping of gold from loaded organic phases was also studied using low ionic strength alkaline solutions.

Extraction of gold(I) cyanide by the primary amine tridecylamine

Abstract The extraction of gold(I) from cyanide solutions by tridecylamine/xylene solutions was studied at various temperatures, amine and metal concentrations. The influence of different diluents, aqueous ionic strength and the use of different mixtures of organophosphorous reagents and ketones with the amine in metal extraction was evaluated, and also the selectivity of the present extraction system. The gold-amine extraction mechanism is discussed.