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Di(2-ethylhexyl) dithiophosphoric acid (D2EHDTPA) was examined for cadmium removal from phosphoric acid solutions. High extraction performance was achieved. By means of slope and saturation methods, the stoichiometry of the complex was postulated. Both methods indicated the presence of anhydrous CdR2 as being the metallic extracted complex, HR denoting the D2EHDTPA molecule. The stripping of cadmium from the organic phase was ensured by aqueous solutions of HCl; quantitative stripping was achieved with either HCl (4 M) or an HCl-NaCl mixture. [ABSTRACT FROM AUTHOR]

Abstract: Kinetics of nickel(II) extraction by 2-ethylhexanal oxime (EHO) has been investigated in a homothetic cell (Rushton cell) from ammonium solutions. The kinetic study was carried out with a stirring speed fast enough to eliminate the diffusion limitation. The chemical regime can then be assumed and the kinetic result can be used to determine the reaction mechanism. Thus, a kinetic mechanism has been suggested and a limiting step found. Influence of pH and the concentrations of NH4NO3 and EHO on rate have been investigated and results suggest that the limiting step is an interfacial reaction between a molecule of EHO monomer (HOx) and the adsorbed complex Ni(Ox)(H2O)5ad +. [Copyright &y& Elsevier]

• A process for the simultaneous recovery of silver and gold from leaching solutions is proposed • The approach allows recovering in a single stage the two metals, reducing the equipment required • Extraction of silver and gold is performed by D2EHDTPA • Mathematical models are proposed to predict the performance of the extraction and the stripping/scrubbing. This study is focused on the extraction and recovery of gold and silver from thiourea acid leaching ore liquors. In a first step, extraction is performed using di(2-ethylhexyl)dithiophosphoric acid (D2EHDTPA). The extraction of gold and silver takes place simultaneously, allowing the removal of both metals in a single equipment under the same operational conditions. Each metal is then recovered by selective stripping, using NH 4 SCN/H 2 SO 4 solutions to separate the silver from the D2EHDTPA. Such treatment is followed by a second stripping system, where a (NH 4) 2 S 2 O 3 solution is used to recover gold. A mathematical model is developed to represent all the operations in the process flowsheet. Through this model, it is predicted that, for properly selected operating conditions, recoveries higher than 99.9% for silver, gold and thiourea (to be recycled) can be obtained. The data predicted by the model has a good fit with previously reported experimental data. The proposed process is a more sustainable approach, in comparison with the traditional process involving cyanide, and has potential to be economically feasible. [Display omitted] [ABSTRACT FROM AUTHOR]