Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group ib metal
Patent
1994-10-19
1997-05-27
Gorgos, Kathryn
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group ib metal
423 87, 423139, 75712, 75714, 205581, C22B 326
Patent
active
056329636
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for the removal of the impurity elements arsenic and optionally antimony, bismuth or iron from solutions of valuable metals by solvent extraction and subsequent separation of the impurity elements.
In the context of the invention, "valuable metals" are understood to be the elements copper, nickel, zinc, cobalt, chromium and aluminium which may all be contaminated with arsenic. Valuable-metal solutions in the context of the invention are aqueous systems with the listed valuable metals in ionic form which, in addition to arsenic, optionally contain antimony, bismuth or iron as impurity elements in the form of their ions in varying quantities. The impurity elements are to be removed from the valuable-metal solutions so that the valuable-metal solutions may then either be directly used as such or may be subjected to electrolytic treatment to recover the valuable metals or their salts.
STATEMENT OF RELATED ART
Solutions of valuable metals are often obtained from ores by digestion or leaching with aqueous systems. Recently, however, the processing of fly dusts or the recycling of spent valuable-metal products has also played a significant role in the preparation of valuable-metal solutions. Irrespective of how the valuable-metal solutions are formed, efforts have always been made to remove the impurity elements present, namely arsenic and optionally antimony, bismuth or iron, from the solutions so that pure valuable metals are obtained. Apart from the intended improvement in the quality and quantity of the valuable metals, it is also desirable to recover the impurity elements for economic and ecological reasons.
Numerous solvent extraction processes in which arsenic and, in some cases, also antimony are removed from valuable-metal solutions are known from the prior art in connection with the electrorefining of copper. Thus, DE-A-26 03 874 describes a process for the removal of arsenic in which the aqueous electrolyte solution is contacted with an organic phase containing tributyl phosphate, the arsenic being extracted into the organic phase. It is known from EP-A-106 118 that arsenic can be removed from copper electrolyte solutions with organophosphorus compounds, such as trioctyl phosphine oxide, in organic solvents, such as kerosine. To work up the arsenic, it is proposed that aqueous hydrochloric acid or other mineral acids be contacted with the organic arsenic-containing phase. In addition, DE-A-34 23 713 describes a process for the removal of arsenic from sulfuric acid copper electrolytes in which aliphatic alcohols containing 6 to 13 carbon atoms, preferably 2-ethyl-1-hexanol, in organic phase are used as the extractants. In this process, a large part of the arsenic can be removed in six extraction cycles.
However, all the processes mentioned above are attended by disadvantages. They require an extremely high concentration of acid for efficient arsenic extraction which, in practice, is achieved by increasing the sulfuric acid concentration of the copper electrolyte solution by concentration from 100 to 250 g/l to around 500 g/l. With sulfuric acid concentrations as high as these, considerable quantities of sulfuric acid are extracted into the organic phase with the impurity elements. To remove the sulfuric acid, several washing stages have to be incorporated which involves unwanted extra expenditure. In addition, the organophosphorus extractants are not sufficiently stable at such high acid concentrations, resulting during extraction in losses of effect of the extractant and in unwanted crud formation.
The difficulties illustrated with reference by way of example to the removal of impurity elements from copper electrolyte solutions also apply to contamination by the impurity elements in aqueous solutions of the other valuable metals already listed. In individual cases, the removal of a certain impurity element may be more important than the removal of other impurity elements within the group.
The described disadvantages attending the removal of
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patent: 4834951 (1989-05-01), Kehl et al.
patent: 5039496 (1991-08-01), Kehl et al.
patent: 5174917 (1992-12-01), Monzyk
Kehl Ralf
Schwab Werner
Gorgos Kathryn
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Mee Brendan
Span Patrick J.
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