Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group ib metal
Reexamination Certificate
1997-11-21
2001-04-03
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group ib metal
C423S099000, C423S139000, C252S184000, C205S581000, C205S590000, C205S605000
Reexamination Certificate
active
06210647
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an improvement in the process for recovery of metals from aqueous ammoniacal solutions wherein the metal values in the aqueous ammoniacal solution is extracted by contact with a water insoluble extractant solution in a water immiscible hydrocarbon solvent and subsequently stripped with an aqueous acid solution to strip the extracted metal values from the water immiscible organic hydrocarbon phase, the improvement wherein the extractant organic phase contains an ammonia antagonist which is a hydrogen bond acceptor, as distinguished from a hydrogen bond donor. The use of these ammonia antagonists, with either phenolic ketoxime or aldoxime extractants results in a significant reduction in chemically loaded ammonia from the aqueous ammoniacal solution containing the metal values.
In the typical extraction process of a metal from an aqueous solution containing the metal values, the aqueous solution containing the metal values is contacted by a solution of a water insoluble extractant capable of extracting the desired metal, in a water immiscible hydrocarbon solvent. After contact for a sufficient time to extract at least a portion of the metal values, the hydrocarbon solvent phase, now loaded or containing the extracted metal values, is separated from the aqueous solution phase from which the metal values have been extracted, due to the immiscibility of the organic and aqueous phases. The loaded organic phase is then typically contacted with an aqueous stripping solution thereby forming two phases again, (a) an aqueous strip phase, now containing metal values stripped from the organic extractant phase, and (b) an organic phase from which the metal values have been stripped. Again the organic and aqueous phases are separated due to immiscibility of the phases. The metal is then recovered from the metal loaded aqueous strip phase, by conventional means, such as electrowinning, precipitation or other means suitable to the particular metal, generally electrowinning being the preferred recovery means.
Both acid and ammoniacal aqueous solutions have been employed as stripping solutions in the past, one commercial process in the recovery of nickel employing an ammoniacal aqueous stripping solution.
The organic extractant currently employed commercially in extraction of metals such as copper, nickel and zinc are the phenolic oxime extractants. In the process, particularly with aldoxime extractants, it is often desirable to include in the organic extractant phase an equilibrium modifier, to provide for the most efficient extraction and “net transfer” of the metal being recovered. In the process there is a transfer of metal in the extraction stage from the aqueous feed solution to the organic extractant phase, followed by a second metals transfer from the organic phase to the aqueous strip solution phase, the two metal transfers representing the “net metal transfer” of the process. Effectively “net transfer” can be determined by observing the difference between the extraction isotherms and the strip points.
Typically equilibrium modifiers employed with the phenolic oxime extractants in the process have generally been various alcohols and esters.
DESCRIPTION OF THE INVENTION
In this description, except in the operating examples or where explicitly otherwise indicated, all numbers describing amounts of ingredients or reaction conditions are to be understood as modified by the word “about”.
Briefly, the present invention is an improvement in the process of extraction of metals from aqueous ammoniacal solutions in which an aqueous ammoniacal solution containing the metal values is:
(1) contacted with an extractant reagent comprised of a water insoluble oxime extractant for the metal dissolved in a water immiscible hydrocarbon solvent to extract metal values from the aqueous ammoniacal solution to provide an organic phase containing the metal values and an aqueous phase from which metal values have been extracted;
(2) separating the immiscible organic phase containing metal values from the aqueous phase;
(3) contacting the organic phase with an aqueous stripping solution to strip metal values from the organic phase into the aqueous stripping solution;
(4) separating the immiscible aqueous stripping solution now containing metal values from the organic phase from which metal values have been stripped; and
(5) recovering the metal values from the aqueous stripping solution.
In the past in such a process where the original feed or leach aqueous solution containing the metal values is an aqueous ammoniacal solution, the process resulted in significant amounts of ammonia to be loaded along with metal values into the organic phase. The ammonia must then be removed from the organic phase, at a cost of ammonia the system and a cost of acid required to neutralize the ammonia carried in the organic phase by a scrub section.
It has now been discovered that when an ammonia antagonist is employed along with the oxime extractant, which may also act as an equilibrium modifier, to provide the most efficient net transfer of the metal values in the overall extraction process, particularly where the extractant is a strong extractant such as an aldoxime extractant for the metal, a significant reduction in the chemically bonded ammonia results, thereby providing reduced cost of operation, minimizing, if not eliminating, the scrubbing of the organic phase with a weakly acidic solution. Thus, the ammonia antagonist is employed in an amount effective to provide as significant reduction in the ammonia in the organic phase also when employed in an effective amount with a ketoxime extractant. The ammonia antagonist is a compound which may be characterized as a pure hydrogen bond acceptor compound. By “pure hydrogen bond acceptor” is meant that the compound is “only” a hydrogen bond acceptor compound in contrast to compounds which are hydrogen bond donors or a mixed hydrogen bond donor and acceptor. Mixed hydrogen bond donor and acceptor compounds can be illustrated by alkyl phenols, such as nonyl phenol or alcohols such as tridecanol, each of which is a mixed hydrogen bond donor and acceptor. While the ammonia antagonist useful with aldoxime strong extractants, in that they may also act as an equilibrium modifier to provide efficient net transfer, the ammonia antagonist is also useful with the weaker oxime extractant, such as the ketoxime extractants, in that significant reduction in ammonia transfer to the organic phase occurs, though equilibrium modifier properties may not be necessary in the case of the ketoxime extractants. Thus, in the improved process of the present invention, there are employed ammonia antagonist compounds which are “non-hydrogen bond donating” and are only “hydrogen bond accepting” compounds.
It was found that in the case of Ni, the use of an ammonia antagonist, which is only a hydrogen bond acceptor modifier, such as 2,2,4-trimethylpentane-1,3-diol diisobutyrate, surprisingly resulted in about a 50% reduction in the amount of ammonia transferred relative to the Ni.
Similarly the improvement of the present invention is applicable to other metals capable of extraction by oxime extractants, particularly copper and zinc where the extraction is carried out from an aqueous ammoniacal solution and the organic phase is subsequently stripped with an aqueous acidic stripping solution.
The ammonia antagonists for use in the present improvement are those organic hydrogen bond acceptor compounds containing one or more of the following organic functionalities: ester, ketone, sulfoxide, sulfone, ether, amine oxide, tertiary amide, phosphate, carbonate, carbamate, urea, phosphine oxide, and nitrile and having greater than 8 carbon atoms, up to about 36 carbon atoms and a water solubility of less than 100 ppm, more desirably less than 50 ppm and preferably less than 20 ppm. Other than 2,2,4-trimethylpentane-1,3-diol diisobutyrate, which is preferred, illustrative ammonia antagonists which are only hydrogen bond acceptor compounds are: al
Kordosky Gary A.
MacKenzie J. Murdoch
Virnig Michael J.
Wolfe George A.
Bos Steven
Drach John E.
Henkel Corporation
Span Patrick J.
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