Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group ib metal
Reexamination Certificate
1999-09-02
2001-01-23
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group ib metal
C252S184000
Reexamination Certificate
active
06177055
ABSTRACT:
FIELD OF THE INVENTION
This application relates to a process of extracting copper from aqueous solutions containing copper by contacting the aqueous solution with a solution of a water insoluble hydroxy aryl oxime (ketoxime or aldoxime or mixtures thereof) in a water insoluble and water immiscible organic solvent so as to extract the metal from the aqueous solution into the organic phase in the form of a chelate of the metal with the hydroxy aryl oxime and then separating the organic phase loaded with the metal from the aqueous phase by virtue of the immiscibility of the organic phase and the aqueous phase. The metal can then be recovered from the organic phase by stripping with an aqueous acid solution followed, for example, by electrowinning.
The general process of extraction of copper from aqueous solutions such as acid solutions and the recovery of the metal by stripping of the organic phase followed by electrowinning is taught in U.S. Pat. Nos. 4,507,268; 4,544,532; 4,978,788; and 5,281,336 the entire contents of which are hereby incorporated by reference.
The reaction leading to the metal chelate compound also forms acid and causes a lowering of the pH. This reaction is reversible and proceeds to an equilibrium point which will favor formation of the chelate compound as the pH is increased. The metal salt-containing aqueous solutions from which metal e.g. copper is to be extracted will frequently be leach liquors obtained by extracting metal ores with acid and will in some cases have a low pH. Since the amount of chelate compound formed at equilibrium is lower as the pH is decreased only those o-hydroxyaryloximes which have a strong chelating power will be able to achieve a high degree of extraction from those aqueous leach liquors having very low pH or high copper content.
The advantage of high copper extraction shown by these strongly chelating oximes is to some extent offset by the large amount of copper which remains as chelate in the solvent after stripping with acid of convenient strength. While this residual copper as chelate is not lost since it can be recycled to the extraction stage, a reduction in the amount of residual copper chelate would, in the absence of any comparable reduction in the degree of copper extraction from the aqueous solution, afford an improvement in the overall efficiency of the process.
UK Patent No 1549615 teaches that the amount of copper removed in these cases from the solvent phase in the stripping stage is significantly increased if the solvent phase contains a “strip modifier” such as a phenol. This patent also teaches that certain aliphatic alcohols, such as tridecanol have similar beneficial effects.
Strip modifiers will not only influence the strength of the extractant, but can also affect the hydrolytic stability, the selectivity of copper extraction over iron extraction, the level of entrainment, the kinetics of the extraction and stripping stages and the generation of crud. A suitable modifier will therefore often be the result of a compromise.
‘Crud’ is a term applied to undesirable extraneous matter formed at the organic-aqueous interface or in the organic phase in the settler compartment of mixer settlers used in the solvent extraction process. It is usually an oil-water emulsion stabilized by the presence of finely divided solid material that may be either alumino silicates present in the feed, or colloidal silica precipitated during the solvent extraction operation. It can accumulate in sufficient quantities to seriously reduce the working volume of a settler leading to flooding. Where large quantities are produced it has to be removed and the emulsion broken by centrifuging. Crud can also be a source of loss of reagent .
U.S. Pat. No. 5,281,336 describes the use of highly branched chain aliphatic or aliphatic-aromatic C-10 to C-30 esters or C-14 to C-30 alcohols which give unexpected benefits as strip modifiers. By “highly branched” is indicated as the ratio of the number of methyl carbons to non-methyl carbons is higher than 1:5. Good and unexpected selectivity for copper over iron can be achieved and the above disadvantage concerning crud formation and entrainment level can be overcome by using such compounds, particularly very highly branched derivatives as compared to straight chain compounds.
SUMMARY OF THE INVENTION
The surprising discovery has now been made that copper extractant formulations based on linear diesters perform similarly to formulations based on branched diesters. This is surprising in light of the assertions made in U.S. Pat. No. 4,978,788 and 5,281,336 that linear esters do not perform as well as do highly branched esters in terms of entrainment and crud formation.
Thus, the invention is a process for recovery of copper from an aqueous solution containing copper values comprising the steps of: (1) contacting the aqueous solution with water insoluble extraction reagent composition comprising an aldoxime, a ketoxime or combinations thereof and a diester or polyester of an unbranched monocarboxylic acid or unbranched dicarboxylic acid and an unbranched mono- or diol to extract at least a portion of the copper values into the organic phase; (2) separating the resultant copper pregnant organic phase from the resultant copper barren aqueous phase; and (3) recovering the copper values from the copper pregnant organic phase.
DETAILED DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”.
Thus, in its broadest scope, the present invention is directed to a process of recovering copper from an aqueous solution containing copper values comprising:
(a) contacting the aqueous copper bearing solution with an organic phase comprising a water insoluble and water immiscible organic solvent solution of an extraction reagent formulation to extract at least a portion of the copper values into the organic phase;
(b) separating the resultant copper pregnant organic phase from the copper barren aqueous phase; and
(c) recovering the copper values from the copper pregnant organic phase:
wherein the extraction reagent formulation comprises an hydroxy aryl oxime and an equilibrium modifier in which the modifier is a linear diester or polyester of a dicarboxylic acid and an alcohol, or diol.
The copper values are preferably recovered from the organic phase by
(d) contacting the copper pregnant organic phase with an aqueous acidic stripping solution, whereby copper values are stripped from the organic phase into the aqueous acidic stripping solution;
(e) separating said aqueous acidic stripping solution from said organic phase; and
(f) recovering the copper from said aqueous acidic stripping preferably by electrowinning;
The extractant reagents for use in the extraction of copper step include those containing one or more hydroxyaryl oxime extractants of the hydroxy aryl aldoxime or hydroxy aryl ketone oxime type. A general formula for such oximes is formula (I) below;
in which A may be:
(i)
(ii) R′″ or
(iii) H
where R and R′ may be individually alike or different and are saturated aliphatic groups of 1-25 carbon atoms, ethylenically unsaturated aliphatic groups of 3-25 carbon atoms or OR″ where R″ is a saturated or ethylenically unsaturated aliphatic group as defined; n is 0 or 1; a and b are each 0, 1, 2, 3, 4, with the proviso that both are not 0 and the total number of carbon atoms in R
a
and R′
b
is from 3 to 25, R′″ is a saturated aliphatic group of 1-25 carbon atoms or an ethylenically unsaturated aliphatic group of 3 to 25 carbon atoms, with the proviso that the total number of carbon atoms in R
a
and R′″ is from 3-25.
Preferred compounds where A is (i) above are those in which a is 1, b is 0, R is a straight or branched chain alkyl group having from 7 to 12 carbon atoms and where R is attached in a position para to the hydroxyl group. Among those, the more prefer
Grinstein Reuben
Olafson Stephen M.
Sudderth R. Brantley
Virnig Michael J.
Wolfe George
Bos Steven
Drach John E.
Henkel Corporation
Span Patrick J.
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