Methods of metal extraction using oximes

#The present invention relates generally to the field of extractive metallurgy. In particular, the present invention relates to metal solvent extraction methods and reagents.

#Copper and its metal alloys have been used for thousands of years. The importance of copper, as well as a variety of other metals, has led to a continuing search for more efficient and productive procurement methods. One method of copper extraction is a process of leaching, coupled together with solvent extraction, and finally copper production by electrowinning. Leaching is typically carried out by stacking the ore in piles on a prepared pad or by stacking it in a small canyon. A solution of sulfuric acid is then applied, and as the acid solution is trickled down through the heap, copper is dissolved from the rock. The resultant copper-bearing solution (pregnant leach solution or PLS) is collected, and then transferred to the solvent extraction plant, where it is contacted by vigorous mixing with an organic solution comprising an extractant dissolved in a kerosene-like hydrocarbon diluent. In this extraction, the copper (as cupric ion) is transferred to the organic phase, where it forms a chelate-type complex with the extractant. After contact, the mixture of aqueous and organic is allowed to separate. The copper-depleted aqueous solution (raffinate) exits the solvent extraction plant, and the organic is transferred to stripping, where it is contacted with a strong acid solution. In stripping, the cupric ion is transferred to the aqueous phase and protons are transferred to the organic. The now copper-depleted organic is returned to extraction for re-use. The copper-rich aqueous strip solution (pregnant or rich electrolyte) is transferred to electrowinning. In electrowinning, copper is plated as metal from solution at the cathode, and water is broken down at the anode to form oxygen and protons as acid. Depending on the climatic conditions at the site, the size of the ore heap or dump, and the irrigation rate, the temperature of the PLS entering the plant could range from about 10° C. to about 30° C. As a result, temperatures in extraction typically range from about 20 to 25° C., and temperatures in stripping may range from about 30 to 35° C. The temperature in the electrowinning cells is typically about 45° C., incorporated herein by reference. This acid leach process may also be used for other metals. Additionally, leaching with ammonia may be carried out analogously. Combinations of ammonia with an ammonium salt, such as ammonium carbonate or ammonium sulfate, have been used on a commercial scale to leach copper metal (recycling applications), copper oxide ores and copper sulfide ores. Ammonia leaching can be applied other metals such as nickel and zinc as well.

#Reagents useful in such processes should generally possess certain qualities. Examples of important features are the rates of reaction, phase separation and reagent stability. A detailed discussion of the useful characteristics in a liquid ion exchange reagent is available in Swanson, “Liquid Ion Exchange: Organic Molecules for Hydrometallurgy” presented at the International Solvent Exchange Conference September 1977.

#FIG. 1 is a graphical representation of the level of copper in several stripped organic solutions containing various ratios of 3-methyl ketoxime and 3-methyl aldoxime.

#Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways.

#Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

#The term “NSAO” as used herein is used interchangeably with 5-nonylsalicylaldoxime, and refers to a compound having the structure: