Formulations

Four basic reagent formulations are used in the SX industry, each derived from one of the hydroxyoximes discussed previously: 

• Modified aldoximes
• Aldoxime:ketoxime blends containing no modifier
• Ketoxime
• Modified aldoxime:ketoxime blends

The choice or use of the formulation is dependent upon a number of operational factors. Syensqo is able to assist operations in choosing the optimum formulation to meet customer requirements. The following provide additional detail and background on how the formulations may be used.

Modified aldoximes

Aldoximes are called "strong" reagents because they extract copper even at low pH and/or high Cu tenor. However, aldoximes on their own are rarely used as copper reagents due to the difficulty in stripping copper from the ligand, under typical stripping conditions.

To enable the effective stripping of aldoximes, modifiers are added to weaken the complex. These alter the strength of the hydrogen bonds stabilizing the aldoxime/metal complex, which allows the copper to be removed more easily.

By varying the amount and type of modifier relative to the oxime, it is possible to optimize the formulation strength to match circuit conditions/needs. The correct modification will produce good stripping characteristics that will maximize net copper transfer, resulting in an efficient extraction of copper from the leach solution.

Many modifiers have the ability to affect the strength of an oxime formulation. Essentially, any molecule that can form a hydrogen bond (acceptor or donor) with the oxime can act as a modifier. However, the choice and amount of modifier (or modifier blend) relative to the oxime is critical to reagent stability and to the metallurgical and physical properties of the reagent.

Syensqo has developed and patented a highly branched ester that has become the SX industry's most common modifier. Other modifiers currently used include alcohols, esters, and ketones. 

Due to their flexibility and versatility, there has been a trend in the industry to use modified aldoximes allowing operations to take advantage of optimized formulation strength, low entrainment, low consumption, and high Cu:Fe selectivity.

Ketoxime

Ketoxime is called a "weak" reagent because it exhibits poorer extraction capacity than other reagent classes, especially from low pH or high copper leach solutions. Ketoxime is therefore rarely used on its own. However, ketoxime can be stripped more easily.

Aldoxime: ketoxime blends

Aldoxime:ketoxime blends are still widely used in the industry, although the use of this type of formulation has declined over recent years as operators have switched to modified formulations.

Modified aldoxime: ketoxime blends

These formulations (Syensqo's ACORGA OPT series of extractants) provide significant metallurgical advantages over aldoxime:ketoxime blends when the right type and concentration of modifier is selected. Adding the proper amount of modifier optimizes the aldoxime portion of the blend in the same manner that it modifies unblended aldoxime products. The inclusion of a modifier is beneficial since ketoxime does not significantly modify the aldoxime. Inclusion of the right modifier at the proper concentration greatly improves Cu transfer and Cu:Fe selectivity.

Reagent summary

The range of solvent extraction reagents based on the two primary oxime molecules (C9 aldoxime and C9 ketoxime) presents SX plants with a number of options. Through the proper use of modifiers, it is possible to customize a reagent formulation to meet the demands of a circuit configuration/feed. This chosen formulation should optimize recovery, production, selectivity, stability, and the physical characteristics of the organic.  The optimum strength of the formulation is dependent on a number of factors, these should be discussed with your Syensqo representative and a customized formulation may be tailored for your needs.

ACORGA® Product Line