Solvent Extraction using Ferro Chemical Butyl Diglyme Ferro’s BUTYL DIGLYME is very selective in removing gold from various anode slimes using highly effective solvent extraction techniques. The discussion below is a very brief summary of the gold extraction process using Ferro BUTYL DIGLYME. For a complete brochure, please contact Ferro Customer Service at (800) 321-9942. Introduction While the use of solvent extraction to recover metals is not new technology, it is an under-utilized technology even though there is ample evidence and experience validating this technique. In many cases, solvent extraction can provide significant reductions in operational costs in comparison to more traditional methods of metal recovery and refining. Polyethers, such as glymes, form complexes with numerous metals.1-7 This property can be applied to the recovery of transition and noble metals from ores and process streams. One of these commercially proven applications uses butyl diglyme (dibutyl carbitol, E444) to extract gold(III) chloride from acidic aqueous solutions. Sources of gold include various ores, concentrates, anode slimes, cathode sludges, electrolytic plating operations and gold coated electronic parts. Butyl diglyme extraction is both a cost effective and an environmentally friendly metal recovery process. Advantages: The advantages of using a solvent extraction system based on butyl diglyme (dibutyl carbitol or E444 ) can be summarized as follows: I. Health, Safety and Environment: Butyl diglyme is a non-HAPS (Hazardous Air Pollutants) solvent with an LD50 of 3900 mg/kg. Butyl diglyme is biodegradable. The bacteria used in aerobic digestion of industrial waste can be acclimated to digest butyl diglyme under mildly acidic conditions. Butyl diglyme is easy to handle: low volatility (bp. 254.6C); low flammability in part because of a high flash point (118C); Butyl diglyme has low solubility in water (0.3 wt% or ~ 3g/L at 20C). II. Economics: Butyl diglyme delivers nearly quantitative yields (>99%) of high purity gold ( 99.9 to 99.99wt%). Butyl diglyme is very selective for gold (III) chloride. Butyl diglyme provides a clean and facile separation of gold(III) chloride from the chlorides of the platinum group metals (e.g. palladium or platinum). Butyl diglyme is suitable for small or large scale operations. Butyl diglyme is easily recycled with minimal material losses without degrading its extracting performance. No major reprocessing is necessary for recycling. The amount of butyl diglyme consumed in this extraction process is reasonable. Butyl diglyme extraction technology is easily integrated into existing refining processes with low capital expenditures. Butyl diglyme energy requirements14 are 0.3% of those required for traditional electro/pyrolytic processes. Butyl diglyme greatly reduces the amount of gold A locked-up@ during a processing cycle. Butyl diglyme extraction is a well documented technology. Butyl diglyme is readily available in commercial quantities. Process Summary: There are four steps necessary (Figure 1) for a gold extraction process based on butyl diglyme: Oxidative leaching converts crude metallic gold or gold(I) to an aqueous solution of gold(III) chloride. Solvent extraction selectively transfers the gold (III) chloride as chloroauric acid from the aqueous solution into the butyl diglyme phase. A wash of this organic extract with dilute HCl removes other metallic impurities. Reduction of gold (III) to metallic gold is accomplished with a variety of chemical agents that convert the solubilized gold (III) to a solid form of metallic gold which is collected and then cast into ingots. Recycle of the butyl diglyme back into the process with minimal processing.