Solvent Extraction of Gold 

Traditional gold recovery and refining methods employ a variety of mechanical and chemical operations to produce precious metals of commercial purity. Depending on the quality of the gold source and its composition, any one of several different refining methods can be used to recover and refine gold to high purity.

The use of solvent extraction to recover metals is a greatly underutilized technology. Solvent Extraction can provide significant reductions in operational costs in comparison to more traditional methods of metals recovery and refining.

Our CDE 9 Gold collector is:

• Biodegradable and not biotoxic
• Easy to handle-low volatility (bp. 254.6C); low flammability in part because of a high flash point (118C)
• Low solubility in water
• A process that delivers nearly quantitative yields of high purity gold
• Very selective for gold chloride
• Suitable for small and large operations
• Readily recyclable
• Easily integrated into existing refining processes

 Process Summary

• Digest your ore with CDE Leach converting any AU complexes to Au(lll)Cl

• Extract the AuCl from the pregnant solution as chlorauric acid with CDE 5

• Reduce the AU(lll) with CDD9 to Au⁰ (metallic gold)

• Recycle the CDE 5 back into the process

Materials Required:

• Pregnant Solution of CDE Leach that has digested enough of your ore to get a yellow/orange/gold color. (See our leaching video and primer.)

• Hydrochloric Acid Solution (HCl Sol). You make this solution by purchasing 38% Muriatic Acid (available from most hardware stores) and dilute three times with distilled or reverse osmosis water. If you buy one quart of Muriatic Acid, you will make 4 quarts of HCl Sol.

• # 42 Whatman Filters or equivalent

• CDE 5 Gold Collector

• CDE 9 Gold Stripper

Definitions:

• HCL Sol – Hydrochloric Acid as made according to directions above.

• PGM’s – Platinum Group Metals

• PART – When testing we use units of 25 ml. We have substituted the word part for each 25ml we use. This will allow you to adjust the arithmetic for your setup no matter the size.

• This can readily scale-up to any size set-up

Equipment Required:

• Separatory Funnel

• Equipment Stand

• Rings and holders 

• Two funnels

• One beaker marked “Gold”- 400 mL

• One beaker marked “Step 2”

• One beaker marked “Step 2”- 400 mL

• Magnetic Stirring Hotplate and stir bar.

Procedure:

1.  Prepare 1 parts of clear leach by filtering pregnant solution through a # 42 Whatman filter into the beaker marked Gold. [NOTE: You may rinse the debris from the filtering back into your original leaching container to retain any unleached metals.]

2.  Add 1 parts of distilled water and stir manually (stirring rod or agitating the beaker)

3.  Add 2 parts of CDE 5 Gold Collector.

4.  Place beaker on a magnetic stirring hotplate, place stir bar in the beaker and agitate strongly for 45 minutes at 98 degrees F.

 5.  Transfer the solution to a separatory funnel and allow it to settle into two layers. The gold will be in the top layer.

6.  Drain the bottom layer into a beaker marked “Pregnant solution minus Au” and set it aside. [This “waste” liquid will be processed later for possible platinum group metals. The procedure is the same, but the collectors and strippers and different for each metal. Supplies may be purchased from Rocky Ledge.]

7.  Place the CDE 5 into a beaker and add an equal amount of CDE 9 gold separator.

 8.  Agitate vigorously while bringing the solution to 180 F. This could take as long as 90 minutes depending on the volume as well as your heating and stirring equipment.

 9.  As the temperature rises a color change in the liquid will become apparent.

10.  At approximately 180 F any gold present will appear to be “black” particulate floating in the solution. When the color is no longer modifying stop the heating and stirring.

11.  Place the solution into a separatory funnel and allow to separate.

12.  Drain the bottom solution through a # 42 Whatman filter to collect the gold particulate.

13.  Rinse the particulate from the filter paper into an appropriate beaker. Add a small amount of HCL to the liquid and stir vigorously. 

14.  An amount of the gold will be “in the vortex” created by the stirring. Slowly add isopropyl alcohol—store-bought cheap rubbing alcohol—to the dilute HCL solution. When the mix is approximately 50/50 the gold will fall out of the vortex and settle in the bottom.  

15.  Air dry the powder in a protected area. You can be assured the material remaining is an ultra high quality gold in sponge form. This sponge gold is sale-able as it is.

16.  Contact Rocky Ledge Mining Supply for further information. We can be a broker for your sponge gold under certain circumstances.