We have made the leaching process simple, safe, and profitable.

SOME FACT ON LEACHING

Cyanide Leaching - most medium to large mining operations use cyanide leaching. A very good method for recovering gold and other metals, but the pH has to be watched as it can quickly turn into a poisonous gas. This process is under great pressure from environmental and governments groups.

Chlorine Leaching - was first commercial gold extracting agent in the late 1800's. It was replaced with cyanide extraction as it was cheaper and easier for the miners to use.

Bromine Leaching - works very well, but is a bit expensive. Bromine is rather nasty stuff to handle and store in its elemental form.

Iodine Leaching - a very easy process, but too expensive for commercial use due to the cost of Iodine, a element extracted from seaweed. Iodine leaching uses Lye, but is an attractive home or lab way to recover gold because it is simple, safe and the gold is very easy to recover

RECOVERY FROM LEACHING

Leaching produces liquid metals which no one knows for sure what it is or how much there is. Not very salable in this form. There are several methods to recover the metals.

1. 1. Activated Carbon, the carbon is slurred into a column of plastic and the pregnant solution is allowed to flow through it. The column is then stripped with chemicals and smelted. Note: Charcoal briquettes will not work.

2. 2. Ion Resin is very reliable and works almost like carbon. The pregnant solution is mixed with resin then passed through a filter. The gold sticks to the filter which is smelted. We use this method this method with our manufactured Super Resin to enhances the recovery over most commercial grade resins.

Recovering Metals From Resin

The use of ion-specific resins for selective metals recovery is an efficient way to divide up the soup when leaching complex ores. The alternative, chemical precipitation, is slow, expensive and can be extremely dangerous.

Some resin suppliers suggest methods of stripping the metallic ions from the resin which is a cumbersome procedure at best. Experiences with resin stripping suggest a loss of loading capacity diminishing by half each time the resin is stripped, i.e., 100% loading the first round, 50% the second and so on. This varies somewhat by manufacturer. The decrease in loading capacity relates to the oxidation of the resin beads and subsequent loss of functional surface area.

Our preferred method is to consume the resin after each loading since we only employ acidic leach we do not have to eliminate the HNO3 from the solution. This step itself is a tremendous productivity gain.

Using the loaded resin:

1. Pour the pregnant solution into a Pyrex pie plate or similar and spread the loaded resin out in an even layer.

2. Place in a furnace or oven heat the resin to 600o F, stirring occasionally to promote drying.

3. Raise the temperature to 1000oF and cook until the resins are completely charred black. It will be gold color if the resins are totally saturated with gold.

4. Raise the temperature to 1400oF and allow a small amount of air or oxygen to flow across the beads until all of the beads have been reduced to gray ashes. In the case of testing quantities of small amounts, brush the gray ashes into a suitable cupel, add an amount of lead about 30 times the weight of the ashes.

5. Place in a furnace at 1750oF until all the lead is gone and a bead is left. A torch assay method may also be used. Smelting is appropriate in the case of larger quantities

It is recommended NOT to attempt recovery by smelting the resins directly to recover the maximum values. Direct smelting will cause a loss of a portion of the recovered metals. After all of the effort to get to this point, it does not make sense to hurry and throw some of the values away.

3. Cementation - Precipitation in chemistry as relates to mining means making a metal that is in solution come out of solution and (usually) settle to the bottom of the container. Generally, zinc or some other base metal such as aluminum or iron is used to cause this reaction to occur. This is called the replacement or cementation process. The zinc (aluminum or iron) will go into the solution as the precious metal comes out of the solution, hence the term replacement process.

Precipitating Precious Metals with Zinc

Using zinc in acid solutions to precipitate precious metals, including platinum, can be quite tricky. This applies to Aqua Regia as well as the acid leaches. Precious metals are finicky. Many people have thrown ounces of gold, silver or platinum away because nothing came out of solution when they added zinc, or because they had already added zinc several times and were sure nothing was left.

Recovery only comes out of acid solutions in a fairly narrow pH range when zinc is the precipitator, generally between 4 and 5, rarely higher. Zinc raises the pH right up through the range that the precious metals will precipitate out of the solution. If you are lucky the metals will all come out and drop to the bottom as the pH rises upwards toward 7.

A more predictable method is to use zinc chunks. Unlike zinc powder, chunks slowly dissolve bringing the pH up gradually. The pH passes through the precipitation zone it usually get all of the gold if the oxygen has been removed first.

Heat the solution without boiling for a few hours or simply let it sit for several days. Then do the precipitation. Once the metals have precipitated use a weak HCl solution to dissolve the extra zinc, then cupel or smelt.

Note that zinc causes cyanide solution to move towards 7, cyanide leaches are generally around 10 pH.

If powdered zinc is used the pH may raises too quickly to allow the precious metals to precipitate out of the solution. If this happens simply add acid a few drops at a time to maintain the pH in the desired 4 to 5 pH range.

A method popular used by the old-time miner was to fill a box with zinc shavings and slowly run the pregnant cyanide solution over the shavings. The gold would attach, or cement itself to the zinc, or at least that was what was supposed to happen. Often it did not and all the efforts was lost!

Cyanide must have oxygen in order to dissolve the gold, but the oxygen also prevents the zinc from causing the gold to come out of solution. Thus, the reason many old zinc box operations failed.

A method to remove free oxygen from a cyanide solution is to heat the solution for several hours without boiling it, or let it sit for several days in a closed container with just a small opening. The zinc can then be added to get the gold to precipitate. Its best in this case to use powdered zinc, stir it for a while, filter it off, and wash the precipitate thoroughly with distilled water. After the rinsing add a weak hydrochloric solution -1 part HCl to 10 parts H2O to the precipitate to remove the any zinc in the residue. The precipitate can then be cuppelled or smelted.

Make very sure that no acid comes in contact with any cyanide. The gas that forms from an acid/CN combination is DEADLY with one breath!

PROBLEMS: If you have had trouble with zinc powder and wondered why the metals did not come out, it could be you did not use enough zinc; or you used too much too fast; or you did not get the oxygen out of the pregnant solution. If you used zinc chunks, check to see if they are still bubbling hard you have not waited long enough or you did not add enough zinc chunks. When finished the zinc chunks will be bubbling very slowly. Take out a little bit of the liquid and add a small amount of zinc powder. Anything other than a very slight bubbling indicates more time, or more zinc, or both.

Silver Recovery

Super Leach will out perform any other leaching system in recovering Platinum and Gold. However, it does have a down side when it comes to silver which will be lost. Generally, the additional recovery of Platinum or Gold will more than compensate for any lost Silver.

When a ore contains mostly Silver values with little Gold it is recommended to recover the Silver by another method. Silver is relative easy to recovery and two methods are listed here:

Recovering Silver with Household Products

1. Place your ore in a plastic or glass container and add Nitric Acid. Allow to set 30 minutes per oz. and then pour off acid.

2. Add table salt in the Nitric Acid until it stops making white clumps.

3. Pour off acid add baking soda.

4. Rinse in water then add Red Devil Lye until it becomes black.

5. Rinse with water and then add Karo syrup until the black turns silver and smelt.

Recovering Silver with Chemicals

1. Place your ore in a plastic or glass container and add Nitric Acid. Allow to set 30 minutes per oz. and then pour off acid.

2. Add hydrochloric acid allow 2 hours per oz. or let it set overnight. Pour off acid and filter to an clear emerald green.

3. Add 1 quart of boiled tap water. Add urea to the water slowly till it stops foaming.

4. Then heat and add 1 oz. of storm that will change it to a muddy brown. Let it settle and pour the clear amber acid. Add tap water to the mud and stir, then allow it to settle. Repeat this 3 or 4 times.

5. Rinse with aqua ammonia and then rinse that with distilled water. Place it on a hot plate and melt the mud into a powder. Place the powder into a tissue and soak with alcohol and smelt.