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Gold.refinery

Well-known member
Joined
May 2, 2022
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153
Location
EU
Hello

Can you help me about the recovery of gold and silver from silver chloride after Refining operations?

After finishing the gold refining operation, we have some silver chloride in which some gold (about 10-15% ) is trapped. It can be done according to the following steps:
first I recover the silver in the following way, then I dissolve the obtained silver in nitric acid, the gold is extracted, the silver chloride is formed again and the silver is recovered by the following method.


NaOh , Sugar method :
I read the posts and realized that
to convert 1000 grams of silver chloride,

I must first dissolve it in 2 liters of water.
Then add 600 gr of NaOH slowly, and mix well to form silver oxide (stirring well is important)
Then add the saturated food sugar solution (approximately 400 g of sugar) and stir well until Do not increase the temperature by adding syrup.

Am I right so far?
Please Complete if there is a point.

Now I have some questions,
first: what to do to wash silver from NaOH?

How to dry silver easier?

I have experienced that it is difficult to melt the silver obtained from this process, and it is not easy to form silver metal.
Should it be melted with sodium carbonate or what do you suggest?
I have an induction furnace.
 
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Silver Chloride do not dissolve in water.
I thought that it was beneficial to use as little water as possible.
I'd pull out as much of the gold as possible first.

There are many posts regarding this topic so search the forum.
 
10-15% gold trapped in silver chloride is exceptionally high. What was the assay of silver in the feedstock?

For converting the silver chloride to metal before you recover the gold I would suggest a simpler method.

Add the siver chloride to a tumbler with some iron and a solution of 10% sulfuric acid. The silver chloride, on contacting the iron will be reduced to metal and the nails will slowly dissolve. By a tumbler you could use a slow spinning bucket sitting at a 45º angle so the solution and the chlorides move slowly exposing the chlorides to the iron. Nails are often used. When the reaction is complete the iron is removed with a magnet and the metallic silver is rinsed and melted.

The reason I say melt the silver is because you will be able to use your XRF to analyze the resulting bar before you dissolve it to make sure you have found the gold you expect. In any kind of production refinery it is good to quantify your values at every step if possible. If you were doing this in a small, hands on shop, you could just dissolve rinse well and remove the iron remaining with the silver and dissolve it in nitric before melting and the gold will remain behind.

Then you again form silver chlorides and process them as you accumulate larger quantities.

Here in the US refiners of intermediate size love 5 gallon buckets. They are a standard size and most important they are all 12" inside diameter. As a result I have developed the attached Excel spreadsheet which bases everything on the depth of silver chloride in the pail. Measured in inches. (My apologies but we Americans for some reason cling to this rather confusing measurement system of feet and inches)

The silver chlorides you generate should always be stored in water, in the dark, and never dried out. Keep at least an inch or so of water over your chloride level in the bucket. When you are ready to process the silver chlorides, make sure the chlorides are level in the bucket and measure the depth of the chlorides in inches. use decimals for less than a full inch like 2.75 rather than 2 3/4"

The program will tell you the weight in pounds of 50% liquid caustic to add (NaOH) and the weight in pounds of something we call Karo syrup here in the US but is also called corn syrup. It is a thick sugar used in cooking and easy to use and buy in larger quantities.

It seems the old forum software allowed me to post spreadsheets here but now it does not. I will see if it is possible to do it and post it whan I can. my apologies.
 

Attachments

  • formulas for chloride conversion.xlsx
    12.2 KB · Views: 14
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With the silver chloride conversion using caustic and sugar, the silver chloride does not dissolve in the water (it won't) but adding the caustic will react the chlorides in the slurry to create silver oxide.

And it is beneficial to have less water, a slurry is sufficient.
 
A few days after the previous refining operation, the silver chloride has dried , unfortunately.
what's the solution ?
The amount of silver in our feed is usually 6% of scrap gold. For example, in 1000 grams of scrap gold, there are 60 grams of silver.
In the previous operation for 2600 grams of gold, approximately 170 grams of dried silver chloride was obtained.

I will be very happy if you explain the method of recovering silver with iron in more detail and the amount of each material.
(step by step please)
(Use iron powder or iron nails)

A friend suggested that I always keep silver chloride in AR solution, then filter the liquid and precipitate the gold. Finally, I recycle silver by iron or sugar/NaOh method.
is it right way ?

This is a good way or, to dissolve the initial silver obtained in nitric, then extract the gold, then re-form the silver chloride.
 
No need for keeping it in AR, just keep it dark and wet.

For the Sulfuric iron method, one of the members here, just used a cast iron skillet/frying pan and added
the Silver Chloride and Sulfuric and stirred it until it was done. The important thing is contact between AgCl and Iron.
The iron can be anything like rebar, nails, nuts, bolts anything Iron.
It need to be wet and have plenty contact with Iron and Sulfuric.

For the dry I'm not entirely sure, but grind it to a powder and smelt it with soda ash has been mentioned.
But this process has losses.
 
For small amounts of silver like 60 or 170 grams it would be easier to use a cast iron frying pan for the source of the iron. Unfortunately a well seasoned pan will not work well as seasoning will prevent the needed contact between the iron and the silver chloride. Get a average sized frying pan and add 10% sulfuric acid until it is about 1" deep in the pan. Add in some silver chloride and move it about with a plastic spatula to contact the silver chloride with the pan and you will see the chloride visibly convert from white chloride to metallic silver. Scoop out the reduced silver and add some more silver chloride and continue. The pan will be slowly dissolving as it reduces the silver but for small lots it is the easiest way.

Since your silver chloride has dried it will. be more difficult to reduce. Soak it in water overnight in an attempt to re-hydrate it before trying this method. Even the caustic sugar method is difficult with dried chlorides.

Sorry for posting this, the old software informed you if some had posted while you were preparing a new post. Apparently this doesn't happen anymore so this is redundant. Thank you Yggdrasil.
 
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4metals said:
For small amounts of silver like 60 or 170 grams it would be easier to use a cast iron frying pan for the source of the iron. Unfortunately a well seasoned pan will not work well as seasoning will prevent the needed contact between the iron and the silver chloride. Get a average sized frying pan and add 10% sulfuric acid until it is about 1" deep in the pan. Add in some silver chloride and move it about with a plastic spatula to contact the silver chloride with the pan and you will see the chloride visibly convert from white chloride to metallic silver. Scoop out the reduced silver and add some more silver chloride and continue. The pan will be slowly dissolving as it reduces the silver but for small lots it is the easiest way.

Since your silver chloride has dried it will. be more difficult to reduce. Soak it in water overnight in an attempt to re-hydrate it before trying this method. Even the caustic sugar method is difficult with dried chlorides.

Sorry for posting this, the old software informed you if some had posted while you were preparing a new post. Apparently this doesn't happen anymore so this is redundant. Thank you Yggdrasil.
Click to expand...
No problem, it still do I think, I sometimes get a pop up.
But can't always access it until after posting.

Your post was way more descriptive so that stands on its own feet:) (Norwegian Jungle Word)
 
Is this a problem if I keep wet silver chloride with dried silver chloride powder in a bucket of water on it?
 
I've had reasonably good "luck" with dry AgCl using the sulfuric acid method, but tumbling in a 5 gallon bucket with heavy ball bearings. It's like a ball mill. You get good grinding action which breaks down the crystalline structure of the dried AgCl, and provides intimate contact with the iron, in the electrolyte, which causes the reduction.
 
Snowman,

The weight of the iron balls is the key in your description. The use of the 5 gallon bucket means you have an angled tumbler keeping the pail at a 45° angle to avoid spilling. That is excellent but often difficult for members to either imagine, fabricate, or obtain. It would be a service to all if you provided a photo of the mill.
 
In time. I went out to the shop to photograph it, but the state of the hood is not one I'm comfortable posting...ha

I utilized a 1/4 hp DC motor with a 10:1 gear reducer that is bolted to a structure welded out of 3/4" square tubing. The gear reducer has a hub with a large aluminum plate on it. I bolted a 2 gallon bucket to the plate using very large fender washers. I then just drop another 2 gallon bucket into the first one that has my material in it. My plate is large enough to utilize a 5 gallon bucket, but I lack a buchner big enough to really utilize that size and honestly, my back is sick of lifting five gallon buckets...if I add that capacity, I also have a gilson poly drum mixer I will use.

The biggest downside has been the speed control. If you overspeed it, you make a mess.

The weight of the balls is of extreme importance, too big, they just roll, to small, they don't grind well.
It actually works better with odd shaped scrap, but it's a tradeoff as it tears buckets up.
 

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