Gold refining

[tullo]

hello everybody ,
so i am jeweler and when it comes that time of year cleaning the mess (powder,dust)that i have been working all the time of the polish machine always been interested how do they refine it into pure gold , some of the videos that i watched didn't match the target that i wanted , either they got videos with "Refining gold from karat scrap" or pc parts . can someone tell me step by step how it is made that kind of process with the mess(powder,dust)of the polish machine . peace

 

[Shark]

There is much information on refining jewelers waste, here is one from the forum to get you started.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26384#p279924

Hope it helps.

 

[FrugalRefiner]

The book in my signature line was written for jewelers who wanted to refine their own waste. I think it will help.

I deleted your other two posts. In the future, please post your questions only once.

Dave

 

[tullo]

The book in my signature line was written for jewelers who wanted to refine their own waste. I think it will help.

I deleted your other two posts. In the future, please post your questions only once.

Dave

i understand , sorry

 

[tullo]

There is much information on refining jewelers waste, here is one from the forum to get you started.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26384#p279924

Hope it helps.

thank you

 

[Topher_osAUrus]

If its just a once a year type deal, it may be in your best interest to find someone to do it for you. That depends on a lot of things though.

-the space you can dedicate to refining
--the ventilation system you put in place for said space
-the volume you are doing
-the number of lots per year
-cost of chems and equipment
-time spent on educating yourself, "labor" essentially

And a lot of other things im forgetting.
Im sure as a jeweler you already have a small torch and cruciblea and some other required stuff

I do small lots for a local jeweler every few months, and the only reason he said he wouldnt do it himself in house was because of the corrosive fumes. If you get a fume hood, and a segregated space for chems and waste, it makes sense to process the stuff yourself.

Cost vs benefit
Beside myself, there are other members(who may live closer to you) that do toll refining.

 

[Jordan1]

I have recently started refining gold through inquartation and seperation process using acids and aqua regia. I can only achieve 98 % purity though.

Can someone please give me their advice on refining gold to 99.99% ?

What do you think about the Miller process and electrolytic refining?

 

[g_axelsson]

Jordan1, how do you know it's only 98% pure?

Inquartion followed by aqua regia and precipitation with SMB or copperas followed by proper washing should normally get you closer to 99.95% if done properly.

What is the contamination?

Give us more details or we won't be able to help you.

Göran

 

[goldsilverpro]

I have recently started refining gold through inquartation and seperation process using acids and aqua regia. I can only achieve 98 % purity though.

Can someone please give me their advice on refining gold to 99.99% ?

What do you think about the Miller process and electrolytic refining?

Why do you want 99.99%? With inquartation and then aqua regia, you should easily get 99.95%, if you do things right.

 

[Jordan1]

Jordan1, how do you know it's only 98% pure?

Inquartion followed by aqua regia and precipitation with SMB or copperas followed by proper washing should normally get you closer to 99.95% if done properly.

What is the contamination?

Give us more details or we won't be able to help you.

Göran

Hi there,
I had a friend of mine checked it with a xrf gun. 98.02% purity

It was dissolved into aqua regia and precipitated with copperas.

The rest of the contaminent is silver.


Thanks,
Jordan

 

[Shark]

Others may have a better idea but in my case when silver is the major contaminant it is usually related to poor filtering. Once I reached a point where I examined my filters a bit more thoroughly and made changes accordingly I found my quality made a serious improvement.

 

[anachronism]

Spot on Shark you nailed it.

The filtered liquid needs to be crystal clear to reduce the silver contamination. You need to be able to read a newspaper clearly through the liquid.

 

[goldsilverpro]

Silver is fairly soluble in strong aqua regia but nearly insoluble in weak aqua regia.Therefore, let's say you filter the strong aqua regia and get it crystal clear. Then you rinse the filter. This dilutes the AR a little and more silver precipitates, putting you back to square one.

There are only 2 ways I know of to drop out most of this dissolved silver, so it can be filtered out. My favorite way is to simply dilute the AR solution with 3 parts of tap water per part of AR. This will precipitate about 98% of the silver. The other method is to chill the AR solution with a lot of ice. The problem I always had with the ice was to get the solution filtered before the solution warmed up and redissolved some of the silver chloride. I strongly believe that more silver can be removed with dilution than with ice and it works every time.

 

[snoman701]

GSP's post is spot on.

I have been diluting my AR with ice...by the time all of the ice melts and it makes it through the filter, it's usually at 20 deg C. My AR can then be crystal clear...you can not only read the newspaper, but if you hit it in the right spot, it magnifies the pictures and you can see the dots.

After precipitation of gold, I don't wash with HCl...just rinse with distilled water quickly. (I only get paid to two decimal points, so why bother?)

On wavelength dispersive XRF, this gold still comes out at .992-.997, with the only contaminant being Ag.

 

[Shark]

I agree with GSP also. I forget sometimes that others use different methods but I have followed GSP's way for quiet sometime now. By using the dilution method I cured many of the problems I had when using ice. Those remaining problems are where the filtering made the major improvements for me. One day I need to get some testing done to see where the purity stands, but that is just for my curiosity.

 

[anachronism]

How do you define strong AR vs weak AR Chris? Do you mean heavily pregnant vs less?

 

[autumnwillow]

How do you define strong AR vs weak AR Chris? Do you mean heavily pregnant vs less?

I think weak AR is diluted AR. The problem with using weak AR is that the digestion will be very slow but it will lower the chances of your gold chloride turning into a vapor. A strong AR will definitely put gold in your scrubber system even without heating. I observed this when I checked my condenser tube liquid with stannous.

Ag contaminant can be avoided by following GSP's advice but remember to use a #5 or #42 filter paper. Coffee filters are not up to the job. I used a #2 filter paper before and had poor results.

Edit to add: depending on where you are from. I wouldn't use tap water just to be sure.

 

[nickvc]

The only problem is the amount of waste solution you create which for some becomes a major headache, if the gold is going back into jewellery manufacture the small amount of silver makes very little to no difference so long as you know the actual purity so it isn’t worth the extra waste solution.
You could try filtering the solution twice through the same filter paper preferably using a vacuum pump, as the filter slowly clogs it catches more and more small particles or even add ice to the filter to drop the silver chloride and catch it in the paper.

 

[goldsilverpro]

How do you define strong AR vs weak AR Chris? Do you mean heavily pregnant vs less?

I should have worded that differently.

By strong AR, I meant undiluted AR. By weak, I meant after diluting 3 to 1 with water. I should have said that the greater the amount of dilution, within limits, the less the solubility of AgCl. About 50 years ago, I did a set of experiments. It's been a very long time but this is how I remember it. I don't remember if I also had gold dissolved in the AR, but, to duplicate karat gold processing, I probably did add Au, along with some copper. I started with undiluted AR that was saturated with AgCl at room temp and the dissolved Ag was analyzed by AA. I then diluted it 1 to 1, filtered it until crystal clear with glass fiber paper and then analyzed the silver by AA. I then repeated this with 2 to 1, 3 to 1, 4 to 1, and 5 to 1 dilutions. I found that the 1 to 1 dilution eliminated about 50% of the Ag, if I remember right. The 2 to 1 removed a large proportion of what was left. The 3 to 1 reduced the Ag to near zero and, beyond that, the curve flattened out and there was little or no improvement. Therefore, I included 3 to 1 dilution in my production process and have never had a reason to change it.

I can't remember a person's name but, for some strange reason, I can usually visualize and remember most everything I have done with PMs in detail, no matter how long it's been. Most of the time, I can even remember yields.

 

[anachronism]

Thanks for the clarity Chris.

Nick alluded to a point that I wanted to expand upon. If you have a situation where you've processed lots of processors in AR and you have 12 litres of solution that's loaded with in excess of 13g of gold per litre, and all the associated base metals including silver:

Would you still create an additional 36 litres of waste to get the silver out on the first pass or would you filter and drop immediately. Then redissolve in a much smaller volume say under a litre and subsequently triple the volume of this much smaller amount in order to get clear of silver?

Nick, Pat, and I have done it on the basis of using the first (larger volume) dissolve as recovery, and the second (small volume) dissolve as refine on many occasions and find it to generate much much less waste overall.

I understand that if it's initially small quantities of gold and liquid then it doesn't make much of a difference but I'd appreciate your thoughts.

Jon