Help building a Aqua Regia System

[sohan]

I want to build a aquaregia system for refining gold jewellery of 18k to 23k ranging from 500gms to 2kg. I generally cast a bar and than make a strip roll and put in aqua regia solution and than manual stir, than filter and than precipitate. There is loss of gold dissolved solution in manual process.
I was thinking if any one has build a system could help me build one. I have borosilicate beakers.
Components i need help regarding :
● stirrer and heater (now i am using a induction with iron plate)
● pump to transfer AR solution for filtering.
● pump to tranfer gold precipitated solution with gold powder for filtering.

I have seen systems available in market starting from 5,00,000 Indian Rupees. I am thinking of building a system myself as i like DIY's and save some money. Any help, suggestions or advice would be helpful.

 

[4metals]

What is the percentage of Silver in your alloy?
Is nitric acid available and affordable in your area?


Your answer will determine the best path for you to follow.

 

[sohan]

What is the percentage of Silver in your alloy?
Is nitric acid available and affordable in your area?


Your answer will determine the best path for you to follow.

5-10% of silver and nitric is available 3000 INR for 40 litres

 

[4metals]

Your losses were probably because of Silver Chloride in aqua regia. Especially if you approach 10% Silver.

I think your best bet will be inquartation and double parting with nitric acid. That can get your purity in excess of .995 without dissolving the gold in aqua regia. And you will recover all of the Silver you need to add for the process plus all of the Silver in the alloy.

The benefit of nitric parting is it can be done in stainless steel so no glass breakage worries. We have had members here measuring gold refined this way by XRF and getting results of .999+ (specifically a refiner in Vietnam).

The volumes you are working with can be easily transferred by vacuum and the final rinses with Distilled Water can be easily lifted and poured.

 

[4metals]

This approach is easy for a DIY refiner. Your most important equipment will be your melt furnace which you have, a good fume hood and a strong vacuum system. A scrubber will be beneficial if you are in an inner city location.

 

[4metals]

This thread will be useful to you. His feed had a high Silver content and he originally wanted to use aqua regia. He tried both aqua regia and nitric acid and decided in the end to use nitric. It was a good thread because he got back to us with his results and was able to see it both ways.

 

[sohan]

I have

Your losses were probably because of Silver Chloride in aqua regia. Especially if you approach 10% Silver.

I think your best bet will be inquartation and double parting with nitric acid. That can get your purity in excess of .995 without dissolving the gold in aqua regia. And you will recover all of the Silver you need to add for the process plus all of the Silver in the alloy.

The benefit of nitric parting is it can be done in stainless steel so no glass breakage worries. We have had members here measuring gold refined this way by XRF and getting results of .999+ (specifically a refiner in Vietnam).

The volumes you are working with can be easily transferred by vacuum and the final rinses with Distilled Water can be easily lifted and poured.

Used the inquartating with silver method and also copper i stead of silver.but again i have to invest in silver and extract silver again. Copper needs more nitric. Hence want to use aqua regia method.

 

[sohan]

This approach is easy for a DIY refiner. Your most important equipment will be your melt furnace which you have, a good fume hood and a strong vacuum system. A scrubber will be beneficial if you are in an inner city location.

I have furnace. I want help regarding pump and stirrer and heater.

 

[4metals]

Hence want to use aqua regia method.

You are suffering from a case of not knowing what you do not know. You will chase lost gold and silver all over your shop and you will have to convert any Silver Chloride you collect to recover the Silver as metal. And if there are any platinum group metals in your melts you will have to go to great lengths to collect them as well.

I have never had as good a result inquarting with copper which is why I suggested Silver in the first place. Your investment in Silver metal will be one time and you will recover all of the Silver in the alloy along with what you invested in Silver.

If you have come here having decided what you have to do then why don't you simply google scientific hot plate stirrer and plenty of options will pop up. No one pumps aqua regia so forget the pump idea, the pump won't last.

There are many members here who use aqua regia and many who inquart. I have suggested something that will work for you but instead of asking for specifics and details you have already decided. I will sit back now and let others help you and learn from them as well.

 

[sohan]

You are suffering from a case of not knowing what you do not know. You will chase lost gold and silver all over your shop and you will have to convert any Silver Chloride you collect to recover the Silver as metal. And if there are any platinum group metals in your melts you will have to go to great lengths to collect them as well.

I have never had as good a result inquarting with copper which is why I suggested Silver in the first place. Your investment in Silver metal will be one time and you will recover all of the Silver in the alloy along with what you invested in Silver.

If you have come here having decided what you have to do then why don't you simply google scientific hot plate stirrer and plenty of options will pop up. No one pumps aqua regia so forget the pump idea, the pump won't last.

There are many members here who use aqua regia and many who inquart. I have suggested something that will work for you but instead of asking for specifics and details you have already decided. I will sit back now and let others help you and learn from them as well.

Thanks for your reply.
i have asked help regarding building a system for aqua regia method. There are many pumps available in market and on google, but i needed a suggestion or advice if anyone has used or has information about the pump. There are commercial systems available here that use pump for transfer of aqua regia and also precipitated solution.
attached a image of system available in market
https://d91ztqmtx7u1k.cloudfront.ne...4848-26aa58fd-9f8a-43cd-ba07-696d637bdecc.jpg

 

[Yggdrasil]

Thanks for your reply.
i have asked help regarding building a system for aqua regia method. There are many pumps available in market and on google, but i needed a suggestion or advice if anyone has used or has information about the pump. There are commercial systems available here that use pump for transfer of aqua regia and also precipitated solution.
attached a image of system available in market
https://d91ztqmtx7u1k.cloudfront.ne...4848-26aa58fd-9f8a-43cd-ba07-696d637bdecc.jpg

I rarely click unknown links on the net so can you take a screenshot and post it here?
If 4Metals says there are no good pumps for Aqua Regia I believe him and so should you.

 

[4metals]

The system you showed will not allow me to enlarge it to point out specifics so I will compare it to systems available from European manufacturers.

The concentrated acids are fed into reservoir tanks by vacuum suction and dispensed to the reactor by gravity. No pumps hold up well long term so vacuum is used.

The reacted liquids containing gold and insolubles drain by gravity as well into a filter where the acid is sucked through the filter and transferred by a pump. The pumps used are maintenance intensive as they are pumping aqua regia. If you can neutralize the oxidizer first the pumps stand up a bit better but this is difficult. If you were processing large lots this can be an effective way to go. You are processing 1/2 to 2 kilo lots which are by industry standards small lots. The pumps are double diaphragm pumps and all of the internal parts are selected for their ability to stand up to nitric acid. Even the manufacturers of these pumps do not recommend extended nitric exposure even though I am sure they would love to sell you spare parts.

If you were to buy one of these systems you will still have to deal with Silver Chloride encrustation which will inhibit all of your gold from dissolving. And if you use aqua regia you will have any PGM findings in the jewelry you process remaining in the aqua regia after dropping the gold. You will have to chase those down from the spent acid. your collected insolubles which include Silver Chloride and gold will need to be treated and you will for the short term be complaining about lost gold.

Again for what you would spend for small lots you would be better off with Silver inquartation and having all of your gold in one place at the end of the day and all of the Silver as nitrate and the PGM's mixed in. Cementing on copper is quick and easy and the Silver metal can be re-used forever. Plus all of the Silver in the alloys to start will accumulate. Eventually a small Silver cell will allow you to collect PGM's from the Silver you refine to 999 purity.

I'm still waiting for other members to agree or disagree here. You know where I stand on this.

 

[anarxi]

....

 

[anarxi]

I was told that in the Soviet Union tantalum and alloys based on it were widely used for such work.
but how reliable this is, I don't know.

 

[4metals]

Titanium is used for aqua regia vessels and mixers, it holds up well.

 

[anarxi]

Titanium is used for aqua regia vessels and mixers, it holds up well.

tantalum, not titanium.

 

[4metals]

I realize what you said and I personally have not seen tantalum used for refining equipment. Titanium is more readily available. More to the point how does suggesting an exotic choice of metal for acid resistance help the OP who is quibbling about inquarting because he has to buy Silver?