Aqua Regia Process questions

[cblakely]

I have been lurking for a few months now and have read Hoke’s book. I know, I should probably read it again.

My question here is about Aqua Regia. So you don’t think that I am jumping steps; I am doing the hydrochloric acid and hydrogen peroxide wash and then the nitric acid wash. I then have a light almost grey colored sludge from processing CPU pins. I take that and put it into the Aqua Regia. The aqua regia is a nice amber yellow color. I expect it to be more an orange brown color as it consumes the gold. The volume of the sludge has only decreased by a small amount.

I started this phase over a week ago. What I have read it should have dissolved over night. Also another thing I read is that it should take 120 ml of ar per oz of gold. I had about 100 ml of sludge which I weighed at about 8 oz (not troy) and I know that it is not pure, but that should give me a guideline of about 1000 ml of ar. I started with about 200 ml of ar the first night and slowly added more hcl and nitric over the course of a week until I stopped at 1000+ ml. I am thinking about adding more nitric to kick start it, but do not want to overdo it and have to fight that. I have even thought about taking my sludge and putting a flame to it, believing that I would get mostly gold.

It is still winter here and I am working outside in a two horse trainer, so it has a roof, but is open for ventilation about shoulder height. I have a hot plate that is set to warm to keep things going.

Any ideas? Am I just being too impatient?

 

[FrugalRefiner]

My question here is about Aqua Regia. So you don’t think that I am jumping steps; I am doing the hydrochloric acid and hydrogen peroxide wash and then the nitric acid wash.

Let's start here. I have never heard of anyone using hydrochloric acid and hydrogen peroxide as a wash. Keep in mind that hydrochloric acid and hydrogen peroxide will dissolve gold. Did you test your wash solutions to see if they contained gold? Did you save them?

You didn't mention how you started your process on your CPU pins. Maybe you started with the HCl and peroxide to dissolve the base metals? This wouldn't be considered a wash. In any event, once you had your material in HCl, it needs to be incinerated before you introduce nitric acid, or again, you will dissolve some values. Did you test the nitric washes for gold?

I then have a light almost grey colored sludge from processing CPU pins.

As mentioned above, you didn't really tell us how you processed these pins, so it's difficult to guess what might be in your sludge, but it's almost certainly base metals.

I take that and put it into the Aqua Regia. The aqua regia is a nice amber yellow color. I expect it to be more an orange brown color as it consumes the gold. The volume of the sludge has only decreased by a small amount.

Amber yellow is good, depending on how concentrated the gold is in the solution.

I started this phase over a week ago. What I have read it should have dissolved over night. Also another thing I read is that it should take 120 ml of ar per oz of gold. I had about 100 ml of sludge which I weighed at about 8 oz (not troy) and I know that it is not pure, but that should give me a guideline of about 1000 ml of ar. I started with about 200 ml of ar the first night and slowly added more hcl and nitric over the course of a week until I stopped at 1000+ ml. I am thinking about adding more nitric to kick start it, but do not want to overdo it and have to fight that. I have even thought about taking my sludge and putting a flame to it, believing that I would get mostly gold.

Several thought come to mind. First, as Hoke tells us, any time you're doing a process for the first time, or processing a new material, it's good to do a small test batch instead of going all in. Second, you may need more heat to drive the reaction to completion. Once you're sure the AR has dissolved as much material as it can, you would be better served to decant the saturated solution off the remaining sludge and adding fresh acid to what remains rather than continuing to add acid to the existing solution. "Putting a flame to it", i.e., incinerating the sludge, would have been a good idea earlier in the process.

It is still winter here and I am working outside in a two horse trainer, so it has a roof, but is open for ventilation about shoulder height. I have a hot plate that is set to warm to keep things going.

As mentioned above, you may not have enough heat to drive the reaction to completion.

Keep studying. It's all very confusing at first, but the more you read the more the puzzle pieces fit together. Start with small tests. If things go well, you can scale up. If you start large and things don't go well, you can end up losing a lot of values as well as ending up with large quantities of toxic waste.

Dave

 

[cblakely]

I have kept all of my solutions. I have a test kit, but did not test the hcl solution as I did not think about it having consumed values. With the lead from the base of the pins and the hcl, it would seem like a stanus like solution already. I plan to reuse it with a little refresh for pinless cpus. After I have used it a while, I may attempt to do a gold drop from it.

"Wash" may be an incorrect term. I usually soak the pins for a week and then siphon off as much of the solution as I can. I will then dilute what is left with the pins with water. I will let that settle for a few hours and siphon the solution off. I repeat until I have a clear solution. I then use magnets to collect the ferrous parts and rinse the magnets to get off the loose non-ferrous parts. I set the the pins aside, but if it looks like they still have something on them, I will throw them back in the hcl solution for another week or so.

By now I have done a lot of rinses, I have used grease cutting dish soap, to help me remove some of the cpu grease. I do not want any residual hcl when I put it into the nitric. I have that watered down to maybe 10:1. I have it on heat so it will condense. It soaks for 4-7 days. The solution turns a very nice blue color, I believe that is the silver. I have not tried to drop it out yet was I want to use it for a couple more batches. I will probably be full of questions when I do.

I may be just too inpatient with the aqua regia. I have two batches going right now. The last one has a slight green cast. It was the one that only sat in the the nitric for 4 days. I must have left some silver or copper behind.

I know that I jumped in very deep very quickly. I was out of work for a while from a pretty well paying position as a software developer. This was to be income replacement and I pulled from some resources to get started. I am back working now, so the game changed a little, but the desire has not. I would like to build a lab this summer, time and money permitting, so I have a more controlled environment.

Clay

 

[bmgold2]

Sounds like you plan to get into this refining hobby/business in a big way. Be sure to check out all the laws and legal requirements for what you have planned. Processing hundreds of pounds of chips or whatever sounds to me like that is going to take a lot of chemicals which means a lot of waste to deal with also. If you have the money to do it right then I say do it. You wouldn't be the only one on this forum who is or was doing this refining full time. There must be money to be made at it once you are set up AND you know what you are doing. I'm pretty sure there is a big difference between somebody doing a few pounds of chips or pins to get a little gold for their own collection or to sell and someone processing large amounts on a steady basis. For me, I'm still working to get my first little button of gold and I don't have any real plans to sell anything I refine. That could change depending on how I make out on my first tries at this but I consider it just a hobby.

One more thing. If this is going to be more than a small scale hobby, don't forget that taxes will have to be paid on any income BUT you should be able to claim a lot of your expenses as business costs. You may need an accountant but that would be a business expense too. You got to spend money to make money. Just don't go broke before you start actually making money. Save all your receipts for anything that may be considered a business expense.

Good luck.

 

[FrugalRefiner]

Clay,

I'm not trying to be mean, but you have a lot of information jumbled up in your mind right now, and it will lead to more mistakes.

Lead does not make a stannous like solution.
You cannot rinse away all traces of HCl. If you don't incinerate, you'll dissolve some gold in the nitric.
Silver is colorless in nitric, not blue.

Like I said, I'm not trying to be mean. I understand you were under pressure when you jumped in. I'm glad you are working again, because trying to make money while you're learning this probably wouldn't have happened. As you've learned, it's not quite as easy as it seems. My advice would be to set everything aside in a safe place and get back to learning. Read Hoke again. I've read it a half dozen times now, and more and more sinks in every time. Study while the weather is lousy and while you put together your lab. Then you'll have a much better idea of how to recover your gold. It will wait for you.

Dave