First time chemical refining issues

[Airman8403]

I'm in the process of attempting to recover the precious metals from an assortment of fingers and chips. I'll describe what I've done so far and I'm hoping someone might be able to direct me further. To start this process, I initially soaked approximately 600 grams of fingers and 2 cpu's in aqua regia (my aqua regia was made using SubZero which I believe to be Sodium Nitrate and Soda Ash, and HCL) and then filtering off the debris to have a nice container of dark green but transparent liquid. Becoming impatient waiting for SMB to arrive, I tried using Oxalic Acid to recover gold and ended up with an even bigger mess but still no gold. Using gold detection liquid, I got an instant dark indication which I took to be gold. I've forgotten exactly what else I've done over the last week to try and recover my pm's but simply put, I eventually used aluminum foil to cement out all the metals I could and started over. After rinsing the resultant mud with tap water a few times, I made a batch of nitric acid (using SubZero and Liquid Fire drain cleaner) and dissolved the mud into it. I then filtered this liquid twice to get a transparent blue-green solution which I took to be silver and copper in solution with nitric acid. I then made a fresh batch of AR and soaked the filtrate from the previous filtration in it, assuming the undissolved solid to be gold. My AR dissolved MOST of the solid in my filter but still left a few chunks of some brittle substance that I haven't been able to identify. I filtered this mix and ended up with a transparent yellow acid mix which I heated and treated with Urea and after fizzing stopped, SMB. I haven't gotten the brown cloud of preciptant I was hoping for and I'm wondering if I should perhaps dilute the acid to aid in precipitation or if I've done something else wrong? I've also taken the blue-green nitric acid and suspended a ball of copper wire in it hoping to precipitate silver but only managing to produce noxious vapors and melt the copper away into solution as what looked like a black smoke. I now have a batch of AR presumably with gold in solution as well as a dark blue-green nitric acid that I can't seem to recover silver from. Any ideas or help would be GREATLY appreciated.

 

[lazersteve]

I'm in the process of attempting to recover the precious metals from an assortment of fingers and chips. I'll describe what I've done so far and I'm hoping someone might be able to direct me further. To start this process, I initially soaked approximately 600 grams of fingers and 2 cpu's in aqua regia (my aqua regia was made using SubZero which I believe to be Sodium Nitrate and Soda Ash, and HCL) and then filtering off the debris to have a nice container of dark green but transparent liquid. Becoming impatient waiting for SMB to arrive, I tried using Oxalic Acid to recover gold and ended up with an even bigger mess but still no gold. Using gold detection liquid, I got an instant dark indication which I took to be gold. I've forgotten exactly what else I've done over the last week to try and recover my pm's but simply put, I eventually used aluminum foil to cement out all the metals I could and started over. After rinsing the resultant mud with tap water a few times, I made a batch of nitric acid (using SubZero and Liquid Fire drain cleaner) and dissolved the mud into it. I then filtered this liquid twice to get a transparent blue-green solution which I took to be silver and copper in solution with nitric acid. I then made a fresh batch of AR and soaked the filtrate from the previous filtration in it, assuming the undissolved solid to be gold. My AR dissolved MOST of the solid in my filter but still left a few chunks of some brittle substance that I haven't been able to identify. I filtered this mix and ended up with a transparent yellow acid mix which I heated and treated with Urea and after fizzing stopped, SMB. I haven't gotten the brown cloud of preciptant I was hoping for and I'm wondering if I should perhaps dilute the acid to aid in precipitation or if I've done something else wrong? I've also taken the blue-green nitric acid and suspended a ball of copper wire in it hoping to precipitate silver but only managing to produce noxious vapors and melt the copper away into solution as what looked like a black smoke. I now have a batch of AR presumably with gold in solution as well as a dark blue-green nitric acid that I can't seem to recover silver from. Any ideas or help would be GREATLY appreciated.

Airman,

Welcome to the forum.

Here's a few notes to make about the overall process.

1. Remove all base metals from the scrap before dissolving gold. Use AP or 35% nitric for this step. I feel like you understand the concept, but are missing on the execution. The base metals require patience and control of the chemicals added. Too fast or too much of one chemical or another can cause problems. Nitric is best for most metals, but it needs to be free of chlorides and used in calculated doses. Do your math and know how much is required before starting a reaction. It's too expensive or hard to make, so use only what you need. If you have to do a 10 gram sample to get acquainted with the required quantities and yields. Weigh as often as possible and take notes.

2. Don't mix types of scrap. CPUs with cpus, fingers with fingers, pins with pins. All cpus and fingers are not created equal, I go as far as to separate the various grades of fingers (low medium, and high). Depending on many factors your scrap may contain values or not. Don't assume you have silver or gold unless your testing validates this (I fell your tests prove you do not have silver).

3. Ditch the idea of using urea. It's simply not required and complicates the process. There are several ways of removing excess oxidizers without using Urea. Evaporation, controlled oxidizer (eg chlorine and nitric) additions, and adding a fine gold button are three accepted methods of removing excess oxidizers.

4. When dissolving using AR don't mix up the AR before hand. Follow my methods for

Modified Poor Man's AR

to get repeatable results.

5. Test, Test, Test. Always test all solutions along the way. I feel like you understand this also.

Keep us posted on your progress.

Your gold should remain in the sludge until the AR stage. The AR should be yellow to orange colored and test positive to stannous. Confirm you are using sulfite and not sulfate, they are not the same.

Steve

 

[Airman8403]

Thanks Steve for your input. I've gone ahead and dumped my attempt at silver recovery into my waste bucket and refocused on the gold recovery. I took the boards I had left from the fingers I previously mentioned and, after stripping the flat packs with my dremel, soaked it in AP (thanks a LOT for that video series BTW, I wish I'd seen it before I started!). I now have two seperate gold recovery processes going, the one I wrote about before and this new AP batch. I noticed after letting the cards soak in AP, I do have a bit of gold foil floating around but there is also quite a bit of what looks like gold still stuck to the boards. I'm wondering if I might be able to do a solder mask removal using heated NaOH followed by another soak in the AP to recover more gold or if you might have any other ideas? I'm also wondering what I might be able to do with my other batch to recover the gold from it since the nitric-urea-SMB doesn't seem to have been the right direction to have taken. Thanks again for all of your help!

 

[Harkey1]

Hi guys,
I am about to give this a nother shot. I am about to make up another batch of nitric. I have a couple of questions.
1. I have a couple of boards that have a lot of gold foil under the solder mask instead of copper. I soaked in AP with a few other pieces of boards that had spots of gold. These soaked for a few days while I worked my regular job. I pulled the boards and filtered the solution tonight. The solution had a couple of small spots of gold. The boards were clean. Now...wheree did the gold go? Is it in the solution to be dropped by smb?
2. I am looking at my first attempt (failure). There were a lot of pins left from the nitric solution. They are rusty looking. No gold remains on them.
Should I still process them again? I have read that the AR and HCL=cl3 should have nothing left in them at the conclusion of the process.

Please clarify.
Thanks
Glenn

 

[Harold_V]

Glenn,
It's pretty simple. If you have used a chemical combination that is capable of dissolving gold, but you still have base metal that is not dissolved, any gold that was dissolved is now cemented on the remaining base metal. When that happens, what you see most likely will not resemble gold as you know it.

This is a perfect opportunity for you to come to understand why it's always best to eliminate base metals before attempting to recover the values. Processing them in tandem is a PITA, and generally results in inferior quality.

Your gold is not lost. It's still waiting for you. Eliminate the base metals, then process the remaining solids for the values.

Read Hoke!

Harold

 

[Harkey1]

Ok. I have re-read. She said that we have to disolve all of the metals (base) before proceeding. So at this point I have a bunch of pins that hve been partially disolved with the gold cemented back on them. They are dry and waiting. Should I go back to the Nitric bath or go to the AP proceedure? These are from the first nitric bath that I did not allow to complete. I went with a full strength nitric (made it) and about 1.5 lbs of pins.

 

[lazersteve]

Ok. I have re-read. She said that we have to disolve all of the metals (base) before proceeding. So at this point I have a bunch of pins that hve been partially disolved with the gold cemented back on them. They are dry and waiting. Should I go back to the Nitric bath or go to the AP proceedure? These are from the first nitric bath that I did not allow to complete. I went with a full strength nitric (made it) and about 1.5 lbs of pins.

Use the nitric acid. I would not use the term 'bath' as this implies that the pins go in and then out shortly thereafter. The purpose of using the nitric acid is to dissolve all of the base metals. You'll know the reaction is complete when no more brown fumes are given off, even when the reaction is heated and a little more nitric is added. The gold will float freely around the beaker as foils and a fine brown powder that settles to the bottom. Poke around the foils with a glass rod, you should feel no solid chunks. When the beaker of rinsed foils is tilted side to side nothing should rattle like metal. The gold foils will shift, but not clink. When this step is completed, you have finished with the nitric acid.

Steve

 

[Harkey1]

Let me get this straight. I need to put them back in the nitric to disolve all until there is no more reaction. Will the gold that has cemented to the other parts go back to the bottom as a brown powder to be filtered off?

 

[Barren Realms 007]

Let me get this straight. I need to put them back in the nitric to disolve all until there is no more reaction. Will the gold that has cemented to the other parts go back to the bottom as a brown powder to be filtered off?

That is correct on adding them back to the nitric. And yes the gold that has adhered to your current pins should settle in the bottom once the disolving process is complete.

Make sure the nitric is diluted it will work better and with some heat too.

 

[Harkey1]

Thank you Barren. I will get it done. I appreciate your help on the matter.