Non-Chemical Removing HCl and SnCl2 after initial wash

[kernels]

Hi guys,

Hoping for a bit of advice from experienced members.

If I have some fine material that has been incinerated and sieved, and I believe there to be Tin present, my thoughts are to first treat this material with warm HCl to dissolve the tin before treating with Nitric to remove other base metals.

What would then be the best method to rid the material of the residual HCl and Stannous chloride before Nitric treatment ?

Could I repeatedly wash the material with water, then incinerate in a pan ?

Thanks!

 

[jason_recliner]

In general, yes.
And if you want to know for sure there was tin present, test your HCl wash-waste with a tiny drop of gold solution.

 

[patnor1011]

That depend on what this fine sieved incinerated material actually is. So what is it?

 

[nickvc]

Pats hit the nail well and truly on the head.
The more information that is posted about any processes , part process , chemicals or materials that can be posted should be included otherwise we are all second guessing, this isn't having a go at you kernels but to all who have questions for part processed materials or processes, we all assume that the material is processed in the proscribed way but unfortunately that isn't always the case so an A to Z explanation of how the poster has arrived at this point really helps us to help you or them.

 

[kernels]

Hi guys, thanks for the advice so far. Sorry about not including more detail in my original post, the source material will be incinerated, then blended, then sieved ICs with legs - about 10kg (22lb)

The ICs were removed from the boards by heating the boards to the melting point of the solder, then tapping the boards in a bucket to remove the ICs. So there will almost certainly be some remaining solder on the legs of the ICs.

When I then incinerate + blender the ICs, some of that solder will make it's way through the sieve.

I have considered a warm HCl wash of the ICs as the first step in the process, but am hesitant about creating a large amount of waste acid to deal with.

By incinerating and blending first, then removing the magnetic legs, then panning the material, I hope to reduce my acid usage and the associated chemical waste.

 

[kernels]

Once again, very much appreciate the time and insight from the forum contributors. Please let me know if any of the above is not clear enough.

 

[nickvc]

Getting rid of tin at the first opportunity is never a bad thing but in this case I think using the HCl washes after sieving will be the best course of action, the tin by then should be in small particles and thus easy to remove.
With the HCl you use to dissolve the tin just pour into a marked container for use on the next batch and use it until it stops working, check its effectiveness by after pouring it into the container add a little fresh HCl to the powders and see if you get any reaction.
After the HCl soak just rinse your material with water and then follow Patnors process to concentrate your values, in fact read his whole process and work based on that.

 

[patnor1011]

I simply crush, sieve, wash, dry and repeat till you get to concentrate where values are. I do not introduce chemicals until I am in like 1/10th of starting volume.
Also sieving starting material and concentrate repeatedly - like 4-5 times will help to remove over 90% of metallic legs, sometimes even 95% that depend on how fine your sieve is.
I just finished concentrating values from 2 buckets of IC, they were reduced to about 2 handfulls of material which I now leach in HCl+bit of old AP for about a week to get rid of nonmagnetic small pins which escaped sieving. I am not in rush so I do not use heat, 10 days with agitating once a day will sort them out.
After that I will wash, dry, crush, wash again to reduce even more of last carbon in concentrate. I aim for like 2-3 spoons volume and then AR and happy time.

 

[4metals]

I aim for like 2-3 spoons volume and then AR and happy time.

Just to quantify things a bit, those 2-3 spoons of happy time will generate approximately how many grams of gold?

 

[patnor1011]

I aim for like 2-3 spoons volume and then AR and happy time.

Just to quantify things a bit, those 2-3 spoons of happy time will generate approximately how many grams of gold?

I am running 2 batches right now.
1.
BGA N/S Bridge approx 4,5+kg and BGA IC from RAM approx 1,5+kg. Hard to say exactly but incinerated crushed and sieved powder filled small mayonnaise bucket which has capacity 6,5 liter. This was washed, then dried, crushed and all this repeated about 5-6 times. Every round will reduce starting material to about half - in first few cycles, then it slows to about 30-40% reduction from starting volume.
So I managed to reduce 6,5 liter bucket to about 6 full spoons of material which should contain about 30+grams of gold. It would be less but I did not removed solder balls from 1,5kg BGA RAM IC so I am washing it in HCl right now as crushing further become impossible due to solder balls. There is also some amount of copper wires present which remained stuck on black part of BGA when separated from green part. After I wash this solder out I expect to reduce this 6 spoons of concentrate to no more than 2.

2.
Mixed IC with legs. All kind of types except eprom type. Amount is hard to estimate but it was over 10kg but I am shooting blank here it is just guess as it could be more. I was incinerating them in small batches over winter and then I crushed them, sieved several times to remove most of pins and stored this powder over time. I got 2 small 6,5 liter buckets full of it. Here I did the same as with BGA but I also sieved dried crushed material to catch some pins every time I repeated cycle. I do not have super fine sieve I use sieve with smallest holes I managed to find around so it take several runs to get most of pins out. Anyway I got about 90-95% pins out. At the end from what remained I removed some more pins with magnet. I reduced this 2 bucket to about only 3 spoons of material which is mostly small glass balls from broken Si wafers and small amount of pins. All that sit now in HCl to remove base metals. I will not be crushing this further as there is only Si wafers and pretty much no carbon left so it should be good to go to AR. I expect at least 10g of gold there.

I understand that it may look too labor or time intensive but it is a hobby for me and I simply enjoy that. When I wash I pour water in bucket with powder, stir and let it settle for a 45 sec - minute. Then I decant 75% of water and pour in fresh. I may be crazy but I pour this wash water in special tank where it settle and I take out settled powder only to run it again in one of my sluices. I just go that extra mile to ensure I am not losing any of the good stuff. I also reuse the same water after washed material settle on bottom. I do this like that few years already and I know that there is no gold escaping but I somehow cant help myself and I check everything not twice but several times.

Sometimes I do use my sluice with closed circuit of water to wash out first finest ash/powder but only when weather is nice so I can run it few hours. Weather is unpredictable in Ireland, I mean it is raining always and it is hard to predict what day there will be no rain and for how long. You get sun out and it change in 10 minutes to heavy rain and that can happen several times during the day. Here is short video of one sluice at work:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=11827&start=660#p254839

Perhaps one few hour long run in good ball mill will be enough but I do not have one so I do have to resort to repeating crush/wash/dry cycles.

 

[kernels]

Thank you guys, this is pretty much the answers I was hoping for. Would have never thought to test the washed out HCl / SC with a drop of gold solution. It sounds like if I am able to wash enough of the Stannous out with repeated water washes, I may not need to incinerate before the nitric leach.

Also, because I am removing the magnetic pins before adding chemicals, I should be mechanically removing 90%-ish of the tin that is there, it's only the little bit that gets through the fine sieve that will require acid. By trying to remove tin from the IC's at the beginning of the process, you would have to dissolve all the tin on all the legs.

Will study all the replies again in detail, but it sounds like my general desire to concentrate the material before moving to chemicals is standard practice for the more experienced members.

If I do incinerate after washing out the HCl and SnCl2, will a LPG blow torch in a stainless steel pan be hot enough ? What happens to any remaining SnCl2 (salt) if you get it that hot ?

 

[patnor1011]

You do not need to concern yourself with small amount of tin. Tin is problem when dissolving whole brass pins or something like that. Small amount of solder should not be any concern. Also the more you concentrate values by grinding and washing with water the less time and chemicals you spend leaching undesirable base metals. I mean it is better to leach 100grams of material than a the same thing in a kilogram of fine ash.

 

[jason_recliner]

Would have never thought to test the washed out HCl / SC with a drop of gold solution. It sounds like if I am able to wash enough of the Stannous out with repeated water washes, I may not need to incinerate before the nitric leach.

No, this is unrelated. The suggestion was only to let you know whether or not you actually had tin. But how, either way, you will have HCl.
So if you want to use nitric to remove other base metals, you must be completely rid of HCl first.

Always incinerate when switching between HCl and nitric, unless you are happy to lose a bit of your gold.
The only exception is (obviously) when you are going straight from HCl to AR, which is frequently suitable. Pat mentioned this a couple of times in this thread.

If I do incinerate after washing out the HCl and SnCl2, will a LPG blow torch in a stainless steel pan be hot enough ? What happens to any remaining SnCl2 (salt) if you get it that hot ?

You want it hot enough to glow a dull red for a couple of minutes, but don't let it melt.
SnCl2 will be a liquid in the HCl that you rinsed out. If you did a good job of dissolving tin, the few remaining molecules are unlikely to make much of a metastannic goo problem.