Stainless steel in my Cu(II)Cl etch and now a huge mess!

[raa]

So I'm new to the gold recovery game and I seem to have made a very silly and basic error.

It all started well enough. I've been reading the forum for several weeks and watching videos on Youtube. I decided it was time to start with the simplest process and run some close cut RAM fingers. I already had some HCL based patio cleaner so I used the 'bucket with drain holes within a larger container' method to etch the copper and release the foils.

No peroxide was used, I just ran a 3mm hose from a nebuliser into the bottom of the container and ran it intermittently for around 3 hours per day. After about a week the solution started going green. After 3 1/2 weeks the fingers were completely stripped of metal and the solution was a deep dark green.

I captured the foils in a coffee filter but the foils were trapped in an oily matrix probably caused by the unfortunate presence of additives in the patio cleaner. , I cleaned up the foils by roasting them (to drive off the oily detergents in the patio cleaner), then washed them in NaOH solution, rinsed them with H2O and dissolved in HCl/bleach and finally dropped with sodium metabisulphate.

For a first attempt at gold recovery it all seemed to go rather well. The gold took two days to fully settle but I ended up with 1.3g of what looks like fairly clean (based on looking at pictures of other people's gold drops) Au powder from 275g of close cut fingers. I won't melt anything until I have at least 2g of powder.



So after this good result I decided to run a second batch. I remembered reading somewhere under a youtube video that if you place stainless steel in the solution, you can remove it with copper cemented onto it thus extending the life of the etchant.

I had plenty of stainless hard drive lids so i dropped one in - big mistake! - After a few days I went to check if any copper had cemented onto the stainless . The hard drive lid had disintegrated into pieces and the nice green solution was now an ugly rusty orange colour.

I think I probably compounded the error by not removing the RAM fingers from the solution when I still had the chance before any foils had been released.

Anyway I let the solution do its work. It took a similar amount of time for the fingers to be completely stripped of metal.

I removed the stripped plastic pieces today and here is what it looks like:



It doesn't look so bad here as it has been undisturbed for a few hours......

......But give it a stir and you get this:



There seems to be a layer of some of deposit on the bottom of the container which has a 'ferrous' look.
You can also see the rusty staining of the bucket and container; before I foolishly added the stainless steel they both stayed clean.

My dilemma is where to go from here. My gold foils are in that container and something tells me that solution is definitely not going to pass through a coffee filter.

Obviously I would like to get my gold foils back out of the mess if possible. Should I let the solution settle and try to decant off the lighter fractions leaving less material to be 'worked on'?

I probably now have Chromium and possibly Nickel in the solution along with lots of Iron. What implications would this have with regard to dealing with the waste?

Any advice much appreciated
Mark

 

[anachronism]

Hi Mark

Firstly welcome.

Secondly Stainless Steel and HCl don't mix. As in they really don't mix. 8)

Do you have any Nitric?

Jon

 

[MrCrusher]

Mark,

" So I'm new to the gold recovery game "

This is NOT a game.

While I am not the best person to advise you how to fix your mess. One thing you said struck me real hard.

" I probably now have Chromium and possibly Nickel in the solution along with lots of Iron. What implications would this have with regard to dealing with the waste? "

You wanted to know how to deal with the waste. You need to read Hoke and do much more studying.
I am a relative newbie myself. However before I did anything I was concerned how to handle the by products. Since they are VERY hazardous. There are ways to clean your waste and only be left with solids. That can be disposed of at your local hazardous waste location. You should NEVER pour any liquids down the drain or into a septic system. These by products kill wild life and pollute drinking water at the very least. All the information you need to deal with the by products can be found here at the forum.

Please stop what your doing and study more. Watching YouTube videos it not studying. 90% of them are mis-information. There is much to learn here and in Hoke's book. It is good basics.

Thanx
MrCrusher

 

[raa]

Hi Jon

No they clearly don't mix. In future I will be highly sceptical of youtube pearls of wisdom!

I do not have access to any nitric but I have just ordered some 33% HCl.

 

[anachronism]

What strength HCl were you using before?

 

[raa]

@Mr Crusher

Point taken

You are most correct that I need to do much more reading on the subject. To be fair to myself however I have read Hoke (although once is obviously not enough), and am under no illusion regarding how dangerous concentrated acids and their fumes are and how toxic metals in solution can be.

Don't worry, I wouldn't dream of pouring metal laden solutions away. I have read about the basic process of cementing out metals and ultimately ending up with a salt water solution and some solid wastes but lack information at the moment on how to deal with Cr and Ni and whether they need special consideration.

Actually i wasn't expecting to have to deal with waste processing so soon but this solution has probably been ruined. At least I will know what not to do in future...

 

[raa]

What strength HCl were you using before?

Whatever the patio cleaner happened to be. The patio cleaner didn't visibly 'fume' so I think this means it would be below 20%.

It etched the copper well enough the first batch I ran but I won't be using patio cleaner again because the unwanted detergents and surfactants seem to create extra steps in the process.

 

[anachronism]

Patio cleaner is often around 3% so it's possible that youve exhausted your HCl. If you dont have Nitric, try taking a small part of the powder and heating it in some fresh strong HCl.

 

[kernels]

Firstly, your method looks good, your gold yield is exactly what I would expect and your question is clear and concise - very good

First step for me would be to take a small amount of that muck and add some fresh HCl to it, I suspect that will clear it up. You can experiment on a small amount to work out the exact amount of HCl you will have to add to the big bucket to get it clear.

Don't try to filter that mess until you have cleared it up (learned this the hard way)

There is no 'refreshing' of C2C etchant by placing iron in it (I think it was Moose Scrapper that has caused many people to screw this up) you are simply replacing copper in the solution with iron. I tend to just keep using the same C2C etchant (AP solution) until it no longer etches copper, then add HCl to get it going again. At the end of the day when the solution has grown too much in volume, I go through the waste processing to remove the copper and end up with Iron Hydroxide before it's disposal. 4Metals has a brilliant post in one of the sections about waste treatment on home-scale.

 

[kernels]

And, if you keep asking clear questions with pictures you will get a lot of help on this forum. Only other thing to add is to keep yourself safe, we hate hearing about guys who poisoned or injured themselves or their (our) environment.

 

[MrCrusher]

raa,

Thank you for informing me of your cleanup desires. I have witnessed a few " toxic dump sights"
and am always concerned about these types of pollutants. It is a huge concern of mine. I am sorry however if I seamed a little harsh. It was not meant that way. While I am not aware of the toxic waste places in England ( every country has some ) I have seen 3 here in the USA and it is not a pretty sight.

When you know it could have all been avoided.

Thanx
MrCrusher

 

[raa]

Thanks for the various advice so far. I will try adding full strength HCl to a small sample of the solution as suggested and report back soon...

 

[g_axelsson]

Welcome to the forum!

That was a good and clearly formulated question, and you already got a lot of answers.

I agree with the common suggestion, HCl should clear up most of the iron contamination and put it in solution. There probably is a lot of fine copper mixed in with the rust at the bottom of the bucket, that is the cemented copper.
In your place I would add HCl (first to a small sample and then ) to the solution to clear the rust up. Now check the circuit boards to see if they are fully etched, if so just remove them, and if not replace the solution and restart a copper chloride etch.
You probably need to restart the copper chloride etch to get the fine cemented copper powder out.

All my waste solutions goes through a copper cementation step first and then treated with lye to drop metals as hydroxides. There is a good post about it in the library section.

To cement copper out of waste solution I use ordinary iron parts as disk bays or pieces of iron that is easily removed from computer cases. Any stainless parts is sold as scrap, it pays better than plain iron and is inferior for cementing out copper from waste solutions.

It's a sad world where a youtuber like moose scrapper has as many followers as this forum has members. But that's the world we live in now, where you get your instant information from a 5 minute video and then you are an expert on a subject.

There are a number of members that have made good youtube videos. Here is a list of some of them.
http://goldrefiningwiki.com/mediawiki/index.php/YouTube

Göran

 

[raa]

Well thanks again for the advice gentlemen, your diagnoses were spot on!

Having first tested a small sample around 300ml of HCl was enough to get the solution back to how it was (visually anyway) before I added the stainless lid.


I captured the solids in a coffee filter then rinsed through with water.

Then I used a trigger spray with water to wash the contents of the filter into a stainless bowl. I then evaporated off the water and roasted the solids to deal with the oily compounds in the patio cleaner.


At the start of the evapotation the foils are still shiny as they move around in the container


However after being roasted the foils look quite dull (sorry for the poor photo). The bottom of the stainless bowl was glowing a dull red for a time and there was plenty of smoke as the oils and detergents were gasified off.


At this point for the first batch I did, I rinsed this material in a NaOH solution, it made the gold appear a bit cleaner and the wash solution took on a faint blue colour so it must have removed some contanimant.

What do people think? Would it be worthwhile at this stage to rinse in HCl or NaOH or should I skip the extra step and go straight for the HCl/bleach?

Mark

 

[kernels]

I've never personally bothered with all the cleaning steps for the foils, once I have them in a filter and have washed most of the Copper Chloride out, it goes straight to AR digest. You can once again do a test on a small sample to see the results, but I would be inclined to dissolve them, filter the pregnant solution (or even better if you don't have good a vacuum filtering setup is to just leave the solution for a couple of days for any minute particles to settle out) then precipitate with your method of choice.

Next time you drive by the pool shop, stop in and get some cleanish HCl too

 

[Topher_osAUrus]

That stainless bowl is going to get destroyed in notime flat.
Even a tiny amount of HCl is enough to wreak havoc on stainless. So the material must be rinsed very very well before getting put in there.
Stainless will,however, hold up to nitric... But not hydrochloric.

A corningware pyroceram dish is a much better option, as it will hold up tp any type of acid we work with. They can be incinerated in, and even leached in. It is also a good medium to put between your burner and beaker to prevent losses, should your beaker break. It's a good, cheap, investment found at almost any thrift store.

 

[g_axelsson]

I used a stainless steep pot with too thin material in it... The final incineration was with material that contained a bit too much acidic salts in it. Here is the result.


Göran

 

[anachronism]

Mark

As the lads have said above, get the right gear. Glass lab beakers are as cheap as chips on ebay in the UK. Also get yourself a couple of these if you're using gas to heat.

http://www.ebay.co.uk/itm/High-Quality-Metal-Mesh-Wire-Lab-Gauze-for-Bunsen-Burner-/330940592950

Finally always use a catch pan in case something breaks. something plastic and big enough to hold your glass/burner/hotplate etc.

http://www.ebay.co.uk/itm/Garland-Garden-Trays-Various-Sizes-Types-Colours-Plastic-Hydroponic-Greenhouse/131800494006?_trksid=p2045573.c100505.m3226&_trkparms=aid%3D555014%26algo%3DPL.DEFAULT%26ao%3D1%26asc%3D45398%26meid%3D6068fcdf721c47a4b58a41bedcd1492e%26pid%3D100505%26rk%3D1%26rkt%3D1%26

Anything like the above is cheaper than losing your gold.

Jon

 

[raa]

...a corningware pyroceram dish...

Thanks for the tips. I wasn't sure what this was is so I looked it up on Wiki.

https://en.wikipedia.org/wiki/CorningWare

Seems like I need to look for the word 'pyroceram' as there are lookalike Corningware products which don't have the same thermal properties.

I'll be making a trip to some charity (thrift) shops today...the only type of shopping I enjoy

 

[raa]

So I found some Corningware (branded Pyrosil - apparently the same stuff but made under licence in Europe) for almost no money. I seems rather nice though, It doesn't seem right to use it for this, might have to keep it for kitchen use and look for a 'not so nice' one


Anyway I thought I would give an update how my process is going...

I dissolved the gold, without any extra cleaning steps this time, using HCl bleach.

I had made some Stannous Chloride solution using lead free solder and got a clear positive for gold in solution. I also got a clear negative from the solution my first batch was dropped. This was my first time using Stannous and i was great to see it working so clearly.

The solution was extremely dirty and took a long time to filter by gravity through coffee filters. Towards the end I needed to transfer the solution to a second filter as the first became so loaded the filtration stopped.

Here are the solids in the filter. At the moment I don't know what this material is; silica from the PCBs?


After filtration the solution still looked very cloudy but not with solids. The solution was full of tiny trapped gas bubbles. This didn't happen on the first batch I did so I think I must have added too much bleach.

I decided to try to dive off the gas bubbles by gently heating the solution. The pyrex vessel is being heated in a bowl of sand. The temperature was limited to 70 degrees C (as advised elsewhere on the forum).


The heating seems to have released most of the gas. After 30 minutes the solution is clear enough to shine a lazer through although some bubbles remain on the base of the container.

Next step SMB...
Mark