Problems with SMB

[mitchd]

Hi all,

I have been dropping gold out with iron sufate (copperas) for a long time with only once I did not get rid of all the nitric acid. Now I have tried to use SMB with nothing but problems. The gold just will not drop out and I need help to understand why.

there are now 3 lots that nothing has happened and the more I try to do something with it the worse it gets.

all works fine up to the point I add SMB, the liquid goes clear and nothing happens, add more SMB and still nothing, added a little lye and nothing, but for just an instant i saw some brown, so I added more lye and the hole batch went brown red but will not settle to the bottom. So I ask what should I do from here?

Yes there is gold in the liquid. one batch has around 10 gram, one with 4 to 5 grams and the other is unknown but I think 8 to 10 grams.

one batch was done with clorox and HCL. added water and a white powder came down, filtered and added SMB mixed in water. This one I got a little really black mud but only after adding a little lye.
and the other two were NHO3 and HCL and I did simmer the liquid down 2 time and added HCL to the syrup so NHO3 should not be an issue. added water let the white powder drop out, filtered and added SMB mixed with a little water, went clear but then nothing and then added a little lye and most likly way to much lye.. This is the one that is now a cloud of red brown stuff that is still floting around like a cloud.

Had I use iron sulfate I would have been long done with these batches.

Is there any hope of getting the gold out with out starting over?

Thanks

Mitchd

 

[Geo]

perhaps your not waiting long enough for the reaction to take place. SMB (sodium metabisulfite) is dissolved by water and evolves SO2 (sulfur dioxide gas) in solution. its the SO2 that precipitates the gold. when you add the SMB and the solution goes clear, thats the first chemical reaction. the next is not as rapid, you may be just too impatient. copperas is more instantaneous. next time you try, just give it more time. if the solution has a low concentration of gold, it may only appear as a light dusting on the bottom of the container the next day.

 

[philddreamer]

Mitchd, I echo Geo's advice.
If I may add another tip, heat the solution & you'll find that 9 out of 10 times the stubborn solution will "give up" the gold! :mrgreen:

Take care!

Phil

 

[mitchd]

THANKS!!! I have the one with the clouds in the sun right now (I live in Arizona and it's 100 degrees out side) and there is a little bit of very very fine dark materal in in the bottom of the coffee pot and I will move it to a electric warmer later today. It is true that I wanted to see some thing happen right away like with the iron sulfate, but now I will wait a over night befor doing any thing.

Thanks for the help.

 

[lazersteve]

What is your source of SMB?

 

[kurt]

I have to ask the same question as steve asked - another words is it bisulfite or bisulfate - it makes a difference.

as long as you are "sure" there is no free nitric SMB should drop your gold relatively quick. I have always been able to come back to mine decant & start the washing process 2 -3 hrs after adding the SMB

Best way to be sure there is no free nitric is to add a gold button ad heat till there is "no more" reaction. At least that has worked better for me then the evaporation HCL method.


Also - what was the source of your gold - was there a tin factor that could have formed colloids

Kurt

 

[mitchd]

I looked on the package and it is bisulfite.
With one of the lots, tin might be a problem and all that dorped out was a very very fine black materal that will not filter, it goes right through the filter.
The gold was from both computer cpu's and gold filled items and I did not do the HCL and the burning of the items, they were done before I joined the Forum. I put the cpu's and gold fill in NHO3 and water in a crook pot and coffee pots for the pins after they came of the cermanic waffer but all the NHO3. I filtered out the larger foils with a stainless steel coffee filter and all that was left, all the very fine stuff was dryed and saved and this was put into a cofffe pot and HCL was added and i waited for 24 hours then poured the HCL off and then I added AR did the evaporation twice add HCL each time and then the SMB. All I got was the very fine black materal. tested the left over liquid with SnCl and it came out clear but I keep the liquid.

Mitch

 

[Geo]

from your description, i can see a couple of places where the process could have gotten sidetracked. never filter through metal of any kind. next, when you dissolved the base metal in nitric acid and then did a hcl wash before introducing AR, your gold could have already been dissolved in the hcl wash. i hope you saved this wash solution so you can test it.you should test with stannous after each step, it is what keeps you informed of whats going on in your solution. when you wash, test your solution AND test the wash solution to be sure you didnt remove any values.i test each and every step of the way, that way i can catch a mistake before i have gone several different step and then have to work backwards to find my values.

also, make absolutely positive that the stannous chloride is good. buy,swap or make a 1 grain sample of 24k gold to dissolve for a standard test solution to test your stannous chloride against. i will be the best $10 or so you have ever spent when you find out how vital it is to have it.

 

[kurt]

Geo - the steel coffee filters Mitch is talking about is most likely made of stainless steel (ultra fine screen) & they work fine for filtering foils that were recovered with nitric. I have 2 of them that I have been using for going on 2 years now - nitric is "stored" in SS drums. Just don't use them with HCL &/or AR.

Mitch - I am betting your problem is 2 fold (1) I am betting you have free nitric yet. The evaporation HCL addition method of getting rid of free nitric is a bit tricky. If you don't evaporate down far enough before adding the HCL the added HCL will not expel the free nitric & there is a fine line between evaporating far enough for the HCL to do it's job & evaporating to far to where your AuCl starts forming a crust.

You can tell if you evaporated far enough or not. When you ad the HCL you should get a strong fizz & a puff of brown smoke. If you only get a week sputter & white smoke you did not evaporate far enough. One is the chemical reaction of the nitric being expelled - the other is just the cold HCL hitting the hot AR.

If you don't evaporate far enough to get the chemical reaction to expell the nitric - it doesn't mater how many times you do it - you will still have free nitric. --- That is why it is important to calculate the amount of nitric just needed to dissolve your gold (so you don't get a lot of free nitric) & then go with Harolds method of adding a gold button with some heat to use up any possible free nitric. Then you don't need to evaporate.

(2) I am betting you have a tin problem aswell that has formed colliods (the cloudy that goes through the filters) most likely from the gold filled you had in the mix. - This is why incineration & HCL treatment of your foils is important before going to AR. (I prefer to call it roasting rather then incineration)

In assaying they call it an ozidation roast. Put your foils in a stainless steel pan & heat to dull red on a burner (I use a single burner camp stove) & stir several times to get the foils on top to move to the bottom of the pan where the heat is & the foils on the bottom to move to the top where the oxyden is. This converts the white tin paste to a greenish gray tin oxide that can then be treated with warm HCL washes to rid the tin oxide. ---Filter & wash foils with water - force dry - then go to AR.

What I would do at this point --- cement your solutions with copper (I would pour them all together) you will most likely get a dirty messy cement as it will co-depsit tin with the gold & it will form some CuCL that comes down to.

Wash (with water) & dry your cement - do the oxidation roast & HCL wash. At this point you might get away with doing the normal gold powder wash - but I would would dry it - weigh it & re-treat with AR

you may - or may not get all your gold back with the copper cement. Due to the colloids some may stay in suspention & you can't test for it - its just there in suspention. --- So I would cement the copper from the remaining sollution with iron & re-treat to rid base metals (coppor &/or tin) & see if any gold was left behind in the copper cement (it may or may not be enough to mess with) Cementing the copper will assist the colloids in co-depositing with the copper.

And don't feel bad - I learned all this the hard way to - & what you learn is to not skip the oxidation roast (incineration) & HCL treatment of foils &/or to use just enough nitric to dissolve the gold & to use Harolds method of riding free nitric with a gold botton & heat.

And just a note - it does not matter what precip reagent you use to drop your gold - you wont get it all if you have free nitric.Cementing with copper will get it all as the copper use's up the free nitric - but you also get CuCL forming from the HCL.

This post is open to comments & corrections as it is posting my experience from my mistakes.

Kurt

 

[mitchd]

It looks like I have a lot of work to do on getting rid of tin.

It is strange that this issue has not come up in a year of using iron sulfate and then the 3 times I use SMG all I get is colliodal gold with tin and nothing else and about 10 grams of gold missing.
I am sure that I lost some gold due to the tin problems and just did not know it. My yields were what they sould be and I just washed to colliodal gold away.
since the SMG problem I have done 2 more small lots with iron sulfate with no problems of very very fine black powder they came out nice.

I have all the spent AR with iron sulfate from the last year and saved all the liquids from the SMB lots, so there should be some gold waiting to be recoved and it soulds like a good project to start on for this summer.

The place where I get the SMG could have labled the SMG wrong, they make there own lables and in the past have given me the wong stuff, asked for sodium nitrate and got sodium nitide. So I would like to ask what would happen if I had the bisulfate and not the bisulfite.

Thanks of all the input and I will now strat to roast the items befor adding the HCL and it seems for me that I like the iron sulfate better than SMG if only for the fresh air in the back yard when using iron sulfate, not much of a smell to it and I really like to see some thing happen right away.

Thanks again.

Mitch.

 

[butcher]

Kurt, I enjoyed reading your post.

 

[unitedgl]

Iam also having problems with dropping my gold with SMB (Bonide stump remover). Fine black powder and very little of it after 6 tablespoons of SMB.

I removed foils and small bits of gold plate from fingers, memory boards, and cpu’s using AP works great (but lots of trash from boards (green)

….washed cleaned with water ,

then used HCL on hot plate for about 3 hours, repeated this process 2 times

washed, and put in room temp HCL/CL for about 6 hours,

filtered out the solid trash and solution was orange

added SMB and the solution turned brown

black find dust at bottom, and very little of it, solution still test positive for gold after way to much SMB with full reaction every time SMB was added.

I need help iam losing all my gold

 

[Geo]

Iam also having problems with dropping my gold with SMB (Bonide stump remover). Fine black powder and very little of it after 6 tablespoons of SMB.

I removed foils and small bits of gold plate from fingers, memory boards, and cpu’s using AP works great (but lots of trash from boards (green)

….washed cleaned with water ,

then used HCL on hot plate for about 3 hours, repeated this process 2 times

washed, and put in room temp HCL/CL for about 6 hours,

filtered out the solid trash and solution was orange

added SMB and the solution turned brown

black find dust at bottom, and very little of it, solution still test positive for gold after way to much SMB with full reaction every time SMB was added.

I need help iam losing all my gold

how long did you wait before you tried to precipitate the gold after you dissolved it? be careful of false positives. is the test brown or purple?

 

[butcher]

The solution can give a false positive in the stannous chloride test, when too much SMB has been used.

I am not sure how much gold you dissolved but it is possible the black powder is all of the gold that was in solution, was there any un-dissolved metal in the materials you leached, if so there is where I would look for gold, another possibility is colloids from tin in solution, usually filtering will give clues if tin is in solution, when and if you have trouble filtering the solution, another possibility is free chlorine, I doubt free chlorine gas in solution is your problem with the amount of SMB you used, a boil of the solution would tell if I am wrong here.

You said you filtered out the trash (what kind of trash, what else does these filters hold), it is also possible the gold is in that, or any un-dissolved metal from the original leach (if all of the metals were not dissolved into solutions).

Was the trash you filtered orange or was the solution orange, I did not understand which; the solution should normally be a clear yellow color using the HCl/bleach method,

If you did not throw anything away you have not lost your gold, sorry I cannot tell you where it is at right now, as there can be several possibility's depending on your process.

 

[unitedgl]

Hello Geo

Waited overnight (12 hours) before I filtered the HCL/CL solution and after filtering,
I waited 20 minutes on one batch and 10 minutes on the other before adding SMB.

The positives were brown not really purple at all.

Hello Butcher

Leached materials after filtering the HCL/CL solution were plastics, most all base metals were removed in a hot HCL solution prior to HCL/CL solution.

The HCL/CL solution was orange, the trash was green and brown parts of computer boards.

All of theses batches are tests batches 6 to 10 grams I still have the main load and want to make sure I have the correct process before processing the main batch.

 

[Geo]

brown is a false positive. im sorry, but it seems you may have all the gold that was in the solution.

 

[butcher]

unitedgl,
You stated;
"(lots of trash from boards (green)".
"The trash was green and brown parts of computer boards".
"Leached materials after filtering the HCL/CL solution were plastics".

From these and other statements you have made, like the over use of SMB, and waiting short periods of time to attempt precipitation after using bleach as an oxidizer gives me some clues, to several of your problems, my suggestion would be to step back and look at how your processing the materials from the very beginning all the way through the process, step back and look at how to improve your techniques, and skills.

A person can process from dirty materials or solutions, but only if he has to, and if he understands the problems he will face and how to deal with them, but this same person will also know how to clean up the materials in pretreatments and would never cause these problems if they can be avoided.


I feel your making dirty solutions from the beginning and compounding your troubles all the way through your system.
Mixing these materials "(gold plate from fingers, memory boards, and cpu’s), was your first mistake, unless you had an understanding of how to deal with the solution, they should be processed separately.

My suggestion is if you have memory fingers, use these to learn on, go through the forum and read Laser Steve’s older posts, and visit his web site, learn to process memory board, prepare the close cut fingers before they ever come close to acids (this keeps solder out of the system and minimizes the solder mask involved, keep solder and tin completely out of the equation, pay close attention to the small details of the process, Steve teaches, he teaches very good methods and lab practices, pay close attention to the amounts of oxidizers that are to be used in each step of the process, and other small important details, understand the when, how and why of each step, get a good understanding of the small details how much when and why you add ,or do certain things, once you have a good understanding of the process begin with small experiments, ones you can verify that your doing it properly, and also know exactly where and how much gold you have all the way through the process, treat this like a scientist would, keeping your lab and technique in a fashion for getting good results as you follow your experiments through the details, and keep notes and following the directions you have studied, the fingers are a great tool to learn on, they are very simple to process, once you get good results from the small experiments work with these on a larger scale, learn these well before moving further in your studies, to materials you wish to process that can be more difficult process, this way your learning good lab skills, and getting gold, and good results from the time you invest in this, not wasting time scratching our head wondering what went wrong and where you gold is going.
This is just my suggestion, to help you get better results, and more gold in your pocket.

 

[Marcel]

then used HCL on hot plate for about 3 hours, repeated this process 2 times

Did you keep the HCl ?
Check it for gold. 2 x 3 hours on a hot plate may have dissolved some of it.

 

[jeweler1]

I had a similar problem with SMB (Bondite stump remover).
I process 2 beakers at a time dissolving my metal with AR, when the process is finished I usually wait till the next day to precipate. This process has worked flawlessly so far but not this last time.
I do all this in a vent hood and use rubber tipped tongs to pick up beakers so I never consider “Heat” to be a factor
This time I had 2 identical beakers with gold dissolved in both and I wanted to speed up the process so instead of waiting to the next day I only waited about an hour. I put in SMB as usual, waited (another hour) saw gold on the beaker bottom and no bubbles so I began to add more .One beaker went as usual (fine brown powder precipitated out settling to the bottom. But the other fussed gave off brown gas and did nothing (both were identical) I added more SMB and some Urea still nothing .The other beaker was finished by this time (I tested with Stannous) no gold left in this one but the other still wouldn’t precipate? Than I realized it was getting very hot (it was boiling) I finally felt it with my hand the heat wouldn’t go away bubbles were constantly forming. And no gild? So I put the beaker in a bucket of cold water to cool it and walla the gold fell. Heat was causing the gold to re dissolve just after it was produced. I never figured heat as the problem but someone on this forum said to use Ice to dilute with and I should have listened.
Anyway I wonder if Heat could have been your problem I know I will pay more attention to it in the future

 

[freechemist]

mitchd: all works fine up to the point I add SMB, the liquid goes clear and nothing happens, add more SMB and still nothing, added a little lye and nothing, but for just an instant i saw some brown, so I added more lye and the hole batch went brown red but will not settle to the bottom. So I ask what should I do from here?
Yes there is gold in the liquid. one batch has around 10 gram, one with 4 to 5 grams and the other is unknown but I think 8 to 10 grams.

To reduce 1 gram of gold, at least 1.0 g of sodium sulfite (Na₂SO₃) or 0.72 g of sodium-meta-bisulfite (SMB; Na₂S₂O₃) is needed. In my practice I used an excess of not much more, than about 10% over the calculated amount. Thus, for the 10 g Au-batch about 8 g SMB should be sufficient. In addition, it is important, that the mixture to be treated shows always a clearly acidic reaction, that means, excess acid has always to be present.
In neutral or slightly alkaline medium a great excess of sulfite can lead to soluble gold-sulfito-complexes, like they are used in electroplating, in place of cyanidic gold baths. From what you cite above, I guess, that your mixture does no more contain any excessive acid, and therefor probably deposes some brown red, gelatinous iron-hydroxide (Fe(OH)₃; steel coffee filter?). Adding lye to your mixture in my eyes was really not a good idea.

@unitedgl
Like butcher, I think, that you overdid it with your SMB-addition, and I can only support, what he tells you about "Good Recovery Practice". - Did you control pH-values (pH-paper)? - As maybe a "shot into the blue", I suggest, that you take one portion of the supposedly clear and scrap-free, too much SMB containing mixtures, heat it up to about 80^oC and add slowly, in small portions and under constant stirring, if possible, fairly concentrated HCl, until the whole mixture reacts strongly acidic (pH 1, even lower). If there was excessive SMB, and gold still present, you should smell the odour of SO₂ and, eventually, see some precipitated gold. After another 10-15 minutes heating and stirring, let cool down and deposit any precipitate. Test the overnatant, clear liquid with SnCl₂, to verify, if there is any gold left in solution.