Can someone help me?

[Rmwatson78]

After using agua regia on about 2500 grams of gold filled jewelry, I have about four ounces of what I thought would be pure gold powder but after trying to melt it with a torch, I can tell it's far away from being pure. Now that's it's in powder form what would be the best way to get out any base metals and purify it?

I know how some of you dislike stupid questions and I finally spent the hundred bucks for a hardcover copy of Hoke's book but I won't have it till Wednesday and would really appreciate any advice.

Also, if SMB is a "selective precipitant" why does it appear that I have other metals still?

 

[Geo]

SMB decomposes into sulfur dioxide gas when mixed with acid. It is selective in a fairly clean solution with only light contamination. If you dropped the gold from a solution with heavy copper contamination, the copper will precipitate out as copper sulfate. When you try to melt it, it turns black like syrup and makes a mess. It even looks like brown powder when dry.

 

[4metals]

You will always be best served by processing your gold filled in a nitric acid distilled water mix. That will leach out base metals and leave base metals in solution. Whenever using aqua regia you should always strive to eliminate the base metals first before using Aqua Regia to bring the gold to its final purity.

One of the things that will cause you trouble with gold filled directly digested in AR is that an excess of base metals in solution will start to drop out values as the acid becomes saturated. Many refiners lose values in the insolubles they filter off from the digestion because of this.

SMB is the preferred precipitant but in a solution saturated with base metals it is not easy to get it to drop clean gold, and the precipitate should be re-digested and dropped again to get higher purity.

An excellent video on processing gold filled made by a member is on this thread http://goldrefiningforum.com/phpBB3/viewtopic.php?f=39&t=21765&p=226969#p226969
Check it out, it is only 18 minutes and he is using the preferred method.

Welcome to the forum, and enjoy reading Hoke.

 

[Rmwatson78]

I watched the video and after going through some more bulk gold filled material, I am noticing quite a bit of it is magnetic. Is there a different process for this since he states to use only non magnetic gold filled scrap for the batch?

 

[nickvc]

The one big problem with gold filled is the different base metals used to lay the gold over, I have come across alloy with tin in and that's no fun.
As 4metals said your are best served to digest in nitric first and dissolve as much base metal as it can, filter and then incinerate then into HCl to remove further base metals then AR.
It's a great source of gold but like many materials it has its challenges especially when your refining mixed material.
With the gold powder you have already try soaking in cold HCl, if you have a magnetic stirrer it helps to use that, this should remove some base metals and make your second AR digestion cleaner.
Keep us posted as to your progress.

 

[malikjob07]

try to use (borax + boric acid) when you melt your stuff....

 

[NobleMetalWorks]

You could also use solvent extraction.

Butyl Diglyme, or as it is sometimes referred to as BDG, if used properly, can achieve high purity in one refining process. If cleaned properly you loose very little of the BDG and can re-use it again.

In dirty solutions, or solutions with base metals in AR that are problematic you can extract the Au with very little other metals following it into the BDG. You can extract gold from solutions that contain Pt and Pd, leaving those metals behind in the solution as well.

Add BDG to your dirty solution, use a stir plate with stir bar to mix the BDG with the solution as BDG is oily and will stay on the top and not mix with the solution unless you do.

After it has been mixed well and the BDG is loaded with Au, let it stand until the BDG once again floats to the top which should only take a few minutes, then pour into a separatory funnel. I allow the BDG to float to the top prior to pouring into a separatory funnel, once you do pour the solution into a separatory funnel, allow the BDG to rise to the top again. It should be a gold/yellow/orangish color, it will be different colors of gold/yellow/orange depending on the amount of gold present. The more orangish, the more gold is present in the BDG. Sometimes the BDG almost looks brown.

Open the bottom of the separatory funnel, allow the AR solution to drain until there is no more AR solution in the funnel.

Next, use a new beaker and drain the BDG into the beaker. Add a weak solution of HCl of 5% HCl, this is how you remove base metals from the BDG. Put back on the stir plate with a stir bar and stir the solution well. The HCl will change color as the base metals are removed from the BDG by the HCl. Some people pour the HCl directly into the separatory funnel, however, the HCl will not come into contact with all the BDG unless it is stirred/agitated well.

Again, pour the solution into a separatory funnel and separate the BDG from the HCl solution. You may need to repeat this process again until the HCl no longer removes base metals from the BDG. I do this wash using this method 3 times regardless if the HCl changes colors the second time as this seems to work best for me.

Drain the pregnant BDG into another beaker and place on a hotplate/stirrer and heat to about 180 F or about 82-83 C. Add an equal amount of 10% hot oxalic acid with the stir bar on slow. Do not boil the solution! Allow the solution to stir for about 4 hours. The gold will precipitate and fall to the bottom as a very fine sand. Filter through a filter cloth, wash the gold sand, melt with borax and you should have produced fairly high purity Au.

After you have recovered the gold, use HCl and a separatory funnel again, and a solution of 5% HCl to wash the BDG one more time. Allow the HCl to drain off, recover the BDG and you are ready to use it next time.

Scott

BDG floating on top of AR solution in separatory funnel.
https://www.dropbox.com/s/y1o31ondge6gylp/2013-02-16 16.27.05.jpg?dl=0

AR solution drained off of BDG
https://www.dropbox.com/s/2ek9fnwkqjmmeya/2013-02-16 16.28.15.jpg?dl=0

 

[maynman1751]

Great directions Scott! Thanks! 8)

 

[NobleMetalWorks]

Great directions Scott! Thanks! 8)

Not a problem, BDG has been discussed on this forum, but it doesn't seem to be a process many people use, I suspect it might be that BDG doesn't seem to be as readily available as acids and/or precipitants but it does have a few distinct advantages. If used properly you only have to refine once to obtain at least 99.9 purity, and if careful you can easy obtain 99.99+. You can recover extract gold from solutions that have excess nitic acid without driving off the Nitric a ID, and from dirty solutions where there are many other base metals pressent. Of course it is always better not to work with dirty solutions specially when base metals can be resolved easily prior to dissolving gold, and if you are making small additions of Nitric, only as needed you don't need to be concerned overly much about excess Nitric Acid. I use it mostly because I can obtain high purity with a single wet chemistry process.

Scott

 

[Rmwatson78]

Scott,

That was extremely great information and exactly what I was looking for. Do you know of a reliable supplier of BDG? I bought a few 30ml bottles on Ebay that cost me like 30 bucks a piece, but in all I am processing about 6,000 grams+ of gold filled jewelry and I seriously doubt that these tiny and expensive bottles will be enough. How much BDG do I need to process a fairly large batch?

 

[Rmwatson78]

And I still don't understand how or what processes would be different when extracting gold from the gold filled jewelry if the items are magnetic or not. It would appear that atlas half of the gold filled jewelry pieces I'm working with are magnetic.

 

[4metals]

I do not think the BDG process will serve you well with gold filled material. You will have a saturated solution of base metals with very little gold. Your best bet is to get rid of those base metals and nitric excels for that. Your chances of losing gold because the gold cements out of solution are high. That is a big problem with aqua regia because one assumes everything that doesn't dissolve is silver or no value. In nitric parting you assume the gold is what is insoluble as nitric does not dissolve gold. It is much less likely to cause problems. BDG is not a process for those new to refining. It is wonderful for high purity gold but not for high purity gold from solutions saturated with base metals.

If a lot of your gold filled material is magnetic, then it is likely not gold filled. More like plated. That will make your gold yields even lower as the plated material is always less than gold filled.

 

[NobleMetalWorks]

4Metals is right, this is not the way you would normally process gold filled, nor plated. I only suggested this because I have had good results using BDG with other people dirty solutions where only gold was present among base metals. BDG is also not a process that those who are not very experienced should use as it takes good lab practices to ensure it is properly done, and this takes experience.

BDG can be reused so long as you clean the BDG after each use with HCl.

The process which 4Metals has outlined is probably the most reasonable and best suited for gold filled jewelry. I only posted what I have because you already have a dirty solution in which it seems you are focused on extracting the gold.

Scott

 

[Rmwatson78]

I do not think the BDG process will serve you well with gold filled material. You will have a saturated solution of base metals with very little gold. Your best bet is to get rid of those base metals and nitric excels for that. Your chances of losing gold because the gold cements out of solution are high. That is a big problem with aqua regia because one assumes everything that doesn't dissolve is silver or no value. In nitric parting you assume the gold is what is insoluble as nitric does not dissolve gold. It is much less likely to cause problems. BDG is not a process for those new to refining. It is wonderful for high purity gold but not for high purity gold from solutions saturated with base metals.

If a lot of your gold filled material is magnetic, then it is likely not gold filled. More like plated. That will make your gold yields even lower as the plated material is always less than gold filled.

It is because I bought a crapload of gold filled watch bands where mostly just the tops are 10k or 12k gold filled. I didn't want to dismantle them if I could avoid it, but it's not as bad as I thought. Probably will still take me a few days to take off the tops.

 

[Rmwatson78]

4Metals is right, this is not the way you would normally process gold filled, nor plated. I only suggested this because I have had good results using BDG with other people dirty solutions where only gold was present among base metals. BDG is also not a process that those who are not very experienced should use as it takes good lab practices to ensure it is properly done, and this takes experience.

BDG can be reused so long as you clean the BDG after each use with HCl.

The process which 4Metals has outlined is probably the most reasonable and best suited for gold filled jewelry. I only posted what I have because you already have a dirty solution in which it seems you are focused on extracting the gold.

Scott

What if I redissolve the powder I get from the first aqua regia run with the powder I get from the watch tops? I contacted BASF about ordering some butyl diglyme. If they send me some I could use your instructions at this point for probable success right?

 

[Rmwatson78]

What I'm ending up with after a melt w/ borax powder is in these photos. It has a shiny like surface but its dark reddish and black and seem to make needle like formations when pulled away from the crucible with a screwdriver.

 

[Rmwatson78]

I do not think the BDG process will serve you well with gold filled material. You will have a saturated solution of base metals with very little gold. Your best bet is to get rid of those base metals and nitric excels for that. Your chances of losing gold because the gold cements out of solution are high. That is a big problem with aqua regia because one assumes everything that doesn't dissolve is silver or no value. In nitric parting you assume the gold is what is insoluble as nitric does not dissolve gold. It is much less likely to cause problems. BDG is not a process for those new to refining. It is wonderful for high purity gold but not for high purity gold from solutions saturated with base metals.

If a lot of your gold filled material is magnetic, then it is likely not gold filled. More like plated. That will make your gold yields even lower as the plated material is always less than gold filled.

I just tested the tops I'm taking off the watch bands, and most if not all appear to be magnetic. Does this mean they are not gold filled as marked?

 

[4metals]

I think the first thing you should do is slow down and start reading. Processing gold filled has been addressed on this forum "ad nauseam"!

There is no magic method or shortcut for this type, or any type, of scrap refining. From the pictures you posted of your melt result something is off, you will be best served by telling us what steps you followed to separate the scrap before processing, and how you did process it.

As far as gold filled being magnetic, I guess it is possible because by legal definition gold filled is a layer of 10K or higher bonded to a base metal substrate with the gold making up a minimum of 1/20th of the weight of the piece. So the substrate could be iron. My personal experience with watch cases always involved copper or brass base under a gold filled layer. Maybe they were higher end watches or maybe I am old enough that watches were made different back when I processed them.

I always ended up digesting a much more uniform alloy because I always melted the material before processing. This was for 2 reasons, first on a commercial scale melting allowed me to put an assayed product out into the refinery so I knew what to expect in terms of gold coming back in. And second, the alloy was granulated to maximize surface area. (probably not as much surface area as the unmelted jewelry had but the first reason I gave always made granulating a necessity.)

Still it shouldn't matter, nitric will clean up steel (not stainless) and copper or brass, leaving gold behind. That gold can be cleaned up using a BDG process but I do not see the benefit.

The reason I don't see the benefit is, unless you are a commercial refiner producing high purity product, you will be selling your gold to a gold buyer who will discount the product anyway. Refining in aqua regia after the nitric parting will produce a .995+% yield which will be pure enough to get you your best price from the gold buyer (who will likely discount it anyway). If you put in all of the time and effort and chemistry to do the BDG process, your gold buyer will likely still pay you the same, so why bother?

 

[Rmwatson78]

I am actually the owner of a small jewelry store, so I'm going to keep the gold I process to make various pieces with. I guarantee I will still come out on top in the end regardless of how long or how much I spend to get there.

 

[nickvc]

I am actually the owner of a small jewelry store, so I'm going to keep the gold I process to make various pieces with. I guarantee I will still come out on top in the end regardless of how long or how much I spend to get there.

That's good to hear but it needs to pay, refining and recovery should put you ahead on initial costs so keep reading and learning, you will get there it just takes time and a lot of knowledge, it's all here and it's free so the return is down to you.
You can do this, take your time and get it right.