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Recycling Polish Dust...Take 2


#1

Thankyou Frank G, Michael M and Peter R for your comments,

Something I forgot to mention, our factory is in Bali, Indonesia. I
doubt if it would be worth shipping the dust to the US where the
established refiners are situated, and then shipping the refined
metal back through our less than accommodating Customs. Currently we
refine our trees, buttons and floor rejects at Logam Mulia the
largest refiner in Indonesia) but when we sent them our polish dust,
they refused to process it as is. Thus my conundrum! Any other ideas?

ORIGINAL POST:

I am wondering if anyone recycles, or knows how to recover, silver or
gold from polish dust to reclaim lost metal? Our local refiner
doesn’t want to process the raw dust. Is there some process that can
be done to refine the raw dust so our refiner will process it? I have
maybe 30-40 investment drums full of raw polish dust. Anyone?

Cheers,
Marcus Terrey


#2
but when we sent them our polish dust, they refused to process it
as is. Thus my conundrum! Any other ideas? 

I would expect someone at that refiner would be able to tell you
what sort of preprocessing they might need. One common initial step
is to burn away the organic material. This can be done in a burnout
type kiln, though it’s perhaps better to reserve one especially for
that. At the most basic level, one can do this just in a frypan, if
you can heat it enough to burn off the organic matter such as the wax
and grease binders in the polishing dust. Kinda messy and smokey to
do, though.

I’d suggest getting a copy of Hoke’s “refining precious metal
wastes”, for proper descriptions of how to do this sort of thing most
efficiently.

The next step, after burning off the organics, if I remember it
right, is to mix the result with refining fluxes, in a graphite
crucible, put it in a melting furnace, and let it go. the mass
melts, the metal eventually collects at the bottom, you pour it into
an ingot mold, and send the ingot to the refiners. but the details of
that flux mix, and the rest of it, I don’t recall… I tried it
once, about 25 years ago. Whatta mess. I suspect I wasn’t doing it
correctly…

cheers
Peter


#3

The first step, as I understand from my refiner, is to place all of
the materials in a large furnace and reduce the total to ash and
slag. Then remelt this with lots of flux / borax to help remove the
organic ash. You can then take the resulting metal and send it to the
refinery and see if they can deal with it. You can also add a
quantity of copper at this point to help remove even more of the
metal from the slag. Also search the internet for Roland Lowan’s
papers on refining. ( someone may be able to tell you the title I
don’t have it at this time although I do remember seeing it in an
orchid post a few months back) He used to do all of my refining when
he was still working. Good luck in Indonesia. Frank Goss


#4

SEE: http://www.legendmine.com/ Legend, Inc. 140 Manuel St. Reno, NV
USA
89502 ph: 775-786-3003 fax: 775-786-3613 send feedback to:
info@legend-reno.com

Small Scale Refining of Jewelers Waste by Roland Loewen, 1995, 257
pages, (Hardbound)

This book explains in graphic details the refining of precious metal
scraps containing such metals as gold, silver, platinum and
palladium. Descriptions are for small scale recovery and refining
operations. This book is meant for the practical person and oriented
to the layman. There are some fifty illustrations that visually
describe the equipment.

Quantity in Basket: 1 Code: 17208 Price: $34.95 Shipping Weight: 2.00
pounds

Jesse


#5
   I am wondering if anyone recycles, or knows how to recover,
silver or gold from polish dust to reclaim lost metal? Our local
refiner doesn't want to process the raw dust. Is there some process
that can be done to refine the raw dust so our refiner will process
it? I have maybe 30-40 investment drums full of raw polish dust.
Anyone? our factory is in Bali, Indonesia 

Dear Mr. Marcus Terrey, My idea on what you can do to help yourself,
while effective, is not very enviromentally friendly so I say this
only as and not necessarily as a suggestion. What every
refiner does with that kind of material is first to burn it. The
burn must take place in a low turbulance situation so that your metal
particles don’t go up the flu or out over the ocean. It is best to
use indirect heat with the “sweeps” on a large steel pan with just
enough heat to slowly incinerate the burnables. US refiners use what
is called a “bag house” to capture the solid particles to prevent
them from poluteing the atmosphere. This burning reduces the amount
of waste considerably and inceases the percentage of metal greatly.
So your 30 - 40 drums of raw polishing dust will likely become 1 or 2
very heavy drums of ash etc… What can then be done is using a very
large crucible in a pretty hefty furnace, add this (ash, etc…) with
generous amounts of about 75% borax and 25% boric acid comparitively
on the top. What the boric does is float the “crap” on the top and
the heavier metal will sink to the bottom. You then drag off the
"slag" which in a perfect world would not contain any metal and
discard it appropriately. (Note: I don’t live in a perfect world.)
Eventually you would have a lump of metal in the bottom of your
crucible that consist of various metals. You could then send this
to your refiner who would hopefully handle it appropriately. All
this takes a lot of work.

In the real but not so pleasant world the burnt material is ball
milled (broken up into very small homogenous ash), sampled and then
some refiners assay that and pay based on that assay. Sometimes they
do the Boric thing first, ball mill the remaining boric slag, assay
both the metal and powder, and then pay based on the two sets of
numbers. If your refiners won’t take the burnt material then you
have a whole new problem. Often the burnt material ends up in open
pits of cyanide solutions in copper mines in 3rd world countries.
Hopefully the cyanide lakes don’t leak or don’t overflow when it
rains. The cyanide dissolves the metals, the liquid is pumped off,
and the metal is dropped out by various chemical means. This is one
of the dirty little secrets of the jewelry industry that we pretend
doesn’t happen.

I am not sure if this will help you or scare you. My intentions
were honorable in any event. J. Tyler Teague JETT Research
(Jewelry Engineering, Training, & Technology)


#6

just to add to J Tylers post after burning run a magnet over the
residue to pull out any iron particles. it will greatly improve the
melt. andrew goodell


#7

this book suggested by Peter is also available at Legend mine supply
: http://www.legendmine.com/

Refining Precious Metal Wastes
by C. M Hoke, 1940, 362 pages, (Hardbound)
Code: 17205
Price: $38.50
Shipping Weight: 2.00 pounds

This book does not cover assaying of metals but does cover in detail
the secondary refining of precious metals to permit their further
employment in art, science, and industry.

jesse


#8
 just to add to J Tylers post after burning run a magnet over the
residue to pull out any iron particles. it will greatly improve
the melt. andrew goodell 

One caution here. If you process any cobalt/platinum work, know
that cobalt/platinum alloys are magnetic enough to be picked up by
your magnet when you thought you were just removing iron. That makes
for costly dust you might be throwing away…

Personally, if it’s mixed metal sweeps or other waste, I use a
magnet to remove sawblades and larger bits that are easily identified
as steel waste, but the dust goes back in the waste that might
contain gold or platinum, since now and then some of the platinum
things we work on are the cobalt alloys.

Peter