Wastes - The Elephant in the Room

[goldsilverpro]

There is a misunderstanding that occasionally crops up on the forum about base metals that are dissolved in acids. Many people think that the reason for dropping out these metals, with iron or aluminum, is to recover them so that they can be sold, as is, or after melting. Not so. No one will want to buy the powder and melting the powder is most probably cost prohibitive for most all of you. You'll never get the stuff melted with a torch.

So, what is the reason for dropping out the base metals? It is to convert highly toxic heavy metal solutions to much less toxic iron or aluminum solutions.

The copper, nickel, etc., solutions are definitely considered by the EPA to be highly hazardous waste. I don't exactly know they classify the Fe and Al solutions, but surely they must be ranked a peg lower.

As far as solids are concerned, I know basically how the EPA tests them. They mix up enough acid (and water) to make a solution with a pH of about 3 or 4 (I think), add the solid to this solution, and then they analyze this solution for heavy metals. In the 2 photos of copper powder that Steve posted on the link below, the pink copper metal in the 1st photo wouldn't dissolve and would, therefore, be legal, as I understand it. In the 2nd photo, the green copper compound would dissolve in the pH 4 acid solution and, therefore, it would not be legal.

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=1066

The old way to make solutions legal to dump was to drop out the base metals with an alkali, such as sodium hydroxide, sodium carbonate, or lime. The base metals start dropping as hydroxides, carbonates, etc., at a pH of 5.5, depending on the metal(s) involved. The problem is that these hydroxides, etc. will redissolve at a pH of 4 and will fail the EPA test. You're just trading one form of hazardous waste for another. Another problem is that these metal hydroxides are very voluminous. I have dropped the metals out of a drum of acid solution and ended up with a drum full of metal hydroxides.

I haven't kept up with the EPA rules. When I owned refineries, I always had my own wastes hauled off legally and, every place I have worked for (at least in the last 25 years) either had their wastes hauled or had legal treatment facilities. However, I have had a few garage operations, although not for quite a few years. I have been where you are. I know.

Some one here should find, study, and interpret the latest laws and post them under this "Legal Things" category. Legal stuff bores me to tears. I will, however, help work on the technical aspects of how to comply. If we work on it, I'm sure we can come up with a cheap way to handle these wastes.

The best technology and knowledge for handling wastes comes from the electroplating industry. Their wastes are almost identical to ours. At one time, this industry was notorious for dumping toxic wastes illegally. When the EPA and OSHA clamped down, they made an example of these people. The plating shops had to comply or, they had to shut down. Probably 80% of them went out of business. Lots of great new waste control technology has resulted.

The thing that would bring you people and this forum down is if you all dumped these solutions illegally. This is a taboo subject that no one likes to discuss. It's a big elephant in the room that everyone ignores. If we would openly talk about it, we could come up with viable solutions (no pun intended). Be good citizens. Don't ruin this for everybody else.

 

[Never_Evil]

This is just me blurting out ideas so if you dont want to waste time please stop reading NOW.

Since there is a of hydrogen, oxygen, a depending on what other solution, carbon, chlorine and such, Is there a way to turn this into a fuel? By adding baking soda it is neutralizing the solutions, but can we turn this left over solution into a hydro cell or combustable fuel? I dont have the chemical equations infront of me to know what is turned into what so I may be way off.

Is there another chemical that could push out the metals from the solution? Rather than using steel to push out the copper, could there be another chemical that could push out the copper itself? This way we can have a chem solution without and possibly break them down to other chemical solution that can be useful in other ways.

 

[goldsilverpro]

On paper, these components exist in the solution. On a small scale, however, separation would be impractical.

There are selective chemicals for copper. Offhand, I don't know what they are.

A very unique chemical, Sodium Borohydride, will drop out most all metals, as metallics (I think). At last look, it was very expensive. I have a good IPMI article on this chemical that I will reread and report back. It's very powerful. If I remember right, 1 pound will drop 8 pounds of silver. If it's gotten cheaper, it may be the way to go.

I just found a patent using SBH to drop Pt directly as metal, and not a salt.

http://www.google.com/patents?id=6a4fAAAAEBAJ&dq=5304233

 

[Irons]

There comes a point where extracting values becomes uneconomical. The problem is how to deal with these materials without spending a fortune.
On another thread, there was a discussion of using a commercial polysulphide compound to recover values but it precipitates everything. It's what it was designed to do.

If you have to pay to dispose of hazardous waste, the trick is to reduce the volume to where the cost per ton is economical.

Precipitation as sulphides works well in this respect. If done properly, there is little odor involved and the effluent is clean enough to recycle or dispose of in municipal waste streams.

one trick I use to reduce volume is store the liquids until winter and as they freeze, the ice pushes the salts to the bottom, leaving a very concentrated solution. The nice thing about it is I don't have to expend any energy to evaporate the solutions. All I have to do is leave a loop of rope in the top of the solution so that I have a handle to pull out the block of ice.

everything but the squeal.

 

[goldsilverpro]

The problem with the metal sulfides is that many of them are soluble in dilute acids. They probably wouldn't pass the EPA test.

The neat thing about sodium borohydride, NaBH4, is that the metals drop as metals, even platinum. I imagine it's gotten cheaper. The original method of manufacture used sodium metal and that's why it was expensive. It's basically made from boric acid and water. There's tons of info on the net about this chemical, including new ways of making it.

 

[blueduck]

I just looked on ebay and a fella there has 100 grams of it for $42.00 claiming that that is less than half the normal cost of it.... but we all know that ebay is over exaggerated for a lot of things related to recovery of precious metals.....

the chemistry store has boric acid for 90 bux for a 55 pound bag , and 5 bux for a one pound jar..... interesting idea to make it into a useful compound if such can be accomplished inexpensively by the "basement chemist" in our labor-a-tories <----- best Lon Chaney type voice in my head from the bugs bunny cartoons of my misspent youth.

now i have to go crack open a few of those chemistry books that other folks uploaded and ive got on my harddrive as pdf files...... just to figure out how to do such effectively or if it can be....... or find another source for procuring an already made product.....

AS far as handling wastes, I wonder if a carbon arc would reduce the wastes to a small footprint in an economical manner..... such a unit was proposed to be built in Montana in the late 70's to mid 80's and that it would reduce a ton of material to a few grams of ash with virtually no emitted gas [dont know much more about it, I was kid at the time] it sounded to good to be true but it would have stopped a lot of landfills and that would mean less dollars somewhere and the thing was scrapped.... but it may be a viable thing to build even on a small scale......

William

 

[Never_Evil]

Sounds like we may have a new path to take to recovery platinum off hard drives and possibly out of the honeycomb in catalytic converters. I appreciate the feed back on my ideas.

dennis

 

[Lou]

The problem with the metal sulfides is that many of them are soluble in dilute acids. They probably wouldn't pass the EPA test.

The neat thing about sodium borohydride, NaBH4, is that the metals drop as metals, even platinum. I imagine it's gotten cheaper. The original method of manufacture used sodium metal and that's why it was expensive. It's basically made from boric acid and water. There's tons of info on the net about this chemical, including new ways of making it.

I've used sodium borohydride many, many times. It's a very good reducing agent that only slowly reacts with water and primary alcohols (destroyed in a few hours' time, it is hygroscopic as well). It is used very much in organic chemistry as it is a clean, mild reductant and is much safer than lithium aluminum hydride which is pyrophoric. Many hydrides are becoming cheaper as they have potential use for storing hydrogen.

I know of only two effective ways (industrially) to make sodium borohydride. I am sure that it cannot be made from boric acid and water, even at high temperature.

The first method is that which uses sodium hydride, not sodium metal. Sodium hydride is nasty stuff, and unlike borohydride, is not a mild and selective reducing agent; it reacts dangerously with water, often catching fire. This is made by reacting sodium with hydrogen gas at high temperature and the process is the same for all alkali and alkaline earth metal hydrides. This is easy enough with a tube furnace, stainless piping, sodium metal, and a tank of hydrogen. After you have your hydride, you go about it industrial style, and react it with borane (BH3<->B2H6) which is NOT a good thing to work with as it is highly flammable, plus it's hard to buy, and extremely dangerous to make.
It does react very nicely with NaH, NaH+BH3->NaBH4, and is clean. The borohydride is extracted with triethylamine or diglycol methyl ether (diglyme). That gives the best yields. You can use borosilicate glass (as in what beakers are made of) instead of borane, but yields are crap.


The other method is the trimethyl/ethyl borate with sodium hydride at 420F/270C from the late fifties, I think it's called the Schlessinger Process, and this isn't terribly useful, unless you have borohydride to begin with (since you can make trimethylborate from it).


Borohydride is nice, agreeable stuff for reducing platinum quickly and selectively, but it's expensive. Cheapest I've ever seen it was about $500 USD for 5 kilograms.

And Blueduck, for the $42, 100g is really cheap. It would probably cost about twice that from Fisher or Aldrich.

Still, there are other reducers that work just as well and better.
I find that the ammonium formate route works well though, and gives a clean product. Only thing that works better is using hydrazine or one of its salts (amazingly good reducer, and extremely clean, the product is nitrogen gas, ammonium cation). Too bad hydrazine is poisonous as hell, extremely explosive, and almost impossible to buy in this day and age. Straight up stuff still finds use in high performance rockets and ICBMs.

The salts are easier to work with though, and can be made very cheaply (about $15/kilogram), if anyone wants to know how, just ask.



Back to the pertinent topic, waste disposal. For me, it's always been a question of quantities and what it is. Somethings, like mercury, cadmium, lead, thallium, silver chromium, manganese, copper and vanadium just don't go down the drain and must be disposed of properly. As goldsilverpro mentioned, solubility changes depending on the compound and the pH. Some compounds won't be soluble in a base, but will dissolve right up in an acidic environment and vice versa. I always try to reduce the metal to the lowest oxidation state possible, preferably its metal form with a few exceptions (mercuric sulfide, for instance, is better than free mercury metal). Sulfides and hydroxides are generally not soluble at pH 5-8, but still won't be fit to sit at a landfill.

Silver chloride is practically insoluble at the small scale, but get enough solvent (water) and it will dissolve and carry Ag+ ions away. How much depends on its Ksp, or solubility constant for that particular metal salt.

I am not saying that you should let the professionals do it all, as they'll charge you a lot to do it and eat up your profits, but rather to be smart about it and use chemical sense. For metals that are bad, it's about reducing their cations, for nasty anions, it's about oxidizing them. Cyanide is a good example--paying to dispose of sodium cyanide is absolutely stupid. Add the cyanide to bleach, either calcium or sodium hypochlorite, let it oxidize to cyanate, and then dump it down the drain.

Let the pros handle mercury, cadmium, and cobalt compounds...

 

[Anonymous]

Here's what i do to clean up the waste materials. React the spent acids with sodium carbonate to precipitate out the heavy metals then vacuum filter the carbonates out then put in a jar, when there is enough of them they are roasted to drive off the co2 and form oxides. The oxides are then mixed into concrete and disposed of.

I reckon you could salvage the metals such as copper and nickel via electrolysis if you really want to, but it's more work than it's worth for small part time refiners. Any thoughts?

 

[Noxx]

I have no idea if this could work but one could heat Metal Chlorides upon decomposition to give Metal + Chlorine gas. The gas could be neutralized easily.

Just an idea...

 

[peter i]

Quite a few metal chlorides are rather volatile, and will evaporate rather than decompose.

In Denmark it is easy: As a private person any chemical waste can be handed in at the local “recycling station”. No price to pay, and no questions asked. They realized long ago, that this was the easiest way to avoid people flushing things that should not be flushed.

Iron ions are “mostly harmless” and dropping with iron would be my second choice.

 

[geekzilla]

There is a misunderstanding that occasionally crops up on the forum about base metals that are dissolved in acids. Many people think that the reason for dropping out these metals, with iron or aluminum, is to recover them so that they can be sold, as is, or after melting. Not so. No one will want to buy the powder and melting the powder is most probably cost prohibitive for most all of you. You'll never get the stuff melted with a torch...

I am a newbie so maybe there is something I am missing. I figured that recovering the heavy metals and recycling them (copper, nickel and aluminum) was the natural next step in the refining process. One reason I am interested in the whole refining process is not just for the money from the gold and platinum, but the whole idea of recycling as much as possible because that is environmentally responsible. And then, of course, money from the rest of the base metals…

Also, I don’t understand your comment about never being able to melt the powder. The melting temperature for copper is 1,984 F, gold is 1,947 F, and aluminum is 1,220 F. Nickel is extremely high at 2,651 F. However all these temperatures should be achievable with a simple propane torch.

An oxy-acetylene torch achieves temperatures of 5,800 to 6,300 F and a propane torch maximum is 3,623 F.

So, why couldn’t the copper, nickel and aluminum be recovered through melting?

 

[Rag and Bone]

They can be recovered if you want them bad enough. The trouble is finding a market for the metals recovered from solutions. You're right to utilize everything, I share that goal. Also, the amounts of base metals recovered on the hobbyist level is small. At this point I'm just accumulating the base metals from solutions until there are more options.

 

[Harold_V]

So, why couldn’t the copper, nickel and aluminum be recovered through melting?

You've missed the point.

You can, indeed, melt all of the recovered values. The problem is the cost of melting and fluxing, both for the cost of materials, and the wear and tear of equipment. Flux has a nasty way of cutting short, VERY short, the useful life of furnaces and crucibles, and you can't melt them without fluxing because of the nature of the recovered materials.

If you do some research, I think you'll find there is no market for the base metals recovered by conventional methods. That's not to say they are valueless----it's just that the typical foundry can't use them, and isn't willing to accept them. That leaves only the scrap yards, and my experience indicates they don't want them, either.

Because of the nature of the recovery procedures, the metal you recover is very finely divided, and well oxidized and contaminated with other elements. Anything you do to improve the condition of the metal will reduce any hoped for profit, eventually exceeding the value of the metals you may recover.

Understand I'm speaking from the perspective of one that has melted these metals------and in the end discarded two 55 gallon drums of recovered copper because there were no takers-----not even free.

You may enjoy a different outcome in today's market, assuming you're willing to do some research. My experience dates back to the mid 90's, when copper was worth only about $1.20/lb at the refinery. For all I know, the Chinese market may be willing to accept them.

Harold

 

[geekzilla]

Thanks for clearing that up for me Harold. I appreciate it.

 

[Harold_V]

You're welcome. I wish the message was more positive, but what I reported is what I have concluded in my attempt to do "the right thing" by trying to keep these elements in the pipeline. Sometimes you have to do what you don't want to do to preserve your sanity! :wink:

Harold

 

[Anonymous]

I read an article about electrowinning and it stated that copper cloride was
25 percent more efficient to recover than copper sulfate and copper nitrate was 15 percent less efficient. It also stated that it takes 3kwh to produce 2 kilograms. This being a little over 4 lbs of cathode copper in one solid chunk would be worth at my local scrap dealer about $10.00 - $12.00 and cost only .25 cents worth of electricy and should yeild your acid(s).

I am very interested in this because I think from electronic scrap there is more values in base metals than there is PGM content. So, in my own little way I am trying to learn how to get the Tin, Copper, Lead, and Zinc each seperated as I can sell them all. Getting the Tin at 90 percent purity sells for about $5.00 a lb.

Judging from all of the people on this forum and the marketing of various e-scrap hobby(ist) refiners there would be a large market for such service. Even if only to send them back they own copper so they can use it to cement more silver.

 

[markqf1]

The ideal situation would be to recycle it all.
The question is, what is financally and economically feasable with present technology?
With the price of all metals continuing to rise, it may be just around the corner.

Mark

 

[Anonymous]

I tried a little experiment with the copper chloride did not go so well. I did get an initial deposit of copper but it did not stay solid for long. I
I hoping that was because my solution was rather spare of copper.
I did notice that it produced hydrogen and chlorine gases not the HCL back into solution as I had wanted.

I am going to try again with a saturated solution.

 

[Harold_V]

Your problem is typical of what I experienced when I tried parting copper. Unless you can keep the feed metal quite pure, as well as the electrolyte, you get poor results. I do feel the recovering the metals electorlytically is the way to go-----just work out the kinks!

Harold