Dealing with Waste

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Fragum

Member
Joined
Nov 23, 2007
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Location
NW Arkansas
I have been roaming this site for a few weeks, and with Hoke's book on it's way (fyi Harold) and Steve's DVD's I should be ready to start recovering pm's here pretty soon.

I do have concerns about how to correctly deal with wastes. I am looking for some insight into how you guys deal with this issue.

No reason to reinvent the wheel here. Thanks in advance for your input.
 
Waste treatment for the small refiner.

Most of the practicing alchemists on this forum generate waste liquids which, if you have the time and desire, can be neutralized and made free of toxic metals rather simply. The required supplies are simply a pH meter, a few plastic tanks (15 gallon size is ideal), an aquarium air pump and some tubing, slab of copper, some scrap iron. The advantage you have in being a small producer is that you have the time to let the solutions sit and react before proceeding to the next step. Because of this you do not need expensive pH controllers or a filter press and the associated pumps.

The procedure that follows is for your acid waste only, it is not for cyanide or leaching type wastes, only the spent acids used to digest the metals you have refined.

Select a plastic tank to use as a holding tank for your spent acid, if it is translucent it makes it easy to see how full it is. This tank should have a lid to keep out rainwater and it should be kept where it will not freeze. What we will do in this tank is a process called cementation, whereby you hang a slab of copper metal in the waste acid to displace any precious metals which may still be in solution. When the tank is approaching full, maybe a few inches from the top, the copper is suspended in the tank and the solution is agitated to expose the copper to as much solution as possible. An easy and inexpensive trick is to buy an aquarium pump and some tubing and weigh the end of the hose down so it is close to the bottom of the tank and let it bubble away. Overnight should suffice. The copper bar will have displaced any PM’s in the solution which will settle to the bottom. Don’t expect a lot of material to settle from each load, but in time the material on the bottom is collected and refined for values. Allow the solution to settle after removing the bubbler and the copper bar, a few hours should do it. Now siphon the acid into another tank, being careful not to suck out any of the settled material. Usually a few inches of solution left on the bottom will prevent you from sucking out the solids and it is just left in the tank as you start to accumulate more waste acid.

A simple siphon device to prevent siphoning all the way to the bottom can be easily made as follows; cut a length of ½” CPVC pipe about 24” long, glue on a tee, followed by a 6” piece of pipe and a cap on the end. I prefer to use half inch “copper pipe sized” CPVC because it is nice and slim and easy to find tubing to slip over the end. Now you will need some flexible tubing to slip snugly over the end of the pipe opposite the capped end, about 4 or 5 feet will do. You will now have a hose and a short length of pipe which has an opening (because of the tee) 6” from the capped end. To start a siphon, place a finger over the hole in the tee and fill the entire hose and pipe with fresh water, then quickly submerge the capped end and place the end of the hose lower than the solution level in the tank. With this setup you don’t have to worry about sucking the solids off the bottom of the tank. One drawback is the tank you are siphoning from has to be higher than the tank you are siphoning to, so you’ll have to lift the full cementation tank on to a table to siphon it completely.

This second step can boil over if you’re not careful so I would transfer the liquid from the 15 gallon cementation tank into a 30 gallon tank if you’re going to process this all at once. Add your air bubbler to the 30 gallon tank and start bubbling. Check your pH, it should be close to zero when you start. Slowly add soda ash to the bubbling liquid, it will foam and generate CO2 so be careful not to boil it over, since an aquarium pump doesn’t move the liquid aggressively, add the soda ash slowly and stir with a pvc pipe occasionally to make sure it all is dissolving. Slowly over the course of a day or two raise the pH to 2.5.

Now you will add scrap iron to the tank, it can be done by placing the pieces of iron directly in the tank and fishing them out later, (needless to say with rubber gloves on) or you can get a plastic tank that fits into the 30 gallon tank, drill holes in it on the sides and bottom, and immerse the iron in all at once. The iron will displace copper and other metals from solution and slowly dissolve in the liquid. The iron will get coated up and a good shaking will remove the coating from the iron. After a few hours, the solution will have a green tea look to it which is ferric chloride. If you leave the iron in longer it will continue to dissolve so remove it and rinse it well. The copper and other metals will accumulate on the bottom of the 30 gallon tank where they are from time to time collected and dried.

You now use the siphon device to siphon the liquid to a final tank. Your primary contaminant now is iron. You can raise the pH with sodium hydroxide and the iron will drop out of solution which is quite easy to recognize. Unfortunately this liquid is a bit gel like and doesn’t filter well. A better way is to raise the pH with Magnesium hydroxide, the resultant sludge settles better and dries nicely. You cannot measure the pH of the reaction while adding magnesium hydroxide because it is slow to change the pH and you will over add, just go slowly and when you get the color change you’ll know the iron has dropped out. Let the iron settle and you can siphon off the now clear liquid to discard.

Note; in the time since this was originally posted some members have had issues with incomplete dropping of the values from their waste. This is usually because there is not enough exposure of the values in solution to the copper. The key here is time and surface area. As this process only works when the metals beneath copper on the electromotive series chart come in contact with the copper, it is important to have a lot of circulation (as in the air bubbler) and enough time for the reaction to go to completion. I have had great success using copper in the powdered or even dust form to carry out this cementation very quickly. (the metals below Copper on the electromotive series are basically all of the precious metals and Mercury)

Please remember your stannous chloride test will indicate when all of the values have been removed from the solution.
 
4metals said:
I'm sure you, Lou, and Harold could shed some valuable insight about waste treatment and witnessing refining.
Sadly, that is not the case with me. I didn't have a clue about proper interaction with refiners when submitting a lot of material, although I feel I was treated fairly by GD Resources when I delivered some of my waste material that had been treated with cyanide previously.

As for disposal issues, my routine was to cement the solutions with scrap steel, just as you suggested, but I discharged the iron bearing solution instead of attempting to remove the iron. Had you not posted the procedure, I would have had no clue how to accomplish that task.

I had a unique setup, very unlike that of anyone else on the forum. When I refined, I was a resident of Utah. I lived in the Salt Lake Valley, where affluent from sewage processing plants ended up in the Great Salt Lake, a body of water that is mined for some elements, such as magnesium. It would be safe to say that discharging the iron wasn't much of an issue in that the lake is devoid of life forms aside from brine shrimp and a strange little black fly.

Were I to refine today, I would benefit greatly from your contributions. It certainly is nice to have someone aboard that has your experience.

Harold
 
The big companies I was associated with almost always had the material hauled by a legal hauler, such as Univar. Of course, they had huge quantities of waste. About 5 years ago, in Houston, they charged less than $1/gallon to pick up acid wastes and $1.25/gallon for cyanide wastes. For the owners, this was the cheapest way to go.

In California, at one place I worked, an oil company picked up our acid wastes for nothing. They somehow used it to flush oil wells. I also heard about others doing that when I was in Texas.

When I treated my own wastes, I did it about the same way as Harold. Your method, 4metals, sounds better.

As far as PGC is concerned, for safety reasons, I also prefer a porous cup or, on a larger scale, a membrane tank. Other methods can easily produce fulminating gold.
 
Would garden variety lime work as well as magnesium hydroxide to drop the iron?

It is recommended in a document I had read on Steve's site a while back. The last time I went looking for it I may have missed it or it had been removed. I think that's where I read it?

Something from the Australian plating industry?
 
Regular garden variety lime is calcium oxide but it wouldn't surprise me if a little magnesium oxide was in there as well because they are both mined products and can be co-mingled. In any event it will raise the pH as required and if there is enough magnesium oxide in there the precipitate may be coarser than the iron dropped with caustic. I'd say try it, you may need a little heavier agitation than a aquarium bubbler will provide to mix it in. You could always use milk of magnesia, that is nothing more than a slurry of magnesium oxide in water. Magnesium oxide is very difficult to get in less than ton quantities so by all means try it and let us know how it settles.
 
About the copper sludge, better to leave it acidic? Or treat it with lye, soda ash, or lime before drying?

Anyway I checked the bag of lime I have, the analysis is 46.5% calcium oxide, and 32% magnesium oxide.
 
Very good to know that the mag ox content is that high in run of the mill garden lime. It may be a great alternative because it is readily available and inexpensive. With any luck it will filter out well.

The copper sludge is just rinsed with water and dried, when you have a few pounds it can be refined for values.
 
This I find surprising, if there is an easy way, or you know an outfit that does this, please do tell. Harold had mentioned he had 2 drums of copper he couldn't give away when he sold his refinery.

I have 2 gallons of acid neutralized with lime. I don't have a PH meter so after it quit fizzing I added about 2 cups more lime. I'll let you know how it turns out.

A small amount of PMs were dropped from this batch of waste. I'll test and process it as soon as I get a chance.
 
All of what I have read on this forum indicates recovering this copper is not practical because of flux and fuel costs.

However I had a thought. Would a collector such as scrap zinc improve the cost of this recovery? As scrap brass? Reducing the melt temp and perhaps the flux requirements?

I don't have a furnace or foundry to test this but thought I'd put it out there anyway. Any thoughts anyone?
 
I've posted this method as a means of waste treatment for the spent acids. The precipitate from the first drop, when you added the copper bar, theoretically will have any missed PM's in it, it is collected, and when you have enough, roasted and refined. The copper is dropped when you add the iron to the solution that has been raised to a pH of 2.5. The copper as a solid is much less of a waste hazard than it was digested in acid and that is why it is dropped out of solution. Melting the copper into a bar may or may not be cost effective, I don't know. That is not the primary reason for dropping it out.

When I said the copper sludge, it would have been more clear if I'd said the sludge dropped from adding the copper bar. The copper is still in the acid when this sludge drops. Sorry for the confusion.
 
Fair enough. I had been going directly to iron for dropping my wastes. The traces of PMs I missed were simply lost. Thanks for the copper first trick. Though the amount of PMs is small I had thought I was careful with these 2 gallons of waste while some was recovered so that's pretty cool :) .

Still if you think of a way to profit from the copper leftovers dropped with iron I'd be glad to hear it.
 
My competitor at the time I was refining was Cascade Refining. If memory serves, the scrap yard I did business with told me that they had been buying his copper that he had been recovering electrolytically. I had intended to do so myself, but I was so busy I didn't have time to mess with the process. I would suggest that you explore the possibility----for in the long run, you'll have copper to sell, and copper to use for silver recovery. I think it's worth the effort, assuming you have some idle time. I would certainly explore the possibility myself if I was still refining today.

Harold
 
I'm sure the copper could be melted because the copper produced in mining operations is often reduced from solutions with iron, then cast into anodes and electrolytically refined. A strong reducing flux should do the trick, I've used cryolite for really difficult melts, tough on crucibles but tougher on oxides.
 
Q2Know,

You mentioned you don't have a pH meter, well some of these reactions are pH dependent and a meter would help. Since we all have computers, there is a unit out there called a pH Turtle which plugs into a computer and is a fantastic pH meter. Costs about $110. Just Google pH Turtle and it will come up.
 
I melted enough of the material to learn that it isn't profitable on a small scale. The time and expense it takes, coupled with the damage done to the crucible, render it a losing proposition.

Kennecott Copper is one of the largest copper producers in the world. They have operated an open pit mine in what was once Bingham Canyon for over 100 years. The operation is huge, so large that the mountain that once made Bingham a canyon is now gone, a huge hole in the ground. This operation was my neighbor. They run a precipitation plant and recover copper with scrap steel. I've actually stood inside one of their furnaces, a huge reverberatory unit that had been shut down to be relined. They can process the material economically because of the sheer volume and balance of materials that are charged to the furnaces. I have serious doubts if that could be accomplished in a home refinery without sustaining losses far greater than the value of the recovered copper.

When I closed the doors on my humble refinery, I ended up hauling two 55 gallon drums of copper, recovered with scrap steel, to the land fill. In spite of considerable effort, I couldn't find a buyer-----and was totally ignored by Kennecott when I offered to deliver it free of charge to their facility, where it could be put in the pipeline.

It is for the above reasons that I suggest the home refiner attempt recovery electrolytically, where the copper has a chance of being deposited in a relatively pure state, perhaps even nodular in form. That would be acceptable in recycle centers, unlike the sponge that is typically recovered on scrap steel.

Harold
 
I have a question about dropping copper with iron after filtering the silver cement. While experimenting with small batches, I used iron nails to drop the copper. They seemed to work ok. Now that I have processed a number of batches of silver using copper to cement the silver, I have a bucket of copper nitrate. I am using an old lawn mower blade to drop the copper, but it is not working very well. Is there a specific iron that is best to use? Maybe the lawn mower blade is a steel alloy that doesn't work as well.

Thanks for your advise.
Tom
 
Low carbon iron works best (think soft iron) as to avoid carbon residues and speed the process. Also stay away from any form of stainless.
 
4metals said:
Waste treatment for the small refiner.

.......clear liquid to discard.
4metals, you stated in the post to syphon the clear liquid to discard. My question, for discarding, would this clear liquid now be safe enough to just pour down the drain or by whatever means...street, storm drains, etc.

Rusty
 
I believe you still need to bring the PH level to 7 before you can put
your clear liquid with no heavy metals down the drain.
 
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