Dealing with Waste

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Fragum

Member
Joined
Nov 23, 2007
Messages
22
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.
 
Idea :idea:

Could someone do a Tutorial on the different types of waste acids that maybe encountered and the different methods for their reclamation, naturalization, and disposal. Noxx or Steve can post and lock it in the Tutorials section.
 
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.
 
Yes nice post,especially for someone that just got here.You are gonna fit in nicely thats for sure.Can you give us just a little info on you,your hystory and experience?Also are you knowledgable of processing one specific type of material or all materials in general.
Johnny
 
I am a chemist and I've been around precious metals both analytically and for recovery since 1972. I built a small "refinery" for a manufacturer I was working for at my first job out of college, they were getting ripped off by their refiner and I proved to them how much I could save them by processing the higher yield materials in house. They allotted me a space roughly 15 by 20 with 2 hoods which entered the facility's scrubbed exhaust from the plating shop. I also had a drain for acid waste and one for cyanide. Both were treated before discharge. In that room I recovered the gold and made it into PGC (potassium gold cyanide) a salt used in gold electroplating. After my first year I had recovered over 400 ounces of gold from the higher yield materials, and shipped out the low grade materials, which I witnessed myself. The return we received from the low grade, equaled the previous history for returns when they shipped all of the material out and didn't send a rep. I left that company after 5 years and went to another large manufacturer who also had a plating facility, I basically did the same thing for them, only we sold the fine gold instead of making gold salts. After 3 years at the new place I heard that they fired the guy who replaced me at the first place because he wasn't getting the same results as me and they eventually caught him stealing. (Ironically they had hired him from a local refiner because of his work experience) They made me an offer to open my own refinery to process their materials, I approached my current boss at the time and he said if I took them up on their offer, he would send me all of their work as well.

So now I had my own refinery, a 950 square foot facility with 2 good customers to cover my overhead. The first few years were difficult because I was adding equipment to refine faster and smarter but when I settled down on a stream of work, I did very well. I ran that place for 10 years, had 6 employees and sold it for a tidy sum. They had a fire about 6 years later, they had expanded and never took the time to set up a proper chemical storage area, after the fire department left it became a superfund cleanup site.

I had moved on to consulting, basically setting up refineries either completely from scratch or adding process capabilities to suit the owners needs. I semi retired in 1990 just handling 1 client at a time and have done that since. I've handled alot of jewelry related materials, silver and PGM refining, setting up assay labs, electronic scrap processing and even had a placer operation going in Brazil for a few years, with its own refinery of course. Of late the biggest headache for refiners is the EPA and all of my clients are compliant and usually pass inspections.
 
4metals:

Thank you very much for your post on treating acid waste.

I have been looking for that information since I came to the forum. I cringe at the thought of dumping toxic and heavy metal laden waste down the drain and I knew that it could be dealt with responsibily. Just needed to know what to do in order to clean it up for safe disposal.

The best part of the whole process is that it doesn't cost an arm and an a leg to do it.

If we want to refine as a hobby, we need to accept responsibility for the wastes that we generate. Otherwise sooner or later its going to cost us, one way or another and I sure dont want a bill from the EPA for cleaning up my back yard.

Thanks so much and I hope others will add more to this thread.
 
Eeeek, that was 30 years ago, I preferred the porous cup method but I'll have to look that up in some old notebooks, I'm on the road for a few days so I'll look it up when I'm back at home base.

I'd appreciate your comments on neutralizing wastes as well, I'm sure you've been there done that as well and some of the members will benefit from the discussion.

I also wrote some large posts in the section on selling your metal to try and explain to some members how to witness a refining lot at a large refiner and come away with a fair deal. I'm sure you've done that as well and it is another topic which members seem to need more information about. I'm sure you, Lou, and Harold could shed some valuable insight about waste treatment and witnessing refining.

The posts about witnessing are under a thread called "I've been screwed by 2 different refineries" If you have time to comment maybe we all can learn from it.
 
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.

GSP

The first time I made PGC I used the gold fulminate method but when I realized just how much I'd have to make I switched over to the porous up. Fulminates are scary. I did find a very practical use for the gold fulminate at the first place I worked, the boss liked to quietly walk up behind you when you were busy and since I usually had chemicals in my hands I didn't like that. To cure him of the habit I dropped small drops of gold fulminate on the concrete floor just inside the door and allowed it to dry. When he tried to sneak in it popped off like caps under his feet. That cured him, he never came into the room after that. :D
 
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.
 
4metals said:
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.
 

Latest posts

Back
Top