# Waste acid disposal



## denim (Mar 14, 2013)

I have a few questions regarding waste acid disposal. I have been following the suggestions found here on the forum. Here are my questions- 

1.) After raising the ph to about 2.5 using soda ash I then add steel to drop out copper and other metals. I leave the steel (rebar) in the Acid for about 4-5 days then decant off the liquid, then run the resulting sludge through a filter. I rinse this a few times and dry it out and store it in a container. Is this dried material safe to toss in the trash or should it be taken to the local hazardous waste treatment facility? If I take it to the hazardous waste facility what should I label it as, being it might have some other metals in it other than just copper?

2.) Now I have an acid solution that is saturated with iron. I use sodium hydroxide to drop the iron. I then filter this so that I end up with a black sludge, which eventually turns brown. I read another post that said if you rinse this well you can dry it out and dispose of it in the landfill/trash. This would be ok if it did not take so long to filter. If I take this stuff to the local hazardous waste treatment facility what would I label the bucket- ie: iron hydroxide? iron oxide? iron II oxide? I want to order some magnesium hydroxide for this as I understand the resultant sludge from using it is much easier to filter. If I use magnesium hydroxide for this what would I label the bucket then?

3.) Since I am not interested in processing the copper, or any other pm's for that matter, in step one above can I cut to the chase and just drop all metals at one time, after raising the ph to about 2.5, using sodium hydroxide? If so what would the resultant sludge be called? In other words what would I label the bucket containing it as?

I always test my acids with stannous before dumping them into the waste bucket and they always come out negative for AU. Thus I am not concerned with losing any values by going directly to dropping copper and other metals with steel right off the bat. 

Thanks in advance for any advice,

Dennis


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## philddreamer (Mar 14, 2013)

Hi Dennis!
There're several things you could do to improve the safe handling and disposal of your waste, but it depends how serious are you about recovering and refining.


> 1.) After raising the ph to about 2.5 using soda ash I then add steel to drop out copper and other metals. I leave the steel (rebar) in the Acid for about 4-5 days then decant off the liquid, then run the resulting sludge through a filter. I rinse this a few times and dry it out and store it in a container. Is this dried material safe to toss in the trash or should it be taken to the local hazardous waste treatment facility? If I take it to the hazardous waste facility what should I label it as, being it might have some other metals in it other than just copper?


In order for me to speed this step of the process, I don't use a solid piece of steel, but steel filings instead. (my friend has a steel shop and I collect the steel saw's filing).
I also bought a belt heater, because heating the solution speeds the process even faster. After allowing the cemented copper to settle over night, I decant the solution running thru a big filter and I collect the copper for cementing silver and/or cementing PM's from my stock pot. 
To the iron nitrate or chloride, I add Lye until the metals drop; let settle over night and filter the next day; the rust is now ready to be disposed in the trash and the water to clean the drain. If you leave the copper in the solution you're taking to the waste facility, I would make it as Cu-Cl or nitrate... (copper is more detrimental to the enviorment that iron.)


> 2.) Now I have an acid solution that is saturated with iron. I use sodium hydroxide to drop the iron. I then filter this so that I end up with a black sludge, which eventually turns brown. I read another post that said if you rinse this well you can dry it out and dispose of it in the landfill/trash. This would be ok if it did not take so long to filter. If I take this stuff to the local hazardous waste treatment facility what would I label the bucket- ie: iron hydroxide? iron oxide? iron II oxide? I want to order some magnesium hydroxide for this as I understand the resultant sludge from using it is much easier to filter. If I use magnesium hydroxide for this what would I label the bucket then?


You can dispose of the iron in the trash, (but not the copper, that's why you should separate it first); use the proper size filters in order to run thru the filters more solution.


> 3.) Since I am not interested in processing the copper, or any other pm's for that matter, in step one above can I cut to the chase and just drop all metals at one time, after raising the ph to about 2.5, using sodium hydroxide? If so what would the resultant sludge be called? In other words what would I label the bucket containing it as?


How much gold are recovering the first time around that you're willing to throw away PM's left in the resulting solutions...? :shock: 
I would call the resulting sludge a big mess! I don't think that's a good idea; I can't be of much help on this area since I don't drop all kinds of metals in one batch; ...what would you do with that mess!?

Testing with stannous is not the final say; there're other means of testing like placing some clean copper and watch for cementing, if there're any PM's left in the solution.
You could be throwing away hundreds of dollars...
Just my dos centavos!
Take care!
Phil


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## kkmonte (Mar 14, 2013)

Why can't you dispose of the copper in the trash? I know dissolved copper is very bad for the environment, but once you drop the copper with iron, can't you dry and dispose of the copper powder in the trash?


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## philddreamer (Mar 14, 2013)

Maybe I could; but I have better uses for it, like cementing my silver and other precious metals from my left over solutions! 8) 
Phil

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=36&t=1094&hilit=disposing+copper+waste


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## butcher (Mar 14, 2013)

Solutions containing the metals are toxic, these toxic metal solutions can be acidic or basic, caustic or alkali, they will leach through soil and rock and can end up in underground water supply, or if flushed can end up in someone’s drinking water down river, these can contaminate our water with some very dangerous metals, to prevent poisoning ourselves or others, we can treat our waste solutions, which could contaminate drinking water for decades, if left untreated. 

These metals came from the earth as rocks or ore, much of these ores were formed from acids or bases, or were also formed from high temperature chemical reactions, or some even formed from water leaching through the ground, most of these metals in the earth for the most part have formed stable ores and do not pollute our water sources, but once these metals are extracted and changed chemically into concentrated or different solutions or forms they need to be treated before returning them back to the earth, the goal is to convert them into forms that do not leach easily back into our water systems, converting them and or containing them in a way that they do not get back into our drinking water.

There have been several methods to try to do this, concrete bunkers, lime burial, container burial, and other methods have been used, trouble is many of these over time can still pollute our water if the containers leak or are overcome by the toxic substance.

One of the better ways to treat metal solutions, is to cement out the more dangerous metal, (with a more reactive metal), with a metal less dangerous metal (a more reactive metal), the cemented metal in an elemental state being less dangerous state and which is less likely to leach into our ground water can be dried and reused, or disposed of, one of the metals of choice to cement out the more dangerous metals is Iron, this forms an iron solution that still contains many other dangerous more reactive metals (above Iron in the reactivity series), to treat this solution the pH is raised, to precipitate Iron and many of the other metals as a hazardous waste sludge, I normally raise the pH to around neutral let the mud settle and decant the solution, then treat this solution again to about pH 9.5 to 10, this is where many of the metals are least soluble in solution, here I again let the sludge settle and decant solution, then I will lower pH back down some, which again will precipitate some metal powders, and I end up with a clear salt water solution, the clear solution of salt water can be concentrated to remove a lot of the salts, or disposed of in a sewer treatment system, now this leaves us with the toxic metal sludge a hazardous waste, if we dry this waste we end up with many different types of dried metal hydroxides, they can be mixed with lime, they are not very water soluble, or at least more stable and less likely to leach into our ground water, and can be disposed of in a land fill, many land fills nowadays use containment and use water test wells to keep the pollutants out of the ground water, some country's or places may not use this so check with where you are disposing of these wastes to see if they can accept them, these dried metal hydroxides even though less water soluble are better sent to a Hazmat waste disposal station, here once a year we have amnesty day where we can dispose of our material from household waste, so I treat mine and save them up for amnesty day (you can label them as dried metal hydroxide waste). Actually a better way to make these metal hydroxide's even less water soluble is to heat them and to form oxides, but different metals form oxides at different temperatures, the oxides are much less water soluble and thus more safer, but the best temperatures to do this is around 1,200 degrees C. this slag would be better for disposal but can also cost quite a bit in fuel to produce, here where I live I always burn a lot of slash form cleaning up my woods, so roasting the hydroxides to convert most of my waste to oxides (as much as possible) does not cost me much in fuel, heating the hydroxides in large flat pans over a bed of coals from a slash burn pile (here you can label them as dried metal oxides).

Study dealing with waste in the safety section, I also read other articles on this subject studying as much as I can about it, as it is one of the more important topics we need to learn.

edited wording for clarity.


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## kkmonte (Mar 14, 2013)

Good idea to throw the metal powders in a pan over a bed of hot coals if you are burning some brush to clean up your yard.


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## denim (Mar 15, 2013)

Thanks guys for the advice. 

Phil- I'll try a piece of copper to drop pm's before dropping copper etc with iron on my next bucket and get back to you with the results. That will be interesting.

Butcher- quote- (you can label them as dried metal hydroxide waste). That was what I was looking for. I guess if had really strained my brain I could have come up with that myself. 

Regards,

Dennis


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## glorycloud (Mar 15, 2013)

For folks who are just processing fingers in AP, will the copper have less 
or no "other metals" in the sludge after cementing the rinse water
with steel? Just curious. I have been keeping the dried copper
from these efforts and I was wondering if there was a use for them.

If someone wanted to melt those specific powders in a old crucible
would you get a copper button or just a mess? 8)


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## butcher (Mar 15, 2013)

Copper oxidizes easily especially when heated up to melting temperature it can take oxygen from your torch, or furnace burner or the surrounding atmosphere, so if you just tried to melt bare copper you would burn up a lot of the copper as it formed oxides, to keep from oxidizing the copper in the melt, we can use a reducing flux, a flux with a carbon ingredient charcoal, sawdust wood, flour, sugar and so on, to keep the copper from oxidizing and convert copper oxide back to copper, the carbon in the flux is a reducer, it takes oxygen from the melt to form CO or CO2 gas, if using a torch a reducing flame would work better, in a furnace we also want to limit oxygen as much as possible.

Copper powder in air can form green copper oxides copper carbonate, so washing acids well drying and storing in an air tight jar or plastic bag can help, or these powders can also just be kept wet under a layer of water in a jar.

There is always a chance a little gold or values got past you when you process so the copper solution may contain traces of values, but if you process like I do, you would have already get those traces when you used the copper buss bar to cement and let everything settle well before you transferred the copper solution to another bucket to cement out the copper with iron.


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## Anonymous (Apr 11, 2013)

butcher said:


> Copper oxidizes easily especially when heated up to melting temperature it can take oxygen from your torch, or furnace burner or the surrounding atmosphere, so if you just tried to melt bare copper you would burn up a lot of the copper as it formed oxides, to keep from oxidizing the copper in the melt, we can use a reducing flux, a flux with a carbon ingredient charcoal, sawdust wood, flour, sugar and so on, to keep the copper from oxidizing and convert copper oxide back to copper, the carbon in the flux is a reducer, it takes oxygen from the melt to form CO or CO2 gas, if using a torch a reducing flame would work better, in a furnace we also want to limit oxygen as much as possible.
> 
> Copper powder in air can form green copper oxides copper carbonate, so washing acids well drying and storing in an air tight jar or plastic bag can help, or these powders can also just be kept wet under a layer of water in a jar.
> 
> There is always a chance a little gold or values got past you when you process so the copper solution may contain traces of values, but if you process like I do, you would have already get those traces when you used the copper buss bar to cement and let everything settle well before you transferred the copper solution to another bucket to cement out the copper with iron.


Right now I'm at the stage of needing to process my waste solution used to refine silver. My 5 gallon bucket is about 3 inches from the top, starting from Dec 2012 until now. Since I've never disposed of wastes before, I'm now ready to do it because I must do it at this point. 

*Butcher*, your last paragraph really made me get a better understanding of dealing with my wastes I now have. I have a few questions and comments, and any help will be much appreciated.

*1*. I have poured all of my waste solution (Nitric Acid, Distilled Water for recovering & refining silver) in a 5 gallon bucket. As my solution got at least halfway filled, I started adding clean soup cans and other clean food cans to the waste. As of now, the waste bucket is to the point where I must dispose of it properly.

*Q1*. Do I decant the solution first or do I remove any pieces of metal that hasn't dissolved, then decant? Also, Once I remove the solid pieces, should I spray them down into the solution before disposing of them after they dry out?

*2*. I purchased a plastic strainer from the dollar store (pot size) but I'm not sure what size filters I must use. 

*Q2*. Wouldn't I use the very large coffee filters to filter the solution, or could I use a piece of fabric, like an old bed sheet folded a few times or something else?

*3*. The statement about dropping copper into the waste solution is what turned on a light in my head because I know for a fact that I poured some silver powder in the waste solution that I had plans on recovering later on, like right now.

*Q3*. At this stage of how much waste I have and some copper that is too small or too dissolved to use to drop silver from a clean refining, should I drop some copper in the waste solution or should I wait until I decant/filter the solution, then add the copper to drop the silver.

Many of the cans I put in there have either been fully or mostly dissolved, and the few pieces that are still partially solid, they have rust all over them. I did notice that when I added steel to the solution, within a couple of days the solution would appear to clearing up, looking in from the top of the bucket.

Although I have a few more 5 gallon buckets, I don't want to have two of them around and making my cleanup any bigger than it has to be.

*Butcher*, I love your idea about the copper. From this point on, if I'm thinking correctly as to your post, once I pour my solution into the waste bucket, I should add copper to the solution first, to drop the silver that may be still in there, and then after filtering that, drop steel into that solution and let it drop the copper?

Thanks for all the help and knowledge this forum has provided everyone.

Kevin


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## lazersteve (Apr 11, 2013)

For copper nitrate leftovers from silver reactions, you may be better served converting it back into nitric acid:

Reusing Copper Nitrate

and

Recycling Copper Nitrate

Steve


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## Anonymous (Apr 11, 2013)

lazersteve said:


> For copper nitrate leftovers from silver reactions, you may be better served converting it back into nitric acid:
> 
> Reusing Copper Nitrate
> 
> ...


Thanks for the post Steve. At this point, I can revive the Nitric Acid from the waste solution? Sorry for not remembering some things here as most of my notes were lost on my other hard drive.

If I can do that, I can save on buying more Nitric Acid for now. 

I'll be looking at those threads to get a better understanding of what I need to do. 

Thanks again for the info.

Kevin

*[UPDATE]*

I remember those threads, and right now I'm not even setup to recycle the Nitric yet. I have to learn more and get more equipment and other needed tools/accessories to do this.


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## lazersteve (Apr 11, 2013)

Once iron (steel) is added the solution is more complex, but it may still be able to be rejuvenated. I've never tried to convert a nitrate solution that has had iron added to it, but it should work the same, just that iron will be removed electrically first, then copper.

Give it a shot and let us know how it turns out.

Steve


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## Anonymous (Apr 11, 2013)

lazersteve said:


> Once iron (steel) is added the solution is more complex, but it may still be able to be rejuvenated. I've never tried to convert a nitrate solution that has had iron added to it, but it should work the same, just that iron will be removed electrically first, then copper.
> 
> Give it a shot and let us know how it turns out.
> 
> Steve


I'll study on this process, as it's a much needed thing for me to do at this point.

Kevin


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## butcher (Apr 12, 2013)

If I was going to reuse the nitrate I would rather do it from a copper nitrate solution.
but you are left here with an iron nitrate, well lets see if this will work:

But if all you did was put iron in the copper (or possible some silver nitrate solution) you will have replace copper from solution leaving you with copper powder and Iron III nitrate solution (if any silver was in solution it will be mixed with these powders, if you reuse the copper you could get that little bit of silver back, but there may not be much there).

3CuNO3 + Fe --> Fe(NO3)3 + 3Cu
decanting solution from copper.

Iron oxidizes easily so if you had contact with air you may have some insoluble iron oxides mixed with the copper powder (rust) also.

Now if you only used this say to dissolve sterling silver, you most likely would not have much base metals higher than Iron in solution.

From this Iron III nitrate we could look at several options, like drying it to crystals and see if we could sell it to a jeweler to use to etch silver with (one of the uses for this salt), (HMMM maybe we could use it to etch silver plated spoons smearing the dampened crystals on the silver plate, soaking the spoons in a bucket of dampened crystal, and then polishing of the dissolved silver???).

Iron III nitrate mixed with metal hydroxides to a proper pH will precipitate iron hydroxide and leave use with the nitrate salt liquid for reuse:
Fe(NO3)3 + 3KOH --> Fe(OH)3 (s) + 3KNO3 (aq)
Save KNO3 potassium nitrate solution. or dry to crystals re-wet and re-crystalize for more pure salt peter.

Fe(NO3)3 +3NaOH --> Fe(OH)3 (s) + 3NaNO3 (aq)
Save NaNO3 sodium nitrate solution or make crystals and recrystalize.

we can then make HNO3 nitric acid with these nitrate salts salts or solution with an acid:

2NaNO3 + H2SO4 --> 2HNO3 (aq) + Na2SO4 (s) (@freezing).


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