Waste Treatment, copper cementation.

[Alondro]

Same here. But I am wondering if aluminium does not do the trick. Precipitating all metals. I will see how the ppt will appear, and how the reduction will go - if there wouldn't be much nitrate deep reduction to ammonia. Somewhere I read that even HN3 could be produced in the process, what scares me quite a bit.

I wondered that adding NaCl to the juice in just about right ammount can ppt bulk of Pb as PbCl2. Or even better add H2SO4. Cementation with Fe would then give much cleaner copper. On the other hand, another filtration needed.

My waste is very diluted and contain nearly no Cu, lots of Cd and some SnPb traces. No benefit from recovery, and no possibility to scrubb Cd fumes at the moment. For this canister I will probably go with straight hydroxide, and we will see how things end up. I have regulated filtering unit which can be turned on for days... So if some gooey s..t form, I am prepared

Aluminum won't work with nitrates. It forms a layer of impermeable iron nitride on the surface.

Besides, Al is much more expensive than iron.

I also learned that the decomposition of both forms of iron nitrate (iron +2 and +3 oxidation states) takes place at a much lower temperature than copper nitrate, BELOW the boiling point of water. In fact, in hot aqueous solution over 80C, both iron nitrate forms decompose into iron hydroxide and nitric acid vapor.

So, the BEST processing idea is displacing the copper with iron, then pouring the iron nitrate in a flask connected to bubbler set up and heating it to about 90C, with the vapor bubbling into 3% hydrogen peroxide, to ensure that all the nitrogen oxides released are converted back to nitric acid. What will remain in the flask will be aqueous iron hydroxide goop.

 

[4metals]

So, the BEST processing idea is displacing the copper with iron, then pouring the iron nitrate in a flask connected to bubbler set up and heating it to about 90C, with the vapor bubbling into 3% hydrogen peroxide, to ensure that all the nitrogen oxides released are converted back to nitric acid. What will remain in the flask will be aqueous iron hydroxide goop.

The battery idea works for someone running silver cells on sterling silver because the electrolyte is mostly copper nitrate (if the Palladium is removed with Dimethylglyoxime ). That insures the insolubles from the battery are mostly copper.

The setup to distill the nitric for re-use benefits from the lower temperature but only marginally. If one has a proper distillation setup the extra few degrees isn't much different. However free dilute nitric can be concentrated in the same distillation apparatus. I think for some the removal of the copper as a metal is the big plus, and a classic treatment with caustic followed by filter pressing would be easier.

The chemist in me loves the chemical apparatus, but the practical refiner in me often chooses other routes. None are wrong, just another means to an end.

 

[Alondro]

The battery idea works for someone running silver cells on sterling silver because the electrolyte is mostly copper nitrate (if the Palladium is removed with Dimethylglyoxime ). That insures the insolubles from the battery are mostly copper.

The setup to distill the nitric for re-use benefits from the lower temperature but only marginally. If one has a proper distillation setup the extra few degrees isn't much different. However free dilute nitric can be concentrated in the same distillation apparatus. I think for some the removal of the copper as a metal is the big plus, and a classic treatment with caustic followed by filter pressing would be easier.

The chemist in me loves the chemical apparatus, but the practical refiner in me often chooses other routes. None are wrong, just another means to an end.

Since I deal with small volumes, the little setup I mention is ideal. I'll only be dealing with a maximum of a few gallons of waste solution at time, even when I ramp up processing. Still in the experimental phase right now, testing all the different parts for what's recoverable in them, creating standardized and efficient protocols for each main group of parts and pieces, and so forth.

Bigger refiners already would have the equipment to handle thermally decomposing copper nitrate directly.

 

[orvi]

Aluminum won't work with nitrates. It forms a layer of impermeable iron nitride on the surface.

Besides, Al is much more expensive than iron.

I also learned that the decomposition of both forms of iron nitrate (iron +2 and +3 oxidation states) takes place at a much lower temperature than copper nitrate, BELOW the boiling point of water. In fact, in hot aqueous solution over 80C, both iron nitrate forms decompose into iron hydroxide and nitric acid vapor.

So, the BEST processing idea is displacing the copper with iron, then pouring the iron nitrate in a flask connected to bubbler set up and heating it to about 90C, with the vapor bubbling into 3% hydrogen peroxide, to ensure that all the nitrogen oxides released are converted back to nitric acid. What will remain in the flask will be aqueous iron hydroxide goop.

I did cementation with Al also in nitrate enviroment, and it went quite well.. Altough, pH was above 4 to be precise. Loť of nitrate get reduced to ammonia (clearly smelled), but overall, it works in described conditions.
I liked aluminium for it´s quick action... Took 20L bucket, fill 10L of AR copper waste, grab old piece of aluminium roof sheet, rolled it into the spiral and toss it in it kickstarted the reaction instantly, and it was slowly chewing the plate downwards thus moderating the insanely exothermic reaction. Fully saturated spent AR usually reduced in volume by 1/3 at the end of the process just by evaporation/boiling caused by cementation heat.

But iron seems to be much better idea in terms of efficiency and reusability. After removing lead with H2SO4, cemented copper would be fairly clean - nice benefit.
Only thing to resolve is how to deal with cadmium... In a way we can recycle some nitric from the end juice. But... Cd(NO3)2 shouldn´t cause much problems as I think about it.

 

[Alondro]

I did cementation with Al also in nitrate enviroment, and it went quite well.. Altough, pH was above 4 to be precise. Loť of nitrate get reduced to ammonia (clearly smelled), but overall, it works in described conditions.
I liked aluminium for it´s quick action... Took 20L bucket, fill 10L of AR copper waste, grab old piece of aluminium roof sheet, rolled it into the spiral and toss it in it kickstarted the reaction instantly, and it was slowly chewing the plate downwards thus moderating the insanely exothermic reaction. Fully saturated spent AR usually reduced in volume by 1/3 at the end of the process just by evaporation/boiling caused by cementation heat.

But iron seems to be much better idea in terms of efficiency and reusability. After removing lead with H2SO4, cemented copper would be fairly clean - nice benefit.
Only thing to resolve is how to deal with cadmium... In a way we can recycle some nitric from the end juice. But... Cd(NO3)2 shouldn´t cause much problems as I think about it.

Oh, you're talking about aqua regia, not pure nitrate. The chloride ion in the AR will react strongly with aluminum.

 

[orvi]

Oh, you're talking about aqua regia, not pure nitrate. The chloride ion in the AR will react strongly with aluminum.

I also did pure nitrate, but in very weakly acidic pH, then practically basic pH. Altough not as waste, but scavenging last bits of PGMs from the solution after hydrolysis, which refused to cement on iron, zinc, or drop as ammonium platinate that was running nicely on Al. Altough much more ammonia was produced than PGMs cemented, it does the trick well for me

 

[Alondro]

I also did pure nitrate, but in very weakly acidic pH, then practically basic pH. Altough not as waste, but scavenging last bits of PGMs from the solution after hydrolysis, which refused to cement on iron, zinc, or drop as ammonium platinate that was running nicely on Al. Altough much more ammonia was produced than PGMs cemented, it does the trick well for me

Hmm, strange. The few tests I did with Al in pure nitric solution didn't react in the least. I let the Al rod sit in there for days and it did nothing at all.

 

[orvi]

Hmm, strange. The few tests I did with Al in pure nitric solution didn't react in the least. I let the Al rod sit in there for days and it did nothing at all.

Maybe your mixture had passivating properties. Hard to say. But I can say not all kinds of aluminium reacted the same. Sheet metal worked the best, but some aluminium spare parts which I had in the lab (broken) didn´t reacted that well... Just on few spots, and grinding with angle grinder to show fresh surface doesn´t help much

 

[Alondro]

Maybe your mixture had passivating properties. Hard to say. But I can say not all kinds of aluminium reacted the same. Sheet metal worked the best, but some aluminium spare parts which I had in the lab (broken) didn´t reacted that well... Just on few spots, and grinding with angle grinder to show fresh surface doesn´t help much

It might be Al-Mg alloys that react. The Mg would dissolve rapidly, constantly exposing fresh Al sponge with immense surface area that wouldn't be protected by nitride formaiton.

Alternatively, I was reading up on this and found that very dilute nitric acid will indeed react with aluminum. Concentrated will form the nitride layer and stop the reaction. So that's likely why the solution I tested didn't react, it was still too concentrated.