Efficiently Recover Nitric Acid and Copper Metal From Copper Nitrate Wastes

I haven't stopped searching/pondering/scheming in these last few days, and I'm retired, so... I'll have to look into the electrode stripping voltametry, as that seems related to what I'm currently thinking about for replacing my now-dissassembled setup. It involves a steady drip of dissolved circuits onto a flask that has a bunch of hot copper slugs in it. The nitrates return and condense, dissolve more metal, and drip on the hot bed to return their acid until no more metal is dissolving. The sediment (which I'm pretty sure now is the tin I'm interested in) will be mostly trapped in the dissolving flask ( a strange 1L or so flask crossed with a Dean-Stark function I found on ebay). The residue and copper from the collection flask are melted into a bar - which is primarily copper - and electrorefined into purified copper. The residue gets melted with lead, and the process is repeated to elecrorefine lead, and on and on. I just watched your video on doing this with zinc, but of course, I would be melting the remnants into a bar with zinc, etc. It rather bothered me that I interpreted your earlier comment as "you need to know what is in solution to get it out"... your last comment made me realize that this isn't what you meant. My intention is to work out a procedure to take an unknown mixture of solids (circuit board that hasn't been manually separated or targeted extraction-ed, as is normal with "scrappers"), and get good-purity metals as an output. It's more of an 'applied' version of chemistry, rather than a disciplined one, but I'm really not trying to make money from dissolving circuits... Just trying to keep my brain going. :)

That's what analysis is, but you need something more accurate and precise than just dipping metals because the changes in solution composition and concentration can make some metals plate out before others. The famous "gold penny" chemistry trick is one of them. You can get zinc to plate ON to copper. the complete opposite of what you would expect just by the reactivity series. Anyway, the analytical technique best used for determining metals is something called "electrode stripping voltametry"

NurdRage

...and stepping down the reactivity series doesn't work for determining this? If not, then that is a very interesting topic.

unfortunately if you don't know what's in it and their concentrations, it's extremely hard to separate them just on solubility. You're going to have to send a sample to an analytical testing lab to determine the exact concentrations of the metals. And then we can figure out a procedure to separate. This is one of those things that you can't just blindly follow a procedure, you need to figure out what you have and craft a procedure for it.

NurdRage

To clarify, I'm still at the "displacing from Nitric with Copper" stage where I keep getting all this strange sediment. To clarify further, I am still very new to chemistry, and have yet to melt my first bead of purified metal. I'm currently in the process of taking apart my most recent circuit digester and making notes for the next iteration. I think a lot of my issues and confusion are coming from a design 'feature' ... or set of 'features' ...perhaps the types that a properly trained chemist would not choose to do, based simply on taught norms. I think that two interacting properties, one is an action like a soxhlet extractor, but without the submersion. The metal salts may not be combined until they get to the boiling flask, and so they can vary in composition, but are very dilute at this stage. When they get into the boiling flask the environment is both concentrated, and much more acidic due to the continual addition of NOx + (air) into the boiling flask, and reclamation of offgassed NOx in the condenser stages. In the boiling flask, the various salts can compete, likely leaving me with iron/aluminum and greater reactivities in solution, while I've been settling the flask and taking the liquid, and then moving that to a dedicated settling flask, and now I'm trying to displace things less reactive than copper from what really should be copper at most. So now my problem seems to break down to one of dilution, I think... But this puts me back at the previous question about juggling solubility of mixed nitrate salts at various temperatures. So far, I have the following conditions: -Dark green liquid with redish-tan sediment in the boiling flask, as a result of digesting electronics in hot/dilute Nitric Acid -Draining the green liquid and replacing with distilled water turns the sediment Fe2O3 red, and the liquid a pale yellow. -Continuing the NOx additions returns the sediment to the tan color, and the liquid becomes dark green again. -Putting the tan sediment in HCl reduces the volume of sediment, and turns it white, while the HCl turns yellow -Adding various substances to samples of this yellow liquid fails to produce an observable reaction, other than NaOH, which turns it brown, dries to rod and cube crystals, and breaks the beaker (fortunately, it was a 5mL beaker)

BTW, if you're getting stuff on the walls from your copper displacement reactions, just cover the container, don't make it air tight since gases might come out, but you can reduce a lot of the stuff on the walls by covering the container with a plastic lid. Anyway. 1. adding hydrogen peroxide will not cause any problems further down the line. But it would be advisible to let it cool before performing electrolysis. hot piranha and electricity may harm the platinum electrode. 2. if you're trying to displace other metals then temperature primarily affects speed. While it is possible to shift the equilibrium a bit using temperature, the effect is pretty small and wouldn't really be noticeable. anyway, the biggest problem i see with this process is lead. Lead nitrate is soluble but does not displace copper, so the lead remains in solution. But when you add sulfuric acid it becomes insoluble lead sulfate. This accumulates in solution since it doesn't plate out very much. Lead sulfate might be source of weird insoluble material you're seeing.

NurdRage

A question just occurred to me... At the point where the nitric is distilled off, and you're sitting there with sulfates in a sulfuric acid solution, and other potential contaminants, is there any benefit to adding hydrogen peroxide and resuming heat to expel carbon/organics that may be in there from the various epoxies, skin flakes, cat hairs that may have gone into solution during the dissolution of circuit boards? I'm concerned that it may do something outside of my understanding to the oxidation states of the metals, and void some part of the process... This is largely coming from a weird problem I'm having during the "remove noble metals with copper before bringing in the sulfuric acid" stage. I have a mixture of unknown nitrates in solution, and it's a dark forest green color. Putting in a copper bar and stirring 2l of this liquid for days, in a room that's roughly 12c (window always open near this stuff... even when giant fan is off) results in a light tan dusting on the walls after several days. A skin is forming on the surface. So, I stick it on the hotplate. Now, I'm getting much more of this tan stuff, and some of it is starting to look coppery in color, and there is more of it floating on the surface, while more and more of this precipitate is forming on the bottom (hotplate stir motor magnet is ineffective). So, to summarize what are two questions: - Will turning the post-nitric-removal sulfuric acid into hot piranha harm further steps in this video? - Can the temperature of a mixed-nitrate solution, in contact with copper metal, be used to remove more reactive metals due to temp/solubility shifts? I've made a spreadsheet and graph of the various metal nitrate solubilities vs temperature, but I have yet to identify what is more eager to leave solution as the temperature rises in presence of metallic copper. Keep in mind that pretty much any metal that make nitrates can be found in electronics, and some things (like perhaps tin?) can be dissolved in nitric, but then go on to be an oxide. By weight (but not in order), I suspect that most of the things that get dissolved by the nitric will be iron, aluminum, copper, tin, lead, molybdenum. To a lesser degree, there is silver, nickle, and palladium. My suspicion is that the low solubility of aluminum nitrate, and the "I just may be an oxide later" nature of iron and lead may constitute a lot of the sediment. I've been searching online, and through the small library on the behavior of Tin, with little luck, but tin is also a suspect.

I didnt finish the sentence in my earlier comment but white p can be obtained by the amateur. So i would argue that p2o5 is accessible

It appears that it is on ebay. Quite expensive at 142$/25g however it is seems to be there. Also there are other amateur methods of preparing it like burning white P in oxygen and afterwards heating up the residue in dry o2. That would take a specially built reactor as it cant be done in ordinary glass but it still is possible. And white P is obtained https://www.ebay.com/itm/Phosphorus-Pentoxide-99-9999-Metals-Basis-25g/251279590696?hash=item3a816e4528:g:5uQAAMXQrNtRyxql

yep! it would work very well... problem is i don't have it and i'm not sure the amateur can get it.

NurdRage

Would p2o5 work I know it can dehydrate H2SO4 into so3?

not sure, probably not. since i don't have a reliable dehydrating agent that can make it.

NurdRage

thanks! fixed!

NurdRage

All these nitric acid videos are great. Is nitric acid anhydride n2o5 going to be next?

The subtitles at 0:50 to 0:59 read "toxic nitrogen gas" instead of "toxic nitrogen dioxide gas".

Marc Ethier