Sciencemadness Discussion Board

Cleaning / Recycling HNO3 Solution

VeritasC&E - 30-12-2020 at 13:58


I've read through a dozen of threads regarding HNO3 without really finding what I'm looking for. Most threads are about either concentrating HNO3 solutions or making such solutions from nitrate salts.

What I'm looking for is the most simple & practical procedure to start of with either technical grade HNO3 solution or a contaminated HNO3 solution* and ending up with a clean water & HNO3 solution (max 0.2ppm total trace metals). Minimizing losses and avoiding (if still practical) the use of other reagents are the other main focus points (use of a simple distillation apparatus, reasonable vacuum etc. is of course ok). The final concentration is not too important (though the higher is better to minimize storage volume, anything between 50% and azeotropic will do).

*Imagine soaking 5Kg of beach sand with everything that might be found in there (microplastics, organics, etc.) into 5L of technical grade nitric acid and recycling as much of it into a solution with virtually nothing else but water and HNO3.

Instinctively I thought I could clean HNO3 solution to extremely high purity (in the sense of obtaining a result containing virtually nothing else but HNO3 and H2O) as easily as can be done with an HCl solution, but after reading a bit I realizee it's not that simple (in part because HNO3 is an oxidant, and reacts with plastics, in part because it undergoes thermal and photocatalysed decomposition).

[Edited on 30-12-2020 by VeritasC&E]

Boffis - 30-12-2020 at 15:51

Vacuum distillation?

VeritasC&E - 30-12-2020 at 20:24

Quote: Originally posted by Boffis  
Vacuum distillation?


Thank you for your contribution.

Do you think -80% ATM would suffice? What is the rough proportion of thermal decomposition / recovery yield to expect? And how does one deal with NO2 and N2O4?


[Edited on 31-12-2020 by VeritasC&E]

Boffis - 31-12-2020 at 10:35

If by -80% of ATM you mean 200 mBar then yes. I have found that water venturi pressures (typically about 100mBar depending on the design and supply pressure of the pump) to be adiquate for distilling nitric acid. If you acid is contaminated I would distil it carefully at as low a temperature as possible first and fractionate it on a second distillation. This should allow you to get close to 68% azeotrope at 1 Bar. I am not sure what the effect of reducing the presssure has on the azeotropic composition though. Someone else on this farum may be able to offer you some guidance there. When I distil nitric acid it is usually from sulphuric acid to obtain >70% concentrations.

Fulmen - 31-12-2020 at 12:01

I don't see what's wrong with the azeotrope at atmospheric. It shouldn't decompose at that concentration and provides a well defined product.

vano - 31-12-2020 at 13:03

Approximately how much does nitric acid cost in your countries? I can not even imagine making nitric acid at home.

Bedlasky - 31-12-2020 at 17:57

Quote: Originally posted by vano.kavt  
Approximately how much does nitric acid cost in your countries? I can not even imagine making nitric acid at home.


1 liter of 65% stuff for 155 Kč (5,9 €). But you need bussines ID, without it you can't buy >10% HNO3 (EU have regulations for selling explosives precursors). How much it cost in your country?

[Edited on 1-1-2021 by Bedlasky]

vano - 1-1-2021 at 00:42

Its too much. At the moment I can buy 4.7 liters of 68% nitric acid for 5.9 euros, but I know the seller and I am sure he will give me 5 liters. Because he often rounds up the mass and volume of the product purchased and sometimes he gives me laboratory glasswarse and old chemicals for free. That is why I do not spend money on glassware. which is good because it is very necessary and at the same time expensive.

Regulations in Georgia work differently, for example, you can not buy reagents used in the manufacture of drugs, such as red phosphorus, potassium permanganate and acetic anhydride. In the list I think there are only this substances. I am not talking about Safrol, Pseudoephedrine and similar precursor s. But everything else you can buy for no reason. I have been buying for about 15 years.

[Edited on 1-1-2021 by vano.kavt]

Bedlasky - 1-1-2021 at 02:16

I must laugh when I read price for nitric acid in Georgia :D. It's nice that you have such an easy and cheap access to the chemicals and glassware. So my theory is right :D. The more east you are, the easiest access to the chemicals. Western Europe is quite strict, here in CZ you can buy some chemicals which you can't in western Europe. Poland is even more benevolent than Czech republic. But when I read what is possible get in Georgia and for what price, I think that your country is more benevolent than any Europian country.

EU is really chemophob (and not just that...) commonwealth. They just spits regulations without discussion with true experts. They should at least get a chance to amateur chemists to obtain some kind of permission. Just prove that you have knowledge and that you are capable of working with chemicals. In fact, you can get some permision, but nobody give you that just because chemistry is your hobby. This isn't reason for them. And this doesn't end just with chemicals. Everything must be "safe" and "correct". For example EU want ban for weapons. But in these times having a gun cause more problems than advatages, because if you shoot someone in self-defence, you are the one who goes to the jail and pay damages to the attacker. Or I read that German government wanted (or still want?) ban for breeding of venomous snakes just because ILEGALLY breeded cobra escaped to someone. This is nonsense, because regular breeders are really responsible people.

KMnO4 is used for making drugs? I never know that :D. Everytime I read, that KMnO4 is banned in some country, it makes me wonder. KMnO4 is used in medicine when you have some skin issues (for example fungal infection). In Czech republic you can buy it in every farmacy in small brown glass bottles. I don't know exact quantity, something between 20-50g. I can also buy it in bigger quantity online in one shop, which sells chemicals even to public.

VeritasC&E - 1-1-2021 at 02:40

Quote: Originally posted by Boffis  
If by -80% of ATM you mean 200 mBar then yes. I have found that water venturi pressures (typically about 100mBar depending on the design and supply pressure of the pump) to be adiquate for distilling nitric acid. If you acid is contaminated I would distil it carefully at as low a temperature as possible first and fractionate it on a second distillation. This should allow you to get close to 68% azeotrope at 1 Bar. I am not sure what the effect of reducing the presssure has on the azeotropic composition though. Someone else on this farum may be able to offer you some guidance there. When I distil nitric acid it is usually from sulphuric acid to obtain >70% concentrations.


I can simply distill it first at 200mBar, and then a second time with a column and I'll be all good? Is the column pass just for concentrating it?

Thank you and all others for your help.

vano - 1-1-2021 at 03:21

Bedlasky I agree with you in everything. Give good examples. There must be some permission for chemists in the European countries, at least some document must be given. Your vision is true in the East it is easier to find chemicals. My country is somewhere in the center. It would probably be much easier to find in the north of Europe, I mean Norway and Sweden, I remember there were quiet and peaceful countries, but I was little when I lived in such countries and then I did not even know what chemistry was. Now I do not know if anything has changed because of the migrants, but then the citizens did not make bombs from similar chemicals there, so there would be no restrictions.

It is true that in my country you can buy whatever you want, but no one will think of making bombs. It is a friendly country. Or I do not understand what the need to impose a restriction on say urotropine that did not receive from him HMTD and RDX. Anyone will go and buy a ammonia solution and formaldehyde. Then optionally nitric acid or hydrogen peroxide. That is, if a person wants and at the same time has knowledge, nothing can stop him, nor is it a problem to start synthesizing from more primitive chemicals. Why should cyanide be banned for example. When you go to the pharmacy, buy DMSO and selenium on eBay and get selenite from it. Dissolve it in solvent and even if it gets on the skin, it will be absorbed and the person will die. In short, these are not the regulations that Europe needs.

Permanganate sold here in pharmacies is simply expensive. I personally buy on Amazon.

Permanganate. Suddenly what I found https://pubmed.ncbi.nlm.nih.gov/12872685/

[Edited on 1-1-2021 by vano.kavt]

teodor - 1-1-2021 at 10:43

I think the point is that if the acid is contaminated you need vacuum for distillation. Contamination can cause decomposition on rising temperature during distillation. Quite pure nitric acid can be distilled into WFNA without vacuum.


[Edited on 1-1-2021 by teodor]

Fulmen - 1-1-2021 at 12:45

Again: Why vacuum? I assume the acid is below the azeotrope at this point. If so:
The azeotrope boils at 120°C, so well within the comfort zone off glass. And even though I can't find any references at the moment I'm pretty sure decomposition is negligible at 67%. Even if you exclusively need 100% NA I would start with the azeotrope.

VeritasC&E - 2-1-2021 at 07:03

Quote: Originally posted by teodor  
I think the point is that if the acid is contaminated you need vacuum for distillation. Contamination can cause decomposition on rising temperature during distillation. Quite pure nitric acid can be distilled into WFNA without vacuum.


[Edited on 1-1-2021 by teodor]


Makes sense. Maybe some metals act as catalysts.

Bedlasky - 2-1-2021 at 08:19

Quote: Originally posted by vano.kavt  
Bedlasky I agree with you in everything. Give good examples. There must be some permission for chemists in the European countries, at least some document must be given. Your vision is true in the East it is easier to find chemicals. My country is somewhere in the center. It would probably be much easier to find in the north of Europe, I mean Norway and Sweden, I remember there were quiet and peaceful countries, but I was little when I lived in such countries and then I did not even know what chemistry was. Now I do not know if anything has changed because of the migrants, but then the citizens did not make bombs from similar chemicals there, so there would be no restrictions.

It is true that in my country you can buy whatever you want, but no one will think of making bombs. It is a friendly country. Or I do not understand what the need to impose a restriction on say urotropine that did not receive from him HMTD and RDX. Anyone will go and buy a ammonia solution and formaldehyde. Then optionally nitric acid or hydrogen peroxide. That is, if a person wants and at the same time has knowledge, nothing can stop him, nor is it a problem to start synthesizing from more primitive chemicals. Why should cyanide be banned for example. When you go to the pharmacy, buy DMSO and selenium on eBay and get selenite from it. Dissolve it in solvent and even if it gets on the skin, it will be absorbed and the person will die. In short, these are not the regulations that Europe needs.

Permanganate sold here in pharmacies is simply expensive. I personally buy on Amazon.

Permanganate. Suddenly what I found https://pubmed.ncbi.nlm.nih.gov/12872685/

[Edited on 1-1-2021 by vano.kavt]


I think that north Europe is strict as western Europe. But I can't tell it for sure, I never been there. Norway isn't in EU, so who knows...

Most citizens of most countries doesn't think about making bombs :D.

Ban for explosive precusors in fact doesn't make sense - IS, Al-Kaida and similar organizations are from countries, where explosive precusors are cheap and available for everyone - why do they bother buy it in Europe? And even if they can't buy it in their countries, they buy stuff on black market where are certainly available some explosives. If some person want to kill someone, restrictions doesn't stop him. And as you said - if someone have knowledge, he can make explosives even from available sources.

I like to make fun of people, that cyanide can make every idiot from things which you can buy in every hobby market :D.