# Any other alternatives to cutting NOx fumes other than H202?



## CR2008 (Nov 11, 2010)

Hello all, I read something in a few patents some time ago about fume scrubbers using H2O2 combined with NaOH to better absorbe NO2 gas, also something about using H202 directly to the source of reactions (nitric acid bath).

goldsilverpro also mentioned a patent that used a very low concentration of Urea and Sulfamic acid that also reduced NOx fumes and also speed up reactions, has anyone tried this method yet? This was mentioned over 2 years ago, and I figured that by now someone would have tried it.

If it worked or not, I would still be using the fume hood (molded PP) and chemical resistant lab blower (made from PVC and PP plastics) I got the other day, but at lest with less NOx gases, my scrubbing solution or dry scrubber media would last longer and having a faster reaction time sounds good.




Here is a link to the patent if you wish to read it:
http://www.freepatentsonline.com/3367874.html
United States Patent 3367874 
Process and composition for acid dissolution of metals 

Link to old thread were this was mentioned:
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=55&t=764


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## Lino1406 (Nov 11, 2010)

Urea in the scrubber - best NO2 killer, turns it into N2.
If you use it in the working solution you'll get a mess


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## Lou (Nov 11, 2010)

Urea+sulfamic acid+nitric acid gives laughing gas, N2O in quantitative yield. I believe that was how it was made in the old days for giggle parties.

If anything, that would decrease the efficiency of a nitric acid leach.


Best way to get more bang for your buck on nitric--dilute it! That and throw a condenser on top of your flask (or a watch glass on your beaker, which you should have there anyway).


Lou


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## CR2008 (Nov 11, 2010)

Lou said:


> Urea+sulfamic acid+nitric acid gives laughing gas, N2O in quantitative yield. I believe that was how it was made in the old days for giggle parties.
> 
> If anything, that would decrease the efficiency of a nitric acid leach.
> 
> ...



Do you dilute the "rough nitric" acid (using Sulfuric acid with nitrate salt) with equal vol of water? I read this "rough nitric" was about 50% nitric acid. I have lab equipment for distillation, and would only distillate to 68% nitric acid for a final refining rather than initial refining.


I got a some lab glass I can use as a gas washer and have a compact reflux condensator, thinking of initially using distilled water in one (to make a dilute nitric acid, to make some of that NOx usefull at lest I figured) followed by regular scrubbing media under a fumehood. I wander how strong this diluted nitric acid will be? If this solution was used for a long time, probably it can be distilled.


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## entropy (Jan 13, 2011)

I've been looking for the same thing, but instead of looking for other ways to cut the NOx fumes I tried looking for ways to make H2O2. I ended up finding some hypothetical means of dealing with nitric fumes. I don't really know if all these qualify as alternate methods, since they all kind of revolve around the H2O2 reaction, but there's some different end products and price points.

Disclaimer: I have no idea what the hell I'm doing. I haven't done any _real_ chemistry since high school and now I've been reading about it for about a week. Do your own homework. All of this is hypothetical, I haven't tried any of it. Some of these reactions are akali base/acid neutralization reactions and are probably very exothermic so don't blow up.

Method 1: Hydrogen Peroxide

Let me say that I don't think you have to add the H2O2 to the reaction, although you can. If you use a retort or condensor and filter the NOx gasses through H2O2 it will convert it to fairly pure, renewed HNO3 dilluted by whatever water is in your H2O2 plus whatever water vapor is condensing off your reaction. 2 NO2 + H2O2 -> 2 HNO3. If you're boiling nitric off AR, or distilling nitric or making new nitric this is very handy as you can't chuck it in the reactor anyway. Also, by not applying heat to the H2O2 because it's not in the reactor, if you're using heated solution, it's probably more stable. (Downside, it won't turbocharge your solution.) I like this because besides supressing nasty NOx fumes, you get to recycle and reuse your nitric acid so I get to be incredibly cheap and stingy. The big downside is, H2O2 costs as much or even more than nitric does - and that's if you buy nitric, instead of making it for 1/5th of the price! Not seeming economical.

At any rate, I mention this because none of these, as I imagine then, are going to be 'in the reactor' methods but all solutions to filter the evaporated nitric or NOx through.

Method 2: Just plain water

4 NO2 + 2 H2O + O2 -> 4HNO3. (Alla Nurdrage's youtube vid on making nitric acid, method #1). No H2O2 but lots of H2O and some O's on the side, kinda like a 'poor man's hydro peroxide'. Filtering the gas through plain aerated water will reconvert some of the nox into fresh nitric, cuts down on the fumes, and it's cheap as you can get, basically free. Downside is, it's not very efficient. You probably won't get all the fumes out and some will still bubble through the water. And the resulting nitric acid will be very dillute. It will probably work a bit more efficiently if you oxygenate the water with a fishtank bubbler or something.

The 2 above are documented on youtube and on the forum. From here on out these are my own cockamamie newb ideas, so... 

Method 3: Wash your NOx fumes with soap!

Sodium perborate (online price check yields a 55lb bag for $72.60 and a 6lb bucket for $12.30) dissolved in water. It's chemically very similar to Borax. It's considered a bleaching agent because it produces H2O2 in water (so it's still a H202 reaction), with the remaining boron stuff I would guess probably acting like a soapy sudsing agent.

NaBO3 + H2O = H2O2 + NaBO2
2NO2 + H2O2 -> 2 HNO3 (+NaBO2 swimming around)

The problem here is, now your left with more nitric, but what the heck do you do with very dillute soapy nitric? I have no idea what the heck that sodium metaborate is going to do in the nitric, if it will react to produce more NOx, or if it will screw up any other reactions with the nitric. Maybe you can process it out first before using it, but I don't know how at the moment. So this one is kind of half baked. I suspect there's some cool things you can do with cheap and abundant boric acids and boric soaps if you know more about that stuff but I don't.

The last 2 methods do not recycle more nitric, but are neutralization reactions that produce water and salt. But it seems like a convienent salt.

Method 4: sodium peroxide (online price check: holy crap, forget it. Also DHS will probably arrest you when you try to import it from China). It makes peroxide and lye in water and has the same products as method #5. But while researching it, I did learn you can heat sodium metabisulfite to make your own lye, but I've no idea if that's cost effective and it does produce dangerous sulfur dioxide fumes.

Method 5: miracle stain remover / soda ash

Sodium percarbonate (online price check: 100lbs for $62.96, 10lbs for $17.08; caution: one supplier wants $120.90 for a 50lb bag and tacks on a $35 hazmat shipping charge plus regular shipping). Stuff is marketed as a cleaning agent, a flake form of hydrogen peroxide.

2 (Na2CO3-1.5H2O2) (aq) → 2 Na2CO3 + 3 H2O2 
2NO2 + H2O2 -> 2 HNO3
Na2CO3 + 2HNO3 -> 2NaNO3 + CO2 +H2O

The end products are water, carbon dioxide, and sodium nitrate!

NaNO3 + H2SO4 -> Na2SO4 + HNO3

Dehydrate it into a nice, pleasant, stable, solid, neutralized, non-fuming salt and stick it in a jar. Use it for whatever you use sodium nitrate for, including - if you want more nitric acid - adding it to sulfuric and distilling fresh concentrated nitric acid. 

Using sodium nitrate to make nitric produces sodium sulfate - AKA Glauber's Miracle Salt - a 17th century laxative, and/or sodium bisulfate, both of which are fairly benign as well. 

There are probably a zillion other ways you could process it with aqueous alkaline salts, but I'm really liking the sound of soda ash and I might want to try it, if I can deal with the heat it might produce (it is an acid/base reaction!) It seems like it nails 5 birds with 1 stone - it's cheap as all get out, it will process and eliminate NOx fumes, you can recycle your nitric acid, and you've got a better way to store it than bottling red fuming death in your freezer, and the salt byproducts all seem trashcan chuckable. 

AND you've also got pounds of soda ash to neutralize stuff with, if you don't mind peroxide getting in. Multitpurposing means less chemicals to store and run out of and restock and worry about overall.

AND you can also store and use the stable percarbonate to make hydrogen peroxide for other uses, if you don't mind getting sodium carbonate in your peroxide. 7 birds... OK.. maybe not a great oxidizer anymore due to the basic soda ash but possibly wash your clothes with it or something. 6.5 birds. Miracle stain remover indeed.


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## goldenchild (Jan 13, 2011)

entropy said:


> The big downside is, H2O2 costs as much or even more than nitric does...


Where do you get _your_ nitric?


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## Irons (Jan 13, 2011)

Air:

Use a reflux condenser and feed Air at a slow rate through your reaction vessel. NO will be converted to NO2 which will react with water in the reflux condenser and return as HNO3. If you want to be even more efficient, use Oxygen gas instead of air.


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## entropy (Jan 13, 2011)

goldenchild said:


> entropy said:
> 
> 
> > The big downside is, H2O2 costs as much or even more than nitric does...
> ...



From a retort full of hot sulfuric acid 8) 

30% sulfuric is like $3/gallon, sodium nitrate is like $4/lb, 30% hydrogen peroxide I'm finding $100+/gallon. And that's only 30%! If it costs me over $310/gallon to reclaim the nitric acid, screw it I'll just make more. Maybe I can capture and sell my NO2 fumes on ebay.

Maybe it _seems_ cheaper if you're buying 3% H2O2.


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## Barren Realms 007 (Jan 13, 2011)

entropy said:


> goldenchild said:
> 
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> > entropy said:
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$100 for hydrogen peroxide! :shock: Check pool supply store or laundry supply company that price is way to high.


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## entropy (Jan 13, 2011)

Good idea. For online price-checking purposes I was going with the chemical supply stuff rather than pool supply because I don't know if pool chemicals require FDA labeling since you can't eat them... How do you tell what else is in it? Like I said I haven't done any of this yet I'm just gaming it on paper.

I googled "pool supply h2o2"... Found somebody selling a gallon of unknown % + unknown additives for... $125 +S&H... lol. Although I also found somebody selling a gallon of stabilized 35% (ostensibly, the labeling is confusing) for just $45 including shipping. Still unknown on the additives.

At any rate, that really is much better pricing on peroxide costs for use as an oxidizer, but it's still doesn't seem very economical to use to recycle nitric, maybe a wash if you buy nitric and a rip-off if you make it. You can get nitric for around the same price, I'm seeing $20-40ish a gallon for 65-70% online. Or, a whole lot more... depending on where you can get it... kind of like the peroxide I guess. They still seem about equally expensive to me IF you actually buy nitric.

If you make your own nitric you can do much cheaper. And I think if you use percarbonate to recycle it you can do alot cheaper on the H2O2 too.

Open question of whether or not it's good or bad that percarbonate turns it into salt. If you want to reuse your nitric _right away_, it's maybe a PITA bad thing and you have to use more $4 sulfuric, and more time - but I still think you'll save money. If you want to reuse your nitric _eventually_, and/or just get the heck rid of it, I'm looking at the nitrate product as a feature and not a bug.

If you can find a way to get the borax out of the peroxide, the soap method will yield you the liquid acid stuff. Metaborate is not a super common reagent it seems, there's not a lot of information on processes to be had with google for my newb butt to pilfer. Knowing that it's basically soap it seems problematic to me to remove it from the water without killing off the unstable H2O2, and if I took a wild guess I'd guess the nitric will eat it and just make more NOx for a net total waste of time and soap. Or maybe find another peroxide producing salt... there's probably others. I stopped looking when I came by percarbonate because it appears to suit what I was looking for, but it seems a promising avenue.


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## goldenchild (Jan 13, 2011)

entropy said:


> goldenchild said:
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> > entropy said:
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I get 2 gallons of 27% H202 from the pool supply store for under $30. I also make my nitric (when needed).


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## Irons (Jan 13, 2011)

Usually, the pool supply stores have sales in the Spring to get rid of their old inventory. I bought Baquacil 27% H2O2 for $$11. US per gallon on sale.
If you keep it in a cool dark place, it will last at least a Year. I have some that is 2 years old and still usable.


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## gold4mike (Jan 13, 2011)

Sally Beauty Supply - 20%, 30% and 40% by the quart for $6 or $8. It's been a couple of months since I bought so not sure of the exact price. They're all over the US.


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## philddreamer (Jan 14, 2011)

I bought some months ago some 40/peroxide @ Sally's thinking it was 40%.
I was corrected by another fellow member, but I never search to find what %
it really was. The 20, 30, 40, 50 is volume, not %.

I just did an MSDS search on a brand my daughter uses,
SUPER STAR by Marianna, & I found that 10 volume is 3%; 20 vol. is 6% & so on, it increases by 3% ...

I had bought @ that time 40 vol. which in reality is 12% peroxide.
Check out the site: http://msds.beautyalliance.com/Marianna/

Phil


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## goldsilverpro (Jan 14, 2011)

I think 10 vol means that the oxygen contained in the 3% would occupy 10 times the volume of the liquid, if released. The O2 from 1 liter of 3% would occupy 10 liters of space. I assume this is at some definite temperature, pressure, etc.


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## gold4mike (Jan 14, 2011)

Thanks, phildreamer, for that tidbit. I mistakenly thought I was buying 30% and 40%. I guess I'd better start paying more attention to the labels!


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## philddreamer (Jan 14, 2011)

Your welcome brother, & I thank you for bringing that up again so I would end up doing the search I ment to do, but never did. 

Yeap, we should be paying closer attention to the MSDS of the chemicals we plan to handle. I, for one. 

GSP, thanks for shedding light on the "volume". It was my question.

Take care gentlemen!

Phil


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## kadriver (Jan 24, 2012)

Phil:

I tried to go to the site you posted and got an error message - no longer available.

I bought just under half a liter container of the #40 for $3.19 today at Sally Beauty Supply.

It contains phosphoric acid which kind of concerned me - impurity.

the seal on the lid is less than good - some of it leaked out and got on my finger causing a white stain (see photo).

It actually touched a place on my finger that was stained with silver nitrate also - the hydrogen peroxide removed the silver nitrate stain!

kadriver


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## element47 (Jan 24, 2012)

LOL. We can always count on kadriver for clear photos. 

By the way, don't think I'm anything but appreciate of your documentation efforts!


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