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How to neutralize nitric acid


Q. I would like to neutralize 40-45 gallons of 40-50% nitric acid with approximately 10 gallons of a slurry of magnesium hydroxide, which will be pre-loaded inside of a steel 55-gallon waste drum.

Assuming proper mixing throughout the neutralization, would you expect to see any problems with the nitric acid attacking the steel drum?

I have considered using a HDPE tank to do this before I transfer it to a steel drum for disposal, but I'm pretty sure the heat of the reaction would melt the tank.

If steel and HDPE are not suitable, what is? Am I going to have to neutralize smaller amounts of acid at a time to avoid these problems?


Marty V [last name deleted for privacy by Editor]
- Urbana, Illinois, USA


A. Have you considered purifying, rather than dumping this acid? You are correct about the heat problems, it's usually best to dilute the acid before neutralizing. Then you could use a polyethylene tank.

Lyle Kirman
consultant - Cleveland, Ohio


A. I get bad vibes from your question. You can not abruptly add or ever rapidly add the nitric to the slurry or you will have it on the ceiling. It can be done if you have a good mixer and add the acid slowly with a tiny double diaphragm variable pump or a metering pump. Plan on an 8 hour day to be safe. Great care must be taken to not get into an acid condition. Polypropylene (non welded) will take a higher heat than Polyethylene and will stand nitric for a while. Thicker walls would be the best to stand the heat. Fiberglass supported would be great, but that is expensive.

P.S., do not be surprised if part of the sludge turns to a rock after it cools.

James Watts
- Navarre, Florida


A. Holy Moly! Don't get that Nitric Acid anywhere close to a steel container! If Nitric Acid comes in contact in steel it immediately releases a DEADLY orange gas. Even if you have the Mag Hydroxide already in the barrel, chances are the Nitric will splash on the sides of the container. If you want to neutralize the Nitric Acid you must do so in a container that will take the heat evolution that inevitably will take place. I would suggest Stainless Steel. I wouldn't use a plastic container unless the volume was several times larger than the volume of Nitric that you want to neutralize.

If that were the case, you could dilute the acid down to 5-10% and slowly add the Mag Hydroxide which would minimize the heat evolution. If you have dissolved metal in the Nitric you will also need to dispose of that too by legal means. This sounds more like a job for a professional waste handling company. If you make the wrong move with this stuff someone could get badly hurt.

Daryl Spindler
- Nashville, Tennessee

thumbs up signYour replies have confirmed my fears about the acid coming into contact with the steel.

It appears any means to accomplish this neutralization will be more expensive than I had hoped. Currently the system is designed with a HDPE tank and mixer and has been approved by a PE, but the price of disposing of the heavy metal contaminated acid dropped enough in the past month that I wanted to consider other options than an expensive mixer (have to run an electrical outlet too) and small additions of acid to avoid melting the HDPE tank. It appears that my time to recover the cost of the neutralization system will be stretched out a little further than I thought now that disposal prices have dropped.

Thanks for all of your help everyone.

Marty V [returning]
- Urbana, Illinois, USA


A. Have you considered pre-neutralising in a stainless steel tank, allowing to cool and then transferring to the steel vessel?

John Tuohy
- Ireland

January 15, 2008

A. If you want to be safe and cheap, you should dilute the acid with 20 lb bags of Ice, until, its about 10% nitric (and really cold) then you can add sodium carbonate slowly or quickly and it won't be a big deal. If it starts getting hot just add another bag of ice.

Matt J. H.
biochemist - Austin, Texas

May 21, 2010

Q. As per the earlier postings, I want to dispose 2.0 - 2.5% of Hydrochloric acid (HCl) & Nitric acid (HNO3).

My Plan is to mix

100 gms of Sodium hydroxide to 1 litre of HCl solution = Sodium chloride + water


100 gms of Potassium hydroxide to 1 liter of Nitric acid solution = Sodium nitrate + water.

Can anybody say the proportion is right?

Ravi G
Engineer, Employee - India

May 21, 2010

A. Hi, Ravi.

The neutralization formulas are:

NaOH + HCl => NaCl + HOH


KOH + HNO3 => KNO3 + HOH

So the ratios are all one molecule to one molecule. Next you calculate the molecular weight of each compound --

NaOH: 40
HCl: 36.5
KOH: 56.1
HNO3: 63.1

So you need 40 parts by weight of sodium hydroxide to neutralize 36.5 parts by weight of hydrochloric acid, and 56.1 parts of potassium hydroxide to neutralize 63.1 parts of nitric acid.

So you seem to be planning to add roughly 4 times as much hydroxide as you should. But here's the thing:

You should never "fly blind" unless you have to! You either confirm the ratios by doing a test-tube sized titration before trying to neutralize a larger batch, or the neutralization should be very gradual and under pH control or with an indicator of some type. You never neutralize waste based on formula. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

May 21, 2010

Q. Thank you so much Mr. Mooney for your fast response.

But we don't have any chemistry apparatus at our office.
If I mixed with a rough ratio, is there anything serious?

Ravi G [returning]
- Chennai, India

May 25, 2010

A. Hi, Ravi. If I was a home hobbyist dealing with a half liter of mild acid, I might be tempted to neutralize it based simply on calculations. But in that case, I would use nearly neutral chemicals like sodium bicarbonate (baking soda) rather than sodium hydroxide, so that "overshoot" could not cause any problem, as well as to minimize the exothermic reaction. You do realize that your proposed actions are dangerous?

But you used the word "office". Businesses are expected to exercise proper stewardship over the chemicals they use! A business which gains economic advantage over its competitors by doing operations without proper stewardship makes it economically unfeasible for their competitors to be able to do things right either, so it is something the whole world disdains :-)

Call a licensed hazardous waste hauler! Best of luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

April 14, 2015

Q. I want to know if it would be a good solution to neutralize spent Nitric Acid (typically 20-30% concentration) with Ammonia solution (10-30% solution -- again typically from a by-product source). By doing so, it would be possible to get Ammonium Nitrate solution, which could be converted into solid by evaporation of water.

I have a tried this in lab scale earlier and found the results to be encouraging. Of course the neutralisation reaction is exothermic in nature and part of this heat could be used to aid evaporation as well.

- Pune, India

April 2015

Ammonium Nitrate

Hi TVS. Is some countries only licensed facilities are allowed to do this; I don't know the rules in India. Can we assume that this will be done by a well qualified chemist? I don't think it's trivial; and I understand that once there is this much water in it, it's hard to get it out.


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Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

May 18, 2015

Q. Hi Ted, In India too, you need license to manufacture Ammonium Nitrate. Our company does have the license to do so.

In my last communication, I was specifically referring to neutralization reaction between Spent Nitric acid and Spent Ammonia.

Do you know of any specialist/company which has undertaken serial production of Ammonium Nitrate using spent raw material. We have a good resource for getting low cost spent raw material required for Ammonium Nitrate. I know there would be a cost to remove water as well at the end of the reaction.

So I would need the specialist/company to help me in the process as well.

- Pune, Maharashtra, India

May 2015

thumbs up signHi again TVS. Anyone is welcome to post any helpful technical, non-commercial, replies for you; plus, we'll see if any of our supporting advertisers contact you privately about this. Otherwise this forum can't put buyers and sellers together. For one thing we discard over 1000 spams and scams every day; we can't even look at even a fraction of them, and we can't encourage still more by giving people the impression that this forum offers free matchmaking services -- apologies but it doesn't. Camaraderie yes; technical help yes; potential commercial benefit, advertisers only -- sorry.


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Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

Reduce sodium hydroxide consumption for neutralisation of spent acid

November 27, 2016

Q. My company has a pickling plant where both carbon steel and stainless steel coils are pickled. There are various baths of HCl, HNO3, HF+HCl, HF+HNO3, rinse etc. These acids are drained to ETP after they reach a concentration level and iron content. These acids are neutralised using sodium hydroxide in a ETP tank with air blower for aeration (no stirrer present). Then it is passed passed on to clarifier after 6 hrs and attaining a pH of 7-8.Then it is passed to filter press. Now I want to reduce the consumption of sodium hydroxide in the neutralisation of acids. What are the parameters I should analyse and changes that could be implemented in the current system? Also please provide a list of books and research papers that I could refer to solve this problem.

Thanks and Regards,

Zain Ansari
- Mumbai,Maharashtra,India
  ^- Privately contact this inquirer -^

November 2016

A. Hi Zain. I appreciate your ambition, but to learn enough to be able to properly address this whole situation will be the work of years. You surely waste enough to economically justify retaining a consultant to work with you on recycling the waste, employing acid extender chemistry in the pickling baths so you remove the iron instead of dumping the bath, consider the use of alternative neutralizing agents, improve the mixing for neutralization, suggest additions for your library, etc.

Waste reduction is no longer something that your worry about after your production needs are met, but has become such an intrinsic part of every process step that it's rather hard to give "general" advice; someone has to look at exactly how you use each of those acids, instead of focusing on how to treat them after you have (perhaps needlessly) decided to dump them. Our readers can probably answer specific highly detailed questions for you though. Good luck.


pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

simultaneous November 28, 2016

A. pH 7-8 does not sound high enough to get effective removal of the metals. 9.5 to 10 would be better.

You might try lime instead of caustic soda. It's lots cheaper.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

November 28, 2016

A. The best way to reduce your neutralization costs is to purify rather than dump the contaminated acid. Both Acid Dialysis and Acid Retardation technology have been used for this successfully. Caustic consumption may be reduced by 80-90% and sometimes this is a larger cost savings than the redfuction in acid purchases.

Lyle Kirman

Lyle Kirman
Consultant - Cleveland Heights

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