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topic 1558

HCl Acid Recovery / Regeneration

A discussion started in 1998 but continuing through 2018.


Q. I am working with a company that needs to recover the HCl they use in the process.

a) This is a process of electro-plating with zinc, for malleable iron parts (connectors of different sizes). They have a daily production of 40 tons of metal parts.
b) They use per month, 39.8 tons of new HCl.
c) They remove from this acid bath, 300 liters of HCl at day.
d) This daily purge, has a concentration of acid: 8-10% and a concentration of Fe: 2-8%
e) They want to use the acid in a closed loop.

That means that they need to reduce the month purchase of acid.

We think that the diffusion dialysis equipment, or the ion exchange membranes are the most appropriate technologies for this process.

I hope that all this information will be useful, and hope that you can send me an answer as soon as possible.


Daniela Ramos, Environmental Projects Coordinator,
Pollution Prevention Center, ITESM, Environmental Quality Center - Mexico


A. Call U.S. Filter Recovery Services. I saw a presentation over a year ago where they were going to put a plant on line for bulk reprocessing/recovery of HCl. They probably also have technology for reclamation of HCl on-site if the volume is big enough.

bill vins
Bill Vins
microwave & cable assemblies - Mesa (what a place-a), Arizona 


A. Dear Daniela,

You can contact HYDROMATIX. Their technology may help you out, as well as they are helping us.


Domingos J C Spinelli
S B Campo SP, Brazil


A. Hi, Regarding your recouping HCl, I'd like to think that you would get a PARTIAL ... possibly a large 'partial' reduction of the gas stream were you to intercept the fumes and with an inertial (dry scrubber)scrubber approach. This would only partially work as the emitted HCl fumes may be or could be partially gaseous BUT, most definitely, would contain low micron droplets of acid. This inertial approach is much improved/enhanced if one can keep the temperatures down and ergo get improved condensing. I ran across a HCl wire pickling plant where I also happened to design the fume hoods. NO, said that Company, we don't want or need any scrubber'. (This was back in the mid 70's in Ontario, Canada.) I thought that they WOULD have a problem with air pollution and on purpose allowed for an extra length of ducting before the fan ... They DID have a problem.There WAS carry-over.But fortunately as there was enough room/space before the fan, a simple inertial scrubber was installed very easily. This seemed to do the job & I never had a complaint from them. However,the old philosophy dealing with ccid fumes has always been USE A MASS TRANSFER SCRUBBER. My experience indicates that MOST of the fumes and gases in your industry, the Surface Finishing field, are neither GASEOUS NOR FUMES but consist of invisible droplets. Hence, if one can remove said droplets (an absolute breeze for Hard Chrome fumes) WITHOUT 'wetting down and scrubbing with water', then one achieves acid regain. That simple scrubber was a horizontal two stage CT-l20/2 made of PVC which will take out all droplets down to l2 microns. A more advanced unit (which I designed), the so-called LMITS inertial scrubber, will remove droplets down to 3 microns. I did have it once tested at around 85% efficiency in a 0.2 to 0.8 micron spectrum but that was for hot sulphuric emissions and they did wash down constantly with Na0H. (INCO # 2 Research, Port Colborne). . This may not be exactly what you have in mind. Nor would I l00% guarantee a LMITS because some of the HCl will disassociate and be gaseous. But at least I think you could have a very inexpensive partial solution to recouping most of the HCL. Food for thought! Regards,

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

March 25, 2012

A. Dear Ms. Ramos,
The idea of recovering acid has always been a concern of mine and wondered about distillation and eventually came across this link
which showed that the technology is applicable for spent acids. I also envisioned this method would make it a lot easier to collect and recycle iron which is more profitable than the recovered acid I guess.

Q. Dear all,
It would be very much appreciated if you can provide compelling reason/s why Kleingarn acid regeneration procedure should be preferred over the making of fresh acid using fresh water (or used rinse water) and pure acid.

Thank you and regards.

barlow campano
Barlow Campano
galvanizing chemist - Jeddah, KSA

To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)

Recycling pickling waste


Q. I am a research student. There are major pickling waste (acidic) generated to remove the surface contamination. I am trying to recycle & reuse it again. Metal loss is also identified in pickling waste. That are Zr, Cr, Ni, Fe, Sn etc. The pickling waste is acidic and highly corrosive. we use H2SO4, HNO3 and HF for their pickling process. Pickling process is done after scrubbing process. The process done as under:

1. After scrubbing, the zircalloy components a dipped in pickling bath solution to remove the surface contamination.

pickling bath solution
HF 3% in V/V (40% conc.)
HNO3 40% in V/V (60% conc.)
water 57%

2. the Spent pickling solution contains
HF 2.3% 
HNO3 19.5%
zirconium salts as ZrO2(9.3%)

3. After pickling , so lots of solid waste is generated & they are sent to solid waste dumping site. For that we have to pay also.


1. Can we recovered the zirconium from the pickling waste?

2. Can we recycle the spent acid & reuse it again?

3. Can we recover the zirconium from the solid waste?

Kindly give your nice & useful suggestion that will help me. Please Reply early as soon as possible.

Kolan Suman
- India


A. Dear Suman,

Recovery and treatment is possible depending on the quantity of pickling involved. Distillation of unused acid for reuse, membrane recovery etc are some of the possible solutions.

Chander Mohan
Industrial Chemicals Co. - Chandigarh, India


A. Many times the "Spent" pickle solution can be used at near by waste water treatment plants. The solution is used in a process to clean sewage water. The higher the iron content the better. Many companies will now pay you for the product.

Mike Sauls
- Ghent, Kentucky, USA


A. Presently I am searching on this topic I found several methods to recover the acid and salts:

-ion exchange

-diffusion dialysis

-electro dialysis

-microbial oxidation of salts fallowed by precipitation

combination of one of other etc......found

Thirumalesha Chittipotula
- Chennai, Tamilnadu, India

May 28, 2008

A. I undertook thesis regarding treatment of plating chromium waste using pickling waste. Wherein Pickling waste is used to treat Hexavalent chromium compound retained in (carcinogenic in nature) waste water. The sulphates of iron perform reduction reaction in acidic media (both sulphates and acid are present in Pickling waste). Both wastes neutralize each other symbiotically.

- New Delhi, Delhi

May 29, 2014

Q. How to maintain the pH level of acidic tanks in pickling process after it loses it effectiveness?

- vapi, gujarat, india

May 2014

A. Hi Nilesh. With full respect I wonder if your inquiry is worded precisely enough? ... I think you might be concerned with maintaining the pickling effectiveness rather than the pH.

Decades ago I heard the assertion that simply adding water to a partially spent pickling acid could improve its effectiveness. In the years since, I've learned that not only might that be true in certain circumstances, but that there is a whole science to the effectiveness of acid based on its dissolved iron, dissolved zinc, pH, acid content and water content. Barlow Campano has graciously provided this site with a technical article, "The Kleingarn Regenerated Spent Acid at Increasing Ferrous (Fe+2) and Ferric (Fe+3) Chloride Content" and a "HYDROCHLORIC ACID PICKLING CHART", that I think you will find helpful! A patient search of the site will reveal several discussions on the topic.


Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Re-using pickling waste or recovering iron from it

December 29, 2017

Q. Is there any procedure to recover iron from pickling acid?

Is there any use for pickling acid?

puducherry raj.R
Trader - Pondicherry, India

December 2017

A. Hi raj.R,
For the benefit of any readers who generate such waste, we must note that getting the maximum use from the acid via inhibitors, acid extenders, and techniques like the Kleingarn method are a better way to go than trying to recover the iron or re-use the acid. Obviously, you as a trader will be looking at what to do with the waste product rather than how to minimize it, and Ajay Jolly's posting might be of interest.

opinion!  Here in the USA no one dares attempt recycling or re-use of process chemicals anymore. Everything has unintended consequences, and our EPA in an attempt to shut down "midnight dumpers" ruled that the generator of a waste is responsible for it forever, so nobody risks trading it anymore. To my knowledge the whole "Industrial Waste Exchange" business completely collapsed, and treating and burying the waste in a secure landfill is the only non-reckless approach to disposal. If there is in fact an industrial waste exchange that can disabuse me of my ignorance I'd appreciate it.


pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey

January 3, 2018

A. Hi raj.R,

There are some uses for pickling acid, as here in Argentina some company is taking used pickling acid and using as an input in the ferric chloride production. This ferric chloride, here, is used mostly as a cationic aggregation agent or coagulant.

Some companies that have this type of waste products here use it by oxidizing (totally or partially) it to later co-precipitate other heavy metals in wastewater treatment. This is costly because of the quantity of sludge produced by the iron content in this liquid, and disposal is very expensive.

Hope this helps you in some way. Best regards!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

January 3, 2018

A. If the acid used is Sulfuric, then there is one more technology to recover the iron and reuse the acid, namely crystallization of ferrous sulfate at low temperature.

Lyle Kirman
Consultant - Cleveland Heights, Ohio

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