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topic 1558

HCl Acid Recovery / Regeneration

An ongoing discussion from 1998 through 2014 . . .


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
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

May 29, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

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'm not sure that your inquiry is worded precisely enough ... I think you are concerned with maintaining the pickling effectiveness rather than the pH.

Decades ago I heard the assertion that simply adding water to a partially spent 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 am sure you will find helpful -- and a patient search of the site will reveal a few discussions on the topic.


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

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