The finishing.com Hotline -- Serious Education ... plus the most fun you can have in metal finishing
Disposal or Recycling of Hydrochloric Acid
An ongoing discussion from 1999 through 2015 . . .(1999)
Q. Is there a way to recycle muriatic acid (hydrochloric) used in the stripping of hexavalent chromium? I have heard many people tell of different ways to dispose of it. could you explain to me why it couldn't just be neutralized and put down the drain? NOT THAT I WOULD! Thank you, JeffJeff Mattocks
A. Basically, neutralizing it would correct the pH of the acid to an acceptable range, so that the acid would not cause undue corrosion to the sewer pipes, but would leave toxic hexavalent chromium in the waste if there was any to start with. What needs to be done is to reduce any hexavalent chromium to trivalent state, so that it is precipitable, then adjust the pH so it precipitates out, then filter it so the water can be discharged. The chromium-bearing solids would still need to be disposed of in a secure landfill.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
A. I would add a small amount of ferrous sulfate (about 5 lbs. per 1000 gallons) to reduce the chromium to the trivalent form, then adjust the pH to 8.5 - 9 with hydrated lime [linked by editor to product info at Amazon]. Lime should be added slowly with lots of stirring. Then add an anionic polymer to settle the solids. Make sure to have the water phase tested for total chromium before discharging it. It may be that you can extend the life of the stripping solution by running it through a column of weakly basic anion exchange resin, to remove the hexavalent chromium. This would have to be regenerated periodically with sodium chloride solution.
- The Bronx, New York
A. Another way that my former peers did not mention is to use columns to catch the Chromium (Cationic type I believe ) and to clean the Hydrochloric Acid. Then you can use the stripping solution with small HCl addition. Please consult with your local Environmental company or experts. Yours
YB Plating Engineering and Quality - Haifa Israel
Disposal of unused muriatic acid(2004)
Q. I do have a background in metal fabrication, but I have a small stock of muriatic acid from concrete work in trade. The local landfill resists receiving hazardous elements except on a certain date per year. I want to rid myself of this before locating back to Maine, where I last had use of it. My speculative need of it in the future is too lame to justify keeping the hazard in store. This is uncontaminated product. Is there a simple way to reduce it to a neutral condition? I appreciate your consideration and reply.James William Rayne
hobbyist - Newark, Delaware, USA
A. Hi James,
Seeing that no Guru had replied, how about having a gander in the archives at letter #12044. Surely there are some useful hints there ... even more if you are (heaven forbid) a dog lover.
- White Rock, British Columbia, Canada
It is our sad duty to advise that Freeman passed away April 21, 2012. R.I.P. old friend.
A. James, when I want to get rid of hydrochloric acid, I mix it with sodium hydroxide (NaOH) a.k.a caustic soda, until it is neutralized. HCl + NaOH gives NaCl and water.
Geez, I hope I don't have to emphasize that you should be careful, and to make sure that it's completely neutral (pH 7). I presume you know the strength of the muriatic acid, so it should be simple to calculate the amount of caustic soda you need. If you've any doubt, bring a pizza into your local high school chemistry class and let them calculate it for you.
Good luck! And remember, no one at finishing dot com advocates non-adherence to environmental laws!
A. Hi there,
As above but caustic soda is a little too violent in the reaction and somewhat expensive. Try some Calcium Hydroxide I think its also sold in the plastering trade as slaked lime, it's an alkaline. Dilute your acid and in a large 200 Liter plastic drum feed the calcium hydroxide (Slowly) Stir and check using litmus paper to gauge when when it's neutralized. This time you end up with Calcium Chloride. and water.Robert Fyfe
Audio Eng. - Wyoming, NSW, Australia
Thank you, Lee, yes, I'll hold to my best on the environment. Pizza's great, and I throw the dough, so maybe that's an angle.
Freeman, I'm replying with thanks prior to following your directions back into archives. The car looks great! Robert, you've given me the journeyman's answer, and you nailed my back-off (some experience) from caustic soda. I can get the stuff and already have a drum. If you know (or anybody) whether the resulting calcium chloride is ALSO a problem, please reply.
Thank you, all!James William Rayne
hobby/home improvements - Newark, Delaware, USA
A. I recall that the company I retired from a while back had about 1000 gallons of conc. sulfuric leak into a concrete containment pit. A local environmental services company came in and removed it for shipment to an "acid reclaimer" I believe somewhere there, in Delaware area, possibly at Dupont? We would use soda ash routinely to neutralize small drips of either sulfuric or nitric acid, by the way. Fumes were bad, but tolerable, when ventilation was adequate.W. Carl Erickson
- Vernon, New York
A. Dear James,
Calcium Chloride, like many Calcium Salts are insoluble in water. Our bones for example are mainly Calcium Phosphate. In the reaction converting your unwanted Hydrochloric Acid to Calcium Chloride, dilute the acid first otherwise it may splutter, remember that they use Hydrochloric, or when tainted with Iron, then sold as muriatic for cleaning cement off new brickwork, the product is Calcium Chloride and lesser amounts of other things (Silicates) and on construction sites doesn't this normally flow straight down the drain or into ground water. Check with your local E.P.A on acceptable disposal methods. Then again if you dried out the Calcium Chloride (Anhydrous) it makes a great desiccant (Water Absorber) but it is an Irritant...When it's this dry...gets up your nose, arh-choo.Robert Fyfe
Audio Eng. - Gosford, NSW, Australia
April 13, 2011
A. If this acid is new, uncontaminated then why destroy it? Maybe you can find someone who can use it? There is a group of Yahoo mailing lists called FreeCycle where people go to give things away they don't want but might still be useful. Or there's CraigsList. I've gotten rid of quite a few things that way. It's nice when somebody shows up, takes the unwanted item away in THEIR car at YOUR convenience and is even grateful to do so!
I came across your post looking for information about using Muriatic acid for PCB etching. I live too far away to consider taking it but for that use I think just about any Hackerspace would love to have it and be very appreciative. I checked the Hackerspace wiki though and the only one I found for Newark was a group of people interested in starting one. You could try contacting them but their website and twitter links don't actually work so I don't know if their email contact is any better or not. I don't know what other cities are near Newark to check them too.
- Toledo, Ohio, USA
September 6, 2012
A. Muriatic acid is used in many, many applications. If I were in your area, I would take the stuff from you for nothing ...then I would put it into my swimming pool as I do on an almost weekly basis for pH adjustment.
Find a neighbor or pool company and offer it to them. I use about three gallons/month. Ironically, I also purchase about 2,500 gallons a month at my job, which becomes contaminated and has to be disposed of properly.
Hope this answer came soon enough.
- Houston, Texas, USA
Need HCl recovery system for galvanizing tub(2005)
RFQ: Dear Sir/Madam:
We would be more than grateful to get your help in quoting a recycling system for our galvanization tub.
The quality of waste is:
Fe (+2) 14.11%
Fe (+3 ) 3.6%
PO4( -3) 0.3%
HCl (normalized) 4.3%
Quantity : 60 tons/month.
Please let us know as soon as possible what is the best method to recycle .
With kind regardsSHIR BLUMIN
pipe manufacturing and galvanization - Ramla, Israel
^- Sorry, this RFQ is outdated
View Current RFQs
July 12, 2012
Q. I am a student and I have a project on Disposal of Calcium Chloride.
student - Gujarat, India
September 10, 2012
A. Narendra, I have no idea if this is legal in your country. but you can mix it into concrete and make stepping stones out of it. Mixing it into epoxy is an alternative, but it costs a lot more.James Watts
- Navarre, Florida
Recycling/recovery of HClJanuary 17, 2015
Q. Hi Friend,
I'd like to know is there any process where HCl from pickling stream can be recycled? At present we are using 15-20% strength HCl; after a few cycles (within 2-3 days) the strength of acid will be 5-8%. We want to regenerate this acid. Please suggest.
electroplating - pune India
January 19, 2015
A. There are two commonly used technologies to purify and re-use HCl: Diffusion Dialysis and Acid Retardation. Neither actually regenerates the acid, the acid used in dissolving metal and lost due to dilution is not recovered, and must be replenished. There is good information on both these technologies that is readily available on the internet.Lyle Kirman
consultant - Cleveland, Ohio
Disclaimer: It is not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous; some names may be fictitious and some recommendations may be deliberately harmful.
If you need a product/service, please check these Directories: