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-----Muriatic Acid Disposal Problem
Q. I have roughly 30 gallons of diluted muriatic acid
⇦ on
eBay or
Amazon [affil link] . it was diluted 4:1. What would I do (fastest, safest, most environmentally friendly) to make it safe to dump on the ground or down the drain?
I have 3 mini pinschers...
- Columbus, Ohio
2007
A. Carefully neutralize with diluted caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] (sodium hydroxide) to a pH near 7. The final product is sodium chloride and water (very much like sea water). Then investigate if you can dump it in your area.
Guillermo MarrufoMonterrey, NL, Mexico
A. Adding a sodium hydroxide solution to an acid can generate significant heat. It would be safer and cheaper to use Sodium Bicarbonate ([in bulk on eBay or Amazon [affil link] ) in a vessel that is at least twice as large as the volume of liquid that you are neutralizing to allow for bubbling of the Carbon Dioxide gas that will be generated. Add the Sodium Bicarbonate slowly in a well ventilated or outside area. Continue to add the Sodium Bicarbonate slowly until the solution reaches a near neutral pH 6-7. You can then pour it down the drain assuming there is no other contaminants in the muriatic acid (hydrochloric acid). You will have metal contaminants in the muriatic acid if it ever came in contact with metal.
Mike Jackson- Woonsocket, Rhode Island
A. Hi.
Guillermo's and Mike's suggestion are both fine for 30 gallons of diluted HCl. But be prepared: the baking soda will bubble more that you think it will even after you've been warned to expect it to bubble a lot. It will take a pretty long time, maybe a couple of hours to do 30 gallons right. After you have double-checked the pH with pH paper
⇦ on
eBay
or
Amazon [affil link] , you can dump it down the drain (assuming that you are not part of a regulated industry).
Neither iron/steel nor aluminum are regulated in most jurisdictions, so if those were the only metals dissolved in it, you're probably still okay.
Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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Ed. note -- Readers: This is one of dozens of threads & technical articles about analysis, disposal, recycling, recovery, or extending the life of muriatic (hydrochloric) acid pickling solutions. Please search the site with an explicit search term to find info about your own specific situation.
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