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Using waste pickle liquor (ferrous chloride & hydrochloric acid) to break an oil-in-water emulsion

Q. One of my customers in the steel industry is worried about using (recycling) its waste pickle liquor (a mix of ferrous chloride and hydrochloric acid) to break an emulsion of oil in water, generated in its steel galvanizing process, because a US Patent, No 6,409,927 B1, says that this is a patented process.

Do you have any reference about companies, which are using this patent? Or this patent really doesn't apply for breaking O/W emulsions with waste pickle liquor because it's a general known application (like making scrambled eggs).

I will really appreciate if you can help me to clarify my customer's doubt?


Margarito Villanueva
Water treatment - Monterrey, Nuevo León, Mexico

A. Just dial on your browser and find for yourself if it applies to your case. If you prefer, you can even talk to the owners of same.

Guillermo Marrufo
Monterrey, NL, Mexico

Ed. update: The patent office has changed its URLs, and unfortunately that address doesn't work anymore. But the link is

A. You need to talk to a patent attorney if it's questionable, Maragarito. I wouldn't advise anyone to ignore a patent, but both from the standpoint of prior art, and obviousness, it strikes me as fairly lame :-)

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Ed. update 2014: seems to say that it expired in 2014 for failure to pay maintenance fees, but the internet is no substitute for a patent lawyer :-)

A. Margarito,
This patent works and is already being used in many plants. The ratio of spent pickle liquor to wastewater is minimal.

Juan Gonzalez
- Austin, Texas
May 22, 2023

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