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Thread: How does PhosFree and other phosphate removers work?

  1. Back To Top    #1

    Join Date
    May 2011

    How does PhosFree and other phosphate removers work?

    Interested in the actual chemistry, especially because at least PhosFree claims it "is formulated from lanthanum compounds."

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    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Central Minnesota

    Re: How does PhosFree and other phosphate removers work?

    Lanthanum chloride reacts with the free, dissolved phosphate compounds to form a salt (precipitate) of Lanthanum and phosphate (lanthanum phosphate) which is not soluble in water. The chlorine ion from the Lanthanum chloride likely ends up bound to free sodium ions to form sodium chloride, table salt, which would dissolve in water. Lanthanum sulfate is also in these phosphate removers and reacts in a similar way with phosphate.

    Lathanum itself is classified as a rare earth element. It's not actually that rare in deposits, it's just fairly difficult to mine and extract, hence why phosphate removers with lanthanum compounds are relatively expensive and largely unnecessary if proper chlorine levels are maintained.

    chem geek may have more enlightened details on this but that's the Reader's Digest, probably somewhat correct explanation.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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  3. Back To Top    #3

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: How does PhosFree and other phosphate removers work?

    That's a good explanation and the only thing to add is that when you add a phosphate remover to the water it will generally cloud it temporarily until the precipitate is caught in the filter. The fact that it clouds does not necessarily mean you have phosphates in the water. Lanthanum also precipitates with carbonate and mostly what you see is lanthanum carbonate that gets caught in the filter. If there are phosphates, then they are less soluble than carbonate so with lanthanum carbonate in the filter the carbonate gets exchanges with phosphate if there is any left in the pool. So this means that you don't want to backwash your filter too soon after a treatment. Probably waiting one week is plenty (it might only take a day or two, but I don't know for sure).

    Some products such as PhosFREE also contain clarifiers in them to help remove the cloudiness more quickly. Other products, such as Orenda PR10,000 don't have clarifiers so the pool may remain cloudy for a while (days) if you don't use a clarifier. You can read about my experience with this in the thread Orenda Technologies PR-1000 and CV-700 Products.
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  4. Back To Top    #4

    Join Date
    Apr 2009
    Burlington, ON, Canada

    Re: How does PhosFree and other phosphate removers work?

    I used PhosFree several years ago (before I stopped worry about phosphates and just enjoyed my pool - I had no problems at the time, but believed the pool store that the phosphates were too high). I poured it into my skimmer very, very slowly and there was no clouding of my water at all. If you pour it in too fast, it will cloud your water.
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