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Thread: Phosphonic acid, phosphate remover and stains..

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    Phosphonic acid, phosphate remover and stains..

    If there were metal stains in pool water and they were removed with an ascorbic acid treatment and then a chelating product containing phosphonic acid was used to bond to the metals, and then a phosphate remover was used to remove phosphates (and presumably, the phosphonic acid???), would the metals then be released back into the water where they could stain again or would they be removed with the phosphates?
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    JasonLion's Avatar
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    Re: Phosphonic acid, phosphate remover and stains..

    That would not remove any metals. Phosphate remover doesn't remove phosphonic acid.
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    Re: Phosphonic acid, phosphate remover and stains..

    But the phosphonic acid break eventually breaks down into phosphates, no?

    phosphonic-acid-does-it-raise-phosphate-level-t26346.html

    Actually, that brings another question to mind. If phosphonic acid breaks down into phosphates, what happens to the metal that might be bound to the phosphonic acid when it turns into phosphate.
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    Re: Phosphonic acid, phosphate remover and stains..

    If the phosphonic acid is 1-Hydroxy-Ethylidene-1,1-Diphosphonic Acid (HEDP), then it is fairly resistant to breakdown from chlorine, but it will slowly break down over time. When this happens, it no longer binds as effectively to metal so more HEDP is added. The released phosphate would get precipitated by excess of phosphate remover (lanthanum ions), if present.

    If you compare this with non-phosphate metal sequestrants such as EDTA, they break down from chlorine much faster so release metal ions back into the water more quickly and therefore require replenishment more frequently. In fact, they break down quickly enough to be noticed as increased chlorine demand.
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