Explain about Iron solution to lower Phosphate

[aquadise]

Quote from DSR website: https://dsrproducts.co.uk/content/19-phosphate

Anyone please explain to me the part: "The Iron solution contains Iron (II/III) Hydroxide"

Thank you.

Phosphate can be lowered by several commercial adds which contains Aluminum or Iron Oxide (GFO). Both are substrate which must be placed in a bed filter. (with the water streaming up).

In this tube water pas through the media exchanging one PO43- with three OH1- ions.

We use Iron Citrate to control phosphate because it work instantly in the water column. No need to pass through the reactor (tube) to exchange PO4 anymore.

The Iron solution contains Iron (II/III) Hydroxide:

The Fe(OH)3 will exchange his OH1- ion with PO43- , 3x OH1- released 1x PO43- ion is being absorbed.

Fe(OH)3 + PO43- => FePO4 + 3OH1-

FePO4 is precipitated and will be skimmed off, or filtered out by the power filters. It can be recognized by de rust (orange) color in the filter wool and in the skimmer.

Sometimes the Precipitation can be recognized by a haze, which stay for about 2-4 hours.

 

[Randy Holmes-Farley]

That’s a confusing or incorrect write up.

The action of GFO is what is being referred to as iron II/III hydroxide. I cover that chemistry in detail here:

Iron Oxide Hydroxide (GFO) Phosphate Binders by Randy Holmes-Farley - Reefkeeping.com

The liquid iron citrate solution he uses does not contain hydroxide. I’m not certain if he uses ferric or ferrous citrate, but those reactions are:

Iron citrate + phosphate —> iron phosphate + citrate

The iron phosphate is insoluble and precipitates out