Lanthanum vs GFO specificity for phosphates

[sdreef]

Both GFO and lanthanum are used in the aquarium primarily to remove phosphates. I've been considering dosing lanthanum as opposed to using GFO particularly if it is more specific for binding phosphates. In addition to concerns regarding precipitates affecting livestocks, I wanted to understand the chemistry a little better and some of the other potential effects on the water.

I've seen other discussion on the ability of both lanthanum and GFO to affect alkalinity. GFO has been documented to have an effect on trace metal concentrations such as the article here.

Aquarium Chemistry: Effects of GFO (Granular Ferric Oxide) on ‘Trace’ Metals Concentrations in Artificial Seawater

Granular Ferric Oxide (GFO) is popular among reef hobbyists as a means to decrease phosphate levels and subsequently algal growth in their tanks. GFO, however, can also affect other ions and compound levels as well. In this article, Dana investigates the effect that GFO has on our tanks outside...

reefs.com

I have not found much information regarding lanthanum and trace elements and was hoping to learn if lanthanum is going to bind them as well or if it has such strong affinity for phosphates it is less likely to affect trace metal concentrations than GFO.

I have some questions regarding this. @Randy Holmes-Farley
1. Is lanthanum more specific for binding phosphates than GFO? Does lanthanum have a higher affinity for phosphates relative to GFO?
2. Lanthanum can bind to carbonate as well, but does lanthanum affect trace metal concentrations as well?

 

[Randy Holmes-Farley]

I've never seen a study of these trace element issues.

With trace elements, the question is not so much whether lanthanum binds any trace elements (not that likely for most elements), but whether they bind to the lanthanum phosphate and lanthanum carbonate particles that form, which is likely.

Comparing affinity of a particle (GFO) to a soluble ion is very tricky and I'm not sure how one would compare them. Both bind phosphate well.