Reverse Osmosis Filter and Fluoride

Yes, according to :

http://www.livestrong.com/article/527125-does-reverse-osmosis-remove-fluoride/

and here :

http://www.historyofwaterfilters.com/ro-distillation.html

It helps to begin by understanding how reverse osmosis works. The reverse osmosis process starts with water being forced through a filter or membrane in a reversal of the natural process of osmosis.

Fluoride molecules are larger than water molecules, so when the water passes through the membrane, the fluoride molecules get left behind.

'....Fluoride molecules are larger than water molecules....'

Fluoride is an ion, not a molecule. A Fluoride ion has a radius of roughly 120 picometers.

A water molecule has a radius of roughly 280 picometers.

Slip of the tongue, good catch

OK, here is a redeemer question:

Given the common explanation of reverse osmosis, how is it that Na⁺, Cl^-, and Fl^-, each with an ionic radius significantly less than the radius of H₂O, can be effectively removed by reverse osmosis?

Well, pressure is increased on the salt side, forcing the feed stream through the membrane. The salt ions stay with some of the water, which increases it's concentration, and becomes a waste stream. The pure water has a low concentration and is able to pass through to become the product? The technical details of what's happening - I'm not sure, but I believe that current generation systems use a thin film composite membrane.

'... The salt ions stay with some of the water...' This is essentially what makes the separation possible (whether you realized you had given the explanation or not).

Water, being polar, clumps around the ions, and the clumps are too large to pass through the membrane....