How do you separate microcrystalline cellulose from amino acids in a powder mixture?
I would try to use a 5-10 cm layer of fine SiO2 particles above a slow filter in a Buchner funnel. I'd be surprised if it didn't do the trick.
Consider that the cellulose particles you see after filtration could come from the paper filter as well (I sometimes see such tiny tiny particles floating around after filtration), in which case it may help to submerge the filter in a beaker of hot water before use, and in the worst case, carry out the SiO2 filtration AFTER the filter paper (in a column with a fritted disk for instance, above larger sized SiO2 not to waste the fritted glass with tiny particles).