My thought was that the KFe complex would be solid, though I have not checked its water-solubility - and thus can be separated by filtration. If you are concerned about free KOH forming carbonates then most of the unbound material - which would be potassium citrate at this stage-could be removed by washing the solid fraction in distilled water and re-filtering. However, I do suspect that the presence of some small percentage of carbonates in the end product would not be particularly detrimental. Sometimes you have to improvise a bit when exploring the possibilities.
KFeO2 is a metastable solid compound that only exists under specific conditions. Similarly to KOH, it quickly absorbs moisture and CO2 from the environment but with the addition that it decomposes in the process.
I don't think it can be filtrated as wetting the compound with water at low temperature immediately decomposes it into a brown mixture of various iron oxides, hydroxides and KOH. Excerpt below from https://doi.org/10.1002/9783527610044.hetcat0163
On the very short term this brown mixture can be reverted to KFeO2 if water is allowed to evaporate again at elevated temperatures. Actually I have a video where this is in part shown; see the first 30 seconds here (I used a KOH aqueous solution rather than just water):
The carbonates formed with prolonged dry exposure at mild temperature to atmospheric gases tend to have a white (when dry) or initially emerald green look (possibly partially containing Fe in some form although I can't rule out other impurities in the material). They form quicker at lower temperatures; see for instance in the photo below on the cooler edges of the olive-green sample.
From the same source as above:
From what I have observed however, stable carbonate presence is tolerated, if more KFeO2 can be formed again and if the existing carbonates get dissolved onto a wider area. I have usually accomplished this by adding more KOH solution to the heated surface, temporarily wetting it.