Methods to recover or separate cesium formate or rubidium formate or both from a mixed alkali metal formate blend are described. One method involves adding cesium sulfate or rubidium sulfate to the mixed alkali metal formate blend in order to preferentially precipitate potassium sulfate from the mixed alkali metal formate blend. Another method involves adding cesium carbonate or cesium bicarbonate or both to preferentially precipitate potassium carbonate/bicarbonate and/or other non-cesium or non-rubidium metals from the mixed alkali metal blend. Further optional steps are also described. Still one other method involves converting cesium sulfate to cesium hydroxide.