In the membrane-free variant of FO, hydrogels serve as simultaneous separation and draw agents, and the water that is taken up by the hydrogels has a lower salt concentration compared to the feed solution. After swelling of dry hydrogels in the salt solution, the supernatant phase with an enriched salt concentration is removed, and then the water with lower salt content compared to the initial solution can be recovered from the hydrogel by applying temperature. Such a simple desalination setup combined with no need for any sort of membrane reduces the process cost.