We have used crosslinked polymer gels as extraction solvents for aqueous solutions. The gels swell to many times their dry weight by absorbing water and low molecular weight solutes, but excluding proteins and other high molecular weight solutes. The swollen gel is removed by filtration. When it is slightly warmed, it collapses, releasing most of the absorbed material. This sudden change of swelling with temperature occurs because the gel is near a critical point. After the gel is separated from the desorbed water by filtration, it is cooled and then can be reused.