I worked in a company that makes pumps with magnetic bearings for high purity applications, i.e. semiconductor manufacturing. The impeller is a magnet completely coated in a really inert material, e.g. PTFE, so no metallic (bearings, shafts) parts touch the liquids. Efficiency is pretty low with these types of bearings, we got like 60-80%. Not sure if this is ideal for a satellite.