I wondered about that, but the only statements about purification say that the contaminants are left behind when the water evaporates (as in any other distillat

I wondered about that, but the only statements about purification say that the contaminants are left behind when the water evaporates (as in any other distillation system.) They have developed a clever mechanism for giving the aerogels an efficient structure for capillary transport, and the nanotubes make an efficient evaporator, but the article does not give any reason why the water needs to be raised before being evaporated (trees do it because they are in a competition for light, and maybe to get away from big herbivores.)