I'm not sure who to credit for the idea of magnetic nanobot desalinization, but I heard it recently proposed in a YouTube video by a guy named Lee Carroll. To me, the idea makes excellent sense in theory.
The concept is simple, make it cheap to desalinate saltwater in coastal cities by Channeling water from the ocean into a facility where tiny magnetized nanobots are continually injected into a loving stream of water.
The bots attach to salt particles in the water and get pulled out by a magnet as the water passes over the magnet on its way to purification.
If this technology were perfected it could solve a massive water shortage problem looming in The future by making it far cheaper to desalinate water. If this technology were combined with vertical growing technology and geo-thermal electric steam turbines, our cities could potientally feed themselves.