Low-cost, light-switched, forward-osmosis desalination system

T h e looming water crisis is the second largest issue facing humanity after energy. 663 million people, or 10% of the world population, lacks access to safe water. The United Nations estimates that the average person’s fresh water supply will be cut by a third over the next 20 years due to population g r o w t h . We propose a low‐cost solution to desalination based upon our proprietary light‐ sensitive polymers. The light sensitivity of the polymer is based upon the photoactivatable conversion of the hydrophobic spiropyran (SP) to the hydrophilic merocyanine. Light makes the polymer hydrophilic enabling it to draw water out of a seawater solution. When the light is then turned‐off the polymer reverts to the hydrophophic form precipitating and separating from the sea water which can be drawn off. The overall goals of our work plan are: (1) To demonstrate a desalination system that works better than strictly thermal or reverse osmosis systems; (2) To show that the system does not degrade and fragment over time; (3) To show that there is no residual polymer in the “purified” water.