Switchable Water: Design of Polymeric Molecules that can “Switch” the Properties of Water to Enable Green Process Engineering and Green Chemistry

Project Background

Water is undoubtedly the most commonly used solvent (i.e. a medium in which the reactions are conducted) in industry. Unfortunately, the processes used to remove various compounds from water, such as distillation, are often expensive in terms of energy, materials, and time.

The Jessop group has found that an additive can be designed to dissolve in water and allow fully reversible switchable changes in the ability of the water/additive mixture to dissolve different types of chemicals, i.e. the properties of the water can actually be “switched” so that chemical compounds that were originally dissolved will become insoluble, that is “un-dissolved”, and therefore easy to separate from the water. Some chemicals called amines have been identified that function in the following way; when a water and amine additive mixture is treated with carbon dioxide (CO2), the amine becomes a salt. Organic compounds dissolved in the water separate out due to the “salting out” effect.  The process can be reversed by removal of the CO2, for example by flushing the solution with air.  This method could allow for drastic reductions in energy and materials required to separate organic compounds from water and encourage water recycling. Such an additive could greatly increase the versatility and attractiveness of water as an industrial solvent, and consequently lead to reduced use of organic solvents including several listed in Table A of the Toxic Reductions Act (e.g. toluene, xylene, methanol).

While the preliminary results have been very promising, in order to have the greatest efficiency, the amine additive would be much more effective if it was incorporated into a polymer, since many amine groups could be incorporated into a single polymer molecule. The Cunningham and Jessop research groups will work together to develop such polymeric additives and evaluate their effectiveness.