Light Driven Desalination Membranes

Industrial development combined with the population growth has culminated in a rise in the demand for fresh water. Non-uniform distribution of  naturally occurring fresh water supplies may be unable to meet these rising demands. Seawater and brackish water is a readily available source of water. However, the commonly used methods for sea water purification such as reverse osmosis are highly energy intensive and require high density energy sources. We propose a membrane that can selectively pump salt (NaCl) against its concentration gradient thus desalinating saline water. The membrane would be constructed from native proteins found in Halobacterium species which thrive in high salt concentrations. These include sodium proton antiporter, halorhodopsin (pumps chloride ions)  and bacteriorhodopsin (pumps hydrogen ions). The transport of ions by these proteins would be initiated by the presence of light and hence the desalination would be a light driven process that could be used in conjunction with the existing desalination techniques to reduce consumption of energy. Currently, efforts are being made to characterize the fundamental rate of transport of chloride ions embedded in lipid membranes by the protein, halorhodopsin (responsible for pumping chloride). Eventually, we plan on making two-dimensional crystals with all three native proteins first in lipid and then in a more stable block copolymer membrane for the construction of a desalination membrane.