Desalination by recently developed inorganic membranes using reverse osmosis and membrane distillation

Inorganic materials including natural clays, have been known for some time to interact with dissolved ions such that fresh water can be taken from seawater, and applied to desalination. Recently advanced synthetically derived inorganic membranes such as sol-gel silica and zeolites, utilize this separation mechanism with more control for optimizing the flow rates and salt rejection. Researchers for example have shown that by merging alumina and silica to form a bilayer membrane, cationic and anionic ion rejection properties combine leading to excellent ion rejection in both reverse osmosis (RO) and membrane distillation (MD). Our bilayer membranes with hydrostable functionalized silica displayed up to 99% sea salt rejection by MD. A unilayer zeolite membrane displayed sea salt rejection in MD as high as 99%, but was much lower in RO. Considering the novelty and versatility of MD, we make the case for new research here in achieving essential desalination energy and cost reductions, which may not be possible with current desalination technology. In recognizing the potential of inorganic membranes and MD, research is required to uncover long term stability and costs to properly compare with their established counterparts. Desalination is a serious water supply option for future generations and MD and inorganic membranes could offer major improvements to the cost and performance of future plants.