Path toward sustainable desalination: Sodium precipitation and carbon capture

Current desalination technologies are not sustainably scalable due to high operational costs, high carbon emissions, and the environmental impact of brine. Almost all desalination plants built today use Reverse Osmosis technology, with research primarily focused on developing ultra-high permeability membranes that lower specific energy consumed. We believe sustainable desalination can be achieved by optimizing the overall Reverse Osmosis system. Our method takes advantage of the high-pressure brine, high levels of total dissolved solids, and the sheer amount of brine waste discarded. This is achieved by bubbling CO2 into ammoniated brine to precipitate sodium ions. The process was studied by modeling CO2 absorption, simulating real brine behavior, and optimizing for sodium removal. The results showed that ammonia requires 528 kg of CO2 per cubic meter of freshwater. In addition, the results revealed that CO2 absorption at 22.2 °C and 68.7 bar removed 72.5 % of the dissolved sodium. Ammonia unlocks the path toward sustainable desalination, as it can be absorbed and regenerated within the reverse osmosis system.