Selective passive adsorption of nitrate with surfactant treated porous electrode and electrostatic regeneration

Nitrate is an important pollutant in drinking water worldwide, and a number of methods exist for the removal of nitrate from water including ion exchange and reverse osmosis. However, these approaches suffer from a variety of disadvantages including the need for a regenerating brine supply and disposal of used brine for ion exchange and low water recovery ratio for reverse osmosis. We are researching and developing a form of capacitive deionization (CDI) for energy efficient desalination and selective removal of ionic toxins from water. In CDI an electrode is used to electrostatically trap ions in a pair of porous electrodes. Here, we demonstrate the use of high surface area activated carbon electrodes functionalized with ion exchange moieties for adsorption of nitrate from aqueous solution. Unlike a traditional ion exchanger, the functionalized surfaces can be repeatedly regenerated by the application of an electrostatic potential which displaces the bound NO3- while leaving an excess of electronic charge on the electrode. Trimethylammonium has an intrinsic selectivity, we are using this moiety to selectively remove nitrate over chloride. We performed adsorption/desorption cycles under several desorption voltages and ratios of concentrations.