A Novel Electrochemically Regenerable Ion-Exchange System for Nitrate Removal

A novel electrochemically activated and deactivated anion-exchange system is proposed for nitrate removal from groundwater and wastewater, as well as other applications. It will combine the best features of liquid-liquid extraction and anion-exchange using resins, while avoiding many problems inherent in these systems, and providing additional benefits. It will employ liquid-liquid extraction using a non-volatile room temperature ionic liquid (RTIL) as the extractant diluent instead of a volatile organic compound (VOC) solvent, eliminating the primary objections to liquid-liquid processes while retaining their fast kinetics. Ion-exchange resins circumvent the use of VOC solvents, but elution with a large volume of "strip solution" is typically necessary to recover the target ion and regenerate the extractant for reuse, resulting in a large secondary waste stream containing a low concentration of the target ion. Redox-active extractants have made recovery in a small volume possible, but require chemical oxidants and reductants. This system employs only electricity. A redoxactive extractant is immobilized in an RTIL and oxidized electrochemically. It is then contacted with the waste stream and the ion-exchange takes place. The phrases are separated, the extractant is electrochemically reduced, and the target ion is released and recovered in a small volume for recycle or disposal.