The presence of perchlorate in the environment is a growing public health and environmental concern. Military munitions and the chemical and nuclear industries are major sources contributing to the presence of perchlorate. Perchlorate is very stable in the environment and difficult to remove with conventional techniques. Novel technologies are needed for removing perchlorate in a simple, fast, cost-effective, and environmentally friendly manner. The objective of this project was to develop an innovative and cost-effective technology based on an electroactive ion exchange technique combined with nanostructured electroactive ion exchange materials for treatment of perchlorate from wastewater generated by treatment processes. Extension to drinking water is feasible because the perchlorate uptake step is essentially an ion exchange at open circuit, thus no pretreatment is required.
The electrically switched ion exchange (ESIX) technology combines ion exchange and electrochemistry to provide a selective and reversible method for removing target species from wastewater. In this technique, an electroactive ion exchange film is deposited on a conducting substrate, and ion uptake and elution are controlled directly by modulation of the potential of the layer, resulting in high efficiency use of electrical energy. The elution solution can be used repeatedly, minimizing secondary wastes and reducing costs normally required for standard ion exchange waste treatment. This project included fabrication of polyaniline nanowires and polyaniline coated on a conductive nanostructured matrix (i.e., carbon nanotubes or other nanocarbon) as electroactive ion exchange materials with extremely high surface area porosity.
The ESIX system was developed based on a conducting polymer/carbon nanotube nanocomposite for removing perchlorate from drinking water and wastewater. Conductive nanocarbon materials were used as the support for electrochemically fabricating a conducting polymer nanostructure and for improving the stability and electrochemical properties of an electroactive ion exchanger. The electroactive ion exchanger nanocomposite was incorporated into a flow reactor to selectively remove the perchlorates in wastewater. The results indicate that the ESIX technology is effective and selective for perchlorate removal and can potentially be used for large-scale treatment of wastewater.
This project demonstrated the viability of ESIX for removing perchlorate from wastewater. Ion loading and unloading are easily controlled by modulating the electrode potential. Compared with conventional ion exchange processes, the use of a regenerable material and the minimization of secondary waste are significant advantages in favor of the ESIX process.