Water scarcity affects close to a third of the world population. Efficient, affordable and robust purification technologies are needed for a range of separation contexts, from point-of-source treatment or remote in-situ purification devices to large-scale, centralized wastewater treatment facilities. Micropollutants pose a particularly vexing problem in wastewater treatment, since current technologies suffer from high energetic penalties and performance limitations when confronted with pollutants at these very low concentrations (nM to μM), often in the presence of excess competing species. The increased use of heavy metals and metalloids in industrial, agricultural and technological applications has led to their wide distribution and persistence in natural water bodies and soils, while the production of metals through extraction and refining generally results in process streams containing dilute metals that are discarded with the tailings to sedimentation ponds, - there is now strong interest in exploring the potential for the recovery of such metals from the waste streams. Fine chemical processing, too, can be enhanced by the selective separation of by-products and unused reagents that can be recycled to enhance overall productivity of the process.  To address these concerns, we have developed a platform purification technology based on redox-mediated electrochemical modulation of the separation environment, which can, in many cases, offer significant advantages over conventional separation methods. For instance, redox-mediated chemical moieties tethered to electrode surfaces can be tailored to ensure adsorptive selectivity with high separation factors towards toxic pollutants, at low overpotentials and high current efficiencies. We exploit these organometallic polymeric electrodes to target pollutants ranging from pesticides to toxic heavy metals, with potential use in resource recovery. The capture and release of the target molecules are controlled solely by the electrochemical potential, and thus there is no need for chemical regenerants or post-treatment, with little chemical waste produced and low water usage ratios (&lt;0.05). We will discuss the overall concepts underlying this technology, with results on the recovery of micropollutant organic anions, neutral organic contaminants, and heavy metal ions, from water. We will also discuss the tailoring of the redox polymer electrodes to provide enhanced selectivity in fine chemical processing.

Redox-based electrochemical technologies for product purification, wastewater treatment and resource recovery

256th National Meeting (2018)

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