SBIR Phase II: Low-cost Long-life Diamond Electrodes for Wastewater Treatment using Advanced Electrochemical Oxidation

This Small Business Innovation Research (SBIR) Phase II project will employ the boron-doped ultrananocyrstalline diamond (BD-UNCD) electrodes developed during the Phase I project to fabricate and characterize electrochemical cells and systems for the on-site generation (OSG) of advanced oxidants (chlorine-based mixed oxidants - hydrogen peroxide combined with hypochlorite - and sodium persulfate) and apply them to targeted water treatment applications. The primary research objectives are to determine the optimal conditions to generate oxidants and to establish the projected lifetime of the electrodes. BD-UNCD cells will demonstrate higher rates of oxidant production at lower costs and with greater energy efficiency than competing electrodes due to higher current densities and over-potentials for O2 and H2 evolution at the anode and cathode. The known difficulties with existing approaches of disinfection, such as the inadequate destruction of pathogens (Cryptosporidium), ineffective operation below 10°C, generation of large quantities of O2 and H2, and electrode fouling are expected to be mitigated substantially through use of BD-UNCD electrodes. Sodium persulfate (SPS) has been used as a highly effective oxidant capable of oxidative destruction of recalcitrant organics such as in oil-contaminated sea water. BD-UNCD technology will dramatically reduce the cost and increase flexibility of OSG water treatment using SPS. The broader impact/commercial potential of this project is the development of a safer, cheaper, more environmentally friendly technology to generate "green" oxidants using diamond electrodes that can be used for a number of water treatment applications including purification, disinfection, and remediation. The market for chlorine-based disinfection systems alone is $20 billion with a correspondingly large impact on human health and national security issues associated with transporting vast quantities of hazardous materials. Overcoming technical barriers that have prevented diamond from being used for oxidant generation will require advances in the synthesis and large-scale manufacturing of diamond thin films that will impact other applications of this material. The electrochemistry of diamond is not well understood in the conditions needed for OSG. Better understanding of these reactions and the technological trade-offs between cell design and electrode geometry will impact related applications including the development of compact systems for third-world potable water generation, small scale desalination, the energy efficient electrochemical synthesis of new materials and other point-of-use applications of advanced oxidants. Large scale on-site generation of persulfates will enable highly effective treatment of refractory organics found in oil contaminated sea water and waste water associated with bitumen refining.