Development of metal- and carbon-based nanoscale materials for persulfate activation Our group has explored the applicability of various metal- and carbon-based nanomaterials for persulfate activation in which peroxymonosulfate or peroxydisulfate is reductively transformed into highly reactive sulfate radical. We recently demonstrated a first instance of application of noble metals as potential persulfate activators for oxidative organic degradation. Among the tested metals, palladium outperformed cobalt ion as a benchmark persulfate activator in terms of treatment efficiency, and platinum and gold showed a clear distinction in the activation mechanism: persulfate activation involving no radical formation. Current research focuses on comparatively evaluating transition and noble metals for persulfate activation, identifying key mechanism underlying persulfate activation (reductive conversion to sulfate radical versus electron transfer mediation), and developing new activators based on nanoscale metals, metal oxides, carbon materials, and their composites.
Visible light induced oxidation of organics by nanoscale sensitizing and catalytic systems Our group has been interested in diverse visible light responsive systems for initiating oxidative degradation of organics in water. C60 fullerene and porphyrin derivatives as metal-free materials were demonstrated to sensitize production of singlet oxygen via energy transfer and cause oxidation of select organics (e.g., cimetidine and ranitidine). We also reported in the literature that triplet state-induced oxidation involving tin porphyrin is highly effective for treating microcystins under visible light irradiation. In an effort to employ visible light activity of WO3 that undergoes fast recombination of electron-hole pairs due to the inappropriate conduction band edge potential, we explored the new combination systems consisting of WO3 and Fenton reagent or various inorganic oxyanions. These research efforts aid in guiding future research works related to application of fullerenes for viral inactivation with visible light and development of visible light active silver- or bismuth-based materials for photocatalysis.
Electrochemical oxidation systems for treatment of wastewaters with high organic and ammonia-nitrogen concentrations Our group has started research regarding electrochemical oxidation of organics and removal of ammonia-nitrogen in water. We proposed the sequential combination of electro-Fenton oxidation and electrochemical chlorination with DSA (dimensionally stable anode) to achieve concomitant mineralization of organics and conversion of ammonia into dinitrogen (with minimal formation of nitrate). The combined system has been demonstrated to effectively treat real effluent released from anaerobic digestion of food wastes - characterized by high concentrations of organics, ammonia-nitrogen, and chloride. This research effort recently leads to development of electrochemical systems using BDD (boron-doped diamond) or substoichiometric TiO2 (e.g., Ti3O7, Ti4O9) electrodes for oxidative treatment of high COD wastewaters.
