Kinetic Modeling-Assisted Mechanistic Understanding of the Catalytic Ozonation Process Using Cu-Al Layered Double Hydroxides and Copper Oxide Catalysts

In this study, copper aluminum layered hydroxides (Cu-Al LDHs) and copper oxide (CuO) were utilized as catalysts for heterogeneous catalytic ozonation (HCO). Target compounds oxalate and formate were used with removal by adsorption and oxidation quantified to elucidate the role of the catalyst in contaminant removal. Oxidation of oxalate mostly occurred on the catalyst surface via interaction of surface oxalate complexes with surface-located oxidants. In contrast, the oxidation of formate occurred in the bulk solution as well as on the surface of the catalyst. Measurement of O-3 decay kinetics coupled with fluorescence microscopy image analysis corresponding to 7-hydroxycoumarin formation indicates that while surface hydroxyl groups in Cu-Al LDHs facilitate slow decay of O-3 resulting in the formation of hydroxyl radicals on the surface, CuO rapidly transforms O-3 into surface-located hydroxyl radicals and/or other oxidants. Futile consumption of surface-located oxidants via interaction with the catalyst surface was minimal for Cu-Al-LDHs; however, it becomes significant in the presence of higher CuO dosages. A mechanistic kinetic model has been developed which adequately describes the experimental results obtained and can be used to optimize the process conditions for the application of HCO.

Automated summary

In this study, copper aluminum layered hydroxides and copper oxide were used as catalysts for heterogeneous catalytic ozonation, targeting the removal of oxalate and formate contaminants. The role of the catalyst in contaminant removal was elucidated, with Cu-Al LDHs facilitating slow decay of O-3 to form surface hydroxyl radicals, while CuO rapidly transforms O-3 into surface-located hydroxyl radicals and/or other oxidants. Futile consumption of surface-located oxidants via interaction with the catalyst surface was minimal for Cu-Al LDHs, but becomes significant with higher CuO dosages.