Oxidative decomposition of volatile organic compounds using thermally-excited activity of hydroxyapatite

Oxidative decomposition of volatile organic compounds, i.e. toluene, on hydroxyapatite (HAp) under high temperatures was studied. Gaseous toluene, ethyl acetate and iso-propanol, decomposed oxidatively and converted to CO and CO2 effectively at 400-500 °C over stoichiometric or calcium-deficient HAp. From the direct measurement of ESR spectra under high temperatures, the ESR signals (g-value at around 2.003) for stoichiometric and calcium-deficient HAp under 300-400 °C were assigned to the electron trapped on vacancy in HAp. Then, it was concluded that volatile organic compounds were decomposed by the active oxygen radical due to the electron trapped on vacancy in HAp under high temperatures. We propose that HAp has also thermally-excited activity similar to TiO2.

► We would like to propose that HAp has also thermally-excited activity in addition to the normal catalytic property with active site. ► The oxidation of VOCs must be caused by the activation of oxygen due to the electron trapped on vacancy in HAp from our ESR studies. ► The efficiency of the complete oxidation for VOCs on stoichiometric HAp exceeded to that on calcium-deficient HAp. ► That is, the oxidative activity of stoichiometric HAp was higher than that of calcium-deficient HAp. ► The difference of ESR signal intensity of each HAp sample would show that of the activity.