Mechanisms of hydrogen generation during the mechanochemical treatment of biotite within D2O media

The mechanism of hydrogen generation during the mechanochemical treatment of biotite was examined by grinding experiments using a ball mil in H2O or D2O as a grinding media. From the linear relationship between the amount of generated hydrogen and the increase of the surface area of ground powders, the hydrogen productivity of biotite is estimated to be 0.036 μmol/m2, which agrees with the previous results in spite of the difference in the grinding conditions. D2 analyses by a mass spectrometry indicate that the produced amount of D2 accounts for only 10% of the total hydrogen and that more than 90% of hydrogen takes a form of a mixture of HD and H2. The observed isotope distribution clearly indicates that hydroxyls within the crystal structure can be a major source for the generation of hydrogen. Hydrogen generation originated from hydroxyls may indicate the higher hydrogen productivity of phyllosilicates than those of quartz and alkali feldspar.