The higher and
lower kP values of the composites can be interpreted as
being due to the effect of adsorption or desorption in
addition to photodecomposition. In experiments where the
initial MB concentration is 0.1 mM, [five times greater
than in the previous experiments (Fig. 7)], the kP1 values of
the two TiO2 samples was reduced by 1/5 times those
measured at the lower MB concentration, showing a linear
relationship with the initial MB concentration. Although
the decomposition data of the TiO2 samples can be fitted by
a single straight line at the lower concentration, two
straight lines are necessary to fit of the data at the higher
concentration. The kP1 values of the composites containing
P25 are higher than those containing ST-01. This difference
is suggested to be due to two factors, a greater degree
of decomposition by P25 and a greater degree of adsorption
by MPS. The kP values of both types of composites are