The photocatalytic tests were performed as follows: 100 mg
of TiO2 powder and 50 mL of 0.1 mg L−1 toluidine blue
solution were transferred into 100 mL beakers and placed
under gentle agitation on a magnetic stirrer in the student-made
test chamber. The samples were then exposed to UV light for 3
h. At regular intervals, 2 mL aliquots were taken from the
solutions and placed in centrifuge tubes kept in a dark container
until being centrifuged. After centrifugation, samples were
transferred into cuvettes to measure their absorbance at 630
nm. The dye concentration (Cdye) of these solutions was
calculated using a calibration curve that the students acquired
before the catalytic tests.