min. After addition of TiO2, the suspension was again pumped for 30 min. Subsequently, a reference sample was taken using a syringe equipped with filter (Xtra PA-20/13 CHROMAFIL®, MACHERY-NAGEL GmbH & Co. KG) to separate the photocatalyst. The experiment was started by switching on the LED. Samples were analyzed using a cuvette UV/Vis spectrometer (Novaspec III, Amersham Biosciences Europe GmbH) monitoring the absorption band at 660 nm.