The photogenerated electrons on the photocatalyst surface (R1) react with adsorbed oxygen and ozone molecules as electron acceptors (R5) and (R6) [41,42], and these reactions are important 210 M. Mehrjouei et al. / Chemical Engineering Journal 263 (2015) 209–219to decreasing the recombination rate of electron–hole pairs. The recombination of electrons and holes negatively affects reduction and oxidation reactions on the photocatalyst surface, quantitatively decreasing the effective interactions and consequently reducing the performance of this technology.