Preparation, characterization and photocatalytic performance of pyrolytic-tire-char/TiO2 composites, toward phenol oxidation in aqueous solutions

Abstract

A pyrolytic char/TiO2 (PC/TiO2) composite material, where PC was derived from recycled tires, was prepared by the sol–gel method. XRD analysis showed formation of TiO2 anatase phase, as well as, a small fraction of brookite phase. UV–vis DRS spectroscopy showed that PC/TiO2 composites have enhanced absorption at visible wavelengths 340–450nm. The photocatalytic activity and the promoting effect of PC/TiO2 composite catalysts were investigated for the degradation of phenol in aqueous suspensions. The photocatalytic degradation followed pseudo-first order kinetics. The ratio TiO2:PC (w:w) largely affected the performance of the composite catalysts. The optimal (w:w=0.1) ratio was found e.g., (0.2g PC, 2g TiO2). An important finding is a significant promoting effect of PC on the photocatalytic performance of TiO2. Electron paramagnetic resonance (EPR) spectroscopy showed that the pyrolytic char acts as a very efficient electron-acceptor from TiO2 particles under UV–vis irradiation. This resulted in decreased electron–hole pair recombination and subsequently in enhanced production of OH-radicals that oxidized phenol. Thus, PC matrix can act as an electron storage matrix for photo-induced electrons from TiO2.