The effect of NOM to TiO2: Interactions and photocatalytic behavior

Natural organic matter (NOM) is ubiquitous in aquatic environment, which plays a predominant role in the sorption of pharmaceuticals onto the TiO2 nanoparticles. It is a matter of concern whether NOM could act as a surface sensitizer of TiO2 or not. In this context, the role of NOM is investigated for the photocatalytic degradation of carbamazepine (CBZ) using TiO2. Four different ratios of NOM:TiO2 were used varying from 400μgg-1 to 400mgg-1. The findings reveal that small amounts of NOM could enhance the TiO2 efficiency up to 8%. Electron paramagnetic spectroscopy (EPR), along with size exclusion chromatography with dissolved organic carbon detection (SEC-OCD) and nuclear magnetic resonance spectroscopy (NMR) reveal the occurring mechanism. TiO2 binds small molecular size fractions of NOM and breaks aromatic bonds of adsorbed NOM transforming it to stranded alkyl groups. This modified TiO2 bears a significant amount of electrons (e-) and lesser holes (h+) than the purified TiO2 and when irradiated, produces hydroxyl radicals which degrade CBZ

Inhibitory effect of NOM in photocatalysis process: Explanation and resolution

The present study explained the inhibitory effect of natural organic matter (NOM) on the photocatalytic degradation of clofibric acid (CA), and attempted to eliminate this inhibition by changing reaction conditions. The NOM degradation was followed by size-exclusion chromatography for dissolved organic carbon and ultraviolet absorption (SEC-DOC and SEC-UV254).The results demonstrated that the deactivation of NOM on catalyst was more dependent on the molecular weight of NOM than on its concentration. Higher molecular weight fractions were prone to adsorb onto the catalysts’ surface and acted as electron-hole scavengers and light filters to reduce the photocatalytic degradation rate of CA. pH adjustment changed the adsorption property of NOM, while, decreasing of its inhibition was not observed. However, the oxygen addition can significantly eliminate this inhibitory effect by increasing the degradation rate of high molecular size fractions of NOM