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.