Review on the Impact of Natural Organic Matter (NOM) on the Degradation of Emerging Contaminants in Persulfate-Activated Advanced Oxidation Processes (AOPs)

Natural organic matter (NOM) consists of a broad range of chemical compounds with different molecular structures usually present in natural surface water. The co-existence of NOM in surface water, streams, lakes, and rivers poses a serious challenge to the practical application of persulfate-activated advanced oxidation processes (AOPs). NOM can easily adhere to the surface of catalysts blocking the active sites with numerous oxygen groups serving as a barrier between the persulfate, catalysts, and organic contaminants. This inhibitive effect has been credited to the competition for the reactive oxygen species between the organic contaminant and NOM (e.g., humic acid). Moreover, it can act as an OH– scavenger as well as a scavenger of positive holes (h+) effectively forming a barrier limiting the reaction of persulfate with catalysts. Therefore, this short review examines the negative impact of NOM on persulfate-activated AOPs and different ways to which this can be mitigated.