Electrochemically assisted decomposition of ozone for degradation and mineralization of Diuron

In this work, we explore the possibility of enhancing the ozonation of a solution of Diuron by combination with electrochemical processes. To this aim, the ozonation was performed in a membrane free electrolyzer where a reticulated vitreous carbon (RVC) and a stainless steel (SS) cathode have been alternatively tested and compared. The effect of pH, current density and ozone flow on degradation and mineralization of Diuron has been investigated. The involvement of radical species has been verified by means of test conducted with selective scavenging agents. The results show that both cathodes can promote the decomposition of ozone and therefore the degradation of Diuron. The use of scavengers has shown that the removal of Diuron is driven by means of radical species. Depending on the adopted materials, different mechanisms occur and different operating conditions are required. In particular, the use of a carbon-based cathode implies the production of hydrogen peroxide and therefore the occurrence of an Electro-peroxone process, which is favored at alkaline pH and low current values. On the other hand, the adoption of a metal cathode, whose efficiency is highly promoted by acidic pH and high currents, implies the direct reduction of ozone with the production of hydroxyl radicals.