This study examined the oxidation of phenol by electrochemical processes using different mixed-metal oxide (MMO) anodes, namely, Ti/Pt, Ti/IrO₂-Ta₂O₅, Ti/Ta₂O₅-SnO₂-IrO₂, Ti/RuO₂ and Ti/IrO₂-RuO₂. First, the effectiveness of different anodes by phenol oxidation was evaluated with the help of such parameters as cyclic voltammetry (CV), current efficiencies and degradation rates. The Ti/Pt anode was found to be the most effective of all types of anodes, as almost complete phenol degradation was gained with its use. Then, optimum operational conditions, applied current density and initial pH, were determined using Ti/Pt as the anode. By-products of phenol degradation (benzoquinone, hydroquinone, pyrocatechol, oxalic and maleic acid) arising gradually during the reaction were determined via high-performance liquid chromatography (HPLC) for all selected anodes. There was a considerable difference between the anodes with regard to degradation efficiency and concentrations of formed by-products. The toxicity was evaluated by measuring the natural luminescence of the bacteria, Vibrio fischeri, for all selected anodes. According to the toxicity assessment, a number of toxic by-products were formed from phenol degradation for all selected anodes. However, their toxicity decreased at the end of electrolysis on the Ti/Pt anode.

The oxidation of methylene blue (MB) by electrosynthesized ferrate(VI) in a semi-batch reactor is investigated. The effects of pH, Fe(VI) dose and initial MB concentration on the efficiency of the degradation process were studied. The original pH of MB solution was found more effective on the degradation and colour removal as 96.82% MB removal and 40.36% colour removal were gained. Initial MB solution and Fe(VI) dose affected the removal efficiencies. Degradation of MB by Fe(VI) was the second-order reaction kinetics. The density functional theory (DFT) analysis confirmed that density is intended mostly on the phenyl rings and least of all on the bonding orbitals of the middle heterocycle of МВ.

The degradation of atorvastatin (ATV) by electrosynthesised ferrate (VI) ion, electrocoagulation (EC) and peroxi-electrocoagulation (p-EC) were compared in this study. The effects of pH, Fe (VI) dose, electrode type, current density, supporting electrolyte concentration (SEC) and hydrogen peroxide concentration were investigated. All processes were affected by pH. Acidic pH values showed better efficiencies for each process, which was related to the drug’s solubility properties and dominant produced species with acidic values. Hybrid electrodes were found to be the most efficient electrode pairs. In EC, optimum pH value, current density and SEC were determined to be 3, 2.5 mA/cm² and 200 mg/L, respectively. The preferred pH and H₂O₂ concentration in the p-EC process were found to be 3 and 250 mg/L, respectively. Eighty-two per cent specific drug removal and 77% TOC removal were achieved. The performance of the processes for ATV degradation were found to be in the order of peroxi-electrocoagulation > Fe (VI) > electrocoagulation.

Ozonation and catalytic ozonation of humic acid (HA) in the presence of ZnO were examined in a batch scale reactor. The degradation of HA by catalytic ozonation was found to be much more effective than ozonation alone. The quantum chemistry calculations showed that the reaction of the O₃ disproportionation on the surface of ZnO corresponds to the barrierless mechanism. The activation energy of the transition state formation was −5.25 eV. The active oxygen atom formed on the surface of ZnO was found as interacting with both water molecules and dissolved organic molecules, which might lead to further oxidizing reactions.