Sulfate radicals mediated oxidation of amoxicillin: Optimization of key parameters.

The lack of selectivity of hydroxyl radical species used in Advanced Oxidation Processes (AOPs) to eliminate organic pollutants has swayed the investigation towards more selective oxidizing agents. In the current work, we investigated the oxidation of amoxicillin, the most commonly used antibiotic worldwide, by sulfate radical species generated from the activation of Persulfate (PS) and Peroxymonosulfate (PMS-Oxone®). The optimization of this oxidation using the box-behnken experimental design was conducted. From this study, it was shown that the PS/Fe2+ mixture was capable of dose-dependently inducing a significant amount of degradation of the Amoxicillin compound with a higher degradation rate detected with higher amounts of PS and Fe2+. Sulfate radicals generated from the "Oxidant-Catalyst" mixture were shown to be the predominant oxidizing species involved in this process with the second order rate constant of Amoxicillin degradation found to be equal to 2.79 × 109 M-1. S-1. In the optimization procedure, the box-benhken methodology allowed us to assess the impact of various factors and their interaction on COD removal efficiency (mineralization rate), which is the objective response needed to be optimized. The variables considered were PS as the oxidant, Fe2+ as the catalyst, and pH. It was concluded that among the various parameters tested, pH was the most influential as a decrease in pH values was shown to be positively correlated with a significant increase in COD removal rate. Hence, the highest mineralization rate of Amoxicillin (≈76.10% COD removal) was achieved with PS = 300 µM, Fe2+ = 250 µM, and a pH value of 3.