Unprecedented Treatment Strategy of Aquatic Environments:\nOxidative Degradation of Penicillin G by Chromium Trioxide in Acidic\nMedia and the Impact of Metal Ion Catalysts: Kinetics and Mechanistic\nInsights

Degradation kinetics\nand pathways of the antibiotic penicillin\nG (Pen) have been examined via oxidation by chromium trioxide (Cr<sup>VI</sup>) in aqueous sulfuric and perchloric acid media. The oxidation\nreactions were monitored by spectrophotometry at 298 K. In both acidic\nmedia, penicillin G oxidation was set to proceed through acid catalysis.\nThe stoichiometry of the reactions designated that 3 moles of Pen\nrequired 2 moles of Cr<sup>VI</sup>. The kinetics of Pen oxidation\nin both acids was of the first order with regard to [Cr<sup>VI</sup>] and less-than unity order with regard to [Pen] and [H<sup>+</sup>] in their variation. The rates of reactions displayed negligible\nimpacts upon altering ionic strengths or dielectric constants of the\nreaction media. There was no intrusion of free radicals throughout\nthe redox reactions. Addition of low concentrations of Ni<sup>2+</sup>, Cu<sup>2+</sup>, and Zn<sup>2+</sup> ions enhanced the oxidation\nrates, while addition of Cr<sup>3+</sup> as a described product did\nnot noteworthily alter the rates. Under comparable investigational\ncircumstances, the oxidation rates in HClO<sub>4</sub> were almost\n2-fold greater than in H<sub>2</sub>SO<sub>4</sub>. The oxidation\nproducts of penicillin G were identified by spectral analysis and\nspot tests as phenyl acetic acid, 2-formyl-5,5-dimethyl-thiazolidine-4-carboxlate\nion, ammonium ion, and carbon dioxide. Reliance of reaction rates\non temperature has been explored, and the activation and thermodynamic\nparameters were estimated and debated. In view of the noted reactions’\norders and products’ identification, a plausible mechanism\nfor the oxidation reactions was suggested. The derived rate law was\nset to be in accordance with the acquired results. This study offers\nan unprecedented simple and low-cost treatment method for removal\nor degradation of certain pollutants for protecting the environment\nand human health.