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Kinetics and mechanism of electron transfer reactions: Oxidative degradation of fluoroquinolone drugs in aqueous acidic/alkaline medium†

Authors : Vijay Devra* and Gajala Tazwar



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Abstract

 

Pharmaceuticals, especially antibiotics, have received increasing global concern, due to their intensive use in the environment and potential harm to ecological system as well as human health. Among various antibiotics, fluoroquinolones are of extreme interest, since they are broad-spectrum antibacterials with agrowing demand in hospitals, households, and veterinary applications. Wastewater discharge from conventional wastewater treatment plants isthe main source of fluoroquinolone in the aquatic environment. Removal of fluoroquinolone residue from aquatic environment is, therefore, considered as a priority and serves as an important study. For the degradation of FQs in aqueous solution, interesting remedy processes are required such as oxidation-degradation process in which formed intermediates mineralized into CO2, water, and mineral species. The electron transfer reactions and their mechanisms are of much importance in understanding various types of biochemical, pharmaceutical and industrial reactions. Kinetics has played a significant role in understanding the intricacies’ of such reactions. Nanosized colloidal manganese dioxide, hexacyanoferrate(III), diperiodatocuprate(III), potassium permanganate etc. used as effective oxidants for oxidative degradation of different fluoroquinolone antibacterial agents in aqueous acidic/alkaline system. In this regard, we investigated a kinetic study of oxidation of moxifloxacin (MF) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium. The reaction was first order with respect to [DPC] and less than unity order with [MF]. The pseudofirst order rate constant (kobs) changes differently under different concentration of alkali. The results indicates at higher hydroxyl ion concentration DPC complex exist in CuL whereas at lower hydroxyl ion concentration in form of Cu(HL)2. The thermodynamic

parameters associated with the oxidation reaction have been evaluated and discussed.

Keyword

Fluoroquinolone, aqueous alkaline medium, thermodynamic parameters, kinetics, oxidation