Oxidation of β-lactam antibiotics by ferrate(VI)

Amoxicillin (AMX) and ampicillin (AMP), penicillin class β-lactam antibiotics, have been detected in wastewater effluents and their release into the environment may involve long-term risks such as toxicity to aquatic organisms and endocrine disruption in higher organisms. This paper demonstrates the removal of AMX and AMP by ferrate(VI) (Fe(VI)) by performing kinetics and stoichiometric experiments. The dependence of the second-order rate constants of the reaction between Fe(VI) and AMX (or AMP) on pH was explained using acid–base equilibria of Fe(VI) and organic molecules. The kinetics study with the model compound, 6-aminopencillanic acid and the pH dependence behavior suggested that Fe(VI) reacted with the amine moieties of the studied β-lactams. The reactivity of different oxidants with AMX have been shown to follow the sequence: OH≈SO4- > bromine > ozone > chlorine > Fe(VI). The required molar stoichiometric ratios ([Fe(VI)]:[β-lactam]) for the complete removal of AMX and AMP by Fe(VI) were about 4.5 and 3.5, respectively. The Fe(VI) is able to eliminate AMX and AMP and hence is likely to also oxidize other β-lactams effectively.

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• β-Lactams, amoxicillin (AMX) and ampicillin (AMP) were oxidized by ferrate(VI).
• Kinetics for AMX and AMP oxidation by ferrate(VI) were second-order.
• Second-order rate constants were pH dependent.
• Ferrate(VI) likely reacting with the amine moiety of β-lactams under study.