Reaction kinetics and oxidation product formation in the degradation of acetaminophen by ferrate (VI)

This paper investigates the degradation of acetaminophen (AAP) in aqueous solutions by ferrate (VI), aiming to propose the kinetics, pathways and the oxidation products’ formation in the AAP degradation. A series of jar tests were undertaken over ferrate (VI) dosages (molar ratios of ferrate (VI):AAP, 5:1 to 25:1) and pH values (4–11). The effects of co-existing ions (0.2–5 mM) and humic acid (10–50 mg l −1 ) on the AAP removal were investigated. Ferrate (VI) can remove 99.6% AAP (from 1000 μg l −1 ) in 60 min under study conditions when majority of the AAP reduction occurred in the first 5 min. The treatment performance depended on the ferrate(VI) dosage, pH and the type and strength of co-existing ions and humic acid. Raising ferrate (VI) dosage with optimal pH 7 improved the AAP degradation. In the presence of humic acid, the AAP degradation by ferrate (VI) was promoted in a short period (<30 min) but then inhibited with increasing in humic acid contents. The presence of Al 3+ , CO 3 2− and PO 4 3− ions declined but the existence of K + , Na + , Mg 2+ and Ca 2+ ions can improve the AAP removal. The catalytic function of Al 3+ on the decomposition of ferrate (VI) in aqueous solution was found. The kinetics of the reaction between ferrate (VI) and AAP was pseudo first-order for ferrete (VI) and pseudo second-order for AAP. The pseudo rate constant of ferrate (VI) with AAP was 1.4 × 10 −5  L 2  mg −2  min −1 . Three oxidation products (OPs) were identified and the AAP degradation pathways were proposed.