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

• Oxidation products (OPs) and pathways of the acetaminophen (AAP) degradation were proposed.
• Raising ferrate (VI) dosage and the optimal pH 7 improved the reduction of AAP.
• Humic acid promoted to the AAP oxidation by ferrate(VI) in the first 30 min reactions.
• Al3+, CO32− and PO43− declined but K+, Na+, Mg2+ and Ca2+ improved the AAP removal.
• Decomposition of ferrate (VI) was catalytically accelerated by the presence of Al3+.

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 Al3+, CO32− and PO43− ions declined but the existence of K+, Na+, Mg2+ and Ca2+ ions can improve the AAP removal. The catalytic function of Al3+ 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 L2 mg−2 min−1. Three oxidation products (OPs) were identified and the AAP degradation pathways were proposed.