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Degradation of β-blockers in water by sulfate radical-based oxidation: kinetics, mechanism and ecotoxicity assessment
Tay, K. S. & Ismail, N. S. B.
Abstract
This study investigated the kinetics and degradation
pathway of acebutolol, metoprolol and sotalol in a
sulfate radical-based advanced oxidation process. The
selected pharmaceuticals were β-blockers which have been
used to treat cardiovascular diseases. Due to its frequent
use, the presence of these pharmaceuticals in the environment
has been regularly reported. In this study, sulfate
radicals were generated using peroxymonosulfate with
cobalt (II) as activator. At pH 7 and 25 °C, the second-order
rate constant for the reaction between SO4- with
metoprolol, acebutolol and sotalol was (1.0 ± 0.1) × 1010,
(2.0 ± 0.1) × 1010 and (3.0 ± 0.2) × 1010 M-1 s-1,
respectively. Sixteen transformation by-products were
identified from the selected β-blockers. These transformation
by-products were mainly formed through the hydroxylation,
aromatic ring-opening reaction and aliphatic chain
oxidation. The decomposition of β-blockers by sulfate
radicals was found to start from the formation of hydroxylated
β-blockers followed by an aromatic ring-opening
reaction. In general, this study showed that β-blockers
reacted favorably with sulfate radicals, and various transformation
by-products could be produced. The result from
the ecotoxicity assessment showed that almost all of the
transformation by-products were less toxic than its parent
compound. Therefore, a sulfate radical-based advanced
oxidation process could be an effective method for the
treatment of β-blockers in water.
Keywords
Acebutolol; Metoprolol; Sotalol; Advanced oxidation process; Water treatment; Transformation by-products
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