Photocatalytic decomposition of metoprolol and its intermediate organic reaction products: Kinetics and degradation pathway

High purity metoprolol prepared by neutralization of an aqueous solution of metoprolol tartrate is efficiently mineralized to CO2 and water by photocatalysis with TiO2, UV light and a constant flow rate of oxygen. Since the tartrate anions were eliminated, all the HO• generated by photocatalysis reacted efficiently with the aromatic part of the medication. The reaction pathway includes two routes of degradation. The first one includes the transformation of metoprolol to hydroquinone via formation of 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde. Metoprolol is also degraded directly to hydroquinone. Then, this aromatic compound is oxidized to 1,2,4-benzenetriol, which is rapidly oxidized to low molecular weight organic acids before being completely mineralized to CO2 and water. Kinetic studies indicated that the initial reaction rate of the degradation of metoprolol, 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde is described by the LH-HW model. © 2016 by De Gruyter 2016.

metoprolol; pharmaceuticals; photocatalytic degradation; reaction pathway Aromatic compounds; Biodegradation; Carbon dioxide; Catalysis; Chemical reactions; Drug products; Ethanol; Phenols; Photocatalysis; Reaction intermediates; Solutions; 2-(4-Hydroxyphenyl)ethanol; 4-hydroxybenzaldehyde; Degradation pathways; Low molecular weight organic acid; Metoprolol; Photo catalytic degradation; Photocatalytic decomposition; Reaction pathways; Reaction kinetics

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