Advanced oxidation process of valsartan by activated peroxymonosulfate: Chemical characterization and ecotoxicological effects of its byproducts

Abstract

In recent years, the antihypertensive drug Valsartan (VAL) has been detected in surface waters up to concentrations of 6300 ng/L, due to its high consumption and its mostly unchanged excretion. Moreover, wastewater treatment plants fail to completely mineralize/transform it, as evidenced by findings of up to 3800 ng/L in some effluents. In this paper, the possible degradation of VAL was evaluated through Fenton-like reaction with activation of peroxymonosulfate in the presence of Fe(II) under neutral conditions. Fourteen degradation byproducts were isolated and completely identified by both nuclear magnetic resonance and mass spectrometry, five of which were discovered for the first time, and a mechanism of their formation was proposed. Furthermore, the potential acute and chronic toxicity of valsartan and its byproducts in the aquatic environment were evaluated in key organisms of the freshwater trophic chain belonging to producers and consumers, the alga Raphidocelis subcapitata and the rotifer Brachionus calyciflorus, respectively. Acute effects occurred at concentrations in the order of tens/hundreds of mg/L, far from those of environmental concern. As regards chronic effects, algae were not particularly affected by the parent compound and its derivatives, while rotifers were less affected by derivatives (effective concentrations at units/tens of μg/L) compared to valsartan (effective concentrations at hundreds of ng/L).