Proposed transformation pathway and evolution profile of diclofenac and ibuprofen transformation products during (sono)photocatalysis

Abstract

Liquid chromatography time-of-flight mass spectrometry (UPLC/ESI-QToF-MS) was used for the elucidation of the main transformation products (TPs) resulting from the degradation of diclofenac (DCF) and ibuprofen (IBP) during the application of various advanced oxidation processes in aqueous matrices. The examined processes were TiO 2 photocatalysis driven by UV-A or simulated solar irradiation, sonolysis, and UV-A photocatalysis integrated with ultrasound irradiation (sonophotocatalysis). A comparison between the applied treatment processes was performed with respect to the substrates first-order kinetic rate constant. When compared with sonolysis and UV-A photocatalysis, a higher degradation rate was observed for sonophotocatalysis in the presence of 500 mg L −1 TiO 2 . Seven TPs of IBP and ten TPs of DCF under UV-A and simulated solar irradiation photocatalysis and sonophotocatalysis, formed by consecutive attack of hydroxyl radicals (HO • ) in concomitance with the degradation of the primary compounds, were tentatively identified. Overall, no differences were observed in the nature of TPs formed for each substrate among the experiments performed, indicating the involvement of similar reaction mechanisms. The degradation pathway of IBP includes mainly decarboxylation, demethylation and hydroxylation reactions, while the oxidation of DCF, mainly proceeded by oxidation and hydroxylation reactions between chloroaniline and phenylacetic acid. An important observation made during the experiments was that the hydroxylated species (1 -OH-IBP; 2 -OH-IBP; 4 -OH-DCF; 5 -OH-DCF) remained in the solution until 120 min. Finally, the results demonstrated the capacity of the sonophotocatalysis to reduce the initial toxicity of IBP and DCF aqueous solutions against the water flea Daphnia magna yielding 20% and 40% immobilization, respectively, at the end of the treatment.

Synthesis of Ag3PO4/G-C3N4 Composite with Enhanced Photocatalytic Performance for the Photodegradation of Diclofenac under Visible Light Irradiation

“…Several studies have investigated DCF removal in the advanced oxidation processes. Michael observed an 80% DCF (the initial concentration was 10 mg L −1 ) removal efficiency in 120 min with TiO 2 as the catalyst under a sonocatalytic process [45]. Shan found that 80% DCF (the initial concentration was 20 mg L −1 ) was removed in 40 min with FeCeO x under an ultrasonic system [46].…”

“…Several studies have investigated DCF removal in the advanced oxidation processes. Michael observed an 80% DCF (the initial concentration was 10 mg L −1 ) removal efficiency in 120 min with TiO2 as the catalyst under a sonocatalytic process [45]. …”

Degradation of pharmaceuticals by ultrasound-based advanced oxidation process

“…Similar pattern was also applied during the sonophotocatalytic degradation of diclofenac. Similarly, the degradation pattern of ibuprofen involved hydroxylation, demethylation, decarboxylation, cleavage of isobutyl moiety and oxidation of hydroxyl groups (Michael et al 2014). Twenty intermediate products are reported during the sonophotocatalytic degradation of ofloxacin.…”

“…The degradation rate of ibuprofen is 49 9 10 -3 min -1 and that of diclofenac is 40 9 10 -3 min -1 with conversion percentage of 85 % for ibuprofen and 96 % for diclofenac, respectively Michael et al (2014) Environ Chem Lett …”

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU

“…Concerning these compounds, there are several works reporting AOPs to treat diclofenac (Calza et al, 2006;Guyer and Ince, 2011;Martínez et al, 2011;Michael et al, 2014;Naddeo et al, 2010;Naddeo et al, 2009;Pérez-Estrada et al, 2005;Rizzo et al, 2009;Zhang et al, 2011) as well as both hormones (Dimitroula et al, 2012;Frontistis et al, 2012;Frontistis et al, 2011;Pereira et al, 2012). Data regarding these particular compounds can be consulted in article reviews that have been published in the last few years and that already encompass a lot of information dealing with the removal of these compounds from water by using AOPs Kanakaraju et al, 2014;Klavarioti et al, 2009;Liu et al, 2009;Luo et al, 2014;Rivera-Utrilla et al, 2013;Silva et al, 2012).…”