Photocatalytic Degradation of Diclofenac by Hydroxyapatite–TiO2 Composite Material: Identification of Transformation Products and Assessment of Toxicity

Abstract

Diclofenac (DCF) is one of the most detected pharmaceuticals in environmental water matrices and is known to be recalcitrant to conventional wastewater treatment plants. In this study, degradation of DCF was performed in water by photolysis and photocatalysis using a new synthetized photocatalyst based on hydroxyapatite and TiO2 (HApTi). A degradation of 95% of the target compound was achieved in 24 h by a photocatalytic treatment employing the HApTi catalyst in comparison to only 60% removal by the photolytic process. The investigation of photo-transformation products was performed by means of UPLC-QTOF/MS/MS, and for 14 detected compounds in samples collected during treatment with HApTi, the chemical structure was proposed. The determination of transformation product (TP) toxicity was performed by using different assays: Daphnia magna acute toxicity test, Toxi-ChromoTest, and Lactuca sativa and Solanum lycopersicum germination inhibition test. Overall, the toxicity of the samples obtained from the photocatalytic experiment with HApTi decreased at the end of the treatment, showing the potential applicability of the catalyst for the removal of diclofenac and the detoxification of water matrices.

Sonophotocatalytic degradation of sodium diclofenac using low power ultrasound and micro sized TiO2

“…Among the other transformation products detected during photocatalytic and ultrasound-assisted photocatalytic tests, TP5 presents two hydrogen atoms less that TP4, supporting the formation of a benzoquinone imine (pathway B), in agreement with the literature [62]. The TP2 species could result from the loss of a chlorine substituent in DC, causing a cyclization reaction that leads to the formation of a carbazole ring (pathway D).…”

“…It should be noted that our results support similar reaction pathways for photocatalytic and ultrasoundassisted photocatalytic DC degradation. Figure 6 shows that oxidation is one of the major degradation mechanisms, as confirmed by the identification of TP1 and TP4, and in good agreement with the literature about photocatalytic and sonolytic DC degradation [62]. In particular, hydroxyl radicals seem to play a major role, supporting the proposed mechanism of synergistic enhancement.…”

Chlorapatite Derived from Fish Scales

“…Calcium phosphate-based materials have been employed in a wide range of applications such as: biomedical [1][2][3][4]; wastewater treatment [5,6]; soil remediation [7]; foam [8]; display and solid state lightning [9]; and heterogeneous catalysis in chemical, material and industrial industries [10]. Calcium phosphate compounds can either be produced from inorganic precursors or from natural organic based materials.…”

Conversion of spent coffee grounds to biochar as promising TiO2 support for effective degradation of diclofenac in water

“…The results obtained in the degradation of DCF from the compound prepared in this work show that the hole and hydroxyl radicals generated by B1T1 follow the same cleavage pathway for the DCF molecule shown by other searches. [ 55–58 ]…”