Photoassisted defluorination of fluorinated substrates and pharmaceuticals by a wide bandgap metal oxide in aqueous media

Abstract

Persistent fluorinated substances, such as the fluorine-bearing pharmaceutical drugs Fluoxetine (FLX; Prozac) and Fluvoxamine maleate (FOM) together with several other substrates (fluorobenzoic acid and fluoroaliphatic model compounds), were photochemically defluorinated and degraded under UVC illumination in relatively good yields in the presence of a wide band gap metal oxide (β-Ga2O3) in heterogeneous aqueous media. The formation of fluoride ions increased with increasing illumination time under an inert nitrogen atmosphere, the transformation of the aromatic moiety was slower under these conditions, but nonetheless it did occur. The optimal amount of β-Ga2O3 loading for defluorination was 50 mg in aqueous media (0.10 mM, 100 mL); the optimal pH to defluorinate FLX was pH 6. Platinization (1 wt%) of the gallium oxide particles enhanced defluorination under an inert nitrogen atmosphere, but was decreased under an oxygen atmosphere; however, in the latter case the degradation of the substrates was facilitated as witnessed by loss of the aromatic moiety. The Ames test on the intermediate products from the photodegradation of FLX and 4-(trifluoromethyl)benzoic acid after long illumination times revealed that none were mutagenic.

Photodegradation of Fluoxetine Applying Different Photolytic Reactors: Evaluation of the Process Efficiency and Mechanism

“…However, the dehalogenation is also verified from the first instants of irradiation, presenting a slightly linear variation throughout the study period (Figure 5c). Furthermore, the data is compatible with the literature, 16 which observes a formation of approximately 2.28 mg L -1 of fluoride after 2 h of irradiation of 35 mg L -1 FLX, and the present study verified 2.2 mg L -1 of fluoride formation for experimental conditions (45 mg L -1 FLX, 1 h, without catalyst), evidencing the tendency of dehalogenation.…”

“…During the degradation of FLX, the formation of TFMP and the release of fluoride ions show a rupture of the ether bond of the compound and other dehalogenation mechanisms ( Figure 6). The mechanism of degradation by radical attack has been reported in the literature, 16 suggesting that photolysis of water allows the formation of highly reactive hydroxyl radicals. In the present study, the formation of hydroxyl radicals was confirmed for the UV/MW reactor by COU.…”

“…Some of the TPs of FLX may undergo dehalogenation through photolytic/photocatalytic degradation and monitoring the additions of fluoride in the solution is indirectly related to the degradation of FLX. 15,16 The pseudo-first-order kinetics for the formation of fluoride after degradation of FLX was reported in the literature, 6,15 showing that the values of the constants are influenced by medium conditions (pH and process time).…”

“…According to the results obtained and illustrated in Figures S1 and S2 (Supplementary Information (SI) section), the TPs presented in the FLX degradation mechanism are observed in both reactors (UV and UV/MW), and correspond to photolysis, hydrolysis and oxidation processes of FLX, as reported in the literature. 10,16,19 The degradation of the FLX presents as main transformation product, TP4, the process being initiated by hydrolyzing the bond carbon and following the oxidation of the aromatic ring. These results are in agreement with the fluoride formation data in the reaction system, since TP4 is the result of the dehalogenation process, following the stoichiometry of 1:2 (FLX:fluoride).…”

“…[8][9][10][11] It is important to note that the efficiency of degradation of chemical compounds through different processes needs to be verified through some important parameters, such as energy consumption, reagent costs, process time, TPs and, in particular, chemical kinetics. 12,13 Hence, the studies attribute a kinetic behavior of pseudofirst-order for the degradation of FLX, [14][15][16] which may can occur through direct photolysis, indirect photolysis, and hydrolysis. 17 Hydrolysis is not very acceptable since, after a long period of permanence in a degradation system, the hydrolytic degradation of FLX has not been observed.…”