Degradação simultânea dos fármacos genfibrozila, hidroclorotiazida e naproxeno pelos processos TiO2/UV-A, TiO2/H2O2/UV-A e H2O2/UV-C em diferentes matrizes aquosas

Abstract

In this work it was evaluated the degradation of hydrochlorothiazide (HCTZ), naproxen (NAP) and gemfibrozil (GEM) by photoassited peroxidation (UV-C/H2O2), heterogeneous photocatalysis (UV-A/TiO2) in diferente aqueous matrices (deionized water - DW, river water - RW and effluent from sewage treatment plant – STP). Initially, it was evaluated the influence of photolysis (UV-C) in different pH values (4.0, 5.8 and 7.0) for DW and RW and pHs (4.0, 6.0 and 7.7) for STP, not significantly influencing the degradation efficiency, being chosen the values of pH 5.8 (DW and RW) and 7.7 (STP), as they are the natural pH of these matrices. Then, the influence of the H2O2 concentration was evaluated, obtaining the best efficiency in the concentration of 4.0 (DW and RW) and 64.0 mg L-1 (STP) after 30 min of UV-C irradiation. For the UV-A process, the influence of the TiO2 concentration was evaluated, resulting in a better concentration efficiency of 150 mg L-1 (DW and RW) after 120 min, and 450 mg L-1 (STP) after 240 min irradiation. In view of these results, the influence of the H2O2 concentration on the UV-A/TiO2 process was evaluated, obtaining a better efficiency in the concentration of 6.0 mg L-1 (DW and RW), not being observed the same behavior for the matrix of STP. Under these conditions degradation efficiencies above 90% (HCTZ and NAP) and 80% (GEM) were obtained in all matrices. Then under the best experimental conditions obtained, the reaction time was extended in the evaluated processes in all the matrices, in order to monitor the degradation efficiency of the pharmaceuticals, the evolution of the acute toxicity for the V. fischeri bacteria, the mineralization and H2O2 consumption. In the UV-C /H2O2 process (4.0 mg L-1 of H2O2), the degradation efficiency reached values below the detection limit (DL) for all pharmaceuticals in 60 min (DW); in RW, values below DL for the pharmaceuticals were reached in 90 min, with the exception of GEM; In STP (64 mg L-1 of H2O2) for all in 45 min. In this conditions, the mineralization was 43% (DW), 53% (RW) and 58% (STP) after 120 min of irradiation. UV-A/TiO2 degradation of all pharmaceuticals reached values below LD in 240 min (DW and RW) and 300 min (STP), the mineralization reached 38% (DW), 65% (RW) and 75% (STP). Addition of H2O2 (6.0 mg L-1), with replacement every 15 min, degradation of all the pharmaceuticals below their respective DL in 180 min in the DW and RW matrices, leading to a 65% mineralization (DW) and 85% (RW). When using solar radiation with the use of TiO2, the degradation efficiency was above 76% for all matrices when applying a energy dose of 448 kJ m-2, DOC removal reached 65% (DW), 58% (RW) and 52% (STP). The acute toxicity was evaluated as a function of the inhibition of the V. fischeri bacterium' luminescence, obtaining inhibition above 70% for all evaluated processes, indicating that the by-products generated are more toxic than the original pharmaceuticals. In a real application, these will be in lower concentrations and consequently sub-products will be generated in a lower concentration, which may not trigger any deleterious effects on the aquatic biota pharmaceuticals. There fore, the UV-A/TiO2 and UV-C/H2O2 processes can be used as a treatment alternative for the aqueous matrices, and solar radiation can be used in the UV-A/TiO2 process, making these technologies very innovative and viable.