title: Optimization of fipronil degradation by heterogeneous photocatalysis: Identification of transformation products and toxicity assessment.
abstract: In this work it was studied the degradation of the insecticide fipronil (FIP) by heterogeneous photocatalysis induced by TiO2P25. Using chemometric methods (Factorial Design and Response Surface Methodology), it was possible to evaluate the role of interaction between pH of the reaction medium, the reaction time and concentration of TiO2, optimizing the conditions for degradation using artificial radiation. Under the optimized conditions (79.4 mg L-1TiO2and 66.3 min of reaction time for 1.1 mg L-1of FIP, at pH 5.6-5.8 (natural pH of the irradiated suspension)), 90.9% of FIP degradation was achieved at a degradation rate of 1.54 × 10-2m2kJ-1in terms of accumulated UVA radiation, corresponding to a pseudo-first order rate constant of 1.34 × 10-2min-1and a half-life of 51.7 min. Under the same conditions, these assays were extended to the use of solar radiation, when the degradation rate was 14% higher, with half-life of 45 min, suggesting that in both cases FIP degradation was successful. Four by-products of FIP photocatalytic degradation could be separated, identified, and their formation and consumption followed by UHPLC-Q-TOF. Although the same intermediates have been obtained using both irradiation sources, a faster degradation of the transformation products (TPs) was observed under solar irradiation due to its expressive photonic flux covering the UVA and UVB. It is noteworthy that both the untreated effluent and the identified compounds have low toxicity with respect to V. fischeri, suggesting that the heterogeneous photocatalysis may be a good alternative for treatment of wastewaters containing FIP and its TPs, mainly when solar radiation is the source of radiation, since under this condition the power consumption during the treatment can be significantly reduced.
authors.affiliation: Universidade Federal de Uberlândia, Instituto de Química, 38400-902, Uberlândia, MG, Brazil. Electronic address: oswaldogjr@hotmail.com.
authors.forename: Oswaldo
authors.initials: O
authors.lastname: Gomes Júnior
authors.affiliation: Universidade Federal de Uberlândia, Instituto de Química, 38400-902, Uberlândia, MG, Brazil. Electronic address: tagowbn@gmail.com.
authors.forename: Waldomiro
authors.initials: W
authors.lastname: Borges Neto
authors.affiliation: Universidade Federal de Uberlândia, Instituto de Química, 38400-902, Uberlândia, MG, Brazil. Electronic address: aehmachado@gmail.com.
authors.forename: Antonio E H
authors.initials: AEH
authors.lastname: Machado
authors.affiliation: Agilent Technologies, Alameda Araguaia 1142, 06455-000, Barueri, SP, Brazil. Electronic address: daniela.daniel@gmail.com.
authors.forename: Daniela
authors.initials: D
authors.lastname: Daniel
authors.affiliation: Universidade Federal de Uberlândia, Instituto de Química, 38400-902, Uberlândia, MG, Brazil. Electronic address: alamtrovo@ufu.br.
authors.forename: Alam G
authors.initials: AG
authors.lastname: Trovó
mesh_terms: D002384:Catalysis; D006207:Half-Life; D007306:Insecticides / Q000737:chemistry; D012993:Solar Energy; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D007306:Insecticides; D014874:Water Pollutants, Chemical; D014025:Titanium
keywords: DFT; Insecticides; Response surface methodology; Solar radiation; Titanium dioxide; Vibrio fischeri