title: Tolfenamic acid degradation by direct photolysis and the UV-ABC/H2O2process: factorial design, kinetics, identification of intermediates, and toxicity evaluation.
abstract: This study employed direct UV-ABC photolysis and the UV-ABC/H2O2process to investigate the degradation of tolfenamic acid (TA), a common anti-inflammatory drug used in both human and veterinary medicine. A 23factorial design with added center point was used to evaluate the effect of three independent variables-namely, H2O2concentration ([H2O2]), TA concentration ([TA]), and experiment time (time)-on TA degradation and H2O2photolysis during UV-ABC/H2O2treatment using a high-pressure mercury vapor lamp (photon flux of 2.6307 × 104J s-1) as the UV irradiation source. The responses yielded similar values, revealing a linear behavior, with correlation coefficients R = 0.9968 and Radj= 0.9921 for TA degradation and R = 0.9828 and Radj= 0.9570 for H2O2photolysis. The most efficient combination of variables was [H2O2] = 255 mg L-1and [TA] = 25 mg L-1, resulting in 100% TA degradation and 98.87% H2O2photolysis by 90 min of treatment. Additionally, the second-order kinetic constant of the reaction between TA and HO●was determined using a competitive kinetic model, employing 2,4-dichlorophenoxyacetic acid (2,4D) as the reference compound. The kinetic constant was 1.9 × 1010M-1s-1in alkaline medium. TA degradation by direct photolysis generated quinone imines as by-products, responsible for the formation of a dark red "internal filter" that increased the value of acute toxicity to Artemia salina. The UV-ABC/H2O2process did not promote formation of quinone imines by 90 min of treatment and therefore did not increase acute toxicity values. Several by-products generated during TA degradation were identified and possible degradation pathways for the UV-ABC and UV-ABC/H2O2processes were proposed.
authors: Institute of Chemistry, Federal University of Mato Grosso do Sul; Av. Senador Filinto Muller, 1555; CP 549; Campo Grande, MS 79074-460, Brazil.
authors: Lucas
authors: L
authors: de Melo da Silva
authors: Institute of Chemistry, Federal University of Mato Grosso do Sul; Av. Senador Filinto Muller, 1555; CP 549; Campo Grande, MS 79074-460, Brazil.
authors: Rodrigo
authors: R
authors: Pereira Cavalcante
authors: Institute of Chemistry, Federal University of Mato Grosso do Sul; Av. Senador Filinto Muller, 1555; CP 549; Campo Grande, MS 79074-460, Brazil.
authors: Rebeca
authors: R
authors: Fabbro Cunha
authors: Institute of Chemistry, Federal University of Mato Grosso do Sul; Av. Senador Filinto Muller, 1555; CP 549; Campo Grande, MS 79074-460, Brazil.
authors: Fábio
authors: F
authors: Gozzi
authors: School of Technology, University of Campinas; Rua Paschoal Marmo, 1888; Limeira, SP 13484-332, Brazil.
authors: Renato
authors: R
authors: Falcao Dantas
authors: Institute of Chemistry, Federal University of Mato Grosso do Sul; Av. Senador Filinto Muller, 1555; CP 549; Campo Grande, MS 79074-460, Brazil.
authors: Silvio Cesar
authors: SC
authors: de Oliveira
authors: Institute of Chemistry, Federal University of Mato Grosso do Sul; Av. Senador Filinto Muller, 1555; CP 549; Campo Grande, MS 79074-460, Brazil. Electronic address: machulekjr@gmail.com.
authors: Amilcar
authors: A
authors: Machulek
mesh_terms: D000818:Animals; D001156:Artemia / Q000187:drug effects / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007700:Kinetics; D007928:Lethal Dose 50; D008962:Models, Theoretical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010782:Photolysis; D012107:Research Design; D023382:Toxicity Tests, Acute; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D018508:Water Purification / Q000379:methods*; D062367:ortho-Aminobenzoates / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D062367:ortho-Aminobenzoates; C009500:tolfenamic acid; D006861:Hydrogen Peroxide
keywords: UV-ABC/H(2)O(2) process; acute toxicity; degradation pathways; direct photolysis; second-order kinetic constant; tolfenamic acid