title: Sonochemical degradation of ethyl paraben in environmental samples: Statistically important parameters determining kinetics, by-products and pathways.
abstract: The sonochemical degradation of ethyl paraben (EP), a representative of the parabens family, was investigated. Experiments were conducted at constant ultrasound frequency of 20 kHz and liquid bulk temperature of 30 °C in the following range of experimental conditions: EP concentration 250-1250 μg/L, ultrasound (US) density 20-60 W/L, reaction time up to 120 min, initial pH 3-8 and sodium persulfate 0-100mg/L, either in ultrapure water or secondary treated wastewater. A factorial design methodology was adopted to elucidate the statistically important effects and their interactions and a full empirical model comprising seventeen terms was originally developed. Omitting several terms of lower significance, a reduced model that can reliably simulate the process was finally proposed; this includes EP concentration, reaction time, power density and initial pH, as well as the interactions (EP concentration)×(US density), (EP concentration)×(pHo) and (EP concentration)×(time). Experiments at an increased EP concentration of 3.5mg/L were also performed to identify degradation by-products. LC-TOF-MS analysis revealed that EP sonochemical degradation occurs through dealkylation of the ethyl chain to form methyl paraben, while successive hydroxylation of the aromatic ring yields 4-hydroxybenzoic, 2,4-dihydroxybenzoic and 3,4-dihydroxybenzoic acids. By-products are less toxic to bacterium V. fischeri than the parent compound.
authors.affiliation: Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece.
authors.forename: Costas
authors.initials: C
authors.lastname: Papadopoulos
authors.affiliation: Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece.
authors.forename: Zacharias
authors.initials: Z
authors.lastname: Frontistis
authors.affiliation: Department of Environmental & Natural Resources Management, University of Patras, 2 Seferi St., GR-30100 Agrinio, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Antonopoulou
authors.affiliation: School of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania, Greece.
authors.forename: Danae
authors.initials: D
authors.lastname: Venieri
authors.affiliation: Department of Environmental & Natural Resources Management, University of Patras, 2 Seferi St., GR-30100 Agrinio, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Konstantinou
authors.affiliation: Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece. Electronic address: mantzavinos@chemeng.upatras.gr.
authors.forename: Dionissios
authors.initials: D
authors.lastname: Mantzavinos
keywords: Aqueous matrix; Estrogenicity; Factorial design; Intermediates; Micro-pollutants; Sonodegradation