title: Ultrasonic degradation of sulfadiazine in aqueous solutions.
abstract: Advanced oxidation methods, like ultrasound (US), are a promising technology for the degradation of emerging pollutants in water matrices, such as sulfonamide antibiotics. Nevertheless, few authors report the degradation of sulfonamides by high-frequency US (>100 kHz), and limited information exist concerning the use of ultrasonic-driven processes in the case of sulfadiazine (SDZ). In this study, SDZ degradation was investigated with the aim to evaluate the influence of initial concentration, pH and US frequency, and power. Ultrasonic frequencies of 580, 862, and 1,142 kHz at different power values and SDZ initial concentrations of 25, 50, and 70 mg L(-1) were used. The results show that SDZ degradation followed pseudo first-order reaction kinetics with k values and percent removals decreasing for increasing solute initial concentration. Higher SDZ percent removals and removal rates were observed for the lowest operating frequency (580 kHz), higher dissipated power, and in slightly acidic solution (pH 5.5). Addition of the radical scavenger n-butanol confirmed that hydroxyl radical-mediated reactions at the interface of the cavitation bubbles are the prevailing degradation mechanism, which is directly related to the pKa-dependent speciation of SDZ molecules. Finally, addition of H2O2 had a detrimental effect on SDZ degradation, whereas the addition of the Fenton reagent showed a positive effect, revealing to be a promising alternative for the removal of sulfadiazine.
authors.affiliation: Chemical Engineering Department, University of São Paulo, Avenida Prof. Luciano Gualberto, tr. 3, 380, São Paulo, Brazil, arlenlastre@gmail.com.
authors.forename: Arlen Mabel
authors.initials: AM
authors.lastname: Lastre-Acosta
authors.forename: Germán
authors.initials: G
authors.lastname: Cruz-González
authors.forename: Lauro
authors.initials: L
authors.lastname: Nuevas-Paz
authors.forename: Ulises Javier
authors.initials: UJ
authors.lastname: Jáuregui-Haza
authors.forename: Antonio Carlos Silva Costa
authors.initials: AC
authors.lastname: Teixeira
mesh_terms: D010084:Oxidation-Reduction; D013010:Sonication / Q000379:methods*; D013411:Sulfadiazine / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D013411:Sulfadiazine