Synergistic catalytic degradation of antibiotic sulfamethazine in a heterogeneous sonophotolytic goethite/oxalate Fenton-like system

A novel heterogeneous sonophotolytic goethite/oxalate Fenton-like (SP-FL) system was developed in this study. Compared to the corresponding photochemical Fenton-like (P-FL) system and sonochemical Fenton-like system (S-FL) system, it was found that the SP-FL system could achieve synergistic degradation of antibiotic sulfamethazine (SMZ). A synergy factor of 2.2 based on pseudo-first-order degradation rate constant (k(obs)) was observed, along with great improvements in organic mineralization and waste-water detoxification. Examining the evolution of dissolved iron species and reactive oxygen species (H2O2 and center dot OH) in the three systems revealed that the SMZ degradation strongly relied on the "in-situ" photochemical generation of H2O2 and fast regeneration of dissolved Fe(II) species. Identification of the organic intermediates and released inorganic ions suggested that the cleavage of S-N bond in the SMZ molecule was dominant under center dot OH attacking. The important synergistic role of ultrasound (US) in promoting SMZ degradation was proposed. Herein US could affect the system at multi-folds: (1) accelerating the goethite-chelating dissolution by reducing mass transfer barriers, (2) enhancing the radical reactions in the bulk solution with sonochemical cavitation effect, and (3) possible direct hydrolysis of amine intermediates inside the cavitation bubbles. (C) 2013 Elsevier B.V. All rights reserved.