Magnetic Activated-ATP@Fe3O4 Nanocomposite as an Efficient Fenton-Like Heterogeneous Catalyst for Degradation of Ethidium Bromide.

Magnetic attapulgite-Fe3O4 nanocomposites (ATP-Fe3O4) were prepared by coprecipitation of Fe3O4 on ATP. The composites were characterized by scanning electron microscopey, X-ray diffractometry, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, energy dispersive spectrometer and transmission electron microscopy. Surface characterization showed that Fe3O4 particles with an average size of approximately 15 nm were successfully embedded in matrix of ATP. The capacity of the Fe3O4-activated ATP (A-ATP@Fe3O4) composites for catalytic degradation of ethidium bromide (EtBr, 80 mg/L) at different pH values, hydrogen peroxide (H2O2) concentrations, temperatures, and catalyst dosages was investigated. EtBr degradation kinetics studies indicated that the pseudo-first-order kinetic constant was 2.445 min(-1) at T = 323 K and pH 2.0 with 30 mM H2O2, and 1.5 g/L of A-ATP@Fe3O4. Moreover, a regeneration study suggested that A-ATP@Fe3O4 maintained over 80% of its maximal EtBr degradation ability after five successive cycles. The effects of the iron concentrations and free radical scavengers on EtBr degradation were studied to reveal possible catalytic mechanisms of the A-ATP@Fe3O4 nanocomposites. Electron Paramagnetic Resonance revealed both hydroxyl (∙OH) and superoxide anion (∙O2(-)) radicals were involved in EtBr degradation. Radical scavenging experiment suggested EtBr degradation was mainly ascribed to ∙OH radicals, which was generated by reaction between Fe(2+) and H2O2 on the surface of A-ATP@Fe3O4.