Enhanced Fenton-like degradation of pharmaceuticals over framework copper species in copper-doped mesoporous silica microspheres.

Copper-doped mesoporous silica microspheres (Cu-MSMs) with the coexistence of Cu(I) and Cu(II) were prepared using a hydrothermal process and characterized by several methods. The characterization studies suggested that 0.91 wt% of the copper species could exist in the framework of the mesoporous silica microspheres by chemical binding of Si O Cu; excess copper species were located in the extraframework sites, leading to more oxygen vacancies on the surface of the catalysts. The framework Cu of Cu-MSMs was found to be highly effective and stable for the degradation of pharmaceutical pollutants, as demonstrated with phenytoin, ibuprofen and diphenhydramine in the presence of H 2 O 2 at neutral pH values. The conversion of the three pharmaceuticals could reach 100% within 75, 120 and 90 min, respectively; the leaching of Cu was much lower than the EU directives and USA regulations. By the studies of electron spin resonance, gas chromatography–mass spectrometry, Fourier-transform infrared spectra, in situ Raman spectra and X-ray photoelectron spectroscopy, an interaction process among the framework Cu of Cu-MSMs, pharmaceuticals and H 2 O 2 was proposed: During the Fenton-like reaction, the framework Cu(I) in Cu-MSMs primarily converted H 2 O 2 into OH, and Cu(I) was oxidized to Cu(II) by H 2 O 2 . The pharmaceuticals were attacked by OH to form phenolic intermediates, adsorbing on the surface of Cu-MSMs, complexing with the framework Cu(II), forming Cu-ligands. Cu-ligands interacted with H 2 O 2 and enhanced the reduction rate of Cu(II), resulting in the more Cu(I) production; consequently, accelerated the Cu(II)/Cu(I) cycles on the catalyst surface, leading to more OH generation for the pharmaceuticals oxidation. [ABSTRACT FROM AUTHOR]