title: Magnetic iron species highly dispersed over silica: use as catalysts for removal of pollutants in water.
abstract: Fe2O3-SiO2composites were prepared by impregnation (sample FeIMP) or doping (sample FeDOP) in the structure of porous silica. The dye removal capacity of the materials was investigated through adsorption and oxidation studies of methylene blue and rhodamine B. N2adsorption/desorption measurements on FeIMP and FeDOP resulted in specific areas of 27 and 235 m2g-1, respectively. Mössbauer spectroscopy and XRD data detected hematite and maghemite as the iron phases in the samples FeIMP and FeDOP, respectively. Adsorption isotherms and kinetic studies of the dyes were better fitted in DKR model for FeDOP, where the process follows a pseudo-second order with the interparticle diffusion step being the rate-limiting step. On the other hand, FeIMP has better fit in the Langmuir model. Photocatalytic activity was observed in FeDOP under UV irradiation by the presence of reaction-hydroxylated intermediates for MB (m/z = 301) and RhB (m/z = 459). However, the photocatalytic activity was strongly influenced by the adsorption affinity between dye/catalyst. Photogenerated holes are the species responsible for the dye degradation when the adsorption is too strong, while hydroxyl radical action will be favored when the adsorption is not vigorous as detected by ESI-MS. Graphical Abstract Action of photogenerated holes and free electrons into the photocatalytically mechanism of methylene blue degradation over a semiconductor.
authors.affiliation: Department of Chemistry, UFMG, Av. Antônio Carlos, 6627-Pampulha, 31270-901, Belo Horizonte, Minas Gerais, Brazil. victoraugusto.freitas@gmail.com.
authors.forename: Victor A A
authors.initials: VAA
authors.lastname: Freitas
authors.affiliation: Department of Chemistry, UFMG, Av. Antônio Carlos, 6627-Pampulha, 31270-901, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Maia
authors.affiliation: Department of Physics, School of Mathematics, Physics, and Natural Sciences, UNSL, CONICET, Ejercito de Los Andes 950, San Luis, Argentina.
authors.forename: Rolando E
authors.initials: RE
authors.lastname: Belardinelli
authors.affiliation: CDTN, Av. Pres. Antônio Carlos, 6.627 - Campus UFMG, 31270-901, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Jose D
authors.initials: JD
authors.lastname: Ardisson
authors.affiliation: UFVJM, Institute of Science, Engineering, and Technology, Rua Cruzeiro, 1-Jardim São Paulo, 39803-371, Teófilo Otoni, Minas Gerais, Brazil.
authors.forename: Márcio C
authors.initials: MC
authors.lastname: Pereira
authors.affiliation: Department of Chemistry, UFMG, Av. Antônio Carlos, 6627-Pampulha, 31270-901, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Luiz C A
authors.initials: LCA
authors.lastname: Oliveira
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D059346:Magnets / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods*
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D012822:Silicon Dioxide
keywords: Adsorption; DKR; Iron oxide; Kinetic; Photocatalysis; Photogenerated species