Iron Oxide Nanoparticles Supported on Mesoporous MCM-41 for Efficient Adsorption of Hazardous β-Lactamic Antibiotics
2018
Salviano, AdrianaBarbosa | Santos, MarianaRocha Dutra | de Araújo, LauraMaia | Ardisson, JoseDomingos | Lago, RochelMontero | Araujo, MariaHelena
In this work, the effect of crystallite size, defects, and surface area of iron oxyhydroxide particles supported on mesoporous MCM-41 on the adsorption of hazardous β-lactamic antibiotics was investigated. Different adsorbents were prepared by impregnation of 5, 10, 20, and 50 wt% of Fe followed by treatment at 150–400 °C. Mössbauer, XRD, BET, TG, FTIR, and Raman analyses suggested that treatment at 150 °C produced a mixture of α-Fe₂O₃, FeOOH, and highly dispersed Fe³⁺ species. At higher temperatures, different phases were gradually converted to hematite with crystallite sizes varying from 1 to 5 nm. Both, Fe content and temperature, strongly affected the amoxicillin, cephalexin, and ceftriaxone adsorption at pH 5, 7, and 9, with the best results obtained for the sample 20Fe150 (20% Fe treated at 150 °C), ca. 25 mgAMX g⁻¹ which decreased to 17, 6, and 4 mgAMX g⁻¹ (AMX = amoxicillin) upon treatment at higher temperatures. These results combined with competitive adsorption using AMX/phosphate and H₂O₂ decomposition experiments suggested that the antibiotic molecules are likely adsorbing by complexation on Fe³⁺ surface species of poorly crystallized small particles of Fe oxyhydroxide phases. It was observed that below a critical crystallite size of 3 nm, the AMX adsorption was very sensitive and strongly increased.
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