Role of [FeOx(OH)y] surface sites on the adsorption of -lactamic antibiotics on Al2O3 supported Fe oxide

Abstract

In this work, [FeOx(OH)y]/Al2O3 composites with different Fe oxyhydroxy contents, i.e. 10, 20 and 50 wt% treated at 150, 200, 300 and 450 ◦C were investigated as adsorbents of -lactamic antibiotics, i.e. cephalexin, ceftriaxone and especially amoxicillin, from aqueous solutions. The obtained results showed thatthenature ofthe surface Fe3+ species play a fundamental role onthe adsorptionprocess. Themost effi- cient adsorption was obtained for the sample 150Fe50A (50% [FeOx(OH)y] supported in Al2O3 treated at 150 ◦C) whereas the thermaltreatment athigher temperatures caused a strong decrease onthe adsorption capacity. Mössbauer, XRD, FTIR, Raman, TG-MS, SEM, CHN and BET of the composite 150Fe50A suggested an approximate composition of FeO0.65(OH)1.7 whereas at 450 ◦C strong dehydroxylation process takes place to form FeO1.4(OH)0.21. These results combined with competitive adsorption using amoxicillin mixed with phosphate or H2O2 suggest that the antibiotic molecules adsorb by complexation on surface sites likely based on FeOx(OH)y by the replacement of the labile OH ligands.