Controlled Dehydration of Fe(OH)3 to Fe2O3: Developing Mesopores with Complexing Iron Species for the Adsorption of β-Lactam Antibiotics

In this work, efficient adsorbents for β-lactam antibiotics based on mesoporous iron oxide containing surface [FeOx(OH)y] sites were produced by controlled precipitation of iron hydroxide and thermal treatment at 150, 200, 300 and 450 ºC (150FeOH, 200FeOH, 300FeOH and 450FeOH, respectively). Mössbauer, X-ray diffraction (XRD), thermogravimetry-mass spectrometry (TG-MS), Fourier transform infrared spectroscopy (FTIR), Raman, Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM) and elemental analyses showed that the temperature caused a gradual dehydroxylation process with a significant increase of the mesoporous surface area (e.g., 114-142 m2 g-1 with 46-59% mesopores, i.e., 0.04-0.09 cm3 g-1) and approximate compositions of FeO1.06(OH)0.89 for 150FeOH up to FeO1.38(OH)0.26 for 450FeOH. The material 150FeOH showed high adsorption capacities of ca. 42 and 58 mg g-1 for amoxicillin and ceftriaxone, respectively. Experiments assessing the effect of NO3-, Cl-, competitive PO43- adsorption and H2O2 decomposition suggest that the [FeOx(OH)y] surface sites located in the mesopores are involved in the efficient adsorption by complexation of the β-lactam antibiotics.