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 beta-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 degrees C (150FeOH, 200FeOH, 300FeOH and 450FeOH, respectively). Mossbauer, 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 m(2) g(-1) with 46-59% mesopores, i.e., 0.04-0.09 cm(3) 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 beta-lactam antibiotics.