IFLP   13074
INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Hyperfine and magnetic characterization of synthetic beidellite with different cation exchange capacity
Autor/es:
M.L. MONTES; M.A. TAYLOR; R.M.TORRES SÁNCHEZ; MERCADER, R.C.; BARRAQUÉ F; BRENDLE, J
Lugar:
Santiago de Chile
Reunión:
Congreso; XVI Latin American Conference on the Applications of the Mössbauer Effect; 2018
Resumen:
Magnetic nanomaterials are being developed to be used in a wide variety of applications, including catalysis, pollutant sorption, magnetic storage media, and drug delivery, among others. In practice, they are used as matrix materials for nanomaterials synthesis to decrease the particle aggregation and Fe oxidation.In the frame of producing this type of nanomaterials, two magnetic beidellites (BDL0.6Mag and BDL0.8Mag) based on beidellites Na+0.6 [Si4+3.4Al3+0.6)Al2O10(OH,F)2; BDL0.6, and Na+0.8 [Si4+3.2Al3+0.8)Al2O10(OH,F)2 ; BDL0.8, were synthetized.The beidellite samples syntheses were carried out in a hydrothermal reactor (220°C for 24 h), adding the corresponding concentrations of SiO2, Al2O3, NaF, HF and distilled water. BDL0.6Mag and BDL0.8Mag were synthetized in batch condition by alkaline oxidation of ferrous sulfate in the presence of BDL0.6 or BDL0.8.The two materials were characterized by Mössbauer spectroscopy and vibrating sample magnetometer. 57Fe Mössbauer spectra were obtained at room temperature using a conventional spectrometer in transmission geometry. The hysteresis loops were collected in a 2 T Lake Shore vibrating sample magnetometer.The fitting of the Mössbauer spectra yielded parameters belonging to two Fe3+ doublets, two Fe sites assigned to magnetite, a magnetic phase that could be assigned to goethite and a fourth magnetic site with hyperfine parameters around  = 0.7 mm/s,  = -0.05 mm/s and H = 40 T. A paramagnetic relaxation site was also needed to account for the spectra. From this characterization, it can be concluded that the permanent magnetism at room temperature of the systems arise principally from the magnetite existing in the samples. The magnetite relative spectral area was 61 ± 4 % for BDL06Mag and 48 ± 4 % for BDL08Mag. The saturation magnetization, Ms, resulted higher for BDL06Mag, 13.7 ± 0.5 Am2/kg, than for BDL0.8Mag, 11.1 ± 0.5 Am2/kg.The higher amount of magnetite and the higher Ms value obtained for BDL06Mag can be explained by the high cation exchange capacity value of the BDL08, which is able to sorb more Fe in its interlayer space, probably decreasing the available Fe to magnetite formation.The hyperfine and magnetic results reported here indicate that DBL0.6Mag can be manipulated easier than BDL0.8Mag, making DBL0.6Mag a more suitable material to be used, for example, as a sorbent material of hazardous pollutants.