Óxido-Hidróxido de Ferro Nanoestruturado em Argilas Montmorilonitas

Abstract

Akaganeite is an iron oxyhydroxide commonly found in corrosion environments containing high levels of Cl-. In this project, akaganeite was synthesized by two methods: 1) precipitation in a basic medium, and 2) thermohydrolysis. The products were incorporated in inorganic matrices of bentonite clay. These phases were characterized by XRD, UV-Vis and FTIR spectroscopy and thermal analysis (TG). The XRD results show the existence of more than one phase of iron oxyhydroxide, especially for the material after interacting with the clay, and also show that the crystallinity of the materials differs according to the method of synthesis. The material obtained by thermohydrolysis is more crystalline. FTIR proves the existence of the akaganeite phase, but it is not possible to identify the other phases in the case of pure oxides, since the FTIR for the mixed materials is quite distinct from that of the pure oxides. The analysis by UV-Vis electronic spectroscopy also highlights these changes in phase due to the new processes that occur in the materials after the incorporation with clay. TG shows a greater loss of mass for the more crystalline material, while for the mixed materials the behavior is very similar, which indicates better thermal stability of the material after incorporation in the clay. The electrochemical process for both materials is basically the same, with minimal alterations for higher scanning rates for the material obtained by precipitation. These electrochemical processes are independent of the presence of O2. Studies of the degradation of dyes show that these mixed materials are promising catalysts in the Fenton process. The color of a solution disappears in a much shorter time than with many other materials cited in the literature. Qualitative tests of the mixed materials as glucose sensors show that they have good electrochemical responses to this organic molecule, and thus can be used as sensors.