Síntese e caracterização de hidróxidos e óxidos mistos de ferro e alumínio obtidos pelo processo sol-gel

Abstract

This study aimed to the synthesis and characterization of hydroxides and mixed oxides of iron and aluminum obtained under different pH conditions and proportions Fe: Al. The syntheses were carried out on a different methodology from those reported in the literature, based on the sol-gel process and the materials were characterized by XRD, FT-IR, SEM, and colorimetry. The XRD technique stood out crystalline phases for the mixed hydroxides, being evidenced the formation of the goethite (FeO (OH)) and boehmite (AlO (OH)) phases. The mixed oxides had a higher crystallinity degree than the pure oxides phases, and it was verified that the presence of the aluminum influenced some cases, in the structure of hematite phase, possibly containing some isomorphic sites replaced by aluminum. In FT-IR analysis for the hydroxides bands were observed characteristics of the sulfate group (SO4) 2-, in some samples these vibrations were more intense than the others, this fact is attributed to the washing process the material that was not sufficient to eliminate all residual sulfate. It was also observed characterized bands of M-OH bonds in all the samples. The effect of pH variation was identified by differences in the strength characteristics bands. After calcining the structure of the oxides was based on the structure of hematite of which the pH synthesis influence again, the intensity and the appearance of new bands of vibration. By SEM technique was observed that the particles formed exhibited different morphologies and pH influenced the size and agglomeration of these particles. In the case of colorimetric analysis, changes were observed in the parameters regarding the composition of both the hydroxides and for the oxides, and the pH caused major quantitative changes in color of the samples.