Decomposição térmica (TG-DTA) de sais de ferro [FeCl3.6H2O] e [Fe(NO3)3.9H2O] com análise morfológica e química do produto final

Abstract

In this work was investigated the thermal behavior of iron salts (chloride and ferric nitrate) using the technique of simultaneous thermal analysis (TG-DTA). Thermal decomposition of the salts involves complex mechanisms such as dehydration, hydrolysis, evaporation, phase transitions that are possible to be accompanied by thermal analysis. Understanding the mechanisms involved and their temperatures are important to distinguish the structures of inorganic salts widely used as precursors of oxides and coordination compounds. Thermogravimetric curves indicate different thermal behavior, involving loss of initial mass (H₂O, endothermic process) for both. Differences in thermal behavior are observed in relation to ligands chloride and nitrate, as they do not coordinate with the same type of interaction with the central atom (ion Fe³⁺) to form the crystalline structure. Thus implying, in characteristic temperatures of decomposition, the output of chloride (207 ^oC) and nitrate (149 ^oC), with respective process deshidroxilação at 437 ^oC and 166 ^oC. Analyzing images of scanning electron microscopy with chemical analysis of residues of TG, we found that the final product has the same morphology and composition, estimating as possible formation of Fe₂O₃ in the form of hematite, due to not show magnetic property.