Thermal dehydration and decomposition of FeCl3·xH2O

Abstract

Thermal dehydration and decomposition characteristics of Fe(III) chloride hydrate have been studied by both isothermal and non-isothermal methods. After the initial melting at 35–40°C both dehydration and decomposition of the salt proceed simultaneously at temperature above 100°C. At 250–300°C a stable hydrated Fe(OH)2Cl is formed representing the first plateau region in the TG curve. Around 400°C, a second plateau is observed corresponding to the formation of mostly Fe2O3 which however retains some OH groups and Cl− ions. However, these temperature ranges vary with the TA equipments used. Chemical analysis of the products of decomposition at temperatures above 140°C also gives evidence for the formation of FeOCl which on hydrolysis in water gives FeCl3 in solution. The FT-IR spectra suggest the presence of structural OH groups even for samples calcined at 300–400°C. The XRD patterns of the products of decomposition in the temperature range 160–400°C indicate the presence of β-FeOOH, some unidentified basic chlorides and α-Fe2O3.