Analysis of Hydrolysis Products of Iron(III) Salt Solutions by Means of MOssbauer Spectrometry and X-ray Diffractometory

Abstract

Hydrolysis products of iron (III) salt solutions of pH 1.5-1.8 were analyzed. It was found that α -Fe0OH precipitates in the presence of nitrate or bromide ions whereas β -Fe00H precipitates if the solution contains fluoride or chloride ions. NaFe₃(SO₄)₂(OH)₆ is obtained in the crystal form when the solution includes sulfate ions. Chemical state and crystal structure of the precipitates depend on the stability of Fe (III) complexes in the solution and on the concentration of anions. The contents of chlorine and bromine in the hydrolysis products were determined by means of thermal-neutron activation analysis. The γ -ray spectra were measured by a 1024 channel pulse height analyzer and a Ge (Li) detector. Atomic ratios, F/ Fe and Cl/Fe in β -Fe0OH, Br/Fe in α -Fe0OH, were found to be O.55, 0.15 and O.012, respectively. The desorption behaviours of chlorine from β -Fe00H and of bromine from cxF e0OH indicated that chlorine is included tightly whithin β -Fe00H crystal whereas bromine is adsorbed loosely on the surface of α -FeOOH crystal. The processes of iron(III) hydrolysis reactions in the various anions were also discussed from the standpoint of solution chemistry. MOssbauer spectra of β -Fe00H with fluolide ions and of α -Fe00H with chloride ions were taken at 78 K. The results indicated the slight difference in the internal magnetic field; 46.3 ± 0.3 T for the former and 47.2± 0.3 T for the latter.