Thermal analysis of ferrous sulphate heptahydrate in air

The oxidation of pyrite was studied by thermal analysis and quenching of the phases formed at different stages of the reaction. The phases were characterized by optical microscopy, SEM, EDAX, XRD and microprobe analyses. The phases found were essentially those predicted assuming thermodynamic and pressure equilibria. The predictions were that (1) below 404 ~ hematite would form directly on the pyrite surface whereas at higher temperatures magnetite would intervene, (2) pyrrhotite would become a stable phase above 552 ~ (3) ferrous and ferric sulphates would form in the outer layers at temperatures below 583 and 644 ~ respectively. The ignition temperature of pyrite was found to correspond with the onset of pyrrhotite formation. An arrest in some of the TG traces was ascribed to the presence of sulphates, the presence or absence of the arrest depending upon the temperature rise sustained by the sample during oxidation.There is general agreement [1 -13] that the final product of the oxidation of pyrite in air is ferric oxide, usually hematite. Kopp and Kerr [8] mentioned the possible formation of y-ferric oxide and Banerjee [2] has identified this material in X-ray diffraction (XRD) patterns. Agreement as to the intermediate phases is not unanimous. Pyrrhotite was claimed to be present, or hinted at as a possibility, by many workers (3 -5, 7-9, 11, 12, 14] but it was searched for by Banerjee [2J using XRD and chemical means and Schorr and Everhart [6] using XRD alone, and reported absent. Similarly, although magnetite was claimed to be present by several workers [4,5,8,9,11], Schwab and Philinis [13] could not detect it by XRD. Wustite has not been identified, though its presence was alluded to by Blachere [7] and there were mentions of its formation during the oxidation of pyrrhotite, [13,15]. Sulphate has been claimed to be present, either as the ferrous [2, 4,5,[16][17] or ferric forms [2,13], but Schorr and Everhart [6] using high-temperature XRD found no evidence of sulphates. Similarly Niwa and Wada [12], who also used XRD techniques, were unable to find evidence of sulphates. Banerjee [2], claims to have identified a small amount of basic sulphate by chemical means.There is a need, therefore, to examine the phases formed during the oxidation of pyrite to resolve some of the controversy noted above. This was accomplished in the present study by a) using sensitive thermal analysis techniques to provide information on weight changes and heat effects accompanying the oxidation, 16

Section: Reconciliation With the Phases Found In Practicementioning

confidence: 97%

Phases formed during the thermal analysis of pyrite in air

Jorgensen

Moyle

1982

“…Iron(II) sulphate heptahydrate was prepared and analysed as describea earlier [2]. Basic magnesium carbonate, of composition MgCO3.3Mg(OH)z, was prepared and analysed in the laboratory.…”

Section: Methodsmentioning

confidence: 99%

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of basic magnesium carbonate

Prasad

1987

Self Cite

Results on the thermal decomposition of iron(II) sulphate heptahydrate in the presence of basic magnesium carbonate are presented and discussed. These results are compared with those for the mixture of iron(II) sulphate heptahydrate with basic beryllium carbonate. While no reaction occurs between the components in the case of basic beryllium carbonate, basic magnesium carbonate reacts readily with iron(II) sulphate heptahydrate.In a previous communication [1], results on the thermal decomposition of iron(II) sulphate heptahydrate in the presence of basic beryllium cabonate were presented. It may be recalled that the components, iron(II) sulphate heptahydrate and basic beryllium carbonate, do not react at all under the dynamic oonditions studied, but undergo individual decompositions. Therefore, it was felt that it would be interesting to study the reaction of iron(II) sulphate heptahydrate with basic magnesium carbonate under the same conditions.

“…It is now well established that the basic sulphate, Fe(OH)SO4, is produced during the solid-state thermal decomposition of hydrates of iron(II) sulphate [2,3]. However, no attempt has been made till now, to study the hydrolysis of * Left the laboratory to settle in domestic life.…”

Section: Introductionmentioning

confidence: 99%

A new series of materials containing basic sulphates of iron(III)

Prasad

Mahapatra

1996

Self Cite

Series of basic sulphates which were precipitated by the hydrolysis of Fe(OH)SO4 in the presence and absence of metallic iron were studied from compositional, crystallographic and thermal decomposition points of view. The results are presented and discussed. It was found that high pure iron oxides as well as high grade red iron oxide pigments can be obtained by agitating the basic sulphates in hot ammonical medium followed by roasting. Commercial exploitation of the results is suggested.Keywords: application as high pure iron oxides and pigments, basic sulphates of iron(Ill), chemical composition, Fe(OH)SO4, hydrolysis, kinetics of decomposition, X-ray crystallography, washing of basic sulphates