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Heats of Immersion Studies on Anion‐Treated Ferric Oxide
Author(s) -
Jurinak J. J.,
Burau R. G.
Publication year - 1967
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1967.03615995003100060011x
Subject(s) - hematite , outgassing , molybdate , adsorption , chemistry , dissociation (chemistry) , inorganic chemistry , ion , isothermal microcalorimetry , endothermic process , ferric , oxide , standard enthalpy of formation , nuclear chemistry , analytical chemistry (journal) , enthalpy , mineralogy , thermodynamics , chromatography , organic chemistry , physics
Microcalorimetry was used to obtain heats of immersion data for αFe 2 O 3 (hematite) treated with SO 4 ‐2 , H 2 PO 4 ‐1 or MoO 4 ‐2 at pH 4.0. The data were compared with values from a reference OH saturated iron oxide. Using water adsorption data, the net integral heats of adsorption as functions of outgassing temperature (25 to 470C) were calculated. The energies of adhesion were also determined. Anion penetration lowered the surface energy of hematite, as manifested by a lowering of the immersional heats with increasing outgassing temperature. At pH 4.0 the relative bonding strengths of the anions on hematite were concluded to be MoO 4 ‐2 > H 2 PO 4 ‐1 > SO 4 ‐2 > OH ‐1 . The heat of immersion values after 25C outgassing indicated limited anion effect as well as a physical interaction of water with αFe 2 O 3 . The molybdate ion had the greatest effect on surface energy at all outgassing temperatures. The energy of rehydration (hydroxylation) of the αFe 2 O 3 surface was also calculated from the data.