Substitution by Iron in Kaolinite

Section: Methodssupporting

confidence: 86%

Section: The Nature Of the Iron Associated With Kaolinmentioning

confidence: 88%

See 1 more Smart Citation

Mössbauer Effect Studies of Iron in Kaolin. I. Structural Iron

Fysh

Cashion

Clark

1983

“…They observed quadrupole splittings as large as 0.75 mm/sec for kaolin from the bauxitic zone at Weipa, and, considering both X-ray powder diffraction analysis of these specimens and the variation in A values reported in the literature, concluded that this parameter may increase significantly with decreasing kaolinite crystallinity. The isomer shift and quadrupole splitting of the less intense doublet agree well with values reported for Fe 2+ in the kaolinite structure (Malden and Meads, 1967;Jefferson et al, 1975).…”

Section: K Spectrasupporting

confidence: 87%

Mössbauer Effect Studies of Iron in Kaolin. II. Surface Iron

Fysh

Cashion

Clark

1983

Abstract--57Fe M6ssbauer spectra have been used to interpret the effects of different cleaning processes on the iron mineralogy of a Weipa, Australia, kaolin. A magnetically separated fraction contained 28% of its iron as hematite likely of secondary origin. An initial centrifugal size separation was shown to give an improved final product, and oxalic acid was found to be more efficient at removing Fe from the kaolinite surface than dithionite bleach. The MSssbauer spectra clearly show that beneficiation steps which give a substantial increase in kaolin brightness result in only minor changes in the clay iron mineralogy. Similar results were also obtained for two commercially available kaolins.

“…Since soil kaolin generally occurs in a mixture of minerals, some of which contain iron, it is difficult to assign the iron to particular minerals on the basis of the above techniques. M6ssbauer spectroscopy has been successfully used to determine the presence of iron in kaolin in the absence of other iron-containing minerals (Malden and Meads, 1967;Fysh et aL, 1983;Murad and Wagner, 1991). It is therefore likely to prove of value in the investigation of forms of iron in purified soil kaolin especially since the signal produced is specific to the iron in a sample.…”

Section: Introductionmentioning

confidence: 99%

Mössbauer Spectra of Soil Kaolins from South-Western Australia

Pierre¹,

Singh

Webb

et al. 1992

Abstract--Six well-characterized soil kaolins from widely separated sites in south-western Australia and four reference kaolins were studied by 57Fe M6ssbauer spectroscopy at room temperature after removal of non-structurally-bound iron with dithionite-citrate-bicarbonate solution. The soil kaolins and one of the reference kaolins were also studied at temperatures near 16 K. The soil kaolins were remarkably similar in crystal size, crystaUinity, dehydroxylation temperature, cation exchange capacity, surface area and iron content. M6ssbauer spectra of the soft kaolins at room temperature were also essentially identical consisting of a quadrupole-split doublet superimposed on a broad component which indicated that all of the iron was present as Fe(III) and that slow paramagnetic relaxation effects were present. Mean values for the chemical isomer shift and quadrupole splitting of the doublet for the soil kaolins were 0.33 and 0.55 mm/s respectively which indicates that the iron is in the octahedral sites of the kaolin lattice. The spectra of the soil kaolin samples at temperatures near 16 K showed a further slowing down of the paramagnetic relaxation and confirmed that no discrete iron oxide minerals were present.M6ssbauer spectra of the four reference kaolins at room temperature showed a doublet component similar to those for the soil kaolins. Three of them showed evidence for other spectral components including, in two cases, a component due to the presence of Fe(II).