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Changes in potassium exchangeability in heated lepidomelane
AbstractChanges in the K behavior of lepidomelane were induced by heating samples of the mica. These changes were related to concurrent alterations in the heated mineral to obtain information about the role of mineral properties in the exchangeability of interlayer K. The masking effects of small particles and fixable cations in the extractant were minimized by using 5–10 μm samples and NaClNaBPh4 extracting solutions, respectively. The mica samples were heated in a muffle furnace for different periods at several temperatures between 300° and 950°C before they were characterized in terms of their K release to the NaClNaBPh4 solutions. The effects of these thermal treatments on the Fe2+ content, d-spacing and weight of the mica samples were also recorded.The thermal treatments reduced the rate and degree of interlayer K exchange in the lepidomelane. Heat treatments at 300°C had relatively little effect, but the extraction of interlayer K required progressively longer periods when the temperature was increased incrementally to 950°C or the heating period at these higher temperatures was increased. Using the amounts of K extracted in 3 days as an index of the average rate of K release, a close relationship between the K release rate and Fe2+ oxidation in the heated mica was shown to exist. At the same time, however, reductions in the sample weight and basal spacing of the mineral occurred and were attributed to dehydroxylation in the heated mica. These changes in basal spacing probably had some effect on the rate with which all the K was released but had a more pronounced effect on the last 30% of interlayer K and finally made this part of the K nonexchangeable. The reduction in maximum extractable K indicates that a portion of the mica layers have a higher charge density. The processes of dehydroxylation and Fe2+ oxidation occurred independently in the heated mica and are reflected in the combined effects of basal spacing, layer charge and OH status of the mineral on interlayer K exchange.
Changes in potassium exchangeability in heated lepidomelane
AbstractChanges in the K behavior of lepidomelane were induced by heating samples of the mica. These changes were related to concurrent alterations in the heated mineral to obtain information about the role of mineral properties in the exchangeability of interlayer K. The masking effects of small particles and fixable cations in the extractant were minimized by using 5–10 μm samples and NaClNaBPh4 extracting solutions, respectively. The mica samples were heated in a muffle furnace for different periods at several temperatures between 300° and 950°C before they were characterized in terms of their K release to the NaClNaBPh4 solutions. The effects of these thermal treatments on the Fe2+ content, d-spacing and weight of the mica samples were also recorded.The thermal treatments reduced the rate and degree of interlayer K exchange in the lepidomelane. Heat treatments at 300°C had relatively little effect, but the extraction of interlayer K required progressively longer periods when the temperature was increased incrementally to 950°C or the heating period at these higher temperatures was increased. Using the amounts of K extracted in 3 days as an index of the average rate of K release, a close relationship between the K release rate and Fe2+ oxidation in the heated mica was shown to exist. At the same time, however, reductions in the sample weight and basal spacing of the mineral occurred and were attributed to dehydroxylation in the heated mica. These changes in basal spacing probably had some effect on the rate with which all the K was released but had a more pronounced effect on the last 30% of interlayer K and finally made this part of the K nonexchangeable. The reduction in maximum extractable K indicates that a portion of the mica layers have a higher charge density. The processes of dehydroxylation and Fe2+ oxidation occurred independently in the heated mica and are reflected in the combined effects of basal spacing, layer charge and OH status of the mineral on interlayer K exchange.
Changes in potassium exchangeability in heated lepidomelane
Kozak, L.M. (author) / Scott, A.D. (author)
Applied Clay Science ; 1 ; 29-42
1985-03-11
14 pages
Article (Journal)
Electronic Resource
English
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