Ferrous‐Ferric Ratio and CEC Changes on Deferration of Weathered Micaceous Vermiculite

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Abstract
Ferrous iron in the layers increased 2‐fold or more on deferration of coarser fractions of micaceous vermiculite naturally weathered from biotite (Colorado and Transvaal sources). The ferric iron content of the layers was decreased by the deferration treatment but the original content was restored by subsequent H2O2 treatment. Sesquioxide coatings on micaceous vermiculite from Colorado, examined electron microscopically, were composed predominantly of Fe2O3 (80 to 85 percent), along with Al2O2 and SiO2. The CEC increased from 64 to 95 meq per 100 g in the fraction coarser than 1000 microns and 50 to 64 meq per 100 g in the fraction 2–0.2, microns in diameter, as a result of removal by deferration of positively charged sesquioxide coating which had originally blocked a portion of the CEC. Although treatment with H2O2 after deferration restored the Fe3+ content to approximately the original value, the CEC was not affected probably because of deprotonation OH− → O2− + H+ occurring simultaneous with Fe2+ → Fe3+.

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