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

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 H 2 O 2 treatment. Sesquioxide coatings on micaceous vermiculite from Colorado, examined electron microscopically, were composed predominantly of Fe 2 O 3 (80 to 85 percent), along with Al 2 O 2 and SiO 2 . 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 H 2 O 2 after deferration restored the Fe 3+ content to approximately the original value, the CEC was not affected probably because of deprotonation OH − → O 2− + H + occurring simultaneous with Fe 2+ → Fe 3+ .