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Cation Exchange Capacity and Weathering of Muscovite Macroflakes
Author(s) -
Mokma D. L.,
Syers J. K.,
Jackson M. L.
Publication year - 1970
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/sssaj1970.03615995003400010039x
Subject(s) - muscovite , chemistry , hydrolysis , cleavage (geology) , electron micrographs , mineralogy , weathering , analytical chemistry (journal) , nuclear chemistry , chromatography , geology , electron microscope , organic chemistry , paleontology , quartz , geotechnical engineering , geomorphology , fracture (geology) , optics , physics
The cation exchange capacity (CEC) of large (3‐ to 7‐cm 2 ) muscovite macroflakes, determined with 45 Ca, was 8.6 × 10 ‐7 meq/cm 2 of geometrical surface, a value greater than the theoretical one of 3.5 × 10 ‐7 meq/cm 2 calculated from the structural formula. The greater than theoretical CEC was attributed to exchange in areas of growth planes made accessible to the solution by (hkO) cleavage and by charged particle tracks. Similar values were obtained for BaEC (9.7 × 10 ‐7 meq/cm 2 ) and CsEC (8.7 × 10 ‐7 meq/cm 2 ). The excess of BaCl 2 , CsCl, or NaCl was not completely removed, whereas excess CaCl 2 was removed, by five 100% methanol washings, as indicated by radiochemical measurements. The presence of excess BaCl 2 and absence of CaCl 2 were confirmed by electron micrographs of platinum‐carbon replicas of the muscovite cleavage surfaces, the former being removed by subsequent water washings. Hydrolysis of exchangeable Na was appreciable during water washings in the NaEC determinations, resulting in a considerably lower measured NaEC (1.1 × 10 ‐7 meq/cm 2 ), but little hydrolysis of exchangeable Ba or Cs occurred in water washings. Electron micrographs showed that the muscovite (001) cleavage surfaces had been etched during extensive salt treatments and that a weathering product had formed on the surfaces. The latter material was insoluble in water, but was removed by treatment with Na citrate‐NaHCO 3 , indicating a sesquioxidic composition. The CEC of muscovite flakes was unaffected by the etching and the sesquioxidic weathering product.