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This article in SSSAJ

  1. Vol. 26 No. 1, p. 33-36
    Received: Mar 8, 1961
    Accepted: May 31, 1961

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Aluminum Fixation in Montmorillonite1

  1. Mu Ju Shen and
  2. C. I. Rich2



Previous studies have indicated that Al is fixed by a synthetic cation exchanger as a positively-charged hydroxy-Al polymer with an OH/Al molar ratio of 2. The present study with montmorillonite showed that this mineral also can fix Al in nearly the same OH/Al ratio but at a lower pH.

Graded amounts of NaOH were added to an AlCl3-montmorillonite suspension and after 6 months the clay was separated. In the solution with the highest (1.35) OH/Al ratio, the apparent CEC of the clay had decreased from 98 to 20.5 me. per 100 g. and a 15.5 Å. X-ray diffraction spacing was retained at 500°C. This sample, however, expanded to 18 Å. with ethylene glycol at 25°C. The increase in fixed Al with decrease in CEC was 24.6 mg. per me.

Additional evidence is presented which indicates that the CEC was reduced by positively-charged hydroxy-Al groups occupying exchange sites rather than by Al(OH)3 blocking pathways to these sites.

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