The Effects of Iron Oxidation State on Clay Swelling,

Abstract

The effects of the state of iron oxidation in clay crystals on their swelling pressure and surface charge were investigated. The minerals studied were the < 2 micron, Na(+-) saturated fractions of API 25 Upton (UPM), Czechoslovakia 650 (CZM), and New Zealand (NZM) montmorillonites, and API H-33a Garfield nontronite (GAN). Methods and apparatus were developed to prepare reduced suspensions in a pH-buffered medium, as is to remove the undesired solutes and to prepare dried, oriented clay films while minimizing reoxidation of the ferrous iron in the mineral structure. In the composition range 0 < Fe(2+) < 0.4 mmol/g clay, the surface charge increased linearly with ferrous iron composition according to the charge deficits created by the reduction of Fe(3+) to Fe(2+). The swelling pressure decreased by 22%, 31%, 39%, and 56% for the respective clays, UPM, CZM, GAN, and NZM containing 1.5 g H2O/g clay. Above this range, the surface charge deviated from the predicted relationship and the swelling pressure was largely unchanged. Upon reoxidation these effects were reversible.

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Document Details

Document Type
Technical Report
Publication Date
Mar 07, 1983
Accession Number
ADA126543

Entities

People

  • Joseph W. Stucki

Organizations

  • University of Illinois Urbana–Champaign

Tags

Communities of Interest

  • Biomedical
  • Ground and Sea Platforms

DTIC Thesaurus Topics

  • Accuracy
  • Adsorption
  • Buffers (Chemistry)
  • Chemical Analysis
  • Chemical Synthesis
  • Chemistry
  • Classification
  • Controlled Atmospheres
  • Crystal Lattices
  • Crystal Structure
  • Measurement
  • Military Research
  • Photochemical Reactions
  • Phyllosilicates
  • Soil Science
  • Spectra
  • Spectroscopy

Readers

  • Agricultural Chemistry/Soil Science
  • Electrochemical Engineering/ Fuel Cell Technologies
  • Thin Film Deposition Science.