Water Retention by Colloidal Allophane and Imogolite with Different Charges

Jutaro Karube and Yukihiro Abe
Faculty of Agriculture, Ibaraki University, Ami-machi, Ibaraki-ken, 300-0332 Japan

Abstract: Water retention curves of colloidal allophane and imogolite with different charges and different pretreatments were measured using a tension plate and a pressure plate apparatus. An irreversible effect of air-drying was found for the water retention of colloidal allophane even for particles of less than 50 nm in Stokes' diameter collected from air-dried soil. This was attributed to the irreversible submicroscopic aggregation of allophane. Fresh allophane colloids with a low absolute net charge retained more water above −100 J Kg−1 than did highly charged ones due to the formation of a microporous structure. Allophane did not swell under ordinary conditions, but the relatively highly charged allophane recovered water retention above −100 J kg−1 during the wetting process. Imogolite retained 1.5 times more water than Na-montmorillonite at about −650 J kg−1 due to micropores formed by intertwining fibrous particles.

Key Words: Allophane • Imogolite • Net Charge • pH • Pressure Potential • Water Retention

Clays and Clay Minerals; June 1998 v. 46; no. 3; p. 322-329; DOI: 10.1346/CCMN.1998.0460311
© 1998, The Clay Minerals Society
Clay Minerals Society (www.clays.org)