Hydrolysis and Dehydration Reactions of Exchangeable Cu2+ on Hectorite1

M. B. McBride
Department of Agronomy, Cornell University, Ithaca, New York 14853
1 Contribution No. 1408.

Abstract: Electron spin resonance (ESR) analysis of Cu2+-hectorite suspensions provides evidence for the surface-induced hydrolysis of Cu(H2O)62+ at low pH and surface-inhibited hydrolysis (or precipitation) at high pH. Dehydration of the hectorite by heating to 110°C appears to promote hydrolysis in high pH clays further. Heating to even higher temperatures removes ligand water from Cu2+, allowing the metal ion to coordinate with silicate oxygen atoms. The planar Cu(H2O)42+ ion predominates in the interlamellar regions of hectorite that has been air dried or heated to temperatures of 110°C or lower, but more extreme thermal treatment changes the apparent orientation of the Cu2+-ligand axes as some or all of the four water ligands are removed, A loss in ESR signal intensity upon heating Cu2+-hectorite above 110°C is evidence for lowered symmetry of the dehydrated, surface-coordinated Cu2+ ion.

Key Words: Copper • Dehydration • Electron spin resonance • Hectorite • Hydrolysis • Water

Clays and Clay Minerals; June 1982 v. 30; no. 3; p. 200-206; DOI: 10.1346/CCMN.1982.0300306
© 1982, The Clay Minerals Society
Clay Minerals Society (www.clays.org)