Cu2+-Adsorption Characteristics of Aluminum Hydroxide and Oxyhydroxides1

M. B. McBride
Department of Agronomy, Cornell University, Ithaca, New York 14853
1 Agronomy paper No. 1399.

Abstract: The nature of Cu2+ adsorption by boehmite, gibbsite, and noncrystalline alumina was studied over a range of equilibrium pH (4.5–7.5) and Cu2+ concentration (10−3–10−8 M) by electron spin resonance (ESR). Available chemisorption sites at pH 4.5 were the most numerous for noncrystalline alumina (∼1 mmole/100 g), less for boehmite, and least for gibbsite as indicated by the relative strength of the rigid-limit ESR signal attributed to Cu2+ adsorbed at discrete sites. The chemisorption process involved immobilization of Cu2+ by displacement of one or more H2O ligands by hydroxyl or surface oxygen ions, with the formation of at least one Cu-O-Al bond. As the pH was raised from 4.5 to 6.0, essentially all of the solution Cu2+ appeared to be adsorbed by the solids. However, the noncrystalline alumina and boehmite chemisorbed much of the total adsorbed Cu2+ (10 mmole/100 g), whereas precipitation or nucleation of Cu(OH)2 in the gibbsite system was indicated. Precipitated Cu2+ was more readily redissolved by exposure to NH3 vapor than chemisorbed Cu2+.

Key words: Adsorption • Alumina • Aluminum • Boehmite • Copper • Electron spin resonance • Gibbsite

Clays and Clay Minerals; February 1982 v. 30; no. 1; p. 21-28; DOI: 10.1346/CCMN.1982.0300103
© 1982, The Clay Minerals Society
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