ALUMINUM REMOVED FROM SOLUTION BY MONTMORILLONITE

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Abstract
Experiments were made to investigate the effect of experimental conditions on the forms of Al adsorbed from solution by clays. It was found that when Ca(OH)2 was added to suspensions of clay in approximately 10−2 M solutions of AlCl3, the titration curves of the 2 N NaCl extracts of the clays showed one buffer zone between pH 4 and 5. If the Ca(OH)2 was mixed with the AlCl3 solution before adding the clay, the titration curves of the NaCl extracts showed, besides the normal buffer zone between pH 4 and 5, a second one near pH 6. Since the Al material that titrated near pH 6 was formed in the mixtures of Ca(OH)2 and AlCl3, removed from the dilute salt solutions by clay and released again to 2 N NaCl, it was assumed to be positively charged, exchangeable, polymeric Al ions. These polymeric ions were depolymerized and measured as monomers by the aluminon method. Heating the clay-AlCl3 suspensions, to which Ca(OH)2 had been added, to 100 °C also produced these exchangeable, polymeric Al ions but in this case they were not depolymerized and measured by the aluminon method.