Influence of the chemical composition and textural characteristics of palygorskite on the acid leaching of octahedral cations

Leaching of two palygorskites with different octahedral aluminium contents has been carried out in HCl at 20°–70°C. The acid concentration was varied in the range 0·05–6 mol. 1 −1 , using 4–500 g.g −1 liquid to solid ratios. Acid leaching of up to 60% of the octahedral cations did not provoke structural changes or amorphization of the samples. On the bases of the selectivity of extraction of Mg 2+ , Fe 3+ and Al 3+ , it appeared that most of the octahedral edge positions are occupied by Mg 2+ , some by Fe 3+ , and practically none by Al 3+ . Differences in acid-leaching behaviour between the two palygorskites was better related to accessible surface than chemical composition.