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Published online by Cambridge University Press: 01 July 2024
The dissolution of two relatively pure Australian palygorskites in mild acid was studied. For both palygorskites, Si and Mg releases were linear with respect to added acid. The rate of Si release with acid addition is equal to 0.66 μmol Si for each μmol H+ added in both palygorskites. The corresponding releases of Mg were 1.2 μmol for the Al-poor and 0.47 μmol for the Al-rich minerals. Mg appears to be preferentially released into solution over Si, and both Mg and Fe appear to be preferentially released into solution over Al, suggesting a lower stability of Mg and Fe-rich palygorskites compared to Al-rich varieties. The free energy of formation of one of the palygorskites was estimated as equal to −1143.7 kcal/mol.