Re-examination of the kinetics of the thermal dehydroxylation of goethite

The kinetics of thermal dehydroxylation of aluminuous goethites [1] synthes ised from a ferrous salt has been re-examined using the general reaction or der kinetic law. The utilised data processing was based on the procedures e mployed by dissolution kinetics. Recalculation of the activation energies E -A of the dehydroxylation yielded the values 130, 132, 128, and 123 kJ mol( -1) for pure goethite, goethite with 10, 20, and 30 mol% Al substitution, r espectively. The values of E-A are in a good agreement with those given for goethite in literature. The E-A values are linearly related with the chemi cally bound excess H2O/OH- in the crystal lattice that is apparently influe nced by Al substitution.