Avaliação termocinética de processos de desidratação da fração caulinita contendo ferro isomórfico de argilas cauliníticas da Bacia Sedimentar do Araripe

Abstract

Red kaolinite (RK) with isomorphic iron originating from kaolinic clays from Campos Sales region located at Araripe basin, South of Ceará, Northeast Brasil, was obtained by sedimentation method according to Stokes's equation. The TGA analysis showed that the dehydroxylation process (dehydration) resulting from loss of coordinated hydroxyls groups on the replace of aluminium and iron presented an average activation energy(Ea) of 100 KJ/mol while onthe same process to white kaolinite ( without iron) the value was 92 KJ/mol. The TGA curves from red kaolinite showed the presence of FeO(OH) (goethite) at 350°C as well as the dehydroxylation of aluminium octahedron wich has changed to tetrahedral symmetry near 500°C. The TGA curve ofthe red kaolinite after treatment with oxalic acid did not show the event related to goethite showing a pure and less crystalline material.