Dissolution kinetics of Amazonian metakaolin in nitric acid

• Main Authors: P. E. A. Lima, R. S. Angélica, R. F. Neves
• Format: Article
• Language: English
• Published: Associação Brasileira de Cerâmica
• Series: Cerâmica
• Subjects: kaolin; metakaolin; leaching; kinetic study
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0366-69132018000100086&lng=en&tlng=en

Abstract The kinetic study of Amazon metakaolin dissolution was performed with the application of the shrinking core model for spherical and ‘flat plate’ particles with constant size. The Amazon kaolin was calcinated at 700 ºC in order to produce metakaolin. This metakaolin was leached with 5% excess nitric acid at 70, 80 and 95±3 ºC for 3 h. Samples were collected every 15 min and subjected to aluminum analysis. The acid leaching was a chemically controlled process. The spherical morphology showed better fit than the flat plate particles when taking into account the regression coefficients. 91.58 kJ/mol of activation energy was found as well as an aluminum leaching reaction of the first order. The results found in this work using 5% excess acid and Amazon kaolin were consistent with previous research results using excess acid above 50% and standard kaolin.