Investigação da formação de sodalita Bayer no processo de refinamento de alumina metalúrgica

Abstract

Gibbsitic bauxites with high reactive silica are abundant in the Amazon region. The processing of such ores is a challenge due to high costs mainly because of high NaOH consumption related do kaolinite dissolution and sodalite formation. Thus, the main purpose of this work was to investigate sodalite formation by using four different types of kaolinite-rich starting materials from Paragominas region (Pará state, northern Brazil). The NaOH concentration in the solution and reaction time (150 °C under autogenous pressure) were evaluated as the two main processes variables. The results show that higher NaOH concentrations and long reaction time favor a single sodalite phase formation. In the opposite conditions, another metastable sodalite phase is also observed. The confirmed presence of kaolinites with different order-disorder degrees, i.e. different kaolinite generations in the starting materials, help in the understanding on how to use such high reactive silica bauxites and the better physic-chemical conditions in the Bayer Process.