Síntese de mulita a partir de composições contendo caulim e resíduo do processo de obtenção da alumina.

Abstract

In recent years, many studies are being developed seeking to reuse waste, both in the composition of ceramic bodies as in the synthesis of minerals. In the process of obtaining alumina Bayer process a residue is generated during the calcination step, which has in its composition of 90% aluminum oxide. Due to the high content of this oxide, this material can be inserted as a source of Al203in ceramic formulations, especially those used in the synthesis of mullite. The mullite phase is a silica-alumina system (3AI2O32S1O2), which has been extensively studied because of their excellent properties, however, is a rare mineral and commercial production is based on reactive sintering precursor of silica and alumina. Thus, this paper presents a study aiming to obtain mullite from the waste generated in the process of obtaining alumina using conventional ovens and microwaves in the synthesis process. In conventional oven temperatures used were 1450, 1500 and 1550 ° C, heating rate 5 °C / min and level of burn 2 hours. Already in the synthesis microwaves were applied power of 1.4 and 1.6 kW for 10, 15 and 20 minutes. The powders were subjected to characterization by X-ray fluorescence, X-ray diffraction and scanning electron microscopy. The results showed that: kaolin and the residue from the aluminum industry can be used as precursors to obtain mullite, different heat treatments influence on the kinetics of crystallization, as the amount of oxides present in the compositions determined format and the composition of mullite crystals. For the synthesis conventional oven results showed that for all temperatures and compositions were formed mullite phase with increasing intensity of the peaks to higher temperatures. As for heating in microwave oven the mullite phase was only formed after 15 minutes of exposure.