Potencial dos depósitos de caulim halloysítico associados aos pegmatitos da região de Juiz de Fora visando o seu aproveitamento econômico.

Abstract

Brazil has 4.5% of the International reserves of kaolin, and studies in the last 50 years indicate occurrences in the regíon of Juiz de Fora. However there are no identifiable records of halloysitic clay deposits with quality to be used in the industry. Analyses and tests were done on sampling in the regíon to clarify if this material has industrial quality. The total mineral resources of halloysitic clay for the region of the Juiz de Fora are estimated to be about 7,0Mt. To obtain a fine fractíon with a particle size of less than 0.044 mm, the gravitatíonal hydraulic classifier (CHG) proved to be the most efficient process. X-ray diffractíon analysis indicates that after the CHG process is done, quartz peaks were eliminated in the fine fractíon and the halloysite peaks 7Å and 10Å were increased. Thermogravimetric, thermodifferential, X-ray fluorescence, and electron paramagnetic resonance analyzes were used as controls on the bleaching process. Halloysitic clay subjected to K+

adsorptíon and desorptíon tests compared to sodium bentonite demonstrated a concentratíon of 25-400 mg/L having a similar behavior. The most relevant results of this study showed the presence of halloysite in the natural clay, the efficiency in the beneficiatíon process with the removal of Fe3+ extra-structural, as well as the industrial applicatíons of halloysitic clay. In electron paramagnetic resonance (EPR) analyzes for samples 17(ME) and 13(BB), it presents spectra where the halloysitic clay has structural Fe3+ (at peaks in the range of 100-200 mT), which was not removed by the chemical bleaching. Adsorptíon and desorptíon tests of K+ in halloysitic clay minerals compared to sodium bentonite have shown that for a concentratíon between 25-400 mg/L it behaves analogously but at a lower rate. The fine fraction of halloysitic clay formulatíon provided results similar to the fraction containing sodium bentonite and perlite, but a lower value than the fraction containing kaolinite. When the loss of mass was evaluated, the feeder fraction of halloysitic clay gave the greatest mass loss.