The deposits of bentonite clays at Paraíba are the bigger and more important deposits of this type of mineral in Brazil. It is located in Boa Vista city and can be found in Lages, Bravo, Juá, and Canudos mines. These clays became well known because of their capacity of swelling in the presence of water, developing thixotropic gels after treatment with Na2CO3, as well as by their different colours. The aim of this work is to present a comparative study of the mineralogical composition and rheology of three bentonite clays namely Bofe, Chocolate and Verde-lodo, each one from two different mines of Boa Vista, PB. The clays were caracterizated by chemical analysis, differential thermal analysis and thermogravimetric analysis. The natural bentonite clays were transformed into sodium bentonite by addition of different concentrations of Na2CO3. The dispersions were prepared with 4.86wt% in order to measure their apparent and plastic viscosities by Fann 35A viscosimeter and water loss by pressing-filter. The results showed that the bentonite clays from different mines present similar colours and mineralogical composition, but their rheological properties became different after treatment with Na2CO3. This difference at this behavior allows to classify and to indicate the industrial application of each type of clay.
Bentonite clays; mineralogical composition; rheological properties
