Estudo de diferentes processos de troca de cátions em composições binárias de argilas bentoníticas.

Abstract

Boa Vista, in the state of Paraiba, is home to the third largest bentonite clays deposit of South America. Bentonite clays exploitation/industrialization began around forty years ago, and nowadays, due to the process of disorganized exploration, deposits of some types of clays are exhausted, some others are becoming exhausted and only two types of clays, Bofe and Verde-Lodo, still can be found in great amounts. However, these types of clays are regarded as low quality ones by local miners. Because of that, they are either used in less important applications or small portions of them are mixed to other more valuable clays to be used in oil well drilling fluids. So, the goal of this work is to study the influence of different processes of cations exchange in policationics bentonites found in the state Paraiba, in order to try to obtain sodium bentonites. Eight binary mixtures compositions with Bofe e Verde-lodo clays combined in various rates, which were obtained through experimental planning in simplex lattice, were studied. The cation exchange process was carried out using three distinct addition processes; in the first process, different types of clay were mixed and treated with a Na2C03 solution with different concentrations; in the second process, the distinct types of clay were treated individually, using the same concentration of Na2C03, finally in the third process, each type of clays was treated individually with different Na2C03 concentrations. After drying, dispersions were prepared and both apparent and plastic viscosity levels were measured with a Fann 35A viscosimeter. The results showed that the rheology properties of the studied dispersions are directly influenced by the methodology applied in cations exchange, as well as the viability of obtaining dispersions with reologic properties very close to Petrobras specifications, (1998).