Physical-chemical research of the sodium deactivation of brazilian bentonites

Bentonite is formed predominantly by montmorillonite. Generally, it is classified in two types: sodium and calcium. The sodium type has well swelling good thixotropic properties, which are applicable like drilling fluids, iron ore pelletizing, among others. The calcium type has't the same properties. The Brazilian deposits are predominantly calcium, therefore the biggest piece of national production is sodium activated with soda. Thereby, physical, chemical and rheological properties of no sodium bentonites are upgrade and can be used in industry. However, for some Brazilian bentonites activated types that upgrade last about 60 days. Therefore, there is a deactivation. Because that, deactivation was studied whereas its physical-chemical properties. Thus, four types of bentonites were studied: three from Paraíba state (known like calcium bentonites) and one from Maranhão state (magnesian). That bentonites were characterized by XRD, ICP and ETT. The deactivation was studied by swelling, both activated bentonites and after being washed. The results confirmed the predominant presence of montmorillonite in all samples. Both sodium activation and deactivation were confirmed, however, for deactivation in periods of less than 60 days; but this process was different way for them, each type showed the kinetics of deactivation pointed here as being a consequence of the different cationic proportions. (author)