Influence of Ca2+ in the rheological properties and filtration of bentonitic clay dispersions in aqueous drilling fluids

Abstract

The smectic clays are materials consisting of one or more clayey smectite and some accessory minerals. The clay minerals are the main solid constituents of cohesive soils, dispersed sediments and some fine-grained rocks, being one of the most important mineral resources used in many industrial and domestic applications. The smectite sand-minerals are aluminosilicates of sodium, calcium, magnesium, iron, potassium and lithium, which include: montmorillonite, nontronite, saponite, hectorite, sauconite, beidellite and volkonskoite. The montmorillonite is the predominant clay in the bentonite clays, having a layered structure, being an octahedral layer of aluminum hydroxide [Al(OH)3] between two tetrahedral layers of silica (SiO2). Their hexagonal plates carry a negative surface charge due to the isomorphic substitution in Al3+ metal centers in the layers by lower valence metal ions, such as Fe2+ and Mg2+, and is widely surrounded by exchangeable cations such as Na+, H+, K+ and Ca2+, balancing the responsible network. In this sense, smectic clays can vary greatly in relation to their physical, chemical and mineralogical composition, where this variation depends on their geological formation, which can greatly compromise their industrial application [1-5]. The search for new occurrences of bentonite clays in the State of Paraíba, Brazil, has become more and more important since, due to the disordered extraction of the bentonite clays in this State, the clays of the best mineralogical compositions have been depleted [4, 6]. Mineral accessories (mainly quartz, cristobalite, mica, calcite, dolomite and feldspars) compromise the technological applications of bentonite clays, mainly their rheological properties that are greatly found in clays commercialized today, which makes Influence of Ca2+ in the rheological properties and filtration of bentonitic clay dispersions in aqueous drilling fluids