Practical mineralogical quantification of bentonites supported for a PXRD calibrated hkl model

Abstract

In the bentonite industry-exploration and beneficiation-ore quality control has been traditionally carried out using the swelling parameter, denominating those that swell as naturally sodium bentonites and those that do not as naturally non-sodium bentonites. However, the properties of the bentonites can vary due to the quantity and cationic type of montmorillonite. The variation in those properties cannot always be predicted, because there is still no consolidated and convenient method for clays mineralogical quantification. A quantification via PXRD using the Rietveld method is only reliable when all the crystalline structures of the mineral phases are known. This is not the case for bentonites, since the montmorillonite shows turbostratic disorder that leads to extremely wide and asymmetric non-basal reflections that are not considered in the available structural models. Thus, in this work, is generate a calibrated hkl model for a Brazilian montmorillonite applying the combined Rietveld-Le Bail-Internal Standard method developed by Paz et al. (2018). The study concluded that the combined method is a good choice for the mineralogical quantification of the bentonites, handling turbostratic disorder of montmorillonite, since the develop hkl phase model showed good results in mixtures with >50% montmorillonite content (greater precision and reproducibility).

Raw Smectite from the Guarapuava–Parana–Brasil Saturated with Copper Ions and Its Properties

“…The result of the composition analysis of each phase (Weight %) is shown in the pie chart (Figure 1a). The same profile of the diffractograms was characterized by bentonite clay as demonstrated in studies [33,34]. Geologically, formed mainly from the chemical alteration of volcanic glass and pyroclastic or volcanoclastic rocks, bentonite clay rocks are composed basically of Na-montmorillonite.…”

“…The result of the composition analysis of each phase (Weight %) is shown in the pie chart (Figure 1a). The same profile of the diffractograms was characterized by bentonite clay as demonstrated in studies [33,34].…”

Optimization of Pelleting Parameters for Producing Composite Pellets Using Zeolitic Material From Fly Ash

“…From Table 6, it is identi ed that both clays mainly contained silicon oxide (SiO 2 ) and aluminum oxide (Al 2 O 3 ), dominant constituents of all clay minerals. e relatively high percentage of Fe 2 O 3 (~10%) is typical for most Brazilian bentonites [35]. e Fe 2 O 3 and TiO 2 were the main impurities (1.2-1.3%) for kaolinite.…”

Insights into the Impact of Physicochemical and Microbiological Parameters on the Safety Performance of Deep Geological Repositories

“…High quality commercial bentonite typically consists of over 80% montmorillonite. However, this content varies significantly amongst different commercial bentonites, ranging from 60% to more than 80% [64]. During the canister deposition process, the bentonite buffer is composed of low-water-content (10-17%) bentonite blocks.…”

“…Therefore, a continuous evaluation of microbial activity and diversity in such a challenging environment is essential for the safety assessments of the DGR concept. In recent years, numerous studies have investigated the behavior of allochthonous bacteria in highly compacted bentonite (Figure 1), as well as the cultivation of microbes derived from the bentonite itself [6,64,74,75]. For instance, Jalique et al [76] identified Gram-positive spore-forming bacteria in highly compacted bentonite and inferred that the formation of spores might enhance bacterial survival in the challenging conditions of this environment.…”