DIFERENCIAÇÃO CATIÔNICA DE BENTONITAS POR INFRAVERMELHO: UM ESTUDO DOS EFEITOS DA HIDRATAÇÃO DOS CÁTIONS TROCÁVEIS

CATIONIC DIFFERENTIATION OF BENTONITES BY INFRARED: A STUDY OF THE HYDRATION EFFECTS OF EXCHANGEABLE CATIONS. In the bentonite industry, the most common procedure for quality control of the ore and the sodium activation process is the swelling method. However, this tool is restricted only to the differentiation of the sodium and non-sodium types, not considering the other cationic varieties. The objective of this study was to establish parameters for cationic differentiation of bentonites based on Near Infrared (NIR) and Medium (MIR) spectroscopy, which proved to be an effective technique in the cationic differentiation of bentonites using the characteristic bands “7072 cm-1” and “3620 and 3430 cm-1” under the condition of the dry-hydrated sample and not under the anhydrous condition. NIRS can be considered a measure of great scientific and technological contribution, as it allows the cationic differentiation of bentonites in a practical way and with low analytical cost.

Factorial design applied to sodium activation of a Brazilian bentonite

Sodium bentonites are extensively used in industry because they have specific properties that are wanted for several purposes, such as high swelling, thixotropy, and cation exchange capacity. Otherwise, calcium and polycationic bentonites, which are predominant in Brazil, need to be chemically treated by sodium activation to expand their content of interlayer exchangeable sodium cations, which increases these properties. The present study shows the factorial design of the sodium activation for a polycationic bentonite from Quatro Barras, Paraná. The factors considered in the study were: reagent (NaOH and Na2CO3), concentration (1% and 5%) and contact time (24 and 72 h). The response variables were swelling and cation exchange capacity. Statistical analysis indicated significant effects of all factors over swelling and response surface methodology indicated optimal activation with sodium carbonate at 5% for 24 h.

Thermochemical Upgrading of Calcium Bentonite for Drilling Fluid Applications

The rheological properties of bentonite suspensions depend on the chemical composition and the contained dominant element, such as calcium (Ca), potassium (K), and sodium (Na). Na-bentonite type is the one used in drilling fluids, because it has good dispersion stability, high swelling capacity, and outstanding rheological properties. Ca-bentonite generally has bad rheological performance; however, it can be activated by sodium to be used in drilling fluids, since there are huge unutilized Ca-bentonite resources. Many previous attempts of activation of Ca-bentonite were not feasible, upgrading required addition of many extra additives or sometimes mixed with commercial Na-bentonite to improve its properties. In this paper, a process of integrated beneficiation method is designed to efficiently remove the nonclay impurities and produce pure Ca-bentonite. An upgraded Ca-bentonite was produced using a combined thermochemical treatment in a wet process by adding 4 wt % of soda ash (Na2CO3) while heating and stirring. The new thermal treatment optimized and described in this study greatly improved the sodium activation and ions exchange process and improved bentonite properties. The thermochemically upgraded Ca-bentonite outperformed the rheological properties of the commercial bentonite. And when tested in a typical drilling fluid formulation at high temperature, the investigations showed an identical behavior of the commercial drilling grade bentonite. Moreover, the results obtained showed that the thermochemically upgraded Ca-bentonite has higher yield point/plastic viscosity (YP/PV) ratio than commercial Na-bentonite when mixed with the drilling fluid additives. Higher YP/PV ratio is expected to enhance the hole cleaning and prevent most of the drilling problems.

Moisture Diffusion in Natural Rubber/Bentonite Nanocomposites: Effect of Clay Filler Treatments

This study investigated the effects of clay filler treatments on moisture diffusion in natural rubber (NR)/bentonite nanocomposites. Four types of clay filler treatments were considered: sodium activation using sodium chloride (NaCl), ion exchange using hexadecyldimethylamine (HDA) chloride salt, modification using coco diethanolamide (CDEA), and wet grinding using ethanol as medium. A 24full factorial design of experiment (DOE) was utilized during clay filler treatments. The measured vulcanization characteristics of rubber specimens show the NR nanocomposites to be stiffer than unfilled NR, with very small differences in scorch and curing times. The moisture uptake of rubber specimens at 80°C is linear with square root of immersion time showing Fickian behavior. The rate of moisture uptake (slope of moisture uptake versus square root time) was measured. Determination of factor effects and analysis of variance show all clay filler treatments except for wet grinding significantly increase the rate of moisture uptake of NR nanocomposites. When compared to unfilled NR, only wet grinding of clay is found effective in lowering moisture diffusion.

Organophilization of a Brazilian Mg-montmorillonite without prior sodium activation

The use of Mg-montmorillonite in the production of organoclay without sodium activation was investigated. For this purpose, organophilization experiments were carried out by varying the concentration of two surfactants: hexadecyltrimethylammonium (HDTMA+) and dodecyltrimethylammonium (DTMA+) ions. These surfactantswere used at concentrations 0.7, 1.0 and 1.5 times that of the cation exchange capacity (62.6 meq/100 g) of the clay, with a reaction time of 8 h at temperatures of 25 and 80°C. X-ray diffraction (XRD) results confirmed the intercalation for bothin naturaand activated samples. The Fourier-transforminfrared (FTIR) spectroscopy and XRD results showed that the ratio ofgauche/transconformers decreased with increased basal spacing. The results of thermodifferential and thermogravimetric analysis (DTA/DTG) confirmed the thermal stability of the organoclay up to 200°C, permitting the use of suchmaterial in the synthesis of polymer/clay nanocomposites obtained by the melt blending. Thus, Mg-montmorillonite can be intercalated with alkylammonium ions without prior Na-activation to form organoclays. The possibility of using natural (non-activated) Mg-montmorillonite represents a significant difference in terms of processing cost in comparison with existing Ca-montmorillonite in Brazil or even with imported bentonites that require Na-activation during beneficiation.

Differential interaction of dicarboxylates with human sodium-dicarboxylate cotransporter 3 and organic anion transporters 1 and 3

Organic anions are taken up from the blood into proximal tubule cells by organic anion transporters 1 and 3 (OAT1 and OAT3) in exchange for dicarboxylates. The released dicarboxylates are recycled by the sodium dicarboxylate cotransporter 3 (NaDC3). In this study, we tested the substrate specificities of human NaDC3, OAT1, and OAT3 to identify those dicarboxylates for which the three cooperating transporters have common high affinities. All transporters were stably expressed in HEK293 cells, and extracellularly added dicarboxylates were used as inhibitors of [14C]succinate (NaDC3), p-[3H]aminohippurate (OAT1), or [3H]estrone-3-sulfate (OAT3) uptake. Human NaDC3 was stably expressed as proven by immunochemical methods and by sodium-dependent uptake of succinate ( K0.5 for sodium activation, 44.6 mM; Hill coefficient, 2.1; Km for succinate, 18 μM). NaDC3 was best inhibited by succinate (IC50 25.5 μM) and less by α-ketoglutarate (IC50 69.2 μM) and fumarate (IC50 95.2 μM). Dicarboxylates with longer carbon backbones (adipate, pimelate, suberate) had low or no affinity for NaDC3. OAT1 exhibited the highest affinity for glutarate, α-ketoglutarate, and adipate (IC50 between 3.3 and 6.2 μM), followed by pimelate (18.6 μM) and suberate (19.3 μM). The affinity of OAT1 to succinate and fumarate was low. OAT3 showed the same dicarboxylate selectivity with ∼13-fold higher IC50 values compared with OAT1. The data 1) reveal α-ketoglutarate as a common high-affinity substrate of NaDC3, OAT1, and OAT3 and 2) suggest potentially similar molecular structures of the binding sites in OAT1 and OAT3 for dicarboxylates.