Rheological behavior of activated bentonite suspensions and estimation of flow models using least squares method

Abstract

In this study, bentonite samples were obtained from Wyoming-USA (WB), Eldivan-Çankırı (EB), Reşadiye-Tokat (RB), Niksar-Tokat (NB) and Ünye-Ordu (UB) regions. Then, these were evaluated in two main sections as raw and activated. Raw samples were obtained by reducing the samples obtained from the quarry to less than 75 μm particle size as a result of grinding and sieving processes. On the other hand, activated bentonites were obtained as a result of the activation process with 2.5%wt Na2CO3 and 0.5%wt MgO by dry activation method. After the sample preparation procedures, for the characterization X-ray fluorescence spectroscopy (XRF), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), brunauer-emmett-teller (BET) surface area and cation exchange capacity (CEC) analyzes were performed. With the suspensions prepared according to American Petroleum Institute (API) 13A standard with bentonite samples and shear stress measurements were performed at different shear rates. According to measured shear stress values, rheological evaluations with Bingham Plastic (BPM), Power Law (PLM), Casson (CM) and Robertson-Stiff (RSM) models were done by using least squared method (LSM) by MatLab. Also, results were validated statistically. When BPM was evaluated, it showed the R-EB coded suspension as the best with 0.9960 R2. R–NB for PLM was expressed as 0.9927 R2. For CM, the sample coded A-WB with 0.9975 R2 was best expressed. When the results were evaluated in general, it was determined that RSM expressed the shear stresses of the samples with higher accuracy compared to the others. Despite the high accuracy in all of the samples for RSM, the A-UB coded suspension stood out with 0.9987 R2.