Influence of Nano-Modification on Structural, Mechanical and Physico-Chemical Characteristics of Bentonite

Abstract

The paper studies the influence of nanodispersed aluminum and silicon oxides on the structural, physico-chemical and mechanical characteristics of calcium-magnesium bentonite deposits of the Republic of Tatarstan, in order to determine the optimal concentrations of the nanomodifier, and to improve the performance of respective materials. It was found that nanomodification of bentonite increases the strength of samples after firing by more than 1,5 times, the adsorption index by 20–25 %. The optimal concentration of nanoparticles was determined by changing the properties. The methods of Brunauer-Emmett-Teller (BET), x-ray phase analysis and infrared spectroscopy show an increase in the specific surface area, a change in the phase composition of the annealed samples, the intensity and position of the characteristic absorption bands, as well as the chemical bond silicon-oxygen in bentonite, modified by nanoparticles of aluminum and silicon oxides of similar nature.

Transformation of the structure and adsorption properties of bentonite during physical and chemical treatment

“…The low-frequency shift of the absorption peaks to 3385 cm -1 and 1631 cm -1 , which correspond to the stretching and bending vibrations of OH groups of water molecules with a simultaneous increase in their intensity, indicate an increase in hydrogen bonds in the bentonite structure. In addition, an increase in the polarity of the elementoxygen bonds, as previously shown in work [6], according to P. Rebinder's rule, additionally promotes the adsorption of polar MB molecules.…”

“…Its growth in modified compositions is due to an increase in dispersity and specific surface area up to 60-80 m 2 /g, to a greater extent, the surface of the faces, which is 2-3 times higher than the values of the base composition. At the same time, the number of uncompensated elementoxygen bonds on the faces of aluminosilicate minerals [6], which are adsorption centers, increases. Presumably, the following effect takes place: nanoparticles are adsorbed on the surface of bentonite minerals with the formation of structured complexes (boundary layers) in the form of a highly dispersed phase.…”

“…Stabilized hydrosols of aluminum oxide (AS) were used as modifiers -an aqueous dispersion of nanocrystalline boehmite with the general formula AlOOH and a crystallite size of 3.5-4 nm, pH = 4, and silicon oxide (SS) with an amorphous structure and a particle size of 6.0-10.5 nm, pH = 10 [6][7][8].…”

“…The most common methods for transforming the structure and properties of smectites in bentonite in the scientific literature include acid treatment [3,[9][10][11] and activation with sodium carbonate in suspension [12]. In addition to these methods, it was shown [6][7][8] that the modification of bentonite with nanodispersed hydrosols of aluminum and silicon oxides (3.5-10.5 nm) increases the adsorption index for methylene blue (MB) by 20-25%, respectively, the swelling capacity of the suspension and the ultimate strength for compression. In order to achieve higher adsorption properties of natural bentonite raw materials, in this work, we investigated the possibility of effectively combining nanomodification with physical (microwave and ultrasonic treatment) and chemical effects -acid treatment and activation with sodium salt.…”