Study of Mechanical Activation of Diopside in a CO2 Atmosphere

Interaction of natural diopside CaMgSi₂O₆ with CO₂ during mechanical activation in a CO₂ atmosphere has been studied. It has been shown that, depending on the kind of mechanical activator used, two types of CO₂ sorption by diopside are possible. If grinding is not accompanied by crystal structure disordering, the sorption of CO₂ on the diopside surface is similar to the sorption on metal oxides in the form of undistorted CO₃ ^2– groups, resulting in a nonsplit absorption band at 1430 cm^–1 in the infrared spectrum. If the mechanical activation of diopside leads to amorphization of the sample, it absorbs CO₂ in the form of distorted carbonate groups, which results in the appearance of a double carbonate band with maxima at 1433 and 1522 cm^–1 in the infrared spectrum of the ground sample. This band is similar to the one corresponding to CO₃ ^2– groups in the infrared spectra of carbonate-containing silicate glass. The carbonate content in the diopside sample reaches about 15% CO2 (or 35% CaCO₃) after mechanical activation in an AL-1000 activator in the CO₂ atmosphere for 580 min. X-ray diffraction, infrared spectroscopic data, carbonate content, and BET surface area measurements indicate that CO₂ molecules are likely to penetrate the structurally disordered diopside sample by a tribosorption mechanism. The results on the relaxation of the activated diopside sample during heating are presented.