Mechanochemical interaction of Ca silicate and aluminosilicate minerals with carbon dioxide

Processes induced by mechanical activation (MA) in a planetary ball mill of natural diopside CaMgSi2O6 and plagioclase (CaAl2Si2O8)(0.745) . (2NaAlSi(3)O(8))(0.209) . (2KAlSi(3)O(8))(0.046) in CO2 atmosphere have been studied. Plagioclase like diopside consumes CO2 during MA in the form of distorted carbonate groups resulting in appearance of the double IR absorption band in 1400-1600 cm(-1) region corresponding to the stretching vibrations of CO32- group. The degree of spitting of the double carbonate band for plagioclase is markedly higher than that for diopside indicating increased distortion of CO32- group in the mechanically activated plagioclase. According to the XRD data after 25 min of MA the diopside and plagioclase samples are almost totally amorphous. The carbonization degree of the plagioclase is lower than that of diopside after MA at the same conditions. The differences in the mechanically induced CO2 sorption ability by silicates can be explained on the basis of simple thermodynamic considerations involving standard Gibbs free energies of reactions of the crystalline minerals with carbon dioxide producing crystalline carbonates, silica and alumina. The results on thermal relaxation of the activated samples have been reported. (C) 2004 Kluwer Academic Publishers.