Phase evolution during accelerated CO2 mineralization of brucite under concentrated CO2 and simulated flue gas conditions

Abstract

Experimental work on the carbonation of brucite has been carried out in the temperature and pressure ranges of 50−120 °C and 1−10 bar respectively, using concentrated CO2 and simulated flue gas. At 120 °C hydromagnesite and trace amounts of magnesite were identified. Highly to semi-ordered dypingite like-phases and nesquehonite, coexisting with a possibly amorphous carbonate phase, were identified at 50 °C. The dehydration temperatures and chemical composition of these amorphous phases are very close to those of crystalline, stoichiometric nesquehonite. This probably amorphous phase nourishes the late formation of dypingite. This latter mineral gradually undergoes a cell shrinkage due to the partial loss of molecular waters, becoming structurally more ordered as the carbonation reaction proceeds. It remains unclear whether nesquehonite formed directly from brucite or from the crystallization of an amorphous precursor. However, nesquehonite is precursor of dypingite and/or the possibly amorphous phase. Only crystalline carbonate phases were observed at 120 °C. Concentrated CO2 experiments yielded the highest amounts (up to 37 wt.%) of CO2 sequestered at 10 bar and 16 h of reaction, reaching an almost complete carbonation of brucite (>98 %). On the other hand, flue gas experiments results showed higher amounts of CO2 sequestered per unit of CO2 partial pressure than with concentrated CO2.