Understanding the chemistry of direct aqueous carbonation with additives through geochemical modelling

Abstract

Amongst possible mineral carbonation strategies, direct aqueous mineral carbonation using organic salts is perhaps the most promising one. By going to and from between geochemical modelling and experimental results, this paper reviews key findings and conclusions to date about this process. With the magnesium silicate – oxalate system, the paper makes a strong case for the necessity to characterize both solid and liquid phases in order to analyze any aqueous mineral carbonation test results. It is shown that partial information about reaction products, such as liquid phase analysis without characterization of the associated solid phase, can easily lead to flawed conclusions. Proper analysis of solid products is recognized however to complicate experimental work considerably, with many analytical techniques being required to reveal the true nature of the solid phases present in aqueous mineral carbonation chemical systems. Given the complexity of such systems, geochemical equilibrium modelling is found to be an invaluable companion tool for planning and interpretation of experimental results. However, in contrast with the performance of geochemical simulation tools available today, such as the CHESS package used in this work, the lack of thermodynamic data necessary to simulate the behaviour of relevant chemical systems is a real issue that must be addressed.