Aqueous mineral carbonation of Fe rich olivine by cation complexation using 2,2′-bipidine; concept validation and parameters optimization

Abstract

Mineral Carbonation can significantly reduce GHG emissions and it is one of the most promising methods to sequester postcombustion CO2 emissions. In this work, a novel pH-swing indirect mineral carbonation approach by cation complexation using 2,2′-bipyridine has been developed. A mining residue mainly composed of Fe (II)-rich olivine was used as a feedstock. The leaching of the mining residue was performed using NH4HSO4 as solvent (pH 2–3), at 61 °C with 250 rpm of stirring during 2 h of reaction time. A total of 28 and 41 wt% of iron and magnesium was leached respectively. Then, the iron leachate was stabilized as [Fe(bipy)3]2+ complex using 2,2′-bipyridine avoiding iron hydroxide precipitation when the solution pH is raised using NaOH. Finally, the mineral carbonation reaction was performed, using a CO2 gas stream into the solution at alkaline pH. Different parameters such as the temperature, the pH, the reaction time and the vol% CO2 gas injected were optimized in batch mode reactions. This innovative approach allows the use of mild temperature and pressure conditions to obtain iron carbonates. The best results shows that 50 wt% of the CO2 gas stream have been removed from the gas phase giving a ratio of 0.11 kg of CO2 sequestered per kg of residues, which represent an important improvement regarding past studies on Fayalite.