Extraction of magnesium from four Finnish magnesium silicate rocks for CO2 mineralisation - Part 1: Thermal solid/solid extraction

The only option for carbon capture and storage (CCS) in Finland is mineral carbonation, which has been extensively researched at Åbo Akademi University (ÅA). Finding suitable minerals for mineral carbonation in different regions of Finland will keep transportation of either CO₂ or the actual mineral at a lowest possible level. Four different rocks from different regions in Finland have been compared with respect to composition and possibility to extract magnesium. This paper presents experiments applying thermal solid/solid extraction. It was found that a mixture of ammonium sulphate (AS) and ammonium bisulphate (ABS) could extract a significant part of magnesium compared to tests using only AS or ABS. Serpentinite rock is also the best option for magnesium extraction while diopside and magnesiohornblende are much less reactive. Continuous mixing during the experiment in a rotary tube and adding some water to the solid/solid mixture gives better extraction results. The binding capacities of CO₂ in the serpetinites with respect to the magnesium extractions achieved in this study are 240 kg CO₂/ton rock (Serp-A) and 207 kg CO₂/ton rock (Serp-B).