Thermal treatment of lizardite for mineral carbonation using high flux radiation

• Novel heating method used for thermal activation of lizardite for CO 2 sequestration. • High-flux heating can improve Mg dissolution compared to conventional methods. • Sample that was heated rapidly to 530 °C for 480 s showed optimal results. • Promising heat activation conditions produced a highly amorphous, reactive structure. • Potential reduction in energy requirement and associated costs for heating. Heat treatment of lizardite with a high-flux radiant source to temperatures of up to 630 °C, at rates greater than 10 °C/s and exposure times up to 10 min, is reported for the first time in this study. The novel proposed radiant heat activation process was shown to enhance the subsequent carbonation potential when used as a precursor to dissolution experiments for magnesium extraction. It was found to increase magnesium carbonate yields by up to 58 % following dissolution in a saturated carbonic acid solution at room temperature for 2 h (i.e., exposed to carbon dioxide, CO 2 , at a partial pressure of 1 atm) compared to the same material heat treated in a rotary kiln. The magnesium extraction from the radiantly heat treated samples was found to: 1) increase monotonically with increasing heat treatment temperature up to 630 °C, 2) increase with increasing holding time at the set heat treatment temperature (up to 480 s), and 3) decrease with increasing heating rates (from 10 to 25 °C/s) for the same heat treatment temperature. Mineral analyses showed that the heat treated samples providing the greatest magnesium extraction had significant dehydroxylation of the crystalline lizardite. The results suggest that the phases formed during heating to moderate temperatures (530 < T < 630 °C) with relatively short exposure times (<10 min) are highly beneficial for magnesium extraction from the particles during dissolution in a carbonic acid solution, potentially improving the subsequent carbonation performance and the viability of using lizardite as the feedstock for long-term, chemically stable storage of carbon.