Indirect mineralization of CO2 using recyclable glycine with carbide slag

The indirect mineralization of CO2 by industrial solid waste is an essential process for CO2 immobilization; however, many technical challenges remain to be overcome. In this study, carbide slag (CS), a type of industrial solid waste, was used as a raw material for the indirect mineralization of CO2 using glycine. In the extraction stage, the ion extraction efficiency of Ca significantly increased to 68.5% due to the formation of a chelate between glycine and Ca, which enhanced Ca dissolution. Analysis of the mineralization process revealed that glycine was recycled after absorbing CO2, leading to increased CO2 absorption capacity because of the high alkalinity of the extract solution. Furthermore, there was a synergistic effect between CO2 absorption and the Ca precipitation reaction. This synergistic effect increased the reaction rate of mineralization and enhanced its efficiency. As a result, the Ca precipitation reaction was largely complete within 5 min, and the mineralization efficiency was enhanced to 93%. Furthermore, the recirculation (indirect mineralization) results showed that the Ca extraction and mineralization efficiencies remained constant during each cycle. Most importantly, glycine could be regenerated automatically during the cycle, which proved that the cyclic indirect mineralization process could operate stably.