The effects of impurities in carbide slag on the morphological evolution of CaCO 3 during carbonation

Carbide slag (CS) is a kind of solid waste generated by the hydrolysis of calcium carbide for acetylene production. Its major component is Ca(OH) , which shows great potential in CO mineralization to produce CaCO . However, the types of impurities in CS and their mechanisms for inducing the morphological evolution of CaCO are still unclear. In this work, the influence of impurities in CS on the morphology evolution of CaCO was investigated. The following impurities were identified in the CS: Al O , MgO, Fe O , SiO and CaCO . Ca(OH) was used to study the influence of impurities (Al O and Fe O ) on the evolution of CaCO morphology during CS carbonation. Calcite (CaCO ) was the carbonation product produced during CS carbonation under varying conditions. The morphology of calcite was changed from cubic to rod-shaped, with increasing solid-liquid ratios. Moreover, rod-shaped calcite was converted into irregular particles with increasing CO flow rate and stirring speed. Rod-shaped calcite (CaCO ) was formed by CS carbonation at a solid-liquid ratio of 10:100 under a stirring speed of 600 rpm and a CO flow rate of 200 ml/min; and spherical calcite was generated during Ca(OH) carbonation under the same conditions. Al O impurities had negligible effects on spherical CaCO during Ca(OH) carbonation. In contrast, rod-shaped CaCO was generated by adding 0.13 wt% Fe O particles, similar to the content of Fe O in CS. Rod-shaped calcite was converted into particulate calcite with increasing Fe O content. The surface wettability and surface negative charge of Fe O appeared to be responsible for the formation of rod-shaped CaCO . This study enhances our understanding and utilization of CS and CO reduction and the fabrication of high-value rod-shaped CaCO .