The effects of impurities in carbide slag on the morphological evolution of CaCO3 during carbonation

• Published in: Journal of environmental management 2024-07, Vol.363, p.121361, Article 121361
• Main Authors: Pan, Zihe, Cao, Chunxia, Wang, Bo, Zhang, Fengjie, Chen, Lin, Zhao, Jianjun, Zhang, Zhien, Cheng, Huaigang
• Format: Article
• Language: English
• Subjects: CaCO3; Carbide slag; CO2 mineralization; Impurities; Self-assembly
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2024.121361

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)2, which shows great potential in CO2 mineralization to produce CaCO3. However, the types of impurities in CS and their mechanisms for inducing the morphological evolution of CaCO3 are still unclear. In this work, the influence of impurities in CS on the morphology evolution of CaCO3 was investigated. The following impurities were identified in the CS: Al2O3, MgO, Fe2O3, SiO2 and CaCO3. Ca(OH)2 was used to study the influence of impurities (Al2O3 and Fe2O3) on the evolution of CaCO3 morphology during CS carbonation. Calcite (CaCO3) 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 CO2 flow rate and stirring speed. Rod-shaped calcite (CaCO3) was formed by CS carbonation at a solid-liquid ratio of 10:100 under a stirring speed of 600 rpm and a CO2 flow rate of 200 ml/min; and spherical calcite was generated during Ca(OH)2 carbonation under the same conditions. Al2O3 impurities had negligible effects on spherical CaCO3 during Ca(OH)2 carbonation. In contrast, rod-shaped CaCO3 was generated by adding 0.13 wt% Fe2O3 particles, similar to the content of Fe2O3 in CS. Rod-shaped calcite was converted into particulate calcite with increasing Fe2O3 content. The surface wettability and surface negative charge of Fe2O3 appeared to be responsible for the formation of rod-shaped CaCO3. This study enhances our understanding and utilization of CS and CO2 reduction and the fabrication of high-value rod-shaped CaCO3. Synopsis: The effects of impurities on morphological evolution of CaCO3 during CO2 mineralization of carbide slag are still unclear. Here, Ca(OH)2 was selected as model mineral to explore the effects of impurities (Al2O3 and Fe2O3) on CaCO3 morphology evolution during CS carbonation. [Display omitted] •A typical rod-shaped calcite was prepared through CS carbonation.•The impurity of Al2O3 in CS cannot help form the rod-shaped calcite.•The impurity of Fe2O3 in CS induced the formation of rod-shaped calcite.•Hydrophilicity and negative surface charge of Fe2O3 help form rod-shaped calcite.