Effect of carbonic anhydrase-producing microorganisms on carbonation of steel slag powder under suspension process.

Addressing the needs of carbon dioxide capture and waste residue utilization, this study tackles the low reaction rate of existing steel slag carbonation under ambient temperature and pressure, investigating microorganisms' role in the process under suspended reaction conditions. Results show microorganisms significantly accelerate the carbonation rate: the time to reach 10% amount of carbon dioxide fixation is shortened to 1/5 of that of direct carbonation. Key influencing factors include steel slag powder moisture content, reaction humidity, and carbon dioxide concentration. After carbonation, the calcium-silicon phase mainly transforms. Compared with direct carbonation, microorganisms speed up carbon dioxide dissociation-diffusion in the liquid film on steel slag particles, enhance chemical reaction rate, promote carbonation of dicalcium silicate, and improve early-stage carbonation rate. The decrease of the diffusion rate of the product layer is the main rate-limiting step in the later carbon fixation reaction. This study provides process methods and data support for promoting microorganism-assisted steel slag carbonation technology.