Investigation of the acicular aragonite growth behavior in AOD stainless steel slag during slurry-phase carbonation

This study presents a novel method for producing acicular aragonite using argon oxygen decarburization (AOD) slag while controlling the reaction temperature, reaction time, stirring speed, and the magnesium-to‑calcium stoichiometric ratio. This approach provides steel plants with an opportunity to decrease their CO2 emissions and promote efficient resource utilization and CO2 storage through the production of high-quality value-added products. The experimental results showed that reaction temperature was the most significant factor affecting the carbonation efficiency of AOD slag, followed by reaction time, stirring speed, CO2 partial pressure, and the liquid-to-solid ratio (L/S). The study also found that elevated temperature and prolonged reaction duration favored the preferential precipitation of aragonite. Additionally, raising the temperature and the magnesium-to‑calcium stoichiometric ratio was shown to enhance the formation of aragonite, affecting its crystal growth orientation and dimensions. The optimal combination of reaction parameters for the preparation of acicular aragonite was found to be the reaction time of 8 h, the magnesium-to‑calcium stoichiometric ratio of 0.8, the reaction temperature of 120 °C, and the stirring speed of 200 r·min−1. Under these conditions, the resulting acicular aragonite exhibited excellent overall uniformity, a large aspect ratio, and a smooth crystal surface, with a content of 91.49 %, a single crystal length ranging from 9.86 to 32.6 μm, and a diameter ranging from 0.63 to 2.15 μm. This study provides valuable insights into the efficient production of acicular aragonite from steel slag while reducing CO2 emissions and promoting the sustainable use of resources. This study presents a novel method for producing acicular aragonite using AOD slag while controlling the reaction temperature, reaction time, stirring speed and the Mg/Ca stoichiometric ratio. Under the optimal combination conditions, the acicular aragonite CaCO3 prepared had a relative content of 91.49 %, the aspect ratio of the acicular aragonite ranged from 10.51 to 29.11, an average aspect ratio of 17.91. [Display omitted] •The maximum carbonation ratio of AOD slag by the slurry-phase carbonation route could exceed 86%.•Through slurry carbonation, two crystal forms of calcite and aragonite can be precipitated from AOD slag.•Higher temperatures and longer reaction times were conducive to the formation and growth of acicular aragonite.•Acicular aragonite