Synthesis of high-value CaCO3 via indirect CO2 fixation utilized blast furnace slag

Abstract

Ultrasonic and bubbling carbonation method achieved precipitation of CaCO3 was described as a particularly advantageous method for synthesizing low-dispersity vaterite CaCO3. Herein, high-purity vaterite CaCO3 microspheres with regular morphology was synthesized from blast furnace slag (BFS) through mineral phase leaching, precipitation impurity removal, and CO2 solidification in ultrasonic reaction field. The results demonstrated that the method employed for distributing bubbling CO2 under an ultrasonic field aided both CO2 fixation and indeed the formation of homogenized vaterite. And vaterite synthesis is further aided by factors such as low initial calcium ion concentration, low reaction temperature, high CO2 concentration, and short aging time. Furthermore, a sphere-dumbbell-sphere mechanism has been proposed as a possible growth mechanism for the spheroidal structures. Finally, large-scale production of high value-added vaterite CaCO3 would eventually be attained at carbonation temperature of 20 ℃, Ca2+ concentration of 0.1 mol·L−1, CO2 proportion in the gas mixture of 70 %.