Ultrasonically assisted synthesis of CaCO3 whiskers from CO2 flue gas and steel slag leachate: A high-efficiency and valuable technique

Abstract

As the rubber industry thrives amidst global economic growth, enhancing rubber quality through superior fillers like CaCO₃ is becoming increasingly crucial. This innovative approach investigates the sustainable synthesis of CaCO₃ whiskers from steel slag, seeking to reduce reliance on natural resources while promoting environmental preservation. Leveraging a calcium-rich leachate obtained from steel slag through acetic acid leaching, CaCO₃ whiskers were synthesized under the influence of ultrasound and CO₂ captured in ammonia solution. The synthesis parameters including ultrasonic power, reaction time, initial reaction temperature, and the Ca^2 +/Mg²⁺ concentration ratio were systematically varied to optimize the morphology and purity of the CaCO₃ whiskers. Magnesium plays a critical role in this process, acting as a growth regulator by attaching to the most reactive surfaces of initial CaCO₃ crystals, thereby directing their transformation into high-aspect-ratio aragonite whiskers. This control mechanism was pivotal in achieving high-purity aragonite-type CaCO₃ with enhanced structural properties suitable as reinforcing fillers in rubber. The synthesized CaCO₃ whiskers, with an aspect ratio ranging from 20 to 150, achieved purities over 93.1 % and whiteness above 98.5 %. This method not only transforms steel slag and low-concentration CO₂ emissions into valuable resources but also plays a significant role in advancing CCUS (Carbon Capture, Utilization, and Storage) technologies within the steel industry, marking a significant step towards sustainable industrial practices and aligning with global sustainability goals.