Accelerated Direct Mineralization of CO₂ by Carbide Slag under Ambient Temperature and Pressure Reaction Conditions

Abstract

With the proposal of double carbon targets in several countries, Carbon Capture and Storage (CCS) technology for large-scale CO 2 sequestration is receiving increasing attention. Alkaline solid waste carbide slag is a cheap and adequate raw material for CCS. Based on the control steps of the mineralization reaction for CO 2 fixation by carbide slag, a stepwise enhanced strategy for wet mineralization sealing under normal reaction conditions was devised to efficiently improve CO 2 mineralization and byproduct CaCO 3 content. Specifically, we introduced calcination to change the surface morphology of the carbide slag and then utilized agitation to improve the solid−liquid consistency and enhance the dissolution of the carbide slag and the leaching of Ca 2+ . Ultrasound and magnetic stirring cause the carbide slurry to vibrate, shock, and disperse violently so that the calciumcontaining phase releases more Ca 2+ into the reaction system and promotes CO 2 mineralization. However, it is possible that ultrasonic waves to some extent destroyed the CaCO 3 released from the carbide slag to form an encapsulating layer on the surface, allowing more Ca 2+ reactions and better performance of CO 2 capture and CO 2 mineralization efficiency under ultrasonic conditions. The addition of NaOH solution affected the generation of carbonate and the mineralization reaction, which resulted in a CO 2 mineralization efficiency of 86.7% (637 kg CO 2 /tonne of slag), a calcium mineralization product with a purity of 94.1%, and a particle size of about 100 μm under the conditions of 300 W, 25 °C, and 1 M concentration. This technology progressively enhances the process of fixing CO 2 by wetting the carbide slag with the byproduct of CaCO 3 .