Accelerated Direct Mineralization of CO<sub>2</sub> by Carbide Slag under Ambient Temperature and Pressure Reaction Conditions
Hongpeng Lu, Wan Wang, Jianjun Zhang, Mingkun Wu, Yang Deng, Guidong Li, Mengkui Tian
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 calcium-containing 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 .