Understanding the mechanism of CO2 mineralization and carbon sequestration performance in carbide slag: Effects of liquid-solid ratio and gas flow rate.

Emissions of CO2 and industrial solid waste are rising year by year, threatening human survival and development. Wet mineralization of alkaline solid waste is an effective method to mineralize CO2. To study the carbon sequestration performance and reaction characteristics of CO2 fixation by direct wet mineralization of carbide slag, based on a semi-closed reaction test setup. The CO2 mineralization efficiency of carbide slag was investigated under conditions of liquid-solid ratios of 5-20 mL/g and gas flow rates of 200-1100 mL/min. The surface coverage model was used to study the mineralization mechanism. The results show that the carbon sequestration performance of mineralized CO2 from carbide slag increases with the increase of liquid-solid ratio. With the increase in gas flow rate, the carbon sequestration capacity first increases and then decreases. The gas flow rate has a greater effect on the carbon sequestration performance of mineralized CO2 from carbide slag than the liquid-solid ratio. The highest mineralization efficiency of 69.13 % was achieved under the experimental conditions of a liquid-solid ratio of 5 mL/g and a gas flow rate of 500 mL/min. Based on the surface coverage model, the mineralization reaction mechanism can be understood as the reaction process occurring on the surface of CS, and the surface is continuously covered by the reaction product CaCO3, thus hindering the reaction. The results of this study can provide fundamental theoretical support for the technical application of accelerated mineralization of carbide slag to mineralize CO2.