Abstract: CO2 mineralization is a promising method for the resource utilization of low-grade limestone and calcium-containing solid waste. Therein, adopting the acetic acid medium to achieve indirect mineral carbonation process to fixing CO2 is considered as an innovative and environmentally sustainable method owing to the reusability of the acetic acid medium. Nevertheless, the conversion efficiency of carbonation in this technique remains limited, with less than 20% efficiency at pressure of 5 MPa. Even with the addition of an extractant for acetic acid, the conversion efficiency of carbonation is still below 30%, significantly impeding the industrial applicability of this technology. In order to address the low conversion efficiency of carbonation in the acetic acid system, this study developed a new method for the preparation of calcium carbonate nanoparticles by microbubble-enhanced carbonation. The impacts of various factors such as medium calcium concentration, reaction temperature, reaction time, the value of pH, and aperture size of aerator on the efficiency of the carbonation reaction were systematically investigated. The results showed that: (1) Under optimal conditions (reaction time of 1 hour, reaction temperature of 80℃, initial pH of 7.2, initial calcium content of 70.07 g/L, and aperture size of aerator of 0.22 μm), the conversion rate of carbonation can reach 19.17% under atmospheric pressure, equivalent to the conversion rate achieved under 3 MPa. Meanwhile the regeneration cycle of the acetic acid medium can avoid wastewater generation at the source. (2) By integrating tributyl phosphate (TBP) with microbubble technology, the conversion efficiency of carbonation was improved to 57.5%, marking a 13.4 percentage point improvement over the reported pressurized extraction process. (3) At atmospheric pressure, rod-like aragonite nano-calcium carbonate products were synthesized with length of 400~800 nm and width less than 100 nm.

Key words: CO2, microbubble, calcium carbonate, extraction, nanomaterials

摘要： CO2矿化利用是低品位石灰石和含钙固废资源化利用的重要方向，以乙酸为介质的间接矿物碳酸化固定CO2工艺由于乙酸介质可循环，被认为是新一代的清洁工艺，但该工艺加压5 MPa下碳酸化反应转化效率不足20%，即使引入萃取剂后碳酸化反应转化效率仍不足30%，限制了其工业化应用。针对乙酸体系反应过程碳酸化反应转化效率低的问题，本研究开发了微气泡强化碳酸化法制备纳米碳酸钙新工艺，系统研究了介质钙含量、反应温度、反应时间、pH值、曝气头孔径等对碳酸化反应转化效率的影响。结果表明：(1) 最优工艺条件为：反应时间1 h，反应温度80℃，初始pH值7.2，初始钙含量70.07 g/L，曝气头尺寸0.22 μm，在常压条件下碳酸化反应转化效率可达19.17%，与加压3 MPa的转化效率相当，同时实现了乙酸介质的再生循环，源头上避免了废水产生。(2) 将有机溶剂磷酸三丁酯(TBP)与微气泡技术耦合，所得碳酸化反应转化效率达57.5%，比文献报道的加压萃取工艺提高了13.4个百分点。(3) 在常压条件下制得长度400~800 nm、宽度小于100 nm的棒状文石型纳米碳酸钙产品。

关键词: CO2, 微气泡, 碳酸钙, 萃取, 纳米材料