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0~0.45 mm赤泥湿法碳化特性及储碳机理研究

Study on the wet carbonation characteristics and carbon sequestration mechanism of red mud within 0 mm to 0.45 mm

  • 摘要: 赤泥作为一种碱性固体废弃物,可通过碳化反应实现对CO2的矿化封存。为探究拜耳法赤泥在不同液固比、温度及CO2流量条件下的湿法碳化特性,得到各条件下赤泥的储碳性能。以碳化后赤泥的烧失量和pH变化量作为评价其储碳能力的指标,通过动力学拟合分析了不同变量对赤泥碳化改性的影响程度。利用XRD、FT-IR、N2吸附和SEM等手段,研究了赤泥碳化产物的演化规律,并探讨了赤泥的湿法碳化机理。结果表明,在液固比2.0∶1、CO2流量100 mL/min、反应温度30 ℃的最优条件下,赤泥储碳率可达5.68%,赤泥浆的pH值由9逐渐减小并稳定至6.45。动力学拟合结果显示,各变量对碳化改性效果的影响程度由大到小依次为液固比、CO2流量、温度。对碳化产物的表征分析表明,钙霞石与CaCO3含量增加,其原因在于碳化改性过程中赤泥中的水钙铝榴石和AlO(OH)参与碳化反应,溶出Ca2+、Na+和OH-;其中部分Ca2+与溶于水中的CO2反应生成CaCO3,其余Ca2+、Al3+、Na+作为离子源,生成了钙霞石。此外,碳化反应对赤泥中的碱性矿物的侵蚀,以及碳化产物的生成,使得碳化赤泥的比表面积较未碳化赤泥有所增大。

     

    Abstract: Red mud, as an alkaline solid waste, can achieve CO2 mineralization and storage through carbonation reactions.To investigate the wet carbonation characteristics of Bayer process red mud under the three factors of liquid-solid ratio, temperature, and CO2 flow rate, and to evaluate the carbon sequestration performance under various conditions, the loss on ignition and variation in pH value of the carbonated red mud were used as criteria to evaluate its carbon sequestration capacity.Kinetic fitting was applied to analyze the influence of different variables on the carbonation modification of red mud.The evolution patterns of carbonation products in red mud were investigated using techniques such as XRD, FT-IR, N 2 adsorption, and SEM, and the mechanism of wet carbonation in red mud was explored.The results show that under the optimal conditions of a liquid-solid ratio of 2.0∶1, a CO2 flow rate of 100 mL/min, and a reaction temperature of 30 ℃, the carbon sequestration rate of red mud can reach 5.68%, while the pH value of the red mud slurry gradually decreases from 9 and stabilizes at 6.45.Kinetic fitting results indicated that the degree of influence of variables on carbonation modification followed the order: liquid-solid ratio > CO2 flow rate > temperature.Characterization of carbonation products revealed an increase in the content of cancrinite and CaCO3.This is attributed to the participation of hydrogennet and AlO(OH) in the red mud during the carbonation modification process, releasing Ca2+, Na+, and OH-.Some Ca2+ reacted with CO2 dissolved in water to form CaCO3, while the remaining Ca2+, Al3+, and Na+ served as ion sources for the formation of cancrinite.Additionally, the carbonation reaction corrodes the alkaline minerals in red mud and generates carbonation products, resulting in an increased specific surface area of carbonated red mud compared to uncarbonated red mud.

     

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