Efficient leaching and indirect carbonation of Ca from AOD stainless steel slag
The Ca content in steel slag is relatively high.Utilizing steel slag as a substitute for natural ore as a Ca source for carbonation reactions to sequester CO2 is a promising method for both solid waste utilization and carbon reduction.The use of indirect wet carbonation not only significantly improves carbon fixation efficiency but also enables the production of high-purity,high-value-added calcium carbonate products.In this study,AOD stainless steel slag(AOD slag)was chosen as the material.Firstly,chemical analysis and mineralogical analysis were con-ducted to confirm its high carbon fixation potential.Subsequently,based on the indirect wet method to accelerate the carbonation process,the efficient leaching behavior of Ca from AOD slag was investigated.Orthogonal experiments and single-factor experiments were employed to explore the effects of leaching temperature,hydrochloric acid con-centration,liquid-to-solid ratio,and stirring speed on Ca leaching efficiency.Finally,the carbonation reaction was carried out,and the transformation ratio of calcium ions,purity of calcium carbonate,and microstructure were stud-ied using XRD,SEM-EDS,and TG-DTG.The results indicated that hydrochloric acid concentration and liquid-to-solid ratio were the main factors influencing Ca leaching from AOD slag.As the leaching reaction proceeded,the sili-cate colloids formed by the dissolution of Si-based groups hindered the further leaching of elements within AOD slag.Increasing temperature and acid concentration effectively eliminated the impact of silicate colloids,promoting Ca leaching.Under the conditions of leaching with 1.5 mol/L HCl at 85℃,a liquid-to-solid ratio of 50 mL/g,and a stirring speed of 600 r/min,the leaching ratio of Ca from AOD slag could reach 90.51%.Through thermogravi-metric analysis,the purity of the CaCO3 product prepared after indirect carbonation was 96.04%,and the conver-sion ratio of Ca reached 83.96%.The results provide experimental and theoretical foundations for the efficient resource utilization of metallurgical solid waste by carbon sequestration using steel slag Ca and simultaneous prepara-tion of high-value-added CaCO3 products.
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