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Calcite Dissolution in Deionized Water from 50℃ to 250℃ at 10 MPa:Rate Equation and Reaction Order

查看全文 作　　者：GONG Qingjie DENG Jun WANG Qingfei YANG Liqiang SHE [1]Min 高影响力作者 机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083高影响力机构 出　　处：《Acta Geologica Sinica(English Edition)》索引2008年第82卷第5期,共8页高影响力期刊 摘　　要：Carbonate minerals and water (or geofluids) reactions are important for modeling of geochemical processes and have received considerable attention over the past decades.The calcite dissolution rates from 50℃to 250℃at 10 MPa in deionized water with a flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor.The dissolution began near the equilibrium with c/c_(eq)>0.3 and finally reached the equilibrium at 100℃-250℃,so the corresponding solubility was also determined as 1.87,2.02,2.02 and 1.88×10^(-4)·mol/L at 100℃,150℃,200℃and 250℃respectively,which was first increasing and then switching to decreasing with temperature and the maximum value might occur between 150℃and 200℃.The experimental dissolution rate not only increased with temperature,but also had a rapid increase between 150℃and 200℃at a constant flow rate of 4 mL/min.The measured dissolution rates can be described using rate equations of R=k(1-c/c_(eq))n or R=kc^(-n).In these equations the reaction order n changed with temperature,which indicates that n was a variable rather than a constant,and the activation energy was 13.4 kJ/mol calculated with R=k(1-c/c_(eq))~n or 18.0 k J/mol with R=kc^(-n),which is a little lower than the surface controlled values.The varied reaction order and lower activation energy indicates that calcite dissolution in this study is a complex interplay of diffusion controlled and surface controlled processes. 关 键 词：方解石 分解 溶度 动力学 反应级数
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