Influences of SO42- on the solubility of calcite and dolomite
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摘要: 在无CO2和有PCO2条件下,利用目前成熟的水文地球化学模拟软件——PHREEQC,分别对方解石、白云石在Na2SO4、CaSO4和MgSO4溶液中的溶解度进行了模拟计算。结果显示:溶液中SO42-的存在对方解石、白云石溶解度的提高作用很大。如在Pco2、浓度为1200mmol/L的Na2SO4溶液中,方解石和白云石溶解度分别为纯水中溶解度的9.544和9.897倍。其作用机理是:在无同离子效应时,SO42-等所产生的盐效应和SO42-与各种阳离子形成的离子对起重要作用;而有同离子效应时,将发生白云石化或去白云石化反应,从而促使不全等溶解继续发生。与此同时,即使存在同离子效应的条件下,特别是在较高浓度条件下,盐效应的作用也是不容忽视的。Abstract: A computer analogue is given to simulate the influences of SO4^2- ion on calcite and dolomite solubility in Na2SO4,CaSO4 and MgSO4 solutions with different Pco2 at 25℃ by means of the software for hydrogeochemical modeling -PHREEQC. The results show that the existence of SO4^2- ion in solution raises calcite and dolomite solubility considerably. For example, the solubility of the calcite and dolomite in Na2SO4 solution with 1 200mmol/L in concentration and Pco2= 0 at 25 ℃ are 9. 544 and 9. 897 times greater respectively than those in pure water. The chemical mechanism for this is as follows: when common ions do not exist in solution, salt effect and ion pairs raise the solubility significantly. As common ions exist in solution, incongruent dissolution will take place, thus helps dolomitization or dedolomitization to occur. It is also concluded that the salt effect in all the cases should not be neglected including even in the cases with common ion especially when SO4^2- concentration is high.
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Key words:
- SO42- /
- calcite /
- dolomite /
- solubility /
- PHREEQC
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