摘要:
借助PHREEQC软件,文章对方解石、白云石分别在无CO2和大气PCO2条件下NaCl、KCl、CaCl2和MgCl2溶液中的溶解度进行了模拟计算,结果显示:方解石在NaCl、KCl、和MgCl2溶液中以及白云石在NaCl、KCl溶液中的溶解度比纯水中大得多,其原因主要是盐效应。由于同离子效应,在CaCl2溶液中可降低方解石溶解度,而白云石在较高浓度CaCl2或MgCl2溶液中,虽发生同离子效应,其溶解度仍较纯水中有不同程度提高。模拟还显示,方解石在MgCl2溶液中以及白云石在CaCl2溶液中溶解时将分别发生白云石化和去白云石化反应,从而促使不全等溶解继续发生。在常规离子中,按方解石、白云石溶解度提高发挥作用的重要性排序为:阴离子中都是SO24->Cl-;对于方解石溶解,阳离子中Mg2+>Na+>K+>Ca2+;对于白云石溶解,当PCO2=0或PCO2=10-3.5bar且CaCl2浓度大约在1.5mol/L以下时,Na+>K+>Ca2+>Mg2+;当PCO2=10-3.5bar且CaCl2浓度大约在1.5mol/L以上时,Ca2+>Na+>K+>Mg2+。
Abstract:
With the PHREEQC software,the solubility of calcite and dolomite in the NaCl,KCl,CaCl2,and MgCl2 solution under non-air and atmospheric P CO2 conditions is simulated.The results indicate that the solubility of calcite in NaCl,KCl and MgCl2 solution and the solubility of dolomite in NaCl and KCl solution are much larger than those in pure water.The primary reason for this is the salt effect function.Because of the common ion effect,CaCl2 can reduce the solubility of calcite.The solubility of dolomite in higher concentration of CaCl2 or MgCl2 solution is higher than it is in pure water,in spite of the common ion effect and the dolomitization in CaCl2 solution exist.Simulation still reveals that dolomitization and dedolomitization will take place in the calcite dissolved in MgCl2 solution and in the dolomite dissolved in CaCl2 solution,making the incongruent dissolution continue to happen.Among the routine ions,the important sequencing of the improvement solubility of the calcite and dolomite functions is that as for calcite dissolution,the effect of anion SO 2-4 is greater than that of Cl-,the effect order of the ions in the system is Mg 2+ >Na+>K+ >Ca 2+.As for dolomite dissolution,the effect of anion SO 2-4 is greater than that of Cl-,while the effect of ion is determined by P CO2 and concentration of CaCl2.When P CO2 =0 or when P CO2 =10-3.5 bar and the concentration of CaCl2 is lower than 1.5mol/L,the effect order of the ions in the system is Na+>K+ >Ca 2+ >Mg 2+.When P CO2 =10-3.5 bar,and concentration of CaCl2 is higher than 1.5 mol/L,the effect order becomes Ca 2+ >Na+ >K+>Mg 2+.
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