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新型碱源脱钙固碳之后的海水中存在的大量镁离子和碳酸氢根,提取其中的镁离子可以实现海水镁资源利用并将海水进一步软化;分离碳酸氢根使固碳彻底,有利于后续海水资源利用.镁和碳酸氢根的提取需要在碱性条件下进行,因此,本实验将CO2脱钙之后的海水体系简化为Mg2+//CO32-、HCO3-、OH--H2O体系.并利用等温溶解平衡法,研究该体系在10℃条件下的相平衡,探索体系的析盐规律.液相组成通过溶液滴定法获得,由X射线衍射分析技术测出固相物质组成得出,并利用origin9.0软件绘制出四元体系相图.相图中得到1个三相共饱点,固相物组成是MgCO3·3H2O、Mg(OH)2和Mg5(C O3)4(OH)2·8H2O;3条共饱和曲线分别为MgCO3·3H2O、Mg(OH)2的共饱线,Mg5(CO3)4(OH)2·8H2O、Mg(OH)2的共饱线,Mg5(CO3)4(OH)2· 8H2O、MgCO3· 3H2O的共饱线;2个明显的结晶区,MgCO3· 3H2O结晶区和Mg(OH)2结晶区,1个Mg5(CO3)4(OH)2·8H2O的部分结晶区.以上实验数据可为盐化工生产及结晶分离提纯提供参考依据.“,”A large number of magnesium ions and bicarbonate radical in the seawater after decalcification and carbon fixation of the new alkaline source.The extraction of magnesium ions can realize the utilization of seawater magnesium resources and further soften seawater.Meanwhile separation of bicarbonate is conducive to the subsequent use of seawater resources.The extraction of magnesium and bicarbonate need to be carried out under alkaline condition.Therefore,in this experiment,the seawater system after CO2 decalcification is simplified as Mg2+//CO2-3,HCO3-,OH--H2O system.In order to explore the law of salt deposition in explosive system,the isothermal dissolution equilibrium method is used to study the phase equilibrium of the seawater system which is the phase equilibrium system at 10 ℃.The liquid phase composition is obtained with solution titration method,the composition of the solid phase material is determined by X-ray diffraction analysis technology,and the phase diagram of the quaternary system is drawn by using the software of origin9.0.We obtain a three-phase total saturation which comprises MgCO3· 3H2O,Mg (OH) 2 and Mg5 (CO3)4 (OH)2· 8H2O.The three cosaturated curves are respectively as follows:MgCO3· 3H2O and Mg (OH)2 co-saturated line,Mg5 (CO3)4 (OH)2·8H2O and Mg(OH)2 co-saturated line,Mg5(CO3)4(OH)2·8H2O and MgCO3·3H2O co-saturated line;the two distinct crystalline regions are MgCO3-3H2O crystalline region and Mg (OH)2 crystalline region; a partial crystalline region of Mg5(CO3)4(0H)2 -8H2O. The experiment provides a reference for salt chemical production and crystallization separation and purification.