Na^＋,K^＋,Mg^2＋/Cl^-,SO4^2-,NO3^-,H2O体系液固相平衡研究

Study on Liquid-Solid Equilibrium of Na^+,K^+,Mg^(2+)/Cl^-,SO_4^(2-),NO_3^-,H_2O System

针对新疆硝酸盐卤水矿所属的Na^+,K^+,Mg^(2+)/Cl^-,SO_4^(2-),NO_3^-,H_2O六元体系,首次提出了其在25℃、氯化钠饱和时相图的表示方法,并结合生产实际,用等温法测定了所需相图区域的溶解度数据,进行了实际卤水的等温蒸发实验。研究表明:在相图中,氯化钠和硫酸钠分别与白钠镁矾、钾芒硝、钠硝矾有三盐共饱面;氯化钠和硫酸钠分别与白钠镁矾、钾芒硝、钠硝矾中的任两盐有四盐共饱线;氯化钠、硫酸钠、白钠镁矾、钾芒硝及钠硝矾有一个五盐共饱点;实际卤水等温蒸发时的析盐顺序为:氯化钠、氯化钠+无水芒硝、氯化钠+无水芒硝+白钠镁矾、氯化钠+无水芒硝+白钠镁矾+钾芒硝。

The brine of Xinjiang Lop Nur in China consists of the Na^＋,K^＋,Mg^2＋/Cl^-,SO4^2-,NO3^-,H2O system saturated with NaCl and Na2SO4.A phase diagram expression method of this system at 25℃ was proposed in this paper for the first time.The isothermal evaporation experiments of the brine mentioned were conducted,and the solubility data at phase equilibrium of the above system,which are needed for drawing the phase diagram of the system,were measured by isothermal method at 25℃.The plotted phase diagram shows that it consists of one invariant point： NaCl＋Na2SO4＋3K2SO4·Na2SO4＋Na2SO4·NaNO3·2H2O＋Na2SO4·MgSO4·4H2O;three invariant curves： NaCl＋Na2SO4＋Na2SO4·NaNO3·2H2O＋ Na2SO4·MgSO4·4H2O,NaCl＋Na2SO4＋3K2SO4·Na2SO4＋ Na2SO4·MgSO4·4H2O,NaCl＋Na2SO4＋3K2SO4·Na2SO4＋Na2SO4·NaNO3·2H2O;and three crystallization regions： NaCl＋Na2SO4＋3K2SO4·Na2SO4,NaCl＋Na2SO4 ＋Na2SO4·NaNO3·2H2O,NaCl＋Na2SO4＋Na2SO4·MgSO4·4H2O.Based on the experimental data and the phase diagram presented,the reasonable utilization scheme of the brine resource from Xinjiang Lop Nur was discussed,and the crystallization sequence of different salts from the mentioned brine during isothermal evaporation process was determined.