Na^+,K^+,Mg^(2+)∥Cl^-,SO_4^(2-)-H_2O五元体系35℃介稳相图研究  

Studies on the Metastable Phase Equilibrium of Na^+, K^+, Mg^(2+) ∥Cl^-, SO_4~ (2-)-H_2O Quinary System at 35 ℃

作　　者：金作美[1] 周惠南[1] 王励生[1] 

机构地区：[1]四川大学化工学院,成都610065

出　　处：《高等学校化学学报》2001年第4期634-638,共5页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金! (批准号 :2 90 70 0 3 0 )资助

摘　　要：研究得出 (Na+ ,K+ ,Mg2 +∥ Cl-,SO2 -4 -H2 O)五元体系 3 5℃时的介稳溶解度数据 ,绘制了该体系 3 5℃的介稳相图 ,共有 9个为氯化钠所饱和的结晶区域 :氯化钾、钾芒硝 (3 K2 SO4 · Na2 SO4 )、钾镁矾 (K2 SO4· Mg SO4 · 4 H2 O)、钾盐镁矾 (KCl· Mg SO4 · 2 .75H2 O)、光卤石 (KCl· Mg Cl2 · 6H2 O)、白钠镁矾 (Na2 SO4· Mg SO4 · 4 H2 O)、硫酸钠、六水硫酸镁 (Mg SO4 · 6H2 O)和水氯镁石 (Mg Cl2 · 6H2 O) .所得 3 5℃介稳相图与 Van t Hoff2 5℃稳定相图比较有较大区别 :软钾镁矾 (K2 SO4 · Mg SO4 · 6H2 O)、七水硫酸镁、五水硫酸镁及四水硫酸镁结晶区域消失 ,钾镁矾和钾盐镁矾结晶区域显著扩大 .所得 3 5℃介稳相图与 2 5℃介稳相图区别很大 :软钾镁矾和七水硫酸镁结晶区域消失 ,同时出现了钾镁矾和钾盐镁矾的结晶区域 .在该五元体系 3 5℃介稳相平衡研究中发现析出的是钾盐镁矾的低水化合物 (KCl·Mg SO4 · 2 .75H2 O)This paper presents the experimental data of metastable phase equilibrium of Na +, K +, Mg 2+ ∥Cl -, SO 2- 4 H 2O quinary system at 35 ℃, from which the metastable phase diagram is drawn. It consists of nine regions of crystallization saturated with sodium chloride, potassium chloride, glasserite(3K 2SO 4·Na 2SO 4), leonite(K 2SO 4·MgSO 4·4H 2O), kainite(KCl·MgSO 4·2.75H 2O), thenardite(Na 2SO 4), astrankit(MgSO 4·Na 2SO 4·4H 2O), carnallite(KCl· MgCl 2·6H 2O), magnesium sulfate hexahydrite(MgSO 4·6H 2O) and bischofit(MgCl 2·6H 2O). A large difference is found between the obtained metastable phase diagram at 35 ℃ and Vant Hoffs stable phase diagram at 25 ℃. The crystallization regions of schoenite(K 2SO 4·MgSO 4·6H 2O), epsomite(MgSO 4·7H 2O), magnesium sulfate pentahydrite(MgSO 4·5H 2O) and starkeyite(MgSO 4·4H 2O) disappear and the crystallization regions of leonit and astrankit are greatly incresed. Also there is much difference between the obtained metastable phase diagram at 35 ℃ and the metastable phase diagram at 25 ℃. The crystallization regions of schoenite(K 2SO 4·MgSO 4·6H 2O) and epsomite disappear and arise the crystallization regions of leonite and kainite. It is found that the crystallization region of low hydrate kainite(KCl·MgSO 4·2.75H 2O) exists in the metastable phase equilibrium of Na +, K +, Mg 2+ ∥Cl -, SO 2- 4 H 2O quinary system at 35 ℃.

关 键 词：介稳相平衡 海水型五元体系 硫酸型盐钾盐 介稳相图 

分 类 号：O642.4[理学—物理化学] TQ131.13[理学—化学]