CIESC Journal ›› 2017, Vol. 68 ›› Issue (7): 2653-2659.DOI: 10.11949/j.issn.0438-1157.20161758

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Phase equilibria of AlCl3+CaCl2+H2O, AlCl3+FeCl3+H2O and CaCl2+FeCl3+H2O ternary systems at 35℃

YUAN Mengxia, QIAO Xiuchen   

  1. School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2016-12-15 Revised:2017-02-15 Online:2017-07-05 Published:2017-07-05
  • Contact: 10.11949/j.issn.0438-1157.20161758
  • Supported by:

    supported by the National High Technology Research and Development Program of China(2011AA06A102) and the National Natural Science Foundation of China (21176082).

三元体系AlCl3+CaCl2+H2O,AlCl3+FeCl3+H2O和CaCl2+FeCl3+H2O在35℃时的相平衡

袁梦霞, 乔秀臣   

  1. 华东理工大学资源与环境工程学院, 上海 200237
  • 通讯作者: 乔秀臣
  • 基金资助:

    国家高技术研究发展计划项目(2011AA06A102);国家自然科学基金项目(21176082)。

Abstract:

It is difficult to prepare pure AlCl3·6H2O through evaporation crystallization in aluminum recovery from leaching coal fly ash by hydrochloric acid, without phase equilibria diagram for AlCl3, CaCl2 and FeCl3 solution. The phase equilibria of AlCl3+CaCl2+H2O, AlCl3+FeCl3+H2O and CaCl2+ FeCl3+H2O ternary systems at 35℃ were investigated using isothermal dissolution method. After solubility and densities were measured, phase diagram and density diagram were plotted against compositions. The phase diagrams of AlCl3+CaCl2+H2O and AlCl3+FeCl3+H2O had two univariant curves and two crystallization zones without formation of double salt or solid solution. Solubility of AlCl3 decreased with increasing concentration of CaCl2 or FeCl3 due to common ion effect. Double salt CaCl2·2FeCl3·7H2O was formed in CaCl2+FeCl3+H2O ternary system. When temperature was increased from 25℃ to 35℃, phase equilibria diagrams of AlCl3+CaCl2+H2O, AlCl3+FeCl3+H2O and CaCl2+FeCl3+H2O were all changed. Crystallization zone of AlCl3·6H2O in AlCl3+CaCl2+H2O and AlCl3+FeCl3+H2O ternary systems was enlarged and crystallization zone of CaCl2·6H2O was converted into crystallization zone of CaCl2·4H2O. Crystallization zone of CaCl2·2FeCl3·8H2O in CaCl2+FeCl3+H2O ternary system was converted into crystallization zone of CaCl2·2FeCl3·7H2O.

Key words: phase equilibria, solubility, crystallization, aluminum chloride, calcium chloride, ferric chloride

摘要:

缺少含AlCl3、CaCl2和FeCl3的溶液相平衡,使通过蒸发结晶从粉煤灰盐酸浸取液中制备纯净的AlCl3·6H2O变得比较困难。采用等温溶解法研究了三元体系AlCl3+CaCl2+H2O,AlCl3+FeCl3+H2O和CaCl2+FeCl3+H2O在35℃时的相平衡关系,测定了相应的溶解度及密度,并绘制了相应相图及密度-组成图。实验结果表明:三元体系AlCl3+CaCl2+H2O和AlCl3+FeCl3+H2O分别有两条溶解度曲线,两个单盐结晶区,无复盐和共溶体产生,同离子效应导致增加溶液中CaCl2和FeCl3浓度会有效降低AlCl3的溶解度;CaCl2+FeCl3+H2O体系会形成复盐CaCl2·2FeCl3·7H2O;所得35℃相图与25℃相图相比,三元体系AlCl3+CaCl2+H2O和AlCl3+FeCl3+H2O中AlCl3·6H2O结晶区增大,CaCl2·6H2O结晶区转变成CaCl2·4H2O结晶区,CaCl2+FeCl3+H2O体系中CaCl2·2FeCl3·8H2O结晶区转变为CaCl2·2FeCl3·7H2O结晶区。

关键词: 相平衡, 溶解度, 结晶, 氯化铝, 氯化钙, 氯化铁

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