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Crystals 2017, 7(8), 244;

Separating NaCl and AlCl3·6H2O Crystals from Acidic Solution Assisted by the Non-Equilibrium Phase Diagram of AlCl3-NaCl-H2O(-HCl) Salt-Water System at 353.15 K

Institute of Resources and Environmental Engineering, State Environment Protection Key Laboratory of Efficient Utilization of Coal Waste Resources, Shanxi University, Taiyuan 030006, China
College of Chemical Engineering, Qinghai University, Xining 810016, China
Author to whom correspondence should be addressed.
Academic Editor: Lan Xiang
Received: 30 June 2017 / Revised: 26 July 2017 / Accepted: 2 August 2017 / Published: 4 August 2017
(This article belongs to the Special Issue Solution-Processed Inorganic Functional Crystals)
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Extracting AlCl3·6H2O from acid leaching solution through crystallization is one of the key processes to extracting aluminum from fly ash, coal gangue and other industrial solid wastes. However, the obtained products usually have low purity and a key problem is the lack of accurate data for phase equilibrium. This paper presented the non-equilibrium phase diagrams of AlCl3-NaCl-H2O (HCl) salt-water systems under continuous heating and evaporation conditions, which were the main components of the acid leaching solution obtained through a sodium-assisted activation hydrochloric acid leaching process. The ternary system was of a simple eutonic type under different acidities. There were three crystalline regions; the crystalline regions of AlCl3·6H2O, NaCl and the mixture AlCl3·6H2O/NaCl, respectively. The phase diagram was used to optimize the crystallization process of AlCl3·6H2O and NaCl. A process was designed to evaporate and remove NaCl at the first stage of the evaporation process, and then continue to evaporate and crystallize AlCl3·6H2O after solid-liquid separation. The purities of the final salt products were 99.12% for NaCl and up to 97.35% for AlCl3·6H2O, respectively. View Full-Text
Keywords: crystallization; phase diagram; high purity; AlCl3·6H2O; NaCl crystallization; phase diagram; high purity; AlCl3·6H2O; NaCl

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Cheng, H.; Zhang, J.; Lv, H.; Guo, Y.; Cheng, W.; Zhao, J.; Cheng, F. Separating NaCl and AlCl3·6H2O Crystals from Acidic Solution Assisted by the Non-Equilibrium Phase Diagram of AlCl3-NaCl-H2O(-HCl) Salt-Water System at 353.15 K. Crystals 2017, 7, 244.

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