Separation and Recycling of Concentrated Heavy Metal Wastewater by Tube Membrane Distillation Integrated with Crystallization

Tube membrane distillation (MD) integrated with a crystallization method is used in this study for the concurrent productions of pure water and salt crystals from concentrated single and mixed system solutions. The effects of concentrated Zn<sup>2+</sup> and Ni<sup>2+</sup> o...

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Bibliographic Details
Main Authors: Xiang-Yang Lou, Zheng Xu, An-Ping Bai, Montserrat Resina-Gallego, Zhong-Guang Ji
Format: Article
Language:English
Published: MDPI AG 2020-01-01
Series:Membranes
Subjects:
Online Access:https://www.mdpi.com/2077-0375/10/1/19
Description
Summary:Tube membrane distillation (MD) integrated with a crystallization method is used in this study for the concurrent productions of pure water and salt crystals from concentrated single and mixed system solutions. The effects of concentrated Zn<sup>2+</sup> and Ni<sup>2+</sup> on performance in terms of membrane flux, permeate conductivity, crystal recovery rates, and crystal grades are investigated. Preferred crystallization and co-crystallization determinations were performed for mixed solutions. The results revealed that membrane fluxes remained at 2.61 kg&#183;m<sup>&#8722;2</sup>&#183;h<sup>&#8722;1</sup> and showed a sharp decline until the saturation increased to 1.38. Water yield conductivity was below 10 &#956;s&#183;cm<sup>&#8722;1</sup>. High concentrated zinc and nickel did not have a particular effect on the rejection of the membrane process. For the mixed solutions, membrane flux showed a sharp decrease due to the high saturation, while the conductivity of permeate remained below 10 &#956;s&#183;cm<sup>&#8722;1</sup> during the whole process. Co-crystallization has been proven to be a better method due to the existence of the SO<sub>4</sub><sup>2&#8722;</sup> common-ion effect. Membrane fouling studies have suggested that the membrane has excellent resistance to fouling from highly concentrated solutions. The MD integrated with crystallization proves to be a promising technology for treating highly concentrated heavy metal solutions.
ISSN:2077-0375