(376ad) Crystal Morphology and Process Control of Multiple High-Salinity Wastewater Treatment Via Membrane Distillation Crystallization

Crystal Morphology and
Process Control of Multiple High-salinity Wastewater via Membrane Distillation
Crystallization

Guannan Li, Gaohong He, Xiaobin
Jiang*

State Key Laboratory of Fine Chemicals, Research
and Development Center of Membrane Science and Technology, School of Chemical
Engineering, Dalian University of Technology, Dalian, P. R. China

*Corresponding author: Email: xbjiang@dlut.edu.cn

Abstract

Nowadays, the separation of water recovery and
salinity is mainly carried out by evaporative crystallization (ECr) [1].
However, ECr has the disadvantages of high operation temperature and
uncontrolled supersaturation. Therefore, it is necessary to introduce a new
separation technology [2,3].

This study is based on existing research
work, and propose treatment of multiple high-saline wastewater with evaporation
membrane distillation crystallization (VMDC). Coal chemical industry wastewater
is a typical multiple high-saline wastewater, which is mainly composed of NaCl
and MgCl₂. The
influence of different mass fraction of NaCl and MgCl₂ in the feed fluid on the permeation flux
of membrane has been studied. Besides, the effect of impurity MgCl₂
on the NaCl crystal in the process of MDC has also been investigated. The
results indicated that, as the mass fraction of MgCl₂ in the feed
increases from 0% to 100%, the viscosity of the solution gradually increases,
and permeation of the water of the membrane distillation gradually decreases(shown in Fig. 1),. In addition, as the mass fraction of MgCl₂ in the feed
increases continuously, crystal surface appearance defects has been obviously (shown in Fig. 2),and average crystal size has been gradually increased(shown in Fig. 3).

The study has been demonstrated
the possibility of VMDC in the treatment of multiple high-saline wastewater.
Compared with traditional evaporative crystallization, it provides a
theoretical basis for the practical application of VMDC.

Fig. 1 The permeate flux changing with different
NaCl and MgCl₂ mass fraction

Fig.2 The crystal surface morphology with
different NaCl and MgCl₂ mass fraction

Fig. 3 The crystal size distribution with
different NaCl and MgCl₂
mass fraction

References

[1]   
Lu H, Wang J, Wang T,
et al. Crystallization techniques in wastewater treatment: An overview of
applications[J]. Chemosphere, 173: 474-484 (2017).

[2]    Zhang Y, Peng Y, Ji S, et al. Review of
thermal efficiency and heat recycling in membrane distillation processes[J].
Desalination, 367: 223-239(2015).

[3]    Chabanon E, Mangin D, Charcosset C.
Membranes and crystallization processes: State of the art and prospects[J]. J. Mem. Sci.,
509: 57-67(2016).