473821 A Novel Membrane Distillation Response Technology for Nucleation Detection and Crystallization Process Control
A Novel Membrane Distillation Response Technology for Nucleation Detection and Crystallization Process Control
Xiaobin Jiang*, Gaohong He*, Wu Xiao, Xuehua Ruan, Dapeng Lu
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
Most of researchers considered the mass transfer flux decline and the crystallization on the membrane interface as a fouling behavior. The research was focused on the strategy of avoiding and reducing the crystallization, non-attention had been paid on applying this sensitive nucleation response phenomenon to the crystallization research [1,2]. The inevitable crystallization on the membrane interface under certain operational conditions and solution concentration inspired us that the membrane interface performed as the response medium of the nucleation detection. The responding mechanism is constructed base on the chain effect of ¡®solution concentrated & metastable zone uplimit reached-nucleation on the pores of the porous membrane interface-transmembrane flux sharply decrease¡¯. The inflection point of the transmembrane flux confirms the nucleation timing on the membrane interface. The accurate recording of the transmembrane flux data can be utilized to calculate the solution concentration to determine the metastable zone width (MSZW), which is key dynamic data for the effective control strategy of crystal nucleation and growth [3,4].
Without relying on the optical signal, MDC based nucleation response method would be easy and more meaningful in the case of opaque solutions that laser intensity response (LIR) method is invalid . This advantage will improve the controlling accuracy and flexibility during MSZW measurement. Moreover, with the proposed method, it would be easy to enhance control over the process so that to select the real working conditions to simulate different evaporation rates for the concentrating rate in the isothermal membrane distillation process can be adjusted by the membrane permeability, the partial vapor pressure difference and the membrane area, etc.
While, a strict requirement on the membrane interface structure is obvious to enhance the detection accuracy of this proposed method. With conducted effective work of Trout and Diao, the developed Nanoparticle Imprint Lithography (NpIL) method had successfully prepared the polymer films with nanopores of various, uniform shapes that can hinder nucleation or promoted it . In addition, the had reported the significant impact of polymer interface with nanometer scale pores on inducing crystallization and polymorphism control [7,8]. These foundational work can promote the theoretical research and application of the MDC based nucleation response and crystallization control by providing the qualified microporous membrane as desired nucleation detection and response interface.
Fig. 1 Schematic diagram of nucleation response and metastable zone width (MSZW) measurement with MDC technology (compared with the laser detection technology)
This work is supported by National Natural Science Foundation of China (Grant No. 21306017, 21527812), Program for Changjiang Scholars and Support Project of the China Petroleum and Chemical Corporation (X514001).
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