In‐situ cross‐linked PVDF membranes with enhanced mechanical durability for vacuum membrane distillation

Abstract

A novel and effective one-step method has been demonstrated to fabricate cross-linked polyvinylidene fluoride (PVDF) membranes with better mechanical properties and flux for seawater desalination via vacuum membrane distillation (VMD). This method involves the addition of two functional nonsolvent additives; namely, water and ethylenediamine (EDA), into the polymer casting solution. The former acts as a pore forming agent, while the latter performs as a crosslinking inducer. The incorporation of water tends to increase membrane flux via increasing porosity and pore size but sacrifices membrane mechanical properties. Conversely, the presence of EDA enhances membrane mechanical properties through in-situ cross-linking reaction. Therefore, by synergistically combining the effects of both functional additives, the resultant PVDF membranes have shown good MD performance and mechanical properties simultaneously. The parameters that affect the cross-link reaction and membrane mechanical properties such as reaction duration and EDA concentration have been systematically studied. The membranes cast from an optimal reaction condition comprising 0.8 wt % EDA and 3-hour reaction not only shows a 40% enhancement in membrane Young's Modulus compared to the one without EDA but also achieves a good VMD flux of 43.6 L/m 2 -h at 608C. This study may open up a totally new approach to design next-generation high performance MD membranes.

Bipolar membrane electrodialysis: A promising paradigm for caustic soda production

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“…Seawater is the most abundant natural resource that contains a multicomponent liquid and accounts for 96%–97% of the Earth's water 1 . It is desirable to transform seawater into high‐value‐added chemicals by developing highly effective techniques 2 . The chlor‐alkali process is a feasible method to convert saturated NaCl into the fundamental chemicals NaOH, 3 Cl 2 , and H 2 for the aluminum oxide (Al 2 O 3 ), viscose staple fiber, 4 and polyvinyl chloride (PVC) industries 5 .…”

Membrane-Assisted Cooling Crystallization for Interfacial Nucleation Induction and Self-Seeding Control

“…Being a highly designable and environment-friendly material, membranes have led to great development in many fields related to the crystallization process. − One of their most impressive applications is that the membrane serves as a heterogeneous nucleation interface to accelerate the nucleation process. − The supersaturated solution on the membrane surface generates nuclei, and the formed particles can auto-detach from the surface under a suitable dynamic force field. , This result is of importance for the effective control of the mass transfer related to the crystallization process (evaporative crystallization, antisolvent crystallization, etc.). Besides, the outstanding heat transfer features of the hollow fiber membrane also benefit the heat exchange and the relevant process control .…”

Interface‐based crystal particle autoselection via membrane crystallization: From scaling to process control

“…Over the past decade, membrane crystallization (MCr), an innovative hybrid separation technology combining membrane technology with crystallization, has rapidly developed . With the intrinsic advantages of membrane technology and an improved energy utilization efficiency, MCr can simultaneously produce the desired crystal product and ultrapure solvent with relatively low energy input . The hollow fiber membrane module utilized in MCr provides a plentiful and uniform contact interface for the mass transfer of the crystallization solution, which facilitates the precise control of the supersaturation degree and micromixing condition.…”