Deformation in Layer-by-Layer Hollow Fiber Nanofiltration Membranes: Compaction-Expansion Model.

Area of Science:

• Materials Science
• Chemical Engineering
• Membrane Science

Background:

• High operating pressure can cause structural deformation in membranes, negatively impacting separation performance, stability, and efficiency.
• Layer-by-layer (LBL) hollow fiber (HF) nanofiltration (NF) membranes are susceptible to pressure-induced changes.

Purpose of the Study:

• To investigate the impact of hydraulic pressure on the structural integrity and performance of LBL HF NF membranes.
• To analyze the relationship between substrate mechanical properties (Young's modulus) and membrane deformation under pressure.

Main Methods:

• Experimental analysis of membrane morphology and performance changes under varying hydraulic pressures.
• Focus on the Young's modulus of the poly(ether sulfone) (PES) substrate.
• Development and application of a compaction-expansion model to describe LBL skin layer behavior.

Main Results:

• High pressure induced irreversible radial compaction and circumferential expansion in the PES substrate.
• Lower substrate Young's modulus led to more pronounced deformation and earlier performance deterioration.
• A three-stage compaction-expansion model (compaction, limited stretching, significant stretching) was proposed for the LBL skin layer.

Conclusions:

• The study provides a physical explanation for performance degradation in LBL NF membranes under high pressure.
• Membrane deformation is directly linked to substrate stiffness and applied pressure.
• Insights are valuable for designing mechanically stable LBL HF membranes with improved long-term performance.