Microplastic retention and accumulation in filtration membranes is increasingly recognized as a critical factor affecting membrane performance, fouling behavior, and long-term operational stability in water treatment processes. However, conventional characterization approaches provide limited insight into microplastic transport pathways within membrane structures and often rely on destructive or labor-intensive post-analysis.

This work presents an integrated experimental–modeling approach to investigate microplastic transport, retention, and clogging mechanisms in hollow fiber micro- and ultrafiltration membranes. Fluorescence-based detection using Nile Red staining is employed as a rapid, non-destructive diagnostic tool to directly visualize microplastic particles within aqueous systems and membrane structures, without extensive sample pre-treatment. The method enables spatially resolved detection of microplastics retained on membrane surfaces and within porous networks under controlled filtration conditions.

Fluorescence microscopy and emission spectroscopy are combined to monitor microplastic distribution and accumulation as a function of membrane pore size distribution, flow velocity, and particle characteristics. These experimental observations are coupled with pore network modeling to simulate microplastic transport, interception, and progressive pore blockage at the microscale. The model provides a mechanistic framework linking membrane structural properties to observed retention efficiencies and fouling patterns.

Results demonstrate that microplastic behavior in hollow fiber membranes is strongly governed by the interplay between pore size distribution and hydrodynamic conditions, leading to distinct retention and clogging regimes. The combined fluorescence–PNM approach allows direct comparison between membrane types and operating conditions, offering a powerful diagnostic tool for membrane selection and process optimization.

This methodology provides a practical pathway toward improved monitoring of microplastic fouling in filtration systems and supports the rational design of membranes with enhanced resistance to particulate contamination. The approach is readily adaptable to industrial membrane testing and offers potential for integration with real-time fluorescence monitoring strategies.