From Visualization to Mechanism: Uncovering Early Fouling Dynamics in Nanofiltration through LIF Experiments

Area of Science:

• Membrane Science and Technology
• Water Treatment
• Surface Science

Background:

• Early fouling in nanofiltration (NF) membranes is a critical issue affecting performance and efficiency.
• Real-time characterization of dynamic fouling evolution has been limited.
• Understanding early fouling mechanisms is essential for optimizing NF system design and operation.

Purpose of the Study:

• To visualize and quantify the spatiotemporal development of early fouling in NF membranes.
• To investigate the influence of cross-flow velocity and transmembrane pressure on fouling dynamics.
• To elucidate the dominant forces governing foulant transport during early fouling stages.

Main Methods:

• Utilized laser-induced fluorescence (LIF) technology for real-time visualization and quantification of fouling.
• Employed discrete phase model (DPM) simulations to analyze particle transport and forces.
• Combined experimental data with computational modeling for a comprehensive analysis.

Main Results:

• Higher cross-flow velocity (10 mL/s) significantly mitigated foulant accumulation, stabilizing surface concentration and reducing fouling layer thickness.
• Low velocity (0.1 mL/min) and high pressure (5 bar) led to rapid foulant accumulation.
• Flux derivative analysis and LIF imaging identified transitions from intermediate blocking to cake-like deposition.
• DPM simulations identified Saffman lift and permeation drag as key forces in particle transport.

Conclusions:

• The integrated experimental-computational framework provides novel insights into early fouling mechanisms in NF.
• Cross-flow velocity and transmembrane pressure are critical parameters modulating fouling behavior.
• Findings offer a foundation for developing strategies to enhance fouling control and operational efficiency in water treatment.