Quantitative analysis of cake characteristics based on SEM imaging during coagulation-ultrafiltration process

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Materials Science

Background:

• Membrane fouling by flocs significantly impacts coagulation-ultrafiltration (CUF) processes.
• Understanding floc properties is crucial for mitigating membrane fouling.
• Scanning electron microscopy (SEM) offers potential for characterizing floc cake structures.

Purpose of the Study:

• To investigate the relationship between floc properties and cake characteristics in CUF.
• To evaluate the efficacy of SEM imaging at various magnifications for determining cake porosity.
• To correlate floc properties with pore characteristics within the cake layer.

Main Methods:

• Floc cake samples were analyzed using SEM at magnifications of ×5000, ×10,000, and ×20,000.
• Cake porosity was calculated from SEM images and validated using the Carman-Kozeny equation.
• Floc properties (average size, fractal dimension) and pore characteristics were quantified.

Main Results:

• SEM at ×5000 magnification accurately estimated cake porosity (error < 5.00%) and captured comprehensive pore information.
• Cake porosity showed a strong correlation with floc average size, suggesting floc size dominates porosity.
• Pore characteristics like average length and area correlated with floc fractal dimension, while pore fractal dimension and amount related to floc size.

Conclusions:

• SEM imaging is a feasible and effective method for evaluating cake characteristics and porosity in CUF.
• Floc average size is a key determinant of cake porosity, influencing membrane fouling.
• Specific floc properties directly correlate with distinct pore characteristics, providing insights into fouling mechanisms.