Analysis of microstructural properties of ultrafiltration cake layer during its early stage formation and growth

Understanding the development of microstructure of cake layer during filtration can help establish effective operating conditions and membrane cleaning cycles. In this work, dynamic behavior of cake layers formed during early stage of ultrafiltration (UF) of colloids was analyzed in terms of cake porosity, fractal structure and evolution of fouling mechanisms. Experimental data on membrane fouling by SiO2 colloids under different conditions were recorded to study the effect of pH (1.0-8.9), salinity (0-3.5 %wt. NaCl) and nanoparticle concentration (30-1000 ppm). The results show time dependent behavior of cake porosity with a steady state value lower at lower pH and at higher salinity of the continuous phase. Multiple fouling mechanisms were identified to occur sequentially with cake filtration as the dominant mechanism. High fractal dimension (2.45-2.94) was obtained in all conditions tested. Fractal dimension of a growing cake is shown to undergo a sharp transition to a higher value, pointing to cake restructuring during filtration.

Automated summary

Understanding the dynamic behavior of cake layers formed during early stage of ultrafiltration (UF) of colloids, including cake porosity, fractal structure, and evolution of fouling mechanisms, can help establish effective operating conditions and membrane cleaning cycles. Experimental data on membrane fouling by SiO2 colloids under different conditions revealed time dependent behavior of cake porosity with distinct characteristics under various conditions, highlighting multiple fouling mechanisms occurring sequentially. High fractal dimension was consistently obtained in all conditions tested, indicating a sharp transition to a higher value during cake restructuring.