A mechanistic study on the coupled organic and colloidal fouling of nanofiltration membranes
The more wide-spread use of nanofiltration membranes in industrial applications is dependent upon understanding the fouling behavior of representative feed solutions, such as complex suspensions with both organic and colloidal inorganic foulants. In this thesis, three hypothesized mechanisms responsible for enhanced membrane flux decline in the presence of multiple foulant types are examined experimentally: increased hydraulic resistance of the mixed cake layer structure, hindered foulant diffusion due to interactions between solute concentration polarization (CP) layers, and changes in colloid surface properties due to organic adsorption. Additionally, a modified composite cell-model is developed to incorporate the structural differences of a merged, combined fouling layer. Results, including a synergistic effect caused by increased resistance of a heterogeneous fouling layer as well as the adsorption effects of interacting foulants, indicate that current fouling layer models need to be reexamined to include the mechanisms suggested in this study.
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