Membrane fouling concentration polarization measurement

Passage of bacteria through membrane Analysis of deposits ATR, FTIR, measuring fouling in real time Measuring concentration polarization Mathematical modeling of flux decline... 

The first set of experiments, carried out to compare the performance of membranes with MWCO of 10, 20, and 50 kDa, were carried out using a pressure of 2 bar and 200 rpm agitation, to expose the systems to the same concentration polarization and fouling effects. Before and after the UF experiments, the membrane hydraulic permeability coefficient (Lp) was measured to evaluate the permeability loss. 

Membrane fouling and the subsequent permeate flux decline is one of the major drawbacks. A number of theories about concentration polarization, cake formation and flux decline have been developed to predict membrane fouling. Generally those models are based on an assumed behavior and validated by experimental determinations. Nevertheless, typical experimental measurements are focused on macroscopic parameters, such as permeate flux, pressure drop and solute rejection, which provide little information about microscopic phenomena and, thus, are not able to validate mechanistic models. 

Manufacturers tend to characterize membranes by means of rejection measurements with reference molecules, such as dextrans, proteins, or polyglycols. A parameter extensively used for membranes characterization is the cutoff value, which is defined as the lower limit of solute molecular weight for which the rejection is at least 90%. We must keep in mind, however, that rejection measurements always depend on the type of solute (shape and flexibility of the macromolecular solute), the membrane (its interaction with the solute), and the process parameters used (pressure, cross-flow velocity, geometry of the test cell, and concentration and type of solute). In particular, concentration or polarization, pore blocking, and fouling phenomena affect rejection measurements very significantly. 

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