Fouling structure analysis

The XPS analysis of unwashed membranes showed that ESCA could identify the organic fouling layers of the membranes as well as the surface structure. Peak fitting regimens determined whether the materials discovered were foulants deposited (as indicated by the N (Is) data) on the surface or materials that had become chemically bound to the surface. To be chemically bound to the surface, the foulant must show an oxidation state indicative of a bond with membrane substituents. If the foulant showed a chemical composition not associated with the membrane, it was determined to be lying on the surface (physisorbed) and not chemically attached. This was the case for calcium on LFCl (Ca (2pl, 2p3)BE 350.3-346.9 eV). However, this finding does not preclude the possibility of calcium complexation with functional groups of the RO membranes used... 

Arthanareeswaran, G. and Thanikaivelan, P. 2010. Fabrication of cellulose acetate-zirconia hybrid membranes for ultrafiltration applications Performance, structure and fouling analysis. Separation and Purification Technology lA 230-235. 

This chapter covers aspects related to CSLM and its uses in pressure-driven membrane processes. The first part deals with the fundamentals of the technique, the conditions required to obtain a proper visualization either of the membrane or the foulants and some examples of image analysis that lead to quantitative information on membrane structure and the extent of fouling. The uses of CSLM for membrane characterization, adsorption of target compounds to membranes and, in particular, fouling characterization are thoroughly reviewed in the second part of this chapter. 

The combination of a multiple staining protocol with CSLM enabled the visualization of the 3D structure ofthe main components of a biofouling layer (details are reviewed in Section 4.3.3). By applying a complex image analysis, several morphological parameters were determined, such as the porosity and fractal dimension of the fouling layer. 

The morphology visualization, adhesion and cohesive characteristics during biofilm analysis can provide a usefiil insight for fouling study in MBR. Only limited amounts of AFM analysis have been used on MBR surfaces however this technique has the potential not only to provide imaging but also local force/ rheological measurement of biofilm adhesion and structure. 

This technique was used to measure the fouling thickness deposited on a tubular membrane. Bentonite as a particulate model solution was filtered during fouling characterization experiments. The maximum CFV and solid concentration used for this analysis were 0.3 m s and 375 mg L , respectively [72]. The limitations of the technique are the inability to visualize the cake structure and the requirement of light adsorption into the lumen, reducing the visualization potential for MBR study. Extended information can be found in Chapters 11 and 15. 

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