Visualizing Flocculation and Adsorption Processes in Papermaking Using Fluorescence Microscopy

Polymer adsorption characteristics in complex papermaking systems have been elucidated using tagged reagents and the well-established technique of fluorescence microscopy. Interactions between polymers and components of papermaking slurries have been previously well researched, but the theories put forth are usually based on indirect inferences. Moreover, the use of simple model systems often does not permit correlation with real systems. The present study clearly shows that, under shear conditions and time scales prevalent on a paper machine, polymer partitions to inorganic fillers and fiber fines. In the absence of fillers, the polymer adheres to high surface area regions of the fiber, viz., fibrils that result from mechanical fiber processing operations. The roles of surface area, electrostatic interactions, and other papermaking operations are discussed in detail. We believe this study to be the first extension of fluorescence microscopy for visualizing polymer partitioning in complex systems such as papermaking slurries. On the basis of the data provided here, it should be facile to extend this application for studying polymer behavior in other systems such as sludge dewatering and mineral processing.