Internal structure visualization of polymer - clay flocculants using fluorescence

Polymer flocculation is commonly used to remove colloidal material from solution, improving separation performance. The structure of the mesoscale formation (floc) affects process performance, as well as the amount of polymer required. By visualizing polymer in flocs using fluorescently-tagged polymers and laser confocal microscopy, we directly observe effects of ionic strength on polymer-clay floc internal structure. At low ionic strength, I < 10 mM NaCl, the polymer forms a continuous, interconnected internal network, whereas at high ionic strength, the polymer no longer forms this network and simply coats the larger bentonite aggregates. This method offers the ability to visualize the polymer structure without drying or freezing the solution, making it ideal for observation of delicate aggregates. While especially applicable to water purification, the structure observations shown here yield important fundamental insights for polymer adsorption dynamics onto inorganic heterogeneous particulate or surface structures.