Flocculation/dispersion of particles for proper processing and/or performance in industry is a critical and difficult issue to deal with, particularly when the solids content is rather high. It is our objective to understand the fundamentals involved in controlling the stability of concentrated suspensions. Surfactants and polymers are added as stabilizers/flocculants in such systems. For polymers, the extent of adsorption and molecular conformation at the solid-liquid interface often determine their ability to perform properly. Foremost problem in this regard has been the difficulty in monitoring adsorption and particularly conformation in high solids loading suspensions.
At the Center, in-situ monitoring of polymer adsorption and conformation in concentrated suspensions has been achieved by adapting the spectroscopic techniques such as fluorescence and ESR. We conducted a series of adsorption tests to check the adsorption behavior of polymers at different solid concentration in suspensions. It is noted that polymer conformation is changing with increasing solids loading. This is possibly due to preferential adsorption as a function of solids concentration. Effect of molecular weight distribution is therefore being investigated in detail using stepwise adsorption tests. The adsorption results from these tests along with chromatographic analysis of supernatants suggest preferential adsorption of polymers from a polydispersed system. These recent results imply that preferential adsorption plays an important role in regulating suspension stability, and point out the significance of determining polymer adsorption and conformation. This in turn suggests possibilities for fine-tuning molecular weight distribution of additives in order to obtain desired dispersion characteristics.
