Polyelectrolyte titrations of synthetic mineral microparticle suspensions to evaluate charge characteristics

Colloidal charge properties were determined for a system of synthetic mineral microparticles (SMM), which have been developed to promote drainage of water and retention of fine particles during papermaking. Prior research, as well as our own preliminary research showed that the SMM system can have advantages in both of drainage and retention, compared with montmorillonite (bentonite), which is one of the most popular materials presently used in this kind of application. Streaming current titrations employing highly charged polyelectrolytes and were used to evaluate the charge properties of SMM suspensions and to understand the interactions among SMM particles, fibers, fiber fines, and cationic polyacrylamide (cPAM). Polyelectrolyte titrations were carried out under different conditions of pH to predict the charge properties of SMM under conditions that reflect paper manufacturing practices. It was found that pH variation, caused by the change of Al/Si ratio and partial neutralization of aluminum's acidity, profoundly affected the charge properties of SMM, due to the variation of Al-ions and the influence ionizable groups on the Si-containing particle surface.