Flocculation Control of Ceramic Powder Slurries by Water Soluble Polymers with Different Ionicities

Abstract

The factors for the flocculation control of ceramic powder (alumina and alumino-silicate) slurries by various water soluble polymers with different ionicities were investigated through floc size, porosimetry, and polymer adsorption. The results are summarized as follows; (1) Floc size depends on the sign and the strength of charged sites on ceramic particles, ionicities of polymers, solid loading, and slurry pH. (2) Cationic polymers make mainly particles containing SiO sites flocculate, and the floc size increases with increasing pH and solid loading. Anionic and nonionic polymers make particles containing Al (O, OH) sites flocculate, and the floc size increases with decreasing pH and increasing solid loading. (3) The peak pore diameter in a dried floc obtained at high pH is smaller than that at low pH which shows a wide pore distribution. The high pH floc is denser than the low pH floc. (4) It was found that there are two systems showing different floc size behavior. In one system the floc size increases with increasing polymer adsorption, while in the other system it increases with decreasing adsorption. The former is anionic and nonionic polymer systems, the latter is cationic polymer system. This behavior suggests the difference in the mechanisms of polymer adsorption and/or flocculation.