Optimization of Flocculation Conditions for Kaolin Suspensions Using [(3-methacryloylamino)propyl]trimethylammonium Chloride and Dimethylacrylamide Copolymer

Abstract

The flocculating effect of [(3-methacryloylamino)propyl]trimethylammonium chloride-dimethylacrylamide (TMAPMACh-DMAA) copolymer samples at various molar ratios on a kaolin suspension was studied. Varying the flocculant concentration from 0.01 g/L to 0.24 g/L revealed that 0.04 g/L was the most effective; at concentrations below 0.04 g/L, the copolymer exerted a stabilizing effect on the kaolin suspension. A study of the effect of pH on flocculation revealed that the maximum degree of kaolin suspension clarification was achieved in the pH range of 5.0-7.0. This is due to the neutralizing effect of the ammonium groups of [(3-methacryloylamino)propyl]trimethylammonium chloride on the ≡SiO^– groups of kaolin particles. Electrophoresis data demonstrated that although kaolin particles possess a negative charge in the pH range from 3.0 to 9.0, the negative ζ-potential values decrease in an acidic medium. Copolymer samples with TMAPMACh:DMAA molar ratios of 50:50 and 60:40 are optimal for flocculation, providing a sufficient number of cationic groups to neutralize the negative charge of kaolin particles. A relationship between the kaolin particle ζ-potential and flocculation efficiency is demonstrated. The role of neutralization and «bridging» flocculation mechanisms in the sedimentation of kaolin particles using the TMAPMACh-DMAA copolymer is substantiated.