Enhanced Flocculation Efficiency in a High-Ionic-Strength Environment by the Aid of Anionic ABA Triblock Copolymers

The flocculation efficiency of polyelectrolytes in a high-ionic-strength environment is often affected and reduced due to shielding of the active ionizable functional groups, as well as changes in the surface chemistry of the solid slurry. To address this problem, a series of well-defined novel ABA triblock copolymers were employed for the flocculation of high-ionic-strength kaolin slurries at three different Ca²⁺ concentrations (0.05, 0.10, and 0.50 M). The primary focus was on the advancement in the polymer architecture, where the anionic functionalities were localized at the terminal ends. Typical commercial flocculants tend to have anionic functionalities randomly distributed throughout the polymer chain and hence a higher propensity toward condensed conformation and formation of insoluble species. In comparison to a control random copolymer, the ABA triblock copolymers were able to flocculate kaolin slurries to give faster settlement rates, particularly at the high Ca²⁺ concentrations of 0.10 and 0.50 M. In addition, these polymers had significantly better clarification ability at higher Ca²⁺ concentrations compared to the control random copolymer. The ABA triblock copolymer architecture may therefore have potential as a flocculant in high-ionic-strength applications.