The Flocculation Characteristics and Mechanisms of <scp> CO ₂ </scp> ‐Responsive Cationic Polymers for Diatomaceous Suspension

ABSTRACT CO 2 ‐responsive cationic polymers offer a route to couple industrial kiln exhaust pretreatment with sludge deep dewatering, using the abundant CO 2 in flue gas as a trigger to enhance flocculation. This study proposes a flocculation then activation strategy to enhance the flocculation effects of the CO 2 ‐responsive Poly‐(DMC‐DMAEMA) copolymer. The polymer is first dispersed in its low‐viscosity, non‐activated state to achieve uniform contact with suspended particles, followed by CO 2 bubbling to trigger in situ protonation of the PDMAEMA blocks. Using a diatomaceous suspension as model sludge, flocculation behaviors under different CO 2 addition modes were systematically compared. Pre‐activation caused a sharp increase in solution viscosity and poor dispersibility, aggravating inhomogeneity. Post‐activation‐dispersion followed by CO 2 activation effectively balanced uniform adsorption with in situ bridging reinforcement, yielding superior floc growth, turbidity removal, and dewatering efficiency. This mechanistic strategy directly resolves the dispersion problem characteristic of conventional high‐molecular‐weight flocculants, thereby establishing a foundation for the integrated application of kiln exhaust pretreatment and sludge deep dewatering.