Coagulation Performance and Mechanisms of Polymeric Zirconium coagulants: Insights from Integrated Experiment and Simulation

Abstract

Zirconium-based coagulants are a novel class of inorganic coagulants that have attracted considerable attention in recent years because of their outstanding coagulation performance. This study introduces a novel polymeric zirconium-based coagulant and compares the coagulation performance of two variants with different counterions, polymeric zirconium chloride and polymeric zirconium sulfate, in treating domestic sewage. The results show that both polymeric zirconium sulfate and polymeric zirconium chloride achieve turbidity removal rates above 95%, total organic carbon removal above 90%, and total phosphorus removal above 90%. The flocs exhibit a dense core, a rough surface, good settling properties, and a large specific surface area. These coagulants primarily remove contaminants through the synergistic mechanisms of charge neutralization and adsorption bridging. Compared with polymeric zirconium chloride, polymeric zirconium sulfate exhibits more stable removal efficiency across a broader dosage range and performs better over a wider pH range. polymeric zirconium chloride derived flocs have a faster grow rate, whereas polymeric zirconium sulfate derived flocs show greater resistance to breakage and stronger recovery capacity. The mechanistic similarities and differences were further elucidated through molecular dynamics simulations. This study provides theoretical support for the application of polymeric zirconium-based coagulants in water treatment.