Preparation of a magnetic tannic acid zirconium for the removal of the ammonia nitrogen and enhancing coagulation with polyaluminum chloride

Ammonia nitrogen (NH 4 + ‐N) is a key pollutant responsible for water eutrophication, posing significant risks to both ecological systems and human health. Conventional coagulation processes, while central to water treatment, are inherently inefficient for nitrogen removal. To address this limitation, a novel magnetic tannic acid zirconium (MTAZ) adsorbent was synthesized via chemical coating. Optimal synthesis was achieved at a TA:ZrCl 4 molar ratio of 1:5, a nano‐Fe 3 O 4 dosage of 0.0007 mol, pH 7, and a drying time of 32 h. Structure characterization confirmed that MTAZ possesses an amorphous structure with successfully loaded nano‐Fe 3 O 4 and stable functional groups. The adsorbent exhibited a saturation magnetization of 3.66 emu/g, enabling rapid magnetic separation with negligible loss of magnetic properties after adsorption. MTAZ demonstrated selective adsorption for NH 4 + ‐N, showing no affinity for nitrate or nitrite. Under optimized conditions (raw water pH 6–7, MTAZ dosage 9 g/L, 20 min slow stirring), the maximum NH 4 + ‐N removal efficiency in simulated wastewater reached 89.63%. Coexisting SiO 3 2− and Mg 2+ ions were identified as the primary inhibitors of adsorption. The adsorption mechanism involves electrostatic attraction, surface complexation, and hydrogen bonding. When integrated with polyaluminum chloride (PAC) for real wastewater treatment (slow stirring at 70 r/min, MTAZ dosage 9 g/L), the system achieved over 85% NH 4 + ‐N removal and 81.67% total nitrogen (TN) removal, while maintaining excellent turbidity removal (96.53%). These findings highlight MTAZ as a promising material for enhancing nitrogen removal in coagulation‐based water purification processes.