Nitrogen and Phosphorus Recovery from Chicken Manure Biogas Slurry via Magnesium-Modified Zeolite Coupled with Electrochemical Precipitation Crystallization
This study investigates the recovery of nitrogen and phosphorus from anaerobic digestion biogas slurry of chicken manure via magnesium-modified zeolite coupled with electrochemical precipitation crystallization. Three types of magnesium-modified zeolites were prepared using alkali activation and magnesium loading to enhance adsorption capacity. A coupled 'magnesium-modified zeolite-electrochemical MAP' reactor was constructed, and key parameters (N/P ratio, pH, current density) were optimized via response surface methodology. The results show that MgCl2-modified zeolite (MgCl2-ZO) exhibited the best coupling precipitation performance. Under optimal conditions (N/P ratio 3.78, pH 8.43, current density 13.11 A·m−2), the removal efficiencies for total nitrogen (TN), total ammonium nitrogen (TAN), total phosphorus (TP), and total phosphate (TPS) reached 54.84%, 62.93%, 82.02%, and 77.72%, respectively. The mechanism involves synergistic adsorption and electrochemical release of Mg2+ from the magnesium electrode, which promotes struvite crystallization. The electrochemical field enhances ion exchange and chemical precipitation on the zeolite surface, facilitating efficient nutrient recovery. This approach offers a promising solution for nutrient management in livestock wastewater.