Fabrication of a Lignin-Based Magnetic Nanocomposite Adsorbent to Recover Phosphorus in Water for Agricultural Reuse

Phosphorus (P) is an essential nutrient for crops, but its excess in discharge water harms both surface water and groundwater quality. A cost-effective and eco-friendly adsorbent is desirable to meet circular economy criteria by effectively removing P from water and being safely recycled for agricultural use. Thus, this study aims to synthesize an amine-functionalized magnetic lignin nanocomposite biosorbent by first grafting poly(ethyleneimine) on epoxidized lignin followed by coprecipitation with iron. This biosorbent shows an adsorption performance of 43 mg g(-1), which is 20 times greater than the unmodified lignin reported in a previous research study and six times more than the magnetic iron metal. A series of characterization methods confirm the chemical features and the formation of a nanostructure. The pH, coexisting anions, and salt concentrations affect the P removal efficiency. The mechanism studies show that the electrostatic interaction between NH3+ functional groups and P, surface precipitation, and ligand exchange all count for P removal, which indicates the heterogeneous adsorption of P onto the sorbent surface by both chemisorption and physisorption. The seedling study confirms that the nanocomposite after P adsorption has better root development and biomass accumulation as a recycled fertilizer.

Automated summary

This study successfully synthesized an amine-functionalized magnetic lignin nanocomposite biosorbent, greatly improving phosphorus adsorption performance, and demonstrating its application in recycled fertilizers.