Novel oxymagnesite/green rust nanohybrids for selective removal and slow release of phosphate in water

The new paradigm in wastewater treatment demands to change traditional pollutants removal into resource recovery, especially for non-renewable P resources, effectively recovering phosphate from wastewater and reutilizing it as a nutrient is crucial to P sustainable utilization and P-related pollution control. The nanomaterial-based adsorption technology for P recovery from wastewater is becoming a research hotspot due to its high efficiency and selectivity. Herein, to recover aqueous phosphate, we developed novel oxymagnesite/green rust (OMGR) nanohybrids by a one-pot hydrothermal method. Green rust nanoparticles dispersed on the highly reactive oxymagnesite (MgO2MgCO₃) nanosheets could achieve efficient recovery and reuse of P. The volume ratio of water to ethylene glycol played an important role in the preparation of OMGR. The OMGR possessed an excellent selectivity of phosphate removal in the presence of multi-anions and wide pH adaptability in 4.0-10.0. The formation of MgP nanocrystals and the inner-sphere FeOP complexes via ligand exchange contributed to the selective removal of P by OMGR, and the removal capacity reached 141 mg P^.g^-1. The process of phosphate removal by OMGR was spontaneously endothermic and controlled by the intraparticle and boundary layer diffusion. Most importantly, the high bioavailable P (127 mg^.g^-1) of P-loaded OMGR had a persistent release behavior regulated by dissolution and diffusion, indicating that the P-loaded OMGR can act as a slow-release P-fertilizer. The findings provide a green and eco-friendly approach to realizing P resource recovery and reuse for phosphate-containing wastewaters.