Ammonium-accelerated recovery of rare earth elements from mine wastewater by an indigenous Pseudomonas oryzihabitans...

The mining process of ion-adsorption-type rare earth ores generates a large amount of wastewater containing rare earth elements (REEs) and high concentrations of ammonium nitrogen (NH⁺₄-N). It is urgent to develop single-stage, low-energy technologies to achieve REEs recovery and NH⁺₄-N removal simultaneously. Here, we present a local Pseudomonas oryzihabitan, which is capable of achieving this goal. Interestingly, the typical pollutant ammonium does accelerate the recovery of REEs. Comprehensive characterizations show that the fixation of REEs mainly occurs extracellularly through surface complexation and biomineralization. The acceleration of REE recovery by NH⁺₄-N may involve multiple mechanisms, including supporting rapid bacterial growth, enhancing extracellular organic secretion, and promoting biomineralization. Importantly, this acceleration is specific to ammonium and cannot be replicated by other nitrogen sources supporting comparable biomass. This strain was able to recover over 90% of the REEs and remove 76.2% of NH⁺₄-N from real mine wastewater within 34 h, suggesting its potential as a starting point for bioremediation strategies. This work provides a conceptual basis for designing single-reactor bioprocesses that can convert wastewater from rare earth mines rich in NH⁺₄-N into sustainable metal resources.