New Insights into Ion Adsorption Type Rare-Earths Mining-Bacterial Adsorption of Yttrium Integrated with Ammonia Nitrogen Removal by a Fungus

Ion adsorption-type heavy rare earths found in southern China are important ore resources, whose yttrium(Y)-group rare-earth elements account for 90% of the total mass of rare earths known on the planet. At present, ammonia-nitrogen wastewater from extraction of rare earths pose threats to the environment. A bacterial strain (Bacillus sp. ZD 1) isolated from the Foot Cave mining area was used for adsorption of Y3+. Its adsorption capacity reached 428 mu mol/g when the initial concentration of Y3+ was 1.13 mM. Moreover, 50 mg of Bacillus sp. ZD 1 (converted to dry mass) could completely adsorb Y3+ in the mother solution of mixed rare earths from the rare-earth mining area. Ammonia nitrogen in the remaining solution after adsorption was removed through denitrification using a fungus named Galactomyces sp. ZD 27. The final concentration of ammonia nitrogen in wastewater was lower than Indirect Emission Standard of Pollutants for Rare-earth Industry (GB 26451-2011). Furthermore, the resulting fungal cells of Galactomyces sp. ZD 27 could be used to produce single cell proteins, whose content accounted for 70.75% of the dry mass of cells. This study offers a new idea for integrated environmentally-friendly extraction and ecological restoration of the mining area in southern China.

Automated summary

This study demonstrates that utilizing Bacillus sp. ZD 1 and Galactomyces sp. ZD 27 for adsorption and removal of ammonia nitrogen can reduce the threat posed by rare earth extraction wastewater to the environment and achieve effective resource utilization.