Biosynthesis of manganese nanoparticles for efficient recovery of rare earth elements from mining wastewater

Ionic rare earth mining wastewater contains a certain amount of rare earth elements (REEs). Given the scarcity and great application potential of REEs, this study explored the potential of employing manganese nanoparticles (GT-Mn) derived from green tea to recover REEs from mining wastewater. The maximum adsorption efficiencies of GT-Mn on REEs were 98.50 % (Y), 94.85 % (La), 73.33 % (Gd), 75.00 % (Dy), and 81.25 % (Yb), respectively. Characterizations were conducted to elucidate the mechanism of GT-Mn in the recovery of REEs. The findings revealed that the adsorption capacity of GT-Mn for REEs is predominantly attributed to the presence of organic functional groups, including tyrosine and theanine, along with the interactions of Mn O bonding interactions. Moreover, the zeta analysis supported the electrostatic interaction between GT-Mn and REEs. Thus, the key physicochemical properties of REEs removal by GT-Mn were statistically analyzed by Pearson's correlation analysis, indicating that the removal mechanism of REEs included complexation and electrostatic force. The desorption of REEs from GT-Mn in 0.01 M acetic acid (CH 3 COOH) solution showed that the desorption efficiency of REEs exceeded 75.00 %. Overall, GT-Mn demonstrates significant potential and advantages in the realm REEs recovery, which can achieve the dual benefits of environmental remediation and resource conservation.