Sodium alginate/polyvinyl alcohol for the recovery of rare earth elements from mining wastewater: Mechanism and properties

With the demand for rare earth elements (REEs) increasing in the high-tech sector, the recovery of REEs from secondary sources is becoming very critical. In this study, sodium alginate/polyvinyl alcohol (SA/PVA) beads obtained by cross-linking alginate with polyvinyl alcohol were used to recover REEs from real rare-earth wastewaters. The results showed that SA/PVA beads are less affected by temperature and exhibited adsorption selectivity for REEs. The efficiency of adsorbing REEs ranged from 27.6% to 52.6%, but was significantly higher than that of 9.2% Mn. Meanwhile, among the observed REEs, SA/PVA beads revealed a preference for light REEs (44.3% − 52.6%). The adsorption process was investigated utilizing advanced characterization methods, namely Scanning Electron Microscope, Fourier Transform Infrared Spectrometer, and X-ray Diffraction Spectra. Combined with the results of Pearson correlation analysis, we proposed that the adsorption process involves the combined effects of ion exchange, complexation, electrostatic interaction and pore filling. As well, a desorption efficiency of more than 76.9% can be achieved with sodium citrate, which makes possible the effective recovery of REEs. In summary, this study provides a promising green, environmentally friendly and sustainable material for the enrichment and recovery of REEs from mining wastewater.