Rapid recovery of rare earth elements in industrial wastewater by CuFe2O4 synthesized from Cu sludge

This study systematically evaluates the recovery of rare earth elements (REEs) from aqueous solution and industrial wastewater using magnetic nanoparticles CuFe₂O₄. The industrially manufactured CuFe₂O₄ displays a nonlinear isotherm for REEs adsorption, suggesting limiting binding sites on the CuFe₂O₄ surface. The recovery of REEs increases significantly from 0.1% to 99.99% with increasing pH (2.29–8.15). At room temperature, the maxima recovery rates of Nd, La, and Ce are observed to be in a high capacity of 51.02, 42.02, and 40.16 mg/g, respectively. No significant attenuation of REE adsorption is observed with increasing NaCl concentration from 0.001 to 1.0 mol/L, showing high selectivity of REEs even in such high NaCl concentration matrix. In addition, desorption efficiency increases with the increasing concentration of HNO₃ in the range of 0.005–0.05 mol/L. When HNO₃ concentration is over 0.05 mol/L, the desorption efficiency can reach almost 100% in each batch experiment. Importantly, our results show that REEs can be sorbed and recycled from liquid crystal display (LCD) polishing wastewater, suggesting that CuFe₂O₄ may be a good candidate in the efficient and rapid recovery of REEs from industrial wastewater.