Ultrafast separation of Nd and Dy from Co by modified mesoporous silica with a novel phosphate group ligand

Recycling rare earth elements (REEs) from NdFeB magnets alleviates the growing demand for these resources and contributes to environmental protection. Phosphate groups are known for their high adsorption selectivity for rare and precious metals. In this study, a novel phosphorus-functionalized silicon-based adsorption material (PPA@APTES/SBA-15) was synthesized using poly (ethylene glycol)- block -poly (propylene glycol)- block -poly (ethylene glycol) copolymer (P123) as a template, tetraethyl orthosilicate (TEOS) as a silicon source, (3-amino-propyl) trimethoxysilane (APTES) as a coupling agent, and phosphite ester as a functional ligand. This material was designed for the adsorption and separation of Nd and Dy from NdFeB leaching simulants. The batch experiments revealed that PPA@APTES/SBA-15 achieved equilibrium separation of Co and REEs within 10 s, with SF REE/Co  ≥ 2018.76. The material exhibited near 100 % adsorption efficiency for Nd and Dy in 6 M HCl solution, along with excellent reusability. Notably, column experiments also demonstrated near complete adsorption efficiency for Nd and Dy. SEM-EDS, TEM, XRD, and N 2 adsorption-desorption isotherms confirmed that PPA@APTES/SBA-15 possessed a uniform hexagonal mesoporous structure and a high specific surface area. TG-DSC analysis demonstrated that the organic loading of PPA@APTES/SBA-15 was 9 %. FT-IR, XPS, and DFT analysis suggested that PPA@APTES/SBA-15 bond metal ions via P OH (P O) groups.