Selective adsorption of yttrium(III) and ytterbium(III) from rare earth leachate using a phytic acid (C₆H₁₈O₂₄P₆)-modified adsorbent

The adsorption of rare earth ions (RE³⁺) using modified adsorbents has been proven to be an effective and sustainable extraction method. This study screened phytic acid (C₆H₁₈O₂₄P₆) modified Serratia marcescens (SR-PA) for its ability to efficiently adsorb RE³⁺ from rare earth leachate by determining the best adsorption conditions. Quantum theoretical modeling elucidated the binding mode of phytic acid with RE³⁺. The results showed a maximum adsorption capacity of SR-PA was 103 mg/g. The SR-PA data fitted the Langmuir model and the pseudo-first-order kinetic model. The adsorptive capacity of yttrium(III) and ytterbium(III) by SR-PA were 92.9 % and 89.0 %, respectively, and SR-PA significantly increased the distribution coefficient values of yttrium(III) and ytterbium(III). The separation factor calculations revealed that ytterbium(III) was the easiest RE³⁺ to separate, followed by yttrium(III), dysprosium(III), and gadolinium(III). The electrostatic attraction of SR-PA with RE³⁺ was evaluated using zeta potential measurements, and the dual mesopore–macropore structure of SR-PA was confirmed via characterization analyses. The analyses revealed that the phosphate group in SR-PA adsorbs RE³⁺ through complexation, where PA preferentially forms a colloidal structure with RE³⁺. After five cycles, a slight decline in absorption was observed, confirming the reusability of SR-PA. In addition, the biosafety of SR-PA was confirmed through dissolution tests. The structure of SR-PA is stable, and its application prospects are promising.