Sulfonic-functionalized algal/PEI beads for scandium, cerium and holmium sorption from aqueous solutions (synthetic and industrial samples)

The one-pot synthesis of algal biomass/polyethyleneimine beads, ALPEI (electrostatic interaction followed by calcium ionotropic gelation), produces a stable sorbent whose sorption properties for rare earth elements (REEs) are significantly improved functionalization. grafting sulfonic groups (S-ALPEI), which have high affinity REEs, increases capacities as 2.68 mmol Sc g−1, 0.61 Ce g−1 and 0.53 Ho at pH close to 4 (equilibrium pH). Sorption isotherms fitted the Langmuir equation scandium cerium; holmium, Freundlich Sips equations show better fits. occurs within 30–40 min; kinetic profiles pseudo-first order rate Crank (resistance intraparticle diffusion). has marked preference Sc(III) against Ce(III) Ho(III) (confirmed selectivity tests). is also selective REEs alkali-earth elements. three metals readily desorbed (within 20–30 min) using HCl/CaCl2 solution. Desorption remains higher than 99% 5 cycles while performance decreased less 6% fifth cycle. tested recovery valuable from red mud solution different values. Despite large excess heavy in industrial solution, S-ALPEI shows good 3.46 with important enrichment factors (in range 19–118 depending on metal). material fully characterized BET, TGA, FTIR, XPS, elemental analysis, titration SEM-EDX analysis. involves mechanisms (on amine groups) including electrostatic attraction chelation metal speciation.