Selectivity of lanthanum and ytterbium in binary and multi-component system by modified sericin/alginate/poly (vinyl alcohol) adsorbent beads

Rare earths are essential for important industrial applications and for producing high-tech materials. Its recovery from secondary sources is fundamental from an environmental and economic perspective. Biosorption is a promising method that can be used to remove and recover rare earth at low concentrations in an aqueous medium due to its low cost, simplicity, and efficiency. Recently, natural biomaterials based on sericin/alginate began to be investigated as a biosorbent for rare-earths uptake. Sericin is a natural protein of silkworm cocoons, usually discarded along with silk industry effluents, and alginate is a natural carbohydrate extracted from abundant sources of brown algae. The particles produced by the sericin/alginate blend were crosslinked with poly (vinyl alcohol) (PVA), which promotes better properties to this biomaterial. In this study, modified beads of a sericin/alginate/PVA blend were produced by ionic imprinting (Ca(NO3)2, Ca(NO3)2/La(NO3)3, or La(NO3)3) and leaching with HNO3 (0.1 mol/L). The developed particles were applied to remove ytterbium and lanthanum from aqueous solutions through adsorptive affinity and selectivity tests. The results indicated that the modified particles showed superior removal efficiency for lanthanum. For ytterbium, the highest removals were obtained for sericin/alginate/PVA-La(NO3)3 (94.33 +/- 0.05%), sericin/alginate/PVA-Ca(NO3)2/La(NO3)3 (94.05 +/- 3.12%), and sericin/alginate/PVA-Ca(NO3)2 (92.06 +/- 2.01%). For lanthanum, higher removal values were obtained for sericin/alginate/PVA-La(NO3)3 (100.71 +/- 0.77%), sericin/alginate/PVA-Ca(NO3)2/La(NO3)3 (99.21 +/- 0.28%), and sericin/alginate/PVA-Ca(NO3)2 (98.45 +/- 2.98%). In the binary system of rare earths, selectivity between the metals was not observed, however the modified beads showed great selectivity performance for lanthanum and ytterbium in multi-metal solution. Additionally, the modified beads with ionic imprinting were characterized by SEM, EDS, FTIR, XPS, and TGA/DTG. Thus, the results indicated that modified sericin/alginate/ poly(vinyl alcohol) beads could be used as an alternative and promising biosorbent to remove and recover rare earths.