Yue ZHANG
defended her PhD thesis
on 6 october 2022
Modification de billes composites à base de biomasse algale/alginate de sodium à des fins de récupération d’ions métalliques
devant le jury composé de :
– Jacques DESBRIERES, Professeur à l’Université de Pau et des Pays de l’Adour – Rapporteur
– Ana SASTRE, Professeure à Polytechnic University of Catalonia – Rapporteure
– Bénédicte PRELOT, Directrice de Recherche à l’Université de Montpellier – Présidence du Jury
– Jérôme HUSSON, Maître de Conférences à l’Université de Franche-Comté – Examinateur
– Eric GUIBAL, Professeur à l’Ecole de Mines d’Alès – co-encadrant de thèse
– Catherine FAUR, Professeure à l’Université de Montpellier – Directrice de thèse
Abstract:
The algal/alginate-based beads materials have been fabricated by the combination of algal biomass and alginate-composites, via crosslinking process (calcium ionotropic gelation and amine-glutaraldehyde crosslinking). These materials (algal/alginate/PEI=APEI) possess abundant functionalities (carboxyl, hydroxyl, amine groups), as well as good structural stability (via double interactions of alginate/PEI and PEI/GA), which allows their adaptability for further chemical functionalization process. To improve the affinity of metal ions, APEI beads have been surface grafted with N-based moieties (quaternary ammonium salts, or amidoxime). The functionalization process not only enhances the density and number of reactive groups on sorbent, also provides a wider pH range for metal recovery/removal. The chemically-modified beads have been mainly used for two applications: (a) removal and recovery of metals anions (Cr(VI)) and rare earth cations (RE(III)), and (b) separation and purification of REs(III). The materials and their interactions with metal ions were analyzed by FTIR, SEM, EDS, and XPS. The quaternary ammonium-functionalized beads (Q-APEI) exhibited outstanding removal efficiency for Cr(VI) anions, through the interactions of electrostatic attraction/anion exchange (protonated amines, quaternary ammonium salts), coupled with chemical reduction (carboxyls, hydroxyls). The presence of reduced Cr(III) was both detected on the Q-APEI surface and aqueous phase. Also, the study indicated that the flow rate of chromate effluents may impact the release of Cr(III) into water. On the other side, the amidoxime-functionalized beads (AO-APEI) were applied for the recovery of rare earth cations via the cation-exchange (carboxylates), and complexation (amidoximes, free amines). The sorbents showed slight preference for heavy rare earth (Dy(III), Er(III)) over light rare earth (La(III)), but not enough for their separation. Meanwhile, a study was conducted for exploring the effect of soluble complexing ligand on intelligent modification of metal speciation. The results demonstrated that the sorbents exclusively bound only metal cations instead of anionic metal-ligand complex even in the presence of protonated amino functions. Based on this, the selectivity and extracted purity of La(III) ions using AO-APEI were considerably improved through the preferential complexation of heavy rare earths with chelating ligand. This study illustrates the feasibility of chemical functionalization and metal speciation modification for improving the sorption performance (sorption capacity, and/or selectivity) of alginate-based polymeric materials in a solid-liquid system.
Keywords: sorption; alginate; chemical modification; metals; recovery; separation
