Adsorption isotherms and kinetics of rare earth metals on multifunctional materials from various waste pomaces

This contribution presente thè preliminary resuite obtained using waste biomasses from thè industriai food chain for thè preparation of multifunctional materials possibly able to detect, bind and extract, efficiently and selectively, rare earth metal ions from aqueous solutions simulating reai matrices. These metals belong to thè list of “Criticai Raw Materials”, i.e. thè group of materials whose recovery is considered strategie by thè European Community1. Thè use of food-processing industry wastes as secondary raw materials offers a sustainable and environmentally friendly approach, that could also be useful for thè rare earth metals recovery. In particular, thè adsorption of neodymium and dysprosium ions in aqueous solution was studied at pH ~ 5 and t = 25°C using different waste biomasses, namely Bergamot Pomace (BP), Olive Pomace (OP) and Grape Pomace (GP), chemically pretreated at t = 30°C with H2O and HNO3 0.10 mol dm 3 2,3. Thè materials were characterized employing different analytical techniques; through thè FT-IR ATR spectroscopy 2, it was possible to confimi thè presence of functional groups capable of interacting with thè above mentioned metals. To evaluate their adsorption capacity, batch experiments were carried out on different solutions containing thè metal ions (M3+ = Nd3+, Dy3+)- Thè concentration of each M3+ was determined by ICP-OES 4. Thè results obtained from adsorption experiments show that Langmuir equation was thè best isotherm fitting model for BP, OP and GP for thè rare earth metals adsorption. Thè adsorption equilibrium was reached within 24 hours and thè kinetic of adsorption was well described by thè pseudo-second order model. Then thè recovery of thè metals adsorbed on thè biomasses was carried out using HNO3, but thè reused materials show lower performance than thè starting ones, exception done for BP, which showed great reutilization capacities 4 Acknowledgements: We thank MUR: PNRR - Missione 4, Componente 2, Investimento 1.1 - Bando Prin 2022 - Decreto Direttoriale n. 104 del 02-02-2022. Project title: “Wastezilla: Recycled waste biomass for efficient recovery of criticai elements”. CUP: J53D23007540006 - project code: PR1N_2O22HYH95P_OO1 CUP: B53D23013740006- project code: 2022HYH95P_003 References: [1] European Commission, https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:52023PC0160,2024. [2] A. Irto, S.G.M. Raccuia et al. Microchem. J. 2023,193,109183 [3] A. Satira et al. Appi. Sci. 2021,11(22), 10983. [4] S. Cataldo et al. Environ. Sci. Pollut. Res. 2022,29,9023.