Adsorption of rare-earth metals on multifunctional materials from various pomaces

This contribution presents thè preliminary results 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 from thè European Community^ [1]. Thè use of food-processing industry wastes as second 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, such as bergamot pomace (BP), olive pomace (OP) and grape pomace (GP), chemically pretreated at t = 30°C with H2O and HNO3 0.10 mol dnr3 [2,3]. Thè materials were characterized employing different analytical techniques. Through thè FT-IR ATR spectroscopy [4], it was possible to confirm thè presence of functional groups capable of interacting with metals. Potentiometric titrations were performed at t = 25°C and at an ionie strength of 0.10 mol dnr3 in NaN03(aq) to study thè acid-base properties of these materials [5]. 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 [6]. Thè results obtained from adsorption experiments show that Langmuir equation was thè best fitting isotherm model for BP, OP and GP for thè adsorption of rare earth metals. In terms of maximum adsorption capacity, thè best performing material was thè BP. Moreover, release experiments were carried out to assess thè potential reuse of these materials. These experiments were conducted using HNO3 0.10 mol dnr3 solution [4]. A graphical schematic representation of thè studies carried out is reported in Figure 1.References: [1] European Commission 2020: Criticai materials for strategie technologies and sectors in thè EU. [2] Satira et al., Appi. Sci. 2021,11(22], 10983. [3] S. Schiewer, S. B. Patii, Technol. 2008,99,1896-1903. [4] Irto, S.G.M. Raccuia et al., Microchem. J. 2023,193,109183. [5] De Stefano et al., Ann. Chim. 1993, 83,243-277. [6] Cataldo, S.; Muratore, N.;et al Environ. Sci. Pollut. Res., 2022, 29,90231