On the rare-earth metal ions adsorption onto biochars of dead Posidonia oceanica leaves

Rare earth elements (REE] belong to thè list of criticai raw materials, i.e. thè list of materials whose recovery is considered strategie from thè European Community.1 Adsorption is recognized as one of thè most attracting recovery technique, in particular when thè adsorbents employed become from waste platforms.2-3 This contribution presents thè results achieved using three biochars obtained from thè pyrolysis of dead Posidonia oceanica, a marine plant whose leaves accumulate in abundance on thè sicilian cost, as adsorbents of rare earth metal ions from aqueous solutions. To this end, thermodynamic and kinetic adsorption experiments were carried out to study thè recovery of lanthanum, neodymium and dysprosium ions onto thè biochar of Posidonia oceanica as it was (BC] and after two types of chemical activation, i.e., an acid activation threating thè material with phosphoric acid (BCA] and a basic activation with potassium hydroxide (BCBJ in aqueous solution at pH = 5 and t = 25°C. Thè adsorption of REE ions onto BCA was also studied in NaNCh 0.1 mol L1 at pH = 3 and pH = 6 to evaluate thè effect of pH and of thè ionie medium. Chemical and morphological characterization of adsorbents were carried out by SEM-EDX, FT-IR, dementai analysis and nitrogen adsorption/desorption measurements. Thè REE adsorption was well described by Langmuir isotherm equation. Among thè tested adsorbents, thè BCA showed thè highest qm value. Moreover, thè adsorption capacity decreases with thè decreasing of pH and in presence of NaN03. Thè adsorption equilibrium was reached within 8 hours. Recycling experiments, using HNO3 or EDTA 0.1 mol L_1 as extractants, were also carried out to test thè reusability of the BCA. References: [1] European Commission, https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=C ELEX:52023PC0160 (accessed 8 November 2023], 2023. [2] Cataldo, S.; Muratore, N.; Giannici, F.; Bongiorno, D.; Chiodo, V.; Maisano, S.; Pettignano, A., Environ. Sci. Pollut. Res., 2022, 29,90231. [3] Cataldo, S.; Chiodo, V.; Crea, F.; Maisano, S.; Milea, D.; Pettignano, A., J. Mol. Liq., 2018, 271, 481.