title: Use of natural clays as sorbent materials for rare earth ions: Materials characterization and set up of the operative parameters.
abstract: Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption-desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture ≈ 50%, release ≈ 70%) is obtained when the uptake and release processes are performed at pH=5 and pH=1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium.
authors.affiliation: Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Piazza Leonardo Da Vinci 32, 20133 Milano, Italy. Electronic address: elenamaria.iannicelli@polimi.it.
authors.forename: Elena Maria
authors.initials: EM
authors.lastname: Iannicelli-Zubiani
authors.affiliation: Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Piazza Leonardo Da Vinci 32, 20133 Milano, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Cristiani
authors.affiliation: Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Piazza Leonardo Da Vinci 32, 20133 Milano, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Dotelli
authors.affiliation: Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Piazza Leonardo Da Vinci 32, 20133 Milano, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Gallo Stampino
authors.affiliation: Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Piazza Leonardo Da Vinci 32, 20133 Milano, Italy.
authors.forename: Renato
authors.initials: R
authors.lastname: Pelosato
authors.affiliation: Università degli Studi di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Mesto
authors.affiliation: Università degli Studi di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Schingaro
authors.affiliation: Università degli Studi di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Lacalamita
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D001546:Bentonite / Q000737:chemistry*; D000077215:Clay; D007477:Ions / Q000737:chemistry; D008674:Metals, Rare Earth / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D033362:Powder Diffraction; D013054:Spectrophotometry, Atomic; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000032:analysis*; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D001546:Bentonite; D000077215:Clay; D007477:Ions; D008674:Metals, Rare Earth; D062065:Wastewater
keywords: Clays; Electronic waste; Lanthanum; Neodymium; Rare Earths; Recovery