Rare Earths (La, Y, and Nd) Adsorption Behaviour towards Mineral Clays and Organoclays: Monoionic and Trionic Solutions

Cinzia Cristiani,Giovanni Dotelli,Paola Gallo Stampino,Saverio Latorrata,Elena Maria Iannicelli Zubiani,Maurizio Bellotto,Gianguido Ramis,Elisabetta Finocchio

doi:10.3390/min11010030

Cinzia Cristiani, Giovanni Dotelli + Show 6 more

Open Access

https://doi.org/10.3390/min11010030

Copy DOI

Journal: Minerals	Publication Date: Dec 29, 2020
Citations: 14	License type: CC BY 4.0

Affiliation: Politecnico di Milano, University of Genoa

Abstract

Metals from electric and electronic waste equipment (WEEE) can be recovered by dissolution with acids followed by liquid–liquid extraction. A possible alternative to liquid–liquid extraction is liquid–solid adsorption, where sorbents efficiency is the key factor for process efficiency. In this respect, aim of this paper is the study of the behaviour of two solid sorbents for the recovery of Rare Earths (REs)—in particular, La, Nd, and Y—from scraps of end-of-Life (EOL) electronic equipment. Two solid matrices were considered: a pristine montmorillonite clay and a modified-montmorillonite clay intercalated with a commercial pentaethylen-hexamine. The capture ability of the solids was tested towards single-ion La, Nd, and Y solutions and a multi-element solution containing the three ions. Before and after the uptake step, samples of both the solid and liquid phases were analysed. For both sorbents, at lower metal initial concentrations, the ions were captured in similar amount. At higher concentrations, pure clay showed a high total uptake towards La ions, likely due to surface interactions with clay sites. The organoclay preferentially interacts with Nd and Y. Considering the presence of the polyamine, this behaviour was related to ion coordination with the amino groups. The capture behaviour of the two sorbents was related to the different physicochemical properties of the ions, as well as to the ionic radius.

Highlights

In the modern technologies, Rare Earths (REs) are key components, especially applied in electronic devices
The aim of this paper is to demonstrate the feasibility of the use of pristine and modified clays for the recovery of Rare Earths (REs) from aqueous solutions—
The preparation of the organoclays was performed according to a procedure developed elsewhere, which implied the mixing of the clay with the aqueous polyamine solution in a jacketed reactor under vigorous stirring (500 rpm) for 90 min at a controlled temperature of 30 ◦ C, at pH = 11

Summary

Introduction

Rare Earths (REs) are key components, especially applied in electronic devices. In the near future, an increasing demand of REs will occur [1]. Due to their wide application, one of the critical points in their use is supply. Even if world production can satisfy the global demand, monopoly, difficult production technologies, and environmental risks make RE supply a serious problem [3]. The mitigation of this problem could derive from the use of secondary REs coming from wise waste management and recycling. REs are contained in various electrical and electronic wastes—mainly electric and electronic devices but, in other industrial waste residues (e.g., catalysts) [4,5,6,7,8]

Objectives

Methods

Results