Analysis of the Adsorption-Release Isotherms of Pentaethylenehexamine-Modified Sorbents for Rare Earth Elements (Y, Nd, La)

Abstract

Waste from electrical and electronic equipment (WEEE) is constantly increasing in quantity and becoming more and more heterogeneous as technology is rapidly advancing. The negative impacts it has on human and environment safety, and its richness in valuable rare earth elements (REEs), are accelerating the necessity of innovative methods for recycling and recovery processes. The aim of this work is to comprehend the adsorption and release mechanisms of two different solid sorbents, activated carbon (AC) and its pentaethylenehexamine (PEHA)-modified derivative (MAC), which were deemed adequate for the treatment of REEs deriving from WEEE. Experimental data from adsorption and release tests, performed on synthetic mono-ionic solutions of yttrium, neodymium, and lanthanum, were modelled via linear regression to understand the better prediction between the Langmuir and the Freundlich isotherms for each REE-sorbent couple. The parameters extrapolated from the mathematical modelling were useful to gain an a priori knowledge of the REEs–sorbents interactions. Intraparticle diffusion was the main adsorption mechanism for AC. PEHA contributed to adsorption by means of coordination on amino groups. Release was based on protons fostering both a cation exchange mechanism and protonation. The investigated materials confirmed their potential suitability to be employed in real processes on WEEE at the industrial level.

Efficient Capture and Release of the Rare-Earth Element Neodymium in Aqueous Solution by Recyclable Covalent Organic Frameworks

“…On the other hand, Ugi-COF-NH 2 showed a significant improvement in the q e value to ca. 84 mg/g, primarily due to the strong coordination ability of the aliphatic primary amine groups. − The addition of the DGA moiety into the Ugi-COF-DGA design provided the highest q e value of ca. 205 mg/g.…”

Efficient Capture and Release of the Rare-Earth Element Neodymium in Aqueous Solution by Recyclable Covalent Organic Frameworks

“…84 mg/g, primarily due to the strong coordination ability of the aliphatic primary amine groups. [53][54][55] The addition of the DGA moiety into the Ugi-COF-DGA design provided the highest qe value of ca. 205 mg/g.…”

Adsorption Study of Neodymium from the Aqueous Phase Using Fabricated Magnetic Chitosan-Functionalized Graphene Oxide Composites

“…On the other hand, chitosan (CS) is a natural polyaminosaccharide and is the most abundant biopolymer in nature after cellulose, where it has amino (NH 2 ) and hydroxyl (OH) groups in its molecular structure contributions, which act as the active sites. , However, chitosan also has some drawbacks such as its swelling ability, limited applications in neutral and basic media due to the deprotonation of the amino group, and slow kinetic rate. Hence, modification of GO and chitosan was investigated by many authors for the recovery of REEs and neodymium in particular. − Insertion of magnetite to the GO and CS molecules was done to facilitate the recovery of the composite from aqueous media. The magnetic chitosan@graphene oxide composite (MCh@GO) was really investigated by many authors for the sorption of heavy metals such as Ni 2+ , Zn 2+ , Co 2+ , Pb 2+ , Hg 2+ , Cu 2+ , and Cr­(VI) in addition to the remediation of dyes. − However, to the best of our knowledge and based on the literature, this composite was not used for the sorption of Nd­(III).…”

“…Hence, modification of GO and chitosan was investigated by many authors for the recovery of REEs and neodymium in particular. 23 − 28 Insertion of magnetite to the GO and CS molecules was done to facilitate the recovery of the composite from aqueous media. The magnetic chitosan@graphene oxide composite (MCh@GO) was really investigated by many authors for the sorption of heavy metals such as Ni 2+ , Zn 2+ , Co 2+ , Pb 2+ , Hg 2+ , Cu 2+ , and Cr(VI) in addition to the remediation of dyes.…”