Chemisorption of lanthanide ions on succinate-functionalized mesoporous silica: An in situ characterization by fluorescence

Analysis of element yield, bacterial community structure and the impact of carbon sources for bioleaching rare earth elements from high grade monazite

Rare earth element (REE) recovery from waste streams, mine tailings or recyclable components using bioleaching is gaining traction due to the shortage and security of REE supply as well as the environmental problems that occur from processing and refining. Four heterotrophic microbial species with known phosphate solubilizing capabilities were evaluated for their ability to leach REE from a high-grade monazite when provided with either galactose, fructose or maltose. Supplying fructose resulted in the greatest amount of REE leached from the ore due to the largest amount of organic acid produced. Gluconic acid was the dominant organic acid identified produced by the cultures, followed by acetic acid. The monazite proved difficult to leach with the different carbon sources, with preferential release of Ce over La, Nd and Pr.

Revisiting carboxylic group functionalization of silica sol-gel materials

The carboxylic chemical group is a ubiquitous moiety present in amino acids, a ligand for transition metals, a colloidal stabilizer, and a weak acidic ion-exchanger in polymeric resins and given this property, it is attractive for responsive materials or nanopore-based gating applications. As the number of uses increases, subtle requirements are imposed on this molecular group when anchored to various platforms for the functioning of an integrated chemical system. In this context, silica stands as an inert and multipurpose platform that enables the anchoring of multiple chemical entities combined through several orthogonal synthesis methods on the interface. Surface chemical modification relies on the use of organoalkoxysilanes that must meet the demand of tuned chemical properties; this, in turn, urges for innovative approaches for having an improved, but simple, organic toolbox. Starting from commonly available molecular precursors, several approaches have emerged: hydrosilylation, click thiol-ene additions, the use of carbodiimides or the reaction between cyclic anhydrides and anchored amines. In this review, we analyze the importance of the COOH groups in the area of materials science and the commercial availability of COOH-based silanes and present new approaches for obtaining COOH-based organoalkoxide precursors. Undoubtedly, this will attract widespread interest for the ultimate design of highly integrated chemical platforms.

Preparation of a mesocellular siliceous foam supported lanthanide-sensitive polymer for the selective adsorption of lanthanides

A ship in bottle nanocomposite was fabricated as a novel adsorbent for lanthanides by immobilizing a lanthanide-sensitive polymer into mesocellular siliceous foam (MCF). The MCF was used as a novel carrier for immobilization of the polymer, and the polymer was synthesized via in situ ring-opening polymerization of 2-methyl-2-oxazoline (MOL) and divinylbenzene (DVB) in the presence of MCFs. The substantially physically modified MCF-based composite exhibited superior adsorptivity and selectivity to lanthanides due to its exceptional properties, which was employed for lanthanide adsorption from aqueous solution by a facile solid-liquid separation procedure. The adsorption of lanthanides by the composite was systematically studied including adsorption parameter investigation and adsorption mechanism evaluation. The adsorption isotherms and kinetics were also investigated and proved to follow the Langmuir model and the pseudo-second-order model. The adsorption thermodynamics study indicated that the adsorption process was thermodynamically favorable, endothermic and spontaneous. The prepared inorganic-organic hybrid composite has superior selectivity and specificity to lanthanides, which can be used for lanthanide enrichment and separation of lanthanides from actinides.