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October 23, 2025Open Access

Attachment of Tridentate Ligand onto the Polyhedral Oligomeric Silsesquioxanes as an Efficient Strategy to Capture La(III) Ions: A Comparative Study of Homogeneous and Heterogeneous Systems Using Potentiometric Titration

DBDébora de Freitas BrottoUniversidade Federal de Santa Catarina IRIago de Souza ReisState University of Norte Fluminense AHAdolfo HornUniversidade Federal de Santa Catarina

Key Points

Higher formation constants for lanthanum(III) ion complexes indicate stronger ligand interactions.
Surprisingly, modified polyhedral oligomeric silsesquioxanes show effective metal capture with L1 at specific pH levels.
Analysis of adsorption techniques reveals the potential of functionalized materials for sustainable metal recovery strategies.
The study suggests modified matrices provide efficient alternatives for lanthanide ion recovery in heterogeneous systems.

Abstract

Developing sustainable methods for lanthanide ion recovery is a relevant area of research that seeks to promote the efficient reuse of these valuable chemical elements present in several electronic devices. Adsorption techniques using materials functionalized with chelating groups, such as modified Polyhedral Oligomeric Silsesquioxanes (POSS) matrices, may play a crucial role in capturing these metals. This work investigates the coordination of the lanthanum(III) ion with two tridentate organic ligands: bis(pyridin-2-ylmethyl)amine (L1) and (pyridin-2-ylmethyl)(thiophen-2-ylmethyl)amine (L2). The results revealed stronger interactions for L1, with higher formation constants (9.0 for LaL13+ and 16.9 for La(L1)23+) compared to L2 (4.37 for LaL23+). Further studies on ligand L1 attached to silsesquioxane (POSS-L1) showed significant metal ion interactions, showing the formation of LaPOSS-L13+ (81.0%) at pH 5.42 and La(OH)3POSS-L1 above pH 8.0, with a formation constant of 10.33, which is higher than that for free L1. These results demonstrate the efficient binding of La(III) to the POSS-L1 in a heterogeneous system. The modified silsesquioxane matrix presents a promising alternative for lanthanide ion adsorption, contributing to sustainable metal recovery strategies.

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