Issue 26, 2021

A dithizone-anchored silica gel surface, {SiO2}@DZ for the selective sample cleanup of Gd(iii) amidst Fe(iii), Th(iv), and Ce(iv) employing ion pair complexation

Abstract

The SG surface was functionalized with dithizone, R@-{SiO2}n, in a single step for selective sample clean-up and preconcentration of Gd(III) amidst Fe(III), Th(IV), and Ce(IV). Exploiting the differences in pH for extraction/or using selective eluents, the analytes were selectively separated. The sorbent brilliantly preconcentrates the dilute solutions of Gd(III), Fe(III), Th(IV), and Ce(IV) with a high level of enrichment factors at 183.2, 184.0, 184.1, and 182.1, respectively. The sorption process was found to be entropy gaining (ΔS: 0.033 ± 0.001 kJ mol−1 K−1), exothermic (ΔH: −0.098 ± 0.007 kJ mol−1), and spontaneous (ΔG: −9.89 ± 0.31 kJ mol−1). Systematic studies ensure the quantitative sorption of Gd(III), Th(IV), and Ce(IV) at their solution pH 5.75–6.5; while that for Fe(III) was found to be pH 2.25 ± 0.25. The hydroxy complexes [Gd2(OH)2(H2O)8]4+, [Fe2(OH)2(H2O)5]4+, [Ce(OH)2(H2O)4]2+ and [Th(OH)2(H2O)14]2+ exist at their respective sorption pH and being present in the vicinity of the electron-enriched ‘extractor-HOMO’ makes 1 : 1 ion-pair complexes, {extractor-HOMO} : {metal-hydroxy species}n+. The maximum sorption capacity (BTC) was determined from BTC = {amount of HOMO (μmol g−1) × x} = 172 × x μmol g−1 (where x, the degree of polymerization of a particular metal ion at its extraction pH is an integer and its numerical value(s) become(s) 2 for Gd(III)–Fe(III) and 1 for Th(IV)–Ce(IV)). The reusability (1600–1800 cycles) and the maximum sorption capacity (337.8, 331.1, 178.0, and 182.5 μmol g−1, respectively, for Gd(III), Fe(III), Th(IV), and Ce(IV)) of the extractor with a durability of 18 months was outstanding.

Graphical abstract: A dithizone-anchored silica gel surface, {SiO2}@DZ for the selective sample cleanup of Gd(iii) amidst Fe(iii), Th(iv), and Ce(iv) employing ion pair complexation

Article information

Article type
Paper
Submitted
15 Mar 2021
Accepted
02 Jun 2021
First published
16 Jun 2021

New J. Chem., 2021,45, 11672-11688

A dithizone-anchored silica gel surface, {SiO2}@DZ for the selective sample cleanup of Gd(III) amidst Fe(III), Th(IV), and Ce(IV) employing ion pair complexation

R. Sarkar, S. Mondal, B. Hansda, M. Chatterjee and B. Mandal, New J. Chem., 2021, 45, 11672 DOI: 10.1039/D1NJ01265G

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