Amidoxime Functionalization of Algal/Polyethyleneimine Beads for the Sorption of Sr(II) from Aqueous Solutions.

Yuezhou Wei,Khalid A M Salih,Siming Lu,Toyohisa Fujita,Eric Guibal,Mohammed F Hamza,Thierry Vincent

doi:10.3390/molecules24213893

Yuezhou Wei, Khalid A M Salih + Show 5 more

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https://doi.org/10.3390/molecules24213893

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Abstract

There is a need for developing new sorbents that incorporate renewable resources for the treatment of metal-containing solutions. Algal-polyethyleneimine beads (APEI) (reinforced with alginate) are functionalized by grafting amidoxime groups (AO-APEI). Physicochemical characteristics of the new material are characterized using FTIR, XPS, TGA, SEM, SEM-EDX, and BET. AO-APEI beads are tested for the recovery of Sr(II) from synthetic solutions after pH optimization (≈ pH 6). Uptake kinetics is fast (equilibrium ≈ 60–90 min). Sorption isotherm (fitted by the Langmuir equation) shows remarkable sorption capacity (≈ 189 mg Sr g−1). Sr(II) is desorbed using 0.2 M HCl/0.5 M CaCl2 solution; sorbent recycling over five cycles shows high stability in terms of sorption/desorption performances. The presence of competitor cations is studied in relation to the pH; the selectivity for Sr(II) is correlated to the softness parameter. Finally, the recovery of Sr(II) is carried out in complex solutions (seawater samples): AO-APEI is remarkably selective over highly concentrated metal cations such as Na(I), K(I), Mg(II), and Ca(II), with weaker selectivity over B(I) and As(V). AO-APEI appears to be a promising material for selective recovery of strontium from complex solutions (including seawater).

Highlights

Strontium makes up about 0.03% of Earth’s crust, being mainly present in ores as sulfate and carbonate salts
After functionalization with amidoxime groups (AO-Algal-polyethyleneimine beads (APEI)), the surface becomes more irregular with thin wrinkles and sharp edges
The FTIR and XPS analyses confirm the different steps in the chemical modification of algal/alginate/PEI beads

Summary

Introduction

Strontium makes up about 0.03% of Earth’s crust, being mainly present in ores as sulfate and carbonate salts (celestine and strontianite mineral, respectively). Natural strontium is not recognized as a very toxic element; its chemical properties are very similar to calcium and may cause trouble in the case of excess exposure, especially in the early bone-forming years. This similarity to Ca and Ba is essentially critical because of its competitive assimilation in bones Radioactive 90 Sr accumulates in the human body (including bones) and is excreted difficultly. This intake causes bone sarcoma, leukemia, and soft tissue cancer [2]

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