Selective capture of cesium and thallium from natural waters and simulated wastes with copper ferrocyanide functionalized mesoporous silica

Abstract

Copper(II) ferrocyanide on mesoporous silica (FC-Cu-EDA-SAMMS) has been evaluated against iron(III) hexacyanoferrate(II) (insoluble Prussian Blue) for removing cesium (Cs(+)) and thallium (Tl(+)) from natural waters and simulated acidic and alkaline wastes. From pH 0.1-7.3, FC-Cu-EDA-SAMMS had greater affinities for Cs and Tl and was less affected by the solution pH, competing cations, and matrices. SAMMS also outperformed Prussian Blue in terms of adsorption capacities (e.g., 21.7 versus 2.6 mg Cs/g in acidic waste stimulant (pH 1.1), 28.3 versus 5.8 mg Tl/g in seawater), and rate (e.g., over 95 wt% of Cs was removed from seawater after 2 min with SAMMS, while only 75 wt% was removed with Prussian Blue). SAMMS also had higher stability (e.g., 2.5-13-fold less Fe dissolved from 2 to 24 h of contact time). In addition to environmental applications, SAMMS has great potential to be used as orally administered drug for limiting the absorption of radioactive Cs and toxic Tl in gastrointestinal tract.

Figure 1

Chemical structures of FC-Cu-EDA-SAMMS and Prussian Blue.

Figure 2

Cs adsorption capacity of FC-Cu-EDA-SAMMS and Prussian Blue, measured in filtered seawater (pH 7.8), S/L of 0.1 g/L, dashed lines represent Langmuir isotherm models.

Figure 3

Tl adsorption capacity of FC-Cu-EDA-SAMMS and Prussian Blue, measured in filtered seawater (pH 7.8), S/L of 0.1 g/L, dashed lines represent Langmuir isotherm models.

Figure 4

Sorption kinetics of Cs from filtered seawater (pH 7.7) using FC-Cu-EDA-SAMMS and Prussian Blue, S/L of 1.0 g/L.

Figure 5

Sorption kinetics of Tl from filtered seawater (pH 7.7) using FC-Cu-EDA-SAMMS and Prussian Blue, S/L of 1.0 g/L.

Figure 6

The dissolved Cu and Fe from FC-Cu-EDA-SAMMS and dissolved Fe from Prussian Blue as a function of contacting time between the material and seawater (pH 7.7), S/L of 1.0 g/L.