Highly dispersed amorphous nano-selenium functionalized carbon nanofiber aerogels for high-efficient uptake and immobilization of Hg(II) ions.

Owing to the strong Hg-Se interaction, Se-containing materials are promising for the uptake and immobilization of Hg(II) ions; compared with metal selenides or selenized compounds, elemental Se contains the highest ratio of Se. However, it remains a challenge to fully expose all the potential Se binding sites and achieve high utilization efficiency of elemental Se. Through rational design on the structure, dispersity, and size of materials, Se/CNF aerogels composed of abundant well-dispersed and amorphous nano-Se have been prepared and applied for the high-efficient uptake and immobilization of Hg(II) ions. The well-dispersion of nano-Se increases the exposure of Se sites, the amorphous structure benefits the easy cleavage of Se-Se bonds, the 3D porous networks of aerogels permit fast ions transport and easy operation. Benefiting from the combination effect of strong Hg-Se interaction and sufficient exposure of Se-enriched sites, the Se/CNF aerogels demonstrate strong binding ability (Kd = 3.8 ×105 mL·g-1), high capacity (943.4 mg·g-1), and preeminent selectivity (αMHg > 100) towards highly toxic Hg(II) ions. Notably, the utilization efficiency of Se in Se/CNF aerogels is as high as 99.5%. Moreover, the strong Hg-Se interaction and extraordinary stability of HgSe could minimize the environmental impact of the spent Se/CNF adsorbents after its disposal.