Adsorbents based on crown ether functionalized composite mesoporous silica for selective extraction of trace silver

- MS-C-D is an efficient Ag(I) adsorbent to overcome concentrated interfering ions.
- Trace levels of Ag(I) can be selectively adsorbed by MS-C-D adsorbent.
- MS-C-D shows higher adsorption affinity and selectivity coefficient of Ag(I).
- MS-C-D maintains high capacity and selectivity for Ag(I) after 3 cycles.

The selective extraction of trace-level metal ions from unconventional sources such as wastewaters is a long-standing challenge, due to the large concentration difference between the target metal ions and the interfering ions in the matrix. We show here that an adsorbent based on crown ether functionalized mesoporous silica (MS-C-D) overcomes this limitation for selective sequestration of Ag(I) ion. This new adsorbent has hierarchical structure with large specific area and pore framework, which is conducive to the selective adsorption of trace levels of Ag(I) from a complex solution containing concentrated interfered ions such as Cu(II), Zn(II) and Pb(II) ions. The adsorption affinity (b value of 1.45) and selectivity coefficient (distribution coefficient KD of 1.50 * 105 mL/g) of Ag(I) by using MS-C-D were dramatically higher than many other reported adsorbents (e.g. an Ag(I)-ion-imprinted materials with KD of 392 mL/g) in literatures. Furthermore, the lower ion concentration corresponded to higher selectivity for Ag(I). The hierarchically structure of MS-C-D and the rigid cavity of dibenzo-18-crown-6 contributed to the selective adsorption of Ag(I). The adsorbent keeps high capacity (about 39.8 mg/g) and selectivity for Ag(I) adsorption after three regeneration cycles. This new composite adsorbent is promising in extracting trace levels of Ag(I) from unconventional wastewaters containing high concentrations of interfered ions.

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