EXAFS and DFT study of the cadmium and lead adsorption on modified silica nanoparticles

• Modified silica nanoparticles were prepared and characterized by FTIR and 13C NMR.
• Isotherms for the adsorption of Cd2+ and Pb2+ ions on the particles were obtained.
• Pb–N and Pb–C distances on the particles were obtained by EXAFS.
• DFT calculations supported the experimental data.
• Hybrid nanoparticles by precipitation allowed the easy removal of the nano-sorbents.

Silica nanoparticles of 7 nm diameter were modified with (3-aminopropyl) triethoxysilane (APTES) and characterized by CP-MAS 13C and 29Si NMR, FTIR, zeta potential measurements, and thermogravimetry. The particles were shown to sorb successfully divalent lead and cadmium ions from aqueous solution. Lead complexation with these silica nanoparticles was clearly confirmed by EXAFS (Extended X-ray Absorption Fine Structure) with synchrotron light measurements. Predicted Pb–N and Pb–C distances obtained from quantum-chemical calculations are in very good agreement with the EXAFS determinations. The calculations also support the higher APTES affinity for Pb2+ compared to Cd2+.

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