Adsorption of Mercury(II), Lead(II), Cadmium(II) and Zinc(II) from Aqueous Solutions using Mercapto‐Modified Silica Particles

This article presents a novel systematic approach to the fabrication of highly functionalized, silica (SiO₂) nanoparticles used for the adsorption of heavy‐metal ions (Hg²⁺, Pb²⁺, Cd²⁺, Zn²⁺). Almost monodispersed silica (SiO₂) nanoparticles with narrow particle size distributions of around 85 ± 5 nm were formed using the Stöber process. The prepared SiO₂ nanoparticles were successfully surface‐treated during a one‐step procedure by the covalent attachment of mercaptopropyl groups onto the surfaces of the SiO₂ nanoparticles. A FTIR spectra analysis confirmed that the binding of the mercaptosilane molecules onto the surface of the silica nanoparticles mediated the Si–O–Si and –SH vibrations. TEM/EDXS micrographs indicated the almost monodispersed and spherical morphology of the prepared product with strong signals of Si and S, thus implying that the coating procedure involving the mercapto groups onto the silica surface had been successfully accomplished. The final results for the heavy‐metal (Hg²⁺, Pb²⁺, Cd²⁺, Zn²⁺) adsorption showed the strongest affinity within the following sequence Hg²⁺ (99.9%) > Pb²⁺ (55.9%) > Cd²⁺ (50.2%) > Zn²⁺ (4%). Adsorption equilibrium was achieved after 1 h for all the analyzed samples.