Synthesis and characterization of thiol-functionalized silica nano hollow sphere as a novel adsorbent for removal of poisonous heavy metal ions from water: Kinetics, isotherms and error analysis

In this study, a strategy has been provided for the preparation of silica nano hollow spheres and its functionalization with the thiol group. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, N2 adsorption and Fourier transform infrared spectroscopy have been used to characterize the structure of nanoparticles before and after functionalization. This new synthesized nano hollow sphere was applied to remove heavy toxic metals such as Hg2+, Pb2+ and Cd2+ from water samples. The effect of initial concentration of heavy metals and interaction time were investigated in batch mode. In order to determine the best fit model for each system, non-linear regressions was carried out. For this, three error functions were applied to predict the optimum model. The goodness of fit of experimental data was observed with Sips and Redlich–Peterson isotherms. The pseudo-second order kinetic model represented our experimental data very well. Adsorption data showed that the adsorption capacity of thiol functionalized silica nano hollow sphere (thiol-SNHS) for Hg2+ is higher than Pb2+ and Cd2+.

► Novel functionalized nano silica was synthesized for elimination of heavy metal ions.
► Synthesized nano adsorbent showed spherical and uniform shape with approximately 70 nm diameters.
► The rate of adsorption follows pseudo-second order rate equation.
► Adsorption equilibrium data obeyed from the Sips and Redlich–Peterson isotherms.
► The adsorption tendency of ions decreased in the following order: Hg(II) > Pb(II) > Cd(II).