Abstract
Nanosilica (NSi) was functionalized by oxalic acid (NSi-Ox) and tartaric acid (NSi-Tar) using solvent-free microwave-assisted approach. The two surface-modified NSi sorbents were characterized by Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, and thermal gravimetric analysis. NSi-Ox and NSiTar sorbents were examined for the removal of Co(II) from aqueous solutions by the batch adsorption technique. Removal of Co(II) was carried out at different controlling parameters such as pH, contact time, sorbent mass, and interfering ions. The maximum Co(II) uptake values were identified as 733.3 and 1026.7 mu mol g(-1) for NSi-Ox and NSiTar, respectively, and these were higher than the identified value by NSi sorbent (440 mu mol g(-1)). This trend is mainly due to the surface functionalization with several active groups. The adsorption isotherms were evaluated using Langmuir and Freundlich models and the results were better fitted to the Langmuir model (R-2 = 0.983 and 0.989 for NSi-Ox and NSi-Tar, respectively). Kinetic studies were performed and the experimental data were found in good agreement with the pseudo-second-order model. The thermodynamic parameters were also determined. The potential applications of NSi sorbents for removal of Co(II) from drinking tap water and sea water samples were successfully achieved using microcolumn studies.