Modification of silica gel by attachment of 2-mercaptobenzimidazole for use in removing Hg(II) from aqueous media: A thermodynamic approach

The compound 2-mercaptobenzimidazole (MBI) was attached onto a silica gel surface by homogeneous and heterogeneous routes. Both silica modification methodologies resulted in similar products, named SiMhom and SiMhet, respectively. These materials were characterized by surface area, infrared, thermogravimetry, and 13C and 29Si NMR spectroscopy. The ability of these materials to remove divalent mercury from aqueous solution was followed by a series of adsorption isotherms adjusted to a modified Langmuir equation. The maximum number of moles adsorbed was determined to be 1.35±0.31.35±0.3 and 1.42±0.17 mmolg−1 for SiMhet and SiMhomt, respectively. These interactions were calorimetrically followed and the thermodynamic data showed the following exothermic enthalpic values: −23.04±1.4−23.04±1.4 and −20.08±1.2 kJmol−1 for SiMhom and SiMhet, respectively. All liquid/solid interface adsorptions were spontaneous in nature and enthalpically driven.

Graphical abstractHg(II) adsorption on silica modified with 2-mercaptobenzimidazole.Figure optionsDownload full-size imageDownload as PowerPoint slide