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 SiM hom and SiM het, 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 ± 0.3 and 1.42 ± 0.17 mmol g −1 for SiM het and SiM homt, respectively. These interactions were calorimetrically followed and the thermodynamic data showed the following exothermic enthalpic values: − 23.04 ± 1.4 and − 20.08 ± 1.2 kJ mol −1 for SiM hom and SiM het, respectively. All liquid/solid interface adsorptions were spontaneous in nature and enthalpically driven. Hg(II) adsorption on silica modified with 2-mercaptobenzimidazole.