Bifunctional periodic mesoporous organosilicas with sulfide bridges as effective sorbents for Hg(II) extraction from environmental and drinking waters

Abstract

A well-ordered two-dimensional hexagonal periodic mesoporous organosilica have been prepared with a high content of disulfide groups in the pore wall (PMO-S-S). This material was obtained by co-condensation of bis(triethoxysylilpropyl)disulfide and tetraethyl orthosilicate under acidic conditions, using non-ionic surfactant P123 as the template. In order to obtain bifunctional disulfide-bridged materials (PMO-S-S-MTTZ and PMO-S-S-MP), the PMO-S-S was modified in a second step with the organic derivatives of 5-mercapto-1-methyltetrazole (MTTZ) or 2-mercaptopyridine (MP) with sulphur and nitrogen active groups in their molecular structures. The characterization of the materials was carried out by XRD, TEM and SEM, nitrogen adsorption-desorption isotherms, 13C MAS-NMR, 29Si MAS-NMR, FTIR, elemental and thermogravimetric analysis. All prepared materials showed excellent adsorption efficiency and selectivity for Hg(II). The results confirmed the existence of additional active sulphur and nitrogen groups on the material surface, in addition to the disulfide groups of the framework, gave a significant enhancement of Hg(II) maximum adsorption capacity of the materials, being the highest Hg(II) adsorption capacity obtained 437 mg g−1 at pH 5. The prepared materials could be potential sorbents for the extraction of this heavy metal from environmental and drinking waters.