Synthesis and Characterisation of Sulphur-Functionalised Silica Nanocapsules for Mercury Removal Process

Sulphur functionalized silica nanocapsules (S-SiNC) was successfully synthesised and
characterized as a potential mercury adsorbent. The synthesis of S-SiNC was carried
out using the soft-templating method using cetyl trimethylammonium bromide
(CTAB) as cationic surfactant, toluene as co-solvent, ammonia solution as catalyst,
elemental sulphur as precursor and tetraethyl orthosilicate (TEOS) as the silica base.
The S-SiNC adsorbent was characterized using scanning electron microscope (SEM),
transmission electron microscope (TEM), Fourier transformed infrared spectroscopy
(FTIR) and nitrogen adsorption/desorption analysis. The mercury (Hg) adsorption was
carried out in a batch adsorption process with variation in initial Hg (II) concentration.
The results show that blank SiNC and S-SiNC has a BET surface area in the range of
150-200 m2
/g and all of the adsorbents displays good efficiency in mercury ion
adsorption (qe=107.87 mg/g). The experimental data obtained was found to be fitting
well to the Langmuir isotherm model (R2= 0.979) compared to Freundlich isotherm
model. Thus, the presence of sulphur functional groups, especially elemental sulphur
(ES) in the SiNC, gave a significant enhancement of Hg (II) adsorption capacity.