Heavy metal ions extraction from aqueous media using nanoporous silica

Nanoporous silica (NP) was synthesized and modified with thiol moiety [NPSi-SH]. Thermal gravimetric analysis (TGA) of [NPSi-SH] proved its high thermal stability in the temperature range of 25–600 °C. Structural identification of surface modification of [NPSi-SH] was also confirmed on the basis of surface coverage value from the study of thermal desorption method and FT-IR as well as electron impact-mass spectrometry (EI-MS) by the direct insertion probe. A study was performed to explore the metal adsorption, chelating and selectivity properties of [NPSi-SH] toward a series of di- and tri-valent toxic and nontoxic metal ions via determination of the metal capacity and distribution coefficient values. The incorporated selectivity characters of [NPSi-SH] were studied based on determination of the distribution coefficient and separation factor and the results have strongly referred to high affinity toward binding and up-take of anionic and cationic Hg(II) species in all the studied pH range (1.0–7.0). Also, The proposed mechanisms of adsorption of Hg(II) were suggested at different pH. The selective removal and extraction of Hg(II), via micro-column packed with [NPSi-SH], versus other toxic and nontoxic metal ions from drinking tap water samples were also explored. Excellent percentage extraction values of Hg(II) were characterized as 98.1 ± 4.0%, 98.0 ± 4.0% and 97.7 ± 3.0% from water samples buffered to pH 1.0, 2.0 and 7.0 respectively. The other tested metal ions were found to exhibit percentage extraction values of 94.0 ± 5.0% for Cd(II), 93.6 ± 4.0% for Cu(II) and 90.5 ± 5.0% for Zn(II) from pH 7.0 water samples. Different important analytical factors were applied to compare and show superiority of synthesized [NPSi-SH] phase with other previously reported silica gel phases-loaded-thiol [Si-SH].

► Separation factor of thiolated nanoporous silica for different toxic metals were determined.
► Thiolated nanoporous silica has strong affinity toward up-take of anionic and cationic Hg(II) species.
► Selective removal and extraction of Hg(II) via micro-columns.