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 degrees 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 impactmass spectrometry (El-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-loacled-thiol [Si-SH]. (C) 2011 Elsevier B.V. All rights reserved.