Preparation of xylenol orange functionalized silica gel as a selective solid phase extractor and its application for preconcentration-separation of mercury from waters

A new selective solid phase extractor was prepared from silica gel modified with xylenol orange (SGMXO). The solid phase extractor is stable in 6 mol L−1 HCl, common organic solvents, and pH 1.0-9.0 buffer solutions. In the batch experiments, Hg(II) can be adsorbed on SGMXO at pH 1.0 with 90.0% retention, whereas the retention of other common coexisting metal ions such as Cd(II), Pb(II), Cu(II), Ni(II), Co(II), Mn(II), Zn(II), and Fe(III) is less than 4.1%.. The adsorption equilibration for Hg(II) was achieved within 3 min. At optimum conditions, the adsorption capacity of the extractor is 18.26 μmol g−1 of dry modified silica gel, and the preconcentration factor is as high as 333. The recovery is still higher than 95% for the preconcentration of 10 ng mL−1 Hg(II). The new solid phase extractor has been used for the preconcentration of low level of Hg(II) in surface water, tap water in chemistry laboratory and student's dormitory and a simulated sea water samples, recoveries of 98.2-100.6% were obtained. It is showed that low level of Hg(II) can be effectively preconcentrated by this new selective solid phase extractor.