2-Mercaptoimidazole Covalently Bonded to a Silica Gel Surface for the Selective Separation of Mercury(II) from an Aqueous Solution

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Abstract
Silica gel with a specific surface area of 365 m2·g−1 and an average pore diameter of 60 Å was chemically modified with 2-mercaptoimidazole. The degree of functionalization of the covalently attached molecule, (≡SiO)3(CH2)3—MI, where MI is the 2-mercaptoimidazole bound to the silica surface by a propyl group, was 0.58 mmol·g−1. In individual metal adsorption experiments from aqueous solutions by the batch procedure, the affinity order was HgII « CdII > CuII ∼ ZnII ∼ PbII > MnII at solution pHs between 4 and 7. Due to the high affinity by the sulfur atom, HgII is strongly bound to the functional groups. When solution containing a mixture of HgII, CdII, CuII, ZnII, PbII, and MnII ions was passed through a column packed with the adsorbent, HgII was the only one whose adsorption and elution was not affected by the presence of other ions.