Selective extraction of mercury(II) from water samples using mercapto functionalised-MCM-41 and regeneration of the sorbent using microwave digestion.

Silica sorbents, based on mesoporous crystalline material-41 (MCM-41), were functionalised using mercaptopropyl (MP) or diethylenetriamine (DETA) to extract mercury (II) ions from water. MP-MCM-41 is an extremely efficient and selective sorbent for the removal of mercury (II) from samples of distilled water doped with heavy metal ions and additionally from more complex matrices including tap and river water. In contrast DETA-MCM-41 preferentially removes hard metal ions (chromium, manganese, lead and zinc) over soft metal ions such as mercury. During extraction, the influence of pH on adsorption capacity was examined; a maximum adsorption capacity of 1245 μmol g(-1) was achieved for MP-MCM-41 even at pH values as low as 3. Significantly, a method has been developed for the first time to remove Hg (II) from loaded MP-MCM-41 allowing this analyte to be selectively recovered from water contaminated with a wide range of heavy metal ions. The regeneration method does not disrupt the chelating agent which remains on the surface of the silica permitting reuse of the sorbent in further extractions.