Abstract
A double-imprinted polymer exhibiting high sensitivity for mercury(II) in aqueous solution is presented. Polymer particles imprinted with mercury(II) were synthesised by copolymerising the functional and cross-linking monomers, N’–[3– (Trimethoxysilyl)–propyl]diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS). A double-imprinting procedure employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer, was adopted. The imprinted polymer was characterised by FTIR, scanning electron microscopy (SEM) and the average size determined by screen analysis using standard test sieves. Relative selective coefficients (k`) of the imprinted polymer evaluated from selective binding studies between Hg 2+ and Cu 2+ or Hg 2+ and Cd 2+ were 10 588 and 3 147, respectively. These values indicated highly-favoured Hg2+ extractions over the 2 competing ions. The results of spiked and real water samples showed high extraction efficiencies of Hg 2+ ions, (over 84%) as evaluated from the detected unextracted Hg 2+ ions by ICP-OES. The method exhibited a dynamic response concentration range for Hg 2+ between 0.01 and 20 µg/ml, with a detection limit (LOD, 3σ) of 0.000036 µg/ml (36 ng/l) that meets the monitoring requirements for the USA EPA of 2 000 ng/l for Hg 2+ in drinking water. Generally, the data (n=10) had percentage relative standard deviations (%RSD) of less than 4%. Satisfactory results were also obtained when the prepared sorbent was applied for the pre-concentration of Hg2+ from an aqueous certified reference material. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre–concentration of mercury(II) ions in aqueous environments.
Highlights
In recent years the release of various harmful heavy metal ions into the environment has attracted great attention worldwide because of their toxicity and widespread use
There are currently some sensitive instruments to detect mercury(II), the most widely used methods for analysing these harmful ions employ inductively-coupled plasma optical emission spectroscopy (ICP-OES; Leopold et al, 2009) and atomic absorption spectroscopy (AAS; Detcheva and Grobecker, 2006), but their sensitivity and selectivity are usually insufficient for direct determination of these contaminants at very low concentration levels in complex matrices of environmental samples
Spectroscopic and physical characteristics of the polymer material were in agreement with those reported in literature (Wu et al, 2007)
Summary
In recent years the release of various harmful heavy metal ions into the environment has attracted great attention worldwide because of their toxicity and widespread use. A large kvalue means selectivity of the prepared polymer material relative to the competing ions is high. Preparation of the mercury(II) ion-imprinted polymer and removal of the print species (templates)
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