Preconcentration and speciation of inorganic and methyl mercury in waters using polyaniline and gold trap-CVAAS

Applicability of polyaniline (PANI) has been investigated for the preconcentration and speciation of inorganic mercury (Hg2+) and methyl mercury (CH3Hg+) in various waters (ground, lake and sea waters). Preliminary experiments (batch) with powdered PANI for the quantitative removal of both Hg2+ and CH3Hg+ showed that the retention of Hg2+ was almost independent of pH while a pH dependent trend from pH 1 to 12 was seen for CH3Hg+ with maximum retention at pH > 5. Time dependence batch studies showed that a contact time of 10 min was sufficient to reach equilibrium. The K-d values were found to be similar to 8 x 10(4) and similar to 7 x 10(3) for Hg2+ and CH3Hg+, respectively. Subsequently column experiments were carried out with PANI and the separation of the species was carried out by selective and sequential elution with 0.3% HCl for CH3Hg+ and 0.3% HCl-0.02% thiourea for Hg2+. This was then followed by further pre-concentration of mercury on a gold trap and its determination by CVAAS. The uptake efficiency studies showed that the PANI column was able to accumulate up to 100 mg Hg2+/g and 2.5 mg CH3Hg+/g. This method allows both preconcentration and speciation of mercury with preconcentration factors around 120 and 60 for Hg2+ and CH3Hg+, respectively. The interfering effects of various foreign substances on the retention of mercury were investigated. (c) 2005 Elsevier B.V All rights reserved.