Speciation of mercury in South African coals |
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Authors: | Julien Lusilao-Makiese Emmanuel Tessier David Amouroux Hlanganani Tutu Luke Chimuka |
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Institution: | 1. Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand , P.Bag X3, WITS 2050, Johannesburg , South Africa;2. Laboratoire de Chimie Analytique, Bio-Inorganique et Environnement (LCABIE-IPREM) , Université de Pau et des Pays de l’Adour , Pau , France |
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Abstract: | Total mercury (HgTOT) concentrations were determined by inductively coupled plasma mass spectrometry (ICP MS) for South African Highveld coals. The distribution of Hg in coals was investigated using a four-stage sequential leaching protocol and isotope dilution/gas chromatography coupled to ICP MS (ID-GC-ICP MS). The results show that HgTOT ranged from 144 to 303?µg?kg?1 with a mean of 199?±?26?µg?kg?1, while HgTOT leached from coals using different solvents ranged between 103 and 310?µg?kg?1 (mean: 218?±?60?µg?kg?1). Hg leaching rates of 53–78% were achieved in crushed coals. Hg0, Hg2+, and CH3Hg+ were identified in all coals. CH3Hg+ in studied coals ranged between 0.1 and 0.4 (mean: 0.2) µg?kg?1. GC ICP MS chromatograms also showed unknown Hg peaks which were identified as other organomercury species such as ethylmercury. Modes of occurrence of Hg in coals were variable with the organic-bound (37–40%) and the sulfide-bound (37–39%) being the dominant mercury forms. Increasing the HCl concentration in the used protocol increased the amount of Hg leached (16%) during this step. |
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Keywords: | mercury speciation organomercury coal GC ICP MS leaching |
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