Abstract
A fast, simple and reliable method for Hg determination in green coke and oily sludge samples by atomic fluorescence spectrometry is described. Microwave digestion and extraction procedures were evaluated for highly complex samples of coke and oily sludge. The concentrations of SnCl2 and HCl to promote Hg vapor, were optimized, as well as the concentration of KMnO4, to stabilize the Hg2+ before the atomic vapor formation. Accuracy of the method was evaluated through certified reference material, for green coke, and comparison with cold vapor atomic absorption spectrometry (CV AAS), for oily sludge. Recovery tests were also performed. Limits of detection and quantification were 0.8 and 2.6 µg kg−1, respectively. Ten green coke and nine sludge samples were analysed and Hg concentrations in coke are very low, between 0.005 and 0.065 mg kg−1, but oily sludge samples have high concentrations, ranging from 42.5 to 376.6 mg kg−1, requiring careful management.
Highlights
Mercury is an element harmful to human health and environment and nowadays has received great attention and extensive studies concerning its toxic effects and potential accumulation.[1,2] According to a list of harmful substances organized biennially since 1991 and updated by the Agency for Toxic Substances and Disease Registry (ATSDR) mercury occupies the third position among 275 substances hazardous to human health
Since petroleum coke is very complex with high content of organic matter, it would be possible that other compounds present in this sample were extracted to the solutions generating vapors, interfering with the analyte signal and leading to concentrations higher than expected
This study showed that the extraction procedures are not adequate for Hg extraction from petroleum green coke samples
Summary
Mercury is an element harmful to human health and environment and nowadays has received great attention and extensive studies concerning its toxic effects and potential accumulation.[1,2] According to a list of harmful substances organized biennially since 1991 and updated by the Agency for Toxic Substances and Disease Registry (ATSDR) mercury occupies the third position among 275 substances hazardous to human health. Mercury is found naturally in the environment and occurs in several forms, such as gaseous element in atmosphere and inorganic and organic compounds.[3] release from anthropogenic sources has drastically affected Hg natural cycle through the atmosphere, water bodies and sediments, becoming an important global pollutant.[4] Mercury is naturally present in crude oil and natural gas, whose concentrations are highly dependent on the geological location,[5] but causing a direct negative impact on petroleum industry.[6,7,8,9]. Studies have shown that the major part of Hg in crude oil remains in these two residues.[4,10,11]
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