Feasibility Study on Content Determination of Mercury and Arsenic in High Organic Anthracite by Microwave Digestion-Hydride Generation-Atomic Fluorescence Spectrometry and Mass Spectrometry

The microwave digestion method can be used for most coal samples, but not for those with ultra-high organic matter because they contain multiple complex high molecular organisms due to the high coalification degree and cannot be digested by digestion techniques currently available. In this paper, the conditions for microwave digestion including digestion reagents, temperature and time were investigated. The digestion system suitable for anthracite with high organic content was investigated and the feasibility on determination of total Hg and As by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was investigated. Results show that using nitric acid-sulfuric acid-hydrofluoric acid (6:4:0.5) as the digestion reagent and the digestion temperature of 205℃ for 30 minutes, the anthracite with high organic content can be completely digested due to the key role of sulfuric acid. The detection results of mercury by HG-AFS and ICP-MS were consistent, both recoveries of which reach more than 98%. The result of arsenic by HG-AFS was significantly lower due to incomplete transformation of organic As to inorganic As. Therefore, anthracite with high organic content (81%-90%) can be completely digested to solution by microwave technique, and Hg and As can be determined by ICP-MS. HG-AFS is not an efficient method to analyze mercury.