Arsenic in coal of the Thar coalfield, Pakistan, and its behavior during combustion.

The aim of the current study is to evaluate the occurrence of arsenic in coal collected from Thar coalfield, Pakistan, and its behavior during the combustion. Fractionation of arsenic (As) in coal samples was carried out by Community Bureau of Reference sequential extraction scheme (BCR-SES) and single-step-based BCR method (BCR-SS). These methods are validated using the certified reference material of sediment BCR 701 and standard addition method. The stepwise fractions of As in laboratory-made ash (LMA) have been also investigated. The extractable As content associated with different phases in coal and LMA samples were analyzed by electrothermal atomic absorption spectrophotometer. The extraction efficiency of As by BCR-SS was slightly higher than BCR-SES, while the difference was not significant (p < 0.05). The BCR-SS method is a time-saving method because it can reduce the extraction time from 51 to 22 h. The As contents in LMA revealed that during combustion of the coal, >85 % of As may be released into atmosphere. The relative mobility of As in the coal samples was found in increasing order as follows: oxidizable fraction < reducible fraction < acid soluble fraction. The total and extractable As obtained by BCR-SES and BCR-SS were higher in coal samples of block III as compared to block V (p > 0.05).