Leaching characteristics of bromine in coal

Comparative column leaching experiments were carried out on coal samples collected from Moxinpo Mine in Chongqing, Southwest China. Different acid solutions were used to investigate the leaching behavior and potential environmental effects of bromine in coal. The leaching rate and maximum leached concentration of bromine were calculated on the basis of the concentration of bromine in different resulting leachates measured by inductively coupled plasma mass spectrometry. The results show that the modes of occurrence and locations of bromine in coal, time, and pH value play an important role in controlling the leaching behavior of bromine in coal. At 120 h, the maximum leached concentration and the total leaching rate of bromine in coal increased with an increase in the acidity of the leaching solution. The amount of bromine released from coal leached at a pH of 2 accounted for 80.65% of its total leached amount for 40 h, whereas it was 89.42% at a pH of 4 for 50 h. When leached by an acidic solution, the bromine present in carbonate and Fe–Mn oxides located on the surface of coal particles may be released first, followed by the bromine in water-soluble and exchangeable forms in the interior of the coal matrix. The experiment showed that the bromine in coal may be leached out by acidic rain and enters the surrounding soil and surface water, resulting in the enrichment of bromine in the environment.