煤中碘的淋滤行为研究

Leaching characteristics of iodine in coal

用不同pH值溶液对煤进行动态淋滤实验,用电感耦合等离子体质谱(ICP-MS)测定不同pH值淋滤液在不同时间段获取的淋出液中碘的浓度,以及煤和淋滤后残留煤的高温热水解溶液中碘的含量。结果表明,淋滤液pH值、淋滤时间、煤中碘的赋存形态及在煤中的赋存部位对碘的淋出有重要影响。淋滤液的酸性越强,煤中碘的淋出越多,pH值为2.0和pH值为4.0溶液对煤中碘的淋出率(η)分别为7.22%和6.20%;但pH值为2.0溶液的淋出液中碘的量小于pH值为4.0溶液的淋出液中碘的量,其百分率(wx)分别为1.920 0%和5.420 0%。pH 2.0淋滤液,在前30 h内淋出液中碘的平均浓度为10.9μg/L;而pH值为4.0淋滤液,在前110 h内淋出液中碘的平均浓度为10.6μg/L;pH值为6.0和pH值为7.5溶液能淋出煤中碘很少。在酸性溶液作用下,首先被淋出的碘是存在煤颗粒表面少量的水溶态和离子交换态碘及大部分碳酸盐态和铁锰氧化物结合态碘,然后煤基质内部的部分水溶态和离子交换态碘及少量的碳酸盐结合态及铁锰氧化物结合态碘等才被淋出。

The dynamic leaching experiments were carried out by different pH solutions in order to investigate the leaching behaviour of iodine in coal. Based on the contents of iodine in coal, residual and different leachates measured by inductively coupled plasma spectrometry （ICP-MS）, the leaching rate （η） of coal and concentration of iodine （c） in leachate were calculated. The results show that the modes of occurrence and sites of iodine in coal, leaching time, and pH play important roles in controlling the leaching behavior of iodine. In limited time, the released iodine from coal increases with the rise of acidity of leaching solution, with leaching rates （η） of iodine from coal leached by pH 2.0 and pH 4.0 are 7.22% and 6.20%, respectively. However, the leaching rate of iodine in leachate （wx） leached by solution of pH 2.0 （ 1.92% ） is less than that of pH 4.0 （5.42%）. The average iodine concentration in leachate leached by pH 2.0 and pH 4.0 solution are 10.9 μg/L in the first 40 h and 10.6 μg/L in the first 110 h, respectively; there is little iodine in the leachates leached by pH 6. 0 and pH 7. 5 solution. Leached by acidic solution, the iodine occurred in little water-soluble and exchangeable, part of carbonate and Fe-Mn oxide forms which are on the surface of coal particles may be released firstly; and then the part of water-soluble and exchangeable iodine which are inside coal matrix come to be released.