土壤焙烧过程中碘的释放及其环境意义

研究了温度和焙烧时间对黄壤和红壤碘排放的影响。随着焙烧时间的增加,土壤中碘的逸出率呈上升趋势,900℃时焙烧90min后碘的排放基本达到平衡。土壤中的碘主要以吸附形式存在,各种吸附剂对碘的吸附强度不同,从105℃开始即有部分碘被释放出来,随着温度的升高,更多的碘被解吸、释放。焙烧90分钟,1100℃时碘的逸出基本达到平衡,红壤和黄壤碘的逸出率分别为99.85%和98.52%。500℃和900℃左右是土壤碘释放的两个高峰,分别对应着高岭石和蒙脱石的脱羟基作用,这表明有相当一部分I-取代粘土矿物晶格中的OH-而进入了晶格内部。粘土砖生产过程中碘的排放系数约为97.56%,通过计算得出我国粘土砖生产每年向空气中排放4100t碘,其对生态环境与人体健康有重要影响。

Iodine Emission during the Soil Baking Process and Its Environmental Significance

The effects of temperature and baking time on iodine emission from yellow soil and red soil were studied in this paper. The release rate of iodine in soil increased with increasing baking time. In 90 min, the iodine emission tended to reach a balance when soil was baked at 900℃. Most iodine was adsorbed on the various constituents of soil. The adsorption affinities of various adsorbents are different. Some iodine in soil was liberated at 105℃. More iodine was desorbed and released at higher temperature. The emission ratio of iodine reached a balance at 1100℃ when soil was baked for 90 min, 99.85% for red soil and 98.52% for yellow soil, respectively. The iodine was intensely liberated from the soil at 500℃ and 900℃, which represented the dehydroxylation effect of kaolinite and montmorillonite, respectively. This suggests that substantive I- replaces OH- in the lattice of clay minerals. The emission ratio of iodine in the clay bricks making was about 97.56%. It is estimated that 4100 tons of iodine were discharged into the air from the clay bricks making every year in China, which has a great effect on the ecological environment and human health.