柱淋滤模式下脱硫石膏中重金属组分的迁移特性

Research into mobility of heavy metals components in FGD gypsum on the basis of column leaching model

采用柱淋滤模式研究了来自武汉和浙江电厂的2个脱硫石膏样品FA1和FA2中Cr、As、Ni、Pb和Hg 5种重金属组分的迁移过程,了解这一过程为脱硫石膏污染防治工作具有指导意义。首先采用改进的Tessier法分级提取脱硫石膏晶体中重金属组分,完成了不同重金属组分赋存形态研究,结果表明重金属组分以氧化物结合态为主,其中FA1中重金属可淋滤态大小为Pb>As>Cr>Ni,而FA2中重金属可淋滤态为As>Pb>Ni>Cr。柱淋滤实验中选择p H值分别为4.0及4.5的醋酸-醋酸钠缓冲溶液为淋滤液,淋滤周期为17 d,得到不同重金属淋出率L随时间的淋出特征。结果表明:在本研究体系中各重金属组分淋出率均随淋滤时间有显著增加;淋滤液酸性增强可促进重金属组分的淋滤溶出;重金属组分赋存形态对重金属淋出迁移过程具有重要影响。脱硫石膏FA1中Cr、As、Ni、Pb、Hg以及脱硫石膏FA2中的Pb、Hg的最高淋出量超过《地表水环境质量标准》,在脱硫石膏资源化应用过程中可能对环境造成危害。

This study investigated the leaching characteristics of Cr,As,Ni,Pb,and Hg wet flue gas desulphurization（ FGD） gypsum from Wuhan and Zhejiang power plants based on the column leaching model. First,the Tessier method was utilized to determine the levels of Cr,As,Ni,Pb,and Hg. The results showed that oxide was the main component in all heavy metal components. Moreover,there was a descending sequence of Pb,As,Cr,and Ni in sample FA1,and of As,Pb,Ni,and Cr in sample FA2 according to mobility characteristics. The buffer solutions of acetic acid and sodium acetate with p H values of 4. 0 and 4. 5 were selected as the leaching solution,and the leaching period was 17 days. Further,the leaching characteristics of each heavy metal component was obtained by leaching rate vs. leaching time. The leaching experimental results indicated that the leaching rate of each heavy metal component increased as the leaching time increased,and could also increase as the p H value of the leaching solution decreased. The occurrence of each heavy metal component significantly influenced the leaching rate. In the leaching solution,Cr,As,Ni,Pb,and Hg ions from sample FA1 and Pb and Hg ions from sample FA2 were below the environmental standards for surface water quality. Thus,the potential disadvantages of heavy metal components on the environment must be considered while utilizing FGD gypsum.