不同粒径脱硫污泥中汞分布特性及其环境影响

Partitioning and environmental impact of Hg in desulfurizationsludge with different particle diameter

燃煤释放的大量汞部分富集于湿法脱硫(WFGD)系统的脱硫副产物中,尤其是脱硫污泥中。借助X射线衍射仪(XRD)和扫描电镜能谱联用(SEM-EDX)等先进表征手段研究脱硫污泥粒径对内部矿物组成及汞分布的影响。利用汞程序升温脱附(Hg-TPD)方法系统研究了不同粒径脱硫污泥中汞的赋存形态,结果表明脱硫污泥中汞含量远超过脱硫石膏,达到5.652μg/g。脱硫污泥中汞的赋存形态主要有HgS、HgO和HgSO_(4),所占比例分别为47%、49%和5%。随脱硫污泥粒径减小,HgO和HgSO_(4)含量逐渐降低,HgS含量则逐渐增加,在38μm样品中HgS含量超过80%。借助标准浸出程序评估不同粒径脱硫污泥的环境潜在风险,发现脱硫污泥的颗粒粒径和其内部汞赋存形态是影响脱硫污泥中汞浸出能力的主要因素,综合考虑这2种因素粒径74μm的脱硫污泥具有最高的环境潜在威胁,汞浸出量达到3.8μg/g。

Generated from coal combustion,Hg can be found in the products from WFGD system,in particular WFGD sludge.The mineral composition and Hg content were studied by X-Ray diffraction(XRD)and scanning electron microscope energy dispersive X-ray(SEM-EDX)in the present study.The partitioning of Hg species in WFGD sludge with different diameter was investigated by Hg temperature programmed decomposition method(Hg-TPD)in the present study.The results indicate that the Hg content in WFGD sludge is 5.652μg/g which is much higher than that in gypsum.Hg species including HgS,HgO,and HgSO_(4) are identified in the WFGD sludge whose proportions are 47%,49%,and 5%,respectively.The proportions of HgO and HgSO_(4) decreases when the particular diameter decreased,while the proportion of HgS increased.The percentage of HgS reached over 80%in the sample of 38μm.Also,the environmental potential risk is evaluated by applying the standard toxicity characteristic leaching procedure.The results indicate that the particular diameter and the Hg species constitution are the dominant factors that influence Hg leaching ability.The sample 74μm exhibites the highest environmental potential risk with Hg leaching concentration 3.8μg/g.