氯盐诱导汞污染土壤热脱附过程汞挥发性质的研究

发布时间：2018-05-03 23:08

  本文选题：氯盐 + 热脱附　； 参考：《北京化工大学》2015年硕士论文

【摘要】：土壤是人类赖以生存的根基,随着汞矿开采、氯乙烯生产、有色金属冶炼等工业过程,土壤汞污染已经日趋严重。本文在常规热脱附修复技术基础上提出“氯盐诱导汞污染土壤热脱附修复技术”,通过添加氯盐的方式将土壤污染物中难于热脱附去除的HgS、HgO、HgS04等化合物转化为热脱附温度范围低的HgCl2或HgCl,达到降低热脱附温度,缩短热脱附时间的目的。本文首先向HgS、HgO、HgSO4三种汞化合物中分别加入NaCl,CaCl2, MgCl2, NH4Cl, FeCl3五种氯盐反应后热重分析,发现NH4Cl与FeCl3对三种汞化合物热脱附促进作用最明显,在200℃～300℃范围有明显的失重过程,通过自配含单一汞化合物土壤XRD分析可知有HgCl2或者HgCl生成,达到了促进HgS、HgO、HgSO4热挥发的目的。其次,通过不同氯盐添加方式对热脱附总汞去除率的影响对比,发现“湿法-搅拌-冷干”处理效果最好,相较于直接加氯盐处理总汞去除率提高了10%以上；五种不同来源的污染土壤加入氯盐处理后发现,NH4Cl适合汞触媒回收、PVC生产与氯碱生产污染土壤的热脱附除汞,200℃,1h时总汞去除率分别提高了16.96%、12.07%、36.93%,FeCl3处理后汞矿区自然土壤与原生汞生产污染土壤总汞去除率分布提高了34.78%、27.66%；随着温度、停留时间的增加,氯盐诱导热脱附在200℃,1h以后优势逐渐减小,对比发现200℃、1h更利于氯盐诱导方式对汞污染土壤的修复,总汞去除率在加入氯盐后提高了12%以上,含汞盐泥污染土壤在加入NH4Cl处理后更提高了36.93%。最后,对氯盐诱导热脱附后产生的白色晶体进行热重分析与XRD分析,确定热脱附挥发产物主要由HgCl2与HgCl组成。应用HSC Chemistry软件对各反应△G进行计算,发现对于任一汞化合物,△G (FeCl3) 0, NH4Cl与HgO、HgSO4在自然条件下即能发生反应,生成HgCl2,但是与HgS在500℃以后才能反应,HgO与NH4Cl反应生成的NH3,NH3与HgCl2反应能够生成HgCl。
[Abstract]:Soil is the foundation of human survival. With mercury mining, vinyl chloride production, non-ferrous metal smelting and other industrial processes, soil mercury pollution has become more and more serious. In this paper, based on the conventional thermal desorption and remediation techniques, a new method of thermal desorption remediation for mercury contaminated soils induced by chloride salt was proposed. By adding chlorine salt, some compounds such as HgSU HgS04, which are difficult to be desorbed and removed by thermal desorption, are transformed into HgCl2 or HgCl4 with low thermal desorption temperature, which can reduce the thermal desorption temperature and shorten the desorption time. In this paper, the thermogravimetric analysis of three kinds of mercury compounds, NaCl-CaCl _ 2, MgCl _ 2, NH _ 4Cl _ 4 and FeCl3, respectively, was carried out. It was found that NH4Cl and FeCl3 promoted the thermal desorption of the three mercury compounds most obviously, and there was an obvious weight loss process in the range of 200 鈩，

本文编号：1840492