酸化强化—电动修复铬渣场地污染土壤试验研究

发布时间：2018-02-27 21:09

本文关键词： 电动修复酸化预处理铬渣土壤污染形态分析　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：经济的迅猛发展,提高了人们的生活水平,但也带来了一系列的环境问题,其中土壤重金属污染问题突出。铬盐的主要产品品种为重铬酸钠和铬酸酐,是无机化工的主要系列产品之一,铬盐和金属铬的生产过程,会产生大量的铬渣,铬渣的长期堆放,导致了土壤和地下水的严重污染,土壤总铬含量超过10000mg/kg,六价铬含量也达到了1322 mg/kg。电动修复在土壤原位重金属修复技术中的占有重要地位,具有高效、节能、适用范围广等特点,在国内外备受关注。根据课题组前期研究发现,使用电动方法对铬渣堆放场地受铬污染土壤进行修复,去除率低下,影响总铬去除率的主要因素:土壤铬浓度、碱性、共存污染物种类,铬主要以沉淀态和残渣态存在,电动过程中沉淀态和残渣态的铬难以去除。为增加电动修复技术对铬去除效率,提出了酸化强化-电动修复技术。以国内某化工厂铬渣堆放场地铬污染土壤为研究对象,通过改变酸化条件,分析乙酸、柠檬酸和盐酸的酸化时间、浓度对电动修复铬污染土壤中铬去除率的影响,并对土壤中铬的形态进行分析。在此基础上,联合PRB修复技术对铬污染土壤进行修复。通过实验分析,得出以下结论:(1)酸化预处理-电动强化修复技术可以显著提高铬污染土壤中铬的去除率,其中0.9 mol/L柠檬酸酸化5天组总铬和六价铬的去除率由对照组的6.23%、19.01%分别升至26.97%、77.66%;(2)土壤酸化可以将部分铬由碳酸盐结合态转化为水溶态,提高其去除率;(3)与乙酸组、盐酸组相比,柠檬酸组铬的去除率较高,柠檬酸本身也是一种络合剂,在酸化作用释放碳酸盐结合态铬的基础上,柠檬酸能与铬发生络合作用,进一步提升了铬的去除率;(4)电动修复过程中迁移出土壤的铬主要以醋酸可提取态、可还原提取态和可氧化提取态为主,残留铬的生物可利用性降低;(5)电动/PRB联合修复技术可以显著提高总铬去除率,EK-11组总铬去除率达到了33.87%,较采用普通电动修复技术的EK-08组,去除率提高两倍以上。
[Abstract]:The rapid development of economy has improved people's living standard, but also brought a series of environmental problems, among which the pollution of heavy metals in soil is prominent. The main products of chromium salt are sodium dichromate and chromic anhydride. It is one of the main series products of inorganic chemical industry. The production process of chromium salt and metal chromium will produce a large amount of chromium slag and chromium slag for a long time, resulting in serious pollution of soil and groundwater. The total chromium content of soil is more than 10 000 mg / kg, and the content of hexavalent chromium is 1322 mg / kg. Electric remediation plays an important role in soil in situ heavy metal remediation technology, and has the characteristics of high efficiency, energy saving, wide application range and so on. According to the previous research of our research group, it is found that the removal rate of chromium contaminated soil is low, and the main factors affecting the total chromium removal rate are: soil chromium concentration, alkalinity, and so on. In order to increase the removal efficiency of chromium by electrokinetic remediation technology, it is difficult to remove chromium from the precipitated state and residue state in the electric process. The acidizing augmentation-electric remediation technology was put forward. The acidizing time of acetic acid, citric acid and hydrochloric acid was analyzed by changing the acidizing conditions, taking the chromium contaminated soil in the chromium residue dump of a chemical plant in China as the research object. The effect of concentration on the removal rate of chromium in chromium contaminated soil by electrokinetic remediation, and the analysis of chromium forms in soil. On the basis of this, the remediation of chromium contaminated soil was carried out by combining with PRB remediation technology. The following conclusions are drawn: (1) acidizing pretreatment with electric reinforcement can significantly improve the removal rate of chromium in the polluted soil. The removal rates of total chromium and hexavalent chromium in 0.9 mol/L citric acid acidified group for 5 days were increased from 6.23 ~ 19.01% in control group to 26.97% in control group, respectively.) soil acidification could transform part of chromium from carbonate bound state to water-soluble state, and increase its removal rate by 3%) compared with acetic acid group and hydrochloric acid group. The removal rate of chromium from citric acid group is relatively high. Citric acid itself is also a complexing agent. On the basis of acidizing and releasing carbonate-bound chromium, citric acid can react with chromium. The removal rate of chromium was further improved. During the process of electrokinetic remediation, the main forms of chromium migrated out of the soil were acetic acid extractable, reducible and oxidizable. The bioavailability of residual chromium can be reduced by 5%) the total chromium removal rate of EK-11 group can be significantly increased by 33.87%, which is more than two times higher than that of EK-08 group.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

【参考文献】