發(fā)布時間：2018-02-27 21:09

  本文關鍵詞： 電動修復 酸化預處理 鉻渣 土壤污染 形態(tài)分析　出處：《中國地質大學(北京)》2015年碩士論文　論文類型：學位論文

【摘要】：經(jīng)濟的迅猛發(fā)展,提高了人們的生活水平,但也帶來了一系列的環(huán)境問題,其中土壤重金屬污染問題突出。鉻鹽的主要產(chǎn)品品種為重鉻酸鈉和鉻酸酐,是無機化工的主要系列產(chǎn)品之一,鉻鹽和金屬鉻的生產(chǎn)過程,會產(chǎn)生大量的鉻渣,鉻渣的長期堆放,導致了土壤和地下水的嚴重污染,土壤總鉻含量超過10000mg/kg,六價鉻含量也達到了1322 mg/kg。電動修復在土壤原位重金屬修復技術中的占有重要地位,具有高效、節(jié)能、適用范圍廣等特點,在國內外備受關注。根據(jù)課題組前期研究發(fā)現(xiàn),使用電動方法對鉻渣堆放場地受鉻污染土壤進行修復,去除率低下,影響總鉻去除率的主要因素:土壤鉻濃度、堿性、共存污染物種類,鉻主要以沉淀態(tài)和殘渣態(tài)存在,電動過程中沉淀態(tài)和殘渣態(tài)的鉻難以去除。為增加電動修復技術對鉻去除效率,提出了酸化強化-電動修復技術。以國內某化工廠鉻渣堆放場地鉻污染土壤為研究對象,通過改變酸化條件,分析乙酸、檸檬酸和鹽酸的酸化時間、濃度對電動修復鉻污染土壤中鉻去除率的影響,并對土壤中鉻的形態(tài)進行分析。在此基礎上,聯(lián)合PRB修復技術對鉻污染土壤進行修復。通過實驗分析,得出以下結論:(1)酸化預處理-電動強化修復技術可以顯著提高鉻污染土壤中鉻的去除率,其中0.9 mol/L檸檬酸酸化5天組總鉻和六價鉻的去除率由對照組的6.23%、19.01%分別升至26.97%、77.66%;(2)土壤酸化可以將部分鉻由碳酸鹽結合態(tài)轉化為水溶態(tài),提高其去除率;(3)與乙酸組、鹽酸組相比,檸檬酸組鉻的去除率較高,檸檬酸本身也是一種絡合劑,在酸化作用釋放碳酸鹽結合態(tài)鉻的基礎上,檸檬酸能與鉻發(fā)生絡合作用,進一步提升了鉻的去除率;(4)電動修復過程中遷移出土壤的鉻主要以醋酸可提取態(tài)、可還原提取態(tài)和可氧化提取態(tài)為主,殘留鉻的生物可利用性降低;(5)電動/PRB聯(lián)合修復技術可以顯著提高總鉻去除率,EK-11組總鉻去除率達到了33.87%,較采用普通電動修復技術的EK-08組,去除率提高兩倍以上。
[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.
【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X53

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本文編號：1544341