基于碱渣的重金属污染土固化修复技术与机理研究

发布时间：2018-06-16 00:29

本文选题：重金属污染土 + 固化　；参考：《合肥工业大学》2017年硕士论文

【摘要】：随着我国工业化的快速推进,重金属污染问题日益严峻,重金属污染土修复成为人们最为关注的环境问题之一,基于以往的研究,固化稳定法被认为是处理重金属污染场地最为有效的方法之一。通过寻求新的、具有经济效益的固化剂,并揭示其固定化机理,将会进一步促进固化修复技术的发展,更好地解决实际工程问题。本文以国家自然科学基金项目(No.41172273)和国家自然科学基金项目(No.41372281)为依托,采用水泥和碱渣作为固化剂,分析讨论了固化锌、铬污染土的无侧限抗压强度特性、淋滤特性、电阻率特性、微结构特性及其变化规律。得到的主要结论如下:(1)基于无侧限抗压强度结果,无侧限抗压强度会随着养护龄期的增大而增大,随着初始重金属离子浓度的增加而降低;在较高重金属浓度下,养护后的强度仍能达到美国对重金属污染土的修复标准0.35MPa;固化铬污染土无侧限抗压强度高于固化锌污染土的无侧限抗压强度。(2)TCLP淋滤试验结果表明,浸出液中重金属离子浓度随着养护龄期的增大而降低,随着初始重金属离子掺量增加而增大;根据U.S.EPA的TCLP试验规定,滤出液中锌离子浓度的最高限值为10mg/L,铬离子浓度的最高限值为5mg/L,在较低重金属离子浓度下,滤出液中锌、铬离子溶出量均能达到环境要求,在高浓度时,部分固化剂配比掺量下的锌离子的浸出量未能达到环境要求。(3)基于无侧限抗压强度和淋滤试验结果,水泥和碱渣固化铬污染土的固化效果比固化锌污染土效果要好,主要是因为锌离子对水化反应阻碍作用明显,铬离子更易以络合物沉淀的形式填充在土体颗粒孔隙中。(4)基于无侧限抗压强度和TCLP淋滤试验结果:对于铬污染土,较低浓度下(Cr0.1、Cr0.5),最优固化剂掺量配比:固化剂总掺量20%,水泥碱渣配比2:8。较高浓度下(Cr1):固化剂总掺量30%,水泥碱渣配比3:7;对于固化锌污染土,较低浓度下(Zn0.1、Zn0.5),最优固化剂掺量配比:固化剂总掺量30%,水泥碱渣配比5:5。较高浓度下(Zn1):固化剂掺量30%,水泥碱渣配比3:7。(5)固化土体的平均电阻率随着养护龄期的增加而增大。水泥掺量一定,碱渣掺量提高,平均电阻率越高。平均电阻率随着初始重金属离子掺量增大而降低。电阻率与无侧限抗压强度正相关,与淋滤液重金属浓度负相关。电阻率增大,主要是因为水化反应产物吸附、包裹、沉淀重金属离子并填充在孔隙内部,土体变得致密,使得土体连通性变差、孔隙液中游离的阳离子变少。(6)基于扫描电镜结果,随着养护龄期的增大,CSH、CAH和AFt等水化产物增加。Zn~(2+)对水化反应具有明显的阻碍作用,土体中除了少量的Ca(OH)_2之外,几乎看不到水化产物生成;XRD试验结果表明随着养护龄期的增加,水化产物含量增加,重金属离子含量降低,水化产物增多,宏观表现为土体无侧限抗压强度增大,重金属离子固化效果增强,土体导电性能变差,电阻率增大。
[Abstract]:With the rapid development of industrialization in China, the problem of heavy metal pollution is becoming more and more serious. Remediation of heavy metal contaminated soil has become one of the most concerned environmental problems. Solidification stabilization method is considered to be one of the most effective methods to deal with heavy metal contaminated sites. By looking for new and economically effective curing agents and revealing their immobilization mechanism, the development of curing and repairing technology will be further promoted and the practical engineering problems will be solved better. Based on National Natural Science Foundation Project No. 41172273) and National Natural Science Foundation Project No. 41372281), using cement and alkali slag as curing agent, the characteristics of unconfined compressive strength and leaching of solidified zinc and chromium contaminated soil are analyzed and discussed in this paper. Electrical resistivity, microstructure and its variation. The main conclusions are as follows: (1) based on the results of unconfined compressive strength, the unconfined compressive strength increases with the increase of curing age and decreases with the increase of initial concentration of heavy metal ions. The strength after curing can still reach the standard of 0.35 MPa for heavy metal contaminated soil, the unconfined compressive strength of solidified chromium contaminated soil is higher than that of zinc contaminated soil, and the results of TCLP leaching test show that the strength of cured chromium contaminated soil is higher than that of zinc contaminated soil. The concentration of heavy metal ions in leaching solution decreases with the increase of curing age and increases with the increase of initial heavy metal ion content. The maximum limit of zinc ion concentration in filtrate is 10 mg / L, and the highest limit value of chromium ion concentration is 5 mg / L. At low heavy metal ion concentration, the leaching amount of zinc and chromium ions in filtrate can meet the environmental requirements. Based on the unconfined compressive strength and leaching test results, the solidification effect of cement and alkali slag solidified chromium contaminated soil is better than that of zinc contaminated soil. The main reason is that zinc ion has obvious hindrance to hydration reaction, chromium ion is more likely to be filled in soil particle pores in the form of complex precipitation) based on unconfined compressive strength and TCLP leaching test results: for chromium contaminated soil, At lower concentration, the optimum ratio of solidifying agent is 20%, and the ratio of cement alkali slag is 2: 8. At higher concentration, the total amount of curing agent is 30, and the ratio of cement and alkali slag is 3: 7. For the soil contaminated with zinc, the optimum ratio of the amount of solidified agent is 30%, and the ratio of cement and alkali slag is 5: 5%. The average resistivity of solidified soil increases with the increase of curing age when the content of curing agent is 30 and the ratio of cement and alkali slag is 3: 7. 5. The higher the content of alkali slag is, the higher the average resistivity is. The average resistivity decreases with the increase of initial heavy metal ion content. The resistivity was positively correlated with the unconfined compressive strength and negatively correlated with the concentration of heavy metals in leachate. The resistivity increases mainly because the hydration reaction product adsorbs, encapsulates, precipitates heavy metal ions and fills in the pores, so that the soil becomes compact and makes the soil less connected. On the basis of SEM results, the hydration products such as CSHH CAH and AFT increased with the increase of curing age. The XRD results showed that with the increase of curing age, the hydration product content increased, the heavy metal ion content decreased, and the hydration product increased. The solidification effect of heavy metal ions is enhanced, the conductivity of soil becomes worse and the resistivity increases.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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