干湿循环作用下碱渣固化重金属污染土的稳定性研究

发布时间：2018-04-09 05:22

本文选题：重金属污染土　切入点：干湿循环　出处：《合肥工业大学》2017年硕士论文

【摘要】：利用固化/稳定法处理重金属污染土已得到国内外学者的广泛认可,其固化效果显著且经济可行。然而,在复杂多变的自然环境中,干湿交替的气候变化可能会改变固化土体强度及化学稳定性,从而影响土体的固化效果。因此,进行固化重金属污染土在干湿循环作用下的强度、淋滤、微结构等方面的研究,不仅有助于进一步了解固化土体修复机理,也可以对固化土体的长期稳定性做出进一步的预测和维护。基于此,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,以碱渣和水泥固化重金属污染土为研究对象,通过干湿循环试验、强度试验、淋滤试验以及微结构试验,探讨了固化铬/锌污染土在干湿循环作用下的性质变化规律。取得以下主要研究成果:(1)通过对不同类型固化污染土进行强度稳定性研究得出,固化铬污染土随干湿循环次数的增加,累计质量损失的增大呈现先慢后快的趋势,而固化锌污染土则呈现先快后慢的趋势,且总体质量损失锌大于铬;固化铬、锌污染土强度均随干湿循环的作用先增大后减小,前期增长幅度较小,后期降低幅度较大;固化铬污染土强度大于锌污染土,最后两者的强度接近,土体均遭到严重破坏;同级干湿循环作用下,30%固化剂掺量的土体强度大于20%固化剂掺量。(2)通过对干湿循环作用下固化重金属污染土的化学稳定性研究发现,固化锌、铬污染土浸泡液pH值与Ca~(2+)浸出量均随干湿循环的次数增大逐渐减小;对于浸出Ca~(2+)离子总量,固化铬污染试样小于锌试样,固化剂掺量20%的试样小于30%。通过TCLP和半动态淋滤试验发现,TCLP试验中,不同固化剂掺量的固化铬和锌污染土浸出液的pH值均随土样干湿循次数增加逐渐减小;TCLP浸出液中铬、锌的浸出浓度均随干湿循环的作用先减小后增大。铬离子浸出量总体小于锌;半动态淋滤试验中,浸泡液pH值在一个小范围内波动;半动态淋滤试验中,累计离子浸出量随浸泡时间的增加逐渐增加,随试样经受干湿循环次数增多而增大;两种固化土体中的离子扩散系数均随干湿循环次数增加先减小后增大,且锌大于铬。(3)通过SEM和XRD微观分析方法探讨了干湿循环次数、离子类型和固化剂掺量等因素对固化土体的微结构影响。与土体宏观性质改变相互印证,进一步科学完善的解释重金属污染土的固化机理。
[Abstract]:The treatment of heavy metal contaminated soil by solidification / stabilization method has been widely recognized by scholars at home and abroad, and its solidification effect is remarkable and economical and feasible.However, in the complex and changeable natural environment, the soil solidification strength and chemical stability may be changed by the alternate climate change of dry and wet, thus affecting the solidification effect of soil.Therefore, to study the strength, leaching and microstructure of solidified heavy metal contaminated soil under dry and wet cycle is not only helpful to further understand the mechanism of solidified soil remediation.Further prediction and maintenance of long-term stability of solidified soil can also be made.Based on this, this paper takes National Natural Science Foundation Project No. 41172273) and National Natural Science Foundation Project No. 41372281) as the research object, takes alkali slag and cement solidified heavy metal contaminated soil as the research object, through dry-wet cycle test, strength test,Leaching tests and microstructure tests were carried out to investigate the properties of solidified chromium / zinc contaminated soils under dry and wet cycling.Through the study of the strength stability of different types of solidified contaminated soils, it is concluded that with the increase of dry-wet cycles, the cumulative mass loss increases with the increase of dry and wet cycles.On the other hand, the solidified zinc contaminated soil showed a tendency of fast and then slow, and the total loss of zinc was larger than that of chromium, and the strength of solidified chromium and zinc contaminated soil increased first and then decreased with the effect of dry and wet cycle, and the increase range was small in the early stage, and the decrease was larger in the later stage.The strength of solidified chromium contaminated soil is higher than that of zinc contaminated soil, and the strength of the last two soils is close to that of zinc contaminated soil.The soil strength of 30% curing agent is larger than that of 20% curing agent under the same order dry and wet cycle.) the chemical stability of heavy metal contaminated soil solidified under dry and wet cycle is studied, and it is found that zinc is solidified.The pH value of the soaking solution and the leaching amount of Ca~(2 gradually decreased with the increase of the number of dry and wet cycles, and for the total amount of leaching Ca~(2, the amount of solidified chromium contaminated sample was less than that of zinc sample, and the content of solidifying agent was less than 30%.Through TCLP and semi-dynamic leaching tests, it was found that the pH value of the leaching solution of solidified chromium and zinc contaminated soil with different content of curing agent decreased gradually with the increase of dry and wet cycles of soil samples.The leaching concentration of zinc decreased firstly and then increased with the effect of dry and wet cycle.In the semi-dynamic leaching test, the pH value of the solution fluctuated in a small range, and in the semi-dynamic leaching test, the accumulated ion leaching amount increased with the increase of soaking time.The ion diffusion coefficient in both solidified soils decreased first and then increased with the increase of dry and wet cycles, and zinc was larger than chromium. 3) the times of dry and wet cycles were discussed by SEM and XRD microanalysis.The effect of ion type and the amount of curing agent on the microstructure of solidified soil.The mechanism of solidification of heavy metal contaminated soil is explained scientifically and perfectly with the change of macroscopical properties of soil.
【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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