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重金属污染土壤原位钝化稳定性研究

发布时间:2018-02-28 05:52

  本文关键词: 重金属 原位钝化修复 稳定性 出处:《山东师范大学》2015年硕士论文 论文类型:学位论文


【摘要】:随着土壤重金属污染的日益严重,重金属污染土壤的修复已经成为环境问题的热点。原位钝化修复技术是一种向土壤中添加钝化剂,通过钝化剂对重金属的吸附、沉淀、络合、离子交换和氧化还原等一系列反应,以降低重金属的可迁移性和生物有效性的技术。因该技术成本低、修复效率高、且操作简单,对于中低浓度污染土壤的修复具有较好的应用前景。然而该技术致命性弱点是经钝化稳定后的重金属仍留存在土壤中,只是降低了重金属在土壤中的可迁移性和生物有效性,随时间的延长或环境条件的变化,重金属有再次活化的威胁。 本文从钝化剂本身稳定性和钝化剂与重金属结合稳定性两方面来研究原位钝化修复的稳定性。选取以交换吸附机理为主的粘土矿物—钠基膨润土和螯合吸附机理为主的—改性纳米黑碳两种钝化剂,通过模拟实验和培养实验研究钝化剂本身的热稳定性、化学稳定性(化学氧化稳定性和酸碱稳定性)、生物学稳定性;通过吸附解吸实验研究钝化剂与重金属结合的稳定性及其影响因素;通过盆栽实验研究钝化剂在实际应用中的稳定性。其目的是为钝化剂实际应用于原位钝化修复重金属污染土壤提供理论依据。 本文获得的主要研究结果如下: 选取改性纳米黑碳为钝化材料研究其本身稳定性,结果发现:(1)改性纳米黑碳的热稳定性很好,利用热重分析仪将改性纳米黑碳从室温逐步加热到700℃,改性纳米黑碳的质量仅降低13.01%。(2)改性纳米黑碳的化学稳定性强。利用333mmo·L-1的KMnO4对改性纳米黑碳进行氧化24小时后,达到最大降解率仅为4.22%。改性纳米黑碳的酸碱稳定性较强,用不同酸碱度的溶液对改性纳米黑碳进行酸碱腐蚀,pH为2时,降解率为1.933%,pH为12时,降解率为5.334%。(3)改性纳米黑碳在浓度低于1×105cfu·mL-1的枯草芽孢杆菌作用下生物学稳定性较好。当浓度高于1×105cfu·mL-1时,随着枯草芽孢杆菌浓度增高生物学稳定性变差,在浓度为1×107cfu·mL-1下培养30天时,改性纳米黑碳的最大降解率为11%。改性纳米黑碳的生物降解作用大于化学氧化作用。 选取以交换吸附机理为主的粘土矿物—钠基膨润土和螯合吸附机理为主的—改性纳米黑碳两种钝化剂,选择Cu和Cd两种重金属,通过吸附动力学、吸附等温线实验研究两种材料对两种重金属的吸附特性。结果发现,改性纳米黑碳和钠基膨润土对Cu2+和Cd2+的吸附可以用准二级动力学和Langmuir方程很好的拟合。重金属在钝化剂上的吸附分为快慢两个阶段。用Langmuir方程计算出改性纳米黑碳对Cu2+和Cd2+的最大吸附量分别为23809mg·kg-1和24390mg·kg-1,钠基膨润土对Cu2+和Cd2+的最大吸附量分别为4681mg·kg-1和5356mg·kg-1。Freundlich拟合出的n值均大于1,表明两种重金属在两种吸附剂上均为优惠吸附。改性纳米黑碳对两种重金属的吸附能力大于钠基膨润土,Cu2+在两种钝化剂上的吸附能力大于Cd2+。 用0.01mol·L-1CaCl2在不同环境条件下对吸附了重金属的两种材料进行解吸,结果发现,温度和盐离子浓度对解吸率的影响不大,说明钝化稳定性受温度和盐离子浓度的影响不大;pH对解吸率的影响很大,随着pH的降低解吸率迅速增大,说明土壤pH越高,钝化稳定性越强;土壤pH越低,钝化稳定性越差;土壤pH的变化对钝化稳定性影响很大。 将两种钝化剂实际应用于铜污染土壤修复中,结果发现,施入改性纳米黑碳后,三种土壤中有效态含量均在40天后无显著变化,说明改性纳米黑碳的钝化稳定性强。改性纳米黑碳施入三种土壤中后,褐土中有效态的减少最为迅速,10-20内有效态含量减少最多,30天内基本完成有效态的减少。棕壤中30-40天有效态含量减少最多,40天内基本完成有效态的减少。酸性棕壤中10-30天内有效态含量增加,有效态含量的减少主要发生在30-40天时。施入钠基膨润土后,棕壤和褐土中重金属有效态含量均在40天后无显著变化,说明钝化稳定性好。在酸性棕壤中,重金属有效态含量变化无规律,说明钝化稳定性差。钠基膨润土施入三种土壤中后,褐土中有效态的减少最为迅速,10-20内有效态含量减少最多,30天内基本完成有效态的减少。棕壤中10-20天有效态含量减少最多,40天内基本完成有效态的减少。 黑麦草的生长对钝化稳定性具有促进作用,,在施入改性纳米黑碳和钠基膨润土的土壤中,种植黑麦草的土壤中重金属有效态含量均低于未种植黑麦草的土壤。原因可能是,植物在生长过程中根部对重金属的吸附、从根部向地上部的转移等降低了土壤中有效态重金属含量。
[Abstract]:With increasing heavy metal pollution, hot repair of soil heavy metal pollution has become the environmental problem. In situ remediation technology is a kind of passivating agent is added to the soil, the adsorption of heavy metal passivator, precipitation, complexation, ion exchange and a series of redox reaction, in order to reduce the heavy metal migration technology and the biological effectiveness. Because of the technology of low cost, high repair efficiency, simple operation and has a good application prospect for the repair of low concentration of polluted soil. However, the fatal weakness is the passivation of heavy metals in the stable still remained in the soil, only to reduce the heavy metal in the soil can be transferred and the biological effectiveness, change with time or environmental conditions, heavy metals have again activated the threat.
This paper from the stability of passivating agent itself stability and passivation agent and heavy metal combining two aspects to study the stability of in situ remediation. Two kinds of modified nano carbon black passivating agent selected to exchange adsorption mechanism of main clay minerals - sodium bentonite and chelating adsorption mechanism mainly, cultivation of thermal stability experiments of passivating agent itself through the simulation experiment and chemical stability (chemical oxidation stability and pH stability), biological stability; through the factors of the stability of adsorption and desorption experiment study on passivation agent and heavy metal binding and influence; through the pot experiment of passivating agent stability in practical application. Its purpose is for the passivation agent applied to the in situ remediation of heavy metal contaminated soils with passivation on the basis of the theory.
The main results obtained in this paper are as follows:
For the selection of passivation materials research itself the stability of modified nano black carbon results showed that: (1) the thermal stability of the modified nano carbon black is very good, using thermogravimetric analyzer using modified nano carbon black gradually heating from room temperature to 700 degrees Celsius, the quality of the modified nano carbon black only decreased 13.01%. (2) chemical stability the modified nano carbon black. The oxidation of 24 hours of modified nano black carbon by 333mmo L-1 KMnO4, the maximum degradation rate of only 4.22%. modified nano carbon black acid has strong stability, acid alkali corrosion of modified nano carbon black solution with different pH, pH 2 and the degradation rate was 1.933%, pH was 12, the degradation rate of 5.334%. (3) modified nano carbon black at a concentration of less than Bacillus subtilis 1 * 105CFU mL-1 of the biological stability. When the concentration is above 1 * 105CFU - mL-1, with higher concentration of biological stability of Bacillus subtilis The maximum degradation rate of modified nano black carbon is 11%. when the concentration is 1 * 107cfu / mL-1 for 30 days. The biodegradation of modified nano black carbon is greater than that of chemical oxidation.
Two kinds of modified nano carbon black passivating agent selected to exchange adsorption mechanism mainly clay minerals - sodium bentonite and chelating adsorption mechanism based, Cu and Cd two kinds of heavy metals, the adsorption kinetics, adsorption isotherm experiments of two kinds of materials of two kinds of heavy metal adsorption properties. The results showed that the adsorption the Cu2+ and Cd2+ can be used to fit the quasi two kinetics and Langmuir equation well modified nano carbon black and sodium bentonite. The adsorption of heavy metals in the passivating agent is divided into different two stages. Using Langmuir equation to calculate the maximum adsorption capacity of Cu2+ and Cd2+ modified nano black carbon 23809mg kg-1 and 24390mg kg-1 respectively, the maximum adsorption of Cu2+ and Cd2+ of sodium bentonite were 4681mg - kg-1 and 5356mg - kg-1.Freundlich fitted n values are greater than 1, showed that two kinds of heavy metals in the two adsorbents were changed to preferential adsorption. The adsorption capacity of nano black carbon to two kinds of heavy metals is greater than that of sodium bentonite. The adsorption capacity of Cu2+ on two kinds of passivating agents is greater than that of Cd2+.
For desorption, two kinds of materials on the adsorption of heavy metals in different environmental conditions by 0.01mol and L-1CaCl2 results show that the temperature and salt concentration has little effect on the desorption rate, that stability is not affected by the passivation temperature and salt ion concentration; pH has a great effect on the desorption rate, with the decrease of pH desorption rate increases rapidly. PH, indicating that the soil is higher, more stable passivation; the lower the soil pH, passivation stability is worse; the pH variation of soil has great influence on the stability of the passivation.
The two passivation agent applied in copper contaminated soil remediation, results show that the application of modified nano carbon black, three kinds of available content in soil after 40 days were no significant change, indicating the passivation stability of modified nano - black carbon. The modified nano black carbon into three kinds of soils, available in cinnamon soil decreased most rapidly, the effective content of 10-20 reduced by up to 30 days to complete the basic state. The most effective to reduce the effective content of soil decreased by 30-40 days, 40 days to complete the basic state. Effectively reduce the increase in acid brown soil within 10-30 days of the effective content, reduce the content of available mainly occurred in 30-40 days. Application of sodium bentonite, available heavy metal content in brown soil and cinnamon soil in 40 days no significant change, indicating good stability in acid brown soil. The passivation, change of available heavy metal content without the law, that passive stability When sodium base bentonite was applied to three soils, the effective state of cinnamon soil decreased most rapidly, the effective content of 10-20 decreased most, and the effective state decreased basically within 30 days. The content of 10-20 days effective state in brown soil decreased the most, and the effective state was basically reduced within 40 days.
The growth of ryegrass can promote stability in application of passivation, modified nano carbon black and sodium bentonite in soil available heavy metal content in soil ryegrass were lower than those of non ryegrass planting soil. The reason may be that in the growth process of plant roots on adsorption of heavy metals, from the root to the ground the upper part of the transfer to reduce the content of available heavy metal in soil.

【学位授予单位】:山东师范大学
【学位级别】:硕士
【学位授予年份】:2015
【分类号】:X53

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