复合有机物对重金属Cd污染土壤淋洗效果的研究

发布时间：2018-03-11 06:06

本文选题：重金属　切入点：单宁酸　出处：《广西大学》2016年硕士论文　论文类型：学位论文

【摘要】：本文选取盐酸、EDTA、柠檬酸、单宁酸、鼠李糖脂五种淋洗剂,对单一淋洗剂浓度、淋洗速率、淋洗时间三种单因素影响进行研究；通过筛选出修复效果较好、环境危害较小的淋洗剂进行复合,寻找最优复合淋洗条件,并用动力学方程对淋洗过程进行拟合,探索淋洗条件下的动力学特征。通过对土壤不同深度重金属浓度及赋存形态的变化,探究重金属的淋洗机理,最后采用地累积指数(Mull指数)法对重金属镉污染土壤在最优淋洗条件下淋洗后的修复效果进行评价。实验结果表明：(1)五种淋洗剂的土壤重金属镉的淋洗效果顺序为：HClEDTA柠檬酸单宁酸鼠李糖脂。当HCl浓度为2.0 mol·L-1,EDTA浓度为0.1 mol·L-1,柠檬酸浓度为0.8mol·L-1,单宁酸浓度为10.0mmol·L-1,鼠李糖脂浓度为1.5%时,在淋洗速率为1.0mL·min-1,时间为24h条件下,土壤重金属Cd的去除率分别达到88.89%、83.95%、71.22%、70.22%、23.00%。(2)通过多种淋洗剂的两两复配,最终发现,当柠檬酸与单宁酸这两种淋洗剂进行复配且复配体积比为3：1,采用同时投加的方式连续淋洗24h,土壤重金属镉的去除率为96.66%。通过对淋洗时间的动力学研究发现随着淋洗时间的增加,复合淋洗条件下对镉的去除速率逐渐下降。(3)通过动力学方程拟合,三种方程的拟合度大小为：Elovich模型拟合度最优,相关系数R2为0.994 0,双常数模型的拟合度次之,相关系数R2为0.9786,一级动力学方程模型拟合度最差。说明复合淋洗土壤重金属镉的淋洗过程主要是扩散因子控制,解吸过程为非均相扩散。(4)在最优淋洗条件下,复合淋洗剂在淋洗前后对土壤重金属镉赋存形态的含量测定,淋洗后重金属镉的酸可提取态和氧化物结合态去除率分别达到98.45%、 90.98%,且随土壤深度的增加,重金属浓度呈上升的趋势。地累积指数法评价结果显示,淋洗前后土壤由6级极严重污染变为1级轻度-中等污染,土壤重金属镉的浓度显著下降,土壤修复效果显著。
[Abstract]:This paper selects EDTA, hydrochloric acid, citric acid, tannic acid, rhamnolipid five eluant, the single eluant concentration, leaching rate, leaching time of three kinds of single factors; through the selected good repairing effect, less harm to the environment of the eluent were combined to find the optimal elution conditions of composite, and leaching process the fitting with the kinetic equation, explore the kinetics of leaching conditions. Through the change of different depth of heavy metal concentration and speciation of soil heavy metal leaching, probe into the mechanism, the geoaccumulation index (Mull index) method to evaluate the repairing effect of cadmium polluted soil in the optimal leaching conditions after leaching. Experimental results show that: (1) the order of elution effect of five kinds of leaching agent of cadmium in soil: HClEDTA citric acid tannic acid rhamnolipid. When HCl concentration was 2 mol, L-1, EDTA concentration 0.1 mol - L-1, 0.8mol - L-1 concentration of citric acid, tannic acid concentration was 10.0mmol - L-1, Shu Li glucose concentration is 1.5%, the leaching rate of 1.0mL, min-1, time is 24h under the condition of soil heavy metal Cd removal rate reached 88.89%, respectively, 83.95%, 71.22%, 70.22%, 23.00%. (2) by 22 compound a variety of eluent, eventually found that when citric acid and tannic acid of the two kinds of leaching agent compound and mixed volume ratio is 3:1, by adding the continuous leaching of cadmium in soil 24h, the removal rate of 96.66%. on the leaching time dynamic study found that with the increase of leaching time, leaching conditions of composite the removal rate of cadmium decreased gradually. (3) through the dynamic equation fitting, fitting size three equations: Elovich optimal model fitting degree, correlation coefficient R2 is 0.9940 and the double constant model fitting degree of correlation coefficient R2 0.9786, a kinetic equation model fitting degree is the worst. Leaching process of composite leaching of soil cadmium is the main factor for diffusion control, the desorption process of heterogeneous diffusion. (4) under the optimal leaching conditions, determination of compound leaching agent in the leaching of cadmium in soil before and after the deposit form content, after washing the heavy metal cadmium acid reduciblefraction and removal rate reached 98.45% and 90.98% respectively, and with the increase of soil depth, the concentration of heavy metals was increased. The cumulative index evaluation results showed that soil after leaching by the 6 stage of serious pollution becomes 1 mild - moderate pollution, the concentration of cadmium in soil significantly, soil remediation effect is remarkable.

【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X53

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