可渗透反应墙对模拟铅镉复合污染地下水的修复效能研究

发布时间：2017-12-26 19:09

本文关键词：可渗透反应墙对模拟铅镉复合污染地下水的修复效能研究　出处：《陕西科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：地下水作为地球上重要的自然资源,对于人类的生产生活有着密切的影响。由于工业废水、废渣不合理排放、农药化肥的大量使用,导致我国地下水污染越来越严重。目前,重金属污染地下水对环境的安全性越来越成为人们关注的焦点,因此,如何更好的修复重金属污染地下水已成为当前非常重要的问题。可渗透反应墙(Permeable Reactive Barrier,简称PRB)是地下水污染原位修复的一种有效技术,它的效率在很大程度上取决于反应填料的性质。本研究以粉碎秸秆、合成沸石、黄土源铁锰结核和粉煤灰为可渗透反应墙填料修复模拟重金属Pb/Cd污染地下水,采用响应曲面法对其影响因素进行优化分析;选取Pb/Cd进水浓度和流速两个影响因素进行单因素和混合正交试验,借助SPSS回归模型研究两因素对Pb/Cd修复效果的影响,并对相关数据进行拟合分析;采用PRB柱完成耐久性实验,探究该PRB柱运行的可行性与持续性,并对反应前后填料进行XRD、FTIR、SEM测试研究,考察并推断出四种反应填料对Pb/Cd修复的作用机理和效果。本研究的主要内容如下:(1)以秸秆、沸石、铁锰结核和粉煤灰为填料组建PRB实验装置,完成进水浓度、流速、温度、pH和填料性质等影响因素对Pb/Cd去除率的影响实验。实验内容涉及到:反应填料的选择,反应填料安全性测试分析,PRB实验装置的设计,影响因素实验等。填料性质研究结果显示,铁锰结核的比表面积为121.07m2/g,比表面积较大,而沸石的CEC为117mmol/100g,四种填料均可作为PRB填料进行实验。填料安全性测试表明,四种填料的浸出毒性测试值低于标准值,说明填料是安全可用的。影响因素实验表明,浓度、流速、pH和温度对Pb/Cd去除率均具有较大影响,而添加腐殖化秸秆后Pb/Cd去除率有显著提高。(2)选取响应曲面法进行PRB柱的影响因素优化实验,根据Design-Expert软件中的Box-Behnken设计进行响应曲面分析,完成条件优化。结果如下:Pb/Cd回归模型方差分析中,模型均显著(ρ0.0001),模型确定系数为RPb2=0.9957和RCd2=0.9839,说明此模型能解释99.57%和98.39%的响应值变化。PRB系统对Pb/Cd离子修复过程的最佳条件为:溶液浓度Pb为7.11mg/L、Cd为0.74mg/L,温度24~25℃、p H为弱酸性,在此条件下,Pb/Cd的去除率最高。(3)对流速和进水浓度进行单因素和混合正交实验,结果表明:该PRB系统可承受最大铅进水浓度为20mg/L(去除率达80%以上),而可承受最大Cd浓度为1mg/L(去除率达75%以上)。利用PRB系统修复模拟Pb/Cd污染地下水,对实验结果进行模拟分析,结果表明:Pb/Cd去除率与进水浓度和流速都有一定的相关性,且Pb/Cd去除率和进水浓度的相关性均比Pb/Cd去除率和流速的相关性高;二元线性回归模型能更好地展示Pb/Cd去除率随进水浓度和流速的变化趋势。(4)采用PRB柱设计耐久性实验并考察反应填料对Pb/Cd的修复效果和机理。结果显示:四种填料在反应过程中起到了不同的作用。根据光谱分析,秸秆表面有大量官能团,猜测与Pb/Cd发生配位络合反应;而铁锰结核的表面变粗糙,可能是反应沉淀所致;粉煤灰和粉煤灰基沸石由于其表面疏松且比表面积大,吸附效果显著。综上可知,四种填料利用物理和化学反应共同作用,实现了Pb/Cd复合污染地下水的深度修复。
[Abstract]:As an important natural resource on the earth, groundwater has a close influence on human production and life. Because of the irrational discharge of industrial waste water, waste residue and the use of pesticide and chemical fertilizer, the groundwater pollution in China is becoming more and more serious. At present, the safety of groundwater polluted by heavy metals is becoming the focus of attention. Therefore, how to better repair heavy metal contaminated groundwater has become a very important problem. Permeable Reactive Barrier (PRB) is an effective technology for in-situ remediation of groundwater pollution, and its efficiency largely depends on the nature of the reaction filler. In this study, crushed straw, synthetic zeolite, loess source iron manganese nodules and fly ash as the permeable reactive barrier packing repair heavy metal Pb/Cd pollution of groundwater simulation, the optimization analysis on the influence factors of response surface method; select Pb/Cd influent concentration and flow rate of the two factors were the single factor and the mixed orthogonal test, by using SPSS regression model of two factors on Pb/Cd repair effect, and the related data fitting analysis; PRB column with complete durability test, explore the feasibility of the PRB column operation and continuous, and the reaction before and after filling XRD, FTIR, SEM test research, study and deduce the mechanism of four kinds of fillers on the reaction Pb/Cd repair and effect. The main contents of this study are as follows: (1) straw, zeolite, iron manganese nodule and fly ash are used as filling materials to build PRB experimental device, and the effects of influent concentration, flow rate, temperature, pH and filler properties on Pb/Cd removal efficiency are completed. The experiment includes the selection of the reaction packing, the safety test and analysis of the reaction packing, the design of the PRB experimental device, the experiment of the influence factors, etc. The results of filler properties show that the specific surface area of Fe Mn nodules is 121.07m2/g, the specific surface area is large, while the CEC of zeolite is 117mmol/100g. Four kinds of fillers can be used as PRB filler. The test of packing safety shows that the test value of the leaching toxicity of the four kinds of fillers is lower than the standard value, indicating that the filler is safe and available. The influence factors experiments showed that concentration, flow rate, pH and temperature had great influence on Pb/Cd removal rate, and Pb/Cd removal rate increased significantly after adding humification straw. (2) select the response surface method to optimize the influence factors of PRB column. According to the Box-Behnken design of Design-Expert software, response surface analysis is completed, and the condition optimization is completed. The results are as follows: the model of analysis of variance Pb/Cd regression model were significantly (P 0.0001), the coefficient of determination of RPb2=0.9957 and RCd2=0.9839 model, this model can explain the response of 99.57% and 98.39% of the variation. The best conditions of PRB system for Pb/Cd ion repair process are as follows: the concentration of solution is Pb, 7.11mg/L is Cd, 0.74mg/L is Cd, the temperature is 24~25, and P H is weakly acidic. Under these conditions, the removal rate of Pb/Cd is the highest. (3) single factor and mixed orthogonal experiments on flow velocity and influent concentration showed that the PRB system could bear the maximum lead and influent concentration of 20mg/L (removal rate of more than 80%), while the maximum Cd concentration was 1mg/L (removal rate of 75%). Repair of simulated Pb/Cd polluted groundwater by PRB system, simulation analysis of the experimental results, the results showed that the Pb/Cd removal rate and influent concentration and flow rate have a certain correlation, and the correlation between Pb/Cd removal rate and the influent concentration was higher than Pb/Cd removal rate and high velocity; two element linear regression model can better show the Pb/Cd removal the rate of change with the inlet concentration and flow velocity. (4) the durability test of PRB column was designed and the effect and mechanism of reacting filler on the repair of Pb/Cd were investigated. The results showed that the four kinds of fillers played a different role in the reaction process. According to spectroscopic analysis, there are a lot of functional groups on the surface of the straw, which conjecture the complexation reaction with Pb/Cd. However, the surface of the Fe Mn nodules is rough, which may be caused by reaction precipitation. The adsorption of fly ash and fly ash based zeolite is obvious because of its loose surface and large specific surface area. In a comprehensive way, the four kinds of fillers used both physical and chemical reactions to achieve the deep remediation of Pb/Cd contaminated groundwater.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X523

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