人工纳米粒子在矿物及土壤中转化和吸附行为的研究

发布时间：2018-01-07 06:38

本文关键词：人工纳米粒子在矿物及土壤中转化和吸附行为的研究　出处：《安徽农业大学》2015年硕士论文　论文类型：学位论文

【摘要】：纳米材料的广泛使用导致其不可避免地进入环境并对环境生物造成危害,其在环境中的物理化学过程会改变自身理化性质,对其毒性和归趋造成影响。本文以纳米ZnO和纳米Ag作为研究对象,分别考察了纳米ZnO在不同介质中的溶解和转化以及纳米Ag在土壤中的吸附行为。主要研究内容和结果如下：1.纳米ZnO溶解性及其转化行为研究。微米和纳米粒径ZnO在不含矿物的水溶液中溶解结果显示ZnO的溶解量随时间的增加而增加,pH5.5条件下ZnO溶解量大于其在pH 7.5条件下溶解量：与微米ZnO相比,纳米ZnO因粒径小、比表面积高而更容易发生溶解；EDTA的加入能够显著促进ZnO的溶解。纳米ZnO在含矿物溶液中溶解结果显示溶液中Zn~(2+)含量顺序为叶蜡石针铁矿γ-Al_2O_3.随着时间的增加含矿物溶液中Zn~(2+)含量逐渐降低,EDTA的加入显著增加了溶液中Zn的含量。pH 7.5条件下纳米ZnO在水溶液中溶解360天(d)后,采集纳米ZnO悬液中的固体样品进行XRD分析,发现其主要组分为ZnO和水锌矿,表明pH7.5条件下ZnO在水溶液中溶解并在一定条件下转化生成水锌矿。利用X射线衍射(X-Ray Diffraction, XRD)、X射线吸收精细结构(X-Ray Absorption Fine Structure, EXAFS)和透射电子显微镜(Transmission Electron Microscope, TEM)分析纳米ZnO在含矿物溶液中转化及次生矿生成。XRD结果显示仅含γ-Al_2O_3的固体样品中矿物相发生变化,含针铁矿和叶蜡石的固体样品矿物相无明显变化。进一步通过EXAFS和TEM分析含γ-Al_2O_3样品,发现pH 7.5条件下向含γ-Al_2O_3溶液中加入纳米ZnO 24小时后,有Zn-Al层状双氢氧化物(Zn-Al Layered Double Hydroxide,Zn-Al LDH)生成。pH 5.5条件下样品EXAFS结果显示纳米ZnO加入到含γ-Al_2O_3容液中150 d后有Zn-Al LDH沉淀生成,该条件下360 d样品TEM电镜图可见条状与片状沉淀物。pH 7.5条件下将纳米ZnO加入到含有EDTA和γ-Al_2O_3的溶液中,反应150 d后样品EXAFS图谱未见Zn-Al LDH特征峰,该条件下360 d样品TEM和能谱分析发现存在Zn-Al LDH沉淀,表明EDTA的存在会抑制pH7.5条件下Zn-Al LDH的生成。此外,我们还进一步研究了纳米ZnO在实际土壤—红壤和乌栅土中的溶解转化,并用EXAFS进行分子机制的研究,结果显示纳米ZnO加入到中性土壤乌栅土中30 d后有Zn-Al LDH生成,而加入到酸性土壤红壤中150 d后仍无Zn-Al LDH生成。2.络合剂EDTA对Zn-Al LDH生成的影响。研究不同pH条件下EDTA对γ-Al_2O_3吸附Zn~(2+)的影响,结果显示pH 5.5条件下γ-Al_2O_3对Zn~(2+)的吸附量低于pH 7.5条件下；EDTA的加入增强了pH 5.5条件下γ-Al_2O_3对Zn~(2+)的吸附作用,该条件下Zn~(2+)在γ-Al_2O_3的吸附量随EDTA浓度的增加出现先增加后降低的趋势,并在0.5 mmol/L EDTA浓度时达到最大吸附量。pH 7.5条件下γ-Al_2O_3对Zn~(2+)有着强烈的吸附作用,EDTA的加入减弱了γ-Al_2O_3对Zn~(2+)的吸附作用,Zn~(2+)在γ-Al_2O_3上的吸附量随EDTA加入量的增加而降低。对吸附Zn~(2+)的γ-Al_2O_3进行EXAFS分析,结果显示仅pH 7.5条件下样品有Zn-Al LDH特征峰出现,含有EDTA的样品以及pH 5.5条件下的样品中均未出现Zn-Al LDH特征峰,说明pH 7.5条件下γ-Al_2O_3吸附Zn~(2+)后会生成Zn-Al LDH沉淀,EDTA的存在会阻碍Zn-Al LDH沉淀的生成。3.纳米Ag在土壤上吸附行为的研究。选取四种不同理化性质的土壤,考察土壤pH、有机质和二价阳离子Ca~(2+)对纳米Ag在土壤上吸附的影响。试验结果表明纳米Ag在酸性土壤的吸附量高于中性土壤,当土壤酸碱性相似时土壤有机质含量越高纳米Ag在其表面的吸附量越高。纳米Ag在四种土壤上的吸附等温线都能较好地利用Freundlich方程进行拟合。Ca~(2+)的存在均增加了纳米Ag在四种土壤上的吸附量,当Ca~(2+)浓度在0.1-10 mM范围内,纳米Ag在中性土壤上的吸附量随Ca~(2+)浓度的增加而增加,而在酸性土壤上的吸附量则随着Ca~(2+)浓度的增加,出现先增加后减小的趋势。这一结果有助于了解纳米Ag在不同性质土壤上的吸附行为,为评价纳米Ag在环境中的毒性和生态风险提供了有用信息。
[Abstract]:The widespread use of nano materials which inevitably enter the environment and harm to the environment in the environment of biological, physical and chemical processes will change their physicochemical properties on the toxicity and fate of the impact. In this paper, nano ZnO and nano Ag as the research object, were investigated the adsorption behavior of nano ZnO in different media the dissolution and transformation and nano Ag in the soil. The main research contents and results are as follows: 1. nm ZnO solubility and transformation behaviors of micron and nanometer size. The results show that ZnO ZnO dissolved dissolved amount increased with time in aqueous solution containing minerals, the dissolved amount of ZnO under the condition of pH5.5 under the condition of pH 7.5 is greater than the dissolved amount compared with the micro ZnO, nano ZnO with small particle size, high specific surface area and more prone to dissolution; the addition of EDTA could significantly promote the dissolution of ZnO. Nano ZnO in ore The solution results showed that dissolution of Zn~ particles in the solution (2+) content in the order of pyrophyllite goethite gamma -Al_2O_3. with the increase of time containing mineral solution Zn~ (2+) content decreased gradually, the addition of EDTA significantly increased the content of.PH in the solution of Zn ZnO 7.5 nanoparticles in aqueous solution under the condition of dissolution (d) after 360 days nano ZnO suspension solid samples, collected in the solution of XRD analysis, we found that the main component is ZnO and water zinc ore, showed that the pH7.5 under the condition of ZnO in aqueous solution and dissolved into water zinc under certain conditions. By using X ray diffraction (X-Ray Diffraction, XRD), X (X-ray absorption fine structure X-Ray Absorption Fine Structure, EXAFS) and transmission electron microscopy (Transmission Electron, Microscope, TEM) analysis of nano ZnO transformation and secondary ore generation.XRD results showed that the change of mineral phase solid sample containing only gamma -Al_2O_3 in mineral solution, Containing goethite and pyrophyllite mineral phases of solid samples without significant change. Further EXAFS and TEM analysis of samples containing gamma -Al_2O_3, found under the condition of pH 7.5 to -Al_2O_3 solution containing gamma added nano ZnO 24 hours later, a Zn-Al layered double hydroxides (Zn-Al Layered Double Hydroxide, Zn-Al LDH) EXAFS.PH 5.5 generation sample results under the display of nano ZnO added to the solution containing gamma -Al_2O_3 in 150 d after Zn-Al LDH precipitate, the condition of 360 D samples of TEM electron microscope visible strip with pellet under the condition of.PH 7.5 nano ZnO was added to the solution containing EDTA and gamma -Al_2O_3, after 150 D sample EXAFS Zn-Al no LDH feature map under the condition of 360 D peak, the samples of TEM and energy spectrum analysis shows that there are Zn-Al LDH precipitation, indicated the presence of EDTA will generate Zn-Al LDH inhibition of pH7.5 conditions. In addition, we also studied in nano ZnO The actual soil red soil and Wushan soil dissolved in transformation, and study the molecular mechanism of EXAFS, the result shows that nano ZnO added to the neutral soil wushantu soil after 30 d Zn-Al LDH, is added to the effects of acidic red soil in 150 D Zn-Al LDH.2. is still no generation of complexing agent EDTA on Zn-Al the development of LDH. EDTA on the adsorption of Zn~ on gamma -Al_2O_3 under different pH conditions (2+) effects, results showed that under the condition of pH 5.5 -Al_2O_3 of Zn~ gamma (2+) adsorption capacity is lower than under the condition of pH 7.5; EDTA was improved by adding pH 5.5 under the condition of Zn~ gamma -Al_2O_3 (2+) adsorption, the under the condition of Zn~ (2+) increased with the concentration of EDTA has increased first and then decreased in the adsorption of gamma -Al_2O_3, and the maximum adsorption capacity of.PH 7.5 under the condition of Zn~ gamma -Al_2O_3 in 0.5 mmol/L concentration of EDTA (2+) has a strong adsorption, the addition of EDTA decreased the -Al_2O_3 of Zn~ gamma (2+) the adsorption of Zn~ (2+) adsorption capacity increases in -Al_2O_3 with gamma EDTA content decreased. On adsorption of Zn~ (2+) gamma -Al_2O_3 EXAFS analysis, the results showed that only 7.5 pH samples under the conditions of Zn-Al LDH characteristic peaks, samples containing EDTA and pH 5.5. The samples were not found in the Zn-Al LDH Zn~ -Al_2O_3 gamma characteristic peak, 7.5 under the conditions of adsorption of pH (2+) will generate Zn-Al LDH of precipitation, blocking the formation of.3. nano Ag Zn-Al LDH precipitation adsorption behavior in soil on the existence of EDTA. There were four different physical and chemical properties of soil, soil investigation pH, organic matter and two valence cation Ca~ (2+) on the effect of nano Ag adsorbed in the soil. The experimental results showed that nano Ag adsorption amount in acidic soils than in neutral soil, when the soil pH is similar to soil organic matter content was higher in nano Ag adsorption on the surface of nano Ag is higher. Can use Freundlich equation to fit.Ca~ in four kinds of soil adsorption isotherms (2+) are added nano Ag in the four kinds of soil on the adsorption capacity, when Ca~ (2+) 0.1-10 concentration in the range of mM, the adsorption amount of nano Ag in neutral soil with Ca~ (2+) concentration the increase of the adsorption on acidic soils with Ca~ (2+) concentration increased, appeared increased first and then decreased. This result is helpful to understand the adsorption behavior of nano Ag in different soils and provide useful information for the evaluation of toxicity of nano Ag in the environment and health state risk.

【学位授予单位】：安徽农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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