生物炭对黄土中镉的吸附—固定化作用及植物有效性影响及其机制

发布时间：2018-06-07 06:25

本文选题：生物炭 + 重金属　；参考：《兰州交通大学》2017年博士论文

【摘要】：随着城市化和工业化的快速发展,土壤重金属污染的不断加剧已经成为不容忽视的环境问题。生物炭(Biochar)是生物质在限氧条件下热解制备的富碳颗粒。生物炭由于其具有丰富的表面官能团和发达的孔隙结构等特征使其对重金属具有较强的吸附固定化性能,生物炭作为固定化材料修复重金属污染土壤已成为环境和土壤领域的研究热点之一。论文简要介绍了土壤重金属污染及其修复技术研究进展,重点评述了生物炭吸附重金属的特性及机制和生物炭在重金属污染土壤固定化修复中的应用研究进展。针对生物炭施加到黄土后对重金属的吸附固定性能与生物炭结构之间的构效关系尚不明确,生物炭施加对黄土中重金属镉(Cd)的植物有效性与植物吸收Cd含量的相关关系不清等问题,本文选择玉米秸秆生物质为代表制备生物炭,通过SEM-EDS、FTIR、XRD、XPS、比表面积测定和元素分析等手段表征了生物炭的表面性质和结构特征;研究了生物炭对Cd的吸附特性和机制,探讨了生物炭对共存重金属的竞争吸附机制;进一步采用表面改性方法制备了氨基修饰玉米秸秆生物炭,探明了氨基修饰生物炭对Cd的吸附机制;在此基础上,揭示了生物炭施入黄土后对Cd的吸附固定性能与生物炭结构之间的构效关系;最后探究了生物炭施入Cd污染黄土后对Cd赋存形态分布和Cd植物有效性的影响机制。研究结果为区域土壤重金属污染控制提供科学依据。论文的主要结果及创新性如下:(1)揭示了玉米秸秆生物炭与Cd的相互作用机制,发现生物炭表面的含氧官能团对Cd的络合作用是其吸附Cd的主要机制。生物炭吸附Cd前后的XRD图谱未发现新的衍射峰,表明生物炭吸附Cd后没有沉淀物质产生,即表面沉淀作用不是生物炭吸附Cd的主要机制。同时,生物炭吸附Cd前后的FTIR谱图上的羟基(—OH)和羰基(C=O)特征峰波数发生偏移、峰强降低,表明—OH和C=O对Cd产生了表面络合作用。研究生物炭吸附Cd前后的XPS特征,结果发现,生物炭吸附Cd的过程中其表面含氧官能团对应的结合能分别向高能量偏移0.2 eV,表明生物炭表面含氧官能团与Cd形成Cd—R键(R表示为—COO、—CO等)。此外,溶液平衡pH值在生物炭吸附Cd后由5.4降低至5.1,进一步证实了生物炭表面官能团与Cd形成配合物。Cd、Cu和Zn在生物炭上的竞争吸附行为表明,生物炭对Cd、Cu和Zn的吸附性能与重金属自身的物理化学性质有关。氨基修饰生物炭对Cd的吸附机制主要为生物炭表面的氨基官能团和含氧官能团与Cd的络合作用,且生物炭氨基官能团对Cd的结合能力强于含氧官能团对Cd的结合能力。(2)率先研究了生物炭对黄土中Cd吸附固定作用的构效关系。发现生物炭自身的理化性质对施加生物炭黄土吸附Cd有显著影响,生物炭的极性是影响施加生物炭黄土吸附Cd最关键的因素。添加不同比例生物炭的黄土对Cd的吸附结果表明,添加生物炭黄土对Cd的吸附性能高于黄土对Cd的吸附性能,且随着生物炭添加比例的增大,生物炭添加黄土对Cd的吸附性能显著增强。添加不同原料制备生物炭的黄土对Cd的吸附性能也存在较大差异,向黄土中添加秸秆生物炭对Cd的吸附性能优于粪质生物炭和玉米芯生物炭。同时研究发现,不同温度制备的生物炭的理化性质有较大差异,而生物炭的极性指标(O+N)/C和添加生物炭黄土吸附Cd的模型参数KF呈现良好的正相关关系,而生物炭比表面积与添加生物炭黄土吸附Cd的性能之间没有显著的相关关系。(3)研究了玉米秸秆生物炭施入Cd污染黄土后对黄土中Cd的赋存形态的影响以及黄土中Cd赋存形态和玉米体内Cd含量的关系。发现向Cd污染黄土施加生物炭可显著降低黄土中有效态Cd的含量,其作用机制包括生物炭的石灰效应改变黄土中Cd的赋存形态、生物炭吸附固定作用降低Cd的有效浓度。生物炭对Cd污染黄土性质及Cd赋存形态分布的影响研究结果表明,生物炭施加可显著升高土壤pH值、土壤阳离子交换量(CEC)和土壤有机质(SOM)含量,同时可提高黄土中脲酶和碱性磷酸酶的活性。向Cd污染黄土施加生物炭促使Cd由不稳定的有效态转化为稳定的残渣态。同时,玉米根部与地上部Cd含量与黄土中有效态Cd含量呈极显著正相关(P0.01),与残渣态Cd含量呈极显著负相关(P0.01),生物炭施入Cd污染黄土显著降低了玉米根部和地上部的Cd含量(P0.05)。
[Abstract]:With the rapid development of urbanization and industrialization, the increasing pollution of heavy metals in soil has become an environmental problem that can not be ignored. Biological carbon (Biochar) is a carbon rich particle prepared by the pyrolysis of biomass under the condition of oxygen limiting. Biological carbon has the characteristics of heavy metal with its rich surface functional groups and the pore structure of hair. It has become one of the hot topics in the field of environment and soil to repair heavy metal contaminated soil as a immobilized material. The paper briefly introduces the research progress of soil heavy metal pollution and its remediation technology. It focuses on the characteristics and mechanism of bio carbon adsorbed heavy metals and the heavy metals in biological carbon. The research progress in the application of immobilized remediation of contaminated soil. The relationship between the adsorption fixed performance of heavy metals and the structure of biological carbon after the application of the biological carbon to the loess is not clear. The relationship between the plant availability of heavy metal cadmium (Cd) in the Loess and the absorption of Cd in the plant is not clear. Maize straw biomass was used as the representative to prepare biological carbon. The surface properties and structural characteristics of biological carbon were characterized by means of SEM-EDS, FTIR, XRD, XPS, specific surface area measurement and element analysis. The adsorption characteristics and mechanism of biological carbon to Cd were studied, and the competitive adsorption mechanism of biological carbon to coexisting heavy metals was discussed, and surface modification was further used. Methods the amino modified maize straw bio carbon was prepared, and the adsorption mechanism of amino modified biological carbon to Cd was explored. On this basis, the relationship between the adsorption fixed properties of Cd and the structure of biological carbon was revealed after the biological charcoal was applied into the loess. Finally, the distribution of Cd and the Cd plants were explored after the biological charcoal was applied to the Cd polluted loess. The main results and innovations of this paper are as follows: (1) the interaction mechanism of maize straw bio carbon and Cd was revealed, and the cooperative use of oxygen containing functional groups to Cd on the surface of biochar was the main mechanism for its adsorption of Cd. Before Cd was adsorbed by biological carbon No new diffraction peak was found in the XRD map, indicating that no precipitate was produced after adsorption of Cd by biological carbon. That is, the surface precipitation is not the main mechanism for the adsorption of Cd by biological charcoal. At the same time, the number of hydroxyl (- OH) and carbonyl (C=O) peaks on the FTIR spectrum before and after the adsorption of Cd is offset and the peak intensity decreases, indicating that OH and C=O have produced Cd. The surface complexing effect. Study the XPS characteristics before and after adsorption of Cd by biological carbon. It is found that the corresponding binding energy of oxygen functional groups on the surface of biological carbon migration to high energy is 0.2 eV respectively, indicating that oxygen functional groups on the surface of carbon dioxide and Cd form Cd R bonds (R represents COO, CO, etc.). Besides, the pH value of the solution balance is absorbed in biological carbon. The adsorption of Cd,.Cd, Cu and Zn on biological carbon showed that the adsorption properties of Biocharcoal on Cd, Cu and Zn were related to the physical and chemical properties of heavy metals. The adsorption mechanism of amino modified carbon to Cd was mainly the ammonia on the surface of Cd. The combination of basic functional group and oxygen containing functional group with Cd, and the binding ability of biological carbon amino functional groups to Cd is stronger than that of oxygen containing functional groups on Cd. (2) the structure effect relationship of the adsorption and fixation of Cd in loess was first studied. It was found that the physical and chemical properties of biological charcoal have significant influence on the application of Cd to the adsorption of Cd on the biological carbon loess. The polarity of biological charcoal is the most important factor affecting the adsorption of Cd on the adsorption of Biocharcoal loess. The adsorption of Cd by adding different proportions of biological carbon to the Loess shows that the adsorption performance of Cd is higher than that of the loess to Cd, and with the increase of the proportion of biological charcoal, the adsorption property of biological charcoal to Cd is remarkable. The adsorption performance of Cd by adding different raw materials for biological carbon was also greatly different. The adsorption performance of Cd by adding straw bio carbon to Huang Tuzhong was better than that of fecal carbon and corn cob. Meanwhile, the physical and chemical properties of biological charcoal prepared at different temperatures were different, and the polarity index of biological carbon (O+N) was also found. /C and the model parameter KF of adding biological carbon loess to Cd showed good positive correlation, but there was no significant correlation between the specific surface area of biological carbon and the performance of adding bio carbon loess to the adsorption of Cd. (3) the effects of maize straw bio carbon into the Cd contaminated loess and the occurrence of Cd in the Loess and the occurrence of Cd in loess were studied. The relationship between morphology and the content of Cd in maize was found. It was found that applying biological carbon to Cd contaminated loess could significantly reduce the content of effective Cd in loess. The mechanism of its action included the lime effect of biological charcoal to change the form of Cd in loess, and the adsorption and fixation of Biocharcoal to reduce the effective concentration of Cd. The properties of Cd contaminated loess and the existence of Cd form by biological carbon. The results of the influence of the state distribution showed that the soil pH value increased significantly, the soil cation exchange (CEC) and the soil organic matter (SOM) content, and the activity of urease and alkaline phosphatase in the loess. The application of bio carbon to the Cd polluted loess promoted the transformation of Cd from the unstable effective state to the stable residue state. There was a significant positive correlation between the Cd content of rice root and the upper part of the ground and the content of effective Cd in the loess (P0.01), which had a significant negative correlation with the residue Cd content (P0.01). The content of Cd in the root and upper part of the maize (P0.05) was significantly reduced by the application of the biological carbon into the Cd polluted loess.
【学位授予单位】：兰州交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X53

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