不同载气条件及改性对生物炭物化性质及吸附硝氮性能影响研究

发布时间：2017-12-28 07:06

本文关键词：不同载气条件及改性对生物炭物化性质及吸附硝氮性能影响研究　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：由于农业生产中化肥农药的过量施用和较低的利用率,以及工业和生活废水的排放,硝氮已经成为水体富营养化和非点源污染的重要污染物。有研究表明,硝氮浓度的增加对人体健康构成潜在威胁,过量硝氮还会造成动植物急性中毒、病虫害等影响。传统去除水体中硝氮的方法主要分为生物法和物理—化学法。生物法经济有效且环保,但过程缓慢,处理时间长;物理—化学方法包括反渗透、电渗析、离子交换、吸附等,其中吸附法受到广泛关注,而当前的研究热点之一是寻找一种高效、经济且环保的吸附剂。生物炭,也称生物质炭,是指生物质原材料(如秸秆、粪便、花生壳等)在限氧环境下,经一定的温度(一般低于700℃)热解产生的多孔富碳固体。因生物炭具有含碳量高、比表面积较大、表面负电荷较多以及电荷密度较高、稳定性强等特性,近年来被广泛应用于去除及治理各领域污染物。然而,生物炭的性质主要取决于原料来源和制备条件,如温度和载气条件,载气条件主要以氮气、氦气等惰性气体为主,探索CO2作为载气用于制备生物炭方面的相应研究则明显偏少。同时,生物炭施加到水体环境中具有固液分离难的缺点,有造成二次污染的风险。磁性生物炭作为一种节能环保且易回收利用的吸附材料,用来处理含硝氮废水具有一定的研究意义。因此,为更好的理解CO2等载气条件改变与热解温度对生物炭的影响,本文考察了N2和CO2两种载气及不同热解温度下制备的花生壳生物炭,在物化性质上的差异,及其对水体中硝氮的吸附性能的影响。同时,将制备好的以N2为载气的生物炭清洗后利用Fe3+/Fe2+溶液混合改性,将生物炭磁化,对制备的磁性生物炭复合材料进行表征分析(电镜扫描、红外光谱、X射线、元素分析、比表面积等),并探讨了磁性生物炭吸附水体中硝氮的吸附性能。研究结果表明:随温度升高,生物质炭化更充分,比表面积更大;CO2载气条件下生物炭的零电荷点提升速率(9～20%)约为N2气氛的2倍(6～10%);700℃时,CO2载气条件下生物质被气化造成C损失,且O元素被明显引入生物炭中形成新的C-O键;改性之后生物炭的零电荷点、比表面积明显增大;吸附动力学及热力学表明,生物炭对硝氮吸附能力均较弱,内扩散,静电吸附等共同作用于吸附过程,且N2载气条件制备的生物炭的硝氮吸附性能优于CO2载气条件20%以上;此种方法改性之后生物炭对硝氮吸附能力大大减弱。
[Abstract]:Because of the over application and low utilization rate of chemical fertilizers and the discharge of industrial and domestic wastewater, nitrate has become an important pollutant of eutrophication and non-point source pollution. Some studies have shown that the increase of nitrate concentration poses a potential threat to human health. Excessive nitrate can also cause acute intoxication, disease and insect pests of animals and plants. The traditional methods of removing nitrate in water are mainly divided into biological and physical - chemical methods. Biological method is economical and effective environmental protection, but the process is slow, long processing time; physical and chemical methods including reverse osmosis and electrodialysis, ion exchange, adsorption, the adsorption method has attracted wide attention, and the focus of current research is to find an efficient, economic and environmentally friendly adsorbent. Biochar, also known as biochar, refers to porous carbon rich solids produced by pyrolysis of biomass raw materials (such as straw, feces, peanut shells, etc.) under certain oxygen temperatures (usually below 700 degrees). Biochar is widely used to remove and control pollutants in various fields because of its high carbon content, large specific surface area, high surface negative charge, high charge density and strong stability. However, the properties of biochar are mainly determined by the source and preparation conditions of raw materials, such as temperature and carrier gas conditions. The carrier gas conditions are mainly inert gases such as nitrogen and helium. The study of CO2 as carrier gas for preparing biochar is less. At the same time, the application of biological carbon to the water environment has the disadvantage of solid and liquid separation, and there is a risk of two pollution. As a kind of energy saving and recyclable adsorption material, magnetic biological carbon has a certain research significance for the treatment of nitrogenous nitrogen wastewater. Therefore, for a better understanding of CO2 carrier gas conditions change and pyrolysis temperature on the effects of biochar, this paper investigates the N2 and CO2 two kinds of carrier gas and different pyrolysis temperatures of peanut shell biochar preparation, in the physical and chemical nature of differences, and adsorption properties of nitrate in water influence. At the same time, will be prepared with N2 as the biological carbon carrier gas after cleaning by Fe3+/Fe2+ solution mixing modification, biological carbon magnetization, to characterize the magnetic biological carbon composite material (scanning electron microscopy, infrared spectroscopy, X ray diffraction, elemental analysis, specific surface area), and discusses the adsorption the performance of nitrate magnetic adsorption of biochar in water. The results show that with the increasing of temperature, the biomass carbonization more fully, more than the surface area; the point of zero charge biological carbon carrier gas CO2 under the condition of improvement rate (9 ~ 20%) is about 2 times of the N2 atmosphere (6 ~ 10%); 700 DEG C, CO2 carrier gas under the condition of the biomass was caused by gasification C the loss of O element is introduced, and the obvious C-O bond to form a new biological activated carbon; modification of zero point of charge, biochar significantly increases the surface area; adsorption kinetics and thermodynamics, biological activated carbon on nitrate nitrogen adsorption capacity are weak, internal diffusion, electrostatic adsorption interaction in the adsorption process of nitrate nitrogen the adsorption performance is better than that of CO2 and N2 in biological carbon carrier gas prepared by the carrier gas conditions above 20%; the method of modification of biochar on nitrogen adsorption capacity decreased greatly.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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