废弃生物质制备碳材料及其底泥修复与储能应用研究

发布时间：2018-04-19 10:25

本文选题：稻壳生物炭 + 底泥　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：作为可再生资源,农林废弃生物质的利用引起人们的极大关注。与露天焚烧相比,生物质热解是一种绿色、低污染的处理方法,其产物主要包括生物炭、生物油和热解气。本论文研究了生物质热解得到的生物炭在环境及储能方面的应用,以及利用热解气合成碳纳米材料。其中,稻壳生物炭用作底泥修复剂,来限制底泥中污染物的释放,防止污染物向上覆水迁移。生物质热解得到的氮掺杂多孔碳材料有着较好的电化学性能,能用作超级电容的电极材料。最后利用各种生物质热解气合成3D石墨烯泡沫,实现了废气的资源化。论文的具体研究内容和结果如下:1.底泥中污染物的释放是人们比较关心的话题,作为低成本和无毒的材料,稻壳生物炭可以实现对污染底泥的原位修复。在实验中,我们用不同厚度的生物炭(0.62,1.25,3.33和6.20 mm)对铜离子和4-氯酚污染的底泥进行修复。结果显示,在pH为5或7时,一定厚度的生物炭可以有效抑制铜和4-氯酚的释放,并使水体中污染物浓度符合相关国家标准。对于pH为3的高酸性水体,与空白组相比,6.20 mm厚的生物炭可以把上覆水中铜离子的浓度减少10倍以上。释放动力学模拟结果说明,生物炭的加入可以增加污染物的传质阻力,多孔表面和丰富的官能团抑制了污染物从底泥向水体的释放。2.用麦秸秆生物质作为碳源,三聚氰胺作为氮源,混合盐作为反应溶剂和造孔剂,一步制备得到了氮掺杂的多孔生物质基碳材料。超级电容器电极测试结果显示,氮含量为7.78%的材料有着较高的电容性能(447 F/g),其主要原因是在盐模板活化反应中氮掺杂和比表面的提高。同时,在最佳掺杂比例下(1g生物质:1g三聚氰胺),热解产物中硅的去除有助于提高材料电容性能,但是热解前原材料直接去硅对材料的电化学性能有负面影响,这是因为硅在热解掺氮过程中能够催化活性氮形成,并在后续的处理中起着造孔作用。3.生物质热解过程中产生的大量废气通常随惰性载气一起被排放,造成大气污染。在实验中,我们采用热重力学分析和傅里叶红外变换联用技术(TGA-FTIR)对纤维素和木质素的热解气相产物进行了分析,发现气相产物主要包含小分子烷烃类、CO_2、H2O和挥发性有机物(冷凝到生物油中)。然后我们用两种生物质的热解气作为碳源,利用耦合的快速热解和常压气相沉积设备合成了 3D寡层石墨烯泡沫结构,并采用同样的操作方法,利用麦秸秆生物质和锯末的热解废气制备了 3D寡层石墨烯泡沫结构,证实了该方法在生物质热解气增值化应用方面的可行性。
[Abstract]:As a renewable resource, people pay great attention to the utilization of abandoned biomass in agriculture and forestry.Compared with open burning, biomass pyrolysis is a green, low-pollution treatment method, and its products mainly include bio-carbon, bio-oil and pyrolysis gas.In this paper, the application of biochar obtained from biomass pyrolysis in environment and energy storage, and the synthesis of carbon nanomaterials by pyrolysis gas were studied.Among them, rice husk biochar is used as sediment remediation agent to limit the release of pollutants from sediment and prevent pollutants from migrating to overlying water.Nitrogen doped porous carbon materials obtained from biomass pyrolysis have good electrochemical properties and can be used as electrode materials for super capacitors.Finally, 3 D graphene foam was synthesized from various biomass pyrolysis gases, and the waste gas was reused.The specific contents and results of this paper are as follows: 1.The release of pollutants from sediment is a topic of concern. As a low-cost and non-toxic material, rice husk biochar can be used for in-situ remediation of contaminated sediment.In the experiment, the copper ion and 4-chlorophenol contaminated sediment were remedied with different thickness of biochar (0.62 ~ 1.253.33 and 6.20 mm).The results showed that when pH was 5 or 7, the release of copper and 4-chlorophenol could be effectively inhibited by a certain thickness of biochar, and the concentration of pollutants in the water could meet the relevant national standards.For the highly acidic water with pH 3, the concentration of copper ion in the overlying water can be reduced by more than 10 times with the biological carbon of 6.20 mm thick compared with the blank group.The release kinetics simulation results show that the addition of biochar can increase the mass transfer resistance of pollutants, and the porous surface and abundant functional groups inhibit the release of pollutants from sediment to water.Using wheat straw biomass as carbon source, melamine as nitrogen source, mixed salt as reaction solvent and pore making agent, nitrogen-doped porous biomass based carbon materials were prepared in one step.The results of electrode test of supercapacitor show that the material with 7.78% nitrogen content has high capacitance performance (447F / g / g), which is mainly due to the increase of nitrogen doping and specific surface area in the activation reaction of salt template.At the same time, the removal of silicon from pyrolysis products can improve the capacitive properties of the materials under the optimum doping ratio of 1 g biomass to 1 g melamine, but the direct removal of silicon from the raw materials before pyrolysis has a negative effect on the electrochemical properties of the materials.This is because silicon can catalyze the formation of active nitrogen in the process of pyrolysis and doping nitrogen, and play a role of pore making in the subsequent treatment.A large amount of waste gas produced during biomass pyrolysis is usually discharged along with inert carrier gas, resulting in air pollution.In the experiment, the pyrolysis gas phase products of cellulose and lignin were analyzed by thermogravimetry and Fourier transform infrared transform (FTIR).It is found that the gaseous products mainly contain small molecular alkanes such as CO _ 2H _ 2O and volatile organic compounds (condensed into bio-oil).Then we used pyrolytic gas of two kinds of biomass as carbon source, using coupled rapid pyrolysis and atmospheric pressure vapor deposition equipment to synthesize 3D oligolayer graphene foam structure, and adopted the same operation method.The 3D oligographene foam structure was prepared by pyrolysis waste gas from wheat straw and sawdust, which confirmed the feasibility of this method in the application of biomass pyrolysis gas increment.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;X52

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