核桃壳水热活性炭的制备及其吸附性能的研究

发布时间：2018-09-11 09:13

【摘要】：核桃壳是一种分布非常广泛的典型废弃生物质,是一种可再生、易生物降解的环境友好型天然资源。核桃壳作为制备炭材料的原料,可将废弃生物质资源转换为一种制备简单、性能优良的炭材料,是处理环境污染物的新型的环保材料。水热炭化制备水热炭材料是近年来研究功能性炭材料的课题。本研究选择核桃壳水热炭作为制备活性炭材料的前驱体,建立了制备水热活性炭的方法并对制备的水热活性炭材料各性能进行表征,结果如下：(1)在密闭的容器里,以水作为溶剂,温度对水热炭化过程的影响最为显著,调节温度在180-250℃范围内的变化,利用扫描电子显微镜、红外光谱、元素分析等手段表征产物,在温度240℃水热条件下,碳含量达到70.31%,且制备的炭材料热值随之提高。利用过程简单、条件温和的水热方法制备活化前驱体,为后续活化提供了基本的碳骨架结构,可降低整个制备活性炭工艺的成本。(2)选择碳含量最高的水热炭材料进行化学活化处理,考察活化温度(500、600、700、800、900℃)、活化时间(30、60、90、120、150 min)、碱炭比(1：1、2：1、3:1、4：1、5：1)对制备水热活性炭性能的影响。采用单因素统计分析和正交优化实验制备最优炭材料,通过探讨水热活性炭的结构、比表面积、孔径孔容以及对亚甲基蓝吸附性能等参数,综合评价制备水热活性炭的性能。实验结果表明240℃核桃壳水热炭作为改性的前驱体,活化温度为800℃,活化时间为120 min,碱炭比为3：1时,制备的活化水热炭性能最佳。此时,水热活性炭对亚甲基蓝的吸附量为498.52 mg/g,比表面积达2892.70 m2/g,总孔容为1.281 cm3/g,微孔孔容为0.416,表明制备的水热活性炭材料以微孔为主。其对亚甲基蓝的吸附性能优于传统制备活性炭的吸附性能,为水热活化方法深入研究提供基础数据。(3)通过对核桃壳水热活性炭吸附亚甲基蓝影响因素的分析,考察了吸附条件水热活性炭的投加量、初始浓度、初始pH以及停留时间对吸附过程的影响趋势,采用动力学和吸附等温线对实验数据进行拟合,并得到了相应的吸附常数和动力学常数。分析结果Langmuir模型能够更好地描述活化水热炭吸附量与吸附亚甲基蓝浓度的关系,准二级动力学模型可描述活化水热炭吸附亚甲基蓝的动力学过程,拟合相关系数R2达0.99965。
[Abstract]:Walnut shell is a kind of typical waste biomass which is widely distributed. It is a kind of renewable and biodegradable environment-friendly natural resource. Walnut shell can be used as a raw material to prepare carbon materials, which can convert the waste biomass resources into a kind of carbon material with simple preparation and good performance. In this study, walnut shell hydrothermal carbon was selected as the precursor of the preparation of activated carbon materials, and the preparation method of hydrothermal activated carbon was established. The properties of the prepared hydrothermal activated carbon materials were characterized. The results are as follows: (1) In an airtight container, water was used as the precursor of the preparation of activated carbon materials. Solvent and temperature have the most significant effect on hydrothermal carbonization process. The product is characterized by scanning electron microscopy, infrared spectroscopy and elemental analysis. Under hydrothermal condition of 240 C, the carbon content reaches 70.31%, and the calorific value of the prepared carbon material increases with the increase of temperature. (2) The hydrothermal carbon materials with the highest carbon content were selected for chemical activation treatment, and the activation temperature (500,600,700,800,900 C), activation time (30,60,90,120,150 min), alkali-carbon ratio (1:1,2:1,2,1,000) were investigated. The effects of 3:1,4:1,5:1) on the properties of hydrothermal activated carbon were studied. The optimum carbon materials were prepared by single factor statistical analysis and orthogonal experiment. The properties of hydrothermal activated carbon were comprehensively evaluated by investigating the structure, specific surface area, pore size and adsorption properties of methylene blue. When the activation temperature is 800 C, the activation time is 120 min and the ratio of alkali to carbon is 3:1, the performance of the prepared activated hydrothermal carbon is the best. Hydrothermal activated carbon materials mainly consist of microporous materials. Its adsorption performance for methylene blue is better than that of traditional activated carbon, which provides basic data for further study of hydrothermal activation methods. (3) Through the analysis of influencing factors of adsorption of methylene blue on walnut shell hydrothermal activated carbon, the dosage and initial concentration of hydrothermal activated carbon were investigated. The kinetic and adsorption isotherms were used to fit the experimental data, and the corresponding adsorption constants and kinetic constants were obtained. The Langmuir model can better describe the relationship between the adsorption capacity of activated hydrothermal carbon and the concentration of methylene blue, and the quasi-second-order kinetic force. The kinetic process of adsorption of methylene blue on activated hydrothermal carbon can be described by the model. The fitting correlation coefficient R2 is 0.99965.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ424.1;X505

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