秸秆生物炭的制备及对水中镉的吸附特性研究

论文总字数：28646字

摘 要

随着工业化与城市化进程，重金属污染越来越严重。如今水土环境中的重金属治理研究已经逐步受到人类的重视。重金属的治理方法有很多，而生物炭作为一种原料来源简单且廉价的吸附剂，所以具有广泛的研究前景。生物炭是生物质在无氧环境下的热解产物。生物炭的表面的多孔结构以及含氧官能团都使得生物炭对镉有较强的吸附效果。所以我们需要做的就是对生物炭的原料，工艺参数，以及设备的选择进行规划，清楚生物炭吸附重金属以及其他污染物的吸附机理，然后对生物炭进行改性，从而使生物炭更充分的应用于污染物的治理。

本论文采用选取了秸秆、黑麦草、椰壳、杏壳以及松木这五种生物质原料制备生物炭，随着热解温度升高，生物炭的的得炭率越低，灰分在逐渐升高，挥发分在缓慢的降低， pH不断升高。对生物炭进行表征分析，发现生物炭的表面粗糙，具有明显的孔隙结构，秸秆、黑麦草的比表面积相对较高，分别为163.32 m²/g和120.67 m2/g，生物炭中主要含有C、O元素以及很多的Si元素。由吸附实验优选出秸秆生物炭，其对重金属镉的去除率达到92.88%；选择600℃为最佳热解温度，最佳溶液pH为6；随着镉溶液初始浓度的不断增加，生物炭的吸附量在不断增加，但是去除率却在不断下降；几乎所有的生物炭在吸附4h时就已经达到了吸附平衡。选取五种改性剂（FePO₄、CO(NH)₂、H₂O₂、HNO₃、H₂O₂ HNO₃）对优选出来的秸秆生物炭进行改性，发现通过浸渍改性出来的生物炭对Cd的去除率都有所下降，水洗至中性之后对Cd的吸附量有明显提高；通入氮气加热之后，生物炭的比表面积增加，生物炭对Cd的吸附效果都有明显增加。通过对改性后生物炭的表征研究，发现生物炭有更高含量的C元素，更少含量的Si元素；改性后的孔容变大，孔数变多；经硝酸过氧化氢和通气加热改性均使生物炭比表面积增大；改性后的生物炭比表面积增加了126.38m²/g， 所以这都解释了改性之后生物炭吸附效果更好的原因。

关键词：镉污染；生物炭；热解；改性；吸附

Preparation of straw biochar and adsorption characteristics of cadmium in water

03213723 Haitao Ma

Supervised by Yaping Zhang

Abstract：With the process of industrialization and urbanization, heavy metal pollution is becoming more and more serious. Nowadays, the research on heavy metal control in water and soil environment has been paid more and more attention by mankind. There are many ways to control heavy metals, and biochar as a raw material source of simple and inexpensive adsorbent, so it has a wide range of research prospects. Biochar is the matter produced by pyrolysis of biomass in an anaerobic environment. The porous structure of the surface of the biochar and the oxygen-containing functional groups all make the biochar have a strong adsorption effect on cadmium. Therefore, we need to do is to bio-carbon raw materials, process parameters, as well as the choice of equipment planning, and clear the adsorption of bio-carbon adsorption of heavy metals and other pollutants mechanism, then modify the biochar so that biochar is more fully applied to the treatment of pollutants.

This paper uses the straw, ryegrass, coconut shell, apricot shell, and pine biomass for biochar, found that the higher the pyrolysis temperature, biochar carbon rate is lower, ash is gradually rise, volatile in slowly decrease, and pH is rising. Characterization analysis recognizes the rough surface of biochar, with apparent pore structure, straw, ryegrass relatively high specific surface area of 163.32 m²/g and 120.67 m²/g, biochar mainly contains elements of C, O, also contains a lot of Si. The removal rate of heavy metal cadmium was 92.88% by straw biochar. We choose 600 ℃ for best pyrolysis temperature, solution pH of 6; As the initial concentration of cadmium has increased, the absorption of biochar has been increasing, but the removal rate has been declining. Almost all biochar has reached the adsorption equilibrium when adsorbed 4h. Choose five kinds of modifying agent (FePO₄, CO(NH) ₂, H₂O₂, HNO₃ and H₂O₂ HNO₃) on modification and optimization of straw biochar found by dipping modification of biochar is decreased to the removal rate of Cd, after the water washing to neutral on Cd adsorption quantity has increased significantly; After nitrogen heating, the biochar has increased over the surface area, and the effect of biochar on Cd has increased significantly. Through the characterization of the modified biochar, it is found that the carbon has higher content of C, and the lower content of Si elements. After modification, the pores are enlarged and the holes are enlarged. The modification of hydrogen peroxide and ventilatory heating made biochar larger than surface area. The modified biochar increased by 126.38 m2 / g, so this explains why biochar adsorption was better after modification.

Key words: Cadmium pollution; Biochar; Pyrolysis; modified; The adsorption

目 录

1 绪论 1

1.1 重金属污染现状 1

1.2 镉污染现状 1

1.2.1 镉污染来源 1

1.2.2 镉的危害 2

1.3 重金属的处理方法 2

1.4 生物炭及其应用研究 3

1.4.1 生物炭制备技术 3

1.4.2 生物炭的性质 3

1.4.3 生物炭的吸附机理 4

1.4.4 生物炭的应用 4

1.5 研究意义和研究内容 6

1.5.1 研究意义 6

1.5.2 研究内容 6

1.5.3 研究路线 8

2 实验材料仪器与方法 9

2.1 实验仪器与试剂 9

2.2 实验方法 10

2.2.1 生物炭制备 10

2.2.2 生物炭吸附实验 10

2.2.3 生物炭改性实验 11

2.2.4 生物炭表征分析 12

3 生物炭的制备与表征 14

3.1 不同原料生物炭的制备 14

3.2 不同热解温度下生物炭的制备 14

3.2.1 产率分析 14

3.2.2 灰分、挥发分以及pH分析 15

3.3 生物炭表征分析 16

3.3.1 BET分析 16

3.3.2 SEM分析 16

3.3.3 EDS元素分析 17

3.3.4 FTIR分析 18

3.4 本章小结 19

4 生物炭的Cd吸附实验 20

4.1 不同原料生物炭对Cd吸附实验的影响 20

4.2 不同热解温度的生物炭对Cd吸附实验的影响 20

4.3 不同的溶液pH值对镉吸附实验的影响 21

4.4 不同的Cd浓度对吸附实验的影响 22

4.5 不同吸附时间对吸附试验的影响 23

4.6 本章小结 24

5 生物炭改性研究 26

5.1 生物炭改性实验 26

5.1.1 浸渍以及水洗至中性改性 26

5.1.2 通氮气改性 27

5.2 改性生物炭表征分析 28

5.2.1 EDS能谱分析 28

5.2.2 SEM电镜分析 28

5.2.3 红外分析(FTIR) 29

5.2.4 BET表征分析 30

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