碳热法合成纳米零价铁活性炭方法和吸附性能研究

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摘要

本实验主要研究碳热还原法将纳米零价铁负载到活性炭上并用于去除水中污

染物的去除。具体来说是在氮气氛围下通过改变碳热合成温度（350℃到 1150℃）

来制备纳米零价铁/活性炭。合成材料含铁量分析表明纳米零价铁能够成功地负载

到活性炭上。研究过程当中对纳米零价铁/活性炭的主要性质进行了透射电镜

（TEM）、 X射线衍射（XRD）、红外光谱仪（FTIR）、比表面积和孔径分布（BET）

表征。TEM 表征显示，碳热还原法处理可以使铁粒子很好的分散在活性炭上。经

350℃处理后的材料中，负载在活性炭表面上的纳米铁的粒径在 10 nm 左右。随着

处理温度的升高，铁粒子在活性炭内的分散性要更好。XRD 表征显示，碳热改性

后活性炭上有氧化铁和单质铁的存在，且随着碳热合成温度升高，更多的氧化铁会

被还原成单质铁。但是碳热还原温度太高会破坏活性炭本身的结构，降低合成材料

的吸附还原性能。FTIR 表征显示，碳热法合成材料表面有水、氧化铁、对称和非

对称亚甲基以及碳碳双键和脂族的存在。BET 表征结果表明，纳米铁加载到活性

炭的微孔和中孔中，进而影响到活性炭比表面积和孔径分布。纳米铁的加载使得活

性炭的孔体积和比表面积都有不同程度的减小，且减小的程度与碳热还原温度有

关。

实验中以铬为目标污染物研究了合成材料对重金属的吸附还原能力。分别利

用投加量实验、吸附平衡实验和吸附动力学实验来确定最佳投加量和比较改性前

后活性炭对重金属铬的吸附还原能力和吸附速率。投加量实验研究表明，纳米零价

铁/活性炭最佳投加量为 2 g/L。吸附平衡实验的结果表明其去除重金属的过程与

Langmuir 模型相吻合。Langmuir 吸附常数 qmax 表征纳米零价铁/活性炭在吸附达

到平衡时的最大吸附能力。从 qmax 的结果可以看出，碳热还原法负载纳米零价铁

能有效提高活性炭对六价铬的去除能力。其中又以 550℃条件下的改性最优。经

550℃改性后，活性炭对六价铬的吸附量可高达 89.29 mg/g，是改性前的 3倍左右。

吸附动力学试验则表明，纳米零价铁/活性炭对六价铬的吸附较快，与重铬酸盐还

原吸附 50 分钟后，六价铬去除率可达 90%以上。动力学模拟表明反应更符合二级

反应动力学模型。研究中对六价铬的去除机理也进行了探讨。纳米零价铁/活性炭

对六价铬的吸附过程中是由活性炭吸附和纳米零价铁还原共同作用。实验中还研

究了 pH 值和阴离子浓度对反应的影响，结果表明：pH 值越低，材料的吸附还原

效果越好，反应后溶液的 pH 值会升高。氯离子和硫酸根离子对反应的影响很小，

而磷酸根离子对反应有强烈的抑制作用。分别利用液相还原沉淀法和碳热还原法

制备纳米零价铁/活性炭，目的是为了比较不同合成方法对纳米零价铁/活性炭的物

化性质和去除重金属能力的影响。实验最后研究了保存方法和时间对材料的影响，

结果表明：密闭干燥保存 90 天后材料的物化性质基本未发生改变，对六价铬的去

除效率未发生明显变化。

关键词：纳米零价铁活性炭还原沉淀法碳热法铬

ABSTRACT

Activated carbon supported nano zero-valent iron was synthesized through a

carbothermal reduction process. Specifically, iron loaded carbon was thermally treated

under N2 atmosphere and at temperatures ranged from 350 to 1150℃. Iron content

analysis indicated that iron was successfully deposited on activated carbon. Major

properties of the synthesized materials were obtained through analysis of iron content,

characterization through TEM, XRD, FTIR and surface area analysis. Iron particles

produced from carbothermal reduction process were highly dispersed on activated carbon

based on TEM images. The size of these particle after 350℃ treatment is about 10 nm.

In addition, the dispersion of iron improved with the increase of processing temperature.

Results from XRD showed that zero-valent iron and iron oxides were present and a

progressive reduction of iron oxide-to elemental iron was observed during the

carbothermal process. However, extreme high temperature could result in the destruction

of the structure of activated carbon. The material surface have water, ferric oxide,

symmetric and asymmetric methylene, carbon carbon double bond and aliphatic based on

FTIR. Iron nanoparticles were loaded in activated carbon micropores and mesopores, thus

led to a decreased in both specific surface area and pore size distribution based on BET

and pore volume analysis.

Synthesized materials were tested for their reactivity for chromate. Batch dosage

experiment, adsorption isotherm and adsorption kinetics experiments were employ to

determine the optimal dosage, maximum adsorption capacity and reaction rates. Results

showed that the optimum dosage is around 2 g/L. Adsorption isotherm tests proved that

adsorption fit the Langmuir adsorption model well. By comparing the Langmuir

maximum adsorption capacity qmax, it appeared that carbothermal reduction process can

effectively improve the ability of activated carbon to remove hexavalent chromium. And

carbothermal treatment at 550℃ achieved the highest adsorption of 89.29 mg/g which is

3 times more than that of virgin activated carbon. Adsorption kinetics experiment shows

that nano zero-valent iron/activated carbon adsorb hexavalent chromium quickly. 90% of

hexavalent chromium was removed after 50 min of contact using with products

synthesized at 550℃. Kinetics model fitting showed that chromate adsorption abide by

the assumption of secondary reaction kinetics.

The mechanism of hexavalent chromium removal was also studied in this study. Nano

zero-valent iron/activated carbon was able to removal chromate through by adsorption by

activated carbon and reduction by nano zero-valent iron. Experiments were conducted to

further study the influence of pH and anion concentration on the removal process. The

results showed that: the lower the pH, the higher the removal and solution pH rose after

the reaction. Chlorine ion and sulfate ion had little impact on the removal while phosphate

ions presented a strong inhibitory effect. At the end of study, experiments were designed

to investigate the effect of preservation method and time on the material. It seems that

airtight dry preservation could maintain the material’s physical and chemical properties

after 90 days. The removal efficiency of hexavalent chromium did not change

significantly.

Key Word: nano zero-valent iron, activated carbon, liquid-reduction,

carbothermal synthesis, chromate

中文摘要

ABSTRACT

第一章绪论 ........................................................ 1

1.1 研究的背景与意义 ............................................ 1

1.2 重金属废水处理技术现状 ...................................... 1

1.2.1 化学法 .................................................. 1

1.2.2 物理法 .................................................. 2

1.2.3 生物法 .................................................. 3

1.3 活性炭及活性炭改性 .......................................... 4

1.3.1 活性炭的分类 ............................................ 4

1.3.2 活性炭的孔隙性质 ........................................ 6

1.3.3 活性炭在水处理中的应用 .................................. 6

1.3.4 活性炭改性 .............................................. 8

1.4 零价铁技术发展现状 .......................................... 9

1.4.1 零价铁还原技术机理 ..................................... 10

1.4.2 纳米零价铁还原技术 ..................................... 11

1.5 纳米零价铁/活性炭的制备 ..................................... 11

1.6 本文主要研究内容 ............................................ 12

第二章实验材料和方法 .............................................. 14

2.1 主要试剂及仪器 ............................................. 14

2.1.1 主要试剂 ................................................ 14

2.1.2 主要实验仪器 ............................................ 14

2.2 试验方法 ................................................... 15

2.2.1 纳米零价铁/活性炭的制备方法 ............................ 15

2.2.2 重金属去除实验 .......................................... 15

2.3 分析方法 ................................................... 17

2.3.1 纳米零价铁/活性炭负载量分析 ............................ 17

2.3.2 六价铬的分析方法 ........................................ 17

2.3.3 总铬的分析方法 .......................................... 18

2.3.4 材料表征结构分析 ........................................ 19

2.4 本章小结 ................................................... 20

第三章纳米零价铁/活性炭的表征 ..................................... 21

3.1 纳米零价铁/活性炭含铁量分析 ................................. 21

3.2 纳米零价铁/活性炭 TEM 分析 ................................... 22

3.3 纳米零价铁/活性炭 XRD 分析 ................................... 23

3.4 纳米零价铁/活性炭 FTIR 分析 .................................. 24

3.5 纳米零价铁/活性炭比表面积和孔径分布 ......................... 25

3.6 本章小结 ................................................... 26

第四章纳米零价铁/活性炭还原降解重金属铬的研究 ..................... 27

4.1 投加量对纳米零价铁/活性炭反应的影响 ........................ 27

4.2 吸附平衡实验 ............................................... 28

4.3 反应动力学研究 ............................................. 30

4.4 反应机理研究 ............................................... 31

4.5 pH 值对反应的影响 ........................................... 33

4.6 阴离子浓度对反应的影响 ...................................... 35

4.7 碳热法制备纳米零价铁/活性炭的保存 ........................... 35

4.7.1 保存时间对纳米零价铁/活性炭的影响 ...................... 36

4.7.2 保存时间对纳米零价铁/活性炭吸附还原重金属的影响 ......... 37

4.8 本章小结 ................................................... 37

第五章碳热还原法与液相还原法制备方法的比较研究 .................... 39

5.1 合成材料的物化性质 ......................................... 39

5.2 合成材料对金属铬的去除 ...................................... 42

5.3 本章小结 .................................................... 43

第六章结论与展望 .................................................. 44

参考文献 ........................................................... 48

在读期间公开发表的论文和承担科研项目及取得成果 ..................... 54

致谢 ............................................................. 55

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摘要：

摘要本实验主要研究碳热还原法将纳米零价铁负载到活性炭上并用于去除水中污染物的去除。具体来说是在氮气氛围下通过改变碳热合成温度（350℃到1150℃）来制备纳米零价铁/活性炭。合成材料含铁量分析表明纳米零价铁能够成功地负载到活性炭上。研究过程当中对纳米零价铁/活性炭的主要性质进行了透射电镜（TEM）、X射线衍射（XRD）、红外光谱仪（FTIR）、比表面积和孔径分布（BET）表征。TEM表征显示，碳热还原法处理可以使铁粒子很好的分散在活性炭上。经350℃处理后的材料中，负载在活性炭表面上的纳米铁的粒径在10nm左右。随着处理温度的升高，铁粒子在活性炭内的分散性要更好。XRD表征显示，碳热改性后活性...

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