改性催化剂可见光下降解水体中四环素类抗生素的研究

论文总字数：31753字

摘 要

：四环素作为一种广谱抑制剂，是一种优质价廉的抗生素，它可以在低浓度时用作生长促进剂，高浓度时用于治病的药类，在我国畜牧业和临床医学中被大量的使用。持续不断的进入环境，加上因所处环境的不同而表现出不同的降解性能，四环素在环境中广泛存在，不断累积，因此必须开发持续高效的治理技术，降低四环素对环境的破坏作用。最近，聚合物半导体石墨相氮化碳( g-C₃N₄ )，由于其优异的化学稳定性和独特的电子能带结构，被作为一种廉价、稳定、不含金属组分的可见光光催化剂广泛应用于太阳能的光催化转化及污染物的降解。

本文采用改性石墨相氮化碳g-C₃N₄作为主要的环境修复剂，通过其在可见光下的光催化效应降解四环素，从而降低四环素对环境的负面影响。论文主要研究了催化剂的制备及改性对催化剂降解四环素性能的影响。首先研究催化剂前驱物对催化剂催化性能的影响，其次探究了催化剂制备过程中升温速度和升温方式对催化剂催化性能的影响，然后研究了催化剂改性过程中掺杂的金属种类和含量对降解性能的影响，最后研究了氮化碳催化剂与金属氧化物P₂₅复合对催化性能的影响。在实验中，为了验证催化剂是否制备成果及探讨改性后催化剂对光吸收范围的变化，分别对催化剂进行了XRD及UV-vis表征。

实验结果如下：

1. 催化剂前驱物对催化性能的影响

选取了制备g-C₃N₄常用的两种前驱物：三聚氰胺和二氰二胺。研究表明，两者的催化效果类似，但是采用三聚氰胺制备的g-C₃N₄催化效果要略好于采用二氰二胺作为前驱物制备的g-C₃N₄。因此后续的研究过程中，催化剂的制备都采用了三聚氰胺作为催化剂的前驱物进行煅烧。

2. 催化剂制备过程中升温条件的影响

分一段式升温和两段式升温进行探究。一段式升温方式为以2.3℃/min升温至520℃，在此温度下煅烧4h；两段式升温即先升至500℃，在此温度下保持2h，再升温至520℃保持2h，同时两段式升温过程中分别采用了2.3℃/min，10℃/min，20℃/min三种不同的升温速度，研究升温速度对降解效果的影响。研究表明两段式的升温方式明显优于一段式直接升温，此外，在两段式升温过程的三种升温速度下制备的g-C₃N₄对污染物的降解区别不明显，但采用2.3℃/min升温速度制备的催化剂催化效果略好，即升温速度越慢，催化剂催化性能越好。因此，实验采用两段式升温进行催化剂的制备，升温速度选择2.3℃/min。

3. g-C₃N₄复合金属改性的影响

研究了g-C₃N₄与不同金属掺杂（铁、锰、银、铜四种金属），及不同掺杂量对催化效果的影响。实验结果表明，掺杂金属的种类不同，催化效果差别很大。以之前纯g-C₃N₄最佳的降解率15%的数据来看，与硝酸铁的掺杂过程中，掺杂过少或者过多的Fe对污染物降解都有负面的效果。光在与硝酸铜的掺杂实验中，催化效果随着掺杂量的增多而增多。在与硝酸银的掺杂实验中，银的加入让催化剂的光催化效果都有了不同程度的下降，在浓度较高的时候光催化效率甚至降至0。最后复合醋酸锰的实验中，在选择的三个掺杂比下，降解率都有不同程度下的提升，但是值得注意的是高掺杂比的条件下，锰在光反应阶段受到的影响很大，在10%的质量比掺杂的条件下，降解率下降至0。

5. 与P25的复合对催化剂催化性能的影响

在与P25的复合试验中，发现随着P25的掺杂量的不断上升，催化降解率先增大后减少，以p25与三聚氰胺复合比为1:4时为最高。且这几组数据的降解率都要远大于前几组的改性结果。为了研究这样的降解率是P25单方的结果还是两种催化剂在复合过程中互相促进的结果。本论文研究了p25投加量以及C₃N₄投加量与降解率的关系图，通过计算发现在不同投加比的情况下，两者复合的效果都比单独投加有着一定的增加，特别是在p25与三聚氰胺投加比为1:4时，两者的促进作用最为明显。

上述的实验表明，在催化剂制备过程中，升温速度对于催化剂的催化效果的影响不大，但是升温方式影响明显，两段式的升温方法要明显优于一段式的。在催化剂改性方面，选择复合的金属种类以及掺杂比对催化剂的催化效果影响都很大，在不适当的金属选择以及不适当的掺杂比的情况下会达到负面的效果。降解效果最为明显的是与P₂₅复合,复合后的催化剂降解效果明显优于未改性的催化剂，这一部分归因于P₂₅材料对于四环素有着较为优越的催化能力，同时两种催化剂的互相促进作用也是相当的明显。

关键词：g-C₃N₄，四环素，光催化降解，改性、复合

Abstract：Tetracycline as a broad-spectrum inhibitor, is a high quality and cheap antibiotics, it can be used as a growth inhibitor at low concentrations, high concentrations of drugs used in the treatment of animal husbandry and clinical medicine in China A lot of use. Continuous introduction of the environment, coupled with the different environment due to the different performance of degradation, tetracycline in the environment widely present, and constantly accumulate, it must develop sustained and efficient management techniques to reduce the destruction of tetracycline on the environment. Recently, the polymer semiconductor graphite phase carbonitride (g-C3N4), due to its excellent chemical stability and unique electronic band structure, is widely used as an inexpensive, stable, non-metallic component of visible light photocatalyst Photocatalytic conversion of solar energy and degradation of pollutants.

In this paper, modified graphite phase carbon nitride g-C3N4 as the main environmental repair agent, through its visible light in the photocatalytic degradation of tetracycline, thereby reducing the negative impact of tetracycline on the environment. The effect of preparation and modification of catalyst on the degradation of tetracycline was studied. The effects of catalyst precursor on the catalytic performance of the catalyst were studied. Secondly, the effects of the heating rate and the heating mode on the catalytic performance of the catalyst were investigated. The effects of the metal species and content on the catalytic performance of the catalyst were investigated. The effect of the combination of carbon nitride catalyst and metal oxide P25 on the catalytic performance was studied. In order to verify the preparation results of the catalyst and to investigate the change of the light absorption range of the modified catalyst, the catalysts were characterized by XRD and UV-vis.

The results are as follows:

1. Effect of catalyst precursor on catalytic performance

    Two kinds of precursors commonly used in the preparation of g-C3N4 were selected: melamine and dicyandiamide. The results show that the catalytic effect of the two is similar, but the g-C3N4 catalyzed by melamine is slightly better than that of g-C3N4 prepared by using dicyandiamide as the precursor. Therefore, the subsequent research process, the preparation of the catalyst are used melamine as a precursor of the catalyst for calcination.

2. Effect of heating conditions on the preparation of catalyst

Sub-level heating and two-stage heating to explore. The temperature of the two-stage heating up to 500 ℃, at this temperature for 2h, and then heated to 520 ℃ for 2h, while the two The effects of the heating rate on the degradation efficiency were studied by using three different heating rates at 2.3 ℃ / min, 10 ℃ / min and 20 ℃ / min respectively. The results show that the two-stage heating method is better than the one-stage direct heating temperature. In addition, the degradation of the pollutants prepared by g-C3N4 at the three heating rates of the two-stage heating process is not obvious, but using 2.3 ℃ / min The catalytic effect of the catalyst prepared by the heating rate is slightly better, that is, the slower the heating rate is, the better the catalyst performance is. Therefore, the experiment uses two-stage heating for the preparation of the catalyst, the heating rate of choice 2.3 ℃ / min.

3. Effect of g-C3N4 composite metal modification

The effects of g - C3N4 and different metals (iron, manganese, silver and copper) on the catalytic effect were studied. The experimental results show that the catalytic effect is very different. In the case of the best degradation rate of pure g-C3N4 of 15%, the doping with iron nitrate has a negative effect on the degradation of contaminants. The degradation rate of light

reaction, dark reaction and total reaction is about the same as the change of metal doping amount. In the doping experiment with copper nitrate, the catalytic effect increases with the increase of the doping amount, and the degradation rate of the dark reaction and the photoreaction phase also increases synchronously. In the experiment with silver nitrate, the photocatalytic effect of the catalyst was decreased in different degree, and the photocatalytic efficiency was even reduced to 0 when the concentration was high. In the final compound manganese acetate experiment, the degradation rate was improved in different degrees under the selected three doping ratios, but it is noteworthy that the effect of manganese on the photoreaction stage is very high The degradation rate decreased to zero at 10% mass ratio under doping conditions.

4.Effect of P.25 on Catalytic Performance of Catalyst

    In the composite experiment with P25, it was found that with the increase of the doping amount of P25, the catalytic degradation rate increased first and then decreased, and the ratio of p25 to melamine was 1: 4. And the degradation rate of these groups of data should be much larger than the previous group of modified results. In order to study this degradation rate is the result of P25 unilateral or the two catalysts in the composite process to promote the results of each other. In this paper, we study the relationship between the dosage of p25 and the dosage of C3N4 and the rate of degradation. It is found that the effect of the combination is different from that of the individual dosing, P25 and melamine dosing ratio of 1: 4, the two promote the most obvious role.

    The above experiments show that the heating rate has little effect on the catalytic effect of the catalyst during the preparation of the catalyst, but the effect of the heating mode is obvious, and the two-stage heating method is better than the one-stage. In the catalyst modification, the choice of composite metal species and the doping ratio have a great effect on the catalytic effect of the catalyst, and the negative effect is achieved in the case of improper metal selection and improper doping ratio. The degradation effect of P25 is better than that of unmodified catalyst. This part is attributed to the fact that the P25 material has a superior catalytic ability for tetracycline, and the mutual promotion of the two catalysts is also Quite obvious.

   

Keywords: g-C3N4, tetracycline, photocatalytic degradation, modification, recombination

目录

1. 绪论 1

1.1. 四环素简介 1

1.1.1. 四环素污染现状 1

1.1.2. 四环素的性质 1

1.1.3 四环素的环境毒性 1

1.2. 四环素治理 1

1.2.1. 生物处理 2

1.2.2. 物理法 2

1.2.3. 化学法 2

1.2.4. 高级氧化法 3

1.2.5. 生态修复法 3

1.2.6. 总结 3

1.3. 石墨相氮化碳（g-C₃N₄）光催化氧化技术概述 4

1.3.1. 光催化氧化机理 4

1.3.2. g-C₃N₄性质 4

1.3.3. 影响g-C₃N₄的光催化活性因素 4

1.4. 研究目的意义和内容 6

1.5. 本课题技术路线 8

1. 实验设计 9

2.1. 实验材料和仪器 9

2.1.1. 实验材料 9

2.1.2. 仪器 9

2.2. 催化剂的制备 9

2.2.1. 不同前驱物g-C₃N₄光催化剂 9

2.2.2. 不同升温条件下g-C₃N₄光催化剂的制备 10

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