负载型催化剂对水族箱中氨氮、亚硝态氮降解的研究

论文总字数：34428字

摘 要

水族业对人类十分重要，而过高的氨氮与亚硝态氮会导致水生生物的生长繁殖受到限制，因此有效地控制水族箱中的氮含量是十分必要的。本文采用了光催化氧化还原来进行氮含量的控制，旨在研究改性光催化剂在可见光照射条件下，pH为水族箱中鱼类能适应范围内，对于水中氨氮以及亚硝酸氮的去除能力。采用溶胶凝胶法制备出N-Fe-TiO₂、N-Cu-TiO₂ ，采用焙烧法制备出N-C-TiO₂共三种双元素掺杂改性半导体光催化剂，并且经过实验比对了不同制备条件下产生的各改性半导体催化剂分别对氨氮和亚硝态氮的降解效率，并且对可能出现的现象进行系统分析，找出现象的形成原因。讨论了筛选出的最佳催化剂的负载载体和负载方式，并进行负载型催化剂对氨氮的降解实验，得出以下结论：

1. 在所选的几种双元素掺杂的TiO₂光催化剂中，在使用300w氙灯为可见光源，pH恒定为8，催化剂投加量为1g/L，氨氮与亚硝态氮初始浓度都为1mg/L，可见光照射的条件下，半导体光催化剂N-C-TiO₂-550℃对溶液中的氨氮的降解率达到76%；N-Fe-TiO₂改性半导体光催化剂对氨氮的降解率达71%，这说明半导体光催化剂N-C-TiO₂-550℃和N-Fe-TiO₂均对氨氮具有显著的降解能力。
2. 在使用300w氙灯为可见光源， pH恒定为8，催化剂投加量为1g/L，可见光照射的条件下，亚硝态氮的浓度会影响氨氮的降解，在氨氮与亚硝态氮浓度比例1:1的条件下，N-C-TiO₂-550℃对于氨氮的降解率比在氨氮与亚硝态氮浓度比例10:1的条件下高出26个百分点；N-Fe-TiO₂在氨氮与亚硝态氮浓度比例1:1的条件下比比在氨氮与亚硝态氮浓度比例10:1的条件下要高35个百分点。
3. pH对于氨氮的降解有着至关重要的作用，当溶液的pH分别下降到小于8时，溶液中的NH₄ —NH₃几乎全都以不能被光催化降解的非离子态NH₄ 形式存在，在使用300w氙灯为可见光源，氨氮与亚硝态氮初始浓度比为1:1，催化剂投加量为1g/L，可见光照射的条件下，N-C-TiO₂-550℃催化剂保持pH使其自由下降到5.1时恒定所对氨氮的降解率仅仅为7%，而在相同的情况下N-Fe-TiO₂催化剂对氨氮物降解作用，反而因为亚硝态氮的转化而升高了0.07mg/L。在pH为弱碱性时，反应体系中的变化主要以氨氮被氧化为氮气为主。而当pH下降到中性或偏酸性后，体系中的变化以亚硝态氮被还原成氮气和氨氮为主。
4. 使用硅胶陶瓷环做载体的方式具备有较好的负载效果，且能抵抗一定负荷的水流冲击。但是此种负载方式对于半导体的光催化降解氨氮的能力会有影响，负载型N-C-TiO₂-550℃光催化剂对氨氮的降解率由粉末态的76%下降到了44%。

关键词：氨氮和亚硝态氮去除;改性光催化剂;共掺杂 TiO₂;催化剂负载

Load type catalyst for ammonia nitrogen and nitrate nitrogen in the aquarium degradation studies

03213744 Miao JingLing

Supervised by Wu Lei

Abstract: Aquarium industry is very important to human beings, and high ammonia nitrogen and nitrate nitrogen can lead to the growth of aquatic breeding is restricted, thus effectively degrade harmful nitrogen class is very necessary. Due to the traditional way of degradation and difficult to meet the needs of human beings, so imagine using photocatalytic oxidation is originally to the degradation of ammonia nitrogen. Various kinds of catalysts are widely used for Ti02 catalyst has many advantages and research, and there are many ways to improve the catalyst performance. The purpose of this paper is to study three two elements doped modified light catalyst under the condition of visible light irradiation, PH for aquarium fish can adapt in the range, for the ammonia nitrogen and nitrite nitrogen removal ability. Respectively were N-Fe-TiO₂,N-C-TiO₂,N-Cu-TiO₂ these three double element doped semiconductor photocatalyst modification, and experimentally explore under different preparation conditions of different kinds of modified semiconductor catalyst N-Fe-TiO₂, N-C-TiO₂-550℃, N-C-TiO₂-500℃, N-Cu-TiO₂ respectively on the degradation efficiency of ammonia nitrogen and nitrate, and may appear the phenomenon of system analysis, identify the reasons for the formation of the phenomenon. Then discuss catalyst load, and find out the right means of carrier and load, and load type catalyst for ammonia nitrogen degradation experiment, the following conclusions

(1) the selected several pairs of elements doped TiO₂ photocatalyst, semiconductor photocatalyst N-C-TiO₂-550℃, and N-Fe-TiO₂ are visible in the use of 300 w xenon lamp as light source, a constant pH of 8, catalyst dosing quantity is 1g/L, ammonia nitrogen and nitrate nitrogen initial concentration of 1mg/L, under the condition of visible light irradiation, semiconductor photocatalyst N-C-TiO₂-550 ℃ for solution of ammonia nitrogen in the degradation rate of 76%; N-Fe-TiO₂ modified semiconductor photocatalyst for the degradation of ammonia nitrogen rate is as high as 79%, indicating that the semiconductor photocatalyst N-C-TiO₂-550℃, and N-Fe -TiO₂ has significant degradation ability of ammonia nitrogen.

(2) visible in the use of 300 w xenon lamp as light source, a constant pH of 8, catalyst dosing quantity is 1 g/L, under the condition of visible light irradiation, the concentration of nitrate nitrogen can affect the degradation of ammonia nitrogen, the ammonia nitrogen and nitrate nitrogen concentration ratio 1:1, N - C - TiO2-550 ℃ for than in the degradation of ammonia nitrogen, ammonia nitrogen and nitrate nitrogen concentration ratio 10:1 under the condition of 26% above; N - Fe - TiO2 in ammonia nitrogen and nitrate concentration ratio 1:1 conditions than in ammonia nitrogen and nitrate concentration ratio of 10:1 conditions is 35% higher.

(3) the pH on the degradation of ammonia nitrogen have a vital role, when solution pH were decreased to less than 8, the solution of NH4 , NH3, nearly all to be photocatalytic degradation of non-ionic state exists in the form of NH4 , visible in the use of 300 w xenon lamp as light source, ammonia nitrogen and nitrate nitrogen initial concentration ratio of 1:1, catalyst dosing quantity is 1 g/L, under the condition of visible light irradiation, N-C-TiO2-550 ℃, maintain pH catalyst to make it free fall to 5.1 by constant of ammonia nitrogen degradation rate is only 7%, and in the same situation N-Fe-TiO2 catalyst on degradation of ammonia nitrogen, but because of the transformation of nitrate nitrogen and increased 0.07 mg/L.

(4) using silica ceramic ring carrier do the way has good load effect, and can resist impact load currents. But this way of load effects on catalyst degradation ability of the spring, the load type N-C-TiO2-550 ℃ photocatalyst for the degradation of ammonia nitrogen rate fell to 44% from 76% powder state.

Keywords: ammonia and nitrate degradation, modification of photocatalyst, Double element doped,;the catalyst loading

目录

一、 绪论 1

1.1研究背景及意义 1

1.1.1氨氮以及亚硝态氮对水生生物的毒理作用 1

1.1.2光催化技术应用于水族产业的意义 2

1.2光催化技术概述 2

1.2.1光催化的起源与发展 2

1.2.2光催化的基本原理和影响因素 3

1.2.3现阶段光催化技术的研究与应用 4

1.3国内外TiO₂的掺杂和改性的研究进展 4

1.4实验研究的技术路线 7

二、改性催化剂的筛选 8

2.1 催化剂制备方法 8

2.2 改性的方法 8

2.2.1催化剂的改性手段 9

2.3 催化剂的制备及比选 9

2.3.1三种催化剂的制备 10

2.3.2三种催化剂的筛选 10

2.4 催化剂的表征 12

2.4.1 SEM扫描电子显微镜表征分析 12

2.4.2 XRD X射线衍射分析 13

2.5 结论 14

三、光催化去除氨氮以及亚硝态氮的实验探究 15

3.1 实验材料及装置 15

3.1.1实验材料与仪器 15

3.1.2 实验装置 15

3.2 实验方法 16

3.2.1 去除实验 16

3.2.2 标准曲线绘制 16

3.3 影响因素探究 17

3.3.1 氨氮及亚硝态氮初始浓度比的影响 17

3.3.2 pH的影响 19

3.4 结果与讨论 22

四、催化剂的负载性实验探究 23

4.1 负载体的筛选 23

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