Effecient removal of various dyes from aqueous solutions by photocatalysis processes over modified titanium dioxide Nanostructures : Doctoral Thesics- Major: Chemical and Material Engineering

長庚大學化工與材料工程學系

博士論文

Department of Chemical and Materials Engineering

Chang Gung University

Doctoral Thesis

利用具奈米結構之改質二氧化鈦光催化程序以有效

去除水溶液中各種染料

Efficient Removal of Various Dyes from Aqueous

Solutions by Photocatalysis Processes over Modified

Titanium Dioxide Nanostructures

指導教授：莊瑞鑫 博士

Advisor: Ruey-Shin Juang, Ph.D.

研究生：阮志秋

Graduate Student: Nguyen Chi Hieu

中華民國 109 年 01 月

January 2020

-iii￾ACKNOWLEDGMENT

I would like to thank all the people who have helped and supported me in many respects during

the completion of this thesis.

First of all, I am heartily thankful to my supervisor Professor Ruey-Shin Juang, who is always

ready to answer any question enthusiastically and give me helpful guidance. He always encourages

and supports me in both the academic research and ordinary life. Hence, the research life in Taiwan

becomes smooth and relaxing for me. Without his guidance, this thesis would not have been

completed.

I also would like to express my sincere gratitude to all the Professors at Chemical and Materials

Department, Chang Gung University, who transmit me incomparable knowledge and great

encouragement for my future career.

My thanks go to companions at Separation Materials and Techniques Laboratory and my

friends at Chang Gung University, especially to Mr. Chun-Chieh Fu for his time and assistance

through the years of my doctoral program.

I also wish to thank Chang Gung University for providing me with a scholarship to study the

Ph.D. program. Final support of this research work from the Ministry of Sciecne and Technology,

Taiwan and the Chang Gung Medical Foundation, Taiwan is also gratefully appreciated.

My acknowledgment goes to my managers and colleagues at the Institute of Environmental

Science, Engineering and Management, Industrial University of Ho Chi Minh City, Vietnam who

facilitated me to pursue doctoral study.

Finally, I would like to dedicate my achievement and give special thanks to my beloved family,

who always encourage, support, and believe in me. It is a great comfort and relief to know that all

my decisions are always supported and this inspires me to do more.

My heartfelt thanks.

-iv￾摘要

利用光催化技術(Photocatalysis)進行有毒污染物之處理，為水及廢水淨化提供了一個

巨大的機會，以滿足不斷增長嚴重環境污染問題之處理需求。在眾多常見之非均相光觸

媒中，二氧化鈦(Titanium dioxide, TiO2)由於其高化學反應性和穩定性、無毒性和低成本，

已被證明是很有應用潛力之材料。為了進一步提高 TiO2 光觸媒對水中污染物之去除效率，

本論文嘗試以物理化學方式針對 TiO2加以改質，以克服 TiO2固有之缺點，並評估其應用

於廢水脫色(Decolorization)之潛力。通過添加貴金屬鉑(Platinum)及鈀(Palladium)、還原態

氧化石墨烯(Reduced graphene oxide, rGO)及與 ZnO 結合使用，製備出不同之 TiO2基材光

觸媒，以改進材料之光催化活性(Photocatalytic activity)。本論文對各種材料首先鑑定其物

理化學性質，包括晶體結構(Crystal structure)、形態(Morphology)、表面積(Surface area)、

帶隙(Bandgap)等之變化。材料鑑定結果證明，影響光催化活性之關鍵參數有形態、表面

積、結晶度、活性面、帶隙及電子—空洞對(Electron-hole pairs)之壽命。此外，本論文通

過批次降解去除水溶液中各種染料包括亞甲基藍(Methylene blue)，若丹明 B (Rhodamine

B)，甲基橙(Methyl orange)和萘酚藍黑(Naphthol blue black)之效率，以評估所製備材料對

染料之吸附能力及光催化活性，並與市售之 TiO2（Degussa P25）進行比較。降解實驗結

果表明，與自行製備之未改質 TiO2相比，經各種改質 TiO2之光催化活性有不同程度之提

升。此外，與 Degussa P25 相比，也有一些改質後材料具有更高之光催化活性，顯示其具

有未來實際應用之潛力

關鍵詞：去除染料；光催化程序；吸附；半導體；鈦酸鹽奈米材料；鈀金屬；鉑金屬；

還原態氧化石墨烯

-v￾ABSTRACT

Using photocatalysis to apply for water purification and treatment has provided a great

opportunity for the treatment of toxic contaminants in wastewater to meet the ever-increasing

demands of handling serious environmental pollution problems. Of many heterogeneous

photocatalysts used, titanium dioxide (TiO2) is proven to be promising owing to its high chemical

reactivity and stability, nontoxicity, and cost-effectiveness. To improve the removal efficiency

using TiO2 as an economically viable photocatalyst for wastewater treatment, the physicochemical

modifications of TiO2 were adopted in this work. Many different technical approaches were used

to modify pure TiO2 to overcome the indigenous weakness of unmodified TiO2. This thesis study

aimed to assess the potential employment of modified TiO2 photocatalyst for color removal of

wastewater. The different photocatalysts (TiO2-based materials) were prepared by various

modified routes with the addition of noble metal (Pt, Pd), reduced graphene oxide (rGO), and

combination with ZnO to improve the photoactivity of synthesized materials. The changes in

physicochemical properties (crystal structure, morphology, surface area, bandgap, etc.) of

synthesized powders were studied. Characterization experiments confirmed that the critical

parameters such as morphology, surface area, crystallinity, active facets, bandgap and the lifetime

of electron-hole pairs have the important roles for photocatalytic activity. The photocatalytic

activity of the synthesized materials was done in the liquid phase via the degradation of various

dyes (methylene blue, rhodamine B, methyl orange, and naphthol blue black), in a laboratory-scale

batch photoreactor. The photocatalytic performance of all samples was compared with that of a

commercially available TiO2 benchmark catalyst (Degussa P25). Photocatalytic performance tests

revealed improved photocatalytic activity for the modified TiO2 compared to unmodified TiO2

prepared with the same method. Also, several samples presented even higher photocatalytic

activity compared to Degussa P25, demonstrating the promising potential for practical applications.