1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Title:	Synthesis and characterization of ZnO and its doped nanoparticles via sol-gel method for photocatalytic degradation of environmental pollutants under direct solar radiation
Authors:	Muneer Mohammed Awadh Baabbad (P45934)
Supervisor:	Abdul Amir H. Kadhum, Prof. Dr.
Keywords:	Environmental pollutants Environmental toxicology
Issue Date:	24-Apr-2014
Description:	Nanopartikel ZnO (ZnO NP) dicirikan sebagai pemangkin-cahaya yang baik dalam proses penulenan sebatian organik bertoksik disebabkan oleh optiknya dan ciri-ciri kimia yang baik serta menjimatkan. Hasil kajian awal menunjukkan agen penutup atau surfaktan digunakan untuk mengawal saiz nanopartikel semikonduktor. Kebanyakan agen penutup mengandungi bahan kimia bertoksik yang sukar untuk disingkirkan daripada permukaan nanopartikel yang disintesis dan ia juga meningkatkan kos bagi pengeluaran skala naik. Justeru itu, kajian ini adalah bertujuan untuk mensintesis ZnO NP menggunakan kaedah sol-gel tanpa menggunakan agen penutup atau surfaktan untuk mengawal saiz zarah. Kajian kesan parameter proses iaitu nisbah molar, pH dan suhu pengkalsinan terhadap sintesis dan pencirian ZnO NP turut dijalankan. Pengoptimuman parameter proses untuk sintesis ZnO NP telah dijalankan menggunakan kaedah sambutan permukaan (RSM). Bagi meningkatkan ciri-ciri ZnO NP, pengedopan dengan ion logam peralihan seperti besi (Fe3+), titanium (Ti4+) dan samarium (Sm3+) telah dijalankan. Seterusnya, aktiviti ZnO dan ZnO NP yang didop dianalisis untuk penguraian foto sebatian fenol berpoliklorin. Akhirnya, mekanisme dan kajian ketoksikan penguraian sebatian fenol berpoliklorin sebelum dan selepas penguraian telah ditentukan. ZnO NP dan pemangkinnya yang didop telah disintesis menggunakan kaedah sol-gel, yang mana larutan sol-gel yang mengandungi zink asetat dan asid oksalik dengan nisbah molar yang berbeza ditambah dalam etanol dengan pH air yang pelbagai. Gel ZnO dan ZnO NP yang didop kemudian dikeringkan dan dikalsinkan pada suhu 400, 500 dan 600 °C dan dicirikan menggunakan teknik ukuran yang berbeza. Reaktor berjujukan silinder dengan pengadukan yang berterusan telah digunakan untuk mengkaji penguraian foto sebatian fenol berpoliklorin di bawah sinaran matahari secara langsung. Bagi kajian penguraian foto, kaedah faktorial dua peringkat dan RSM telah digunakan untuk mengoptimumkan lima parameter proses termasuk suapan organik, pH, suhu pengkalsinan, kepekatan dan keamatan sinaran. Kecekapan penguraian dan mekanisme telah dianalisis dengan HPLC dan GC-MS, manakala ketoksikan telah diuji menggunakan bakteria Escherichia-coli dengan kaedah zon perencatan. Keadaan optimum kajian pada nisbah molar 1.76, pH 1.50 dan suhu pengkalsinan 402.2 °C menghasilkan ZnO NP bersaiz 18±2 nm berbanding 22.9 nm dari model. Kajian kesan parameter proses terhadap morfologi dan sifat optik ZnO NP menunjukkan saiz ZnO NP meningkat dan pengumpulan yang lebih besar terhasil apabila nisbah molar, pH dan suhu pengkalsinan adalah di antara keadaan optimum. Luas permukaan dan sifat-sifat optik telah meningkat dengan menggunakan proses pengedopan mangkin. Kepekatan optimum untuk bahan dop adalah pada 0.5% berat bagi Fe+3 dan Sm+3 manakala 0.25% berat bagi Ti+4. Keadaan optimum untuk penguraian foto telah ditemui pada pH 6.09, suhu pengkalsinan 411.50 °C dan keamatan sinaran 23 W/m2 dengan kecekapan sebanyak 99.54 % yang menghampiri dengan nilai 97.80 % daripada model teori. Sebatian perantaraan yang dihasilkan daripada penguraian poliklorofenol adalah tidak toksik seperti yang didapati melalui ujian ketoksikan.,ZnO nanoparticles (ZnO NP) have been found to be excellent materials for photocatalysis process in the environmental purification of toxic organic pollutants due to its good optical and chemical properties as well as its low cost. Many earlier studies have made use the capping agent or a surfactant to control the size of the semiconductor nanoparticles. Most of the capping agent comprise of toxic chemicals, which are difficult to be removed from the surface of the synthesized nanoparticles apart from contaminating the environment and add cost for scale up production. Hence, this research aimed to synthesize the ZnO NP using sol-gel method without using capping agent or surfactant to control the particle size. In addition, the effects of process parameters, namely, molar ratio, pH and calcination temperatures on the synthesis and the characterizations of ZnO NP have also been investigated. The optimization of process parameters for synthesis of ZnO NP was performed using Response Surface Methodology technique (RSM). In order to improve the properties of ZnO NP, doping with transition metal ions using iron (Fe3+), titanium (Ti4+) and samarium (Sm3+) were also carried out. The activity of both, ZnO and its doped NP, was then examined for the photodegradation of polychlorinated phenol. Finally, the mechanism and toxicity of polychlorinated phenol degradation before and after degradation were determined. ZnO NP and its doped catalysts were synthesized using sol-gel method, in which gel solutions containing zinc acetate and oxalic acid with different molar ratios were added in ethanol with water using various selected pHs. The ZnO gel and doped ZnO NP were dried and calcined at different temperatures of 400, 500 and 600 °C, then characterized using selected instrumental measurements. A cylinder batch reactor with continuous stirring was used to investigate for photodegradation of polychlorinated phenol under direct solar radiation energy. For the photodegradation experiments, 2-level factorial and RSM were selected for conducting the survey and optimization. Five parameters, namely, loading, pH, calcination temperature, concentration and solar intensity were investigated in this study. The degradation efficiency and mechanism were evaluated using HPLC and GC-MS, whereas the toxicity was tested using Escherichia coli bacteria with inhibition zone method. The experimental optimum condition of molar ratio of 1.76, pH of 1.50 and calcination at 402.2 °C produced ZnO NP with particle size of 18±2 nm compared with 22.9 nm from model. The study on the effects of process parameters on the morphological and optical properties of ZnO NP showed increased in size of ZnO NP and formation of larger agglomeration when the molar ratio, pH and calcination temperature were in within the optimal condition. The surface area and optical properties were found to be improved by doping the catalyst. The optimal concentration for dopant was found at 0.5 wt. % for Fe+3 and Sm+3, and 0.25 wt. % for Ti+4. The optimal condition for photodegradation was found at pH of 6.09, calcination temperature of 411.50 °C with solar intensity of 23 W/m2 with the efficiency of 97.80 % which was in close agreement with the experimental of 99.54 %. The comparison between the activity of ZnO and its doped NP for photodegradation showed that the efficiency increased up to one and a half times for doped compared to undoped ZnO NP under the same experimental conditions. The intermediate compound produced from degradation of polychlorophenols was nontoxic as shown via the toxicity study.,PhD
Pages:	284
Call Number:	T174.7.B334 2014 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.