Production of nanoparticles using cocoa waste /
Currently, a large number of physical, chemical, and biological methods are available to synthesize different types of nanoparticles (NPs) such as metals, semiconductors, and magnetic materials. While most of the synthetic physicochemical methods reported to date are heavily dependent on the use of...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kulliyyah of Engineering, International Islamic University Malaysia,
2017
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | Currently, a large number of physical, chemical, and biological methods are available to synthesize different types of nanoparticles (NPs) such as metals, semiconductors, and magnetic materials. While most of the synthetic physicochemical methods reported to date are heavily dependent on the use of organic solvents and toxic reducing agents, green synthesis of NPs provides advancements over other methods as it is simple, cost-effective, and relatively reproducible and often results in more stable materials. Cocoa pod husk (CPH) is a by-product obtained after removal of cocoa beans from cocoa fruit which causes many environmental problems. The analysis of CPH has shown that this waste material contains phytochemicals such as polyphenols and theobromines as well as high amounts of protein and sugar which can act as reducing agent in the green synthesis of NPs. In this study, aqueous extract and broth of cocoa waste (cocoa pod husk and leaf) were screened for their potential reduction of five salt precursors including copper (II) chloride, cerium (III) nitrate, cadmium sulfate, silver nitrate and iron (III) chloride into their relative nanoparticles (NPs) in a novel, eco-friendly and one step protocol. Formation of NPs by CPH extract was followed by the observation of distinguished colour change of the related NPs in the reaction mixture. The synthesis of CPH extract mediated selenium nanoparticles (Se NPs) was identified by change in the colour of the reaction mixture into bright red colour, while the other metal salt solutions did not present any colour changes expected for their respective metal NPs formation. UV-vis spectroscopy further confirmed the formation of Se NPs. Since the required contact time for the synthesis of Se NPs was relatively long, initial studies were carried out to improve the reaction condition. The addition of 8 ml CPH extract (50% w/v) to 42 ml sodium selenite (1 mM) at 30 °C while vigorously mixing by magnetic stirrer exhibited the distinguished light red colour change of the reaction solution within 48 hours indicating formation of Se NPs. A systematic study of the significant factors involved in the production of Se NPs was performed by fractional factorial design at two levels. Sodium selenite and CPH extract concentration as well as mixing time were identified as significant which were optimized by response surface method. It was concluded that maintaining the mixing time at 5.3 days and CPH extract concentration at 36.5% w/v as well as the use of 30 mM sodium selenite maximized the Se NPs concentration. Characterization of Se NPs by field emission scanning electron microscopy (FESEM) determined the spherical shape of the Se NPs with the size range from 25-45 nm. The Fourier transformation infra-red (FTIR) spectroscopy demonstrated two main peaks in both control sample (CPH extract) and the produced Se NPs corresponding to N-H and O-H groups. This was interpreted as the contribution of the proteins and polysaccharides available in the CPH extract in the reduction of the selenite ions (SeO32-). |
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| Physical Description: | xv, 151 leaves : illustrations ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 125-145) |