Plasmon catalyst dispersed on carbonised pinecone for enhanced degradation of organic contaminants

dc.contributor.authorOlalekan, Sanni Saheed
dc.contributor.co-promoterViljoen, Elvera, Dr.
dc.contributor.promoterOfomaja, Augustine, Prof.
dc.date.accessioned2022-12-12T02:29:47Z
dc.date.available2022-12-12T02:29:47Z
dc.date.issued2020-11
dc.descriptionPh. D. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology.en_US
dc.description.abstractAromatic organic contaminants are difficult to biodegrade, and thus effective green technologies are required to remove these pollutants from the ecosystem. Tetracycline antibiotic, an organic water pollutant, can be degraded by heterogeneous photocatalysis using an appropriate catalyst, with capability in converting the visible light energy into active species. The thesis focused on silver nanoparticles anchored on silver bromide (Ag/AgBr) as a plasmonic catalyst dispersed on activated carbon (ACK), were used as a photocatalyst (AABR-ACK) in tetracycline removal. The aim is to develop a catalyst that is active in low intensity visible light, whilst the addition of activated carbon will increase the light absorption and separate the charge pairs, after the photocatalyst has been excited by the visible light. The activated carbons were derived from pinecone pyrolyzed in a microwave. The pinecone mass to potassium hydroxide impregnation ratio and microwave pyrolysis time influenced the activated carbon properties. An impregnation ratio of 2.24 and microwave pyrolysis time of 16 minutes at constant microwave power of 400 W yielded the activated carbon with the best-developed porous structure and electrochemical properties. This activated carbon was used during the optimisation of the Ag/AgBr activated carbon (AABR-ACK) catalysts preparation using a thermal polyol precipitation method and response surface methodology. The most active catalyst was the AABR-ACK 11 obtained by a preparation temperature of 140 ºC, time (17.50 minutes), mass of surfactant and activated carbon (0.26 g and 0.03 g) respectively. This catalyst had an ordered nanospheres morphology, reduced electron-hole recombination rate, better electrochemical properties and exhibited enhanced activity on the tetracycline antibiotic removal in comparison to other Ag/AgBr activated carbon catalysts. A percentage degradation of 92% was obtained in 180 minutes were obtained with the AABR-ACK 11 catalyst. The photocatalyst prepared using the best activated carbon derived from pinecone developed in this study was compared to photocatalysts prepared using commercial activated carbon and biochar. The Ag/AgBr activated carbon catalysts using pinecone-derived activated carbon degraded the tetracycline to 92%, which is significantly higher than the percentage degradations (80% and 74%) for the catalyst prepared using commercial activated carbon and biochar catalysts respectively. The higher activity of the Ag/AgBr activated carbon catalysts using pinecone-derived activated carbon was due to the conductive attributes of the catalyst support for accelerated transfer of photo-induced electrons. The Ag/AgBr activated carbon catalysts using pinecone- derived activated carbon also exhibited better performance on tetracycline removal when compared to photocatalysts reported in literature. Two catalyst preparation methods, thermal polyol and deposition precipitation, were compared. The thermal polyol method yielded a more active catalyst for the degradation of the tetracycline in comparison to the deposition precipitation method. The degradation reaction conditions such as pH, light intensity and degradation temperature influenced the rate of the reaction. The highest rate of degradation was obtained at a pH of seven, white light and 40 ºC temperature. The intermediate products formed because of hydroxylation, deamination, demethylation and dehydration during the photocatalytic degradation of tetracycline antibiotics were identified using liquid chromatography mass spectrometer. Quenching experiments with hydroxyl, hole, and superoxide anion species showed that the most important radical responsible for the tetracycline degradation was the superoxide anion radical.en_US
dc.identifier.urihttp://hdl.handle.net/10352/575
dc.language.isoenen_US
dc.publisherVaal University of Technologyen_US
dc.subjectPlasmon catalysten_US
dc.subjectDegradation of organic contaminantsen_US
dc.subjectCarbonised pineconeen_US
dc.subjectGreen technologiesen_US
dc.subjectSilver nanoparticlesen_US
dc.subjectPhotocatalysten_US
dc.subjectPhotocatalytic degradationen_US
dc.subjectTetracycline antibioticsen_US
dc.subjectVisible-light photocatalyticen_US
dc.subjectWater contaminationen_US
dc.subject.lcshDissertations, Academic -- South Africa.en_US
dc.subject.lcshNanoparticles.en_US
dc.subject.lcshSilver.en_US
dc.subject.lcshCatalysts.en_US
dc.subject.lcshOrganic water pollutants.en_US
dc.titlePlasmon catalyst dispersed on carbonised pinecone for enhanced degradation of organic contaminantsen_US
dc.typeThesisen_US
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