Development of Solar-Active Photocatalytic Composites for the Degradation of Phrarmaceuticals in Water
| dc.contributor.author | Alfred, Moses Oladele | |
| dc.date.accessioned | 2022-03-02T10:47:38Z | |
| dc.date.available | 2022-03-02T10:47:38Z | |
| dc.date.issued | 2021 | |
| dc.description.abstract | Pharmaceutical chemicals belong to a group of water contaminants of emerging concerns known as emerging contaminants and their presence in water leads to aquatic toxicity, antibiotic resistance development in pathogenic bacteria to mention but few. Although there are some techniques available for their removal in water, yet they are either too expensive to maintain, quite slow and ineffective at some elevated concentration or produce toxic by-products into treated water. Photocatalysis is a promising technique for water treatment due to its low mass transfer limitation, chemical stability, rapid dynamics of mineralization of organic pollutants and efficient operation at ambient temperature. This study reports the synthesis of solar-active composites from combination of waste biomass namely Carica papaya seeds and Musa paradisiaca peels and abundant clay for the purpose of removing Acetaminophen (ACT), Ampicillin (AMP), Arthemether (ART) and Sulfamethoxazole (SMX) in water. The composites were prepared in two forms: TiO2-modified and metal-doped photoactive composites with tungstate and kaolinite being common to them. The X-ray diffraction (XRD) patterns of these composites indicate the presence of semiconductors: ZnWO4, CuWO4, FeWO4 and TiO2, which are responsible for their photocatalytic activity. Photoluminescence and Electron Paramagnetic Resonance (EPR) spectroscopic techniques suggest the presence of defect states in these composites induced by the presence of carbon and kaolinite. Evaluating the photocatalytic activity of TiO2-modifed composites on the pharmaceutical chemicals under sunlight, suggests that TiO2@ZnWO4 composite possesses the best efficiency that allows photodegradation to be complete in 30 min with mineralization of 80% and ~50% for AMP and SMX respectively. However, the metal-doped composites gave better photodegradation efficiency with Cu@ZnWO4 being the best with an efficiency of 100% and 68% for AMP and SMX molecules respectively. Photo-mineralization was however ≤ 45% for both pharmaceutical molecules. The photocatalytic reaction releases inorganic by-products (〖SO〗_4^(2-), 〖NO〗_3^- and 〖NH〗_4^+) at levels below WHO permissible limits for drinking water. Generally, changing the concentrations of electrolyte did not influence the efficiency of both types of composites except for Cu@ZnWO4 with an increment in efficiency of SMX molecules. This suggests that adsorption may not precede photocatalysis, contrary to common models. A small loss in efficiency (~6%) was observed with both type of composites when they were reused for the removal of AMP molecules over 5 cycles while there was consistent loss of efficiency of Cu@ZnWO4 when it is reused for the removal of SMX molecules from water for same number of reuse cycles. From EPR studies, it was concluded that surface oxygen vacancies and defects in the crystal lattices of these composites are the main driving forces characterizing their improved photocatalytic activity. These composites were found efficient for the removal of AMP and SMX molecules from more complex water matrices like raw wastewater from an abattoir, a river, and a hand-dug well for drinking water. This highlights the potential of the composites to effectively treat drinking water, which could find applications in the development of point-of-use water treatment devices. | en_US |
| dc.description.sponsorship | African-German Network of Excellence in Sciences, TWAS-CNPq | en_US |
| dc.identifier.uri | http://dspace.run.edu.ng:8080/jspui/handle/123456789/1723 | |
| dc.language.iso | en | en_US |
| dc.title | Development of Solar-Active Photocatalytic Composites for the Degradation of Phrarmaceuticals in Water | en_US |
| dc.type | Thesis | en_US |