Evaluation of functionalized silver and silica nanoparticles for the removal of deoxyribonucleic acid conveying antibiotics resistance genes from water
- Authors: Ezeuko, Adaora Stella
- Date: 2022
- Subjects: DNA , Silica , Water
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27765 , vital:69414
- Description: Antibiotic resistance genes ARGs are recognized as a serious public health emergency linked to extensive use of antibiotics by humans and animals as a prophylactic agent that treats and prevents infections. The occurrence of high concentrations being identified in wastewater treatment plants, rivers, etc is due to untreated effluents being discharged from households, hospitals, agriculture, and pharmaceutical industries. The application of adequate treatment techniques and material for the removal of bacteria DNA conveying ARGs from the effluents before their release to the environment cannot be overemphasized. Adsorption techniques seem to be effective due to their easy design, operation, and ability to regenerate adsorbents for use without producing toxic by-products. This concept was employed for the removal of bacteria DNA conveying ARGs from simulated aqueous solution, effluents from hospital, river and WWTPs using silver and silica metallic nanoparticles. This thesis investigated the effectiveness of metallic nanoparticles containing silver AgNPs and mesoporous silica nanoparticles MSNPs as well as magnetite Fe3O4 functionalized with 4 4hydroxyphenyl 2 262-terpyridine onto their surface, for the removal of bacteria DNA conveying antibiotic resistance genes from water samples from hospitals, river, and wastewater treatment plants WWTPs. Silver nanoparticles AgNPs of different molar concentrations 0.1M, 0.5M and 1.0 M and mesoporous silica nanoparticles MSNPs adsorbents were successfully synthesized in their original states and surface functionalization achieved by incorporating magnetite Fe3O4 and 4 4 hydroxyphenyl 2 2 6 2 terpyridine on the silver AgNPs Fe3O4 and silica MSNPs TPPY surfaces respectively. Their effectiveness as adsorbent for the removal of bacteria DNA conveying ARGs from aqueous solutions and real water/wastewater samples were investigated. The DNA uptake by the as-synthesized AgNPs and MSNPs were compared to the functionalized AgNPs Fe3O4 and MSNPsTPPY by determining the adsorbents with the highest removal efficiencies. All as synthesized and functionalized adsorbents were characterized by SEM, EDX, FTIR, XRD, UV spectroscopy and PZC before the removal process. The extraction of genomic DNA from antibiotic-resistant Enterococcus faecium and Vibrio parahaemolyticus was successfully achieved via the boiling method. Antibiotic susceptibility test was conducted using the disk diffusion method before the commencement of genomic DNA extraction. Molecular characterization via gel electrophoresis confirmed the presence of resistance genes at different base pairs. Adsorption batch experiment were investigated, and the best optimum parameters were evaluated through the influence of pH, contact time, initial DNA concentration, adsorbent dose, and competitive ions for each sorption process. The rate determining step were determined by fitting kinetic models such as Natarajan and Khalaf first order, pseudo first order, pseudo second order, Elovich model to experimental data. Also, the adsorption mechanisms determining adsorption equilibrium were investigated by fitting Freundlich, Langmuir and Sips model into the experimental data. The application of AgNPsFe3O4 nanocomposite and MSNPsTPPY for the removal of bacteria DNA demonstrated much enhancement for DNA uptake than the as-synthesized AgNPs and MSNPs materials. The incorporation of magnetite and 4 4hydroxyphenyl 2 2 6 2-terpyridine onto AgNPs and MSNPs significantly enhanced the binding affinity towards the removal the bacteria DNA via strong electrostatic attraction between the active sites on the adsorbent and the negative DNA molecules. Finally, high adsorption capacities were recorded with AgNPsFe3O4 nanocomposite and MSNPsTPPY compared to AgNPs and MSNPs with chaotropic salts. The kinetic adsorption models were mostly best fitted by the pseudo-second order and Elovich models while the adsorption equilibrium was best described by Langmuir and Sips isotherm models. MSNPs with different chaotropic salts, AgNPsFe3O4 nanocomposite and MSNPsTPPY also proved its effectiveness in DNA removal not only in the simulated aqueous solution but in three different real life water samples obtained from Cofimvaba hospital, Ndevana river and Uitenhage WWTPs. High adsorption efficiencies above 90 percent were achieved during the removal of DNA in all the three real water samples. Therefore, application of these adsorbents for the removal of bacteria DNA conveying ARGs may be a promising option that would tackle the consequences of consuming ARGs infected water globally. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Authors: Ezeuko, Adaora Stella
- Date: 2022
- Subjects: DNA , Silica , Water
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27765 , vital:69414
- Description: Antibiotic resistance genes ARGs are recognized as a serious public health emergency linked to extensive use of antibiotics by humans and animals as a prophylactic agent that treats and prevents infections. The occurrence of high concentrations being identified in wastewater treatment plants, rivers, etc is due to untreated effluents being discharged from households, hospitals, agriculture, and pharmaceutical industries. The application of adequate treatment techniques and material for the removal of bacteria DNA conveying ARGs from the effluents before their release to the environment cannot be overemphasized. Adsorption techniques seem to be effective due to their easy design, operation, and ability to regenerate adsorbents for use without producing toxic by-products. This concept was employed for the removal of bacteria DNA conveying ARGs from simulated aqueous solution, effluents from hospital, river and WWTPs using silver and silica metallic nanoparticles. This thesis investigated the effectiveness of metallic nanoparticles containing silver AgNPs and mesoporous silica nanoparticles MSNPs as well as magnetite Fe3O4 functionalized with 4 4hydroxyphenyl 2 262-terpyridine onto their surface, for the removal of bacteria DNA conveying antibiotic resistance genes from water samples from hospitals, river, and wastewater treatment plants WWTPs. Silver nanoparticles AgNPs of different molar concentrations 0.1M, 0.5M and 1.0 M and mesoporous silica nanoparticles MSNPs adsorbents were successfully synthesized in their original states and surface functionalization achieved by incorporating magnetite Fe3O4 and 4 4 hydroxyphenyl 2 2 6 2 terpyridine on the silver AgNPs Fe3O4 and silica MSNPs TPPY surfaces respectively. Their effectiveness as adsorbent for the removal of bacteria DNA conveying ARGs from aqueous solutions and real water/wastewater samples were investigated. The DNA uptake by the as-synthesized AgNPs and MSNPs were compared to the functionalized AgNPs Fe3O4 and MSNPsTPPY by determining the adsorbents with the highest removal efficiencies. All as synthesized and functionalized adsorbents were characterized by SEM, EDX, FTIR, XRD, UV spectroscopy and PZC before the removal process. The extraction of genomic DNA from antibiotic-resistant Enterococcus faecium and Vibrio parahaemolyticus was successfully achieved via the boiling method. Antibiotic susceptibility test was conducted using the disk diffusion method before the commencement of genomic DNA extraction. Molecular characterization via gel electrophoresis confirmed the presence of resistance genes at different base pairs. Adsorption batch experiment were investigated, and the best optimum parameters were evaluated through the influence of pH, contact time, initial DNA concentration, adsorbent dose, and competitive ions for each sorption process. The rate determining step were determined by fitting kinetic models such as Natarajan and Khalaf first order, pseudo first order, pseudo second order, Elovich model to experimental data. Also, the adsorption mechanisms determining adsorption equilibrium were investigated by fitting Freundlich, Langmuir and Sips model into the experimental data. The application of AgNPsFe3O4 nanocomposite and MSNPsTPPY for the removal of bacteria DNA demonstrated much enhancement for DNA uptake than the as-synthesized AgNPs and MSNPs materials. The incorporation of magnetite and 4 4hydroxyphenyl 2 2 6 2-terpyridine onto AgNPs and MSNPs significantly enhanced the binding affinity towards the removal the bacteria DNA via strong electrostatic attraction between the active sites on the adsorbent and the negative DNA molecules. Finally, high adsorption capacities were recorded with AgNPsFe3O4 nanocomposite and MSNPsTPPY compared to AgNPs and MSNPs with chaotropic salts. The kinetic adsorption models were mostly best fitted by the pseudo-second order and Elovich models while the adsorption equilibrium was best described by Langmuir and Sips isotherm models. MSNPs with different chaotropic salts, AgNPsFe3O4 nanocomposite and MSNPsTPPY also proved its effectiveness in DNA removal not only in the simulated aqueous solution but in three different real life water samples obtained from Cofimvaba hospital, Ndevana river and Uitenhage WWTPs. High adsorption efficiencies above 90 percent were achieved during the removal of DNA in all the three real water samples. Therefore, application of these adsorbents for the removal of bacteria DNA conveying ARGs may be a promising option that would tackle the consequences of consuming ARGs infected water globally. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
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Development of a visible light active, photo-catalytic and antimicrobial nanocomposite of titanium dioxide and silicon dioxide for water treatment
- Authors: Mungondori, Henry Heroe
- Date: 2012
- Subjects: Titanium dioxide , Silica , Catalysis , Nanocomposites (Materials) , Water -- Purification
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11335 , http://hdl.handle.net/10353/471 , Titanium dioxide , Silica , Catalysis , Nanocomposites (Materials) , Water -- Purification
- Description: The aim of this study was to prepare composite materials based on titanium dioxide (TiO2) and silicon dioxide (SiO2), and to evaluate their photo-catalytic and antimicrobial properties. Carbon and nitrogen doped TiO2nano-particles were prepared via a sol gel synthesis, which is a simple hydrolysis and condensation technique. In situ doping was carried out using glucose and urea as carbon and nitrogen sources respectively. Doping increased the spectral response of titanium dioxide photo-catalyst, allowing it to utilise the visible region which is much wider than the UV region (about 40 % of the solar spectrum), thus making it a more efficient photo-catalyst. The carbon and nitrogen doped TiO2-SiO2nano-particles were immobilized on glass support material to allow for easy separation of the spent photo-catalyst after the photo-degradation process. Tetraethyl orthosilicate (TEOS) was employed as both a binder and precursor for silicon dioxide. A mixture of TiO2 and TEOS in a 1:1 ratio was allowed to polymerize on a glass support which had been treated with hydrofluoric acid to introduce OH groups. The prepared photo-catalytic material was characterized by FT-IR, XRD, DRS, TEM, EDX, and BET analyses. Carbon was found to be more effective as a dopant than nitrogen. It brought about a band gap reduction of 0.30 eV and a BET surface area of 95.4 m2g-1 on the photo-catalyst as compared to a gap reduction of 0.2 eV and surface area of 52.2 m2g-1 for nitrogen doped TiO2. On the other hand, introduction of SiO2 allowed utilization of visible light by the TiO2-SiO2 nano-composite leading to an improved rate of photo-degradation of both methyl orange and phenol red. However, the immobilization of TiO2 on support material made it less effective towards inactivation of E. coli ATCC 25922 bacterial cells when compared to powdered TiO2 which was able to inactivate about 98 % of the bacterial cells within an hour of treatment.
- Full Text:
- Authors: Mungondori, Henry Heroe
- Date: 2012
- Subjects: Titanium dioxide , Silica , Catalysis , Nanocomposites (Materials) , Water -- Purification
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11335 , http://hdl.handle.net/10353/471 , Titanium dioxide , Silica , Catalysis , Nanocomposites (Materials) , Water -- Purification
- Description: The aim of this study was to prepare composite materials based on titanium dioxide (TiO2) and silicon dioxide (SiO2), and to evaluate their photo-catalytic and antimicrobial properties. Carbon and nitrogen doped TiO2nano-particles were prepared via a sol gel synthesis, which is a simple hydrolysis and condensation technique. In situ doping was carried out using glucose and urea as carbon and nitrogen sources respectively. Doping increased the spectral response of titanium dioxide photo-catalyst, allowing it to utilise the visible region which is much wider than the UV region (about 40 % of the solar spectrum), thus making it a more efficient photo-catalyst. The carbon and nitrogen doped TiO2-SiO2nano-particles were immobilized on glass support material to allow for easy separation of the spent photo-catalyst after the photo-degradation process. Tetraethyl orthosilicate (TEOS) was employed as both a binder and precursor for silicon dioxide. A mixture of TiO2 and TEOS in a 1:1 ratio was allowed to polymerize on a glass support which had been treated with hydrofluoric acid to introduce OH groups. The prepared photo-catalytic material was characterized by FT-IR, XRD, DRS, TEM, EDX, and BET analyses. Carbon was found to be more effective as a dopant than nitrogen. It brought about a band gap reduction of 0.30 eV and a BET surface area of 95.4 m2g-1 on the photo-catalyst as compared to a gap reduction of 0.2 eV and surface area of 52.2 m2g-1 for nitrogen doped TiO2. On the other hand, introduction of SiO2 allowed utilization of visible light by the TiO2-SiO2 nano-composite leading to an improved rate of photo-degradation of both methyl orange and phenol red. However, the immobilization of TiO2 on support material made it less effective towards inactivation of E. coli ATCC 25922 bacterial cells when compared to powdered TiO2 which was able to inactivate about 98 % of the bacterial cells within an hour of treatment.
- Full Text:
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