Phthalocyanine-nanoparticle conjugates supported on inorganic nanofibers as photocatalysts for the treatment of biological and organic pollutants as well as for hydrogen generation
- Authors: Mapukata, Sivuyisiwe
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanofibers , Nanoparticles , Zinc , Hydrogen , Organic water pollutants , Water Purification , Electrospinning , Photocatalysis , Photodegradation , Anti-infective agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192831 , vital:45268 , 10.21504/10962/192831
- Description: This thesis reports on the synthesis, photophysicochemical and photocatalytic properties of various zinc phthalocyanines (Pcs). For enhanced properties and catalyst support, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. For increased catalyst surface area and catalyst reusability, the Pcs and some of their conjugates were also supported on electrospun inorganic nanofibers i.e. SiO2, hematite (abbreviated Hem and has formula α-Fe2O3), ZnO and TiO2 nanofibers. The effect that the number of charges on a Pc has on its antimicrobial activities was evaluated by comparing the photoactivities of neutral, octacationic and hexadecacationic Pcs against S. aureus, E. coli and C. albicans. The extent of enhancement of their antimicrobial activities upon conjugation (through chemisorption) to Ag NPs was also studied in solution and when supported on SiO2 nanofibers. The results showed that the hexadecacationic complex 3 possessed the best antimicrobial activity against all three microorganisms, in solution and when supported on the SiO2 nanofibers. Covalent conjugation of Pcs with carboxylic acid moieties (complexes 4-6) to amine functionalised NPs (Cys-Ag, NH2-Fe3O4 and Cys-Fe3O4@Ag) resulted in enhanced singlet oxygen generation and thus antibacterial efficiencies. Comparison of the photodegradation efficiencies of semiconductor nanofibers (hematite, ZnO and TiO2) when bare and when modified with a Pc (complex 6) were evaluated. Modification of the nanofibers with the Pc resulted in enhanced photoactivities for the nanofibers with the hematite nanofibers being the best. Modification of the hematite nanofibers with two different Pcs i.e. monosubstituted (complex 5) and an asymmetrical tetrasubstituted Pc (complex 6) showed that complex 6 better enhanced the activity of the nanofibers. Evaluation of the hydrogen generation efficiencies of the bare and modified TiO2 nanofibers calcined at different temperatures demonstrated that the anatase nanofibers calcined at 500 oC possessed the best catalytic efficiency. The efficiency of the TiO2 nanofibers was enhanced in the presence of the Co and Pd NPs as well as a Pc (complex 7), with the extent of enhancement being the greatest for the nanofibers modified with the Pd NPs. The reported findings therefore demonstrate the versatility of applications of Pcs for different water purification techniques when supported on different nanomaterials. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mapukata, Sivuyisiwe
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanofibers , Nanoparticles , Zinc , Hydrogen , Organic water pollutants , Water Purification , Electrospinning , Photocatalysis , Photodegradation , Anti-infective agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192831 , vital:45268 , 10.21504/10962/192831
- Description: This thesis reports on the synthesis, photophysicochemical and photocatalytic properties of various zinc phthalocyanines (Pcs). For enhanced properties and catalyst support, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. For increased catalyst surface area and catalyst reusability, the Pcs and some of their conjugates were also supported on electrospun inorganic nanofibers i.e. SiO2, hematite (abbreviated Hem and has formula α-Fe2O3), ZnO and TiO2 nanofibers. The effect that the number of charges on a Pc has on its antimicrobial activities was evaluated by comparing the photoactivities of neutral, octacationic and hexadecacationic Pcs against S. aureus, E. coli and C. albicans. The extent of enhancement of their antimicrobial activities upon conjugation (through chemisorption) to Ag NPs was also studied in solution and when supported on SiO2 nanofibers. The results showed that the hexadecacationic complex 3 possessed the best antimicrobial activity against all three microorganisms, in solution and when supported on the SiO2 nanofibers. Covalent conjugation of Pcs with carboxylic acid moieties (complexes 4-6) to amine functionalised NPs (Cys-Ag, NH2-Fe3O4 and Cys-Fe3O4@Ag) resulted in enhanced singlet oxygen generation and thus antibacterial efficiencies. Comparison of the photodegradation efficiencies of semiconductor nanofibers (hematite, ZnO and TiO2) when bare and when modified with a Pc (complex 6) were evaluated. Modification of the nanofibers with the Pc resulted in enhanced photoactivities for the nanofibers with the hematite nanofibers being the best. Modification of the hematite nanofibers with two different Pcs i.e. monosubstituted (complex 5) and an asymmetrical tetrasubstituted Pc (complex 6) showed that complex 6 better enhanced the activity of the nanofibers. Evaluation of the hydrogen generation efficiencies of the bare and modified TiO2 nanofibers calcined at different temperatures demonstrated that the anatase nanofibers calcined at 500 oC possessed the best catalytic efficiency. The efficiency of the TiO2 nanofibers was enhanced in the presence of the Co and Pd NPs as well as a Pc (complex 7), with the extent of enhancement being the greatest for the nanofibers modified with the Pd NPs. The reported findings therefore demonstrate the versatility of applications of Pcs for different water purification techniques when supported on different nanomaterials. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
Investigation of the levels of PBDEs and PCNs in the surface water and sediments from selected waterbodies in the Eastern Cape Province, South Africa
- Agunbiade, Idowu Victoria https://orcid.org/0000-0001-5605-0312
- Authors: Agunbiade, Idowu Victoria https://orcid.org/0000-0001-5605-0312
- Date: 2021-06
- Subjects: Persistent pollutants , Water -- Purification -- Organic compounds removal , Organic water pollutants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22699 , vital:52660
- Description: Studies have revealed that persistent organic pollutants (POPs) are omnipresent in our environment; almost all human beings have definite levels of POPs in their bodies. Even fetus and embryos are not spared; they have been found to bear certain levels of POPs. So far, there are about 28 chemicals listed as POPs among which are polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs). PCN and PBDE distributions have been reported from different sources around the world, but studies relating to PCNs occurrence and distribution in Africa, especially South Africa is still minimal. PBDEs have been reported to cause diabetes, cancer, damage to reproductive system, thyroid, liver and other vital organs in the body, while PCNs have been linked to chloracne (severe skin reactions/lesions) and liver disease (yellow atrophy) in humans, chicken oedema and X-disease in cattle. Hence, this study evaluates PCN levels in water and sediment samples from three waterbodies: North End Lake (NEL), Chatty River (CHA) and Makman Canal (MMC), while PBDE levels was reported in NEL and CHA samples. The three sites are located in Port Elizabeth, Eastern Cape Province (ECP) of South Africa. The lake serves as a recreational resort while the latter two waterbodies are tributaries discharging into the Swartkop Estuary, an important estuary in ECP. Water samples were extracted with C18 cartridges (solid phase), while soxhlet was employed for the extraction of sediments. Water and sediment extricates were purified and quantified with gas chromatography-micro electron capture detector (GC-μECD). Forty-seven (47) water samples and 44 sediment samples were collected in August until December 2020 from six sampling points in NEL, five points in each of CHA and MMC. All the samples were evaluated for physicochemical properties, PBDEs and PCNs using validated standard methods. The sampling period covered three South Africa seasons: August (winter), October (spring) and December (summer). The physicochemical parameters (PP) of NEL water samples for the three seasons generally varied as follows: temperature (15.3–23°C), pH (7.9–10.3), oxidation-reduction potential, ORP (23.4-110 mV), atmospheric pressure, AP (14.52-15.56 PSI), turbidity (15.1–167 NTU), electrical conductivity, EC (114–1291 μS/cm), total dissolved solids, TDS (55-645 mg/L), total suspended solids, TSS (20–107 mg/L) and salinity (0.05–0.65 PSU). All the PPs except for turbidity and TSS are within acceptable limits. NEL sediments had moisture content (MC), organic matter (OM) and organic carbon (OC) in the range of 0.04–8.0percent, 0.08–2.2percent and 0.05–1.8percent, respectively. The sum of eight PCN congeners Σ8PCNs and six PBDE congeners Σ6PBDEs in NEL water samples ranged from 0.164–2.934 μg/L and 0.009-1.025 μg/L individually. The values for Σ8PCNs and Σ6PBDEs in NEL sediment samples varied from 0.991–237 μg/kg and 0.354-28.850 μg/kg, respectively. The calculated hazard quotient (HQ) corresponding to the non-carcinogenic health risk associated with PBDEs in NEL water samples was 2.0×10-3-1.4×10-1, while the TEQ values due to PCNs varied from 6.10×10-7- 3.12×10-3 μg/L in NEL water samples and 3.70×10-5-1.96×10-2 μg/kg dw in sediments. The PP values for CHA water samples include temperature (15.4–22.9°C), pH (7.7–10.5), TDS (991–1771 mg/L), TSS (6–41 mg/L), turbidity (1.0–198 NTU), EC (1981–3542 μS/cm), AP (14.60–14.80 PSI), ORP (-339.1-51.3 mV), and salinity (1.02–1.87 PSU). The EC, TDS and salinity exceeded acceptable values at certain points. The sediments of CHA have MC, OM and OC contents ranging from 0.01-10.2percent, 0.2-1.3percent and 0.1-0.8percent in that order. Sum of Σ8PCNs, Σ6PBDEs in CHA water and sediment samples ranged from 0.026–1.054 μg/L, 0.007-0.079 μg/L and 0.429–1888.468 μg/kg, 0.347-6.468 μg/kg individually. The HQ in CHA water samples was 1.6×10-3-7.7×10-3 and the estimated TEQ was 1.0×10-7-6.62×10-5 μg/L and 1.10×10−5-6.40×10−2 μg/kg in water and sediments, respectively. The temperatures for MMC water samples ranged from 15.6-24.5°C, while other PPs recorded were as follows: pH (8.4-10.2), TDS (943–4002 mg/L), TSS (7-491 mg/L), turbidity (2.9-154.2 NTU), EC (1885-8004 μS/cm), AP (14.53–14.82 PSI), ORP (7.8-130 mV) and salinity (0.96-4.47 PSU). MMC’s sediments recorded MC, OM and OC varying as 0.4- 18.9percent, 0.2-4.5percent and 0.1-2.6percent, respectively across the three seasons. The Σ8PCNs for MMC water and sediment samples were 0.035–0.699 μg/L and 0.260–6744 μg/kg. The TEQ values in MMC water and sediment samples were 1.19×10-7-1.47×10-4 μg/L and 4.43×10−5- 4.19×10−1 μg/kg, respectively. The results are all less than one, and this suggests that the selected water is safe. Results showed that NEL water had highest TEQ, PCN and PBDE concentrations, while MMC sediments recorded maximum TEQ and PCN levels in this study. PBDE concentrations in NEL sediments were above the other site. In conclusion, NEL water was most polluted with both pollutants (PCNs and PBDEs), but MMC sediments contained more PCNs. There is need for the immediate remediation of these selected waterbodies. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
- Full Text:
- Date Issued: 2021-06
- Authors: Agunbiade, Idowu Victoria https://orcid.org/0000-0001-5605-0312
- Date: 2021-06
- Subjects: Persistent pollutants , Water -- Purification -- Organic compounds removal , Organic water pollutants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22699 , vital:52660
- Description: Studies have revealed that persistent organic pollutants (POPs) are omnipresent in our environment; almost all human beings have definite levels of POPs in their bodies. Even fetus and embryos are not spared; they have been found to bear certain levels of POPs. So far, there are about 28 chemicals listed as POPs among which are polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs). PCN and PBDE distributions have been reported from different sources around the world, but studies relating to PCNs occurrence and distribution in Africa, especially South Africa is still minimal. PBDEs have been reported to cause diabetes, cancer, damage to reproductive system, thyroid, liver and other vital organs in the body, while PCNs have been linked to chloracne (severe skin reactions/lesions) and liver disease (yellow atrophy) in humans, chicken oedema and X-disease in cattle. Hence, this study evaluates PCN levels in water and sediment samples from three waterbodies: North End Lake (NEL), Chatty River (CHA) and Makman Canal (MMC), while PBDE levels was reported in NEL and CHA samples. The three sites are located in Port Elizabeth, Eastern Cape Province (ECP) of South Africa. The lake serves as a recreational resort while the latter two waterbodies are tributaries discharging into the Swartkop Estuary, an important estuary in ECP. Water samples were extracted with C18 cartridges (solid phase), while soxhlet was employed for the extraction of sediments. Water and sediment extricates were purified and quantified with gas chromatography-micro electron capture detector (GC-μECD). Forty-seven (47) water samples and 44 sediment samples were collected in August until December 2020 from six sampling points in NEL, five points in each of CHA and MMC. All the samples were evaluated for physicochemical properties, PBDEs and PCNs using validated standard methods. The sampling period covered three South Africa seasons: August (winter), October (spring) and December (summer). The physicochemical parameters (PP) of NEL water samples for the three seasons generally varied as follows: temperature (15.3–23°C), pH (7.9–10.3), oxidation-reduction potential, ORP (23.4-110 mV), atmospheric pressure, AP (14.52-15.56 PSI), turbidity (15.1–167 NTU), electrical conductivity, EC (114–1291 μS/cm), total dissolved solids, TDS (55-645 mg/L), total suspended solids, TSS (20–107 mg/L) and salinity (0.05–0.65 PSU). All the PPs except for turbidity and TSS are within acceptable limits. NEL sediments had moisture content (MC), organic matter (OM) and organic carbon (OC) in the range of 0.04–8.0percent, 0.08–2.2percent and 0.05–1.8percent, respectively. The sum of eight PCN congeners Σ8PCNs and six PBDE congeners Σ6PBDEs in NEL water samples ranged from 0.164–2.934 μg/L and 0.009-1.025 μg/L individually. The values for Σ8PCNs and Σ6PBDEs in NEL sediment samples varied from 0.991–237 μg/kg and 0.354-28.850 μg/kg, respectively. The calculated hazard quotient (HQ) corresponding to the non-carcinogenic health risk associated with PBDEs in NEL water samples was 2.0×10-3-1.4×10-1, while the TEQ values due to PCNs varied from 6.10×10-7- 3.12×10-3 μg/L in NEL water samples and 3.70×10-5-1.96×10-2 μg/kg dw in sediments. The PP values for CHA water samples include temperature (15.4–22.9°C), pH (7.7–10.5), TDS (991–1771 mg/L), TSS (6–41 mg/L), turbidity (1.0–198 NTU), EC (1981–3542 μS/cm), AP (14.60–14.80 PSI), ORP (-339.1-51.3 mV), and salinity (1.02–1.87 PSU). The EC, TDS and salinity exceeded acceptable values at certain points. The sediments of CHA have MC, OM and OC contents ranging from 0.01-10.2percent, 0.2-1.3percent and 0.1-0.8percent in that order. Sum of Σ8PCNs, Σ6PBDEs in CHA water and sediment samples ranged from 0.026–1.054 μg/L, 0.007-0.079 μg/L and 0.429–1888.468 μg/kg, 0.347-6.468 μg/kg individually. The HQ in CHA water samples was 1.6×10-3-7.7×10-3 and the estimated TEQ was 1.0×10-7-6.62×10-5 μg/L and 1.10×10−5-6.40×10−2 μg/kg in water and sediments, respectively. The temperatures for MMC water samples ranged from 15.6-24.5°C, while other PPs recorded were as follows: pH (8.4-10.2), TDS (943–4002 mg/L), TSS (7-491 mg/L), turbidity (2.9-154.2 NTU), EC (1885-8004 μS/cm), AP (14.53–14.82 PSI), ORP (7.8-130 mV) and salinity (0.96-4.47 PSU). MMC’s sediments recorded MC, OM and OC varying as 0.4- 18.9percent, 0.2-4.5percent and 0.1-2.6percent, respectively across the three seasons. The Σ8PCNs for MMC water and sediment samples were 0.035–0.699 μg/L and 0.260–6744 μg/kg. The TEQ values in MMC water and sediment samples were 1.19×10-7-1.47×10-4 μg/L and 4.43×10−5- 4.19×10−1 μg/kg, respectively. The results are all less than one, and this suggests that the selected water is safe. Results showed that NEL water had highest TEQ, PCN and PBDE concentrations, while MMC sediments recorded maximum TEQ and PCN levels in this study. PBDE concentrations in NEL sediments were above the other site. In conclusion, NEL water was most polluted with both pollutants (PCNs and PBDEs), but MMC sediments contained more PCNs. There is need for the immediate remediation of these selected waterbodies. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
- Full Text:
- Date Issued: 2021-06
- «
- ‹
- 1
- ›
- »