Removal and photocatalysis of 4-Nitrophenol using metallophthalocyanines
- Authors: Marais, Eloïse Ann
- Date: 2008
- Subjects: Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4343 , http://hdl.handle.net/10962/d1005005 , Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Description: Photodegradation of 4-nitrophenol (4-Np) in the presence of water-soluble zinc phthalocyanines and water-insoluble metallophthalocyanines is reported. The water-soluble phthalocyanines employed include zinc tetrasulphophthalocyanine (ZnPcS[subscript 4]), zinc octacarboxyphthalocyanine (ZnPc(COOH)[subscript 8]) and a sulphonated ZnPc containing a mixture of differently sulphonated derivatives (ZnPcS[subscript mix]), while the water-insoluble phthalocyanines used include unsubstituted magnesium (MgPc), zinc (ZnPc) and chloroaluminium (ClAlPc) phthalocyanine complexes and the ring-substituted zinc tetranitro (ZnPc(NO[subscript 2])[subscript 4]), zinc tetraamino (ZnPc(NH[subscript 2])[subscript 4]), zinc hexadecafluoro (ZnPcF[subscript 16]) and zinc hexadecachloro (ZnPcCl[subscript 16]) phthalocyanines. The most effective water-soluble photocatalyst is ZnPcS[subscript mix] in terms of the high quantum yield obtained for 4-Np degradation (Φ[subscript 4-Np]) as well as its photostability. While ZnPc(COOH)[subscript 8] has the highest Φ[subscript 4-Np] value relative to the other water-soluble complexes, it degrades readily during photocatalysis. The Φ[subscript 4-Np] values were closely related to the singlet oxygen quantum yields Φ[subscript Δ] and hence aggregation. The rate constants for the reaction with 4-Np were kr = 0.67 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPcS[subscript mix] and 7.7 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPc(COOH)[subscript 8]. ClAlPc is the most effective photocatalyst relative to the other heterogeneous photocatalysts for the phototransformation of 4-Np, with 89 ± 8.4 % degradation of 4-Np achieved after 100 min. The least effective catalysts were ZnPcCl[subscript 16] and MgPc. The final products of the photocatalysis of 4-Np in the presence of the homogeneous photocatalysts include 4-nitrocatechol and hydroquinone, while degradation of 4-Np in the presence of the heterogeneous photocatalysts resulted in fumaric acid and 4-nitrocatechol. ClAlPc was employed for the heterogeneous photocatalysis of the non-systemic insecticide, methyl paraoxon. Complete degradation of the pesticide was confirmed by the disappearance of the HPLC trace for methyl paraoxon after 100 min of irradiation with visible light. The removal of 4-Np from an aqueous medium using commercially available Amberlite[superscript ®] IRA-900 modified with metal phthalocyanines was also investigated. The metallophthalocyanines immobilised onto the surface of Amberlite[superscript ®] IRA-900 include Fe (FePcS[subscript 4]), Co (CoPcS[subscript 4]) and Ni (NiPcS[subscript 4]) tetrasulphophthalocyanines, and differently sulphonated phthalocyanine mixtures of Fe (FePcS[subscript mix]), Co (CoPcS[subscript mix]) and Ni (NiPcS[subscript mix]). Adsorption rates were fastest for the modified adsorbents at pH 9. Using the Langmuir-Hinshelwood kinetic model, the complexes showed the following order of 4-Np adsorption: CoPcS[subscript mix] > NiPcS[subscript 4] > NiPcS[subscript mix] > FePcS[subscript 4] > FePcS[subscript mix] > CoPcS[subscript 4]. The adsorbents were regenerated using dilute HNO[subscript 3], with 76 % (7.6 x 10[superscript -5] mol) of 4-Np recovered within 150 min.
- Full Text:
- Date Issued: 2008
- Authors: Marais, Eloïse Ann
- Date: 2008
- Subjects: Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4343 , http://hdl.handle.net/10962/d1005005 , Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Description: Photodegradation of 4-nitrophenol (4-Np) in the presence of water-soluble zinc phthalocyanines and water-insoluble metallophthalocyanines is reported. The water-soluble phthalocyanines employed include zinc tetrasulphophthalocyanine (ZnPcS[subscript 4]), zinc octacarboxyphthalocyanine (ZnPc(COOH)[subscript 8]) and a sulphonated ZnPc containing a mixture of differently sulphonated derivatives (ZnPcS[subscript mix]), while the water-insoluble phthalocyanines used include unsubstituted magnesium (MgPc), zinc (ZnPc) and chloroaluminium (ClAlPc) phthalocyanine complexes and the ring-substituted zinc tetranitro (ZnPc(NO[subscript 2])[subscript 4]), zinc tetraamino (ZnPc(NH[subscript 2])[subscript 4]), zinc hexadecafluoro (ZnPcF[subscript 16]) and zinc hexadecachloro (ZnPcCl[subscript 16]) phthalocyanines. The most effective water-soluble photocatalyst is ZnPcS[subscript mix] in terms of the high quantum yield obtained for 4-Np degradation (Φ[subscript 4-Np]) as well as its photostability. While ZnPc(COOH)[subscript 8] has the highest Φ[subscript 4-Np] value relative to the other water-soluble complexes, it degrades readily during photocatalysis. The Φ[subscript 4-Np] values were closely related to the singlet oxygen quantum yields Φ[subscript Δ] and hence aggregation. The rate constants for the reaction with 4-Np were kr = 0.67 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPcS[subscript mix] and 7.7 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPc(COOH)[subscript 8]. ClAlPc is the most effective photocatalyst relative to the other heterogeneous photocatalysts for the phototransformation of 4-Np, with 89 ± 8.4 % degradation of 4-Np achieved after 100 min. The least effective catalysts were ZnPcCl[subscript 16] and MgPc. The final products of the photocatalysis of 4-Np in the presence of the homogeneous photocatalysts include 4-nitrocatechol and hydroquinone, while degradation of 4-Np in the presence of the heterogeneous photocatalysts resulted in fumaric acid and 4-nitrocatechol. ClAlPc was employed for the heterogeneous photocatalysis of the non-systemic insecticide, methyl paraoxon. Complete degradation of the pesticide was confirmed by the disappearance of the HPLC trace for methyl paraoxon after 100 min of irradiation with visible light. The removal of 4-Np from an aqueous medium using commercially available Amberlite[superscript ®] IRA-900 modified with metal phthalocyanines was also investigated. The metallophthalocyanines immobilised onto the surface of Amberlite[superscript ®] IRA-900 include Fe (FePcS[subscript 4]), Co (CoPcS[subscript 4]) and Ni (NiPcS[subscript 4]) tetrasulphophthalocyanines, and differently sulphonated phthalocyanine mixtures of Fe (FePcS[subscript mix]), Co (CoPcS[subscript mix]) and Ni (NiPcS[subscript mix]). Adsorption rates were fastest for the modified adsorbents at pH 9. Using the Langmuir-Hinshelwood kinetic model, the complexes showed the following order of 4-Np adsorption: CoPcS[subscript mix] > NiPcS[subscript 4] > NiPcS[subscript mix] > FePcS[subscript 4] > FePcS[subscript mix] > CoPcS[subscript 4]. The adsorbents were regenerated using dilute HNO[subscript 3], with 76 % (7.6 x 10[superscript -5] mol) of 4-Np recovered within 150 min.
- Full Text:
- Date Issued: 2008
Synthesis, photochemical and photophysical properties of gallium and indium phthalocyanine derivatives
- Authors: Chauke, Vongani Portia
- Date: 2008
- Subjects: Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4375 , http://hdl.handle.net/10962/d1005040 , Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Description: The syntheses of octasubstituted and unsusbstitituted Gallium(III) chloride and indium(III) chloride phthalocyanines (GaPc and InPc), their photophysical, photochemical and nonlinear optical parameters are hereby presented. The photocatalytic oxidation of 1-hexene using the synthesized GaPc and InPc complexes as well as electrochemical characterization is also presented in this thesis. Fluorescence quantum yields do not vary much among the four Ga complexes, except for complex 21c; therefore it was concluded that the effect of substituents is not significant among them. Solvents however, had an effect on the results. Lower Φ[subscript F] values were obtained in low viscosity solvents like toluene, relative to highly viscous solvents, such as DMSO. The triplet quantum yields were found to be lower in DMSO than in DMF and toluene. The rate constants for fluorescence, intersystem crossing and internal conversion as well as fluorescence and triplet lifetimes are reported. Photodegradation and singlet oxygen quantum yields have also been reported. There was no clear correlation between the latter parameters. It was however established that the four gallium MPcs were stable, within the allowed stability range for phthalocyanines. High quantum yields of triplet state (Φ[subscript T] ranging from 0.70 to 0.91 in dimethysulfoxide, DMSO) and singlet oxygen generation (Φ[subscript greek capital letter delta], ranging from 0.61 to 0.79 in DMSO) were obtained. Short triplet lifetimes 50 to 60 μs were obtained in DMSO). Calculated non-linear parameters of these complexes are compared with those of the corresponding GaPc derivatives and tetrasubstituted GaPc and InPc complexes. The optical limiting threshold intensity (I[subscript lim]) values for the InPc and GaPc derivatives were calculated and compared with those of corresponding tetrasubstituted InPc and GaPc complexes. The octasubstituted were found to be better optical limiters. Photocatalytic oxidation of 1-hexene by GaPc (21a-c) and InPc (22a-c) derivatives is also presented. The photocatalytic oxidation products for 1-hexene were 1,2- epoxyhexane and 1-hexen-3-ol. The % conversion values of 1-hexene and % selectivity of 1,2-epoxyhexane were generally higher for InPc derivatives. Even though InPc derivatives showed better photocatalytic results than GaPc derivatives, the former were less stable relative to the latter. Both type I and type II mechanism were implicated in the photocatalysis mechanism.
- Full Text:
- Date Issued: 2008
- Authors: Chauke, Vongani Portia
- Date: 2008
- Subjects: Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4375 , http://hdl.handle.net/10962/d1005040 , Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Description: The syntheses of octasubstituted and unsusbstitituted Gallium(III) chloride and indium(III) chloride phthalocyanines (GaPc and InPc), their photophysical, photochemical and nonlinear optical parameters are hereby presented. The photocatalytic oxidation of 1-hexene using the synthesized GaPc and InPc complexes as well as electrochemical characterization is also presented in this thesis. Fluorescence quantum yields do not vary much among the four Ga complexes, except for complex 21c; therefore it was concluded that the effect of substituents is not significant among them. Solvents however, had an effect on the results. Lower Φ[subscript F] values were obtained in low viscosity solvents like toluene, relative to highly viscous solvents, such as DMSO. The triplet quantum yields were found to be lower in DMSO than in DMF and toluene. The rate constants for fluorescence, intersystem crossing and internal conversion as well as fluorescence and triplet lifetimes are reported. Photodegradation and singlet oxygen quantum yields have also been reported. There was no clear correlation between the latter parameters. It was however established that the four gallium MPcs were stable, within the allowed stability range for phthalocyanines. High quantum yields of triplet state (Φ[subscript T] ranging from 0.70 to 0.91 in dimethysulfoxide, DMSO) and singlet oxygen generation (Φ[subscript greek capital letter delta], ranging from 0.61 to 0.79 in DMSO) were obtained. Short triplet lifetimes 50 to 60 μs were obtained in DMSO). Calculated non-linear parameters of these complexes are compared with those of the corresponding GaPc derivatives and tetrasubstituted GaPc and InPc complexes. The optical limiting threshold intensity (I[subscript lim]) values for the InPc and GaPc derivatives were calculated and compared with those of corresponding tetrasubstituted InPc and GaPc complexes. The octasubstituted were found to be better optical limiters. Photocatalytic oxidation of 1-hexene by GaPc (21a-c) and InPc (22a-c) derivatives is also presented. The photocatalytic oxidation products for 1-hexene were 1,2- epoxyhexane and 1-hexen-3-ol. The % conversion values of 1-hexene and % selectivity of 1,2-epoxyhexane were generally higher for InPc derivatives. Even though InPc derivatives showed better photocatalytic results than GaPc derivatives, the former were less stable relative to the latter. Both type I and type II mechanism were implicated in the photocatalysis mechanism.
- Full Text:
- Date Issued: 2008
Synthesis, photophysics and electrochemical study of tin macrocycles
- Authors: Khene, Mielie Samson
- Date: 2008
- Subjects: Electrochemistry , Photochemistry , Phthalocyanines , Macrocyclic compounds , Spectrum analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4376 , http://hdl.handle.net/10962/d1005041 , Electrochemistry , Photochemistry , Phthalocyanines , Macrocyclic compounds , Spectrum analysis
- Description: Three non-peripherally substituted tin(IV) macrocylic compounds, octahexylphthalocyaninato dichlorotin(IV) (35a), octahexyltetrabenzo-5,10,15-triazaporphyrinato dichlorotin(IV) (35b) and octadecylphthalocyaninato dichlorotin(IV) (35c) were synthesized and their photophysical and electrochemical behaviour studied. Complex (35b), containing a CH group in place of one of the aza nitrogen atom of the phthalocyanine core, shows a split Q band due to its lower symmetry. The triplet state quantum yields were found to be lower than would be expected on the basis of the heavy atom effect of tin as the central metal for phthalocyanine derivatives (35a and 35c). In contrast, (35b) shows a triplet quantum yield ΦT = 0.78. The triplet state lifetimes were solvent dependent, and were higher in THF than in toluene. Cyclic voltammetry and spectroelectrochemistry of the complexes revealed only ring based redox processes. This thesis also reports on the microwave syntheses of tetrasulphonated tin phthalocyanine and tetrasulphonated tin α,β,γ-tetrabenzcorrole. The latter was only formed at low ratios (< 1:8) of 4-sulfophthalic acid to urea. Both complexes are aggregated in aqueous media, but can be partly or fully disaggregated by the addition of Triton X-100. The SnTSTBC complex has lower triplet life times and yields, while binding constant and quenching (of bovine serum albumin) constant are lower for SnTSTBC, compared to SnTSPc. Finally Non-peripherally (α) tetra- (40) and octa-(38a) substituted dodecyl-mercapto tin(IV) phthalocyanines where synthesized and the electrochemical behavior studied. Cyclic voltammetry and spectroelectrochemistry show ring-based reductions for (38a) and (40); the former shows two ring oxidations, while the latter shows only one ring based oxidation. The adsorption kinetics of (38a) and (40) on a gold electrode have been investigated by electrochemical impedance spectroscopy (EIS). The equilibrium constant (K) for the adsorption and the Gibbs free energy ΔG(ads) of the self-assembled monolayer (SAMs) were evaluated based on the Frumkin isotherm. The interaction factor between adsorbate –adsorbate molecules is also discussed.
- Full Text:
- Date Issued: 2008
- Authors: Khene, Mielie Samson
- Date: 2008
- Subjects: Electrochemistry , Photochemistry , Phthalocyanines , Macrocyclic compounds , Spectrum analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4376 , http://hdl.handle.net/10962/d1005041 , Electrochemistry , Photochemistry , Phthalocyanines , Macrocyclic compounds , Spectrum analysis
- Description: Three non-peripherally substituted tin(IV) macrocylic compounds, octahexylphthalocyaninato dichlorotin(IV) (35a), octahexyltetrabenzo-5,10,15-triazaporphyrinato dichlorotin(IV) (35b) and octadecylphthalocyaninato dichlorotin(IV) (35c) were synthesized and their photophysical and electrochemical behaviour studied. Complex (35b), containing a CH group in place of one of the aza nitrogen atom of the phthalocyanine core, shows a split Q band due to its lower symmetry. The triplet state quantum yields were found to be lower than would be expected on the basis of the heavy atom effect of tin as the central metal for phthalocyanine derivatives (35a and 35c). In contrast, (35b) shows a triplet quantum yield ΦT = 0.78. The triplet state lifetimes were solvent dependent, and were higher in THF than in toluene. Cyclic voltammetry and spectroelectrochemistry of the complexes revealed only ring based redox processes. This thesis also reports on the microwave syntheses of tetrasulphonated tin phthalocyanine and tetrasulphonated tin α,β,γ-tetrabenzcorrole. The latter was only formed at low ratios (< 1:8) of 4-sulfophthalic acid to urea. Both complexes are aggregated in aqueous media, but can be partly or fully disaggregated by the addition of Triton X-100. The SnTSTBC complex has lower triplet life times and yields, while binding constant and quenching (of bovine serum albumin) constant are lower for SnTSTBC, compared to SnTSPc. Finally Non-peripherally (α) tetra- (40) and octa-(38a) substituted dodecyl-mercapto tin(IV) phthalocyanines where synthesized and the electrochemical behavior studied. Cyclic voltammetry and spectroelectrochemistry show ring-based reductions for (38a) and (40); the former shows two ring oxidations, while the latter shows only one ring based oxidation. The adsorption kinetics of (38a) and (40) on a gold electrode have been investigated by electrochemical impedance spectroscopy (EIS). The equilibrium constant (K) for the adsorption and the Gibbs free energy ΔG(ads) of the self-assembled monolayer (SAMs) were evaluated based on the Frumkin isotherm. The interaction factor between adsorbate –adsorbate molecules is also discussed.
- Full Text:
- Date Issued: 2008
- «
- ‹
- 1
- ›
- »