Introduction: In Ghana, Corchorus olitorius, Solanum macrocarpon and Amaranthus cruentus are gree... more Introduction: In Ghana, Corchorus olitorius, Solanum macrocarpon and Amaranthus cruentus are green leafy vegetables that are customarily eaten together with a starchy staple food. The present study aimed at assessing the ethanolic leaf extract of C. olitorius, S. macrocarpon and A. cruentus for antioxidant capacity, phytochemical property, nutritional and anti-nutrient content. Method: Phytochemical constituent and proximate analysis were determined using standard protocols. The DPPH scavenging activity was used to determine the antioxidant activity of the ethanolic leaf extracts from the three vegetables. The antinutrients phytate and oxalate were determined by titrimetric methods of analysis. Results: Pytochemical screening revealed the presence of tannins and flavonoids in C. olitorius, S. macrocarpon and A. cruentus. Alkaloids and saponins were present in C. olitorius and S. macrocarpon but not in A. cruentus. Terpenoids, steroids, carotenoids and coumarins were absent in all the three vegetables. Proximate analysis revealed varying levels of moisture, fat, protein, ash, crude fibre and carbohydrates in the three leafy vegetables. The DPPH scavenging showed 86.71%, 71.72% and 38.86% activity for S. macrocarpon, C. olitorius and A. cruentus respectively. The antinutrient results revealed an oxalate level of 2.7 ± 0.13% for C. olitorius, 6.43 ± 0.06% for A. cruentus and 12.32 ± 0.13% for S. macrocarpon. For levels of phytates, our results revealed a 3.084 ± 0.54%, 1.14 ± 0.26% and 1.71 ± 0.27% for C. olitorius, A. cruentus and S. macrocarpon, respectively. Conclusion: The current study has shown that C. olitorius, A. cruentus and S. macrocarpon possess important phytochemicals, nutrients and significant antioxidant activity, suggesting a potential of these vegetables against diverse disease, if eaten by humans.
The oxo complexes of group VII B are of great interest for their potential toward epoxidation and... more The oxo complexes of group VII B are of great interest for their potential toward epoxidation and dihydroxylation. In this work, the mechanisms of oxidation of ethylene by rhenium-oxo complexes of the type LReO3 (L = O(-), Cl, CH3, OCH3, Cp, NPH3) have been explored at the B3LYP/LACVP* level of theory. The activation barriers and reaction energies for the stepwise and concerted addition pathways involving multiple spin states have been computed. In the reaction of LReO3 (L = O(-), Cl, CH3, OCH3, Cp, NPH3) with ethylene, it was found that the concerted [3 + 2] addition pathway on the singlet potential energy surfaces leading to the formation of a dioxylate intermediate is favored over the [2 + 2] addition pathway leading to the formation of a metallaoxetane intermediate and its re-arrangement to form the dioxylate. The activation barrier for the formation of the dioxylate on the singlet PES for the ligands studied is found to follow the order O(-) > CH3 > NPH3 > CH3O(-) > Cl(-) > Cp and the reaction energies follow the order CH3 > O(-) > NPH3 > CH3O(-) > Cl(-) > Cp. On the doublet PES, the [2 + 2] addition leading to the formation the metallaoxetane intermediate is favored over dioxylate formation for the ligands L = CH3, CH3O(-), Cl(-). The activation barriers for the formation of the metallaoxetane intermediate are found to increase for the ligands in the order CH3 < Cl(-) < CH3O(-) while the reaction energies follow the order Cl(-) < CH3O(-) < CH3. The subsequent re-arrangement of the metallaoxetane intermediate to the dioxylate is only feasible in the case of ReO3(OCH3). Of all the complexes studied, the best dioxylating catalyst is ReO3Cp (singlet surface); the best epoxidation catalyst is ReO3Cl (singlet surface); and the best metallaoxetane formation catalyst is ReO3(NPH3) (triplet surface).
Heterocyclic compounds are vital in rational drug design by providing convenient means for the op... more Heterocyclic compounds are vital in rational drug design by providing convenient means for the optimization of drugs or drug candidates. Isoxazolidine (a heterocyclic compound) derived from the (3 + 2) cycloaddition reaction is reported to possess anticancer, antiviral, antibacterial, and anti-inflammatory properties. The mechanistic study of the chemo-, regio-, and stereo-selectivities of the (3 + 2) cycloaddition reaction (32CA) of diarylnitrones (A1) to 1-(4-nitrophenyl)-5H-pyrrolin-2-one (A2) has been conducted using the density functional theory (DFT) method at the M06/6-311G (d, p ) computational level. The 32CA reaction of A1 and A2 proceeds through a chemo-selective addition of A1 across the C=C olefinic bond of A2 to furnish both kinetically and thermodynamically favored reaction routes. The effect of substitution on the 32CA reaction has been studied using a representative set of electron-acceptor and electron-releasing groups on both A1 and A2. The chemo-, regio-, and ste...
Lake Bosomtwe in the Ashanti Region of Ghana is one of the largest naturally occurring lake in We... more Lake Bosomtwe in the Ashanti Region of Ghana is one of the largest naturally occurring lake in West Africa. The lake is surrounded by about 36 farming and fishing communities that use synthetic pesticides and herbicide in the cultivation of crops. These chemicals are likely to leak into the tributaries, contaminate the lake, and threaten the life of the aquatic animals. For this reason, a study of the levels of the active components of the pesticides in the lake were measured to monitor the water quality. A Gas Chromatographic equipped with Electron Capture Detector (GC-ECD) was employed in the measurements and levels of organochlorine, organophosphorus and pyrethoids. The GC-ECD analysis revealed that, the mean concentrations of organochlorines in the water sample were, Beta – HCH (0.03µg/L), Gamma – HCH (0.015 µg/L), Delta – HCH (0.012 µg/L), Endrin (0.014 µg/L), Beta-endosulfan (0.01 µg/L), Endosulfan (0.028 µg/L), and p, p’- DDT (0.012 µg/L). Heptachlor, Alpha-endosulfan, p,p’- ...
International Journal of Innovative Research and Development
Polystyrene is an aromatic hydrocarbon plastic material with applications in the packaging, food,... more Polystyrene is an aromatic hydrocarbon plastic material with applications in the packaging, food, and construction industries. As a packaging material, it protects items against shocks and acts as an insulator in the construction of buildings and food preservation. The polystyrene bowl for food packaging has become a convention in the food and pastries industry in Ghana due to its clean, lightweight, and insulation properties. However, the corresponding waste litters its environment, chocks gutters, and does not decompose. For this reason, we explored the hot melt recycling technique to convert the PS wastes into valuable plastic plates that finds application in the artifact and souvenir industry. The incorporation of a 20% v/w lauric fatty acid (LFA) into the material matrix blocked micro holes in the finished product and induced a smooth surface. Characterizations included experiments such as Fourier Transform-Infra Red spectroscopy, melting point determination, tensile testing, a...
Metakaolin is an anhydrous clayey material obtained by the calcination of kaolin. This material h... more Metakaolin is an anhydrous clayey material obtained by the calcination of kaolin. This material has been utilized as a valuable substitute or additive for concrete/cement mixtures and many other applications. The current study is on the production and characterization of metakaolin together with its adsorbent properties for the purification and regeneration of spent lubrication oil. Metakaolin was produced from the calcination of kaolin from Wassa in the Western region of Ghana. The metakaolin was characterized by using X-ray fluorescence (XRF), X-ray diffractometry (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX), and Fourier transform infra-red (FT-IR). The metakaolin was then used as an adsorbent in the regeneration of the engine lubrication oil, mimicking the acid-clay percolation process. The test results show that the efficiency of metakaolin in removing heavy metals from the used oil using an atomic absorption spectrometer (AAS) was 13.25% ...
The bandgap energy and band alignment of the CdS/SiH vdW heterostructure were modified by applyin... more The bandgap energy and band alignment of the CdS/SiH vdW heterostructure were modified by applying biaxial strain and an external electric field.
The oxidation of ethylene catalyzed by manganese and technetium oxo complexes of the type MO3L (M... more The oxidation of ethylene catalyzed by manganese and technetium oxo complexes of the type MO3L (M = Tc, Mn, and L = O−, Cl−, F−, OH−, Br−, I−) on both singlet and triplet potential energy surfaces (PESs) have been studied. All molecular structures were stable on the singlet PES except for the formation of the dioxylate intermediate for the MnO3L (L = O−, Cl−, F−, OH−, Br−, I−) catalyzed pathway. Frontier molecular orbital calculations showed that electrons flow from the HOMO of ethylene into the LUMO of the metal-oxo complex for all complexes studied except for MO3L (M = Tc, Mn, and L = O−) where the vice versa occurs. In the reaction of both TcO3L and MnO3L (L = O−, Cl−, F−, OH−, Br−, I−) with ethylene, it was observed that the formation of the dioxylate intermediate along the [3 + 2] addition pathway on the singlet reaction surface is both kinetically and thermodynamically favorable over its formation via the [2 + 2] pathway. Furthermore, it was observed that TcO4− and MnO4− catalyzed pathways exclusively form diols on the singlet PES. The formation of epoxides on the singlet surface is kinetically favorable through the [2 + 1] and [2 + 2] channel for the MnO3L (L = F−, Cl−, Br−, I−, OH−) and TcO3L (L = F−, Cl−, Br−, I−, OH−) catalyzed surfaces respectively. In all cases, the TcO3L complexes were found to be polar compared to the MnO3L complexes. The MnO4− (singlet) and MnO3F (singlet) are the best catalysts for the exclusive formation of the diols and epoxides respectively.
The management of solid wastes at the workplace in Ghana is characterised by mixed wastes pickup ... more The management of solid wastes at the workplace in Ghana is characterised by mixed wastes pickup delays, dustbin overflows and leakage of plastic bags into the environment. Benefits from the pilot of source sorting as a mitigation measure at the workplace are unavailable in literature. Hence, the study employed descriptive statistical tools to assess the advantages of a piloted source sorting system at the CSIR-IIR. The sampled size was 100 staff with an 80% questionnaire recovery rate. The analysis of data showed that, the implementation of segregation at source transformed the social approach of workers towards waste management. Most workers (97.7%) preferred sorting their wastes at source irrespective of the location of the generation point. A congenial environment was created by the source separation infrastructure, which made staff worked better, (70% responses). The majority of staff (95.2%) confirmed the savings made by the Institute on the cost of landfilling. The sorting a...
Materials for Renewable and Sustainable Energy, 2021
Understanding the mechanism of CO2 reduction on iron is crucial for the design of more efficient ... more Understanding the mechanism of CO2 reduction on iron is crucial for the design of more efficient and cheaper iron electrocatalyst for CO2 conversion. In the present study, we have employed spin-polarized density functional theory calculations within the generalized gradient approximation (DFT-GGA) to elucidate the mechanism of CO2 reduction into carbon monoxide and formic acid on the Fe (100) facet. We also sort to understand the transformations of the other isomers of adsorbed CO2 on iron as earlier mechanistic studies are centred on the transformations of the C2v geometry alone and not the other possible conformations i.e., flip-C2v and Cs modes. Two alternative reduction routes were considered i.e., the direct CO2 dissociation against the hydrogen-assisted CO2 transformation through formate and carboxylate into CO and formic acid. Our results show that CO2 in the C2v mode is the precursor to the formation of both products i.e., CO and formic acid. Both the formation and transform...
Transition-metal-mediated oxygen transfer reactions are of importance in both industry and academ... more Transition-metal-mediated oxygen transfer reactions are of importance in both industry and academia; thus, a series of rhenium oxo complexes of the type ReO3L (L = O−, Cl−, F−, OH−, Br−, I−) and their effects as oxidation catalysts on ethylene have been studied. The activation and reaction energies for the addition pathways involving multiple spin states (singlet and triplet) have been computed. In all cases, structures on the singlet potential energy surfaces showed higher stability compared to their counterparts on the triplet potential energy surfaces (PESs). Frontier Molecular Orbital calculations show electrons flow from the HOMO of ethylene to the LUMO of rhenium for all complexes studied except ReO4− where the reverse case occurs. In the reaction between ReO3L (L = O−, Cl−, F−, OH−, Br−, and I−) and ethylene, the concerted [3 + 2] addition pathway on the singlet PES leading to the formation of dioxylate intermediate is favored over the [2 + 2] addition pathway leading to the ...
The mechanisms of LMnO3 (L = O−, Cl, NPH3, CH3, and Cp)-catalyzed oxidation of ethyne has been st... more The mechanisms of LMnO3 (L = O−, Cl, NPH3, CH3, and Cp)-catalyzed oxidation of ethyne has been studied on the singlet and triplet hypersurfaces at the M06/6-311G(d) level of theory. For the first step, the [3 + 2] pathways to the formation of the metalla-2,5-dioxol-3-ene intermediate are kinetically and thermodynamically the most favored pathways in all the complexes studied; it is favored over the [2 + 2] addition pathways to the metallaoxetene intermediate. The formation of the oxirene precursor that could give the oxirene the reported key intermediates in the ozonolysis of alkynes would most likely result from the oxidation of ethyne by MnO3Cl on the triplet potential energy surface (PES). [3 + 2] versus [2 + 1] addition of MnO3Cl with ethyne at the M06/6-311G(d) level of theory [3 + 2] versus [2 + 1] addition of MnO3Cl with ethyne at the M06/6-311G(d) level of theory
Despite series of experimental studies that reveal unique activities of late 3d transition metals... more Despite series of experimental studies that reveal unique activities of late 3d transition metals and their role in microorganisms known for CO2 conversion, these surfaces are not industrially viable yet. An insight into the elementary steps of surface catalytic processes is crucial for effective surface modification and design. The mechanisms of CO2 transformation into CO, through the reverse water gas shift and methane reforming, are being studied. Mechanisms of CO2 methanation is also being explored by the Sabatier reaction into methane. This review covers both experimental and theoretical studies into the mechanisms of CO2 reduction into CO and methane, on single metals and bimetals of late 3d transition metals, i.e. Fe, Co, Ni, Cu and Zn. This paper highlights progress and gaps still existing in our knowledge of the reaction mechanisms. These mechanistic studies reveal CO2 activation and reduction mechanisms are specific to both composition and surface facet. Surfaces with least CO2 binding potential are seen to favour CO and O binding and provide higher barriers to dissociation. No direct correlation has been seen between binding strength of CO2 and its degree of activation. Hydrogen-assisted dissociation is seen to be generally favoured kinetically on Cu and Ni surfaces over direct dissociation except on the Ni (211) surface. Methane production on Cu and Ni surfaces is seen to occur via the non-formate pathway. Hydrogenation reactions have focused on Cu and Ni, and more needs to be done on other surfaces, i.e. Co, Fe and Zn.
Materials for Renewable and Sustainable Energy, 2021
The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped La... more The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped LaMnO3 (LBM25) have been studied at the density functional theory (DFT) with Hubbard correction and the results compared with adsorption on 25% Ca-doped LaMnO3 (LCM25) and Sr-doped LaMnO3 (LSM25). The trend in the reduction energies at the Mn cation sites are predicted to be in the order LSM25 < LBM25 < LCM25. In addition, the trend in dissociation energies for the most exothermic dissociated precursors follow the order LBM25 < LSM25 < LCM25. The adsorption energies (− 2.14 to − 2.41 eV) calculated for the molecular O2 precursors at the Mn cation sites of LCM25, LSM25 and LBM25 are thermodynamically stable, when compared directly with the adsorption energies (Eads = − 0.56 to − 1.67 eV) reported for the stable molecular O2 precursors on the Pt, Ni, Pd, Cu and Ir {111} surfaces. The predicted Gibbs energies as a function of temperature (T = 500–1100 °C) and pressures (p = 0.2 at...
Introduction: In Ghana, Corchorus olitorius, Solanum macrocarpon and Amaranthus cruentus are gree... more Introduction: In Ghana, Corchorus olitorius, Solanum macrocarpon and Amaranthus cruentus are green leafy vegetables that are customarily eaten together with a starchy staple food. The present study aimed at assessing the ethanolic leaf extract of C. olitorius, S. macrocarpon and A. cruentus for antioxidant capacity, phytochemical property, nutritional and anti-nutrient content. Method: Phytochemical constituent and proximate analysis were determined using standard protocols. The DPPH scavenging activity was used to determine the antioxidant activity of the ethanolic leaf extracts from the three vegetables. The antinutrients phytate and oxalate were determined by titrimetric methods of analysis. Results: Pytochemical screening revealed the presence of tannins and flavonoids in C. olitorius, S. macrocarpon and A. cruentus. Alkaloids and saponins were present in C. olitorius and S. macrocarpon but not in A. cruentus. Terpenoids, steroids, carotenoids and coumarins were absent in all the three vegetables. Proximate analysis revealed varying levels of moisture, fat, protein, ash, crude fibre and carbohydrates in the three leafy vegetables. The DPPH scavenging showed 86.71%, 71.72% and 38.86% activity for S. macrocarpon, C. olitorius and A. cruentus respectively. The antinutrient results revealed an oxalate level of 2.7 ± 0.13% for C. olitorius, 6.43 ± 0.06% for A. cruentus and 12.32 ± 0.13% for S. macrocarpon. For levels of phytates, our results revealed a 3.084 ± 0.54%, 1.14 ± 0.26% and 1.71 ± 0.27% for C. olitorius, A. cruentus and S. macrocarpon, respectively. Conclusion: The current study has shown that C. olitorius, A. cruentus and S. macrocarpon possess important phytochemicals, nutrients and significant antioxidant activity, suggesting a potential of these vegetables against diverse disease, if eaten by humans.
The oxo complexes of group VII B are of great interest for their potential toward epoxidation and... more The oxo complexes of group VII B are of great interest for their potential toward epoxidation and dihydroxylation. In this work, the mechanisms of oxidation of ethylene by rhenium-oxo complexes of the type LReO3 (L = O(-), Cl, CH3, OCH3, Cp, NPH3) have been explored at the B3LYP/LACVP* level of theory. The activation barriers and reaction energies for the stepwise and concerted addition pathways involving multiple spin states have been computed. In the reaction of LReO3 (L = O(-), Cl, CH3, OCH3, Cp, NPH3) with ethylene, it was found that the concerted [3 + 2] addition pathway on the singlet potential energy surfaces leading to the formation of a dioxylate intermediate is favored over the [2 + 2] addition pathway leading to the formation of a metallaoxetane intermediate and its re-arrangement to form the dioxylate. The activation barrier for the formation of the dioxylate on the singlet PES for the ligands studied is found to follow the order O(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; CH3 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; NPH3 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; CH3O(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Cl(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Cp and the reaction energies follow the order CH3 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; O(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; NPH3 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; CH3O(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Cl(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Cp. On the doublet PES, the [2 + 2] addition leading to the formation the metallaoxetane intermediate is favored over dioxylate formation for the ligands L = CH3, CH3O(-), Cl(-). The activation barriers for the formation of the metallaoxetane intermediate are found to increase for the ligands in the order CH3 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; Cl(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; CH3O(-) while the reaction energies follow the order Cl(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; CH3O(-) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; CH3. The subsequent re-arrangement of the metallaoxetane intermediate to the dioxylate is only feasible in the case of ReO3(OCH3). Of all the complexes studied, the best dioxylating catalyst is ReO3Cp (singlet surface); the best epoxidation catalyst is ReO3Cl (singlet surface); and the best metallaoxetane formation catalyst is ReO3(NPH3) (triplet surface).
Heterocyclic compounds are vital in rational drug design by providing convenient means for the op... more Heterocyclic compounds are vital in rational drug design by providing convenient means for the optimization of drugs or drug candidates. Isoxazolidine (a heterocyclic compound) derived from the (3 + 2) cycloaddition reaction is reported to possess anticancer, antiviral, antibacterial, and anti-inflammatory properties. The mechanistic study of the chemo-, regio-, and stereo-selectivities of the (3 + 2) cycloaddition reaction (32CA) of diarylnitrones (A1) to 1-(4-nitrophenyl)-5H-pyrrolin-2-one (A2) has been conducted using the density functional theory (DFT) method at the M06/6-311G (d, p ) computational level. The 32CA reaction of A1 and A2 proceeds through a chemo-selective addition of A1 across the C=C olefinic bond of A2 to furnish both kinetically and thermodynamically favored reaction routes. The effect of substitution on the 32CA reaction has been studied using a representative set of electron-acceptor and electron-releasing groups on both A1 and A2. The chemo-, regio-, and ste...
Lake Bosomtwe in the Ashanti Region of Ghana is one of the largest naturally occurring lake in We... more Lake Bosomtwe in the Ashanti Region of Ghana is one of the largest naturally occurring lake in West Africa. The lake is surrounded by about 36 farming and fishing communities that use synthetic pesticides and herbicide in the cultivation of crops. These chemicals are likely to leak into the tributaries, contaminate the lake, and threaten the life of the aquatic animals. For this reason, a study of the levels of the active components of the pesticides in the lake were measured to monitor the water quality. A Gas Chromatographic equipped with Electron Capture Detector (GC-ECD) was employed in the measurements and levels of organochlorine, organophosphorus and pyrethoids. The GC-ECD analysis revealed that, the mean concentrations of organochlorines in the water sample were, Beta – HCH (0.03µg/L), Gamma – HCH (0.015 µg/L), Delta – HCH (0.012 µg/L), Endrin (0.014 µg/L), Beta-endosulfan (0.01 µg/L), Endosulfan (0.028 µg/L), and p, p’- DDT (0.012 µg/L). Heptachlor, Alpha-endosulfan, p,p’- ...
International Journal of Innovative Research and Development
Polystyrene is an aromatic hydrocarbon plastic material with applications in the packaging, food,... more Polystyrene is an aromatic hydrocarbon plastic material with applications in the packaging, food, and construction industries. As a packaging material, it protects items against shocks and acts as an insulator in the construction of buildings and food preservation. The polystyrene bowl for food packaging has become a convention in the food and pastries industry in Ghana due to its clean, lightweight, and insulation properties. However, the corresponding waste litters its environment, chocks gutters, and does not decompose. For this reason, we explored the hot melt recycling technique to convert the PS wastes into valuable plastic plates that finds application in the artifact and souvenir industry. The incorporation of a 20% v/w lauric fatty acid (LFA) into the material matrix blocked micro holes in the finished product and induced a smooth surface. Characterizations included experiments such as Fourier Transform-Infra Red spectroscopy, melting point determination, tensile testing, a...
Metakaolin is an anhydrous clayey material obtained by the calcination of kaolin. This material h... more Metakaolin is an anhydrous clayey material obtained by the calcination of kaolin. This material has been utilized as a valuable substitute or additive for concrete/cement mixtures and many other applications. The current study is on the production and characterization of metakaolin together with its adsorbent properties for the purification and regeneration of spent lubrication oil. Metakaolin was produced from the calcination of kaolin from Wassa in the Western region of Ghana. The metakaolin was characterized by using X-ray fluorescence (XRF), X-ray diffractometry (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX), and Fourier transform infra-red (FT-IR). The metakaolin was then used as an adsorbent in the regeneration of the engine lubrication oil, mimicking the acid-clay percolation process. The test results show that the efficiency of metakaolin in removing heavy metals from the used oil using an atomic absorption spectrometer (AAS) was 13.25% ...
The bandgap energy and band alignment of the CdS/SiH vdW heterostructure were modified by applyin... more The bandgap energy and band alignment of the CdS/SiH vdW heterostructure were modified by applying biaxial strain and an external electric field.
The oxidation of ethylene catalyzed by manganese and technetium oxo complexes of the type MO3L (M... more The oxidation of ethylene catalyzed by manganese and technetium oxo complexes of the type MO3L (M = Tc, Mn, and L = O−, Cl−, F−, OH−, Br−, I−) on both singlet and triplet potential energy surfaces (PESs) have been studied. All molecular structures were stable on the singlet PES except for the formation of the dioxylate intermediate for the MnO3L (L = O−, Cl−, F−, OH−, Br−, I−) catalyzed pathway. Frontier molecular orbital calculations showed that electrons flow from the HOMO of ethylene into the LUMO of the metal-oxo complex for all complexes studied except for MO3L (M = Tc, Mn, and L = O−) where the vice versa occurs. In the reaction of both TcO3L and MnO3L (L = O−, Cl−, F−, OH−, Br−, I−) with ethylene, it was observed that the formation of the dioxylate intermediate along the [3 + 2] addition pathway on the singlet reaction surface is both kinetically and thermodynamically favorable over its formation via the [2 + 2] pathway. Furthermore, it was observed that TcO4− and MnO4− catalyzed pathways exclusively form diols on the singlet PES. The formation of epoxides on the singlet surface is kinetically favorable through the [2 + 1] and [2 + 2] channel for the MnO3L (L = F−, Cl−, Br−, I−, OH−) and TcO3L (L = F−, Cl−, Br−, I−, OH−) catalyzed surfaces respectively. In all cases, the TcO3L complexes were found to be polar compared to the MnO3L complexes. The MnO4− (singlet) and MnO3F (singlet) are the best catalysts for the exclusive formation of the diols and epoxides respectively.
The management of solid wastes at the workplace in Ghana is characterised by mixed wastes pickup ... more The management of solid wastes at the workplace in Ghana is characterised by mixed wastes pickup delays, dustbin overflows and leakage of plastic bags into the environment. Benefits from the pilot of source sorting as a mitigation measure at the workplace are unavailable in literature. Hence, the study employed descriptive statistical tools to assess the advantages of a piloted source sorting system at the CSIR-IIR. The sampled size was 100 staff with an 80% questionnaire recovery rate. The analysis of data showed that, the implementation of segregation at source transformed the social approach of workers towards waste management. Most workers (97.7%) preferred sorting their wastes at source irrespective of the location of the generation point. A congenial environment was created by the source separation infrastructure, which made staff worked better, (70% responses). The majority of staff (95.2%) confirmed the savings made by the Institute on the cost of landfilling. The sorting a...
Materials for Renewable and Sustainable Energy, 2021
Understanding the mechanism of CO2 reduction on iron is crucial for the design of more efficient ... more Understanding the mechanism of CO2 reduction on iron is crucial for the design of more efficient and cheaper iron electrocatalyst for CO2 conversion. In the present study, we have employed spin-polarized density functional theory calculations within the generalized gradient approximation (DFT-GGA) to elucidate the mechanism of CO2 reduction into carbon monoxide and formic acid on the Fe (100) facet. We also sort to understand the transformations of the other isomers of adsorbed CO2 on iron as earlier mechanistic studies are centred on the transformations of the C2v geometry alone and not the other possible conformations i.e., flip-C2v and Cs modes. Two alternative reduction routes were considered i.e., the direct CO2 dissociation against the hydrogen-assisted CO2 transformation through formate and carboxylate into CO and formic acid. Our results show that CO2 in the C2v mode is the precursor to the formation of both products i.e., CO and formic acid. Both the formation and transform...
Transition-metal-mediated oxygen transfer reactions are of importance in both industry and academ... more Transition-metal-mediated oxygen transfer reactions are of importance in both industry and academia; thus, a series of rhenium oxo complexes of the type ReO3L (L = O−, Cl−, F−, OH−, Br−, I−) and their effects as oxidation catalysts on ethylene have been studied. The activation and reaction energies for the addition pathways involving multiple spin states (singlet and triplet) have been computed. In all cases, structures on the singlet potential energy surfaces showed higher stability compared to their counterparts on the triplet potential energy surfaces (PESs). Frontier Molecular Orbital calculations show electrons flow from the HOMO of ethylene to the LUMO of rhenium for all complexes studied except ReO4− where the reverse case occurs. In the reaction between ReO3L (L = O−, Cl−, F−, OH−, Br−, and I−) and ethylene, the concerted [3 + 2] addition pathway on the singlet PES leading to the formation of dioxylate intermediate is favored over the [2 + 2] addition pathway leading to the ...
The mechanisms of LMnO3 (L = O−, Cl, NPH3, CH3, and Cp)-catalyzed oxidation of ethyne has been st... more The mechanisms of LMnO3 (L = O−, Cl, NPH3, CH3, and Cp)-catalyzed oxidation of ethyne has been studied on the singlet and triplet hypersurfaces at the M06/6-311G(d) level of theory. For the first step, the [3 + 2] pathways to the formation of the metalla-2,5-dioxol-3-ene intermediate are kinetically and thermodynamically the most favored pathways in all the complexes studied; it is favored over the [2 + 2] addition pathways to the metallaoxetene intermediate. The formation of the oxirene precursor that could give the oxirene the reported key intermediates in the ozonolysis of alkynes would most likely result from the oxidation of ethyne by MnO3Cl on the triplet potential energy surface (PES). [3 + 2] versus [2 + 1] addition of MnO3Cl with ethyne at the M06/6-311G(d) level of theory [3 + 2] versus [2 + 1] addition of MnO3Cl with ethyne at the M06/6-311G(d) level of theory
Despite series of experimental studies that reveal unique activities of late 3d transition metals... more Despite series of experimental studies that reveal unique activities of late 3d transition metals and their role in microorganisms known for CO2 conversion, these surfaces are not industrially viable yet. An insight into the elementary steps of surface catalytic processes is crucial for effective surface modification and design. The mechanisms of CO2 transformation into CO, through the reverse water gas shift and methane reforming, are being studied. Mechanisms of CO2 methanation is also being explored by the Sabatier reaction into methane. This review covers both experimental and theoretical studies into the mechanisms of CO2 reduction into CO and methane, on single metals and bimetals of late 3d transition metals, i.e. Fe, Co, Ni, Cu and Zn. This paper highlights progress and gaps still existing in our knowledge of the reaction mechanisms. These mechanistic studies reveal CO2 activation and reduction mechanisms are specific to both composition and surface facet. Surfaces with least CO2 binding potential are seen to favour CO and O binding and provide higher barriers to dissociation. No direct correlation has been seen between binding strength of CO2 and its degree of activation. Hydrogen-assisted dissociation is seen to be generally favoured kinetically on Cu and Ni surfaces over direct dissociation except on the Ni (211) surface. Methane production on Cu and Ni surfaces is seen to occur via the non-formate pathway. Hydrogenation reactions have focused on Cu and Ni, and more needs to be done on other surfaces, i.e. Co, Fe and Zn.
Materials for Renewable and Sustainable Energy, 2021
The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped La... more The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped LaMnO3 (LBM25) have been studied at the density functional theory (DFT) with Hubbard correction and the results compared with adsorption on 25% Ca-doped LaMnO3 (LCM25) and Sr-doped LaMnO3 (LSM25). The trend in the reduction energies at the Mn cation sites are predicted to be in the order LSM25 < LBM25 < LCM25. In addition, the trend in dissociation energies for the most exothermic dissociated precursors follow the order LBM25 < LSM25 < LCM25. The adsorption energies (− 2.14 to − 2.41 eV) calculated for the molecular O2 precursors at the Mn cation sites of LCM25, LSM25 and LBM25 are thermodynamically stable, when compared directly with the adsorption energies (Eads = − 0.56 to − 1.67 eV) reported for the stable molecular O2 precursors on the Pt, Ni, Pd, Cu and Ir {111} surfaces. The predicted Gibbs energies as a function of temperature (T = 500–1100 °C) and pressures (p = 0.2 at...
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Papers by Albert Aniagyei