Activated carbon from lignocellulosic waste residues: effect of activating agent on porosity characteristics and use as adsorbents for organic species
- Olorundare, O F, Okonkwo, J O, Msagati, T A M, Mamba, Bhekie B, Krause, Rui W M
- Authors: Olorundare, O F , Okonkwo, J O , Msagati, T A M , Mamba, Bhekie B , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125233 , vital:35748 , https://doi.org/10.1007/s11270-014-1876-2
- Description: This paper reports on the effect of activating agents such as the impregnation ratio of phosphoric acid (1:1–1:5) at constant activation temperature on the performance of porous activated carbon from waste residues (maize tassel). The variation in the impregnation ratio of the produced activated carbon (AC) from 1:1 to 1:5 enabled the preparation of a high surface area (1,263 m2/g) and a large pore volume (1.592 cm3/g) of AC produced from maize tassel (MT) using a convectional chemical activating agent (phosphoric acid). Impregnation ratios (IR) of the precursors were varied between 1:1 and 1:5 in which it was found that the ratio of 1:4 was optimal based on the high surface area, while 1:5 has the optimal pore volume value for the produced activated carbon.
- Full Text:
- Date Issued: 2014
- Authors: Olorundare, O F , Okonkwo, J O , Msagati, T A M , Mamba, Bhekie B , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125233 , vital:35748 , https://doi.org/10.1007/s11270-014-1876-2
- Description: This paper reports on the effect of activating agents such as the impregnation ratio of phosphoric acid (1:1–1:5) at constant activation temperature on the performance of porous activated carbon from waste residues (maize tassel). The variation in the impregnation ratio of the produced activated carbon (AC) from 1:1 to 1:5 enabled the preparation of a high surface area (1,263 m2/g) and a large pore volume (1.592 cm3/g) of AC produced from maize tassel (MT) using a convectional chemical activating agent (phosphoric acid). Impregnation ratios (IR) of the precursors were varied between 1:1 and 1:5 in which it was found that the ratio of 1:4 was optimal based on the high surface area, while 1:5 has the optimal pore volume value for the produced activated carbon.
- Full Text:
- Date Issued: 2014
Comparison between base metals and platinum group metals in nitrogen, M codoped TiO 2 (M= Fe, Cu, Pd, Os) for photocatalytic removal of an organic dye in water
- Kuvarega, Alex T, Mamba, Bhekie B, Krause, Rui W M
- Authors: Kuvarega, Alex T , Mamba, Bhekie B , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125129 , vital:35734 , https://doi.org/10.1155/2014/962102
- Description: The photocatalytic performance of a number of nonmetal and metal codoped TiO2 for the degradation of eosin yellow under simulated solar radiation was investigated. The synthesised materials were characterised by FTIR, Raman spectroscopy, XRD, DRUV-Vis, SEM, and TEM.The N, metal codoped TiO2 containing 0.5 wt.% of the metal consisted mainly of the anatase phase, with a particle size range of 15–28 nm. The particles were largely spherical and shifted the absorption edge well into the visible region. Band gap reduction was more pronounced for the N, PGM codoped TiO2 compared to N, base metal codoped samples. Codoping led to an enhancement in the photocatalytic activity of the materials for the degradation of eosin yellow. N, Pd codoped TiO2 was the most effective photocatalyst (99.9% dye removal) while N, Cu codoped TiO2 showed the least activity (25.5% removal). The mechanism for the photocatalytic enhancement was proposed on the basis of formation of an electron deficient Schottky barrier at the semiconductor-metal interface, which acts as an electron sink and thus retards electron-hole recombination. It was shown that the ability of the photocatalyst to degrade the dye depends on the nature and type of the metal dopant in the codoped TiO2 system.
- Full Text:
- Date Issued: 2014
- Authors: Kuvarega, Alex T , Mamba, Bhekie B , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125129 , vital:35734 , https://doi.org/10.1155/2014/962102
- Description: The photocatalytic performance of a number of nonmetal and metal codoped TiO2 for the degradation of eosin yellow under simulated solar radiation was investigated. The synthesised materials were characterised by FTIR, Raman spectroscopy, XRD, DRUV-Vis, SEM, and TEM.The N, metal codoped TiO2 containing 0.5 wt.% of the metal consisted mainly of the anatase phase, with a particle size range of 15–28 nm. The particles were largely spherical and shifted the absorption edge well into the visible region. Band gap reduction was more pronounced for the N, PGM codoped TiO2 compared to N, base metal codoped samples. Codoping led to an enhancement in the photocatalytic activity of the materials for the degradation of eosin yellow. N, Pd codoped TiO2 was the most effective photocatalyst (99.9% dye removal) while N, Cu codoped TiO2 showed the least activity (25.5% removal). The mechanism for the photocatalytic enhancement was proposed on the basis of formation of an electron deficient Schottky barrier at the semiconductor-metal interface, which acts as an electron sink and thus retards electron-hole recombination. It was shown that the ability of the photocatalyst to degrade the dye depends on the nature and type of the metal dopant in the codoped TiO2 system.
- Full Text:
- Date Issued: 2014
Cytotoxicity, phytochemical analysis and antioxidant activity of crude extracts from Rhizomes of Elephantorrhiza Elephantina and Pentanisia Prunelloides
- Mpofu, Smart J, Msagati, Titus A M, Krause, Rui W M
- Authors: Mpofu, Smart J , Msagati, Titus A M , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125097 , vital:35728 , https://doi.org/10.4314/ajtcam.v11i1.6
- Description: Background: Elephantorrhiza elephantina (Ee) and Pentanisia prunelloides (Pp) are two medicinal plants which are widely used to remedy various ailments including diarrhoea, dysentery, inflammation, fever, rheumatism, heartburn, tuberculosis, haemorrhoids, skin diseases, perforated peptic ulcers and sore joints in southern Africa (South Africa, Swaziland, Botswana and Zimbabwe). The following study was conducted to explore the in vitro cytotoxicity, antioxidant properties and phytochemical profile of the two medicinal plants. Materials and Methods: The cytotoxicity of the aqueous and methanol extracts and fractions of both species was studied using the brine shrimp lethality tests (BST) for the first time. Results: The results demonstrated that the lethality (LC50) for crude extracts for both plants ranged between 1.8 and 5.8 ppm and was relatively greater than that for the methanol, ethyl acetate and chloroform fractions of the extracts which ranged between 2.1 ppm and 27 ppm. This suggested that crude extracts were more potent than their respective fractions, further explaining that the different fractions of phytochemicals in these plant species work jointly (in synergy) to exert their therapeutic efficacy. Both aqueous and methanol extracts of the two medicinal plants demonstrated a high degree of antioxidant capacity against the DPPH radical with the Duh and Yen inhibition percentage ranging between 4.5% and 72%. Phytochemical studies of the rhizome extracts showed that the major compounds present include flavonoids, tannins, anthocyanidins, anthraquinones, triterpenoids (oleanolic acid), the steroidal saponin Diosgenin, the sugars, rhamnose, glucuronic acid, Arabinose and hexoses. Conclusion: This is the first report of the detection and isolation of diosgenin and oleanolic acid from the rhizome extracts of Ee and Pp. All structures were determined using spectroscopic/spectrometric techniques (1H NMR and 13C and LC-ESI-MS) and by comparison with literature data.
- Full Text:
- Date Issued: 2014
- Authors: Mpofu, Smart J , Msagati, Titus A M , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125097 , vital:35728 , https://doi.org/10.4314/ajtcam.v11i1.6
- Description: Background: Elephantorrhiza elephantina (Ee) and Pentanisia prunelloides (Pp) are two medicinal plants which are widely used to remedy various ailments including diarrhoea, dysentery, inflammation, fever, rheumatism, heartburn, tuberculosis, haemorrhoids, skin diseases, perforated peptic ulcers and sore joints in southern Africa (South Africa, Swaziland, Botswana and Zimbabwe). The following study was conducted to explore the in vitro cytotoxicity, antioxidant properties and phytochemical profile of the two medicinal plants. Materials and Methods: The cytotoxicity of the aqueous and methanol extracts and fractions of both species was studied using the brine shrimp lethality tests (BST) for the first time. Results: The results demonstrated that the lethality (LC50) for crude extracts for both plants ranged between 1.8 and 5.8 ppm and was relatively greater than that for the methanol, ethyl acetate and chloroform fractions of the extracts which ranged between 2.1 ppm and 27 ppm. This suggested that crude extracts were more potent than their respective fractions, further explaining that the different fractions of phytochemicals in these plant species work jointly (in synergy) to exert their therapeutic efficacy. Both aqueous and methanol extracts of the two medicinal plants demonstrated a high degree of antioxidant capacity against the DPPH radical with the Duh and Yen inhibition percentage ranging between 4.5% and 72%. Phytochemical studies of the rhizome extracts showed that the major compounds present include flavonoids, tannins, anthocyanidins, anthraquinones, triterpenoids (oleanolic acid), the steroidal saponin Diosgenin, the sugars, rhamnose, glucuronic acid, Arabinose and hexoses. Conclusion: This is the first report of the detection and isolation of diosgenin and oleanolic acid from the rhizome extracts of Ee and Pp. All structures were determined using spectroscopic/spectrometric techniques (1H NMR and 13C and LC-ESI-MS) and by comparison with literature data.
- Full Text:
- Date Issued: 2014
Interactive efficacies of Elephantorrhiza elephantina and Pentanisia prunelloides extracts and isolated compounds against gastrointestinal bacteria
- Mpofu, Smart J, Olivier, Denise K, Krause, Rui W M, Ndinteh, Derek T, Van Vuuren, S
- Authors: Mpofu, Smart J , Olivier, Denise K , Krause, Rui W M , Ndinteh, Derek T , Van Vuuren, S
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124122 , vital:35552 , https://doi.org/10.1016/j.sajb.2014.07.002
- Description: Elephantorrhiza elephantina (Burch.) Skeels (Fabaceae) and Pentanisia prunelloides (Klotzsch ex Eckl. & Zeyh.) Walp. (Rubiaceae) are two medicinal plants used extensively in southern Africa to treat various ailments. Often, decoctions and infusions from these two plants are used in combination specifically for stomach ailments. The antimicrobial activities of the methanol and aqueous extracts of the rhizomes of the two plants, as well as the two active ingredients from the plants [(−)-epicatechin and palmitic acid] have been determined apart and in combination against Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 8739) and Bacillus cereus (ATCC 11778). The minimum inhibitory concentration (MIC) values for the aqueous (0.50–16.00 mg/mL) and methanol (0.20–16.00 mg/mL) extracts independently demonstrated varied efficacies depending on the pathogen of study. When the two plants were combined in 1:1 ratios, synergistic to additive interactions (ΣFIC values 0.19–1.00) were noted. Efficacy for the two major compounds ranged between 0.13–0.63 mg/mL and mainly synergistic interactions were noted against E. faecalis and E. coli. The predominantly synergistic interactions noted between E. elephantina and P. prunelloides and major compounds, when tested in various ratios against these pathogens, provide some validation as to the traditional use of these two plants to treat bacterial gastrointestinal infections.
- Full Text:
- Date Issued: 2014
- Authors: Mpofu, Smart J , Olivier, Denise K , Krause, Rui W M , Ndinteh, Derek T , Van Vuuren, S
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124122 , vital:35552 , https://doi.org/10.1016/j.sajb.2014.07.002
- Description: Elephantorrhiza elephantina (Burch.) Skeels (Fabaceae) and Pentanisia prunelloides (Klotzsch ex Eckl. & Zeyh.) Walp. (Rubiaceae) are two medicinal plants used extensively in southern Africa to treat various ailments. Often, decoctions and infusions from these two plants are used in combination specifically for stomach ailments. The antimicrobial activities of the methanol and aqueous extracts of the rhizomes of the two plants, as well as the two active ingredients from the plants [(−)-epicatechin and palmitic acid] have been determined apart and in combination against Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 8739) and Bacillus cereus (ATCC 11778). The minimum inhibitory concentration (MIC) values for the aqueous (0.50–16.00 mg/mL) and methanol (0.20–16.00 mg/mL) extracts independently demonstrated varied efficacies depending on the pathogen of study. When the two plants were combined in 1:1 ratios, synergistic to additive interactions (ΣFIC values 0.19–1.00) were noted. Efficacy for the two major compounds ranged between 0.13–0.63 mg/mL and mainly synergistic interactions were noted against E. faecalis and E. coli. The predominantly synergistic interactions noted between E. elephantina and P. prunelloides and major compounds, when tested in various ratios against these pathogens, provide some validation as to the traditional use of these two plants to treat bacterial gastrointestinal infections.
- Full Text:
- Date Issued: 2014
Steam activation, characterisation and adsorption studies of activated carbon from maize tassels.
- Olorundare, O F, Msagati, Titus A, Krause, Rui W M, Okonkwo, J O, Mamba, Bhekie B
- Authors: Olorundare, O F , Msagati, Titus A , Krause, Rui W M , Okonkwo, J O , Mamba, Bhekie B
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123847 , vital:35507 , https://doi.org/10.1080/02757540.2013.877001
- Description: In this paper, steam-produced activated carbon (STAC) from maize tassel (MT) was evaluated for its ability to remove basic dye (methylene blue MB) from aqueous solution in a batch adsorption process. The equilibrium experiments were conducted in the range of 50–300 mg/L initial MB concentrations at 30°C, for effect of pH, adsorbent dosage and contact time. The experimental data were analysed by Langmuir, Freundlich and Temkin isotherm models of adsorption. Freundlich adsorption isotherm was found to have highest value of R2(R2=0.97) compared to other models of Langmuir and Temkin having (0.96 and 0.95 respectively). STAC has a high adsorptive capacity for MB dye (200 mg/g) and also showed favourable adsorption for the dye with the separation factor for the dye-activated carbon system. The kinetic data obtained were analysed using pseudo first-order kinetic equation and pseudo second-order kinetic equation. The experimental data fitted well into pseudo second-order kinetic equation, as demonstrated by the high value of R2.
- Full Text:
- Date Issued: 2014
- Authors: Olorundare, O F , Msagati, Titus A , Krause, Rui W M , Okonkwo, J O , Mamba, Bhekie B
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123847 , vital:35507 , https://doi.org/10.1080/02757540.2013.877001
- Description: In this paper, steam-produced activated carbon (STAC) from maize tassel (MT) was evaluated for its ability to remove basic dye (methylene blue MB) from aqueous solution in a batch adsorption process. The equilibrium experiments were conducted in the range of 50–300 mg/L initial MB concentrations at 30°C, for effect of pH, adsorbent dosage and contact time. The experimental data were analysed by Langmuir, Freundlich and Temkin isotherm models of adsorption. Freundlich adsorption isotherm was found to have highest value of R2(R2=0.97) compared to other models of Langmuir and Temkin having (0.96 and 0.95 respectively). STAC has a high adsorptive capacity for MB dye (200 mg/g) and also showed favourable adsorption for the dye with the separation factor for the dye-activated carbon system. The kinetic data obtained were analysed using pseudo first-order kinetic equation and pseudo second-order kinetic equation. The experimental data fitted well into pseudo second-order kinetic equation, as demonstrated by the high value of R2.
- Full Text:
- Date Issued: 2014
Synthesis and characterization of novel zinc phthalocyanines as potential photosensitizers for photodynamic therapy of cancers
- Moeno, Sharon, Ermilov, E A, Kuzyniak, W, Höpfner, M, Krause, Rui W M
- Authors: Moeno, Sharon , Ermilov, E A , Kuzyniak, W , Höpfner, M , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123673 , vital:35471 , https://doi.org/10.1039/C3PP50393C
- Description: Two novel zinc phthalocyanines (Pcs): tetramethyl tetrakis-2,(3)-[(4-methyl-2-pyridyloxy)phthalocyaninato] zinc(II) (4) and (the negatively charged form) tetrakis-2,(3)-[(3-carboxylicacid-6-sulfanylpyridine)phthalocyaninato] zinc(II) (5), water soluble by virtue of their ionic substituent groups were synthesized. The spectroscopic properties of both compounds were determined and their photodynamic activities were investigated in a human tumor cell model. In aqueous media the two peripherally substituted water soluble Pcs are highly aggregated. The phototoxic activity of the two novel Pcs (Pc 4 and Pc 5; 0–20 μM) was shown to be time- and dose-dependent in human pancreatic carcinoid BON cells, leading to a reduction of tumor cells of >80% compared to the controls. The effectiveness of the treatment appeared to be attenuated by the aggregation of Pcs under aqueous conditions. Interestingly, even those cells that were not immediately killed by the photoactivated photosensitizer seemed to be affected by the Pc photodynamic activity, as a single PDT induced long-lasting effects on cell survival. Even 4 days after PDT, the number of surviving cells did not re-increase or still dropped, as compared to control cells. The underlying mechanism of this observation has to be deciphered in future investigations.
- Full Text:
- Date Issued: 2014
- Authors: Moeno, Sharon , Ermilov, E A , Kuzyniak, W , Höpfner, M , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123673 , vital:35471 , https://doi.org/10.1039/C3PP50393C
- Description: Two novel zinc phthalocyanines (Pcs): tetramethyl tetrakis-2,(3)-[(4-methyl-2-pyridyloxy)phthalocyaninato] zinc(II) (4) and (the negatively charged form) tetrakis-2,(3)-[(3-carboxylicacid-6-sulfanylpyridine)phthalocyaninato] zinc(II) (5), water soluble by virtue of their ionic substituent groups were synthesized. The spectroscopic properties of both compounds were determined and their photodynamic activities were investigated in a human tumor cell model. In aqueous media the two peripherally substituted water soluble Pcs are highly aggregated. The phototoxic activity of the two novel Pcs (Pc 4 and Pc 5; 0–20 μM) was shown to be time- and dose-dependent in human pancreatic carcinoid BON cells, leading to a reduction of tumor cells of >80% compared to the controls. The effectiveness of the treatment appeared to be attenuated by the aggregation of Pcs under aqueous conditions. Interestingly, even those cells that were not immediately killed by the photoactivated photosensitizer seemed to be affected by the Pc photodynamic activity, as a single PDT induced long-lasting effects on cell survival. Even 4 days after PDT, the number of surviving cells did not re-increase or still dropped, as compared to control cells. The underlying mechanism of this observation has to be deciphered in future investigations.
- Full Text:
- Date Issued: 2014
- «
- ‹
- 1
- ›
- »