Showing papers by "Bhekie B. Mamba published in 2011"

Nitrogen/Palladium-Codoped TiO2 for Efficient Visible Light Photocatalytic Dye Degradation

Abstract: Elimination of toxic organic compounds from wastewater is currently one of the most important subjects in water pollution control. Eosin Yellow, an anionic xanthene fluorescent dye, known to be carcinogenic, originates mainly from textile industrial processes and is resistant to conventional chemical or biological water treatment methods. Photocatalysis using non metal/platinum group metal-codoped TiO2 may provide effective means of removing such dyes from contaminated water. In this study, nitrogen/palladium-codoped TiO2 photocatalysts were prepared by calcination of the hydrolysis product of titanium isopropoxide, Ti(OC3H7)4, with aqueous ammonia. Samples were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), diffuse reflectance UV–vis spectrophotometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Anatase phase particles of size range 1...

Household water treatment systems: A solution to the production of safe drinking water by the low-income communities of Southern Africa

Abstract: One of the United Nations Millennium Development Goals is to reduce to half by 2015 the number of people, worldwide, who lack access to safe water. Due to the numerous deaths and illnesses caused by waterborne pathogens, various household water treatment devices and safe storage technologies have been developed to treat and manage water at the household level. The new approaches that are continually being examined need to be durable, lower in overall cost and more effective in the removal of the contaminants. In this study, an extensive literature survey was conducted to regroup various household treatment devices that are suitable for the inexpensive treatment of water on a household basis. The survey has resulted in the selection of four household treatment devices: the biosand filter (BSF), bucket filter (BF), ceramic candle filter (CCF) and the silver-impregnated porous pot filter (SIPP). The first three filters were manufactured in a Tshwane University of Technology workshop, using modified designs reported in literature. The SIPP filter is a product of the Tshwane University of Technology. The performance of the four filters was evaluated in terms of flow rate, physicochemical contaminant (turbidity, fluorides, phosphates, chlorophyll a, magnesium, calcium and nitrates) and microbial contaminant (Escherichia coli, Vibrio cholerae, Salmonella typhimurium, Shigella dysenteriae) removals. The flow rates obtained during the study period were within the recommended limits (171 l/h, 167 l/h, 6.4 l/h and 3.5 l/h for the BSF, BF, CCF and SIPP, respectively). Using standard methods, the results of the preliminary laboratory and field studies with spiked and environmental water samples indicated that all filters decreased the concentrations of contaminants in test water sources. The most efficiently removed chemical contaminant in spiked water was fluoride (99.9%) and the poorest removal efficiency was noted for magnesium (26–56%). A higher performance in chemical contaminant removal was noted with the BF. For pathogenic bacteria, the mean percentage removals ranged between 97% and 100%. Although the concentrations of most chemical parameters were within the recommended limits in raw surface water, poor removal efficiencies were recorded for all filters, with the poorest reduction noted with fluorides (16–48%). The average turbidity removals from surface water ranged between 90% and 95% for all filters. The highest bacterial removal efficiency was recorded by the SIPP (99–100%) and the lowest by the BF (20–45%) and the BSF (20–60%). Extensive experimental studies with various types of raw surface water will still determine the long-term performance of each filter, as well as the filters that can be recommended to the communities for household treatment of drinking water.

Preparation, characterization, and application of polypropylene-clinoptilolite composites for the selective adsorption of lead from aqueous media.

Abstract: A polymer composite of polypropylene (PP) and clinoptilolite (CLI) for the adsorption of lead has been prepared using the melt-mixing compounding technique in a rheomixer. Characterization of the composite was performed using scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), X-ray diffraction (XRD), Brunuer–Emmett–Teller (BET), and Fourier transform infrared spectroscopy (FTIR). The influence of contact time, pH, initial metal-ion concentration, temperature, and pretreatment on the adsorption of lead (Pb) by the PP–CLI composite was investigated. Optimum pH was found to be between pH 6 and pH 8 while the maximum sorption of lead at optimal pH was 95%. No difference was observed between the adsorption behavior of composites functionalized with 20% and 30% clinoptilolite, respectively, while the pretreatment with HCl and NaCl made a slight difference to the adsorption capacity of composites. The findings from this study on the lead adsorption behavior of CLI–PP composite may have potential applications in wastewater and water purification works.

Electrochemical detection and removal of lead in water using poly(propylene imine) modified re-compressed exfoliated graphite electrodes

Abstract: Modification of exfoliated graphite (EG) electrode with generation 2 poly(propylene imine) dendrimer by electrodeposition resulted in an electrochemical sensor which was used to detect lead ions in water to a limit of 1 ppb and a linear response between 2.5 and 40 ppb using square wave anodic stripping voltammetry (SW-ASV). Pb(II) was also removed from spiked water sample using a 40-mm diameter unmodified EG electrode with an applied potential of −1,000 mV for 180 min. A removal efficiency of 99% was calculated from a 150 mL sample. The results obtained in both cases using SW-ASV, correlated with atomic absorption spectroscopy.

Fluorescent Sensing of Chlorophenols in Water Using an Azo Dye Modified β-Cyclodextrin Polymer

Abstract: A water soluble azo dye modified β-cyclodextrin polymer 4 was synthesized and used as a chemosensor for the detection of chlorinated phenols, model chlorinated by-products (CBPs) of water treatment for drinking purposes. The characterization of the intermediates and the azo dye modified β-CD polymer was done by UV/Vis Spectrophotometry, FT-IR and 1H-NMR spectroscopies. The chlorophenols were capable of quenching the fluorescence of the polymer. The polymer showed greater sensitivity towards 2,4-dichlorophenol, with a sensitivity factor of 0.35 compared to 0.05 and 0.12 for phenol and 4-chlorophenol, respectively. The stability constants (Ks) of the pollutants were also determined by the Benesi-Hildebrand method to be 2.104 × 103 M−1 for 2,4-dichlorophenol and 1.120 × 102 M−1 for 4-chlorophenol.

The potential of melt-mixed polypropylene-zeolite blends in the removal of heavy metals from aqueous media

Abstract: The continued deterioration of the water quality in natural water sources such as rivers and lakes has led to tensions amongst relevant stakeholders to such an extent that cooperative water resource management is being regarded as an ideal solution to culminate conflicts and maximise the benefits. The desire to develop technologies that combine the three most important aspects of integrated water resource management (namely social, economic and environmental) has been encouraged by relevant authorities. This paper therefore reports the application of clinoptilolite–polypropylene (CLI–PP) blends/composites for the removal of lead from aqueous media. Just like many other heavy metals, lead poses a threat to water and soil quality as well as to plant and animal health. The findings on the adsorption behaviour of clinoptilolite–polypropylene composites with respect to Pb2+ are also reported here, with the aim of extending its application to wastewater and environmental water purification. The batch equilibrium adsorption method was employed and the influence of contact time, pH, initial metal-ion concentration, temperature and pretreatment was determined. The optimum pH was found to be between pH 6 and pH 8 while the maximum sorption of lead at optimal pH was 95%. No big difference was observed between the adsorption behaviour of composites functionalised with 20% and 30% clinoptilolite, respectively. The pretreatment with HCl and NaCl made a slight difference to the adsorption capacity of composites.

Ethylene Vinyl Acetate and Polycaprolactone–Organoclay Nanocomposite: Thermal, Mechanical and Morphological Properties

Abstract: Organoclay of the type Cloisite® 20A (C-20A) with two structurally different but semicrystalline polymer matrices was studied. Polycaprolactone (PCL), a linear, biodegradable polymer, and ethylene vinyl acetate (EVA), a branched copolymer, were chosen to prepare polymer clay nanocomposites via the melt-blending method. The results show that the structure of a polymer matrix plays a significant role towards compatibilization with the silicate layers of the clay. Scanning electron microscopy and X-ray diffraction analyses revealed an exfoliated-intercalated mixed morphology for the PCL matrix. However, for the EVA matrix, silicate layers agglomerated to form tactoids and resulted primarily in an intercalated morphology. Fourier transform infrared spectroscopy was used to determine the nature of the interactions between the polymer and the filler. The thermal properties were investigated using thermogravimetric analysis and indicated that, with an increase in clay loading, the thermal stability was reduced for both matrices. Tensile tests suggested that Young’s modulus improved for the EVA matrix with an increase in clay dosage whereas for PCL the modulus was found to be highest for 8% clay loading.

Comparative studies of the morphological and thermal properties of clay/polymer nanocomposites synthesized via melt blending and modified solution blending methods

Abstract: In this study, EVA/clay nanocomposites were prepared by two different methodologies i.e. melt blend technique and solution blend technique. Comparative analyzes of morphological and thermal properties of the nanocomposites fabricated by two different methods were done. The modified solution method was found to be an efficient method to obtain nanocomposite strips with uniform dispersion of the clay at organoclay loading of 8% and crystallinity by extrusion. The melt blending method produced nanocomposites with high porosity, intercalation, and thermal stability, whereas solution blending technique resulted in composites with more intercalated-exfoliated morphology, and less porosity and thermal stability.

Nitrite Electrochemical Sensor Based on Prussian Blue /Single- Walled Carbon Nanotubes Modified Pyrolytic Graphite Electrode.

Abstract: Nitrite, NO2 - (in neutral), and NO (in acidic media) were used as analytical probe to investigate the electrocatalytic properties of Prussian blue nanoparticles (PB) modified edge plane pyrolytic graphite (EPPG) electrode. Results indicate that single-walled carbon nanotubes-Prussian blue hybrid (SWCNT-PB) modified electrode demonstrated greater sensitivity and catalysis towards nitrite compared to PB or a SWCNT modified electrode. The current response of the electrode was reduced in the presence of cetyltrimethylammoniumbromide (CTAB) which was used as a stabilising agent. Electrocatalytic oxidation of nitrite occurred through a simple adsorption controlled electrode reaction. The adsorption equilibrium constant β and the standard free energy change ΔG 0 due to adsorption were 4.35 x 10 3 M -1 s -1 (-20.76 kJmol -1 ) and 15.0 x 10 4 M -1 s -1 (-29.53 kJmol -1 ) for nitrite and nitric oxide respectively. Despite the adsorption, the EPPGE-SWCNT-PB electrode showed good stability of greater than 80% in the analytes. The electrode’s limit of detection and catalytic rate constant were 6.26 µM (4.37 x 10 6 cm 3 mol -1 s -1 ) and 4.9 µM (6.35 x 10 5 cm 3 mol -1 s -1 ) for nitrite and nitric oxide respectively. The fabricated electrode is not difficult to prepare and could serve as a potential sensor for nitrite determination in food and environmental samples.

A simplified cost-effective biosand filter (BSFZ) for removal of chemical contaminants from water

Abstract: A study aimed at designing, constructing and evaluating a cost-effective biosand filter was undertaken. The biosand filter was modified with the addition of zeolites (clinoptilolite). The zeolites formed the largest part of the filter media which comprised of four layers. The complete filter had six zones which played a role during the filtration process. Filtration was done for 3 h to mimic water filtration in private homes. The filtered water was collected in a vessel for 1 h after which the samples were taken for analysis. Results indicated removal of up to 80 calcium, 89 magnesium, 99 iron, 56 arsenic, 54 fluorides, 96 turbidity, 37 nitrates and 41% total organic carbon. Higher turbidity (r = 0.024) and chlorophyll a (r = 0.566) concentrations resulted in a decrease in the flow rate of the filter which was between 1.74 l/h and 19.20 l/h. Higher chlorophyll a concentrations resulted in higher turbidity (r = 0.609). The filter was costeffective (

Treatability and characterization of Natural Organic Matter (NOM) in South African waters using newly developed methods

Abstract: Managing the removal of Natural Organic Matter (NOM) or problematic components from water has become increasingly important. NOM is a heterogeneous mixture of organic compounds of human origin and derived from plant and microbial residues. The inadequate removal of NOM has a bearing on the capacity of the other treatment processes to remove organic micro-pollutants or inorganic species that may be present in the water. In addition the action of certain disinfection processes has been shown to lead to the formation of harmful disinfection by-products (DBPs). Owing to the complexity, in composition and structure, of NOM, the techniques currently employed for its characterization have a number of limitations, both in terms of quantification and removal of the NOM within short periods of time. The dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC) and Fluorescence Emission Excitation Matrices (FEEM) were used to characterize NOM from various water samples collected around South Africa. Characterization results gave an indication of the character of NOM present in all the water samples. FEEM and UV–Vis results indicated that most of the water samples were aromatic in nature, since they had high hydrophobic and humic acid-like materials content. Generally, the characterization data indicated a varying composition of NOM amongst the various sampling points. The polarity rapid assessment method (PRAM) was then employed as a rapid NOM characterization tool. The characterization under PRAM is based on preferential adsorption of dissolved organic matter (DOM) fractions onto solid phase extraction (SPE) sorbents. The PRAM also allows the separation of DOM into fractions by polarity, hence reducing the molecular heterogeneity of NOM and thus aiding the removal of specific NOM fractions from water. The PRAM provided a quick characterization of the NOM character. However, DOC quantification by the PRAM analysis was hindered by excessive carbon leaching from the SPE cartridges. The BDOC method of analysis is based on the bacteria fixed on the biologically active sand and gives a ratio of the biodegradable NOM versus the non-biodegradable NOM. For the BDOC analysis, the percentage DOC removal for the samples ranged from 12% to 61%.

Copper and silver impregnated carbon nanotubes incorporated into cyclodextrin polyurethanes for the removal of bacterial and organic pollutants in water

Abstract: Increasing demand for safe drinking water and the problems associated with some existing water treatment methods have made it vital for the development of new technologies to address these challenges. This study explores the use of nanosized silver and copper impregnated on polyurethanes for possible use in water disinfection. It also investigates the adsorption of organics by the metal impregnated polyurethanes in water. Copper and silver nanoparticles were immobilized on carbon nanotube and embedded in water-insoluble cyclodextrin polyurethane polymers. The polyurethanes were characterized by various techniques such as BET, TEM, SEM and EDX and evaluated for their adsorption and bacteria reduction capacity using spiked water samples containing bacteria (Escherichia coli and Salmonella typhi) and a model organic pollutant (para-nitrophenol) in water. The metal impregnated polyurethanes inactivated up to 3 logs of bacteria but had a maximum adsorption of 55% of the model organic pollutant.

Development of supported liquid membrane techniques for the monitoring of trace levels of organic pollutants in wastewaters and water purification systems

Abstract: The supported liquid membrane (SLM) extraction technique has been developed and successfully used for the monitoring of trace quantities of ionisable organic contaminants, including 17β-estradiol and its metabolites, testosterones and their methyl ester derivatives, benzimidazole anthelmintic antibiotics and sulphonamides in aquatic systems. A number of parameters which control the mass transfer in the supported liquid membrane extraction process such as donor and acceptor pH, extraction time and the type of organic liquid membrane were optimised to enhance the efficiency of the liquid membrane in the removal of these compounds. The method developed gave very low detection limits (0.3 ng/l to 2.4 ng/l for 17β-estradiol and its metabolites; between 1 μg/l and 20 μg/l for sulphonamides; and between 0.1 ng/l and 10 ng/l for benzimidazole anthelmintic compounds). The SLM method showed good linearity, reproducibility and repeatability values and is therefore suitable for routine monitoring of such compounds in water and wastewater systems.

Supercapacitive Properties of Symmetry and the Asymmetry Two Electrode Coin Type Supercapacitor Cells Made from MWCNTS/Nickel Oxide Nanocomposite

Abstract: 1 October 2011 Supercapacitive properties of synthesised nickel oxides (NiO) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in a two-electrode coin cell type supercapacitor were investigated. Successful formation of the MWCNT-NiO nanocomposite was confirmed with techniques such as transmission electron microscopy (TEM), scan electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The supercapacitance behaviour of both the symmetry and the asymmetry MWCNT-NiO based supercapacitor in 1 M H

The adsorption behavior of Cu(II), Pb(II), and Co(II) of ethylene vinyl acetate-clinoptilolite nanocomposites

Abstract: In this study, ethylene vinyl acetate (EVA) was mixed with clinoptilolite (C), a natural zeolite, to prepare EVA-C nanocomposites. The films were characterized by SEM-EDS, XRD, and FT-IR, and heavy metal removal was studied using the batch technique. The effects of the initial pH value and concentration of solutions, contact time, and filler dosage on the adsorption capacity of the composites were investigated. To study the influence of pretreatment on the filler, clinoptilolite was activated using KCl, NaCl, and HCl. Adsorption results show that equilibrium was reached after 24 h, and that sorption reached its maximum at pH values between 5 and 7. The selectivity trend was observed to be Pb > Cu > Co, which was consistent for both single and mixed metal-ion solutions. Pretreatment significantly increased adsorption capacity of the composite, but was dependent on the conditioning reagent. Nanocomposites filled with HCl-activated particles demonstrated a high adsorption capacity of between 70 and 80% for all three metals, while KCl-activated particles were the least efficient with a maximum adsorption capacity of 69% for Pb(II), 54% for Cu(II) and 48% for Co(II). The adsorption data were then fitted to both Langmuir and Freundlich isotherms over the entire concentration range, and the Langmuir isotherm showed a better fit of the experimental sorption data than the Freundlich isotherm. The results obtained show that this simple methodology which can be up-scaled has great potential for the preparation of a wide variety of similar particle-filled adsorbent nanocomposites in other environmental remediation applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

UV/visible spectroscopic analysis of CO3+ and CO2+ during the dissolution of cobalt from mixed Co-Cu oxidized ores

Abstract: The leaching of cobalt from four-mixed Co-Cu oxidized ores containing cobalt at levels ranging from 0.5wt% to 34wt% was studied and the results has been reported. Conventional dissolution of these oxidized Co-Cu ores with diluted H2SO4 and SO2 as a reducing agent resulted in a substantial improvement in the solution based recovery of cobalt. UV/visible spectroscopic analysis of the leached solutions indicated that the increased cobalt content in the solution was a result of flushing the acidified cobalt leaching solution with SO2. Furthermore, UV/visible spectroscopy confirmed that as SO2 was flushed into the acidified leaching solution, Co3+ bearing minerals were reduced to the readily soluble Co2+ bearing minerals, and this resulted in the increase of total cobalt in the collected solution. The mechanism of the reduction of Co3+ to Co2+ bearing minerals when SO2 is flushed during the leaching of mixed Co-Cu oxidized ores, including the stability trends of Co3+, Co2+, and Cu2+ complexes, as shown by their UV/visible spectra, are also discussed.

Imidazolium ionic liquids as dissolving solvents for chemical-grade cellulose in the determination of fatty acids using gas chromatography-mass spectrometry

Abstract: A quick, simple, and environmentally friendly sample preparation method for fatty acids analysis from chemical-grade cellulose was developed employing imidazolium based ionic liquids as solvents. A variety of imidazolium based ionic liquids were screened for their ability to dissolve chemical cellulose at different temperatures. Dissolution of chemical cellulose was observed to be dependent on the ionic liquids’ anions as well as temperature. The effect of ionic liquids on chemical cellulose was examined using FT-IR and TGA techniques, which showed no difference between the original and the regenerated cellulose except for the percentage mass residues in TGA profile which was high for regenerated cellulose, 15% compared to 8% of the original at 600 °C. Fatty acids extracted from cellulose were found to be predominant in the samples from different bleaching stages, with high levels in the oxygen delignification and low levels were observed in hypochlorite bleached samples. The number and levels of the identified fatty acids were observed to decrease with the bleaching sequence. The recoveries obtained using this method ranged from 90 to 107%.

Morphological, transport, and adsorption properties of ethylene vinyl acetate/polyurethane/bentonite clay composites

Abstract: The effect of polyurethane (PU) foam on the morphological and transport properties of ethylene vinyl acetate (EVA) with 9% vinyl acetate and the potential application of 3%bentonite/28.5% PU/68.5% EVA composites fabricated via the melt-blending method in heavy-metal extraction from water systems were investigated. EVA did not swell in water, whereas the PU/EVA blend attained a maximum percentage of deionized water uptake of 2.158 mol %. A 3% bentonite/28.5% PU/68.5% EVA composite blend successfully removed 90% of Pb2+ from an aqueous solution with an initial concentration of 30 mg/L, whereas 3% bentonite/97% EVA could only extract 7.323% of Pb2+ ions. Pb2+ adsorption was found to obey the Langmuir adsorption isotherm and pseudo-second-order kinetic model. Thermodynamic studies demonstrated that the adsorption was favorable at room temperature and the uptake of Pb2+ was mostly by physical adsorption, as also indicated by the value n = 2.449 (where n is an empirical parameter indicating transport mode) from the Freundlich adsorption isotherm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Polymerization of cyclodextrin-ionic liquid complexes for the removal of organic and inorganic contaminants from water

Abstract: The removal of toxic contaminants from water still remains a huge challenge for water supplying companies and municipalities. Both organic and inorganic (mostly heavy metal) pollutants are often present in water distribution networks as a result of agricultural, domestic and industrial operations. To remove these pollutants from water distribution networks, effective techniques need to be developed. In our laboratories, research that involves the use of polymers of cone-shaped cyclodextrins (CDs) interconnected by linkers has been successfully demonstrated in the removal of organic pollutants from water. We have now undertaken a programme whereby polymers possessing moieties capable of removing both organic and inorganic contaminants from water, the so-called multifunctional complexes will be synthesised. To access these multifunctional complexes, CDs were attached to salts of organic cations (i.e. imidazolium and pyridinium) in a manner similar to the formation of ionic liquids (ILs). These cyclodextrin-ionic liquid (CD-IL) derivatives were then polymerised with bifunctional linkers with the expectation that the resulting polymers will be able to perform the dual role of removing a wide range of both organic and inorganic pollutants from water. Pollutants from many industries often end up in water systems; other pollutants emanate from domestic and agricultural run-offs. Organic pollutants such as organic solvents, pesticides, fungicides and inorganic pollutants such as nitrates, cyanides and dissolved gases are present in many water systems (Schwarzenbach et al, 2003). When these pollutants are introduced into the environment, they are subjected to physical, chemical and biological processes, leading in the generation of derivatives possessing different environmental behaviour and effects (Schwarzenbach et al, 2003). These contaminants may leach into the soil and contaminate ground water. They also tend to bioaccumulate in the bodies of organisms. The small size and chemical inertness (or unreactiveness) of these pollutants make their removal from water using the current water treatment methods difficult (Li and Ma, 1999). Also, they have health effects such as kidney and liver damage, the destruction of nerve and circulatory systems and other psychological effects detrimental to human health. Since communities need ultra pure water, there is a need to remove pollutants even at very low concentrations to ensure the health and safety of water users.

Effect of metal poisoning and the implications of gender and age on the elemental composition in patients with mental behavioural disorders

Abstract: The objective of this work was to investigate the possible correlation between the exposure to selected toxic metals and the behavioural disorder of mentally ill patients. The study also sought to establish if gender and age of the patient had an effect on the pattern of the elemental distribution in their head hair and blood samples. To achieve this, the concentrations of a number of selected toxic metal elements were determined in 60 mentally ill patients and 43 healthy individuals (control) in Ile-Ife area, in Nigeria, using inductively coupled plasma spectrophotometer-optical emission spectrometer (ICP-OES). The behavioural disorder cases investigated were 8 bipolar, 2 post partum psychosis, 43 schizophrenia and 7 non-specific cases. The concentration ranges of Cu, Zn, Ca, Li, V, Be (for both males and females), Cd and Sr (for females only) as analyzed from the patients’ head hair with behavioural disorders, were found to be similar with those of the controls. However, the concentration ranges of Al, Ba, Mg, Cr and Cd, Sr (for males only) were higher in patients than in the controls, while those for K and Fe were found to be higher in the controls than in the patients for both males and females. Blood samples analysis showed that, nearly all the elements were higher in the female (patients and control) than in the males; a possible indication that women may be at greater risk than men. It was also shown that, age may have an influence on the accumulation of some specific elements. The accuracy of the analytical results was experimentally demonstrated by NCS DC 73347 certified reference material that was analyzed along the standards while the significance of the data obtained was tested statistically at both p = 0.01 and 0.05. Key words: Toxic metals, behavioural disorder, gender, age, inductively coupled plasma-optical emission spectrometer.

Measurements of distribution coefficients and lipophilicity values for oleanolic acid and betulinic acid extracted from indigenous plants by hollow fibre supported liquid membrane

Abstract: Hollow fibre supported liquid membrane (HFSLM) has been applied in the measurements of distribution constants, K D and lipophilicity (log P) values for the isomeric triterpenic acids, betulinic acid (BA) and oleanolic acid (OA) isolated from indigenous plants. The results have shown that BA had an optimum pH of 3.5 while the optimum sample pH for OA was ranging from 0.5 to 2.5. The log P values obtained for BA and OA were 6.61 and 6.12, respectively. The K D value obtained for BA was 0.29 while that for OA 0.16. The method has advantages of simplicity, use of minimal organic solvents and the ability to selectively extract only one isomer (OA) in the mixture with BA by optimizing pH conditions. KEY WORDS : Betulinic acid, Oleanolic acid, Hollow fibre supported liquid membrane, Distribution coefficient, Lipophilicity Bull. Chem. Soc. Ethiop. 2011 , 25(3), 321-332.

Synthesis, characterization, and in vitro antibacterial and antifungal studies of tin(IV) thiohydrazide complexes

Abstract: Reaction of tin dichloride and tin tetrachloride with cyclohexylamine-N-thiohydrazide (ChaThz) [L1] and 1,3-propanediamine-N-thiohydrazide (PdaThz) [L2] results in [Sn(ChaThz)2] (1), Sn(ChaThz)2Cl2] (2), [Sn(PdaThz)2] (3), and [Sn(PdaThz)2Cl2] (4), in which the thiohydrazide coordinates to tin through imine nitrogen and thioamide sulfur. The ratio metal : ligand was 1 : 2 for all complexes. The tin(IV) thiohydrazide complexes were characterized by elemental analysis, IR, UV-Vis, 1H-NMR, 119Sn NMR, and mass spectral studies. Using the disc diffusion method, the ligands and metal complexes were screened for in vitro antibacterial activities against four pathogenic bacteria, Escherichia coli, Staphylococcus aureus, P. aeruginosa, and Bacillus cereus and for antifungal activities against Aspergillus flavus, A. carbonarius, A. niger, and A. fumigatus. While the tin(IV) complexes exhibited moderate antifungal activities, their parent ligands showed much higher and long-lasting broad spectrum of bioactivity agai...

Natural organic matter (nom) in south african waters: characterization and method development for effective nom removal

Abstract: The removal of natural organic matter (NOM) from water is becoming increasingly important in order to prevent the formation of carcinogenic disinfection by-products (DBPs). The inadequate removal of NOM has a bearing on the capacity of the other treatment processes to remove organic micro-pollutants or inorganic species that may be present in the water. In order to effectively study the nature of the South African water sources in terms of their NOM composition, water samples were collected from drinking water treatment plants in the five geographic water regions of South Africa. A raw water sample, an intermediate sample taken before sand filtration and a final sample after sand filtration were collected three times from these water treatment plants at two-month intervals and over three different seasons. The fluorescence excitation-emission matrices (FEEM), biodegradable dissolved organic carbon (BDOC), ultraviolet (UV) characterisation (200 nm to 900 nm) and dissolved organic carbon (DOC) analyses were used to characterise the NOM in the water samples. The FEEM and UV results revealed that the samples were composed mainly of non-humic substances with low UV-254 absorbance, while some samples had high humic substances with high UV254 values. The samples’ DOC results were within the range of 3.25 mg/l to 21.44 mg/l carbon, which was indicative of the varying nature of the NOM composition in the regions where samples were collected. The BDOC fraction of the NOM, on the other hand, ranged from 20% to 65%, depending on the geographical location of the sampling site.

Determination of persistent cyclic organochlorine residues in sediment slurry by microporous membrane liquid-liquid extraction and gas chromatography-mass spectrometry

Abstract: A method, using microporous membrane liquid-liquid extraction technique (MMLLE) and gas chromatography with an electron capture detector (GC-ECD) and gas chromatograph coupled to a mass spectrometer, was developed for the analysis of cyclic organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in sediment slurry. The MMLLE extraction employed isooctane as the organic liquid that was immobilised in the hollow fibre pores and in the lumen, at optimal sample pH value of 2.0 for OCPs and 7 for PCBs. The effect of triton x-100, in enhancing the dissolution of the compounds from sediment, was found to be optimal at a value of 0.15%, while the ionic strength was optimal at a value of 0.01 M. Samples from coastlines along the Indian Ocean in the southern parts of South Africa were found to be contaminated with cis and trans chlordane at concentrations of up to 0.003 mg/kg, while samples from northern parts were contaminated with 2,2’,4’,4-tetrachloro-1,1’biphenyl at concentrations of up to 0.02 mg/kg. Keywords: Organochlorine pesticides, polychlorinated biphenyls, hollow fibre liquid phase micro-extraction, high performance liquid chromatography, mass spectrometry