Theses and Dissertations (Chemistry)

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Determination of volatile organic compounds in ambient air by using thermal desorber, sorbent tubes, canister and GC-MS
(2009-06) Mkhwanazi, Sipho Sydney; Naidoo, E. B.; Niemandt, M. J.
The dissertation deals with volatile organic compounds that evaporate from the water-oil separate in the refinery, which causes bad odour around the neighbouring communities, the existence of these compounds are being identified and quantified in different seasons for the year. VOC are emitted whenever wastewater is exposed to the atmosphere. As such, emission points include open drains ditches, manhole sewer outfalls and surface fore bays, separators and treatment ponds. Refinery units such as reactors, fractionators are periodically shutdown and emptied for internal inspection and maintenance. The amount of VOC entering the wastewater is not monitored. The effluent water discharged from the refinery is not checked for the amount ofVOC present. The monitoring of the amount of VOC in wastewater stream may lead to a decrease in the emission. From the quantified results at different season, the summer session has the highest VOC emission due to the heat that causes more vapours. The preparation of a method for determination of VOC's in air presents many difficulties, because of their high volatilities and low concentrations in air. As well, the results of determination are affected by the properties of the sorbent used, mainly its sorption capacity, depending on the properties of the compound under determination. The methods for sampling and analytical procedures for the measurements of volatile organic compounds that are hazardous to air pollution are compendium method T0-14 and sorbent tube method compendium T0-17. Both methods (sorbent tube and canister) differ from each other in their extraction and detection techniques. The well suitable method for the VOC determination is canister method; this method gives more representative sample of the ambient monitoring of 24 hours, where as sorbent tube can do for 2 hours only. The canister method is more advantages due to the sample that will be still remaining for further analyses or re-check. The integrity of API water-oil separator has been improved to cause less evaporation during high temperature season. As the temperature drops from season to season, the VOC also comes down as its being seen in this study that on the winter results that all the VOC were below 90 1-lg/kg.
Reduction of ferric and ferrous compounds in the presence of graphite using mechanical alloying
(Vaal University of Technology, 2011-05) Moloto, Ledwaba Harry; Manzini, Dr. S. S.; Dikio, Dr. E. D.
Many oxidic iron compounds—iron oxides; oxy-hydroxides and hydroxides—not only play an important role in a variety of disciplines but also serve as a model system of reduction and catalytic reactions. There are more than 16 identifiable oxidic iron compounds. The reduction of these compounds has been investigated for centuries. Despite this, the reduction behavior of the oxides is not fully understood as yet. To date the reduction mechanism is still plagued with uncertainties and conflicting theories, partly due to the complex nature of these oxides and intermediates formed during the reduction. Thermodynamically, the reduction of iron oxide occurs in steps. For example, during the reduction of hematite (a-Fe2O3) magnetite (Fe3O4) is first formed followed by non-stoichiometric wüstite (Fe1-yO) and lastly metallic iron (a-Fe). The rate of transformation depends on the reduction conditions. Further, this reduction is accompanied by changes in the crystal structure. The reduction behavior of iron oxides using graphite under ball-milling conditions was investigated using Planetary mono mill (Fritsch Pulverisette 6), Mössbauer Spectroscopy (MS), X-ray Diffraction (XRD), Scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM). It was found that hematite transformed into magnetite, Wüstite and or cementite depending on the milling conditions. The study shows that by increasing the milling time, the rotational speed and / or the ball to powder ratio, the extent of the conversion of hematite to its reduction products increased. Further investigations are required for the elucidation of the reduction mechanism. The reaction og magnetite and graphite at different milling conditions lead to the formation of Fe2+ and Fe3+ species, the former increasing at the expense of Fe3O4. Fe3O4 completely disappeared after a BPR of 50:1 and beyond. The Fe2+ species was confirmed to be due to FeO using XRD analysis. HRSEM images Fe2O3 using scanning electron microscopy prior to and after milling at different times showed significant changes while the milling period was increased, HRSEM images showed that the once well defined hematite particles took ill-defined shapes and also became smaller in size, which was a results of the milling action that induced reaction between the two powders to form magnetite. EDX spectra at different milling times also confirmed formation of magnetite. EDX elemental analysis and quantification confirmed the elemental composition of starting material consisting mainly of iron. Similarly, HRSEM images of Fe3O4 using Scanning electron microscopy (SEM) prior to and after milling at different BPR showed significant changes when the milling period was increased. EDX spectra at different milling times also confirmed formation of partial FeO and EDX elemental analysis and quantification confirmed the elemental composition of starting material consisting mainly of iron than Fe2O3. TEM images of both Fe2O3 and Fe3O4 particles at different milling conditions displayed observable particle damages as a function of milling period.The once well - defined particles (Fe2O3 and Fe3O4 ) successively took ill – defined shapes, possibly accompanied by crystallite size reduction. MAS showed that the reactive milling of α- Fe2O3 and C resulted in reduction to Fe3O4 , FeO and or cementite depending on the milling conditions etc Time, milling speed and BPR variation which influenced the reduction. The study shows that by increasing the milling time, the rotational speed and / or the ball to powder ratio, the extent of the conversion of hematite to its reduction products increased. XRD study investigations even though were unable to detect spm species (Fe2+ and Fe3+ ) which has smaller crystallites below detection limits ,the variation in time showed an increment in the magnetite peaks accompanied by recession of hematite and graphite peaks as the milling time was increased which relates to the MAS observation.XRD also corroborated the data obtained from MAS that showed that the main constituent was magnetite and further evidence in support of the reduction of hematite to magnetite under reactive milling was obtained using XRD . Overall, the work demonstrated selective reduction of Fe2O3 to Fe3O4 and Fe3O4 to FeO by fine tuning the milling conditions. It is envisaged that the reduction of FeO to Fe and possible carburization to FexC could also be achieved.
Separation and recovery of selected transition-metal catalyst systems using membrane processes
(2011-06-06) Xaba, Bongani Michael; Modise, S. J.; Naidoo, E. B.
Membrane separation processes offer a promising alternative to energy-intensive separation processes such as distillation and solvent extraction. NF and RO are among the most investigated membrane processes with a potential use in the chemical industry. Carbon-carbon coupling reactions feature in the top ten most used reactions in the chemical industry. These reactions often use homogeneous palladium, nickel and other precious catalysts which are often difficult to separate from reaction products. This leads to potential product contamination and loss of active catalysts. This not only poses a threat to the environment but is also costly to the chemical industry. The purpose of this study was to investigate the efficiency of the recovery of the metal catalysts by selected membrane processes. Four commercial polymeric NF and RO membranes (NF90, NF270, BW30 and XLE) were selected for the study. Palladium catalysts commonly used in Heck and Suzuki coupling reactions were selected. These are Pd(OAc)2, Pd(OAc)2(PPh3)2, PdCl2 and Pd(PPh3)2Cl2. A range of organic solvents were also selected for the study. All the membranes were characterized for pure water permeability, pure solvent permeability, swelling, surface morphology and chemical structure. The chemical and catalytic properties of the catalysts were determined. Catalytic activity was investigated by performing coupling reactions. These catalysts generally performed well in the Heck coupling reaction with sufficient yields realized. The catalysts showed poor activities in the Suzuki and Sonogashira coupling reactions. These coupling reaction systems were affected by rapid palladium black formation. vi Catalyst retention studies showed the influence of membrane-solute interactions such as steric hindrance and size exclusion. The larger catalyst, Pd(OAc)2(PPh3)2 was rejected better by all the membranes irrespective of the solvent used. The smaller catalyst, Pd(OAc)2 was the most poorly rejected catalyst. This catalyst showed signs of instability in the selected solvents. An interesting finding from this study is that of higher rejections in water compared to other solvents for a particular catalyst. In this regard, the influence of solventsolute effects was evident. Generally, higher rejections were observed in solvents with higher polarity. This has been explained by the concept of solvation. It has been shown that solvents with different polarity solvate solutes differently, therefore leading to a different effective solute diameter in each solvent. Catalyst separation using NF90 membrane was attempted for the Heck coupling reaction system. The reaction-separation procedure was repeated for two filtration cycles with rapid activity decline evident. This was regarded as very poor showing of the catalyst separation efficiency of the membrane. Other authors in similar studies using SRNF membranes have reported reaction-separation processes of up to seven cycles. This observation shows the inferiority of polymeric membranes in organic solvent applications such as catalyst separation.
Identification and quantification of selected pesticides in surface water in Southern Gauteng region
(2011-06-10) Bucibo, Malesole Nontutu Gadihele; Sipamla, A.M.; Sibali, L. L.
The increased production and application of pesticides for agricultural and non-agricultural purposes has caused the pollution of air, soil, ground and surface water. This has a negative impact on the environment as well as human health due to direct exposure or through residues in food and drinking water. The continuous monitoring of pesticides residues in environmental samples has great importance and demands high efficiency, unique selectivity and high sensitivity techniques. Gas chromatography and high performance liquid chromatography have been established for years as the techniques for the analysis of pesticides residues. The dissertation deals with the qualitative and quantitative determination of selected pesticides in the Southern Gauteng region using Liquid- liquid extraction solid-phase extraction, high performance liquid chromatography, gas chromatography equipped with electron capture detector and gas chromatography mass spectrometry. Liquid-liquid extraction and solid-phase extraction using dichloromethane, hexane and ethyl acetate as the extracting solvent were optimized and evaluated for the determination of pesticides in surface water in the Southern Gauteng region. From the developed method the techniques were applied to water samples taken from different rivers selected namely: Zuikerbosch, Rand Water barrage and Kliprivier for sampling. Dichloromethane was used as a solvent in this study since a recovery test was done between dichloromethane, Ethyl acetate and n-hexane. The percentage recovery test for 4,4-DDT, 4,4-DDE, 2,4-DDD and Endosulfan 1 & 2 ranged from 89.9% -97.3% for dichloromethane, 87.3%-96.8% for hexane 88.4%-97.1% for ethyl acetate. The extracts obtained were subjected to column chromatography for clean up. Thereafter 1µl of the cleaned extracts were injected into the Gas chromatography equipped with an electron capture detector. Organochlorines 4,4-DDT and its metabolites, Organophosphate Chlorypyriphos and carbamates were detected using Gas chromatography electron capture, Gas chromatography mass spectrometry and high performance liquid chromatography.
Effects of oxidation states of Copper (Cu), Nickel (Ni), Palladium (Pd) and Silver (Ag) on rejection by nanofiltration membranes
(2011-08-10) Brooms, Thabo John; Modise, S. J.; Nelana, S. M.
Mining industry produces metals which are economical and serve as high valuable commodities in South Africa. This country is regarded as the world leading producer of precious metals such as platinum group metals (PGMs). Silver (Ag), which is also a precious metal, contribute to the country’s economy wealth due to its significance during industrial applications. Base metals such as copper (Cu) and nickel (Ni), though they are low valued, play a significant role in the republics economic wealth. Mining wastewater contains some of these metals, which end up polluting the environment. A possibility to recover this was investigated using NF membranes. Mine effluent was simulated by using relevant reagents. Characterization of NF90, NF- and NF270 membranes, was done by using scanning electron microscopy (SEM), clean water permeability, single charged salts of NaCl and MgCl2 and binary mixture of NaCl/MgCl2 studies. All the rejection experiments were conducted at pH 2.0 with varying pressure and concentrations. Flux measurements indicated that water permeability through the membranes trend, NF270 > NF90 > NF-. The experiments were performed at pressures of 5 bar, 10 bar, 15 bar and 20 bar. For NF90 membrane, a rejection of Na+ monovalent ion in 20 ppm solution was less than of Mg2+ (divalent) ion. Percentage rejections of 90% (Na+) and 98% (Mg2+) were achieved. NF- had rejection of 83% and 90% for Na+ and Mg2+, respectively. In the case of NF270, the membrane had rejection of 92% (Na+) and 94% (Mg2+), respectively. At 100 ppm, all three membranes showed a decreasing trend in rejection while increasing pressure. For binary-solution mixture, Mg2+ ion still had the highest rejection compared to Na+ ion with about 94% and 85% on NF90 than on NF270 and NF-. The high rejection of divalent ion as compared to monovalent ion for charged solutes was due to solute size and electrostatic interaction between the membrane surface layer and the solute. In the case of transition metal rejection studies, Pd2+ ion had an average of 90%, with Ni2+ ion ≈ 95% and Cu2+ ion ≈ 98% as single salts on NF90 compared to NF270 and NF-. However, as for binary and trinary solution mixture, the competition amongst ions was high, where Pd2+ ion rejection was ≈ 99,0%, while Ni2+ and Cu2+ ions was > 90% on NF90 and NF-. Therefore it was excluded from the tests. For the monovalent metal ions (Ag+ and Cu+), the rejection was > 90% in almost all concentrations mixtures. During membrane fouling evaluation, AgCl salt fouled the most, compared to other metal ions, forming a concentration polarization accumulation on the membrane surface for both 20 and 100 ppm solutions. This situation leads to cake layer formation which causes a flux decline, reduces membrane life time and lowers the rejection performance of NF membranes. The aim of this study was to evaluate the performance of three commercial polymeric membranes (NF90, NF270 and NF-) during rejection of the metal
Synthesis and characterization of cobalt and copper sulfide nanoparticles with reproducible stoichiometry using sulfur containing single-source precursors
(2012) Sibokoza, Simon Bonginkosi; Moloto, M. J.; Moloto, N.
Complexes of alkyldithiocarbamate and thiuram have been extensively explored for various applications in the medical field. Thiuram and dithiocarbamate ligands were used to prepared complexes of cobalt and copper. The high abundance of sulfur in these ligands has resulted to be the preferred complexes for the synthesis of metal sulfide nanoparticles. All the prepared complexes were characterized using techniques such as IR and 1HNMR spectroscopy, elemental analysis, and thermogravimetric analysis. All the spectra data obtained were consistent with the coordination of the ligands through sulfur atom to the metal ion. The thermogravimetric analysis of all complexes decomposed to form metal sulfide, which really confirmed that all the complexes could be used to metal sulfide nanoparticles. All the prepared complexes were used to synthesize MxSy nanoparticles. The metal sulfide nanoparticles were successful prepared by thermal decomposition of the single-source precursor in hexadecylamine solution. The reaction parameter such as the concentration (1.0, 0.5, 0.25 and 0.125 g), reaction temperature (80, 130, 200, 250 °C) and the time (5, 10, 15, 20, 25 and 30) of the reactionwere varied to see their effect on the preparation of the nanoparticles. The prepared metal sulfide nanoparticles were characterized using techniques such as UV spectroscopy, photoluminescence spectroscopy, X-ray diffraction analysis and transmission electron microscopy. The concentration was found to have a profound effect in size and shape of the prepared nanoparticles. The nanoparticles prepared at various concentrations were dominated by sphere with an average size of 2-30 nm. The XRD pattern confirmed that the composition is not affected by the temperature. Thetemperature has a dramatic effect in size, shape and the stoichiometry of the reaction. This was confirmed by an increase in size as the temperature was increased, with the exception of cobalt sulfide nanoparticles that decrease in size while temperature was increase. The XRD pattern showed different composition as the temperature was varied. Time of the reaction was found to affect the particles size of the nanoparticle. The sizes of the nanoparticles were increase as the time of the reaction was prolonged.
Synthesis and characterization of graphene and carbon nanotubes for removal of heavy metals from water
(Vaal University of Technology, 2012-06) Thema, Force Tefo; Moloto, M. J., Prof.; Dikio, E. D., Prof.
The commercial flake graphite was prepared into functionalized graphite oxide (GO) by adopted chemical treatment. After the exfoliation and intercalation of graphite into functionalized graphene oxide that formed stable colloidal dispersion in polar aprotic solvent, the reduction process was undertaken by continuous stirring with hydrazine hydrate in a microwave at 35 oC for two hours. The reduced material was characterized by X-ray diffraction (XRD), attenuated total reflectance (ATR) FT-IR, Ultra-violet visible (UV-vis), atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman microscopy and magnified optical microscopy that confirm the oxidation of graphite and reduction of graphene oxide into graphene sheets. Carbon nanomaterials were synthesized from Co-Sn, Co-Sr and Co-Zn as catalysts supported on Al2O3, CaCO3 and MgO. The as-prepared nanomaterials were characterized by thermogravimetric and derivative thermogravimetric analysis (TGA & DTA), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and the transmission electron microscopy. The intensity ratios (ID/IG) of the D- and G- bands were found to be the same that is averagely at 0.83. The TGA & DTA curves have shown Co-Sn/Al had significant weight loss, Co-Sr/Mg weight loss and decomposition, Co-Sr/Al decomposition and Co-Zn/Mg weight loss. However these weight losses were not significant. The EDS analysis showed all elements which took part in the reaction confirming the success of each synthesis. The SEM images show carbon nanotubes only on samples that have been synthesized on MgO as confirmed by TEM images. Finally the XRD showed some characteristic peaks at desired peaks except that they were other peaks attributed to impurities and armophous carbon. It was also observed that Co-Sn/Ca and Co-Sn/Mg XRD curves showed broad peaks at theta = 24.3o & 42.6o and theta = 23.9o & 43.1o respectively which are lattice structure characteristic peaks.
Investigation of causes of foaming in industrial waste water treatment and effects of substances in industrial waste water treatment
(Vaal University of Technology, 2012-06) Maleka, Mamohau Julia; Sipamla, A. M., Prof.; Mtunzi, F. M., Dr.
The research was aimed to study the causes of excessive foaming in a waste water treatment plant. Although the activated sludge process has been adopted to treat this industrial waste water , lots of problems were experienced by the inhibitory effects of toxic compounds that are found in industrial effluents and the foaming stability that was very high. Industrial waste water treatment using sludge processes was found to be more challenging than the normal municipal waste water treatment although the principle is the same; the foaming tendencies were found to be more in industrial waste water. In this study the composition of influents to the waste water treatment plant and operating parameter’s effects on foaming tendencies were examined. The foaming potential in the plant was found to be chemically related due to high contamination of compounds such as phenols, which played a major role in formation of stable foam. It was recommended that there must be pretreatment of the incoming influents to minimize their impact to waste water treatment.
Competitive biosorption of a mixture of cationic dyes from a multicomponent solution using modified pine cone powder
(Vaal University of Technology, 2012-07) Ngema, Silindile Lucia; Ofomaja, A. E., Dr.; Naidoo, E. B., Prof.
The biosorption of methyl violet and methylene blue onto modified pine cone powder was studied. Single and binary component systems studies were carried out for the biosorption of methyl violet and methylene blue onto raw, Fenton treated and acrylic acid grafted pine cone powder. Various experimental parameters were studied including initial dye concentration (200-900 mg/dm3), contact time, solution pH (4-12), mass of adsorbent (0.05-0.30g) and temperature (25-45 °C). Pseudo-first order and pseudo-second order equations were used to analyze the kinetic data. It was found that the data follow the pseudo -second order kinetic model for all temperature studied. The experimental data were analyzed using Langmuir and Freudlich isotherm model. The biosorption of methyl violet and methylene blue showed a better fit to Langmuir isotherm which properly describes the experimental data and that the sample surfaces are homogeneous. Various thermodynamic parameters, such as Gibbs energy (ΔG*), enthalpy change (ΔH*) and entropy change (ΔS*), were calculated which indicated the present system was spontaneous and exothermic process for methyl violet and methylene blue. It was found that enthalpy and entropy of acrylic acid grafted pine cone was higher as compared to raw and Fenton‘s reagent for methyl violet and methylene blue. Raw, Fenton treated and acrylic acid pine cone powder were characterized with Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectroscopy (UV-VIS), Thermogravimetic analysis (TGA/DTA), X-ray Diffraction (XRD) and Brauner, Emmett and Teller (BET). The following parameters were used to determine the surface properties of the grafted pine cone: change in H+ concentration and oxidation reduction potential (ORP), surface negative charge, bulk density and acid number measurements. The FTIR analysis confirmed the presence of the organic compounds on the raw, Fenton treated and acrylic acid grafted pine cone powder. The UV/VIS determined the percentage removal of dyes from aqueous solution in single and binary component systems by comparing the raw, Fenton treated and Acrylic acid grafted pine cone powder. Thermo gravimetric analysis confirmed the reactions which occur at the molecular level of the raw, Raw + KMnO4 and Fenton treated + KMnO4 pine cone powder materials. The second order derivative spectroscopy (SODS) was a suitable method for the analysis of the study of cationic dyes in binary solution. To determine the unknown concentrations of methyl violet and methylene blue dyes in binary solution using SODS, maximum wavelengths 561.8 nm and 623.1 nm were obtained. It was found that the percentage removal was higher for acrylic acid grafted pine cone than Fenton‘s treated and raw pine cone and treated samples adsorbed more methyl violet that methylene blue.
Impact of metallurgical industries on water
(Vaal University of Technology, 2012-07) Matsie, Simon Sello; Smith, N.; Naidoo, E. B., Prof.
The increase in industrial activities has contributed towards an increase in environmental pollution problems. Many ecosystems have deteriorated as a result of an accumulation of pollutants including heavy metals contained in effluents discharged from various industrial processes. Legislative standards require that pollutant levels be controlled to fall within set limits. The World Health Organisation (WHO) states that the following metals: aluminium, chromium, manganese, iron, cobalt, nickel, copper, cadmium, mercury and lead are a concern. The research has focussed on the removal of heavy metals from industrial waste water. This was achieved by investigating, characterising and quantifying pollutants within a metallurgical industry environment resulting from applied operations technology and then looking into abatement measures that can be put in place.The study was done and conclusions are discussed below. Analysis of samples indicated the presence of heavy metals with varying concentrations at different sampling points. D1 borehole is found to have higher chromium levels because ferrochrome was once stored in that catchment area. The dam and road bridge sites manganese content is higher due to suspended particulates settling on the ground and being washed down by water streams . Raw materials from mines contain heavy metals which are transferred to water systems during handling. In this research the toxic metal ion biosorption on an inexpensive and efficient biosorbent from agricultural waste materials has been investigated as replacement strategy for existing conventional systems. The study was conducted by using eucalyptus leaves powder for sequestering heavy metal ions from waste water. The metal uptake from an aqueous solution is facilitated by functional groups in the ligno-cellulosic material Many solids are capable of adsorbing ions and molecules from solutions . The removal of heavy metals from aqueous solution using eucalyptus leaves has been investigated under different experimental conditions viz. initial metal concentration and adsorbent mass. Results obtained indicated a decrease in metal concentration due to biosorption of a known elemental concentration per known volume by a known mass of sorbent over a specific time. Sorption is found to be dependent upon contact time, initial concentration, sorbent dose of small quantities of wastewaters containing heavy metals. In the event of high levels of heavy metal being experienced, ground eucalyptus leaves can be used for heavy metal recovery from wastewater. A procedure covering the sorbent mass required per average specific pollutant concentration over a specific time frame can be compiled to optimise sorption. The advantage of biosorption compared to conventional treatment methods are low cost, high efficiency, minimisation of chemical and biological sludge as well as the regeneration of biosorbents and a possibility of metal recovery.
Isolation and characterization of bioactive compound from Combretum erythrophyllum leaf extracts
(Vaal University of Technology, 2012-08) Ledwaba, Imelda Phuti; Sipamla, A. M., Prof.; Mtunzi, F. M., Dr.
Combretum erythrophyllum has been used for medicinal purposes and several studies have been carried out to investigate the bioactive compounds present in the leaves of this plant. The World Health Organization reported that 80% of the people living in the developing countries almost exclusively use traditional medicine. Combretum species are used in many human medicines for the treatment of microbial infections and several anti-inflammatory conditions. Members of the Combretaceae family are widely traded in the traditional medicine market in Southern Africa. The family is also used for medicinal purposes in the rest of Africa and Asia for close to 90 medicinal indications. Many of these indications are related to infective agents. Traditional healers have long used plants to prevent or cure infectious conditions. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids and flavonoids, which have been found in vitro to have antimicrobial properties. This review highlights the current status of traditional medicines, its contribution to modern medicine, recent trends in the evaluation of anti-microbial activity with a special emphasis upon some tribal medicine, in vitro and in vivo experimental design for screening and therapeutic efficacy in safety and human clinical trials for commercial outlet. Many of these commercially available compounds are crude preparations administered without performing human clinical trials. The leaves of Combretum erythrophyllum were extracted with acetone to obtain the crude extract. Liquid-liquid fractionation was performed on the crude using different solvents of different polarity. The crude and obtained fractions were investigated for antimicrobial activity. The crude and fractions were tested against certain bacterial and fungal microorganisms. The assay methods used included the microtitre dilution method for determining the minimum inhibitory concentration and bioautographic methods used to detect the inhibition of bacterial and fungal growth by active compounds separated from the crude and fractions. The antioxidant activity was performed using TLC-DPPH, DPPH, ABTS and hydroxyl radical scavenging. The toxicity of crude extract and fractions was determined using MTT assay. Isolation of compounds was performed using column chromatography. Structural elucidation was done using NMR and MS spectrometry. In microtitre dilution assay acetone fraction inhibited the growth of S. aureus, E. faecalis, P. aeruginosa with the lowest MIC value of 0.02, 0.32, 0.16 μg/ml and ethyl acetate fraction inhibited the growth of E. coli with the lowest MIC value of 0.16 μg/ml. All fractions were active against C. neoformans with the MIC value of 0.02 μg/ml. Dichloromethane was the least active against C. albicans with the MIC value of 0.16 μg/ml while the rest had the MIC value of 0.08 μg/ml. Dichloromethane was found to be active against A. fumigatus with the lowest MIC value of 0.16 μg/ml. Bioautography showed the presence of various inhibitory chemical compounds. Ethyl acetate and hexane fraction had a very good separation and showed various zones of inhibition on exposure to E. faecalis, E. coli, S. aureus and P. aeruginosa with the Rf values ranging from 0-0.98. Crude and fractions showed slight zones of inhibition against C. neoformans, C. albicans and A. fumigatus with the Rf values ranging from 0-0.76. TLC-DPPH assay displayed that ethyl acetate and water fraction had the highest antioxidant activity in CEF. Ethyl acetate fraction had a strong antioxidant activity in DPPH assay with the EC50 of 0.04272 μg/ml, water fraction showed a good antioxidant activity with the EC50 of 0.01825 μg/ml in ABTS assay and in the hydroxyl radical scavenging the crude extract scavenged 77.62 ± 1.41% at the highest concentration of 0.250 mg/ml and 47.21 ± 3.20% at the lowest concentration of 0.003 mg/ml. The toxicity level of the crude extract and fractions were found to be between 34 and 223 mg/ml which were all below doxorubicin (LC50 = 7.1855 μg/ml) which was used as the positive control. Column chromatography was used in a bio-guided assay fractionation and led to isolation of one compound. The antimicrobial activity was determined against pathogenic bacteria. The isolated compound had a good activity against Pa and Sa with the lowest MIC value of 0.32 μg/ml. Nuclear magnetic resonance spectroscopy (NMR) and mass spectroscopy were used for the identification of isolated compounds. One compound was isolated and identified as Friedelin. The results obtained confirm that the leaves of Combretum erythrophyllum have a good antimicrobial activity and strong antioxidant activity.
Development of a simple technique for selective removal of cesium in wastewater in the presence of mixed alkali metals
(Vaal University of Technology, 2012-08) Pholosi, Agnes; Ofomaja, A. E., Dr.; Naidoo, E. B., Prof.
Amongst treatment technologies, adsorption is rapidly gaining prominence because it can remove metal pollutants at low concentrations, economical, ease of operation, and the adsorbent can be regenerated for reuse. This study therefore, aimed at developing a simple material for selective removal of cesium from wastewater. An agricultural waste material (pine cone) was used as a cheap solid support for transition metal hexacyanoferrate and applied as biosorbents for cesium removal. The preparation and characterization of biosorbent for cesium removal in the presence of alkali metals is reported. The experimental procedure was carried out in three phases; the first phase described the sample preparation. Toluene-ethanol mixtures of different ratios were investigated as surface treatment method for pine cone and the optimum treatment ratio determined by measuring the improvement in surface properties of the pine cone such as bulk density, iodine number, and surface negative charge. The modification of pine cone with iron hexacyanoferrate was examined in the second phase. The preparation of potassium iron(III) hexacyanoferrate (KFeHCF) supported toluene-ethanol modified pine cone powder was studied in order to consider its application for cesium removal from aqueous solution. The biosorbent was designed to incorporate the hexacyanoferrate ligand which is known to have a high affinity for cesium ions in aqueous solution. Fe(III) was loaded onto the toluene-ethanol treated pine cone powder followed by hexacyanoferrate ligand incorporation on the biosorbent producing the potassium iron hexacyanoferrate supported toluene-ethanol treated pine cone. The modified pine cone was characterized by FTIR, XRD and TGA analysis. The influence of solution pH and adsorbent dose were studied. The application of potassium iron hexacyanoferrate for the selective removal of cesium in the presence of sodium and calcium was investigated in the third phase. Batch adsorption kinetic studies were performed to determine the effect of modification on cesium removal. Coefficient of correlation, r2, and Chi-square, χ2, methods were applied in the determination of the best fit kinetic method. Increasing the ratio of toluene in the extractant mixture increased formation of esters and iodine capacity of the material, but reduced carboxylate ions and surface charge. Maximum cesium adsorption was observed for the 2:1 toluene-ethanol treated sample. Structural characterization using FTIR, XRD and TGA confirmed the successful modification of KFeHCF pine cone powder. Cesium adsorption experiments indicate that KFeHCF supported toluene-ethanol modified pine was more efficient for cesium removal than the raw pine cone powder. Kinetic modeling of Cs+ adsorption was done using the pseudo-first, pseudo-second order and diffusion chemisorption kinetic models. The pseudo first order kinetics could not accurately predict the experimental data. The kinetics data fitted the pseudo-second order and diffusion-chemisorption models. The chemisorption diffusion model only accurately describes the experimental data after 5 min of contact whereas the pseudo second order describes the experimental data over the range of contact time. The application of the FeHCF modified pine cone for cesium removal from aqueous solution revealed that the FeHCF modified pine was less affected by the presence of competitive cations than the toluene-ethanol treated sample and the raw pine cone sample.
Modification of glassy carbon electrode (GCE) with prussian blue as a mediator on carbon nanotube materials through sequential deposition
(Vaal University of Technology, 2012-08) Farah, Abdullahi Mohamed ; Modise, S. J., Prof.; Dikio, E. D., Prof.
Prussian blue (PB) nanoparticles were synthesized from FeCl3.6H2O, K4[Fe(CN)6].3H2O, and from Fe(NO3)3.9H2O and K4[Fe(CN)6].3H2O, and then characterized by Fourier transform infrared (FT-IR), Ultraviolet-visible spectroscopy, X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), Scanning electron microscopy (SEM), Raman spectroscopy and thermogravimetric analysis. Graphene oxide and carbon nanotubes were also synthesized and characterized. PB nanoparticles, carbon nanotubes (CNT), graphene oxide (GO) and cetyltrimethylammonium bromide (CTAB) were sequentially deposited onto glassy carbon electrode surface to form chemically modified electrode for the detection of hydrogen peroxide (H2O2) and dopamine. The following electrodes were fabricated, GC-PB, GC-MWCNT, GCGO, GC-CTAB, GC-MWCNT-PB, GC-GO-PB and GC-CTAB-PB. Cyclic and Square wave voltammetric techniques were used to measure the hydrogen peroxide detectability of the electrodes at pH ranges of (3 - 7.4) in 0.1M phosphate buffer solution, in the absence or presence of 25 μL of H2O2. The GC-CNT-PB, GC-GO-PB,GC-CTAB-PB electrodes showed a good response for the detection of hydrogen peroxide in both acidic and neutral media while the GCPB electrode only showed good response in acidic media.
Synthesis and characterization of carbon nanomaterials using BIS(acetylacetonato)oxovanadium(IV), Manganese(III) Acetylacetonate, Co-Zn and CoAI as catalyst precursors.
(2012-11-01) Ndwandwe, Silindile Nomathemba.; Dikio, E. D.
Bis(acetylacetonato)oxovanadium(IV), Manganese(III) acetylacetonate, Co-Zn and Co-Al were prepared as catalyst precursors for the synthesis of carbon materials in a catalytic chemical vapor deposition (CCVD) reactor. The carbon materials produced were characterized with Raman spectroscopy, Scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), High resolution transmission electron microscopy (TEM) and Thermogravimetric analysis, (TGA). Carbon material prepared from bis(acetylacetonato)oxovanadium(IV) catalyst precursor showed the presence of carbon spheres with average diameter of 104μm together with small traces of carbon nanotubes or amorphous carbon. Synthesis of bis(acetylacetonato)oxovanadium(IV) catalyst precursor yielded approximately 92% of carbon material. Carbon material prepared from Manganese(III) acetylacetonate catalyst precursor showed the presence of carbon spheres with diameter of 87.5μm. Synthesis of Manganese(III) acetylacetonate catalyst precursor yielded approximately 97% of carbon material. Carbon material produced from Co-Zn and Co-Al catalyst precursors showed the presence of carbon nanotubes with small amounts of amorphous carbon. The use of Co-Zn catalyst precursor yielded approximately 80% of carbon nanotubes, whereas Co-Al catalyst precursor yielded approximately 98% of carbon nanotubes.
Evaluation of biological activities of nine anti-inflammatory medicinal plants and characterization of antimicrobial compounds from Pomaria sandersonii and Alepidea amatymbica
(2013) Muleya, Eddwina; Mtunzi, F. M.; Sipamla, A. M.; Eloff, J. N.
Medicinal plants provide valuable alternative sources of drugs and drug discovery because many have been used in traditional practices for centuries to manage or treat various forms of ailments. The aim of this study was to evaluate the biological activities of nine medicinal plants used by Zulus in Mabandla village, KwaZulu-Natal province, South Africa to treat inflammation and to isolate selected active compounds against studied pathogens from Alepidea amatymbica and Pomaria sandersonii. The plants were selected on the basis of an ethnobotanical survey based on questionnaire response and verbal interviews that were conducted in Mabandla village with the local traditional healers and herbalists. The isolation of compounds from Alepidea amatymbica and Pomaria sandersonii was based on the bioassay based study which was carried out in this study. Bioassay guided study involving in vitro anti-inflammatory measurement using soya bean derived 15 Lipoxygenase, free radical scavenging capacity against the ABTS●+ radical cation and DPPH● radicals; antimicrobial and bioautography assays against Staphylococcus aureus, ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 29212, Escherichia coli, ATCC25922, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus were carried out using the plants extracts, fractions and pure compounds. Isolation of compounds displaying biological activity was carried out by using open column chromatography and preparative thin layer chromatography (PTLC). The compounds were characterised by use of Nuclear Magnetic resonance, (NMR) and Mass Spectrometry (MS). The DPPH sprayed TLC showed that all the nine plants contained antioxidants. Most of which were contained in polar fractions of acetone and methanol. Results of the assays displayed a range of biological activities comparable to the positive controls used for each assay. DPPH● scavenging displayed EC50 values ranging between 1.008 and 467 Kg/ml. The highest activity was observed with the methanol fraction of Berkheya setifera with an EC50 value of 1.008 Kg/ml followed by the crude extract of Gunnera perpensa with EC50 value of 1.069 Kg/ml. Carissa bispinosa hexane fraction had the lowest activity of 467.7 Kg/ml. The Pomaria sandersonii DCM extract had the highest ABTS●+ radical scavenging activity by Pomaria sandersonii DCM extract, (1.273 Kg/ml) for the ethyl acetate, (5.973 Kg/ml) while the hexane fraction from Eucomis autumnalis had the lowest activity (929.4 Kg/ml). The activity of Pomaria sandersonii extracts and fractions demonstrated that the plant contains antioxidants that react with both DPPH and ABTS radicals although higher activities were shown by ABTS as displayed by the lower EC50 values. All the crude fractions and extracts had high to moderate antibacterial activities (20-625 Kg/ml) and anti-fungal activities (20-2500 Kg /ml). Pomaria sandersonii crude and fractions had the highest antimicrobial activity compared to other plants. Some MIC values for P. sandersonii dichloromethane and ethyl acetate fractions (80 Kg/ml in each case) compared well with gentamycin (4 Kg/ml) since they showed same values against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudonomus aeruginosa. The dichloromethane, acetone and methanol fractions were also active (20 Kg/ml) against both Candida albicans and Aspergillus fumigatus. Inhibition of pathogen growth demonstrated by the polar fractions of the studied plants suggested that some of the active compounds would be soluble in water. A total of seven compounds were isolated from Alepidea amatymbica and Pomaria sandersonii. We propose three were new compounds after considering literature search involving closely related research to this investigation. These were two diterpenes from Alepidea amatymbica, namely, 14-acetoxo-12-oxokaur-16-en-19-oic acid labelled as 0657 and 16-hydroxy-kaur-6-en-19-oic acid given the label 06-2 in this study. The third suspected new compound is the chalcone dimer, which is referred to as EM86 in this study from Pomaria sandersonii. EM80-2 was obtained as a mixture of the cis and trans of 2’, 4, 4,’-trihydroxychalcone or 1-(2,4-dihydroxyphenyl)-3-(4-hydroxyphenyl)-2-propen-1-one, from Pomaria sandersonii. The three diterpenes, 14-acetoxokaur-16-en-19-oic acid (0652), 13-hydroxy-16-kauren-19-oic acid (06B) and 14-oxokaur-16-en-19-oic acid (06431) were isolated from Alepidea amatymbica for the first time. Isolated compounds were further tested as individual compounds and results showed that 16-hydroxy-kaur-6-en-19-oic acid (06-2) had weak activity against tested bacteria and fungi with the MIC: Staphylococcus aureus (320 Kg/ml) and Candida albicans, (320 Kg/ml). On the other hand 13-hydroxy-kaur-16-en-19-oic acid (06B) was more active against, Staphylococcus aureus (160 Kg/ml) and Aspergillus fumigatus (40 Kg/ml). The yellow compound that was isolated from Pomaria sandersonii, 1-(2, 4-ihydroxyphenyl)-3-(4-hydroxyphenyl)-2-propen-1-one was antimicrobial with the following MICs: Candida albicans: 80 Kg/ml; Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecalis, Staphylococcus aureus: 160 Kg/ml and Aspergillus fumigatus: 625 Kg/ml. There were two mixtures referred to as EM 49 and EM 77 from Pomaria sandersonii which were difficult to purify but had anti-microbial inhibitory activities worth reporting. EM49 had MIC against Candida albicans of: 160μg/ml; Pseudomonas aeruginosa: 320 Kg/ml, Escherichia coli: 80μg/ml, Enterococcus faecalis 80μg/ml, and Staphylococcus aureus: 80μg/ml and Aspergillus fumigatus: 320μg/ml. EM 77 had MIC against Escherichia coli: 80 Kg/ml and Cryptococcus neoformans: 80μg/ml. Further work on their purification need to be done since in this research we are just reporting on their high MIC activities. The medicinal plants used to treat inflammation under different disease conditions in the Zulu community of Mabandla village, Kwa-Zulu Natal, South Africa have some relevant biological activities. The various antimicrobial, antioxidant and anti-inflammatory activities support the validity of their healing capacities that the traditional healers of the community claim to possess. Although there is evidence of good antimicrobial, antioxidant and anti-inflammatory activities by the crude extracts, the high levels of sucrose in P. prunelloides and glucose in G. perpensa should be borne in mind when using their decoctions in traditional medicine particularly by diabetic patients. In vitro results for the antioxidant, antinflammtory and antimicrobial activities carried out in this investigation illustrate that the plants can be a source of treatment and management for inflammation related conditions. These therefore justify their use in Zulu traditional medicine. However, in vivo assays should be carried out in order to completely validate claims by the traditional healers that they treat inflammation related conditions.
Development and optimization of selective leaching processes for the extraction of calcium from steel slag in view of sequestering carbon dioxide
(2013-05) Kotoane, Alice Mpho; Naidoo, E. B.; Doucet., Frederic J.
Several technologies are currently being developed to mitigate the greenhouse gas CO2. One of these promising processes is industrial mineral carbonation whereby alkaline industrial wastes are taken as raw material. The process is a multi-step process which involves the extraction of calcium from industrial alkaline wastes and the subsequent reaction of extracted calcium rich supernatant with CO2 at elevated pH to form stable carbonates. Steelmaking slags were selected from four different plants in SA and used for this investigation owing this to their high calcium content. The potentially-suitable four slags were selected on the basis of their Ca content and high chemical reactivity. The objective of this investigation was to develop a common leach process for all four steel slags to achieve a complete Ca extraction from slags. A Ca rich solution was carbonated to achieve a stable carbonate that can be used. Experiments were carried out using ammonium reagents and a hydroxide reagent to investigate their suitability for the rapid, selective extraction of calcium. Calcium was leached under different experimental conditions including varying leachant concentrations, temperatures and solid to liquid ratios. The slags exhibited contrasting reactive properties to different leachants, which can essentially be explained in terms of differences in mineralogical composition, hence mineral solubility characteristics. Leaching with 2M NH4NO3 aqueous solution at room temperature extraction efficiency increased with increasing concentration. The extent of extraction was different for the four slags. WMO5 showed a complete dissolution of Ca within 20 min of experiment. This difference is due to their different Ca-containing minerals. Same is observed with aqueous NH4CL but WMO5 did not reach a complete dissolution as with NH4NO3. Aqueous NaOH made it impossible for Ca extraction due to its high pH and upon slag addition it was more elevated. Increasing solid to liquid ratio had an influence in percentage slag loss. The pH of leach solution was elevated to 9 making it difficult to extract Ca. Under controlled conditions (pH kept under 1) optimal slag dissolution was achieved with traces of larnite and large amount of brownmillerite. The generated Ca-rich leachate was carbonated in a 600 ml reactor vessel with liquid CO2. A stable carbonate aggregate was produced.
Determination of the antibacterial, antioxidant activity, isolation and characterisation of active compounds from the leaves of Rhys Leptodictia plant
(2014-02) Matamela, Tshifhiwa; Myunzi, F. M.; Sipamla, A.
Rhus leptodictya commonly known as a mountain karee belongs to the family Anacadeceae and has been used since antiquity in tradition medicine. In the present study antimicrobial and antioxidant potentials of the leaves of Rhus leptodictya were studied, followed by isolation of at least one active compound which showed antibacterial and antioxidant potentials. Extractions were performed based on the polarity of the solvent used. The solvents used were hexane, dichloromethane, ethyl acetate, acetone and methanol. Dichloromethane was found to be extracting more compounds than the other used solvents. Thin layer chromatography (TLC) was used to determine the chemical composition of the extracts by employing different solvent systems. The results showed that, of the solvent systems used, namely ethyl acetate: methanol: water (EMW) 40: 5: 1; chloroform: ethyl acetate: formic acid (CEF) 5: 4: 1 and benzene: ethanol: ammonium hydroxide (BEA) 90:10:1, BEA produced better separations. To determine the antioxidant potential of the leaves, 2.2-diphenyl picrylhydrazyl (DPPH) was used. Different spot with different Rf values were found to be active by show of yellow colour on the TLC plate. The yellow colour is due to the proton gained by DPPH when it reacts with active compound. Bioutography results showed that different leaves were active against selected bacterium. Minimum inhibitory concentration studies showed that the methanol extract was more active against B.subtilis and S.pnuemonia at concentration less than 0.1 mg/ml respectively. Dichloromethane extract was found to be the least effective on S.pneumonia, as compared to the methanol, acetone and ethyl acetate extracts. In terms of the total activity, the ethyl acetate concentration showed better total activity than the other extracts studied in this research. A new compound 7, 8-trihydroxy-2-(4’hydroxy phenyl)-3-5-[5’’, 6’’-dihydroxy-2’’-O-(4’’’hydroxyphenyl)-4-1t-chromen-4’’-one]-41t-chromen-4-one was isolated and characterized by H1-NMR, C13-NMR, MS and IR. According to the literature search, this compound has never been isolated from any plant and it has showed both antioxidant and antibacterial activity.
Method development and Validation for the determination of selected Polycyclic Aromatic Hydrocarbons (PAHs) in water by Solid Phase Extraction and High Performance Liquid Chromatography
(Vaal University of Technology, 2014-02-12) Xoliswa, Madlanga; Simpamla, A. M., Prof.; Mtunzi, F. M., Dr.
Polycyclic Aromatic Hydrocarbons (PAHs) are one of the pollutants in the environment. They are organic compounds that consist of more than one aromatic ring (Kanchanamayoon & Tatrahun 2008). Due to less information forthcoming regarding the levels of PAHs in Vaal area, this study is to evaluate the levels of PAHs in the rivers around Vaal Triangle. Three river sites such as Vaal, Barrage and Klip Rivers were selected to investigate the concentration of polycyclic aromatic hydrocarbons in water. Validation of an analytical method is the process by which it is established by laboratory studies, that the performance characteristics of the method meet the requirements for the intended analytical application. (Stockl et al 2009). The validation parameters tested were, linearity detection limit of quantitation, sensitivity, accuracy, specificity, selectivity, robustness and ruggedness. PAHs can be determined using High Performance Liquid Chromatography (HPLC) which is a technique for separation, identification and quantification of components in a mixture. The following ten compounds were identified and quantified with a HPLC: naphthalene, acenaphthylene, phenanthrene, anthracene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h) anthracene and indeno(1,2,3-cd)pyrene. The linear calibration ranges from 0.1-5ppm.The linearity ranges between 0.9993-0.9999.Three reversed sorbent phases (Strata-X, MFC18 and C18) were tested for PAH retention efficiency. An optimised reverse solid phase extraction (SPE) method was used after conditioning the sorbent to extract and collect compounds of polycyclic aromatic hydrocarbons (PAHs) in river water samples. LC18 sorbent showed good recoveries after extracting PAHs standard mixture of 1 mg/l. The best performing eluting solvent was acetonitrile and very good percentage recoveries that ranged from 70% to over 100 % were obtained for eight compounds. Poor recoveries were also obtained for phenanthrene (61%) and benzo(b)fluoranthene (48%). The standard deviation ranged from 0.01 to 0.05 and the detection limits ranging from 0.01 – 0.17 mg/l were obtained. Average concentration ranges of PAHs identified within the study area were: phenanthrene (0.02 – 0.42 mg/l); anthracene (0.37 – 0.39 mg/l), fluoranthene (0.11 – 0.15 mg/l); benzo(b)fluoranthene (0.09 mg/l) and indeno(1,2,3-cd)pyrene (0.26 mg/l). However, naphthalene, acenaphthylene, benzo(k)fluoranthene, benzo(a)pyrene and dibenzo(a,h)anthracene were not detected.
TiO₂-supported dealuminated clinoptilolite: synthesis characterisation and kinetic studies for enhanced photo catalytic degradation of volatile organic compounds
(2014-06) Sanni, Saheed Olalekan; Modise, S. J.; Sipamla, A. M.
Advanced oxidation processes (AOPs) are supposedly effective means for removal of low concentration of organic pollutants from waste water as compared to conventional treatment methods. However, TiO2 metal semiconductor is the most promising photocatalyst for degradation of organic pollutant under heterogeneous photocatalysis as compared to other metal semiconductors. Challenges such as aggregation in solution, low adsorptive ability for non-polar organic contaminants and recycling are limitations in application of TiO2 for commercial purposes. The other limitations of TiO2, is it only utilizes 4-6% of the solar energy reaching the earth's surface which is in the UV region and also rapid electron-hole recombination due its wide band gap. In this work, the limitations are overcome by synthesis of a new photocatalyst material and further applied on degradation of model organic contaminants. The first part of this work focused on preparation and characterization of photocatalyst material. The photocatalyst synthesized were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and UV-VIS diffuse reflectance spectrophotometer (DRUV-VIS). Supporting characterization techniques revealed partly dispersion of TiO2 within the cavities of dealuminated Clinoptilolite (HCP). TiO2 exist as nanoparticles or clusters on the HCP surface ascribed to lower loading of TiO2. XRD analysis showed that the support material employed was mainly Clinoptilolite and absorption band of prepared photocatalyst was red-shifted into the visible region, with slight reduction in band gap of photocatalyst. The second part focused on adsorption and photocatalytic degradation of methyl orange solution (MO) conducted under UV-irradiation in the presence of TiO2/HCP. The influence of operational parameters on degradation efficiency of photocatalyst material on MO was carried out in this study. Parameters such as initial dye concentration, pH, calcination temperature, inorganic anions and peroxide concentration were varied during degradation activities of MO. Comparative degradation efficiency of TiO2/HCP, TiO2 and HCP were conducted on dye mixture (Methyl orange and Methylene Blue) under UV irradiation. Kinetic analysis employing Langmuir-Hinshelwood model on dependencies of organic contaminants degradation was also conducted at different operational parameters. The adsorption capacity of MO was highest in the presence of TiO2/HCP at lower loading, which is ascribed to good dispersion of TiO2 on HCP and increased surface area of dealuminated Clinoptilolite. The photocatalytic degradation of methyl orange in the presence of TiO2/HCP was optimized at low dye concentration (30 ppm), acidic condition (pH 4), and calcination temperature of 873 K. Nitrate ion of Sodium salt accelerates degradation activities on methyl orange as compared to other inorganic anions. Photocatalytic degradation of methyl orange was greatly enhanced upon addition of oxidant (H2O2) and the photocatalyst possessed good repeatability after 3 cycles. TiO2/HCP exhibit highest degradation activities, followed by HCP as compared to TiO2 during the degradation of dye mixture. The degradation of MO by the photocatalyst fits into pseudo-first order kinetic model, while for comparative analysis of photocatalyst on dye mixtures follows second order kinetic model.
Synthesis, characterization and anti-bacterial studies or Hydrazide Schiff bases of Acetylacetonate metal complexes
(2014-06) Dikio, Charity Wokwu; Mtunzi, F. M.; Sipamla, A. M.
Infectious diseases, a group of illnesses caused by specific pathogens or its toxins is a leading cause of death globally. Treatment with antibiotics is a key intervention in the control and management of many infectious disease. However, the increasing incidence of antibiotics failure, due to the emergence of drug resistant pathogens, is rendering the use of antibiotics chemotherapy ineffective. A possible solution is to synthesize new compounds with broad spectrum characteristics and superior drug performances as alternative to conventional antibiotics. Schiff Bases are biologically active ligands. They form metal complexes with superior biological activities. This research aims to synthesize some Schiff Base metal complexes and investigate their biological effects on Staphylococcus aureus and Enterococcus faecalis. Metal acetylacetonates of Vanadium, Copper, Cobalt, Zinc, Magnesium, Manganese, Cadmium, Nickel and Iron were synthesized and characterized by Fourier transform infrared spectroscopy. Four Schiff bases, LI, L2, L3 and L4 were also synthesized by the condensation of 4- (diethylamino)-2-hydroxybenzaldehyde with 4-nitrobenzohydrazide and 4-methoxybenzohydrazide to form L1 and L2. 4-(dimethylamino) benzaldehyde was reacted with 4-nitrobenzohydrazide and 4-methoxybenzohydrazide to form L3 and L4 respectively. The Schiff base ligands were then reacted with synthesized Vanadium, manganese, cobalt and magnesium acetylacetonates to form Schiff base complexes (SBC 1A to 4D). Schiff bases ligands and complexes were characterized by FT-IR, 1H-NMR, 13C-NMR, TGA and DTA. Fourier Transform infrared spectroscopy (FTIR) of the acetylacetonates showed the formation of metal acetylacetonates as characterized by the absence of the carbonyl stretching n(C=O) vibration in metal acetylacetonate spectra as compared to pure acetylacetone. Metal acetylacetonates also showed the presence of metal oxygen vibration frequency, n(M-O-C), in the spectra obtained. Thermogravimetric analysis (TGA) and Derivative or Differential Thermogravimetric analysis (DTA) of the Schiff base ligands showed the presence of a single decomposition product in L1, L2, L3 and L4 indicating the formation of a single reaction product while those of Schiff base complexes showed the formation of several decomposition products. Proton and carbon thirteen Nuclear Magnetic Resonance (1H- and 13C-NMR) spectroscopy of the Schiff base ligands indicated the presence of hydrogen and carbon-13 in different environments. The chemical shifts of the hydrogens and carbon-13 provided evidence that Schiff base ligands were formed. The strongest evidence is the presence of the azomethine hydrogen and carbon in the spectra of the Schiff base ligands. The presence of aromatic hydrogens and carbon at chemical shift environments found in literature also confirmed the formation of Schiff base ligand. The NMR spectra of Schiff base complexes showed the presence of azomethine (HC=N) and aromatic hydrogens at expected chemical shifts. The synthesized Schiff bases and their corresponding metal complexes were screened for their invitro antibacterial activities against two Gram-positive (Staphylococcus aureues and Enterococcus feacalis) bacterial strains by the Agar-well diffusion methods.The ligands and complexes were tested against confirmed S. aureus and E. faecalis strains and only 4 exhibited antimicrobial activities. The ligands and complexes were effective against the S. aureusand E. faecalis isolates.

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