Browsing by Author "Moodley, Brenda."

Now showing 1 - 14 of 14

Analysis and monitoring of persistent organic pollutants in the Umgeni River, KwaZulu-Natal, South Africa.
(2016) Gakuba, Emmanuel.; Moodley, Brenda.
Abstract available in PDF file.
Analysis of targeted pharmaceuticals and metabolites at a wastewater treatment plant in KwaZulu-Natal, South Africa.
(2022) Inarmal, Nikitha.; Moodley, Brenda.
Globally, surface water bodies are shown to be severely contaminated by chemical compounds as a result of human activity. Some of these compounds are inclusive of pharmaceuticals and their metabolites which are classified as emerging contaminants (ECs). A major contributor to this pollution event is treated wastewater effluent. This is an area of growing concern, particularly for emerging economies, due to an increase in demand for clean and potable water arising from rapid urbanisation and significant population growth. In South Africa, there is limited information outlining concentrations of various pharmaceuticals in treated wastewater effluent and surface water bodies and there is currently no legislation indicating maximum concentrations to be allowed in wastewater effluent. This research study aimed to identify and quantify concentrations of selected pharmaceuticals and metabolites present at various stages within the Wastewater Treatment Plant (WWTP). Additionally, the study aimed to determine seasonal pharmaceutical trends in relation to SARS-CoV-2 (COVID-19) and influenza infections, removal efficiencies and undertake an environmental risk assessment (ERA). The pharmaceuticals that were analysed included metformin, caffeine, sulfamethoxazole hydroxylamine, sulfamethoxazole, nevirapine, prednisolone, valsartan, rifampicin, 17α ethinylestradiol (EE2) and ivermectin, all of which being pharmaceuticals that are commonly prescribed for the treatment of medical conditions that are prevalent in South Africa and for the treatment and prevention of COVID-19. Analyte concentrations were assessed in wastewater samples taken from the inlet, balancing tank, secondary effluent, and maturation river over three sampling seasons. Analytes were extracted using a solid phase extraction (SPE) method and extracts were analysed using liquid chromatography – mass spectrometry (LC – MS). Method percentage recoveries ranged from 73.53 – 100.70% while limit of detection (LOD) and limit of quantification (LOQ) overall ranged from 0.0330 – 0.886 mg L-1 and 0.0990 – 2.68 mg L-1, respectively. Analyte concentrations quantified in inlet samples ranged from 0.007587 – 1.243 mg L-1 while balancing tank concentrations ranged from 0.007599 – 1.042 mg L-1. Secondary effluent and maturation river concentrations ranged from 0.0005244 – 0.9483 mg L-1 and 0.0002507 – 0.9286 mg L-1, respectively. Non-detection of certain analytes in some samples could imply the possibility that the pharmaceutical converted into transformation products and thus evaded detection. Influent pharmaceutical concentrations showed distinct seasonal variation, and this was statistically shown using a one-way ANOVA analysis. P-values were recorded as < 0.05 for caffeine, sulfamethoxazole hydroxylamine, sulfamethoxazole, EE2 and ivermectin, thus implying that significant differences were observed between seasonal levels of pharmaceutical compounds and in relation to the COVID-19 and influenza infection peaks. Analyte removal efficiencies based on the plant treatment processes ranged from 7.70 – > 99.99 %. The ERA performed indicated ratios within the range of 0.0863 and 10.5x 108, which is of significant concern as values greater than 1 would severely impact the health of aquatic organisms and ecosystems within the receiving surface water body.
Assessment of the impact of reforestation on soil and river water quality based on organic chemical pollutants.
(2018) Pillay, Vishalan.; Moodley, Brenda.
Forests are a natural resource and are influential in most countries as they are a source of food, clothing, and form of shelter for many organisms. These sections of forested land have been sacrificed for the development of urban areas, making way for agriculture, cities and the ever increasing human population. Some of the detrimental effects associated with deforestation are as follows: loss of wildlife and fish habitats, increased nutrient and sediment loads in nearby rivers, and ultimately increases in greenhouse gas emissions. Reforestation refers to the planting of trees so as to replenish an area that was previously a forest but due to anthropogenic effects, such as land deforestation, resulted in its deterioration. This project aimed to assess the impact of the eThekwini Municipality reforestation project on the quality of the soil within the reforestation sites, and water from the nearby rivers (White and Black Mhlasini Rivers) situated at the reforested Buffelsdraai area in KwaZulu-Natal. The levels of organic pollutants were assessed from the analysis of soil, sediment and river water. Selected polyaromatic hydrocarbons (PAHs) and pesticides, which had been previously utilised at this site when it was a sugarcane farm, were analysed. The sixteen PAHs analysed were naphthalene, acenaphthylene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[i]fluoranthene, benzo[a]pyrene, benzo[e]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, and benzo[g,h,i]perylene which are on the Environmental Protection Agency (EPA) list of priority pollutants. The pesticides analysed were hexazinone, oxamyl, and acetochlor. The soil and sediment samples were extracted using ultrasonication, and liquid-liquid extraction was utilised for the water samples. Gas chromatography mass spectrometry (GCMS) and liquid chromatography mass spectrometry (LCMS) were used to analyse the PAHs and pesticides, respectively. PAH recoveries on the GCMS ranged between 60-110%, and pesticide recoveries on the LCMS were between 83-113%. The PAH LOD values were between 0.30–0.69 μg g-1 and between 0.17-0.32 μg g-1 for pesticides. PAH LOQ values ranged between 0.99-1.9 μg g-1 and between 0.56-1.33 μg g-1 for pesticides. The total PAH concentrations determined were between 4.258 – 6.426 μg g-1 in the soil samples, 2.210 – 13.900 μg g-1 in sediment, and 6.360 – 85.468 ng L-1 in river water. The total pesticide concentration was between 1.271 – 1.742 μg g-1 in soil, 0.197 – 1.175 μg g-1 in sediment, and 0.792 – 12.950 ng L-1 in river water. A comparison between the soil samples and the control,showed that reforestation is potentially reducing the concentration of organic chemical pollutants. The water and sediment samples also provided potential evidence of the positive impact of reforestation, as it revealed the concentration of pollutants to be lower within the reforestation boundaries and higher outside the reforestation boundary. The most abundant PAH determined in the samples was fluoranthene, which could possibly be due to this hydrocarbon being the most abundant aerosol in the atmosphere. Source apportionment analysis showed that most PAHs originated from pyrolytic sources, which was from burning of sugarcane. The total concentration for specific PAHs was above the threshold value for most sampling sites according to Canadian environmental guidelines. However, reforestation was shown to potentially be reducing these pollutant concentrations. The findings from this study will assist the neighbouring communities and eThekwini in future planning for the extension of existing or development of new reforestation sites.
Characterisation of SAPPI SAICCOR pulp mill's effluent.
(2001) Moodley, Brenda.; Marsh, Jeremy J.; Mulholland, Dulcie Aca.
SAPPI SAJCCOR, whose factory is situated south of Durban, South Africa, is one of the few paper and pulp mills that uses the acid sulphite process with calcium and magnesium bases to produce a high-grade cellulose pulp. Four streams of effluent, namely, the calcium - spent liquor stream, the magnesium condensate stream and two streams from the bleaching effluent are produced during this sulphite pulping process and they contain a variety of organic compounds extracted from the wood. Characterisation of the effluent was based on isolation using column chromatography and identification using NMR techniques. A range of constituents, such as lignans and lignin - type precursors, a trilerpenoid and fatty acids were isolated and identified. X-ray diffraction was used to identify an inorganic residue obtained from the calcium - spent liquor stream and gas chromatography/mass spectrometry was used to identify a wax residue. which builds up in the process. In addition to this, the carbohydrate content of the four streams of effluent was detennined using UV/visiblc spectroscopy.
Detection and quantification of emerging contaminants in Mgeni and Msunduzi rivers by gas chromatography-mass spectrometry in KwaZulu-Natal, South Africa.
(2018) Gumbi, Bhekumuzi Prince.; Ndungu, Patrick Gathura.; Moodley, Brenda.; Birungi, Grace.
This work concerns the development, optimization and validation of simple and affordable analytical methods for determination of different classes of emerging contaminants in environmental waters and solids. Occurrence of emerging contaminants in the African environment has received much attention recently. However, there is paucity of detailed analytical methods for determination and regulation of emerging contaminants in the environment and wastewater effluents in South Africa today some parts of the world. The developed methods included, extraction with solid phase (clean-up), ultrasound-centrifuge assisted extraction (sediments), detection with gas chromatography-mass spectrometry (after derivatization of polar analytes) and ecological risk assessment technique associated with emerging contaminants. For all developed methods, recoveries (60% - 130%), R2 (> 0.99) and precisions (< 25%) within acceptable limits were achieved. This study was undertaken to determine the occurrence and concentration of major classes of emerging contaminants (pharmaceuticals, personal care products and stimulants) between 2014 and 2016 in Mgeni and Msunduzi Rivers, KwaZulu-Natal, South Africa. Surface water, wastewater (influent and effluent), sediment and biosolid samples were collected from these rivers and wastewater treatment plants along both rivers. The developed methods were combined and applied to qualitative and quantitative analysis of pharmaceuticals (acidic/ non-steroidal antiinflammatory drugs, antibiotic and hormones), stimulants (caffeine) and personal care products (paraben and triclosan). Approximately 50 emerging contaminants of different classes were detected and only 15 were quantified. Environmental concentration of contaminants were found to range from 0.02 μg L-1 to 68 μg L-1 and 0.12 to 220 ng g-1 in water and sediments respectively. Acidic drugs, antibiotic and hormones were detected in all samples analysed in both water and sediments, however, stimulant and PPC were not detected in some of the samples. Wastewater treatment plants were recognised as one of the main routes of emerging contaminants into the aquatic environment. The developed methods can be used to monitor emerging contaminants in the environment.
The determination of organochlorinated pesticides and polychlorinated biphenyls in sediment, soil and water of the Msunduzi River, KwaZulu-Natal, South Africa.
(2014) Adeyinka, Gbadebo Clement.; Moodley, Brenda.
Persistent organic pollutants (POPs) are a major class of organic contaminants of serious global concern due to their persistence in the environment because of their stability to photolytic, chemical and biological degradation. POPs are mostly semi volatile organic compounds (SVOCs) and include polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), which are toxic and capable of causing serious health disorders, such as, developmental and cancer related problems in animals and humans. Organic pollutants, such as, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are as well toxic as inorganic pollutants. There is limited information available on the concentration level and distribution pattern of organic pollutants within the KwaZulu-Natal Rivers as well as many studies done within this area have also only focused on inorganic pollutants. The lack of information and the need for knowledge on the organic pollutants in these rivers together with global concern for quality water has therefore prompted an investigation of the organic pollutants in the selected river. Therefore, the results and outcomes of this study could serve as a baseline assessment for various levels of government and scientific communities for future planning on the state of this river. The concentration patterns of selected priority pollutants (dirty dozen) made up of eight polychlorinated biphenyl (PCB) congeners and seven organochlorine pesticides (OCPs) together with six DDT metabolites were evaluated in sediment, soil and surface water during autumn, winter, spring and summer seasons from the Msunduzi River of KwaZulu-Natal, South Africa. Sediment, soil and water samples were collected at ten sites along the river in April 2013, July 2013, September 2013 and February 2014 that represented autumn, winter, spring and summer sampling seasons. Soil and sediment samples were dried and sieved while water samples were kept at 4 °C prior to the extraction. Soil and sediment samples were extracted by ultrasonication with dichloromethane (DCM) and water samples were subjected to liquid-liquid extraction using DCM. All sample extracts were cleaned up using multi-layered acidic/basic silica gel and all quality assurance steps were carefully observed. Both PCB congeners and OCPs were analysed and quantified in the sample extracts using gas chromatography–mass spectrometry (GC-MS). All the PCB congeners and OCPs analysed were detected in sediment, soil and water samples during all seasons. The results showed that sediment and soil samples contained the highest concentrations of both PCBs and OCPs with water samples having the lowest concentrations of all the analytes throughout the seasons. Concentrations of PCB congeners detected in the environment were found to be dependent on the number of chlorine atoms on the phenyl ring of PCB congeners, were PCB 180 exhibited the highest concentration and PCB 138 was found to be present in the lowest concentration. Total DDTs and endrin were the most predominant OCPs. The result of indicative indices suggested that the presence of DDTs could be attributed to the aged long degradation of DDT to its metabolites. The concentration patterns of the pollutants during the seasons were found to be in decreasing order of winter, spring, autumn and summer seasons. The concentrations detected in water samples during the seasons were also found to exceed the United State Environmental Protection Agency (USEPA) of 0.014 ng/mL and European Union (EU) 0.01 ng/mL recommended tolerable levels in surface and underground water respectively.
Determination of polycyclic aromatic hydrocarbons in the water, soils and surface sediments of the Msunduzi River, KwaZulu-Natal, South Africa.
(2016) Munyengabe, Alexis.; Moodley, Brenda.; Mambanda, Allen.
Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants which are known carcinogens. Their presence in the environment has been linked to cancer, neurological and reproductive illnesses to name but a few. Hence it is important to monitor the levels of these PAHs in order to identify areas of high pollution and possible toxic exposure to aquatic and human life. The concentration of seven polycyclic aromatic hydrocarbons (namely naphthalene, acenaphthylene, fluorene, phenanthrene, anthracene, pyrene and chrysene) were determined in 28 surface water, 8 wastewater, 26 soil and 26 surface sediment samples from the Msunduzi River. Water samples were extracted using a liquid-liquid extraction technique into dichloromethane and dehydrated with sodium sulfate anhydrous. The soils and surface sediments were extracted with a mixture of dichloromethane and n-hexane (1:1 v/v) using the soxhlet extraction technique. The crude extracts were purified by silica gel packed column chromatography. The concentrations of PAHs in the extracts were analysed by GC-MS. The instrument was calibrated using internal standardization (deuterated PAH) and PAH standards. Percentage recoveries of 7 PAHs in the spiked and equilibrated samples varied from 79.16±0.01 to 101.28±0.02 and 80.30±0.02 to 105.56±0.01 for solid and water samples, respectively. The grand average in the summed concentrations of concentrations of the 7 PAHs in the water for all seasons decreased in the order: Σ[7-PAH] spring > Σ[7-PAH] summer > Σ[7-PAH] autumn > Σ[7-PAH] winter while in the surface sediments was in the order: Σ[7-PAH] spring > Σ[7-PAH] autumn > Σ[7-PAH] summer > Σ[7-PAH] winter and in the soils was in the order: Σ[7-PAH] spring > Σ[7-PAH] autumn > Σ[7-PAH] winter > Σ[7-PAH] summer. The concentration of PAHs was found to be comparatively higher in the soils and surface sediments than in the water samples.
The effect of extraction methods on the oxidatives stability of marula and moringa seed oil.
(2017) Nwabuebo, Anwuli Tracey.; Moodley, Brenda.; Goyvaerts, Elisabeth.
Marula and moringa seeds are used as a source of food, and the seed oils are used in cosmetics, pharmaceuticals and in medicines. This is due to its high nutritive value and high content of unsaturated fatty acids, which however makes them highly susceptible to oxidation. Due to its high nutritive value, the demand for the seed oil often exceeds industrial supply. Therefore, a timeous and environmentally friendly extraction method, which produces an oil with better oxidative stability, is required. Hence, the reason for this investigation on the effect of screw press, aqueous extraction (37 and 60 °C) and solvent extraction (shaker and Soxhlet) method on the oxidative stability of marula and moringa seed oil. The oxidative stability of the seed oils was determined by carrying out several tests, such as moisture content, acid value and peroxide value (PV). In addition, the anisidine value (AV), radical scavenging activity, conjugated diene (CD) and triene (CT) % were determined by UV-Vis spectroscopy. The fatty acid methyl ester content was determined using gas chromatography-mass spectrometry (GC-MS). The result for the oil yield showed there was a significant difference (P˂0.05) in the different extraction methods. Soxhlet extracted marula and moringa seed oil had the highest oil yield of 53.99 % and 35.20 %, respectively. Aqueous extracted marula and moringa oil at 37 °C had the lowest oil yield of 18.67 % and 12.00 %, respectively. The fatty acid profile showed the presence of palmitic, stearic, oleic, linoleic and behenic acid in moringa seed oils with oleic acid being the most dominant in the seed oils with the different extraction methods. Soxhlet extracted marula and moringa seed oil had a fatty acid composition of 70.70 and 77.61 % respectively, while aqueous extracted marula and moringa seed oil at 37 °C was 72.36 and 79.94 % respectively. The oxidative stability test PV, a measure of the initial oxidation, and AV, a measure of secondary oxidation product, showed there was a significant difference (P˂0.05) for the different extraction methods. Aqueous extracted marula and moringa seed oil at 37 °C had the highest radical scavenging ability compared to the other extraction techniques. The oxidative stability test carried out for 35 days at ambient and different accelerated storage conditions (45 and 65 °C) showed that aqueous extracted seed oil at 37 °C for both seed oils had lower values for the oxidative tests and lower values for the rate of change of PV and AV values thus suggesting a better stability oil. This could be as a result of the presence of the higher monounsaturated fatty v acid which aids stability, and lower polyunsaturated fatty acid present. A comparison of the stability tests for two seed oils showed that moringa seed oil had a better stability. This is probably due to the lower secondary oxidation products present in moringa oil as well as a higher quantity of monounsaturated fatty acid and lower quantity of polyunsaturated fatty acid present compared to that of marula. This study showed that aqueous extracted seed oils have a has a better resistance to degradation and oxidation reduction and shelf life in comparison with the other extraction methods. Also, moringa seed oil showed a better resistance to degradation as compared to marula seed oil
The isolation, structure elucidation and biological testing of compounds from Plectranthus hadiensis.
(2010) Dukhea, Shiksha.; Koorbanally, Neil Anthony.; Moodley, Brenda.
Three diterpenes of the abietane class, 7b-acetoxy-6b-hydroxyroyleanone (I), 6b,7b- dihydroxyroyleanone (II) and ent-pimara-8(14),15-diene-3b,11a-diol (III) and three triterpenes, 2a,3a,19 -trihydroxyurs-12-en-28-oic acid (IV), stigmasterol (V) and lupeol (VI) were isolated from the stem and leaf material of Plectranthus hadiensis. The structures of the compounds were elucidated using 2D NMR spectroscopy and Mass spectrometry. All six compounds have been isolated previously, but this is the first occurrence of compounds III-VI in Plectranthus hadiensis. This is also the first report of the isolation of a pimarene from Plectranthus, which provides a biochemical link to other genera in the family Lamiaceae where this class of compounds exist. Compounds I to IV were tested for their antibacterial activity against Enterococcus faecalis and Pseudomonas aeruginosa as well as their anticancer activity against breast (MCF-7), renal (TK- 10) and melanoma (UACC-62) cell lines. Compounds I and II exhibited good antibacterial activity against Enterococcus faecalis and Pseudomonas aeruginosa and although the entpimara- 8(14),15-diene-3 ,11 -diol (III), was inactive against E. faecalis, it was very active against P. aeruginosa. Compound IV, the triterpenoid, was structurally different to I-III and did not show any anti-bacterial activity. Compounds I-III were weakly active toward the cancerous renal (TK-10), melanoma (UACC-62) and breast (MCF-7) cell lines, while IV was inactive in all of the cell lines.
Partitioning studies of polychlorinated biphenyls between aqueous solution and soil and sediment systems of Umngeni river, KwaZulu-Natal, South Africa.
(2018) Adeyinka, Gbadebo Clement.; Moodley, Brenda.
The significance of soil and sediment physicochemical properties and the environmental parameters such as pH, temperature, ionic strength, humic acid (HA) and time on the partitioning action of eight selected polychlorinated biphenyl (PCB) congeners were critically evaluated in this study to better understand the mobility, transportation, fate and distribution of hydrophobic organic pollutants in environmental media. Natural soil samples used in this study were collected along uMngeni River of KwaZulu-Natal province of South Africa. The mineral properties of soil samples were determined using the Walkley Black method, barium chloride compulsive exchange method and Brunauer-Emmet-Teller (BET) adsorption-desorption isotherm. All these were employed to observe the surface characteristics of the modeled individual soil particle sizes. Scanning electron microscopy (SEM) equipped with energy disperse X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) were used for the internal morphology and qualitative elemental analysis, as well as identification of possible functional groups in soil samples and commercial HA. Batch adsorption experiments were used for sorption studies. The results revealed that the amount of PCBs sorbed by soil was found to increase with an increase in contact time reaching equilibrium within 8 h. Among the soil chemical properties, soil organic matter was observed to correlate positively and play a more significant role in the sorption of PCBs. Soil samples with highest BET surface areas were related to the soil particle grain size. The sorption of PCBs onto soil was also found to decrease with an increase in the aqueous HA concentrations, and a change in the aqueous concentration of ionic strength was found to be less significant. Other important factors found to be more significant in the sorption were the degree of chlorination as well as stereochemistry of PCB congeners. The more hydrophobic and non-ortho (planar) congeners were found to contribute more significantly to sorption relative to the less hydrophobic and more ortho-substituted (nonplanar) congeners. Moreover, a decrease in the ratio of Si: (Al + Fe) was found to contribute positively to the sorption of PCBs. The kinetic studies on the partitioning of PCBs onto the soils was found to fit best with pseudo-second order, suggesting that the partitioning process of the selected PCBs between aqueous solution and active components in soil, involved more than onestep. Logarithmic values of organic carbon normalized sorption coefficient (log Koc) of the selected PCBs were found to decrease with an increase in the solution pH. The partitioning of PCBs onto the soils was also said to be temperature driven, where low aqueous temperatures encouraged morepartitioning of hydrophobic PCBs onto the soil. The Gibbs free energy (ΔG°) was found to be negative. Therefore, the thermodynamic studies showed that the PCB interaction with soil particle sizes was a spontaneous process. The role of initial PCB concentration on the partitioning was found to be L-type. This indicated that an increase in PCB concentration in the aqueous phase made it more difficult for PCB molecules to find a vacant site available for sorption onto the soil SOM.
Phytochemistry and quorum sensing inhibitory studies of four vernonia species growing in Nigeria.
(2017) Aliyu, Abubakar Babando; Moodley, Brenda.
Abstract This thesis contains the phytochemical analysis of four medicinal Vernonia species growing in Nigeria and used in ethnomedicine to treat a variety of medical conditions. The four Vernonia species studied were Vernonia blumeoides, Vernonia perrottetii, Vernonia ambigua and Vernonia glaberrima. The thesis also contains a comprehensive review of the sesquiterpene lactones from the genus Vernonia, their structural diversity and biosynthetic considerations. For each of the plants, the crude extracts and selected compounds were tested for their antibacterial activity using the traditional disc diffusion and broth microdilution as well as anti-quorum sensing assays. Three of the four plants studied yielded sesquiterpene lactones, Vernonia blumeoides yielded four novel eudesmanolide sesquiterpene lactones (blumeoidolides A-D), Vernonia perrottettii yielded a novel keto-hirsutinolide 13-acetoxy-1(4β),5(6)β-diepoxy-8α-(senecioyloxy)-3-oxo-1,7(11)-germacradiene-12,6-olide B1 and the known keto-hirsutinolide 13-acetoxy-1,4β-epoxy-8α-(senecioyloxy)-3-oxo-1,5,7(11)-germacratriene-12,6-olide B2 and Vernonia ambigua yielded a novel glaucolide sesquiterpene, 5,6-dehydrobrachycalyxolide. The structures of the sesquiterpenes were determined from their 1H, 13C and 2D NMR spectra along with mass spectra. The crystal structure of one of the eudesmanolide sesquiterpenes allowed the configuration of the stereocentres in the molecule to be determined. In addition to the sesquiterpene lactones, some common sterols and flavonoids were isolated from the plants: stigmasterol was isolated from V. blumeoides, lupeol was isolated from V. blumeoides, V. ambigua and V. perrottettii and lupeol acetate from V. ambigua and V. perrottetti. The flavonoid apigenin was found in V. blumeoides, V. perrottetti and V. glaberrima, luteolin in V. blumeoides and V. perrottetti, velutin in V. perrottetti and V. glaberrima and chrysoeriol in V. ambigua and V. glaberrima. Chrysin was found only in V. blumeoides and luteolin 3',4'-dimethyl ether in V. glaberrima. Several of the isolated sesquiterpene lactones showed good anti-quorum sensing inhibition (QSI). QSI ≥80% was obtained for blumeoidolide A at a concentration ≥ 0.071 mg mL-1, blumeoidolide B (≥ 3.6 mg mL-1) and B1 (1.31 mg mL-1), QSI ≥75% for B2 (0.33 mg mL-1) and QSI ≥84% for 5,6-dehydrobrachycalyxolide (2.6 mg mL-1). The sterols, lupeol and lupeol acetate, were also found to have QSI ≥84% at 2.6 mg mL-1. Molecular docking studies carried out on blumeodolides A-D in the binding sites of CviR and CviR' (transcription activator proteins) suggested that these molecules are able to bind to certain domains in the target protein, thus eliciting an effect. The current work adds to the library of sesquiterpene lactones from the genus Vernonia and provides some lead compounds to antibacterial activity via quorum sensing inhibition.
Phytochemistry and quorum sensing inhibitory studies of four vernonia species growing in Nigeria.
(2017) Abubakar, Babando Aliyu.; Koorbanally, Neil Anthony.; Moodley, Brenda.
Abstract available in PDF file.
Studies of ionic liquid modified materials for adsorption of organic pollutants from aqueous media.
(2015) Lawal, Isiaka Ayobamidele.; Moodley, Brenda.
Abstract available in PDF file.
A study of modified mesoporous silica for the adsorption of selected organic pollutants.
(2016) Akpotu, Samson Oghenemauro.; Moodley, Brenda.
Water is an essential natural resource the world over. Only one-tenth of the world’s water is pol-lution free and hence there is a need for remediating polluted water. These pollutants, some of which are organic (dyes and pharmaceuticals), are often difficult to remediate from wastewater. Of all the available remediation techniques, adsorption is a proven technique that combines ease of use and cost effectiveness in removal of these organic pollutants. This study is aimed at the synthesis and characterisation of mesoporous silica/ordered mesoporous silica from agrowastes and commercial precursors, and their utilization in adsorption of organic pollutants. Silica was modified with citric acid, graphene oxide and graphene because of silica’s ready availability, low cost and its environmentally benign nature. The synthesized materials were charactersied by means of various standard analytical techniques. In the first study, silica nanoparticles (SNP) and silica nanotubes (SNT) were synthesized from elephant grass. Parameters such as surfactant con-centration and temperature were investigated on the morphology of mesoporous silica which yielded SNTs and SNPs. These parameters, especially the surfactant concentration had a pro-found effect on the morphology of silica. SNT and SNP were applied in the adsorption of 2 dyes; methylene blue (MB) and methylene red (MR). The adsorption of MB and MR on SNT were 109.97 mg/g and 40.6 mg/g, respectively. For SNP, MB and MR adsorption was 104.85 mg/g and 40.98 mg/g, respectively. The adsorption of MB and MR increased with an increase in pH with pH 6 and 8 being the optimal pH for MR and MB, respectively. This slight difference in sorption capacities can be attributed to the surface area. Pseudo-second order and the Langmuir isotherm model best fitted the data obtained. In the second study, mobil catalytic material (MCM-41) was synthesised using tetraethylorthosilicate and elephant grass as precursors. Citric acid was used a modifier and applied in the adsorption of methylene blue. The citric acid had a significant effect on the adsorption capacity, which increased at basic pH. The mechanism for adsorption was electrostatic ion interaction. The maximum adsorption capacity of the modified material improved considerably with a qm of 204.08 mg/g at pH 10 and a temperature of 25 °C. The adsorption kinetics favoured the pseudo-second-order model and the best fit model for the equilibrium data was the Freundlich model. In the third study, MCM-41 was synthesized from millet straw (agrowaste). A citric acid-MCM-41 (SCA-MCM-41) composite was prepared by grafting citric acid (CA) onto MCM-41 for improvement of its adsorptive capacity for methylene blue (MB). The highest adsorption capacity was achieved at pH 8. The Temkin isotherm model was the best fit in analyzing the equilibrium data. Kinetics favoured the pseudo-second order and the optimum temperature for adsorption was 25 oC. In the fourth study, SNT was synthesized using elephant grass as a precursor and was encapsulated with graphene oxide and graphene and applied in the remediation of sulfamethoxazole from aqueous media. The highly hydrophobic materials had high adsorptive capacities for sulfamethoxazole. In this study, ordered mesoporous silica-graphene oxide (MCM-41-GO) and graphene (MCM-41-G) composites and as-synthesised MCM-41 were synthesized and applied in the adsorption of acetaminophen and aspirin from aqueous solution. Elemental analysis showed that the percentage carbon was MCM-41-G > MCM-41-GO > AS-MCM-41 > MCM-41. This conferred various degrees of hydrophobicity on these materials and hydrophobic interaction was the main mechanism of adsorption. The pseudo-second order model best fitted the adsorption kinetics and the Freundlich isotherm best described the equilibrium. These materials had higher sorption capacities as compared to unmodified MCM-41. In the last study, MCM-48 encapsulated with graphene and graphene oxide, and as-synthesised MCM-48 were synthesized and applied in the remediation of caffeine and phenacetin from wastewater. The results obtained were similar to that of the previous study and hydrophobic interaction was the main mechanism of adsorption. Overall the modification of mesopo-rous/ordered mesoporous materials proved very useful in the remediation of organic pollutants from aqueous media.