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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Attenuation of ionic pollutants in selected South African soils

Mwepu, Mireille K. M. 03 1900 (has links)
Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2007. / Two–thirds of South Africa, including more than 280 towns and settlements are largely dependent on groundwater for their drinking water supply and development. However, groundwater resources in South Africa are limited both in terms of quantity and quality, especially in the semi–arid parts of the country (Sililo et al., 2001, p. i). Therefore, the importance of protecting groundwater resources from pollution has been recognized. The first objective of this research was to investigate the attenuation capacity of a selection of soil horizons and materials representing major types of diagnostic horizons and materials in the South African soil classification in order to validate their chemical attenuation ratings as provisionally specified by Sililo et al. (2001, p. 4.6). The second objective was to assess the pollutant attenuation capacity of South African soil horizons and materials as well as describe the diagnostic value of key chemical properties of soils for conveying information on their contaminant transport/attenuation potential. The third objective was to investigate whether it is possible to apply acid/base priming using H2SO4 and Ca(OH)2 to a bulk quantity of soil in order to reduce the mobility of contaminants.
2

Modelling of sorption of trace elements in an agricultural soil impacted by mining activities

Mosai, Alseno Kagiso January 2017 (has links)
A dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science Johannesburg 2017. / The development of the economy of South Africa and many other countries has been highly dependent on mining industries. Minerals such as gold, platinum, diamond and many others have been mined and continue to be mined. Despite the importance of these minerals, their processing comes with social and environmental problems. During the processing of these minerals, trace elements such as copper, chromium, nickel, mercury, uranium, molybdenum and many others are released as wastes into the environment either, directly or indirectly. The release of the elements into the soil is of concern due to the possibility of groundwater system contamination. The presence of these elements in the groundwater system poses serious challenges to the wellbeing of life forms, due to their toxicity, when they exceed threshold limits. From the processing plants, these elements could be released onto the soil, and mobilise to groundwater, increasing the already existing environmental crisis due to water pollution. Once these elements are in the water, access to living organisms becomes easier through the food chain. Some of these elements are not biodegradable and thus persist in the environment as well as in the bodies of living organisms. They can cause serious health problems because of their toxicity effect. In humans, these elements can be carcinogenic, and also cause chronic disorders, kidney failures, defects in infants, bone and vascular diseases which could also be lethal. It is therefore of importance that these elements are neither bioavailable nor bioaccessible to living organisms. When these elements are mobile in the soil, the probability of reaching groundwater increases. Water, an important natural resource should always be protected from such pollutants. The demand for unpolluted water has been rising every year in the world due to increasing population, extended droughts and improper disposal. This research was dedicated to determining the behaviour of elements in an agricultural soil impacted by mining activities. Agricultural soils are sometimes exposed to pollutants that could originate from dust fallout or precipitation; fertilisers and manure; pesticides; and water used for irrigation. Understanding the iv processes that control the distribution of these pollutants in agricultural soils is an important risk assessment measure, considering that such pollutants have the potential of being taken up by crops and vegetables or transported to groundwater. In this study, a soil on a farm that grows vegetables for commercial purpose. Cabbage, spinach, carrots and potatoes are some of the vegetables grown on the plot and sold to markets in Pretoria and Johannesburg. The plot is in the vicinity of smelting operations in the North West Province. The mobility of trace elements in the soil can be controlled, depending on the type and properties of soil. Hence in this research, the ability of the soil to adsorb elements entering the soil is studied. The batch experimental work was performed to determine the effect of pH, initial concentration (5 - 100 mg/L), competing ions (Fe3+, Ca2+, Co2+, Mg2+, K+, Ni2+ and Zn2+), fertilisers (ammonium nitrate, ammonium phosphate and calcium chloride) and plant exudates (acetic acid, citric acid and oxalic acid as well as ethylenediaminetetraacetic acid (EDTA) which is often used as proxy organic ligand (found in manure)) on the adsorption of cadmium (Cd), copper (Cu) and chromium (Cr) onto an agricultural soil. The PHREEQC geochemical modelling code was used to complement experimental methods in predicting processes and to further assess the leaching behaviour of the elements. Powder X-ray diffraction (PXRD) and X-ray fluorescence (XRF) were used to determine the mineralization of the soil. The structural features of the soil were determined using Fourier Transform Infrared spectroscopy (FTIR) and the element content was determined using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The point of zero charge (PZC) of the soil was found to be 8.3 and the cation exchange capacity (CEC) of 51.6 meq/ 100g. In the absence of fertilisers and plant exudates, the soil exhibited a similar high adsorption for elements at all initial concentrations by all the elements. Most (> 90%) of the elements were adsorbed within the first 3 minutes of contact with the soil. Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms were used to describe the experimental data for the elements. Kinetic rates were modelled using pseudo first-order and pseudo second-order equations. Pseudo v second-order gave the best fit for all the elements (R2 >0.999) indicating chemisorption. The effect of pH on Cd and Cu was insignificant however, the adsorption of Cr decreased with pH. The presence of competing ions decreased the adsorption of cadmium more than that of the other analyte elements. The soil was generally effective in adsorbing and retaining the elements. However, the retention was highly dependent on elemental speciation and prevailing conditions e.g. pH (as in the case of Cu and Cr). Such changes in conditions would have implications for groundwater quality. The effect of plant exudates and EDTA was studied and the results showed that low molecular weight organic acids (LMWOAs) viz acetic acid (AA), citric acid (CA) and oxalic acid (OA) and EDTA significantly (p < 0.05) decreased the adsorption capacity of the elements onto the agricultural soil. AA had the least effect on the adsorption capacity of the elements whereas OA and EDTA strongly prevented the adsorption of the elements. Moreover, some of the elements which were already in the soil including those which were not under study such as Ca and Mg were desorbed from the soil by OA and EDTA. Thus, the mobility of the elements was increased by the presence of plant exudates, increasing groundwater contamination and consequently threatening the health of living organisms. Agrochemicals such as fertilisers, stabilizers and pesticides are constantly applied to agricultural soils to improve the fertility of the soil for better crop production however; their presence may affect the mobility and bioavailability of elements in the soil. The effect of ammonium nitrate and ammonium phosphate as well as calcium chloride on the adsorption of Cd, Cu and Cr onto an agricultural soil was studied. The effects of initial concentrations of the elements (5 – 50 mg/L), concentrations of fertilisers (0.01 – 0.1 mol/L) and pH (3 - 8) on the adsorption of Cd, Cu and Cr were studied. The initial concentration of the elements and the concentration of fertilisers had no significant effect (p > 0.05) on the adsorption capacities of Cu and Cr at pH 5. But, ammonium nitrate and calcium chloride decreased the adsorption capacity of Cd. The adsorption of Cd onto the soil was reduced as the concentration of fertilisers increased. The adsorption of Cd was lower than that of Cu and Cr at all pH values. The agricultural soil was found to vi be an effective adsorbent in preventing the mobility of Cu and Cr in the presence of fertilisers but not for Cd whose adsorption was significantly affected by the presence of ammonium nitrate and calcium chloride. A continuous flow fixed-bed column script with specified conditions simulating the natural environment was utilised in PHREEQC for column studies. The geochemical computer model PHREEQC can simulate solute transport in soil surfaces. The effect of initial concentration (100 and 300 mg/L) of the elements, column bed depth (5 and 10 cm) and pH (3, 5, 7 and 10) were considered in this study. The adsorption capacity was affected by initial concentration of the elements since the breakthrough curves at higher analyte concentrations were reached at lower pore volumes than at low concentrations. This can be attributed to the fast occupation of active sites of the soil at higher concentrations. The results from PHREEQC indicated that the conditions used would lead to the oxidation of Cr3+ to Cr6+ leading to the formation of HCrO4- and Cr2O72- which were not favoured for adsorption by soil surfaces due to high solubility. This could have potential implications on the quality of groundwater in regions with similar conditions. Thus, the leaching of Cr6+ onto the agricultural soil will be high in areas where remediation techniques are not applied. The changing of bed depth from 5 to 10 cm did not have an effect on the adsorption of the elements. The ability of the soil surfaces to adsorb Cd and Cu even at lower bed depth implies that the soil will be effective in preventing the leaching of the elements to groundwater due to strong surface interactions of the elements with the soil. The results from PHREEQC showed that the adsorption of Cd and Cr onto the soil surface was not affected by pH. The results for Cr were contradicting with those obtained from laboratory experiments which could be due to the conditions used in PHREEQC. The change in the speciation of Cu at basic conditions decreased the ability of Cu adsorption onto the soil surfaces. The Cu2+ was converted to Cu(OH)2 which were large in size and thus only a small amount could be adsorbed since the other adsorption sites were covered by the large species. This research had notable outputs in the form of publications which will form an important repository of information. / LG2017
3

Impact of mining operations on the groundwater quality within Vantech mine area in Mpumalanga province, South Africa.

Singo, Mangaga. January 2008 (has links)
Thesis (MTech. degree in Environmental management.)-Tshwane University of Technology, 2008. / Aims to generate information on the quality of water from boreholes and the Steelpoort river in order to ascertain the level of pollution within the vicinity of Vantech mine. The information is envisaged to help a better water management within the area. The following objectives were pursued: to measure water quality parameters ; to investigate the extent of the pollution plume movement ; to study the composition and geological factors in the area in relation to mobility of groundwater and to determine the impacts of Geo hydrological characteristics.
4

Silver nanoparticle-resin filter system for drinking water disinfection and inhibition of biofilm formation.

Mpenyana-Monyatsi, Lizzy January 2013 (has links)
D. Tech. Water care. / Groundwater is the main source of drinking in most rural areas of South Africa and is supplied to the communities without prior treatment. However, the contamination of groundwater sources by pathogenic bacteria poses a public health concern to these communities. This study was aimed at developing and evaluating the effectiveness of filter materials coated with silver nanoparticles for the removal of pathogenic microorganisms from groundwater as well as the inhibition of biofilm formation in drinking water systems.
5

Assessment of the effects of gold-mine effluent on the natural aquatic environment

Venter, Andries J.A. 21 May 2014 (has links)
D.Phil. (Zoology) / South Africa is a major gold-producing country with the 43 larger mines processing approximately 120 x 106 ton of milled and processed ore and about 30 x I06 ton of mined waste rock. Pollution of both surface and ground water, which can be attributed to the influences of gold-mining, are well known. Acid mine drainage, characterized by a low pH and high concentrations of dissolved metals, and seepage, from active and disused mine-tailings, are two of the main environmental problems associated with gold mining operations in South Africa. A growing concern for the environment and a stricter approach to water pollution by government agencies have made it necessary to investigate the type of effects which the gold mining industry is responsible for, and to develop action to reduce these impacts. The present study focused on procedures to access the effect of gold-mining effluent on the natural surface environment. The study is divided into three separate identities. The mine represented as Ccse study Mine One is considered to be a major contributor of salt loads to the natural stream on the property of the mine. This stream confluences with the Klip River outside the mined area. This mine has only one discharge point of underground mine service water, and is considered to be the main point source of pollution for the mine. As the mine makes use of an open water circuit, the quality and quantity of effluent have a direct effect on the downstream users. It appears that one of the main water quality problems of this open water circuit is the creation of surface water with a very low pH. Part of the problem is the geology of the area which consists of shales, which has a natural low buffering capacity. Because of the low pH the wetlands are not very effective. Metal concentration changes are possibly the direct result of the low pH of the both the water column and sediment. Improving the pH of the surface water can leads to reduced metal concentrations in the water, with possible increased concentrations in the sediment and wetland vegetation. Case Study Mine Two was conducted at a gold mine in the Far West Rand Mine region. The mine can be classified as having a closed water circuit, in that only excess water is discharged. The volume of water discharged is dependent on a number of factors, such as rainfall, wash-down service water and changing demands in sewage treatment systems. The advantage in this type of circuit is that water which has accidentally been spilled can be retained in one of the boundary dams, without the possibility of endangering the downstream users. From the assessment it appears that although the mining activities have influenced the water within the mining area this impact is only confirmed to certain areas. Biotic environmental conditions at certain sites resemble the conditions of the two control sites while other, notably those in contact with processing plants (e.g. metallurgical plant), are far more deteriorated. pH does not seem to be a problem at this specific mine. The main reasons are that the underlying geology of the mine is dolomitic in nature, while the sulphate concentration in the ore appears to be lower than those' found at the Witwatersrand mines. Case study Mine Three is situated in the Klerksdorp gold-mining region. The mine has a complex water circuit as a percentage of the service water is being reused or/and discharged via effluent streams into the Vaal River. Metal concentrations in the sediment core samples indicate a large variability between seasons, sites and depth. Sites in close proximity of slimes dams have high iron and manganese concentrations, whilst those in contact with effluent water from metallurgical plants have relatively high nickel, copper and in concentrations. This can be related to the type of processing material used in the gold-mining process.
6

Bioremediation of creosote-contaminated soil by microbial intervention..

Atagana, Harrison Ifeanyichukwu. January 2002 (has links)
No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.
7

Assessment of municipal solid waste leachate pollution on soil and groundwater system at Onderstepoort landfill site in Pretoria

Tshibalo, Rudzani 06 1900 (has links)
This study focuses on determining the quality of soil and groundwater at the Onderstepoort Municipal Solid Waste (MSW) landfill site. The study area is situated in Pretoria North, a jurisdiction of City of Tshwane Metropolitan Municipality (CTMM). Samples were collected from three different spheres (i.e. leachate, soil and water) in the study area, to determine the concentration of metals accumulated in each sphere. The three spheres provided an overview of the contaminants found in leachate, soil and water. The laboratory analyses using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) indicated that soils in the site have been severely contaminated with heavy metals. Higher concentrations of heavy metals occurred in the soils compared to the groundwater surrounding the landfill site and this may be due to the ability of the soil strata to absorb the contaminants caused by the landfill leachate. In essence, the measurements indicated that leachate soil has very high pollutant levels (0.21 to 2505.61 mg/kg); soil was characterised by fairly-high pollutant levels (0.03 to 638.27 mg/kg); leachate solution has given rise to moderate pollutant levels (0.01 to 2.296 mg/L) and water resources have low-moderate pollutant levels (<0.0001 to 0.456 mg/L) depending on the location. Furthermore, the findings indicated that the soil was contaminated with lead, cadmium, copper, zinc and nickel, and the concentration increases particularly where the generation of leachate is taking place. Groundwater, particularly in Borehole 2 has been moderately contaminated with nitrite, calcium and manganese. The findings also indicated that the concentrations of contaminants become high in borehole located close to the waste dump and decrease further away from the waste dump. The chemical analysis of this groundwater indicated that the concentrations of chemical properties have increased since the year 2009. This was determined through the comparison of groundwater study undertaken in 2009 to the current study results obtained. The site geological formation, Rustenburg Layered Suite is known to contain the anomalies of nickel, chromium, vanadium, copper, arsenic, lead and zinc but these are less toxic and less distributed. Therefore, the primary source of pollution at the study area could be the landfill operation through the generation of leachate affecting both soil and water / College of Agriculture and Environmental Sciences / M. Sc. (Environmental Sciences)
8

Synthesis of biopolymer-metal oxide nanoparticles reinforced composites for fluoride and pathogens removal in groundwater.

Ayinde, Wasiu Babatunde 20 September 2019 (has links)
Department of Ecology and Resource Management / PhDENV / Groundwater has traditionally been perceived to be low in chemical species toxicity and microbiologically 'pure'. However, depending on the geological chemistry, formations and anthropogenic activities creating the frequent occurrence of microbiological contamination and excess toxic chemical constituents, the high quality of groundwater as a drinking water source can easily be compromised rendering it unsafe, thus, leading to severe waterborne epidemics. The rapid increase in fluoride and microbial contamination of groundwater have become a global problem to human health. Fluoride in its acceptable concentration in drinking water (< 1.5 mg/L); is known to be beneficial for human growth and development but becomes detrimental at higher concentrations (> 1.5 mg/L) leading to the prevalence of dental and crippling skeletal fluorosis. On the other hand, consumption of microbiologically contaminated water has led to many types of diseases including diarrhea, cholera, typhoid, dysentery and other serious illnesses often leading to millions of deaths annually worldwide. South Africa had experienced water-borne diseases epidemic in the recent past due to failing water treatment facilities in many parts of the country including rural areas. Fluorosis, diarrhea, and cholera are among the chronic health hazards affecting a large population in South Africa. Continuous outbreaks of water-related diseases have been at an unimaginable high level with a reported increase in death rate. The inefficiency of conventional water treatment plants to remove fluoride and disinfect these pathogens from the contaminated domestic and rural community has led to the development of many techniques. These include membrane filtration, ion-exchange, coagulation-precipitation, adsorption among others of which adsorption process proves to be a more significant technology for fluoride removal. Equally, the emergence of nanomaterials has also proved to be the natural answer to solve problems associated with microbes in water since these are absolute barriers to pathogens whose size exceeds most sorbent pore sizes. Also, materials from natural biopolymers or biomass can be utilized at an affordable cost as effective sorbent material for toxic chemical ions and pathogens removal from contaminated water. Consequently, extensive research works have been channeled into the development of more advanced low cost sustainable functionalized sorbent materials and technologies with multifunctional properties for effective water purification. The present study focused on the development of a functionalized chitosan-cellulose hybrid nanocomposite decorated with metal-metal oxides nanoparticles for simultaneous fluoride and microbial removal from groundwater. This was to increase the selectivity and disruption of such pollutants for effective groundwater purification technology. The thesis is presented in nine chapters: (1) General introduction, problem statement, and motivation, research objectives, hypothesis and delimitations of the research are briefly discussed, (2) This chapter gives the literature review of occurrence and sources of fluoride, various fluoride removal techniques; sources, control measures and prevention of microbial pollution in groundwater; the importance of biosynthesis of nanomaterials as emerging novel water treatment adsorbents, the strength of Point-Of-Use as a means of water treatment, water treatment adsorbents synthesis and types of adsorbents with emphasis on hydroxyapatites and biopolymeric based sorbent materials, (3) Optimization of microwave-assisted synthesis of silver nanoparticle by Citrus paradisi peel extracts and its application against pathogenic water strain, (4) Biosynthesis of ultrasonically modified Ag-MgO nanocomposite and Its potential for antimicrobial activity, (5) Green synthesis of Ag/MgO nanoparticle modified nanohydroxyapatite and its potential for defluoridation and pathogen removal in groundwater (6) Green Synthesis of AgMgOnHaP nanoparticles supported on Chitosan matrix: defluoridation and antibacterial effects in groundwater, (7) Biosynthesis of nanofibrous cellulose decorated Ag-MgO-nanohydoxyapatite composite for fluoride and bacterial removal in groundwater, (8) Defluoridation and removal of pathogens from groundwater by hybrid vi cross-linked biopolymeric matrix impregnated Ag-MgOnHaP nanocomposite (9) Conclusions and Recommendations. It is important to point out that Chapters 3 to 8 contains a collection of the research deliverables produced in forms of paper publications and manuscripts and are summarized in a systemic order of experimental protocol. This first output (Chapter 3) of this study evaluated the optimization of a time-dependent microwave-assisted biosynthesis of silver nanoparticles using aqueous peel extracts of Citrus paradisi (Grapefruit red) as a reducing, stabilizing and capping agent with emphasis on its antibacterial property. Optical, structural and morphological properties of the synthesized Citrus paradisi peel extract silver nanoparticle (CPAgNp) were characterized using UV-visible spectrophotometer, transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), Brunauer–Emmett–Teller (BET) and X-ray diffractometer (XRD). The antimicrobial activity was evaluated using the well- and disc-diffusion as well as microdilution methods. Characteristic surface plasmon resonance (SPR) wavelength in the range of 420-440 nm at an optimized intensity growth rate typical of silver nanoparticles was obtained. Microwave irradiation accelerates the reaction medium within seconds of nucleation compared to conventional heating methods of synthesis. The influence of the reaction mixtures affected the SPR patterns on the different nucleation, stability and nanoparticle growth. The mixing ratio of 2:3 (C. paradisi peel extracts: 1 mM AgNO3) was chosen as the optimum reaction mixing ratio relative to the bio-reduction intensity of SPR process contributing to the particle size growth of CPAgNps. The presence, interaction and shifting of the functional groups in the FT-IR spectra of biosynthesized CPAgNps indicated that bioactive compounds present in C. paradisi peel extract were responsible for the bio-reduction of the silver ion to silver nanoparticles. The electron micrographs of the synthesized CPAgNps showed a face-centered cubic (FCC) unit phase structure, spherically-shaped nanoparticles size of 14.84 ± 5 nm with a BET pore diameter of 14.31 nm. The use of biological material allowed the control of the size and stability of the nanoparticle but was obtained in low quantity. The Citrus paradisi peel extract mediated AgNp were found to possess a broad-spectrum antimicrobial activity against water-borne pathogenic microbes in the order: Escherichia coli > Staphylococcus aureus > Klebsiella pneumonia. In Chapter 4, a synergistic bi-layered Ag-MgO nanocomposite from Ag and MgO precursor salts using a natural source from the waste product (citrus fruits outer cover) as a reducing and capping agent was successfully synthesized by a simple rapid, integrated bio-mediated microwave and ultrasonic methods. This was carried out to investigate the interfacial interaction and the encapsulated growth rate behind their combination in obtaining an enhanced antibacterial activity against common water fecal pathogen (Escherichia coli). The growth sequence, structural and morphology interface as well as the composition of the nanocomposite were examined and evaluated by the different characterization techniques. The respective potential application as an antimicrobial agent was evaluated and compared against Escherichia coli. The bio-mediated core-shell Ag-MgO nanocomposite showed characteristic synergetic UV-visible absorption bands at 290 nm for MgO nanoparticle and at around 440 nm for Ag nanoparticle, which moved to a lower wavelength of 380 nm in the composite. The shifting to a lower wavelength confirmed the reduction in the particle size as influenced by the growth rate optical property of biomolecular capped Ag-MgO nanocomposite from the phytochemical constituents in the peel extract of the Citrus paradisi. FTIR analysis further elaborated the role of the organic moieties in the Citrus paradisi extracts acting as the capping and stabilizing agent in the formation of the core-shell Ag-MgO nanocomposite. SEM analysis revealed an agglomeration of layered clustered particles, which was poly-dispersed while XRD showed the cubical crystal lattice network phase structure of the Ag-MgO nanocomposite. The TEM micrograph vii showed a structurally uniform and spherical biosynthesized Ag-MgO nanocomposite with a diameter of about 20–100 nm with an average particle size of 11.92 nm. The bi-layered Ag-MgO nanocomposite exhibited a higher level broad-spectrum of antibacterial potential on E. coli with 22 mm zone of inhibition and MIC of 20 (μg/mL) in comparison with the Ag (9 mm; 40 μg/mL) and MgO (9 mm; 80 μg/mL) nanoparticles. The leaching and toxicity level of the time-dependent releases of metal ions indicates that the effluents contain a lower concentration of Ag and Mg ions as compared to World Health Organization permissible limit of < 100 ppb (Ag). The biosynthesized Ag-MgO nanocomposite exhibited an enhanced antibacterial activity synergistic effect against E. coli than Ag and MgO nanoparticles, thus, proving to be a potential disinfect material against common pathogens in water treatment. Chapter 5 presented the biosynthesis, characterization, and assessment of simultaneous fluoride and pathogen removal potential in aqueous solutions of a multi-layered Ag-MgO/nanohydroxyapatite (Ag-MgOnHaP) composite. The successful incorporation of Ag-MgO into nanohydroxyapatite (Ag-MgOnHaP) sorbent via an in-situ solution-gelation (sol-gel) method was ascertained from UV-visible absorption spectrum bands at 290 and 440-378 nm typical of MgO and Ag nanoparticles combination in Ag-MgOnHaP composite. FTIR analysis showed the main surface functional groups involved to be –OH, C=N, carbonate and phosphate species on the backbone of Mg-O-Mg vibrational mode. The hydroxyl and amine groups indicated the interaction of a variety of metabolites components present in citrus peel extract as bio-reductive compounds associated with the Ag-MgO and also in fluoride ion exchange. SEM, TEM images and XRD analysis showed a well-dispersed discretely embedded layered-spherical Ag-MgOnHaP nanocomposite without any form of agglomeration after ultrasound exposure ranging in size from 20 to 100 nm with an average mean particle size diameter of 16.44 nm. The high purity of the synthesized Ag-MgOnHaP nanocomposite was confirmed by the presence Ag, Mg and O impregnated on the nanohydroxyapatite template from EDS spectrum analysis. Batch sorption studies using the nanocomposite under different experimental parameters were conducted and optimized. Equilibrium fluoride adsorption capacity of 2.146 mg/g at 298 K was recorded with more than 90% fluoride removal at optimized conditions of 60 min, 10 mg/L initial F- concentration, 0.3 g/L dosage, and pH 6 at 250 rpm. pHpzc of Ag-MgOnHaP nanocomposite was established to be 8. The equilibrium data were best fitted to the Freundlich isotherm model and followed the pseudo-second-order kinetics model at room temperature. The presence of competing anions such as Cl−, NO3−, does not have an impact on percentage fluoride uptake efficiency, but SO42− and CO32− reduce the F- removal efficiency. Moreover, as the concentration of the co-anions increased, fluoride adsorption uptake decreases. The biosynthesized nanohydroxyapatite incorporated Ag/MgO nanoparticle adsorbent (Ag-MgOnHaP) showed strong antibacterial activity against Escherichia coli and Klebsiella pneumonia when compared to hydroxyapatite alone. The presence and interaction between the Ag, MgO nanoparticles with the respective bacterial genomes was suggested to have accounted for this bioactivity. The synthesized Ag-MgOnHaP sorbent was found to portray a better sorption capacity compared to other adsorbents of similar composition in the literature and could be successfully regenerated with 0.01 M NaOH with fluoride removal of 74.24% at the 4th cycle of re-use. The impregnation of metal-metal oxide nanoparticles on sustainable natural biopolymers from waste products was presented in Chapters 6, 7 and 8. The use of these sustainable natural biopolymers (chitosan and cellulose) was targeted with more emphasis on surface functionalization, improved structural diversity and improved specific surface area with the sole aim of increasing the adsorptive capacity of fluoride ions as well as antimicrobial properties. The selected polymers were chosen because of their biodegradability, viii non-toxicity, renewability, selectivity and abundance in nature, which makes them promising starting materials for the purpose of sustainable water treatment. Chapter 6 presents the successful sol-gel biosynthesis, characterization, potential application for fluoride and pathogens removal from aqueous solution using Ag-MgOnHaP embedded on a chitosan polymer backbone (AgMgOnHaP@CSn) sorbent material. The overall formation of the AgMgOnHaP@CSn nanocomposite from different surface functionalization precursors and phases were supported by the various characterization methods such as UV–vis spectroscopy, SEM-EDS, FTIR, TEM, and Brunauer–Emmett–Teller (BET) techniques. Batch fluoride sorption experiments were conducted to assess fluoride uptake efficiency through optimization of several operational parameters such as contact time, adsorbent dosage, initial pH and co-competing anions. The antimicrobial activity of the synthesized AgMgOnHaP@CSn nanocomposites was also determined. The presence and bio-reduction processes of both Ag and MgO chemical species due to the interaction and coordination of bonds within the bioactive functional species of the polymer matrix was confirmed by the emergence of a sharp peak appearing at around 290 nm to a broad plateau plasmon absorbance above 440 nm on the AgMgOnHaP@CSn nanocomposite. FTIR analysis further supported the presence of the main bioactive functional species to be –OH, –NH2 CO32−, PO43-, Mg–O-Mg amongst other groups on the material surface. SEM and TEM displayed homogeneously dispersed particles within the aggregated biopolymeric composite with a diameter ranging between 5-30 μm. Pore sizes were observed to be in the micro-mesoporous range with an average size of about 35.36 nm and a pore diameter of 33.67 nm. The optimized conditions were as follows: 30 mins contact time, a dose of 0.25 g/50 mL, adsorbate concentration of 10 mg/L F-, initial pH 7 while adsorption capacity decreases with increase in temperature. AgMgOnHaP@CSn composite has a pHpzc value of ≈ 10.6 and the maximum sorption capacity was established to be 6.86 mg/g for 100 mg/L F- concentration at 303 K. The effect of co-existing anions was observed to be of the following order: Cl- < NO3- < SO42- << CO32-. The fluoride sorption experimental data was well described by Langmuir adsorption isotherm while the sorption reaction mechanisms were diffusion-controlled and followed the pseudo-second-order sorption model. F- sorption process could best be described as a combination of ligand exchange, electrostatic attraction, and improved structural surface modification. The antimicrobial susceptibility analysis through the zone of inhibition (mean and standard deviation) showed the potency to pathogens of the following order: Staphylococcus aureus > Escherichia coli. Chapter 7 gives an insight into the development of cellulose nanofibrous matrix (isolated from saw-dust) decorated with Ag-MgO-nanohydroxyapatite (CNF-AgMgOnHaP) and its application in fluoride and pathogen removal from contaminated water. The synthesized CNF-AgMgOnHaP, unlike the cellulose nanofiber, showed characteristic absorption bands in UV–vis spectroscopy between 270-290 nm typical of MgO together with a broad band around 420 nm associated with the characteristic of silver nanoparticles. FTIR spectrometry suggested the presence of nanohydroxyapatite (nHaP) and MgO species impregnation within the CNF matrix. SEM, TEM, XRD, and EDS analysis showed a well-established structural and morphological modifications between cellulose nanofiber alone, biosynthesized CNF-AgMgOnHaP and fluoride sorbed CNF-AgMgOnHaP nanocomposite. A granulated aggregation of micro-mesoporous particles with an improved BET surface area of 160.17 m²/g was developed. Optimum fluoride sorption capacity was 8.71 mg/g for 100 mg/L F- solution at 303 K. F- sorption capacities decreased as the operating temperatures increases. Optimum F- removal of 93 % was achieved at optimum conditions established: pH 5, solid/liquid ratio of 0.25 g/ 50 mL, 10 mg/L F-, contact time 10 min, temperature 25 ± 3 °C and shaking speed of 250 rpm. Percent F- removal decreased with increasing initial adsorbate concentration. The pHpzc value of the CNF-AgMgOnHaP occurred at ≈ 4.7. Co-existing ions were observed to have an effect on the adsorption of F- in the following order: NO3- < Cl- < SO42- <<CO32-. Equilibrium fluoride sorption onto the CNF-AgMgOnHaP was best described by non-linear Freundlich isotherm model across all the operating temperatures. The linear Dubinin-Radushkevvich (D-R) model for F- sorption energies were in the 3.54 – 4.08 kJ/mol across all operating temperature. This suggested the physical adsorption mechanism processes were involved in the F- uptake by the CNF-AgMgOnHaP sorbent. The overall kinetic results indicated that the mechanisms not only depend on the pseudo-second-order process but were also governed by mass transfer of the adsorbate molecules across the CNF-AgMgOnHaP surface. The thermodynamic parameters revealed that the sorption process of F- onto CNF-AgMgOnHaP was endothermic and spontaneous at the sorbent/solution interface. The regeneration-reuse study showed that the synthesized adsorbent can be reused for a maximum of 5 adsorption-desorption cycles using Na2CO3 and NaOH as regenerants. Overall surface chemistry by XPS, FTIR, EDS as well as sorption isotherm and kinetic models analysis suggested that both physical and chemical adsorption processes were involved in the fluoride uptake by CNF-AgMgOnHaP nanocomposite. The observed zone of inhibition demonstrated that CNF-AgMgOnHaP adsorbent possesses antibacterial activity against all the bacterial strains in the following order: E. Coli > S. aureus > K. pneumonia. The antibacterial potency increased with increasing sorbent concentration. In chapter 8, Defluoridation and antimicrobial activity of synthesized cross-linked cellulose-chitosan impregnated with the developed nanomaterial (AgMgOnHap) are presented. The before and after fluoride sorption by the synthesized CECS@nHapAgMgO nanocomposites were characterized using several physical and chemical techniques which include, BET, SEM-EDS, TEM, XPS, XRD, and FTIR. The overall batch fluoride sorption processes and adsorption capacity through optimization of different experimental sorption parameters, sorption isotherms, and kinetic mechanisms as well as antibacterial potency were studied and reported. SEM and TEM analysis showed densely irregular multiple-layered structures, homogeneous deposition of the AgMgOnHaP on the polymeric matrices. Equilibrium fluoride sorption capacity on CECS@nHapAgMgO sorbents showed an increased affinity of 26.11 mg/g for 150 mg/L F- solution at 313 K.at optimized conditions of 40 min contact time, dosage of 0.3 g and pH of 5. The pH point of zero charge was found to be 7.27. The reaction pathway model sequence of fitness follows the order Pseudo first order < Elovich < Pseudo-second order kinetic model while intra-particle diffusion model and mass transfer of fluoride molecules from the external surface onto the improved pores of the adsorbent were found to be involved in the rate-controlling step. Although both non-linear Langmuir and Freundlich isotherms showed appropriate trends in the F- sorption process, the adsorption isotherm data were better fitted to the non-linear Freundlich isotherms models, suggesting stronger heterogeneous adsorption onto the active binding sites of the CECS@nHapAgMgO surface. The fluoride sorption was observed to be a favorable process across the operating temperatures. Temkin heat of sorption (BT) and the mean free adsorption energy (E) of the D-R isotherm model was within the range of 0.68-3.39 J/mol and 1.58 -7.45 kJ/mol respectively. The fluoride sorption process was observed to be temperature-dependent; while adsorption capacities (Qm) and Temkin heat of sorption (BT) increased with increasing temperature, D-R Mean free sorption energy (E) decreased at higher temperatures. The thermodynamic analysis demonstrated that fluoride sorption on the CECS@nHapAgMgO surface was exothermic, feasible and spontaneously inclined with a decrease in the degree of randomness at the sorbate-sorbent interface. The influence of co-existing anions on fluoride removal exhibited the following trend Cl−< NO3− <SO42- << CO32- <<HCO3−. The practical and economic viability, potential for regeneration showed its reusability up to 3 cycles with water and Na2CO3 as regenerants. The potential ability of CECS@nHapAgMgO to disinfect both gram- positive and gram-negative water bacterial was confirmed by the zone of inhibition and Minimum Inhibitory Concentration (MIC) measurements. The observed values showed the inhibitory efficiency in the following order: S. aureus > E. Coli > K. pneumonia where the MIC values of 20 μg/mL were recorded for S. aureus and E. Coli respectively and 10 μg/mL for K. pneumonia. Lastly, the applicability of the sorbents was tested with a field water sample collected from a high fluoride borehole water from a local village (Lephalale Municipality of Limpopo province, South Africa). The before and after analysis showed the excellent potential of CECS@nHapAgMgO sorbent in removing fluoride. In conclusion, the successful surface functionalization synthesis of these improved surface area hybrid nano-sorbents supported by the different morphological techniques was found to be effective in creating more surface-active binding sites for fluoride adsorption and disinfection of waterborne pathogens from aqueous solution. The originality of this developed sorbent lies firstly, in the ability to simultaneously remove both chemical and biological water pollutants; secondly, the use of biodegradable, eco-friendly and non-toxic abundance wastes raw materials to develop a water purification material and in solving waste management issues was a key factor towards environmental sustainability. Above all the developed materials were established to possess superior fluoride adsorption capacity when compared to other reported sorbent materials. Lastly, the project findings /innovation will contribute to Sustainable Development Goals (SDG) 3 and 6, aimed at improving clean water supply and health of the communities and the world at large. However, the following recommendations were made following the findings from this study: 1) In order to increase the surface area to volume ratio, greater selectivity, porosity, and mechanical stability of the polymers as well as size-exclusion mechanism without a large energy penalty of the microbes and fluoride ion for effective water treatment, a more effective and an enhanced multifunctional, multi-layer nanofibrous hybrid sorbent through electrospinning techniques should be considered for future work, 2) More studies on the mode of actions and morphological changes in the pathogens leading to the cell death through the influence of the nanocomposites should be further explored, 3) Application of this advanced technology vis-à-vis other biomaterials to generate filter membrane towards efficient microbial removal and deflouridation is a great challenge worth looking at, 4) Lastly, materials developed in the present study should be modeled, tested and fabricated at the point of use for fluoride and pathogen removal at household level. / NRF
9

An investigation into factors increasing contamination risk posed by fuel storage facilities and concomitant methods to mitigate these risks.

Pfotenhauer, Torin. 23 September 2013 (has links)
Light Non-Aqueous Phase Liquids (LNAPLs) are used throughout the world for numerous applications, the most well-known being automotive fuels, such as petrol and diesel. The widespread production, distribution, storage and use of LNAPLs results in the ubiquitous occurrence of spillage to ground (Geller et al, 2000). Considering the hazardous nature of most LNAPLs due to their explosive and toxic characteristics, releases of LNAPLs to ground have well documented human health and ecological consequences. The occurrence of leaking underground and above-ground storage tanks at service stations and consumer installations is a common cause of contamination; and is described in literature for various countries of the world (Dietz et. al., 1986; Moschini et al, 2005; Mulroy and Ou, 1997; Harris, 1989; The Institute of Petroleum, 2002). Little failure data are however available for the South African context. In addition to this, data concerning the location and characteristics of sites storing LNAPLs in South Africa is similarly scarce. The study analysed data from three sources, namely the eThekwini Fire and Emergency Services data, GIS data and data from a local consultancy, in order to determine whether certain factors increased contamination risk posed by these facilities. The results indicated that contamination may be a result of numerous factors, but primarily line and tank failure. The type of installation was also found to have a significant influence on whether a site would be contaminated or not. In addition to the above, the results indicated that certain circumstances increase the severity of loss. The results indicated the need for more investigation to be performed into contamination as a result of LNAPL loss to ground, and the need for protective measures to be implemented for high risk sites where the likelihood and severity of a potential loss is high. Focus should then be centred on the probability of failure of non-ferrous pipework and GRP tanks to ensure adequate protective mechanisms are in place in the event of a failure of this newer infrastructure. In addition, a review of regulatory control of LNAPL storage in South Africa and the eThekwini Municipality, with reference to the international context, indicated the need for a specific department within the local government structure that manages LNAPLs with the objective of reducing contamination incidents. The continued use of underground storage of LNAPLs will always present a risk of failure/contamination due to the unseen nature of the installations and related infrastructure. It is this risk that requires regulatory management. Details of contaminated sites in South Africa should be within the public domain. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

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