Faculty of Science, Engineering and Agriculture

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Browsing Faculty of Science, Engineering and Agriculture by Author "Akintola, George Oluwole"

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    ItemOpen Access
    Evaluation of major clay deposits for potential industrial utilization in Vhembe District Municipality, Limpopo Province of South Africa
    (2018-05-18) Akintola, George Oluwole; Amponsah-Dacosta, F.; Mhlongo, Sphiwe Emmanuel
    Vhembe District has several clay deposits which are traditionally use for clay products such as burnt bricks without taking into account the chemical and mineralogical characteristics of clay being used. The ever-increasing market demand for these clay products cannot be met with the traditional method of clay utilization due to the paucity of scientific information on properties of the clay in the area. Consequently, there is a need to gain better understanding of the characteristics of the clay in Vhembe District and to establish the suitability of the variety of clay for different purposes. The current study was undertaken to better understand the compositional relationship between the clay deposits and surrounding rocks present in the study area. It further aimed at characterizing the clay deposits on the basis of chemical, mineralogy, physical, mechanical, thermal and micro structural properties with a view of evaluating the clays for possible industrial use. A total of thirty-nine clay and rock samples were collected from thirteen different locations across the Vhembe District. Thirteen representative samples from each location were obtained after thorough mixing until homogenization was attained and then quartered for subsequent analyses. The mineralogical and chemical characteristics of the clay and rock samples were determined using XRD and XRF respectively. Thin-sections of the rock samples were prepared and examined under petrographic microscope to better understand the mineral assemblages present in the rocks. The thermal and micro structural properties of the clays were determined using DTA-TGA and SEM analyses and the physical properties which include colour, cation exchange capacity (CEC) and soil pH were assessed. The particle distribution and Atterberg limits tests of the clay samples were also conducted in order to establish their mechanical properties. The petrographic results showed that the clay deposits exhibited an intense weathering and sedimentation processes which incorporated detrital minerals from the surrounding rock units. The rock units which include basalt, granodiorite, gneiss and quartzofeldspathic gneiss were found to be differentiated from subalkaline and/or tholeiitic magmatic composition. Although the value of SiO2 content in rock samples was higher when compared with clay samples, it indicated an ongoing desilicication and allitization processes. The high values of chemical index of alteration (CIA), low values of K/Cs (<6200), Ce* normalized value and higher values of LILE enrichment in the clay deposits indicated oxidizing environments during period of deposition. v The mineralogical composition of the studied clayey deposits showed that smectite (8.25 - 29.32%), kaolinite (14.91 - 59.26%) and chlorite (5.94 -16.54%) were present as clay minerals although associated with other non-clay minerals such quartz, plagioclase, talc and geothite. The chemical composition results revealed high silica and alumina content in most studied clay samples. Their fluxing oxides which include K2O, Na2O, CaO, and MgO, varied slightly from 0.06% to 1.78% in abundance while the Fe2O3 and TiO2 contents in most samples averages at 9.2% and 1.3% respectively. The plasticity index of the studied deposits ranged from 9.50 to 62.00% while liquid limit ranged from 31.34 to 73.62%. The microanalysis using SEM indicated that the microstructure framework of most studied clay exhibited a porous skeleton structure owing to numerous tiny voids. The composite results of SEM and CEC analyses suggested their possible application in water filter and chemical fertilizer industries since they provided passage for water and soil cations transmission. The particle size distribution demonstrated that the studied soils have clayey silt texture with wide range coverage of the well graded and sorted particle sizes. Compressibility and plasticity properties were found to be high in Mukondeni, Mashamba-1, Mashamba-2 and Mashamba-3 clay samples. The thermal behavior of Mukondeni, Mashamba-1, Mashamba-2 and Mashamba-3 samples showed relatively high shrinkage (>9%). The high shrinkage percentage suggests the preponderance of smectite minerals. Other samples which are rich in kaolinite and chlorite minerals exhibited low shrinkage (<2%). The drying trends of the studied clay suggest their suitability for fast drying processes like soft and hard refractoriness, sanitary wares and ceramics. Empirical assessment of most studied clay showed their suitability for pottery-making and manufacturing of roofing tiles and masonry bricks.
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    ItemOpen Access
    An integrated approach of determining shale gas potentiality of carbonaceous shale of the Permian Tuli Basin, Limpopo Province of South Africa
    (2022-11-10) Akintola, George Oluwole; Amponsah-Dacosta, F.; Rupprecht, S. M.; Mhlongo, S. E.
    Shale gas displays signs of future potential for energy generation. Apart from the fluctuating prices of liquid fuel and energy resources, the recent national load shedding of electricity supply is probably the most obvious sign of the energy security crisis in South Africa. To expand energy security, there is a need for an energy mix to complement existing sources. Despite extensive studies on stratigraphic, sedimentology, and coal investigations, the source rock potential of organic-rich shale for gas generation remains elusive in the Permian Tuli Basin. As a result, this research aims to investigate the shale gas potentiality of the carbonaceous shale of Madzaringwe and Mikambeni Formations in the Tuli Basin of Limpopo Province, South Africa. A total of Twenty (20) representative core samples are selected to determine the whole rock major and trace elements using X-ray fluorescence (XRF) and Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) respectively. In addition to the mineralogical characterisation using X-ray diffraction (XRD), the functional groups of organic compounds in studied samples are identified using Fourier Transform Infrared Spectrometry (FTIR). Furthermore, the porosity networks of the shale samples are determined using the Scanning Electron Microscopy-Energy Dispersive X-Ray Analysis (SEM-EDX). Lastly, the total organic carbon content (TOC), Kerogen type and thermal maturity of the studied samples to generate hydrocarbon are determined using the Rock-Eval 6 programmed pyrolysis. The major oxides results indicate a varying amount of Al2O3 (19.37–20.32%), CaO (0.20-0.22%), Fe2O3 (0.85-0.94%), K2O (1.59-1.66%), MgO (0.25-0.28%), Na2O (0.12-0.15%), P2O5 (0.04%), SiO2 (50.37-51.90%), TiO2 (0.69-0.73%) in the studied Mikambeni samples. The compositional trend of other major components is comparable, except for the lower average value of loss-on-ignition (LOI), which averages 15.04% in the Madzaringwe shale, indicating a lower TOC content. The average LOI values of Mikambeni shales (25.02%) show a higher TOC content which correspond to the actual TOC test. The elemental ratio K2O / Al2O3 (0.08) of the studied samples showed values ≤ 0.5, which suggests a moderately mature shale since a significant amount of Al2O3 is typical of immature sediments. The LA-ICP-MS analysis reveals trace elements Ba (294.16-560.88 ppm), Zn (57.46-121.63 ppm), Zr (189.02–341.72 ppm), Rb (67.69-102.26 ppm), V (81.24-156.88 ppm), Sr (92.02-344.91ppm), Cr (47.50–86.66 ppm), Pb (11.25-35.22ppm) in all studied samples. The presence of Ba suggests the dissolution of mineral barite in the black shale by the action of sulphate-reducing bacteria while Zn indicates paleo-productivity of abundant organic matter. Furthermore, Mo concentration > 2.5ppm of Mikambeni, suggests a marine sediment input in the Mikambeni samples apart from terrigenous sources in all studied samples. The interpretation of the anoxic environment is consistent with the V/(V+Ni) average value of 0.84ppm which exceeds the 0.54 limit for anoxic conditions for all studied samples. The XRD analysis shows the presence of montmorillonite, mixed illite/smectite (I/S), illite, chlorite, and non-clay minerals such as dolomite, albite, microcline, pyrite, and quartz in the studied samples. The presence of pyrite suggests activities of sulphide-reducing bacteria on parent organic matters to generate biogenic gas. The presence of illite and chlorite suggests illitisation and chloritization at greater depths of Madzaringwe samples, suggesting a high thermal alteration level for sediments. The functional group of all studied samples shows infrared absorption peaks between 2800 and 3300cm-1 wavelength attributed to an aliphatic C-H stretching vibrations. The sp2 C-H hybridization found with absorption peak between 3000-3100 cm-1 wavelength indicates the aliphatic methane gas stretching of methyl and methylene vibration. Bubble-like porosity resulting from organic matter decomposition typifies most of the studied samples, suggesting a gaseous release from organic matters. However, isolated-irregular pattern of matrix-mineral pores are displayed apart from preferred-oriented linear pores exhibited by the micro-fracture pore types in all studied samples. The EDX elemental compositions indicate intragranular grains composed of quartz, feldspars, carbonate, and pyrite minerals to form interconnected matrix. Furthermore, a non-spherical, closely packed polyframboidal-pyrite is observed, having multiple presence of Fe contents on the EDX composition. Thus, this suggests an anaerobic condition that favours organic matter degradation that initiates methanogenesis. The Rock-Eval 6 programmed pyrolysis and TOC of the studied shale samples revealed a TOC content that exceeds threshold limit of 5.0 wt %, indicating an excellent source rock in both formations. The hydrocarbons produced from the thermal breakup of kerogen (S2) ranged from 101.64 to 122.75mg HC/grock with an average value of 115.7mg HC/g rock in the Mikambeni samples. The S2 content of Madzaringwe shale ranged from 15.25 to 16.47 mg HC/g rock averaging at 1.82 mg HC/g rock. The plot of Hydrogen Index (HI) against TOC indicates a mixed kerogen TYPE II-III for the Mikambeni samples and TYPE-III for the Madzaringwe samples, which is gas prone. The maximum temperature, Tmax, corresponding to the peak of hydrocarbon yield (S2) range between 430 to 434°C, averaging at 431.8°C thus indicating a thermally immature source in the Mikambeni samples. On the other hand, the Madzaringwe shale samples yield a thermally mature condensate wet-gas, with Tmax values (464 - 470°C) averaging at 467.2°C. The studied samples have an average Productivity Index (PI) value of 0.1 which indicates a moderately mature source, generating a mixed biogenic-thermogenic gas. As such, the petroliferous indicators of the studied Mikambeni shale generates thermal immature biogenic gas while Madzaringwe shale produces a matured condensate wet-gas in the Tuli Basin.