https://repository.biust.ac.bw/handle/123456789/30 The community is made up of electronic theses and dissertations produced by post graduate students of Botswana International University of Science and Technology( BIUST) 2026-06-06T01:39:16Z https://repository.biust.ac.bw/handle/123456789/747 Physiological and ecological responses of the larger grain borer, Prostephanus truncatus (Horn), to changing environments: implications for its population dynamics and management Mlambo, Shaw The rapid change in environments owing to anthropogenic activities and climate change has reshaped the geographical range and status of different insect pests of economic importance. Further, the mechanisms by which conspecific and allospecific species phenotypes vary and how that influences species adaptation in novel environments are poorly understood. The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is one of the quarantine pests which poses serious threats to stored maize and dried cassava tubers and has continued to expand its ranges in Africa. However, physiological and ecological data required to map the dispersal pathways and factors limiting geographical distribution of such pests in diverse environments are largely understudied. A combination of literature reviews, field (questionnaire survey and pest monitoring through pheromone baited traps) and laboratory studies were conducted to determine (i) the presence and geographical range of P. truncatus in Botswana (Chapter 2), (ii) local farmers’ knowledge, practices and perceptions on cereal postharvest management including the efficacy of current storage technologies against P. truncatus (Chapter 3), (iii) the drivers and implications of P. truncatus and Spodoptera frugiperda biological invasions in Africa (Chapter 4), (iv) effects of increasing temperatures on the transgenerational (Chapter 5) and intergenerational (Chapter 6) responses of P. truncatus, (v) feeding rates and effects of maternal host preferences on progeny fitness (Chapter 7) and (vi) effects of intra- an interspecific competition on P. truncatus’ physiological and ecological performance (Chapter 8). Standardised physiological (critical thermal maxima [CTmax], critical thermal minima [CTmin], heat knockdown time [HKDT], upper lethal temperatures [ULTs]) and ecological performance (% maize grain damage, % grain weight loss, progeny production, % insect feeding dust) traits were measured under controlled temperature and relative humidity conditions in climate chambers. Results confirmed, for the first time, the presence of P. truncatus in Botswana, but its distribution is still patchy. Although the pest seems not yet well-established inland, the current farmer practices dominated by use of botanical pesticides makes them vulnerable if P. truncatus was to become dominant. Lack of information and awareness of the dangers that P. truncatus pose and lack of improved grain storage facilities further expose local smallholder farmers to this threat. Laboratory assays showed behaviourally plastic responses to increased temperatures and varying xvii hosts. First, trait-dependent thermal plasticity responses are passed on to offspring through transgenerational and intergenerational plastic physiological responses which mediate P. truncatus progeny fitness. Alongside, maternal experiences or decisions by offspring through transgenerational plasticity act as signals for adaptation to a host. Ecological performance of P. truncatus was high at 25 and 30℃ in response to temperature suggesting high pest activity under elevated temperature conditions. This may mean that P. truncatus poses serious threats to food security with increasing temperatures under climate change. However, damage was highly suppressed at higher suboptimal temperatures of 35℃. Prostephanus truncatus failed to survive on mopane wood suggesting that the wood may not be a suitable host for the pest. The study shows P. truncatus physiological adaptative responses to changes in the environment and climate and calls for concerted efforts to monitor the pest inland, forewarn farmers of the dangers of the pest and train them on appropriate efficacious grain storage technologies to manage the pest. This work contributes insights into the ecology and physiology of P. truncatus, which are important in developing models for early warning and control, as well as integrated national and regional pest management strategies against the pest. Thesis (PhD Biological Sciences and Biotechnology)--Botswana International University of Science and Technology, 2025 2025-09-01T00:00:00Z https://repository.biust.ac.bw/handle/123456789/746 Modelling and optimisation of ultra-fine grinding of Copper Sulphide ore. Moyo, Nkosilamandla The global demand of base metals has been steadily on the rise since the fourth industrial revolution, and in the past 20 years, the rise has sharply increased, driven by the paradigm energy transition from traditional fossils utilization to green sustainable technologies. Base metals play are key in these sectors particularly in structural developments, smart materials for the health sector and as key elements in the renewable energy storage facilities, energy transmission and in the automotive industry. Copper is an essential base metal, particularly in driving energy transition and electrification, in electronics and technology advancements, in urbanization and infrastructure growth etc. For instance, the utilization of copper in electric vehicles is reported as 2-4 times that of internal combustion engine cars therefore its demand has been steadily on the rise. Mining sector remain crucial to the development of Southern African economies, Botswana having its economy being driven by the diamond industry, however, observing the dangers of relying on diamonds, the government has since set its sights towards diversification of its industrial sector. This starts with the prominent mining sector, by promoting and resuscitating once operational base metals mines, particularly reviving the copper industry, which currently is the second mined mineral in the country. Copper reserves in Botswana are predominantly sulphide ores therefore they have been beneficiated through the pyrometallurgy route. However, with the depletion of rich ore bodies, and the imposed environmental laws set to reduce climate effects resulting from anthropogenic emissions, the traditional route has not been favorable anymore. This led to the country exporting its resources solely in concentrate form, losing some valuable revenue in that transaction, therefore the need to extract, separate and purify base metals from these concentrates is more beneficial for the nation. Hydrometallurgy technologies developed in the late 20th century to the beginning of the 21st century, e.g. the Activox, CESL technologies, have demonstrated effective extraction, countering the traditional drawbacks of sulphide mineral leaching. This work looks therefore into adoption of the Activox technology for the efficient beneficiation of copper in Botswana. The Activox technology is parent to two daughter processes, the ultra-fine grinding process and the oxidative pressure acid leaching. The scope of this work dwelt on the primary process, the ultra-fine grinding process, an energy intensive process, for the mechanical activation of the mineral surfaces for effective extraction of copper form its mineral matrix. Due to equipment constraints faced, the work was conducted using a 5litre laboratory ball mill, with the aim of modelling and optimizing the process, i.e. the product grind quality and energy consumption. This was achieved through hybrid modelling, i.e. machine learning modelling surrogated with statistical modelling. The StatEase Design Expert software was utilized for statistical modelling while the Artificial Neural Network and Artificial Neuro-Fuzzy Inference System packages in Matlab 2021a were used. The UFG process is highly complex, as evidenced by increasing research conducted on it, assessing the impact of various factors on its efficiency, both in grinding extent and energy consumption, e.g. rotational speed, powder filling, media type, media size, media filling, solids/liquids ratio and use of viscosity modifiers etc. In this study, the effects of grinding media size, milling speed, milling time and media filling ration were tested experimentally on the efficiency of the process on both counts. The outright realization herein was that media size greatly impacts the process, and this aligned with reports from literature with the generalisation for machine learning. particle size grammar xvii | P a g e that fine media best suits fine milling, and the effect of this was also noticed in energy consumption as lengthy milling periods were needed with coarse media for effective grinding compared to fine media. Further analysis of the observations from experiments using fine media showed that the base factor of importance was the media filling ratio, from which mill speed and milling time impacts relied on. This was a positive realisation as it highlighted the potential of improved production rate at maximum filling of the media, subject to optimisation of this filling rate using the attainable region as thus recommended in this work. Modelling of the processed led to effective optimisation, firstly after realisation of 20μm being the optimum P80 grind size, compared to the technology’s 10μm from characterization. As such, the hybrid modelling exercise was effectively done, with validation results when using a different sulphide ore, of 97.34% for P80 predictions using the ANFIS technique while that of SE at 85.71% using the ANN technique. The ascertain the validity of this optimisation, a cost benefit analysis was conducted, and it proved that with optimizing the process from 10μm to 20μm, a 24.45% energy saving could be realized. This translates to a massive saving especially in a process that is energy intensive as such this could lead to the feasible adoption of the technology, leading to reviving the economy, creating more employment opportunities. To fully stamp on this optimisation, a comparison of the leaching at 10μm and 20μm is required to ascertain the extraction efficiency as validation of the entire work. 2025-06-01T00:00:00Z https://repository.biust.ac.bw/handle/123456789/745 Corrosion inhibition mechanism and performance of Sclerocarya Birrea (Marula) leaf extract in acidic and seawater environments Shathani, Phenyo Natural materials, especially derived from medicinal plant extracts, which are renewable, biodegradable, and highly effective, have been the core subject of research lately due to the growing demand for sustainable and environmentally benign corrosion inhibitors. This dissertation explores the corrosion inhibition potential of Sclerocarya birrea (Anacardiaceae .Rich) Hochst. subsp. caffra (marula) leaf extract for mild steel, API X42 pipeline steel and Aluminium (AA 1100) alloy in 3.5 % NaCl and 1 M H2SO4 corrosive environments. These materials are often utilized in petrochemical, water transportation and construction industries where these corrosive environments are prevalent. Initially, we used FTIR, UV-Vis, and GC-MS techniques alongside preliminary phytochemical screening to identify all the phytochemical compounds, bioactive compounds, and functional groups that will aid in suppressing corrosion. The mechanisms and effectiveness of the Sclerocarya birrea ethanolic extract inhibitor were assessed by a multifaceted approach expending weight loss analysis, thermodynamics and adsorption studies, electrochemical impedance spectroscopy (EIS) analysis, open circuit potential (OCP) , potentiodynamic polarisation (PDP), dense functional theory (DFT) , Monte Carlo (MC) simulations, and surface analysis such as X-ray diffraction (XRD) and Raman spectroscopic analysis. These techniques offer a thorough comprehension of the chemical interactions, adsorption processes, and inhibition efficiency that underline the leaf extract's ability to impede corrosion. When comparing the uninhibited samples to the inhibited ones, the weight loss results for the metals revealed significant corrosion for blank exposed samples in both corrosive media. As the inhibitor’s concentration increased, the inhibition efficiencies also increased, suggesting that the inhibitor's effectiveness was dose dependent. Sclerocarya birrea inhibitor served as a mixed-type inhibitor, lowering both anodic and cathodic processes on the metal surface, according to electrochemical investigations such as EIS and PDP. With increasing inhibitor concentration, EIS measurements indicated a decline in double-layer capacitance (Cdl) and an increase in charge transfer resistance (Rct) , demonstrating the inhibitor's ability to generate a protective barrier. Stable potential values during prolonged exposure periods demonstrated that a stable protective film has been formed on the metal surface, as confirmed by OCP measurements. Thermodynamic parameters determined by adsorption isotherms indicated that physisorption is the dominant adsorption mechanism of the inhibitors on the metal surfaces. The best fit in both 3.5 % NaCl and 1 M H2SO4 corrosive solutions is given by both the Langmuir and Temkin adsorption isotherm models, which suggests a monolayer adsorption mechanism. With values compatible with physisorption interactions rather than chemisorption, the computed Gibbs free (ΔG) energy of adsorption validates the inherent spontaneity of the adsorption process. The molecular interactions between the active ingredients in the inhibitor and metal surfaces were further explained by computational insights from DFT and Monte Carlo simulations. DFT simulations determined which functional groups in the leaf extract were responsible for adsorption; they revealed that some of these groups had a high capacity to donate electrons, which made it easier for them to interact with the metal surface. By visualizing the arrangement of extract molecules on the metal surface, simulating the adsorption process, and quantifying adsorption energy values that supported the experimental results, Monte Carlo simulations enhanced these findings. Additional layers of verification were offered by structural and spectroscopic examinations from Raman spectroscopy and XRD surface analysis. The inhibitor's significance for surface protection rather than bulk alloy change is confirmed by XRD data obtained, which also confirms that the crystalline structure of inhibited metal samples is substantially intact. Shifts in distinctive peaks linked to the mild steel, API 5L X42 pipeline steel and AA 1100 metal surfaces were revealed by Raman spectroscopy, signifying the development of a thin protective organic layer. The development of a physiosorbed layer and the involvement of functional groups from the inhibitor, such as C-H, C=C, OH, and C-O, in the inhibitory process were further complemented by changes in Raman spectrum characteristics. Overall, the results obtained from this investigative study demonstrated that Sclerocarya birrea ethanol extracted leaf extract exhibits outstanding inhibitory efficacy in both acidic (1 M H2SO4 ) and simulated seawater (3.5 % NaCl) environments, proving its potential as a mild steel, API X42 pipeline steel and aluminium (AA 1100) potential inhibitor that is both economical and sustainable. This study adds to the expanding corpus of research on plant-based corrosion inhibitors by shedding light on the structural effects, thermodynamic behavior, and molecular interactions of natural inhibitors on different metals. The findings imply that Sclerocarya birrea inhibitor’s eco-friendliness and effectiveness in combating corrosion render it a strong contender for substituting synthetic inhibitors, which are frequently linked to human health and the environment threats. The significance of multidisciplinary approaches in corrosion science is emphasized in this dissertation, which merges computational modelling and experimental approaches to clarify the complex dynamics of corrosion inhibition and advance the creation of sustainable materials that can be adopted for industrial use. 2025-06-01T00:00:00Z https://repository.biust.ac.bw/handle/123456789/744 Evaluation of Morupule coal mine’s Block 2 Morupule main seam for the prospects of new coal mine development and coal production Mamba, Nonduduzo B. The coal mining industry plays a crucial role in global energy production, and the need for accurate and updated information about coal deposits is essential for effective resource management. This study focused on the re-evaluation of the Morupule Coal Mine block 2 (MCM2) that was initially evaluated over 50 years ago. The aim was to utilise the change in methodologies and advancement in technology over the years, leading to more accurate and reliable results. By re-evaluating the MCM2 coal block and incorporating the advancements in methodologies and technology, this study provided an updated understanding of the coal deposit focusing on the Morupule main coal seams’ potential and feasibility for future mining. Findings rendered the project both technically and financially feasible at the current economic condition based on the estimated coal resource and cost estimates, respectively. The overall in-place coal resources of the Morupule main seam were estimated to be 812 million tonnes (Mt). This resource was further broken down as 715 Mt Measured Resource and 97 Mt Indicated Resource. Mining method anticipated is open cast mining using a dragline in combination with drill and blast techniques, roll-over mining where progressive rehabilitation is conducted as mining takes place. The proposed opencast mine has a production capacity of 3 million tonnes per annum, requiring capital investment ofUS$57 million and targeting a coal selling price of US$100 per tonne, with a potential net present value of US$1.094 billion. 2024-11-01T00:00:00Z