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Method development for the quantification of rare earth elements in South African monazite by various spectroscopic techniques
No full textA dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Chemistry, to the Faculty of Science, School of Chemistry, University of the Witwatersrand, Johannesburg, 2025The rare earth elements are critical, and their various applications include electronics, the defence sector, manufacturing, renewable energy, technology and the medical sciences. The increasing demand for these critical elements will strain the existing supply chain. There is a major concern that any disruption to the supply chain will negatively impact innovation. Countries worldwide are seeking to secure new reserves, find the material substitutes, and boost the research in recycling electronics that have reached the end of life. Monazite contains critical rare-earth-elements responsible for green energy transition. The bottleneck associated with analysing rare-earth elements in monazite is its refractory nature and associated heavy minerals that do not decompose completely in the sulphuric acid fuming procedure. Furthermore, rare-earth elements have been successfully measured in geological materials employing the sensitive inductively coupled plasma mass spectrometry techniques. Nevertheless, it suffers from a low tolerance of total dissolved solids in matrices such as monazite. While, inductively coupled plasma optical emission spectroscopy suffers from poor sensitivity and matrix removal is often required for accurate rare-earth elements determinations. Extensive research has been conducted on sensitive procedures and efficient sample preparation for trace elements determinations including rare-earth elements. This study aims to develop a method for direct determination of rare-earth elements in monazite. The monazite ore samples were collected from the extractive metallurgy within Mintek for method development for quantification of REEs. Three preparation methods for sample digestion techniques were evaluated. The methods involved the flux fusion method using the lithium metaborate and sodium peroxide respectively and the multi acids digestion with hotplate as the source of heat followed by rare earth elements quantification using both the inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectroscopy. Moreover, the complete sample dissolution was achieved with the flux fusion method while the partial sample dissolution was observed via multiple (repetitive) treatment steps by multi acids digestion method. The total dissolved solids were mitigated, and the matrix effect was eliminated when glass beads were treated (dissolved) in a mixture containing nitric and hydrofluoric acids. The analyte spectrum was often completely obscured by wing overlap and direct overlap of emission lines from interfering elements during-inductively coupled plasma optical emission spectroscopy analysis. In addition, the recoveries for some rare earth elements were suppressed with enhanced spikes for rare earth elements concentration were observed from inductively coupled plasma optical emission analysis particularly from the solution samples digested in alkaline fusion. The inductively coupled plasma optical emission spectroscopy results for the rare earth elements suggest that the sample matrix significantly affects the sensitivity. The method’s validity was tested using a monazite ore-certified reference material. In contrast to the optical emission spectroscopy, the accurate analysis of rare earths from all the digested samples was obtained using the inductively coupled plasma mass spectrometry. The results of the rare earth elements obtained for all digested samples analysed using the mass spectrometry strongly agree with the certified values. The excellent accuracy of the method was realised with the rare earth elements data obtained from quality control samples, and recoveries yield within the range of 90-110%, and the relative standard deviation of 0.2-5.4%. The selectivity and sensitivity of the method were realised with individual rare earths accurately measured in the presence of other interfering elements, as indicated by lower detection of limit ~ (0.0004-0.016 ppm) and limit of quantification ~ (0.0001-0.0290 ppmn). Calibration curve linearity for individual rare earth elements is demonstrated by the correlation coefficient in the range of 0.99 to 1.0. Moreover, multi fusion methods followed by mass spectrometry are futuristic analytical approaches for determining rare earth elements in monazite associated minerals and they can be used interchangeably. In South African context, South Africa should prioritise the development of Rare Earth Elements (REE) extraction and recycling technologies in order to maximise yield, purity, and environmental sustainability, notably through enhanced procedures for monazite-rich deposits. Investing in a circular economy paradigm, such as boosting REE recovery from electronic trash, can minimise dependency on virgin resources and help to create a more sustainable future. To further help the country's green energy transition, the government should fund research into REE-based technologies critical to renewable energy systems such as wind turbines, solar panels, and electric cars. Furthermore, developing regulatory frameworks that ensure responsible mining techniques and monitor the entire REE supply chain will assist to mitigate environmental and social consequences. Additionally, South Africa can enhance its role in the global REE market by collaborating with international partners, leveraging external expertise, and promoting sustainable technologies, thereby contributing to a low-carbon economy.Mintek Science VoteMMM202
Role of remuneration and career development on employee turnover in mines surrounding the Eastern Bushveld Igneous Complex
No full textA research report submitted in fulfillment of the requirements for the Master of Business Administration, in the Faculty of Commerce Law and Management, Wits Business School, University of the Witwatersrand, Johannesburg, 2025This research investigated the impact of remuneration and career development on employee turnover in mining operations in the Eastern Bushveld Igneous Complex (BIC), a critical hub for South Africa’s mineral resources. The study highlighted the high turnover rates among employees with critical skills, which pose risks to operational stability and profitability. It examined how dissatisfaction with remuneration and limited career development opportunities adversely influence employee turnover intent. Using a descriptive quantitative research design, the study surveyed employees with critical skills and human resource practitioners from selected mining operations in the Eastern BIC. Results showed that more than half of respondents had considered leaving their jobs within the past year. Career development emerged as the most significant factor influencing turnover intent, followed by dissatisfaction with remuneration. The findings revealed that although employees value competitive basic salaries, performance- linked incentives significantly affect retention. Similarly, opportunities for professional growth and structured career development paths are critical for retaining talent. The study underscores the importance of fostering supportive leadership and enhancing organisational culture to address turnover effectively. Recommendations include developing robust incentive schemes, providing targeted career development programmes and enhancing leadership practices to improve employee satisfaction and retention. This research provides actionable insights for mining companies to mitigate turnover risks and sustain operational success in the Eastern BIC. Future research should explore these dynamics across broader mining regions and job categories to generalise findings and refine retention strategiesMM202
Investigating the Foraging Behaviour of Entomopathogenic Nematodes Cultured in Vitro
No full textA dissertation submitted in fulfilment of the requirements for the degree of Master of Science, to the Faculty of Science, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2025Synthetic pesticides have provided a cost-effective approach for the control and protection of agricultural and horticultural crops against insect pests and diseases since their introduction and success in the mid-1940s. Despite the noticeable benefits of synthetic pesticides, an inconsiderable amount of evidence has shown that their overuse poses several adverse effects, including the development of resistance, crop contamination and the unconscious reduction of non-target organisms. Therefore, safer yet effective techniques for managing insect pests are required. Insect parasitic nematodes such as entomopathogenic nematodes (EPNs) are widely studied for their use as potential biological control agents (BCAs) against various economically important insect pests. EPNs are classified into three foraging groups namely cruise, ambush, and intermediate foragers which influence their soil depth distribution and host range. Upon their emergence from host cadavers or inundative release into soil, EPNs experience a variety of environmental and host-associated cues which significantly affect their foraging behaviour and, ultimately, their pathogenicity, survival, and persistence. Therefore, understanding the foraging behaviour of EPNs following their exposure to abiotic and chemotactic stimuli is essential for classifying EPNs into foraging groups and their assignment to specific hosts. As such, this study aimed to isolate EPNs from soil samples collected from Mahobong Leribe in Lesotho and investigate their foraging behaviour by exposing the nematodes to abiotic factors and chemical cues that influence their host-seeking behaviour. Nematodes were recovered from collected soil samples and infected Tenebrio molitor cadavers using the soil baiting technique and White trap method, respectively. PCR amplification and Sanger sequencing of the 18S and 16S rDNA regions were used to identify the phylogenetic relationships of the isolated nematode and its potential bacterial symbiont using the GenBank sequence database, respectively. The isolated nematode had a high affinity to Cruznema sp. isolate 734C-1 (OR606776.1), whereas the potential bacterial symbiont had a high affinity to Enterobacter ludwigii strain EN-119 (NR 042349.1). The foraging behaviour of Cruznema sp. NTM-2021 was studied by investigating the influence of soil moisture and the nematode's response to a distal chemotactic cue. After 7 days, insect mortality observed in the 2D sand substrate assays was 0%, 23.3%, 40%, 46.7% and 66.7% for 10%, 12.5%, 15%, 17.5% and 20% soil moisture levels, respectively. This overall trend suggests that insect mortality increases with an increase in soil moisture. After 7 days, the vertical sand column assay revealed that at 10% soil moisture levels, the IJs travelled to a maximum depth of 8 cm and caused <12% insect mortality at this depth. At 12.5% soil moisture, the IJs travelled to a maximum depth of 14 cm and caused >85% insect mortality at this depth. In soil moisture levels ranging between 15-17.5%, IJs reached depths of 32cm, causing >85% insect mortality at all depths along the column. Interestingly, at a soil moisture level of 20%, IJs reached lengths of 26 cm; however, they could only parasitise <15% of the insect larvae, suggesting that higher moisture levels may restrict the vertical dispersal of nematodes. The PF127 gel assay revealed that the IJs of Cruznema sp. NTM-2021 were strongly repelled by prenol, suggesting its use as a distal chemotactic cue. Based on the IJs ability to move to depths of 32 cm and its response to prenol, Cruznema sp. NTM-2021 may be classified as a cruise forager. Overall, the results of this study not only classified the foraging behaviour of a potential entomopathogenic nematode but also characterised the nematode according to its moisture requirements to optimise its performance in field applications since it showed great promise as a biological control agent.National Research Foundation (NRF)MMM202
Leadership for employee engagement in a global organisation
No full textA research report submitted in fulfillment of the requirements for the Doctor of Philosophy, in the Faculty of Commerce Law and Management, Wits Business School, University of the Witwatersrand, Johannesburg, 2025This study examines the relationship between the leadership styles of first line managers and employee engagement in a global organisation. Leadership has significant impact on employee engagement, especially in a global context that is complex and uncertain. Organisations require new leadership strategies for managing human capital. This is because the business environment globally is marred by volatility, uncertainty, complexity, and ambiguity. The impact of globalisation, digitalization, technological advancement, and intense competition requires effective leadership for employee engagement. Despite the plethora of research on the impact of leadership on employee engagement, research on contemporary leadership approaches in global organisations is not extensive. Organisations rely more on employees for productivity and performance hence employee engagement is used as a strategy to gain competitive advantage. Organisations are operating in an era where they should create an environment conducive for high productivity through effective leadership and engaged employees. First line managers are responsible for employee engagement but should ensure that they employ suitable leadership styles that promote employee engagement. Most scholars have explored the relationship between transformational, transactional, laissez-faire, servant and authentic leadership styles, and employee engagement. However, these leadership styles may not be suitable for the contemporary business operating environment in relation to employee engagement. It appears that the relationship between agile, adaptive and multiplier leadership styles and employee engagement has attracted less attention in research despite its importance to leadership theory and global organisations. Moreover, existential thinking has limited research in leadership theory in terms of its ii influence on employee engagement. This study investigates the relationship between leadership styles of first line managers and employee engagement with a potential moderating effect of leadership existential thinking in a global pump manufacturing organisation. The study hypothesizes the relationship between agile, adaptive and multiplier leadership styles and employee engagement. It tests the relationships between these leadership styles moderated by existential thinking. This cross-sectional quantitative study is grounded on the positivism philosophy using a deductive approach. A survey method was used to collect primary data from 753 first line managers in 52 countries in a global pump manufacturing organisation. The data was analysed through statistical techniques that include descriptive statistics, correlation analysis, and structural equation modelling (SmartPLS-SEM). The sample consists of first line managers with different titles including manager, supervisor, and team leader. The findings of this study show that agile leadership is considered the dominant leadership style for first line managers in this global organisation. Statistically significant relationships were found between adaptive leadership, agile leadership and existential thinking, and employee engagement. The relationship between multiplier leadership and employee engagement was statistically insignificant. The moderating effect of existential thinking was statistically significant for the relationship between adaptive leadership and employee engagement. Statistically insignificant relationships were found between the moderating effect of agile leadership and multiplier leadership, and employee engagement. In conclusion, this study contributes to the existing leadership literature in the context of global organisations. While caution is necessary on attempts to generalise the study’s findings, the first line managers in global organisations may benefit from using agile and adaptive leadership styles. This study demonstrates the relationship between agile, adaptive and multiplier leadership styles and employee engagement. It also iii demonstrates the moderating effect of existential thinking on the relationship between adaptive leadership and employee engagement. It recommends a leadership framework for employee engagement suitable for the contemporary business operating environment. In respect of practical contribution, this study proposes an improved Twenty-Sixty-Twenty (TST) model shifting the proportions to the right so that a greater percentage of employees become more engaged.MM202
Twostep inertial accelerated algorithms for solving split feasibility problem with multiple output sets
No full textAgricultural pest management: Identification, characterisation, and stress tolerance of entomopathogenic nematodes
No full textA dissertation submitted in fulfilment of the requirements for the degree of Master of Science, to the Faculty of Science, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2025Sustainable agriculture faces increasing challenges from insect pests as climate change and pesticide resistance reduce the efficacy of conventional pest control methods. This study evaluated the biocontrol potential of two new nematode strains, Oscheius sp. k KN-2024 isolate kv-2022 and Cruznema sp. NTM-2021. Using insect-baiting and modified White-trap techniques, the nematodes and their symbiotic bacteria were isolated, with DNA extraction performed using E.Z.N.A kits followed by sequencing and bioinformatic identification. Laboratory experiments assessed the efficacy and environmental tolerance of these potential entomopathogenic nematodes (EPNs) under varying temperature and desiccation conditions to enhance their application as eco-friendly alternatives to chemical pesticides. Cruznema sp. NTM-2021 demonstrated efficacy across a broad temperature range (5-30°C), exhibiting opportunistic pathogenic characteristics, while O. sp. k KN-2024 displayed true entomopathogenic behaviour with optimal efficacy at 25°C. At elevated temperatures (37°C), insect mortality occurred independently of nematode infection, indicating complex temperature-host-pathogen interactions. Desiccation trials revealed superior survival rates for both strains at higher relative humidity levels (75-85%), with O. sp. k KN-2024 demonstrating significantly greater desiccation tolerance than C. sp. NTM-2021. Peak survival was observed at 85% relative humidity over 24 hours. Four-way ANOVA confirmed statistically significant differences in performance across experimental conditions. These findings provide critical insights for optimising strain-specific EPN deployment in diverse agricultural settings, potentially reducing chemical pesticide dependence. By characterising the environmental tolerances of these novel nematode strains, this research advances the development of targeted, sustainable biological control strategies for integration into environmentally conscious pest management systems.National Research Foundation (NRF)University of the Witwatersrand, Johannesburg - Research OfficeMMM202
Analyzing radiative heat on thirdgrade fluids over an expanding inclined sheet subject to higherorder chemical reaction An overlapping grid spectral quasilinearization approach
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