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Welcome to the NWU Repository, the open access Institutional Repository of the North-West University (NWU-IR). This is a digital archive that collects, preserves and distributes research material created by members of NWU. The aim of the NWU-IR is to increase the visibility, availability and impact of the research output of the North-West University through Open Access, search engine indexing and harvesting by several initiatives.

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Recent Submissions

Effect of fluxing inorganic element-bearing acetate composite on the distribution of pyrolytic products from Highveld partially oxidized fine-coal reject and its beneficiated residue
(Elsevier Ltd., 2024) Mphahlele,K; Matjie, R,H; Bunt, John, Reginald; Van Vuuren, Janse
The role of mineral-matter in coal significantly influences pyrolysis, yet there is no consensus on the behavior of inherent-minerals and carboxylate salts during coal or fine-coal reject (FCR) pyrolysis. This study investigates the effects of carboxylate salts (Ca(C2H3O2)2, Mg(CH3COO)2·4H2O, and Fe(C2H3O2)2 composite (CSC) on FCR, demineralized FCR (FCRD), and demineralized > 1.9 g/cm3 FCR sink fraction (SI1.9D) in a Fischer-assay double retort set-up under the following pyrolysis conditions: 500 °C and heating rate of 5 °C/min for 3 hours in nitrogen. Analytical techniques identified kaolinite, quartz, dolomite, siderite and calcite, and characterized tar precursors, functional groups, carbon associations, and species evolution in FCR, FCR+CSC, FCRD+CSC, SI1.9D, SI1.9D+CSC and their chars. FCR+CSC exhibited the fastest decomposition rate due to extraneous-minerals and CSC interactions. FCRD+CSC and FCR+CSC achieved the highest carbon conversion, tar yield and gas yield, and the lowest char yield compared to SI1.9D and SI1.9D+CSC. The CSC addition increased the S proportion in FCRD+CSC and SI1.9D+CSC chars due to the H2S in-situ capturing to form nano-sulfides and S-bearing amorphous phases. Also, the SI1.9D+CSC blend released a higher CO2 via inherent nano-carbonates reacted with H3O+ from kaolinite/illite transformation, the HF/HCl aqueous solution and acetate decomposition. Tar yield, polycyclic aromatics, alkylated phenolics, and naphthalene compounds decreased due to hydrogen transfer by CSC, inhibiting secondary cracking of intermediate vapors. These results highlight the catalytic potential of carboxylate salts, dependent on inherent-minerals and dominating maceral groups during coal pyrolysis
The effects of irrigation on the survival of Clostridium sporogenes in the phyllosphere and soil environments of lettuce
(American Society for Microbiology, 2024) Fourie, Johannes, Cornelius, Jacobus; Van Wyk, Deidre; Bezuidenhout, Cornelius ,Carlos; Mienie, Charlotte; Adeleke, Rasheed
This study aimed to address the gap in knowledge regarding the fate of foodborne pathogens within agro-ecosystems. It specifically focused on the surrogate microorganism Clostridium sporogenes, which was introduced into lettuce-producing environments via surface and spray irrigation methods, respectively. The concentration of C. sporogenes in the rhizosphere, phyllosphere, and non-rhizosphere soil was quantified by quantitative polymerase chain reaction (qPCR) over a 42-day trial. The surface irrigation method exhibited a more noticeable contamination effect on the soil environments, compared to the phyllosphere. The results indicated a noticeable increase in C. sporogenes concentrations during the initial 22 days, with a 10.4-fold rise (0.39–4.05 log copy numbers/g soil) in the rhizosphere and 1.9-fold increase (2.97–5.59 log copy numbers/g soil) in the non-rhizosphere. However, concentrations in both soil environments subsequently decreased, falling below the initial inoculum concentration by the end of the trial. In contrast, the spray irrigation method resulted in most of the contamination being localised on the lettuce phyllosphere, with a high C. sporogenes concentration of 9.09 log copy numbers/g leaves on day 0. This concentration exponentially decreased to a minimal 0.019 log copy numbers/g leaves by day 32. Although concentrations in both soil environments decreased over time, trace concentrations of C. sporogenes were detectable at the end of the trial, posing a potential hazard to the microbiological safety of postharvest produce. These findings shed light on the dynamics of C. sporogenes in agro-ecosystems and underscore the importance of irrigation practices that ensure the safety of those who consume fresh produce.
Comparative evaluation of the power-tomethanol process configurations and assessment of process flexibility†
(Elsevier B.V., 2024) Mbatha, Siphesihle; Cui, Xiaoti; . Panah,e ,G. Payam; Se´bastien,Thomas; Parkhomenko, Ksenia; Roger, Anne-Ce´cile; Louis, Benoit; Everson, Ray; Debiag,Paulo; Musyoka, Nicholas; Langmi, Henrietta
This paper compares different power-to-methanol process configurations encompassing the electrolyser, adiabatic reactor(s) and methanol purification configurations. Twelve different power-to-methanol configurations based on direct CO2 hydrogenation with H2 derived from H2O-electrolysis were modelled, compared, and analysed. A high temperature solid oxide electrolyser is used for hydrogen production. A fixed bed reactor is used for methanol synthesis. The aim of the paper is to give detailed comparison of the process layouts under similar conditions and select the best performing process configuration considering the overall methanol production, carbon conversion, flexibility, and energy efficiency. ASPEN PLUSs V11 is used for flowsheet modelling and the system architectures considered are the open loop systems where methanol is produced at 100 kton per annum and sold to commercial wholesale market as the final purified commodity. Further optimization requirements are established as targets for future work. Three options of power-to-methanol configuration with methanol synthesis from CO2 hydrogenation are proposed and further evaluated considering process flexibility. From the evaluation, the series–series based configuration with three adiabatic reactors in series performed better in most parameters including the flexible load dependent energy efficiency
Strengths use and deficit improvement of first-year university students: A structural model for social support and student outcomes
(Taylor & Francis Ltd., 2023) Mostert, K; Du Toit, C
This study aimed to examine first-year students’ proactive behaviour towards strengths use (PBSU) and deficit improvement (PBDI), their relationship with students’ social support and essential student outcomes (student burnout, student engagement, life satisfaction, satisfaction with studies, study–course fit and intention to drop out). A sample of first-year students (N = 776; 19–20 years = 67%; female = 62%; black = 58%) from a large South African university completed the Strengths Use and Deficit Correction (SUDCO) questionnaire; the Maslach Burnout Inventory–Student Survey (MBI–SS); as well as measures of present social support, engagement, satisfaction with life, person-study-course fit and intention to drop out. Structural equation modelling was used to test the relationships among the variables in the structural model using Mplus 8.6. Overall, this study’s findings show that PBSU and PBDI are significantly related, with the exception that support from parents did not predict deficit improvement and PBDI did not predict intention to drop out. The results further show that PBSU was much more strongly related to support from parents, cynicism, life satisfaction, satisfaction with studies, study-course fit and intention to drop out. In contrast, PBDI was much more strongly related to support from significant others, exhaustion and engagement. The results confirm that engaging in proactive behaviour towards strengths use and deficit improvement may result in positive student outcomes. The findings of this study suggest a need for university institutions to implement initiatives to promote social support programmes for students to leverage their strengths, creating learning environments conducive to student success.
Well-being of first-year students: The role of study characteristics, strengths and deficits Read online: Scan this QR code with your smart phone or mobile device to read online.
(AOSIS, 2024) Mostert, K; Du Toit, C
Orientation: Higher education institutions (HEIs) are crucial in preparing students for the work force. Practitioners, such as industrial psychologists, can aid HEIs to enhance student development and improve university efficiency. Research purpose: This study aims to investigate the relationship between student demands and resources, proactive behaviour towards strengths use (PBSU) and proactive behaviour towards deficit improvement (PBDI), and students’ well-being (emotional, social and psychological). Motivation for the study: Two specific types of proactive behaviour, namely PBSU and PBDI, have been identified that may contribute to student success. Investigating the impact of these behaviours on student antecedents and outcomes could offer valuable insights for designing student development initiatives. Research approach/design and method: This study included 773 South African first-year university students studying at different campuses of a South African university. Structural equation modelling was used to test the structural model and investigate the regression weights. Main findings: Students’ personal problems were found to predict both PBSU and PBDI negatively. Autonomy positively predicted both types of proactive behaviour. Proactive behaviour towards strengths use was strongly related to emotional and psychological well-being, while PBDI was strongly related to social well-being. Practical/managerial implications: This study highlights the direct impact of PBSU and PBDI on students’ well-being. Practitioners in university settings can benefit from there commendations provided in this article to inform and implement initiatives related to student development and assist students in developing the necessary skills to enhance their work readiness. Contribution/value-add: This study’s findings contribute to the relatively small body of research on implementing strengths-based and deficit improvement initiatives in South African universities.