Conference Publications

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Active nanocomposite films based on low density polyethylene/organically modified layered bouble hydroxides/thyme oil to retain retail shelf life and quality of hass avocados
(2020-12) Kesavan Pillai, Sreejarani; Sivakumar, D; Ray, Suprakas S; Obianom, P; Eggers, Sharon K; Mhlabeni, T
In this study, the ability of an active film containing volatile bioactives in post-harvest disease control and preservation of quality in avocados is explored as a non-traditional treatment method. Antimicrobial transparent flexible trilayer low density polyethylene (LDPE) films containing organically modified layered double hydroxides (OLDH) and plant bioactive-thyme oil (TO) were made using single step blown film extrusion. Antifungal effects of the packaging in comparison to commercial treatment and untreated control showed considerable reduction in anthracnose disease events in ‘Hass’ cultivar of avocados while improving the fruit quality. 2wt% OLDH loading improved the oxygen and moisture barrier properties while not affecting the transparency of the film. The results suggest that the synergistic effect of barrier and antimicrobial properties of the controlled volatile bioactive release of the nanocomposite film can be utilised as a prospective strategy to modify the headspace gas composition to combat anthracnose disease in avocados.
Analytical techniques to quantify modifiers in bitumen for the South African asphalt pavement industry
(2021-07) Makhari, A; Hawes, Nomashaka BN; Mturi, George AJ; Ojijo, Vincent O
Modifying bitumen is currently a common practice in South Africa. The asphalt pavement industry has seen an increase in use of different types of modifiers in an attempt to improve or extend the properties of bitumen. Common modifiers used in South Africa include plastomers (e.g. ethylene vinyl acetate or EVA), elastomers (e.g. styrene-butadiene-styrene or SBS) and warm mix additives (e.g. waxes). Bitumens are already complex materials which can be represented mechanically and rheologically with mathematical models. Recently, the need to also characterise the in situ structural and chemistry effect of modifiers within bitumen has been appreciated, in order to determine their influence on modified bitumen performance. This paper explores the analysis of bitumen with various modifiers using Fourier Transform Infra-Red (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Special attention is paid to quantification of these modifiers in bitumen as a quality control and forensic investigative tool, due to the current asphalt failure challenges facing the industry. The aim is to accurately determine the extent of modification through analytical techniques as a monitoring tool for the better construction of asphalt pavement roads. The paper shows such analytical scientific techniques have the potential to quantify locally used modifiers in South African bitumen.
Biowaste biorefineries in South Africa: Current status, opportunities, and research and development needs
(2023-12) Sekoa, Patrick T; Chunilall, Viren; Msele, K; Buthelezi, L; Johakimu, Jonas K; Andrew, Jerome E; Zungu, M; Moloantoa, K; Maningi, N; Habimana, O; Swartbooi, Ashton M
As one of the highest carbon-emitting nations, South Africa is working tirelessly to swiftly transition to sustainable technologies in order to strengthen its green economy initiatives. Amongst the technologies that are explored in the scientific and industrial community, biorefineries are seen as the most efficient technologies that can be used to create economic opportunities and will contribute to the advancement of a bio-based economy as they can synthesize diverse industrially-competitive products. Despite their numerous socio-economic advantages, the establishment of large-scale biorefineries in developing nations like South Africa is very scarce. Therefore, it is imperative to address the technological gaps that hinder the growth of large-scale biorefineries and provide practical solutions that could be used to solve these bottlenecks. This work provides a comprehensive review of the development of biowaste biorefinery-based technologies in South Africa. Different biowaste valorization technologies applicable to locally available organic waste streams, and the resulting market-based compounds that can be obtained from these sustainable feedstocks, are reviewed. Finally, the work provides insights into research and development needs (knowledge gaps) that should be explored by scientists and industries, as these technological solutions might propel biorefineries toward industrialization in South Africa.
Cellulose nanocrystals and snail shell-reinforced polyvinyl alcohol bioplastic films: Additive concentration optimization and mechanical properties assessment
(2022-07) Gbadeyan, Oluwatoyin J; Fagbemi, Olajumoke D; Jerome, Andrew E; Adali, S; Glen, B; Sithole, Bishop B
This study focused on modeling and optimization of the concentration of poly (vinyl alcohol) (PVA), cellulose nanocrystals (CNC), snail shell nanoparticles (SSN), and glycerol for the development of bioplastic films. The response surface methodology using Box–Behnken experimental design was used to investigate the effect of the independent parameters (additives concentrations) on the ultimate tensile strength and Young's modulus of fabricated bioplastic films. A varied ultimate tensile strength and Young's modulus with different component loadings was observed, proving the effect of nanoparticles loading effect on the mechanical properties of bioplastic films. The quadratic polynomial model experiment data provided a coefficient of determination (R2) of 0.795 for ultimate tensile strength and 0.732 for Young's modulus, evidencing the fitness of the models to pilot the optimization space. The optimum parameters were PVA (7.820%), CNC (1079%), SSN (1241%), and glycerol (2.657%). The ultimate tensile strength and Young's modulus of 27.2 MPa and 31.2 MPa were obtained for the developed bioplastic film with optimized concentrations of each component. The bioplastic films showed improved thermal stability and degradation. The scanning electron microscopy (SEM) imaging revealed a homogeneous dispersion of SSN and CNC in the matrix, which explained the improved properties observed.
Chemical modification of sugarcane bagasse with chitosan for the removal of phosphates in aqueous solution
(2020-11) Manyatshe, Alusani; Balogun, Mohammed O; Nkambule, TTI; Cele, Zamani ED; Msagati, TAM
Sugarcane bagasse is the major solid waste product of the sugarcane industry. As a plant-derived biomass, it is an attractive environmentally friendly alternative to petroleum-based materials. Being a non-food agriculture product, its use as a raw material is more widely accepted. Sugarcane bagasse is comprised mainly of cellulose, hemicellulose and lignin. The aim of this study was to develop a low-cost anion exchange adsorbent from sugarcane bagasse for the removal of phosphates in aqueous solution. The adsorbent was developed by crosslinking chitosan with cellulose that was extracted from sugarcane bagasse. To obtain cellulose for covalent linkage with chitosan, the bagasse was pretreated with dilute sodium hydroxide and sulphuric acid solutions followed by bleaching with hydrogen peroxide. After this process, the material was modified using chitosan functionalized with epichlorohydrin to obtain the modified bagasse (SCB-CS). SCB-CS was characterized using Fourier transform infrared spectroscopy (FTIR) analysis that indicated the successful reduction in the content of lignin and hemicellulose. The grafting of chitosan derivatives within the matrix of cellulose was confirmed by intense peaks at 1651cm-1 and 1589 cm-1 observed on the modified SCB-CS. SCB-CS was evaluated for its ability to remove phosphates from synthetic waste water and 61.51% removal and an adsorption capacity of 52.3 mg/g, where the initial concentration was 28.36 mg/L at an adsorbent dosage of 0.1 g was achieved.
Gas chromatographic profiling of the biocatalytic conversion of sclareol to ambradiol by Hyphozyma roseoniger
(2021-10) Ncube, EN; Mathiba, Kgama; Steenkamp, Lucia H; Dubery, IA
Hyphozyma roseoniger is a filamentous yeast used for its biocatalytic ability to convert sclareol, a plant diterpenoid to ambradiol, an intermediate to ambrafuran, which is a sought-after fixative in the perfume industry. Metabolite profiling is a suitable investigative tool to dissect the biochemical steps involved in the biocatalytic reaction by H. roseoniger from sclareol to ambradiol. H. roseoniger suspensions were grown in batch culture to simulate growth in a bioreactor over a 14-day period. Cells were harvested at stipulated days (phases of growth) using an ethyl acetate extraction procedure. The progress of the bioconversion was monitored using gas chromatography with flame ionisation detection (GC–FID) profiling. Here, decreasing concentrations of sclareol with concomitant increasing concentrations of ambradiol as product and with sclareolide as a putative intermediate, were recorded. While the presence of unidentified peaks were noted in the GC chromatograms, no previously unknown intermediates could be identified in the sequence of sclareol to sclareolide to ambradiol.
Gas sensing materials roadmap
(2021-06) Wang, H; Ma, J; Zhang, J; Feng, Y; Vijjapu, MT; Yuvaraja, S; Surya, SG; Salama, KN; Tshabalala, ZP; Akande, Amos A
Gas sensor technology is widely utilized in various areas ranging from home security, environment and air pollution, to industrial production. It also hold great promise in non-invasive exhaled breath detection and an essential device in future internet of things. The past decade has witnessed giant advance in both fundamental research and industrial development of gas sensors, yet current efforts are being explored to achieve better selectivity, higher sensitivity and lower power consumption. The sensing layer in gas sensors have attracted dominant attention in the past research. In addition to the conventional metal oxide semiconductors, emerging nanocomposites and graphene-like two-dimensional materials also have drawn considerable research interest. This inspires us to organize this comprehensive 2020 gas sensing materials roadmap to discuss the current status, state-of-the-art progress, and present and future challenges in various materials that is potentially useful for gas sensors.
Immunogenic profile of a plant-produced nonavalent African horse sickness viral protein 2 (VP2) vaccine in IFNAR-/-mice
(2024-04) O’Kennedy, Martha M; Roth, Robyn; Ebersohn, K; Du Plessis, LH; Mamputha, Sipho; Rutkowska, Daria A; Du Preez, Ilse; Verschoor, JA; Lemmer, Yolandy
A safe, highly immunogenic multivalent vaccine to protect against all nine serotypes of African horse sickness virus (AHSV), will revolutionise the AHS vaccine industry in endemic countries and beyond. Plant-produced AHS virus-like particles (VLPs) and soluble viral protein 2 (VP2) vaccine candidates were developed that have the potential to protect against all nine serotypes but can equally well be formulated as mono- and bi-valent formulations for localised outbreaks of specific serotypes. In the first interferon a/ß receptor knock-out (IFNAR-/-) mice trial conducted, a nine-serotype (nonavalent) vaccine administered as two pentavalent (5 µg per serotype) vaccines (VLP/VP2 combination or exclusively VP2), were directly compared to the commercially available AHS live attenuated vaccine. In a follow up trial, mice were vaccinated with an adjuvanted nine-serotype multivalent VP2 vaccine in a prime boost strategy and resulted in the desired neutralising antibody titres of 1:320, previously demonstrated to confer protective immunity in IFNAR-/- mice. In addition, the plant-produced VP2 vaccine performed favourably when compared to the commercial vaccine. Here we provide compelling data for a nonavalent VP2-based vaccine candidate, with the VP2 from each serotype being antigenically distinguishable based on LC-MS/MS and ELISA data. This is the first preclinical trial demonstrating the ability of an adjuvanted nonavalent cocktail of soluble, plant-expressed AHS VP2 proteins administered in a prime-boost strategy eliciting high antibody titres against all 9 AHSV serotypes. Furthermore, elevated T helper cells 2 (Th2) and Th1, indicative of humoral and cell-mediated memory T cell immune responses, respectively, were detected in mouse serum collected 14 days after the multivalent prime-boost vaccination. Both Th2 and Th1 may play a role to confer protective immunity. These preclinical immunogenicity studies paved the way to test the safety and protective efficacy of the plant-produced nonavalent VP2 vaccine candidate in the target animals, horses.
Microbial Induced Calcium Carbonate Precipitation (MICCP) for road construction
(2022-07) Smit, Michelle A; Akhalwaya, Imraan; Rust, FC; Ramdas, Veshara
The growing concern over climate change has led the drive for the development of alternative building materials in several industries, including road construction. Bio-based construction, using Microbial Induced Calcium Carbonate Precipitation (MICCP) has been investigated in recent years as a potential cost-effective and environmentally friendly alternative engineering approach. The Council for Scientific and Industrial Research (CSIR) developed a research program looking at MICCP. Several barriers to using MICCP in road construction was found, a potential biohazard using exotic bacteria and the current technique used for treatment. In this paper, in situ cultivation of indigenous urease positive bacteria was investigated and compared to a CSIR designed biological prototype. The objective of this paper is to present the results of Unconfined Compressive Strength (UCS) tests performed on a marginal G5 (COLTO, 1985) material treated with the prototype and in situ cultivated bacteria. The work showed that it was possible to cultivate urease positive bacteria present within the G5 material. It was found that the cementation solution could act as a stimulation and cementation media when the pH is reduced to give the bacteria time to cultivate and buffer the pH upward for Calcium Carbonate Precipitation to take place. Lastly, the CSIR prototype performed better in terms of UCS and treatment technique. The treatment consists of only one application of the prototype, which is more consistent with current road construction practice, as compared with the multiple application needed for in situ cultivation.
Nanofluids and their application in carbon fibre reinforced plastics: A review of properties, preparation, and usage
(2023-08) Lawal, SA; Medupin, RO; Yoro, KO; Okoro, UG; Adedipe, O; Abutu, J; Tijani, JO; Abdulkareem, AS; Ukoba, K; Sekoai, Patrick T
Renewed call for the replacement of conventional materials with carbon fibre reinforced plastics (CFRPs) in many high-performance applications is responsible for the current wave of research on minimum quantity lubrication (MQL) strategy in machining. Due to their competitive advantages over conventional materials, polymer matrix composites (PMCs) are now attracting the attention, of researchers, especially in the field of machining. Although most manufacturing methods require less machining, precision machining like milling and drilling call for more research inputs. For this purpose, this review article assesses various aspects of nanofluid preparation and its application in CFRPs. Recent scientific reports on nanofluids with a focus on properties, preparation, and application (including respective methodologies) were analyzed, to contribute to the growing database for future research in this field. This review article shows that cutting temperature and cutting force remain the key determinants of surface finish, while tool wear constitutes a major parameter that machining scientists would like to keep under full control by the use of appropriate cutting fluids. Uncertainties around the quality of nanofluids which is scarcely discussed in the literature is raised in this review, while advocating for more research to unravel it. Furthermore, this review article sheds more light on the machining operations of carbon fiber-reinforced plastics using nanoparticle-laden fluids for a safe and sustainable machining experience. Finally, this review assesses the possibility of achieving excellent CFRP processing using a sustainable approach to fill existing gaps identified in literature like wasted cutting liquids, environmental pollution, and exposure of operators to health hazards.
A novel method for rapid extraction of biofibres from waste chicken feathers
(2021-02) Kakonke, Grace; Tesfaye, Tamrat; Sithole, Bishop B; Ntunka, M
South Africa is the biggest chicken meat producer in Southern Africa and generates about 258 million kg of waste feathers. Although some of this waste is beneficiated into animal feed and fertiliser there are problems in adequate digestion of the feed by animals. Consequently, there is a need to find other innovative ways of beneficiating the waste. In this paper, beneficiating of feathers by extraction of fibres for possible conversion into high value products was explored. Three mechanical methods for extracting fibres from feathers were evaluated and the properties of the resultant fibres were studied and compared: they were using a tweezer, a blender, and a novel stripping method using a pulp fluffer. The results revealed that fibres extracted from chicken feathers using a tweezer or a blender had a hollow structure whereas those from the fluffer exhibited pronounced damaging effects on the fibre structure as some barbules were detached from their rami. Fluffer fibres had the highest average length of 16.56 mm followed by blender (16.15 mm) and tweezer (14.84 mm); they were also the most flexible with an aspect ratio of 476.29. The modified pulp fluffer appeared to be a cost-effective and an efficient method of grinding feathers into commercial fibres.
Physico-chemical characterization of polyethylene glycol-conjugated betulinic acid
(2020-11) Mvango, Sindisiwe; Mthimkhulu, N; Fru, PA; Pilcher, LA; Balogun, Mohammed O
Betulinic acid (BA) is a naturally occurring plant pentacyclic triterpenoid with activity against cancer and infectious diseases like malaria and AIDS. Its pharmacological activity is limited by low aqueous solubility and bioavailability. Attempts have been made to improve the solubility of BA by conjugation to the water-soluble polymer polyethylene glycol (PEG) but with very limited physico-chemical characterizations. This work presents physico-chemical characterizations of a PEG-BA conjugate using 1H NMR spectroscopy, electron microscopy, DLS and XRD. The NMR data showed successful conjugation through the formation of an amide bond with a 5% drug loading although the appearance of some chemical shift signals were solvent-dependent. TEM images showed a spherical morphology of the conjugate with average diameter of 59.58±4.47 nm.
Pseudocapacitive material for energy storage application: PEDOT and PEDOT:PSS
(2020-11) Adekoya, Gholahan J; Sadiku, RE; Hamam, Y; Ray, Suprakas S; Mwakikunga, Bonex W; Folorunso, O; Adekoya, OC; Lolu, OJ; Biotidara, OF
The total volume of solar energy reaching the earth in every second is equivalent to the total energy usage by the entire human race for three days. With this vast amount of clean energy freely available to humanity, there is still heavy dependence on fossil resources for energy. The major challenge with the use of fossil-based fuel is the generation of both land and atmospheric pollutants, which adversely affect the ecosystem. However, an essential requirement in transitioning from fossil energy to clean energy is the use of effective energy storage systems. Poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(4-styrene sulfonate) (PSS) PEDOT:PSS is currently one of the highly researched semi-conducting polymers that form the vast and expanding literature on energy application. Owing to its high electrical conductivity, thermal stability, and film-forming ability, PEDOT and its derivatives are employed for pseudocapacitive storage applications. This review will present a detailed discussion on the synthesis, properties, and application of PEDOT:PSS for battery and ultracapacitors. Highlights on the recent development and outlook in the use of PEDOT and its derivatives for energy application will also be provided.
Qualitative assessment on the surfactant traces from the organically modified nanoclay containing polymer nanocomposite
(2020-11) Khoza, Mary; Sinha Roy, Jayita; Ray, Suprakas S; Ojijo, Vincent O
Traces of quaternary ammonium salt from dispersed nanoclay in PA6/6.6 polymer nanocomposite may have some potential toxicological effects that could pose a risk to human health. Modified nanocomposite system was produced by masterbatch melt extrusion process while water-assisted nanocomposite was prepared via direct melt extrusion process. Investigations were conducted by hyphenated thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA-FTIR). Small traces of surfactant alkyl ammonium ions in the nanocomposite can be found in the masterbatch and nanocomposite.
A review of technologies used in handling the acid mine drainage challenge: Perspectives on using green liquor dregs as a sustainable option for treatment of acid mine drainage
(2021-02) Sebogodi, Keolebogile R; Johakimu, Jonas K; Sithole, Bishop B
Acid mine drainage (AMD) is one of the repercussions that result from earth-moving activities around the sulfide-bearing mineral hosts. The detrimental effects associated with this AMD are driven by its characteristics, which include low pH and high concentrations of sulfate and toxic dissolved metals. Traditionally, the prevention and treatment of AMD are achieved by using technologies that use, amongst other, naturally occurring soils and carbonates. However, the continual use of these materials may eventually lead to their depletion. On the other hand, industrial by-products have been proven to occupying land that could have otherwise been used for profitable businesses. Additionally, the handling and maintenance of landfills are costly. In this current trend of a circular economy that is driven by industrial symbiosis, scientists are concerned with valorizing industrial by-products. One such by-product is the green liquor dregs (GLD) from Kraft mills. The neutralizing and geotechnical properties of these wastes have prompted the research pioneers to seek their potential use in handling the challenges associated with AMD. In this review, the formation AMD, trends in technologies for treatment and prevention of AMD are critically analyzed. This includes the feasibility of using GLD as an alternative, promising sustainable material.
Role of cellulose nanofibrils in improving the strength properties of paper: A review
(2021-11) Jele, TB; Lekha, Prabashni; Sithole, Bishop B
The pursuit for sustainability in the papermaking industry calls for the elimination or reduction of synthetic additives and the exploration of renewable and biodegradable alternatives. Cellulose nanofibrils (CNFs), due to their inherent morphological and biochemical properties, are an excellent alternative to synthetic additives. These properties enable CNFs to improve the mechanical, functional, and barrier properties of different types of paper. The nanosize diameter, micrometre length, semicrystalline structure, high strength, and modulus of CNFs have a direct influence on the mechanical properties of paper, such as tensile index, burst index, Scott index, breaking length, tear index, Z-strength, E-modulus, strain at break, and tensile stiffness. This review details the role played by CNFs as an additive to improve strength properties of paper and the factors affecting the improvement in paper quality when CNFs are added as additives. The paper also includes techno-economic aspects of the process and identifies areas that need further research.
Structure-property relationship of the laser cladded medium carbon steel: The use of butter layer between the substrate and the top clad layer
(2019-03) Botes, Annelize; Bolokang, Amogelang S; Kortidis, Ioannis; Matjeke, V
The structure-property relationship of the laser deposited 316 L/St 1.2311 and Fe/St 1.2311 on E9 substrate was investigated. The variation in the geometrical features of the deposited layers, width, thickness, depth of penetration into the substrate, and the dimensions of the heat-affected zone (HAZ) was studied. The X-ray diffraction (XRD) technique detected structural transformations. Substrate Ferritic and martensitic structures were found on the substrate and clad layers. MnS inclusion was observed on the heat-affected zone (HAZ). Microstructural analysis was conducted by the optical microscopy while Vickers hardness tester measured the macro-hardness.
Surfactant-assisted green liquor dregs pretreatment to enhance the digestibility of paper mill sludge
(2021-06) Rorke, DCS; Lekha, Prabashni S; Kana, GEB; Sithole, Bishop B
This study optimizes a novel surfactant-assisted green liquor dregs (GLD) pretreatment of paper mill sludge (PMS), both of which are wastes from the kraft pulping industry, using a combined Response Surface Methodology (RSM) design. Optimized conditions give a maximal reducing sugar release of 16.38 g/L. A substantial reduction in heavy metals aluminum, chromium, cobalt, arsenic, lead, and copper after pretreatment illustrates the enhancement of substrate digestibility by reducing toxic elements. Separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) for hydrogen production are assessed. SSF produced a hydrogen yield of 3.72 mL/g, displaying a 36.26% increase from pretreated PMS compared to SHF. These findings provide insights into possible methods of reducing process duration, energy input, and costs incurred with waste disposal within the paper industry. Furthermore, improved hydrogen yield using an SSF process demonstrates the potential beneficiation of pulp and paper GLD and PMS wastes.
Systematic review of WAVE water treatment design software and related technologies
(2023-01) Roopchund, R; Andrew, Jerome E; Sithole, Bruce B
The water treatment industry needs customized solutions. Despite the advancement of water treatment technologies, proposed designs must pass pilot trials before industrial implementation. Technology piloting is costly and time-consuming. Water treatment software tools can optimize processes through simulation to meet the industry's need for rapid process solutions, thus saving time and money. However, not many studies demonstrate the requirements and capabilities of water treatment design software. Hence, this study aims to demonstrate the ability of the Water Application Value Engine (WAVE) software to design a demineralized water production plant for a Biorefinery process. The feedwater data was input in WAVE. The ultrafiltration (UF) and reverse osmosis (RO) process operations were specified, and the required water output was specified. WAVE simulated the process and provided the water quality exiting each process operation. The UF reduced the total suspended solids in the feedwater, while the RO lowered the total dissolved solids, thus reducing the ions by 98.56%. This ion removal ensures that the process equipment is protected from corrosion while yielding a high-quality product in the biorefinery process. Several design warnings were issued, analyzed, and mitigated. The study concluded that WAVE could effectively design and simulate new water treatment processes. Additionally, WAVE can serve as a diagnostic tool to optimize existing water treatment plants. The findings implied that Engineers and Academics could use WAVE to meet the industry’s demand for rapid and accurate process solutions. The reported methodology can serve as an empirical guideline for WAVE and similar software tools.
The thermal degradation kinetics and morphology of poly(vinyl butyral) cast films prepared using different organic solvents
(2020-11) Motlatle, Abesach M; Bothloko, Orebotse J; Scriba, Manfred R; Ojijo, Vincent O; Ray, Suprakas S
Polyvinyl butyral (PVB) films are highly promising materials as they combine interesting thermal and structural morphology properties and in many cases coating viability. However, the polymerization ability of PVB films through solvent casting method using different solvents is fundamentally not well understood. In this rational, the present study demonstrates the use of Isopropanol, ethanol, methanol, and acetic acid for the development of high quality PVB films. The resulting acetic acid-based PVB film exhibits moderated thermal stability with smooth surface morphology which is an important factor in coating applications. On the other hand, ethanol-based PVB film achieves higher thermal stability relative to all other PVB films with some structural defects attributed to less impurities in the solvents. This study will pave the development of high performance PVB cast films.

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