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2,2-Dithiobis(benzothiazole) complexes (Cd and Ni): Precursors to nanoparticles and electrochemical properties and interactions with Rhodamine B
(Vaal University of Technology, 2021-10-13) Mabaso, Busisiwe Dagracia; Moloto, N., Prof.; Moloto, M. J., Prof.
The ligand 2, 2-dithiobisbenzothiazole and it metal complexes have been a subject of interest in various fields but they have found to exhibit remarkable and prevalent biological and pharmacological activities. The ligand tends to coordinate to complexes through the sulfur atom and hence the metal-sulphide bond are good precursor to generate metal sulfide nanoparticles using single-source precursor route. The complexes are generally prepared by reflux for 1 to 2 hours depending on the solvent used to produce very stable solid products and some form in crystalline form. All the prepared nickel and cadmium complexes were characterized using techniques such as elemental analyzer, IR, 13C NMR spectroscopy and thermogravimatric analysis. The data obtained from the spectroscopic analysis was consistent of the coordination of the ligand with the metal ions through the sulphur atoms of the 2,2-dithiobisbenzothiazole moiety. The thermal analysis of the prepared complexes gave a final residue of metal sulphide for both metal complexes. Characterization techniques showed the formation of bidentate complexes for both nickel complex and cadmium complex. The prepared complexes were then used to synthesize metal sulphide nanoparticles .The nanoparticles were prepared by thermal decomposition method of the single source precursor in a solution of oleylamine (OLA). Two different parameters were investigated temperature and time to study their effect on the size and shape of the nanoparticles. The synthesized nanoparticles were characterized using techniques such as UV-Vis spectroscopy, photoluminescence spectroscopy, and X-ray diffraction analysis and transmission electron microscopy. The temperatures of the reaction have a significant effect on the rate of the reaction that will affect the size and shape of the nanoparticles. This effect was confirmed by the optical properties of the synthesized nanoparticles prepared at different reaction temperatures. The spectra shows that absorption maximum and band edge shift to lower wavelength as the temperature of reaction was progressively increased. This trend is associated to the decrease in particles size of the prepared nanoparticles. TEM images further confirmed that the particles size of the prepared nanoparticles was progressively decreased as the temperature was increased. The time of the reaction is one of the most significant factors in the synthesis of the nanoparticles. The investigation of the time of the reaction yield results that depicted that with increase in time of the reaction, the band edge increases, but relatively at short wavelength to the bulk. Hence, the band edges of the nanoparticles were blue shifted significantly to the bulk. The results show that with an increase in the time of the reaction, the nanoparticles increases in their size due to Ostwald ripening. The optimum complexes and optimum nanoparticles were used to further study their electrochemical properties using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) graphs were fitted using the randles circuit and they confirm that the NiS nanoparticles GCE greatly increase the electron transfer rate, probably due to the nanostructured surface property of the NiS nanoparticles. Differential pulse voltammetry (DPV) was used to study the electrochemical behavior and the DPV showed that the current response of Rhb was higher for the optimum temperature NiS nanoparticles compared to all the materials used. There was an increase in the Rhb current response with an increase in pH and pH 7 was used as the optimum pH when Ni- complex was used as a modifier and pH 8 was used as optimum when NiS nanoparticles were used as a modifier. Effect of concentration showed that the NiS nanoparticles for the optimum temperature had a wide linear range and a low detection limit. The method has good accuracy, acceptable precision, and reproducibility. This method provides a novel electrochemical method for determination of RhB.
A model to measure the E-learning system success at a University of Technology in South Africa
(Vaal University of Technology, 2022-05) Rankapola, Madute Elias; Lebelo, S.; Zuva, T., Prof.
As e-learning systems adoption increases worldwide, their effectiveness and success measurement become imperative. Therefore, it is crucial to justify the investment made in e-learning systems by assessing their value and benefits within the academic field. Higher Education Institutions (HEIs) adopt and implement e-learning systems to enhance the quality of their teaching and learning practices, such as extending the teaching and learning space beyond physical locations, convenience, on-demand learning, self-paced learning, cost-effectiveness, time-efficient and flexible learning environments. However, some universities in developing countries encounter many challenges in implementing e-learning systems and eventually drop out of their e-learning system endeavours. This implies that universities in developing countries may face unique challenges compared to those in developed countries. Therefore, the current study aimed to identify and investigate critical e-learning system success factors at universities of technology in South Africa and develop a comprehensive model to measure the e-learning system success. A literature review was conducted to achieve the research aims and objectives, and a research model that encompassed the variables: Technical System Quality (TSQ), Content & Information Quality (C&IQ), Educational System Quality (ESQ), Service Quality (SQ), User Self-Efficacy (USE), User Satisfaction (US), Intention to Use/Use (IU/U), Net Benefits and System Loyalty (SL). A cross-sectional survey was implemented using a 5-Likert scale electronic questionnaire to collect data from a sample of 654 participants studying Information and Communication Technology (ICT) from universities of technology in South Africa. The reliability was measured using Cronbach's alpha and all the values were greater than 0,73, higher than the threshold of 0.70 for acceptable reliability. Validity was conducted through convergent (AVE>0.5) and discriminant validity (AVE>ICCS). Factor analysis was done using Principal Component Analysis (PCA), and all nine constructs were retained after the analysis. The structural model displayed suitable model fit indices (CMIN/DF = 3.514; CFI = 0.935; Normed Fit Index Root Mean Square Error of Approximation (NFI) = 0.953; Comparative fit index (CFI) = 0.959; AGFI = 0.880; Tucker-Lewis Index (TLI) = 0.926; and (RMSEA) = 0.068). These GoF results highlighted that the model was acceptable for deriving conclusions from the hypotheses tested. Pearson Correlation Analysis results showed positive relationships exist between the variables except for TSQ & USE. Multiple regression analysis indicated that USE→C&IQ (β= 0.183, <0.05); USE→ESQ (β = 0.453, <0.05) USE→SQ (β = 0.785,<0.05), USE→US (β = 0.995, <0.05), US→USE (β = 0.605, <0.05), IU/U→US (β = 0.797, <0.05), NB→IU/US (β= 0.538, <0.05), IU/U→NB (β = 0.166, <0.05), SL→NB (β = 0.736, <0.05) were statistically supported. The final model was then developed. The study contributed to the body of knowledge by highlighting critical factors that influence an e-learning system success at universities of technology in South Africa. The study provided a deep insight into the theories and models used for measuring system success. A modified model was developed. The model may be used by researchers to test system success in different settings and countries. Universities of Technology may use the model to guide the design, development and adoption of e-learning systems.
Acceptance of biometric authentication security technology on mobile devices
(Vaal University of Technology, 2022) Malatji, W. R.; Van Eck, Rene, Dr.; Zuva, Tranos, Prof.
Mobile devices are rapidly becoming a key computing platform, transforming how people access business and personal information. Accessing business and personal data using mobile devices requires authentication that is secure. The world is rapidly becoming connected and all users of mobile devices need to be clear regarding individual data security. As a result, biometrics for mobile devices has come into existence. Biometric technology can be applied on mobile devices to improve the trustworthiness of wireless services. Furthermore, it is of great importance and necessary to start paying attention to and investing in mobile biometric technologies, as they are quickly turning into tools of choice for productivity. In the literature review, it shows that few studies measured the acceptance of biometric authentication technology on mobile devices. This study seeks to find out the perceptions as to the acceptance of biometric authentication technology on mobile devices. TAM2 was used as the foundation for generating the hypothesis and developing the conceptual framework for this study. This quantitative study used a survey-based questionnaire to collect data from 305 participants. The simple random sampling technique was used to select participants for this study. The response rate was 98% of the expected population, which was a total of 302 valid responses. A descriptive analysis was deployed to provide a description of respondents’ demographic characteristics. SPSS was used to compute the multiple regressions in order to evaluate the research hypotheses. The findings of this study revealed that perceived humanness, perceived interactivity, perceived social presence, perceived ease of use and subjective social norm, and perceived usefulness and trust are important determinants of customers’ intention to accept and use mobile biometric devices. It was found that reliability is a good predictor of trust. On the other hand privacy, identity theft and combining data are also important determinants of trust. This work can be used to strengthen biometric authentication technology in-cooperation with mobile devices for simplicity of use. Since most mobile devices are used for personal and business information, further research on the acceptance of biometric authentication technology on mobile devices is needed.
Adoption of mobile learning at the University of Technology in South Africa
(Vaal University of Technology, 2019-11-29) Hlatshwayo, Motsotua Confidence; Baxter, Roger; Zuva, Tranos, Prof.
The influence of Information and Communication Technology (ICT) in the education system has encouraged both students and educators to become more and more computer literate. With the increased use of portable devices (tablets, PDAs, Smartphones, iPads etc.), mobile learning (m-learning) has gained popularity as it is believed to be an effective and efficient tool for content presentation and knowledge acquisition in education sector. The realisation of the benefits depends on the effective adoption of m-learning technology. The superseding purpose of this study was to investigate the adoption of mobile learning at a University of Technology (UoT) in South Africa. A quantitative study was carried out at an UoT in South Africa, with respect to mobile learning perceptions; 64 valid questionnaires were received from the participants. The proposed research framework/model derived from Extended Technology Acceptance Model (ETAM) and Technology Acceptance Model 3 (TAM3) was used. The Statistical Package for the Social Sciences (SPSS), version 25.0. was used for analysing data. The findings revealed that perceived usefulness of mobile learning, attitude toward mobile learning, service and system quality as well as perceived ease of use are significant predictors of intention to use mobile learning application. Perceived mobility on mobile learning strongly influences perceived usefulness more than perceived ease of use of mobile learning application. The study concluded that it is necessary to measure perception of potential users using the variables in the model proposed before adoption of mobile learning application to ascertain an effective adoption of the technology in education.
Adsorption and Photodegradation of Molasses Wastewater using TiO2-ZnO Hybrid Nanocatalysts Supported on Activated Carbon and Silica
(Vaal University of Technology, 2017-03) Otieno, Benton Onyango; Naidoo, E. B., Prof.; Aoyi, Ochieng, Prof.
There is an increasing use of composite materials in photo-catalysed remediation of wastes such as molasses wastewater (MWW), which is characterised by high organic load and a dark brown colour caused by biorecalcitrant melanoidin compounds. This study was carried out to determine the photocatalytic efficiency of a TiO2-ZnO hybrid supported onto activated carbon (AC) and silica for the remediation of MWW. Immobilisation of ZnO onto synthesised TiO2 formed TiO2-ZnO, which was then supported onto AC and silica, to give TiO2-ZnO/AC and TiO2-ZnO/Silica composites, respectively. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX) and Fourier Transform Infrared (FTIR) spectroscopies, and transmission electron microscopy (TEM), revealed the successful hybridisation of TiO2 and ZnO, and the subsequent support of the hybrid onto AC and silica. Thermal stability of the synthesised composite catalysts was studied by differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). Photoluminescence (PL) spectroscopy further revealed a restrained electron-hole pair recombination resulting from both the successful formation of a heterojunction in the hybrid, and the introduction of electron accepting AC support. Introduction of a silica support on the other hand increased the rate of recombination resulting in reduced quantum efficiency of the TiO2-ZnO/Silica composite, hence AC was adopted as the ideal support material for this study. Photodegradation was monitored in terms of colour and total organic carbon (TOC) reductions, and nitrate formation. It was observed that the TiO2-ZnO hybrid, due to its desirable optical properties, had better activity than the respective oxides (TiO2 and ZnO). On supporting the hybrid onto AC, both adsorption and photocatalytic activities were further enhanced with improved overall colour removal of 86% from 68%. Photodegradation followed pseudo-first order rection model, with the rate constant (𝑘𝑎𝑝𝑝) decreasing from 0.0701 to 0.0436 min-1 with increased MWW initial concentration from 3000 to 6000 ppm. Formation of nitrates confirmed a reductive pathway for the degradation of melanoidins. The UV-photodegradation process was found to be 33-fold less energy intensive for colour reduction as compared to TOC reduction, with energy demands of 35 and 1183 kWh/m3, respectively. Sorption of MWW onto TiO2-ZnO/AC fitted well with the Freundlich isotherm and were found to be endothermic in nature with physisorption being the rate determining step. An optimum pH of 5 for the degradation process was determined. The robustness of the composite TiO2-ZnO/AC photocatalyst was revealed by its high reusability up to four cycles.
Adsorption of Cr(VI) by iron oxide functionalized polyethyleneimine (PEI) coated activated carbon-silica composites
(Vaal University of Technology, 2020-12-14) Qhubu, Mpho Cynthia; Nomngongo, P. N., Prof.; Pakade, V. E., Prof.
Water scarcity due to limited resources and pollution of the little available water by organic and inorganic contaminants remains as one of the critical issues of the 21st century. Several treatment methods have been developed, with some being used successfully at industrial scale but many challenges including secondary sludge generation, high operation costs, high maintenance costs and high energy input were observed. In this study, the adsorption process was explored as an effective means for the removal of Cr(VI) ions from aqueous solution due to its economic feasibility and use of abundantly available adsorbents. Amongst the many available adsorbents, this work focused on exploring functionalized activated carbons (ACs) as adsorbents for Cr(VI) ions due to their favorable adsorption characteristics which involve large surface area, high porosity, and high radiant stability. The iron oxide functionalized polyethyleneimine activated carbon-silica composites were prepared through co-precipitation of Fe(II) and Fe(III) over Macadamia activated carbon to form the AC-Fe3O4 co-shell which was reacted with tetraethylorthosilicate (TEOS) and the polyethyleneimine (PEI). The different adsorbents prepared were labelled AC-Fe3O4, AC-Fe3O4-SiO2 and AC-Fe3O4-SiO2-PEI. The adsorbents were further characterized using elemental analysis (CHNS), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), transmission electron spectroscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FTIR displayed successful attachment of Fe3O4 and SiO2 with bands at 404 and 786 cm-1 being assigned to the asymmetric vibration of Fe-O and Si-O-Si while the asymmetric stretch of Si-OH is observed at 1066 cm-1. XRD showed the presence of magnetite particles in the adsorbents confirmed by the JCPDS 00-019-0629. EDS revealed the presence of Fe, Si, and N atoms which can relate to successful incorporation of the desired functional groups. Each of these materials were evaluated for their Cr(VI) ion removal through batch adsorption experiments where one parameter at a time was varied while all others were fixed. The parameters investigated included the effect of pH, contact time, initials Cr(VI) concentration, adsorbent dosage concentration and temperature. The optimum conditions were obtained at pH 3, initial concentration 2.5 mg/L, contact time of 120 min for AC-Fe3O4-SiO2-PEI. The optimization of each parameter was done in order to determine the conditions in which the adsorbents work best in the uptake of Cr(VI). All the three studied adsorbents showed acceptable adsorption performance for the removal of Cr(VI) from aqueous solutions. Adsorption isotherms studied confirmed that the adsorption data in all the three adsorbents fitted well into the Langmuir isotherm, demonstrating a homogeneous monolayer coverage. Regarding the kinetic studies, the adsorption data were best described by the pseudo-second order rate model with R2 values of 0.974, 0.974 and 0.962 for AC-Fe3O4, AC-Fe3O4-SiO2 and AC-Fe3O4-SiO2-PEI, respectively. The adsorption capacity observed from the present study (6.62, 3.92 and 5.48 for AC-Fe3O4, AC-Fe3O4-SiO2 and AC-Fe3O4-SiO2-PEI, respectively) were satisfactory and suitable as compared to those reported in literature. Thermodynamics data of the adsorption processes revealed a feasible spontaneous endothermic adsorption process which also confirmed that the reaction process occurred through chemisorption.
Adsorption of nitrate and fluoride anions from aqueous solutions using doped magnetite-pinecone nanocomposites
(Vaal University of Technology, 2022-03-23) Frans, Nonhlanhla; Ofomaja, A. E., Prof.; Akpotu, S., Dr.; Pholosi, A., Prof.
The increasing rate of pollutants, such as nitrate and fluoride from industrial and agricultural sources in the environment, especially in water bodies, is becoming alarming. Excessive nitrate and fluoride concentration in water cause environmental toxicity and hazard such as eutrophication and toxic, chronic illnesses such as methemoglobinemia. Hence, there is an urgent need to remove these pollutants from water. There have been a few successful strategies for the purification of pollutants contaminated water. Adsorption has been applied to remove pollutants from aqueous media due to its flexibility, ease of use, cost-effectiveness and ability to adsorb contaminants at low concentrations. Various adsorbents have been applied to remove nitrate and fluoride anions, and doped magnetic has shown to be effective in removing these anions. In this study, manganese doped magnetite coated pinecone (Mn-MNP-PCP) and lanthanum doped magnetite coated pinecone (La-MNP-PCP) nanocomposite were prepared using the co-precipitation method. Fourier Transform Infra-Red (FT-IR), Scanning electron microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDS), Thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) were used to determine the surface groups, structure and morphology, chemical composition, thermal stability and phase determination (amorphous or crystalline) structure of the synthesised Mn-MNP-PCP and La-MNP-PCP adsorbents, respectively. In addition, batch adsorption experiments were conducted to evaluate the effects of solution pH, adsorbent dose, initial solution concentrations, contact time, adsorption kinetics, adsorption isotherm and the impact of co-existing anions on the adsorption of nitrate and fluoride ions. The mechanism of adsorption processes was also determined using equilibrium isotherm modelling results and thermodynamic parameters. The maximum adsorption capacity of Mn-MNP-PCP and La-MNP-PCP adsorbents for nitrate adsorption was 22.8 mg/g and 37.7 mg/g at solution pH 4, while the adsorption efficiency was 45.6% and 75.4%. Fluoride removal occurred at pH 2 with the adsorption capacity of 46.2 mg/g and 44.77 mg/g with the removal efficiency of 92.4 % and 89.6% on both Mn-MNP-PCP and La-MNP-PCP adsorbents. The optimum adsorbent dose for both Mn-MNP-PCP and La-MNP-PCP in the adsorption of nitrate and fluoride was 1 g/L. The optimum time for the uptake of nitrate and fluoride onto MNP-PCP and La-MNP-PCP was between 15 – 20 min. The competing phosphate and sulphate ions impacted the nitrate adsorption, while the presence of carbonate and chloride had positive nitrate adsorption onto both Mn-MNP-PCP and La-MNP-PCP nanocomposites. The decrease in nitrate adsorption may be attributed to the lower affinity of Mn-MNP-PCP and La-MNP-PCP for nitrate and a competition between the nitrate ions and co-existing anions for the active sites. The presence of all competitive ions decreased the fluoride adsorption onto Mn-MNP-PCP and La-MNP-PCP nanocomposites. The multi-valent anion with higher charge density have been reported to be more readily adsorbed than monovalent anion. The equilibrium data for nitrate and fluoride ions uptake was best described by Langmuir isotherm, which predicts the formation of ionic or covalent chemical bonds between the adsorbent and adsorbate. In the same vein, pseudo-second-order model is considerably suitable for nitrate and fluoride ions adsorption, which showed that their uptake was fast. Conclusively, La-MNP-PCP adsorbent is an effective adsorbent for nitrate adsorption, while Mn-MNP-PCP effectively trmoved fluoride ions from the aqueous solution.
Adsorption studies of toxic metal ions (Co(II), Ni(II), Cu(II), Cr(VI) and Pb(II)) and methylene blue using black cumin (Nigella sativa L.) seeds
(Vaal University of Technology, 2021) Thabede, P. M.; Xaba, T., Dr.; Naidoo, E. B., Prof.; Shooto, N. D., Dr.
High levels of pollutants in water are found to have poisonous effects on human health. Due to increasing awareness about the environment and strict environmental regulations, wastewater treatment has become a very important aspect of research. Thus, this makes the adsorption of pollutants an urgent matter. The aim of this research was to investigate the adsorption capacity of black cumin seeds in the removal of cobalt-Co(II), nickel-Ni(II), copper-(II), chromium-Cr(VI), lead-Pb(II), and methylene blue (MB) dye from aqueous solution. In this research work the black cumin seeds were reacted with sodium hydroxide (NaOH), hydrochloric acid (HCl), phosphoric acid (H3PO4), potassium permanganate (KMnO4) and sulfuric acid (H2SO4). Thereafter it was carbonized at 200 and 300 °C and functionalized with magnetite-sucrose nanoparticles and further carbonized at 600 °C to improve the adsorption capacity of the materials towards different pollutants. The seeds were characterized by scanning electron microscopy (SEM), thermogravimetric analyser (TGA), X-ray diffractometer (XRD), Brunauer, Emmett and Teller (BET) and Fourier transformed infrared (FTIR) spectroscopy. The SEM images showed that the surface morphology of the treated adsorbents was more porous and had cavities more than the starting material. The TGA profile showed a major weight loss between 198-487 °C which was due to disintegration of cellulose, lignin and hemicellulose. The XRD spectra of adsorbents showed broad peaks at 2θ value of 21° associated crystalline lignocellulose content. FTIR results showed that the adsorbents had functional groups such as hydroxyl (-OH), carboxyl (-COOH), amide (-NH) and carbonyl (-C=O). The BET surface area of pristine black cumin seeds was 2.7 m2/g and increased after treatment with KMnO4 and H3PO4 to 10.1 and 9.3 m2/g respectively. The surface area of the carbon black cumin seeds was 11.67 m2/g whilst the activation of carbon from black cumin seeds with 10 and 20% H2SO4 gave the surface area of 20.14 and 21.54 m2/g respectively. The seeds activated with 20% H2SO4 showed larger pore width of 7.13 nm compared to 6.81 and 3.78 nm after treatment with 10% H2SO4 and carbon black cumin seeds respectively. The results show that there is an increase in surface area and pore size for both 10 and 20% H2SO4 in comparison with carbon black cumin seeds. The adsorption of Co(II), Ni(II), Cu(II), Cr(VI) and Pb(II) and MB in the solution was investigated by studying the effect of initial concentration, contact time, temperature and pH. The batch adsorption experiments were conducted using different ion solution concentrations of 20, 40, 60, 80 and 100 mg/L, contact time was determined at intervals of 1, 5, 10, 15, 20, 30, 60, 90 and 120 min, while temperature was studied at 298, 303, 313, 333 and 353 K. On the other hand, the effect of pH on all solutions was studied at pH 1, 3,5,7 and 9. The results showed that the acid treated black cumin seeds (AT-BCS) and base treated black cumin seeds (BT-BCS) were successfully used for quaternary adsorption study of Cu(II), Co(II), Pb(II) and Ni(II) ions from aqueous solution. The results for the adsorbents indicated that the BT-BCS adsorbed more metals than AT-BCS and the UT-BCS. The maximum capacity for BT-BCS was 190.7 mg/g for Cu(II) whilst AT-BCS and UT-BCS showed capacities of 180.1 and 135 mg/g respectively for Pb(II). The uptake of Cr(VI) and Cd(II) ions onto pristine black seeds (PBS), KMnO4 black seeds (KMBS) and H3PO4 black seeds (H3BS) treated adsorbents showed that the trend for Cr(VI) ions was KMBS>H3BS>PBS with capacities of 16.12, 15.98 and 10.15 mg/g respectively. Meanwhile the adsorption of Cd(II) ions showed maximum capacities of 19.15, 19.09 and 16.80 mg/g for KMBS, H3BS and PBS respectively. Carbon from black cumin (CBC) seeds was modified with 10 % and 20 % sulfuric acid (H2SO4) then carbonized at 200 °C to obtain the activated adsorbents of ACBC-10 and ACBC-20. The new adsorbents were used for the adsorption of Cd(II) and methylene blue (MB). The adsorbents maximum trend for Cd(II) was ACBC-10>ACBC-20>CBC meanwhile the trend for methylene blue (MB) dye was ACBC-20>ACBC-10>CBC. The overall capacities showed that the prepared materials adsorbed more MB dye (16.42 mg/g) than Cd(II) ions (13.65 mg/g). The preparation of carbon from black cumin seeds (BCC) and activation with 10 and 20 % sulfuric acid (H2SO4) at 300 °C to obtain new adsorbents namely (BCAC-10) and (BCAC-20) respectively was used for the adsorption of Pb(II) ions and MB dye from aqueous solution. The maximum adsorption of Pb(II) ions was 17.19, 17.71 and 17.98 mg/g onto BCC, BCAC-10 and BCAC-20 respectively. Whilst for MB dye it was 11.63, 12.71 and 16.85 mg/g onto BCC, BCAC-10 and BCAC-20 respectively. The utilization of pristine Nigella Sativa (PNS) and magnetite-sucrose functionalized Nigella Sativa (FNS) seeds as the adsorbents for the uptake of Cr(VI) and Pb(II) ions from synthetic wastewater revealed that the maximum adsorption capacities for Cr(VI) were 15.6 and 13.0 mg/g onto PNS and FNS composites respectively at pH 1. On the hand, the maximum sorption capacities for Pb(II) ions were 39.7 and 37.9 mg/g onto PNS and FNS respectively at pH 5. The sorption study of Cr(VI), Cd(II) ions and MB dye by pristine Nigella Sativa (PNS) seeds, defatted and carbonized Nigella Sativa seeds from aqueous solution was investigated. The PNS seeds were treated using acetone (then named ANS) and N,N dimethylformamide (named DNS). The defatted ANS and DNS adsorbents were carbonized at 600 °C and named CANS and CDNS. The results of pristine, defatted and carbonized seeds maximum capacities were compared with each other and found that CANS had highest adsorption capacity of 99.82 mg/g for MB, 96.89 mg/g for Cd(II) and 87.44 mg/g for Cr(VI) followed by CDNS with 93.90, 73.91 and 65.38 mg/g for MB, Cd(II) and Cr(VI) respectively. ANS capacities were 58.44, 45.28 and 48.96 mg/g whilst DNS capacities were 48.19, 32.69 and 34.65 mg/g for MB, Cd and Cr(VI) respectively. PNS had the lowest sorption capacities at 43.88, 36.01 and 19.84 mg/g for MB, Cd and Cr(VI) respectively. Therefore, this makes black cumin seeds a promising material for use in wastewater treatment to mitigate metal ions and dye pollution.
An adsorptive study of Pb(II), Cr(VI) ions and methylene blue dye by treated and untreated coral limestones in aqueous solution
(Vaal University of Technology, 2021) Nkutha, Cynthia Sibongile; Naidoo, E. B., Prof.; Shooto, N. D., Dr.
For centuries the contamination of surface water has been problematic, especially in third world countries whereby socio-economic issues are prevalent. With the development of various technologies for surface water rehabilitation, adsorption has been found to be the most viable due to its lower cost implications. As such the development of innovative adsorbents which are synergistic to the low cost method have been sought. Herein, the use of fossil coral limestone from Mauritius as adsorbents for the removal of Pb(II), Cr(VI) and methylene blue is presented. The pristine material (PCLS) was thermally treated by calcination to temperatures 800°C (CLS-800) and 900°C (CLS-900) and chemically treated by using an acid HCl (ACL) and base NaOH (BCL). The optimum conditions found for chemical and thermal treatment of the pristine material were used for the one pot synthesis of magnetite and maghemite calcium carbonate based nanocomposites. The pristine fossil coral limestones were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray fluorescence XRF), X-ray diffractometer (XRD), Brunauer, Emmett and Teller (BET) and Fourier transformed infrared (FTIR) spectroscopy, UV visible spectrophotometer (UV/vis) and Photolumiscent spectroscopy (PL). Surface morphology of the material was found to contain an interconnected framework of pores, with a surface area of 20.45 m2/g and pore with of 4.04 nm. Thermal treatment of the material was found to increase the surface area of the materials to 64.10 and 63.28 m2/g for CLS-800 and CLS-900. The surface morphology of the calcined materials compared to the pristine were fibrous like and irregularly shaped for CLS-800 and CLS-900 respectively. The FTIR revealed the dominant surface groups to be (-C-O) and (-C=O) asymmetric stretch of the in and out of plane bend of carbonate (-CO32-), with the composition of the material being 91.76 % (-CaO) and 3.32% SrO. The thermally treated materials also exhibited vibrations of asymmetric stretch, which are characteristics of the carbonates as with the pristine material. However, EDS of the pristine compared to that of the calcined materials show a decline in the carbon and oxygen content, due to calcination. The XRD analysis confirmed the orthorhombic structure of aragonite, while CLS-800 was rhombohedral calcite with newly developed (-CaO) peaks. CLS-900 showed complete removal of CaCO3 polymorphs with more (-CaO) peaks. The surface morphology of the chemically modified samples show irregularly shaped surface. The XRD analysis confirmed that chemical treatment did convert the materials to a different polymorph. The FTIR of the chemically modified materials compared to the pristine, were found to reveal a removal of the vibrations of the asymmetric stretch associated with carbonates. However, vibrations associated with (-CaO) were observed. The SEM of the nanocomposites was observed to deviate from sphericity with variable size distribution. The materials were both red and blue shifted due to their variable sizes. Their UV/vis revealed absorption bands in the visible region. The adsorption analysis was done by varying parameters such as time, pH, concentration and temperature. The data was such that the highest capacity for the pristine material was found to be 37.24, 39.26 and 69.42 mg/g for MB, Pb(II) and Cr(VI) respectively. The removal of MB and Pb(II) pollutants were due to physical adsorption, as observed from the good fitting to pseudo first order model (PFOM). The removal of Cr(VI) was due chemisorption and the good fit on pseudo second order model (PSOM). The adsorption process was supported on a heterogeneous surface whereby multilayer adsorption could occur. Adsorption was spontaneous and feasible, exothermic for MB and Pb(II) and endothermic for Cr(VI) at all the studied temperatures as observed from thermodynamics. The adsorption of methylene blue was found to be more favourable on adsorption compared to photo-degradation Chemical modification was observed to increase adsorption and the maximum removal capacities for PCLS, ACL and BCL for Cr(VI) ions were 69.42, 65.04, 64.88 mg/g, Pb(II) ions 39.36, 74.11, 78.34 mg/g and methylene blue 37.24, 46.28, 46.39 mg/g, respectively. Uptake of Cr(VI) and methylene blue on ACL and BCL was feasible on a heterogeneous surface whereby multilayer adsorption took place. Monolayer adsorption on a homogenous surface of ACL and BCL was observed for Pb(II) uptake. The uptake of Pb(II) was exothermic on PCLS and ACL while methylene blue only on PCLS. The adsorption of Cr(VI) ions onto PCLS, ACL and BCL and methylene blue dye onto ACL and BCL were endothermic in nature. The adsorption process was spontaneous and feasible at all the studied temperatures. Thermal modification further increased the adsorption uptake of the pollutants. The recorded uptake for Cr(VI) and Pb(II) were 99.12 and 98.42 mg/g onto CLS-800 and CLS-900, respectively. The adsorption process was found to be physisorption, due to the good fit on PFOM. In addition, the adsorption occurred on a heterogeneous surface whereby multilayer adsorption was possible. The removal of Cr(VI) was found to be exothermic for both the materials and Pb(II) was found to be endothermic. The materials were tested for their reusability to up to four cycles, whereby the removal on the fourth cycle were 16.87, 63.60, 73.13 mg/g for Cr(VI), 9.87, 64.19 and 70.95 mg/g for Pb(II) on PCLS, CLS-800 and CLS-900. While the leaching test for PCLS, CLS-800 and CLS-900 for the release of Ca2+ into solution was found to be within the permissible limits of world health organisation (WHO). The as synthesized nanocomposites increase adsorption of the pollutants. Maximum capacities were found to be 345.34, 388.31, 377.92 and 375.35 mg/g for Pb(II) onto magnetite-PCLS, magnetite-CLS, maghemite-PCLS and maghemite-CLS, respectively and 308.01, 335.3, 335.29 and 335.27 mg/g for Cr(VI) onto magnetite-PCLS, magnetite-CLS, maghemite-PCLS and maghemite-CLS, respectively. From the data it was observed that the maghemite samples were much more favourable for the removal of the pollutants. The removal was due to chemical adsorption, as observed from the good fit onto PSOM and intraparticle diffusion (IPD), whereby surface adsorption was the rate limiting step. The adsorption process was heterogeneous and multilayer, while thermodynamic data reveal that adsorption was spontaneous and favourable at the studied temperature.
Alanine, aspartic acid and lactose-capped CuS, ZnS and FeS nanoparticles: synthesis, characterization and properties
(Vaal University of Technology, 2017) Mofokeng, Thapelo Prince; Shumbula, P. M., Dr.; Moloto, M. J., Prof.
Water soluble metal sulfide nanoparticles were successfully synthesized using an aqueous, simple and environmentally friendly synthetic method in the presence of ʟ-alanine, ʟ-aspartic acid and lactose, acting as both stabilizers and crystal growth modifiers. The structural and optical properties of the synthesized metal sulfide nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Ultraviolet-visible (UV-Vis) and photoluminescence spectroscopy. Colloidal method was employed in the synthesis of CuS, ZnS and FeS nanoparticles from metal chlorides as precursors and thioacetamide (TAA) as a sulphur source. The effect of temperature on the growth and solubility of nanoparticles was investigated. The absorption spectra of all samples prepared were blue shifted as compared to their bulk materials indicating small particles size. The morphologies and sizes of the nanoparticles were influenced by the variation of temperature and capping agent. TEM images revealed interesting changes in the morphology of CuS nanoparticles formed from various capping agents. By varying the temperature, ʟ-aspartic acid-capped CuS nanoparticles changed from rod-shaped particles to particles dominated with hexagonal shape. However, the morphologies of both ZnS and FeS nanoparticles were close to spherical shape and were unaffected by either change of temperature or capping agent. Water-solubility of bio-functionalized CuS, ZnS and FeS nanoparticles was investigated. Amongst the three capping agents used, ʟ-alanine (Ala) was found to be the most effective capping agent to render solubility of the nanoparticles. As the temperature was increased, the solubility of the particles also increased. Cytotoxicity and antimicrobial activity of ʟ-alanine-capped CuS and ZnS nanoparticles were investigated. The particles were less toxic at low to moderate concentrations and only induced toxicity at higher concentrations. Particles synthesized at 95 °C were less toxic compared to other nanoparticles (35 and 65 °C) for both two set of experiments, as informed by the CC50 values. Antimicrobial properties were tested using different strains of both positive and negative bacteria and fungi. It was found that Ala-capped CuS nanoparticles were more effective against the bacteria than Ala-capped ZnS nanoparticles.
Amino acid-capped metal selenide nanoparticles: their synthesis, characterization, optical and magnetic properties
(2018-04) Mokubung, Kopano Edward; Moloto, N; Moloto, M. J.
Quantum dots (QDs) have already proven features that can be considered to improve their properties for biological applications. Metal selenide nanoparticles possess semiconducting behaviors that can vary with structural and optical properties evolving from their synthesis. An aqueous medium through a simple, non-toxic and environmentally friendly colloidal route for the preparation of water-soluble CdSe, Cu2Se, FeSe semiconductor nanoparticles has been developed. Different capping molecules with multi-functional moieties (-COOH, -NH2 and -OH) namely, L-cysteine, L-glutamic acid and L-phenylalanine, have been employed in the preparation of cadmium selenide, copper selenide and iron selenide semiconductor nanoparticles as capping molecules. The synthesized metal selenide nanoparticles were characterized by Fourier Transform Infrared (FTIR), UV-Vis spectroscopy, Photoluminescence spectroscopy (PL), X-ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and Transmission Electron Microscopy (TEM). The FTIR spectroscopy confirmed the binding moiety through the surface of the nanoparticles which is pH dependent. The XRD patterns confirmed a cubic phase of CdSe and Cu2Se while FeSe revealed a hexagonal phase for the synthesized nanoparticles. The optical absorption as a function of wavelength for the prepared nanoparticles at different temperature is investigated. The morphology of the nanoparticles dominated through this method was spherical in shape. Amino acids capped metal selenide nanoparticles were successfully synthesized by aqueous medium through a simple colloidal route. The absorption spectra of all samples prepared were blue shifted as compared to their bulk counterparts which signify quantum confinement effect. The optical absorption measurements show some dependency of the temperature values used in the synthesis of nanoparticles. The effect of temperature and pH on the growth and morphology of nanoparticles was investigated. X-ray diffraction patterns confirms the structure, single cubic and hexagonal phase for the synthesized nanoparticles. TEM studies of metal selenide nanoparticle show that particle size increases with the increase in reaction temperature. The vibrating sample magnetometer (VSM) shows almost linear without any hysteresis loop for copper selenide, which indicated the absence of magnetism and exhibits paramagnetic nature than diamagnetic properties while iron selenide revealed twofold ferromagnetic behavior in low fields and paramagnetic behavior in up fields.
Analysis and application of semantic web mechanism for storing and querying ontologies
(Vaal University of Technology, 2017-02) Kwuimi, Raoul; Fonou-Dombeu, J. V., Dr.
Since the introduction of Semantic Web in the early 2000, storing and querying ontologies have been a subject of greater research. Thus, several types of storage media and mechanisms have been developed to increase storage and query speed and efficiency of ontologies in Semantic Web applications. Existing Semantic Web mechanisms for storing and querying ontologies are implemented on several storage media and support different languages. However, there is a shortage of studies that provide an empirical analysis and application of these ontology storage and query mechanisms in the Semantic Web domain. This study conducted an analysis and application of the Semantic Web mechanisms for storing and querying ontologies. A thorough literature review was carried out to identify relevant publications pertaining to existing Semantic Web mechanisms for storing and querying ontologies as well as the platforms and storage media for implementing these mechanisms. Thereafter, the Design research method was used consisting of a set of predefined steps, namely, awareness, suggestion, development, evaluation, and conclusion. The awareness stage identified the need for an architecture to test several ontology storage media and mechanisms. In the suggestion stage a framework was proposed to empirically analyse and evaluate existing ontology storage and query mechanisms. The required Semantic Web platforms were identified to implement the framework in the development stage. The evaluation stage used a set of metrics to evaluate the framework including: the loading times of ontologies, the disc space used to store the ontology repositories and the mean and variance of query response times. Further, the evaluation stage analysed and discussed the storage mechanisms implemented in Semantic Web platforms. Finally, the outcome of the performance of the framework is presented in the conclusion stage. The framework was practically tested with six ontologies of different formats and sizes on two popular Semantic Web platforms, namely, Sesame and Jena API and the ontology storage and query mechanisms were analysed and compared. Although the underlying structures of repositories in the in-memory and native files in Jena and Sesame could not be accessed, it was possible to access and analyse the data in the repositories in the relational database storage in both Sesame and Jena. The results showed that Sesame relational uses a combination of mechanisms such as normalized triples store in combination with vertical partitioning. That combination allows Sesame to store ontologies based on their contents; in other words, each ontology has a different database schema in Sesame. Jena on the other hand, uses only a normalized triple store mechanism, also known as generic schema mechanism to store ontologies; thus, all ontologies in Jena have the same database schema. The study would be useful to the Semantic Web and Computer Science communities as it does not only provide theoretical knowledge but also the empirical findings that may serve as a base for further development of ontology storage media and mechanisms.
The antifungal activity and bioanalysis of fractions from Tulbaghia violacea (leaf and root) acetone extracts.
(Vaal University of Technology, 2022-12) Makgati, Mogau Mafise Brian; Mitema, A. Dr.; Takaidza, S. Dr.
Infectious diseases represent a critical problem to health and cause morbidity and mortality worldwide. Despite the significant progress in human medicine, infectious diseases caused by microorganisms such as fungi are still a major threat to public health. Tulbaghia violacea is one medicinal plant that has been used traditionally to manage fungal infections. The present study aimed to determine the antifungal activity and perform bioanalysis of acetone fractions from T. violacea extracts. Tulbaghia violacea crude leaf and root acetone extracts and their fractions were tested against seven fungal species for antifungal activity. The plant extracts were prepared using the maceration method, and column chromatography was utilized to obtain fractions. The plant extract’s total phenolic and flavonoid contents were determined using the Folin-Ciocalteu and aluminum chloride colorimetric methods, respectively. The antioxidant activity was evaluated using the free radical scavenging methods 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS•+) assays. The antimicrobial activity of T. violacea crude leaf and root extracts and their fractions was determined using the well diffusion, microtiter, and time-kill assay. The compounds present in the T. violacea leaf and root extracts and their fractions were determined using GC-MS. The results indicated that the total phenolic content (TPC) of all four samples of T. violacea leaf extracts ranged from 0.597-5.003 mg of Gallic acid equivalent/g, whereas total flavonoid content (TFC) varied between 5.324- 15.844 mg of Quercetin/g. The TPC and TFC of all root extracts ranged between 3.19-8.41 mg of GAE/g and 10.28-12.40 844 mg of QE/g, respectively. DPPH leaf fractions ranged from 48-50% and 60-61% for root extracts at 0.5 mg/mL. The ABTS assay also showed a dose-dependent radical scavenging activity. The scavenging activity ranged between 92-95% (crude leaf extract and fractions) and 77-84% (crude root extract and fractions). The investigations using GC-MS revealed a total of 21 metabolites with varied phytochemical activity. For antimicrobial activity, all T. violacea leaf and root acetone extracts and their fractions suppressed the growth of all fungal strains with leaf extracts zones of inhibition ranging between 3-18 mm whereas the root extracts ranged between 3.3-21 mm. The MIC of leaf and root acetone extracts and their fractions ranged between 0.78-12.5 mg/mL and 0.39-12.5 mg/mL, respectively whereas the MFC values of the plant leaf and root acetone extracts and their fractions ranged between 0.78- ˃ 50 mg/mL and 0.39-25 mg/mL, respectively. The time-kill curve assay demonstrated that most of the leaf extract and their fractions at 2 MIC demonstrated fungistatic activity averaging 3-6.23 log10 kill against C. albicans whereas, almost all root extract and their fractions demonstrated fungicidal activity, averaging 0.04-3 log10 kill. The membrane permeability assay indicated membrane damage in a dose-dependent manner for all extracts. In conclusion, T. violacea possesses phytocomponents with good potential as antifungals.
Antimicrobial activity and dye photodegradation of titanium dioxide nanoparticles immobilized on polyacrylonitrile-cellulose acetate polymer blended nanofibers.
(Vaal University of Technology, 2019) Nkabinde, Sibongile Chrestina; Matabola, K. P., Dr.; Moloto, M. J., Prof.
Electrospinning is a method that has gained more attention due to its capability in spinning a wide variety of polymeric fibers and nanoparticles embedded in polymer fibers. Polymer blending has been considered the most appropriate way for creating new materials with fused properties which improve poor chemical, mechanical, thermal and dynamic mechanical properties of each polymer. Hence, in this study, electrospinning technique was used to fabricate polyacrylonitrile (PAN) nanofibers at concentrations of (10, 12 and 14 wt%) and cellulose acetate (CA) nanofibers at concentrations of (14, 16 and 18 wt%). 10wt% of PAN and 16 wt% of CA were blended together and the optimum blend ratio was found to be 80/20 PAN/CA. TiO2 nanoparticles (0.2 and 0.4 wt%) were incorporated into CA nanofibers and (1, 2 and 3 wt%) were incorporated into PAN and PAN/CA blended polymers, respectively. Applied voltages of 20, 22 and 24 kV were varied at a spinning distance of 15cm and the optimum voltage for the fabrication of composite was 22 kV. The sol-gel method was used to synthesise the TiO2 nanoparticles at different calcination temperatures of 400, 500 and 600 ºC. The fabricated composite nanofibers were tested for antibacterial and photocatalytic activities. The synthesised nanomaterials were characterized using SEM, TEM, EDX, UV-Vis, PL, FTIR spectroscopy, XRD and TGA. The absorption and emission spectra illustrated the formation of TiO2 nanoparticles and the increase in absorption band edges. TEM showed the spherical morphology of the nanoparticles with average diameter of 12.2 nm for nanoparticles calcined at 500 ºC. SEM illustrated the diameter and morphology of the nanofibers and composites with the average diameter of 220, 338, 181, 250, 538, 294 nm for PAN, CA, PAN-TiO2, CA-TiO2, PAN/CA and PAN/CA-TiO2, respectively. XRD revealed anatase phase as the dominant crystalline phase of the synthesised nanoparticles. FTIR spectroscopy and EDX signified that the formation of composite nanofibers and the presence of TiO2 nanoparticles corresponded to the Ti-O stretching and Ti-O-Ti bands on the FTIR spectra. The antimicrobial activity of the composite nanofibers were tested against E. coli, S. aureus and C. albicans microorganisms. The photocatalytic activity of the nanomaterials was tested using methyl orange dye. PAN/CA-TiO2 composite nanofibers revealed the greatest antibacterial activity against selected microorganisms as compared to the other nanocomposites. PAN/CA-TiO2 nanocomposite (44%) showed greater rate of photodegradation of methyl orange than PAN-TiO2 nanofibers (28%) and TiO2 nanoparticles (12%) under visible light irradiation.
Antimicrobial activity of synthesized copper chalcogenides nanoparticles and plant extracts.
(2019-03) Mbewana, Nokhanyo; Mubiayi, Kalenga Pierre, Dr; Mthunzi, Fanyana, Dr; Moloto, Makwena Justice, Prof
Chemical precipitation method is the most widely used of all methods for preparing good quality semiconductor nanoparticles. Several conditions are optimized for producing the desired size and shape of particles. The parameters such as capping molecule, precursor concentration, time and temperature were investigated using the colloidal hot injection method. The effect of capping agent was the first parameter investigated in the synthesis of copper selenide, copper sulphide and copper oxide nanoparticles. The capping agents of interest in this study were oleylamine (OLA) and trioctylphosphine (TOP), due to their ability to act as reducing agents, surfactant, solvent and enhancement of colloidal stabilization. The use of oleylamine and trioctylphosphine were carried out at 220 °C for 30 minutes. The optical and structural properties of the yielded nanoparticles were characterize using UV/Vis spectroscopy, TEM and XRD and showed dependence on the type capping interactions from the two agents. Nanoparticles synthesized using TOP produced two phases whereas a single phase was observed from OLA as confirmed by XRD. OLA produced bigger particle sizes compared to TOP but with a wider variety of shapes. The wide variety of particle structures of OLA capped nanoparticles was advantageous since different types of bacteria were targeted in this work. Therefore, other synthetic parameters were investigated using OLA as both solvent and capping molecule. Precursor concentration ratio showed bigger effect in the size, and shape of the yielded nanoparticles. For copper selenide and copper sulphide (Cu: Se/ S), 1:1 concentration ratio gave the best optical and structural properties while copper oxide (CuO) nanoparticles demonstrated its best optical and structural properties in 2:1 ratio (Cu: O). Nonetheless, 1:1 precursor concentration ratio was used to optimise other parameters. Since reaction time has a profound effect on the nanocrystals size and shapes, the effect of reaction time in OLA was also investigated. The reaction time showed no effect on the phase composition of the synthesized copper sulphide, copper oxide and copper selenide nanoparticles. Reaction time of 30 minutes gave the best optical (the shape of the absorption band edge and emission maxima values) and structural (size distribution of particles) properties for CuSe and CuS compared to other reaction times (15 min, 45 and 60 min). 15 min reaction time gave the best optical and structural properties for copper oxide but nonetheless, 30 min was used as the optimum reaction time for further optimization. Temperature showed an effect in size, shape and the stoichiometry of the reaction. These effects were confirmed by the optical and structural properties of the synthesized nanoparticles. XRD patterns revealed some differences with the temperature change, indicating an effect on the phase composition of CuS and CuO but not on CuSe nanoparticles. CuSe and CuS nanoparticles synthesized at 220 °C gave the ideal optical and morphological features compared to other temperatures that were selected (160 ºC, 190 ºC and 240 ºC). Nonetheless, CuO revealed its best optical and structural properties at 160 ºC. 220 ºC was deduced to be the optimum temperature for the synthesis of these three materials under the synthetic conditions. The optimum parameter (220 ºC, 30 min and 1:1 ratio) were used to synthesize the three copper chalcogenides which were then tested against Gram-negative (E. coli and P. aeruginosa), Gram-positive (S. aureus and E. faecalis), and fungi (C. albicans). The plant species, Combretum molle and Acacia mearnsii were phytochemical screened for the presence of active organic compounds and the content of total phenols, flavonoids and antioxidants using different solvents. Both C. molle and A. mearnsii revealed the highest phenolic content in acetone extracts. C. molle revealed its highest flavonoid content in methanol extract and its highest free radical scavenging activity in acetone extract. Acetone extracts demonstrated the highest flavonoid content as well as the highest free radical scavenging activity of A. meansii. The solubility of copper chalcogenides and plant extract was tested in four different solvents and the solvent that demonstrated highest solubility was used for the coordination of the plant extract and copper chalcogenides. The plant extract coordinated nanoparticles were tested for their antibacterial and antifungal activity. Their results were compared to those of the active ingredient in their respective solvents from the medicinal plants as well as those of copper chalcogenides nanoparticles without plant extracts using diffusion disk and MICs methods. The synthesized nanoparticles showed better performance than plant extracts with copper oxide performing the best, followed by copper selenide and lastly by copper sulfide. The performance of plants extracts highly dependent on the solvent of extract with acetone showing the best performance for both C. molle and A. Mearnsii followed by ethanol. The addition of active ingredients from C. molle and A. mearnsii to the synthesized nanoparticles did not enhance the performance of these nanoparticles.
Antimycobacterial activity of synthetic compounds isolated from South African medicinal plants against mycobacterium tuberculosis
(Vaal University of Technology, 2014-11) Ledwaba, Elizabeth Ramadimetsa; Bapela, N. B., Dr.; Van Wyk, Christa
Tuberculosis (TB) remains one of the most difficult infectious diseases to control in the world today. The disease spreads easily in overcrowded, badly ventilated places and among people who are undernourished. Trends in the incidence of TB together with the development of multi-drug (MDR-TB) and extensively drug resistant (XDR-TB) strains of TB raises the need to intensify the search for more efficient drugs to combat this disease. Herbal remedies used in traditional medicine provide an interesting and largely unexplored source for the discovery of potentially new drugs for infections such as TB. The aim of the study was to evaluate the in vitro antimycobacterial activity of synthesized compounds from medicinal plants against Mycobacterium tuberculosis (M. tuberculosis). About 40 synthesized compounds isolated from South African medicinal plants were screened against H37RV using microplate alamar blue assay (MABA). Identified active compounds were screened against resistant strains of M. tuberculosis (MDR, XDR and pre-XDR) and sensitive clinical isolates of TB. Cytotoxicity and synergistic drug combination studies were done on active compounds to validate their toxicity and synergy levels. Cytotoxicity was done by sulforhodamine assay (SRB) against the C2C12 cell line. Only six compounds showed activity against M. tuberculosis with minimum inhibitory concentration (MIC) below 10μg/ml. The results obtained indicated that the cytotoxicity effects of the three compounds on C2C12 cells demonstrated marginal toxicity except for MVB 282/61215 which showed a high toxicity at the lowest concentration of 0.156μg/ml with over 100% viable cells at the highest concentration (5μg/ml). MVB 282/61271 had the highest percentage cell viability (65%) at the lowest concentration. Only two compounds had a higher potency evoking a bigger response at low concentrations with treated cells still viable after 3 days of incubation with the compound which was comparable with the treatment of isoniazid (INH). Synergistic activity of the six compounds was less in INH combination as compared to the rifampicin’s (RIF) combination. The results demonstrated that the synergistic interaction between the compounds and RIF could the antituberculosis acitivity. In conclusion the synergistic effects with RIF translate to lower dosing requirements of the compounds and the potential to combat multidrug resistant TB. In deed there is no doubt that natural products, with their range of interesting chemical structures and powerful antimycobacterial effects are certain to remain important participants in the development of new generations of antimycobacterial drugs.
An approach to a creative pedagogy to improve the learner-content relation in Tertiary ICT education in South Africa.
(Vaal University of Technology, 2018-12) Van Eck, Rene; Jordaan, A., Prof
The work-integrated learning (WIL) concept was introduced to enhance the employability of students completing their IT qualification at universities of Technology (UoTs) in South Africa. Employability is defined as a combination of characteristics that make a person a useful and thereby desirable employee. WIL is defined as a component of a curriculum to improve the value of student learning by integrating academic training and practical workplace exposure. However, a large cohort of students registered for the IT qualification at UoTs do not find company placement for WIL, resulting in these students having to complete this final qualifying module of their qualification by undertaking a group project on campus. The group project entails developing a software system for a client. The overall sentiment expressed by employers, lecturers and students in this study is that students who remain on campus for the group project are not as well-prepared as those who find placement at a company for their in-service training. This study aimed to develop and propose an approach to a creative pedagogy in the form of a simulated working environment on campus within a tertiary educational setting to contribute towards enhancing the learner-content relation of WIL students, in order to improve the employability of students by providing the on-campus project students with an equal opportunity to those going into industry for their in-service training. The philosophy adopted for this research is interpretivism, with the Vaal University of Technology as the case of the research. The investigation adopted a mixed-method approach where respondents were requested to complete questionnaires focusing on their perceptions of on-campus group work vs. in-service training at companies for the WIL component of the IT qualification. Five respondent groups were identified for participation in the study, namely: i) In-service training students, i.e. WIL students who found placement in a company; ii) Project students, i.e. WIL students who remained on campus to do a group project; iii) Graduates, i.e. students who already completed WIL and graduated; iv) Employers of WIL students who found placement at a company; and v) Lecturers involved in WIL training on campus. The responses of the various respondent groups were analysed qualitatively and quantitatively. Comparisons of the perceptions of the respective groups were made to explore the possibility of a viable solution to the on-campus group work challenges that were identified. Based on reviewing recent literature, analysing the data collected from the completed to questionnaires by different role players, and adapting and the institutional strategy framework for WIL developed by Jacobs in 2015, an approach to a creative pedagogy in the form of a virtual company on campus for WIL students is presented to provide students who cannot find placement in industry for their in-service training with an equal experience to the in-service training company students. The proposed pedagogical approach incorporates the five standards defined by Tharp in 2018 as requirements for an effective and successful curriculum in the development of the actual virtual company. These include: contextualisation, challenging activities, joint productive activity, intellectual conversation and language development. The proposed approach adopts a three-layered approach to a creative pedagogy, with the aim of improving the employability of on-campus WIL students. The first layer lays the basis for implementing a virtual company on campus and includes aspects such as the objective for a simulated working environment on campus, employer preferences, and the skills set students should possess for employers to offer them a placement in their company for in-service training. The second layer focuses on the details that should be in place for a virtual company to be successfully implemented. This practical layer in the implementation of the virtual company focuses on infrastructure, Finance, HR, legislative approval, and appropriate assessments. The third layer only follows when the second layer has been put into place. This layer deals with how academic content can be included in the proposed pedagogical approach. The study also revealed that in addition to adopting the concept of a virtual company on campus for WIL students, a substantial focus should be on soft skills training. The exit level outcomes (ELOs) related to a simulated working environment for the WIL module of the IT are specified in the HEQF (Higher Education Qualifications Framework) document as set out by the South African Qualifications Authority.
Assessing methanol and water leaf extracts of Eriobotraya japonica (Thunb) Lindl for anti-diabetic properties
(Vaal University of Technology, 2022-11) Sikhakhane, Maria Nomusa; Pillay, Michael, Prof.; Takaidza, Samkeliso, Dr.
Diabetes mellitus is projected to become one of the world’s leading causes of death and disability in the next 25 years. By 2004, diabetes mellitus was widespread, affecting approximately 25% of the world’s population. Despite developing several drugs, diabetes and its secondary complications remain a major health problem. Many biochemical and chemical agents used to treat hyperglycemia have known side effects. Herbal medicine is used as an alternative form of treatment for diabetes in developing countries where the cost of conventional medicine is still high. This research aimed to assess methanol and water extracts of the leaves Eriobotrya japonica for anti-diabetic properties in vitro. The leaf extracts' bioactive molecules were characterized by thin-layer chromatography (TLC) and Liquid chromatography-mass spectrometry (LC-MS) analysis. The total antioxidant capacity and free radical scavenging activity of the aqueous and methanolic-based extracts were assessed using the DPPH assay. The inhibitory effects of the aqueous and methanolic extracts on alpha-amylase and alpha- glucosidase were examined to evaluate the antidiabetic potential. The qualitative phytochemical analysis showed that pharmacologically active compounds such as tannins, terpenoids, flavonoids, steroids, cardiac glycosides, and phenols were present in the leaves of E. japonica. However, alkaloids were absent in both extracts. The quantitative phytochemical analysis revealed that E. japonica has a lower Total Flavonoids Content (TFC) than Total Phenolic Content (TPC), and this trend was observed in both extracts. The water extract had a TFC of 0.085 ± 0.004 mg of QE/g and TPC of 19.88± 0.2 mg of GAE/g, while the methanol extract had a TFC of 0.084 ± 0.02 mg of QE/g and TPC of 19.10± 0.1 mg of GAE/g. A total of 12 bands were observed on the (TLC) plate of the methanol extract, while none was observed for the water extract. From the (LC-MS), 13 compounds were identified from the water extract of E. japonica. Protocatechuic acid occurred in the highest concentration at 115 mg/L, while Icariside F2; Benzyl beta-D-Apiofuranosyl-(1->6)-O-beta-D-glucopyranoside was found in the lowest concentration of 0.1 mg/L. A total of 14 compounds were characterized from the methanol extract of E. japonica. Blumenin, which belongs to a group of fatty acyl glycosides of mono- and disaccharides, had the highest concentration at 82.7 mg/L, whereas xanthohumol had the lowest concentration at 10.5 mg/L. The 2,2-diphenyl-l-picrylhydrazyl-Thin Layer Chromatography bioautography assay showed that the water extract had 5 bands of compounds with antioxidant activity while the methanol extract showed 6 bands. The free radical scavenging assay was performed using DPPH to qualify antioxidants in E. japanica. The ascorvic acid, methanol, and water extracts had the highest percentage inhibition of 85.9%, and 71.6%, and 40.7%, respectively. The IC50 values for ascorbic acid, methanol, and water extracts were 4.4, 6.1, and 12.2 μg/mL, respectively. Alpha-amylase and alpha-glucosidase activity inhibition assays were performed to determine if E. japonica leaf extracts can slow down the rate at which carbohydrates are digested and absorbed into the blood stream, thus reducing blood sugar levels. The highest concentration of 5 mg/mL of the methanol and the water extracts inhibited 88.5% and 83.01% of alpha-amylase activity, respectively, while acarbose inhibition was at 91.3%. The lowest concentration of 0.0391 mg/mL of the methanol and water extracts inhibited alpha-amylase activity by 40.19% and 22.85%, respectively, while acarbose inhibited the activity by 12.4%. The IC50 values of acarbose, methanol and the water extract were 0.07, 0.03, and 0.06 mg/mL. The highest concentration of 5 mg/mL of the water and the methanol extracts inhibited 72.8% and 77.3% of alpha-glucosidase activity, respectively, while acarbose inhibition was 85.1%. The lowest concentration of 0.0391 mg/mL of the water and methanol extracts inhibited alpha-glucosidase activity by 38.9% and 40.7%, respectively, while acarbose inhibition was 32.0%. The IC50 values of acarbose, methanol and the water extract were 0.03, 0.026, and 0.027 mg/mL. The methanol extract was more potent than the water extract in inhibiting alpha-amylase and alpha-glucosidase activity. The findings from the enzyme activity inhibition assays indicated that E. japonica slows down glucose production and absorption in a dose-dependent manner. Based on the results of this study, it can be concluded that the leaf extracts of E. japonica have bioactive compounds, which can be explored for managing type 2 diabetes.
Assessing the effect of some plant extracts on Fusarium oxysporum f.sp. cubense
(Vaal University of Technology, 2022-12) Tebeila, Mashego Kabelo; Pillay, M., Prof.; Takaidza, S., Dr.
Fusarium oxysporum f.sp.. cubense (FOC) causes fusarium wilt, one of the most destructive diseases of bananas. The management of F. oxysporum through synthetic fungicides causes serious environmental problems and threatens to non-target organisms. Medicinal plants may be a good substitute for synthetic fungicides due to their fewer negative impacts on human and ecological health. This study assessed the antifungal effect of crude extracts of Allium cepa L, Allium sativum L, Curcuma longa L, Tulbaghia violacea Harv, and Zingiber officinale L against FOC. The extracts were prepared using acetone, methanol, and water through maceration. Qualitative phytochemical screening was performed using standard methods. The plant extracts’ total phenolic and tannin content was determined using the Folin Ciocalteu method. Total flavonoids were determined by using the aluminium chloride colourimetric method. The antifungal activity of the extracts was determined by well diffusion, microtiter, and poisoned food techniques. High-Performance Liquid Chromatography (HPLC) profiling of standard phenolic compounds in T. violacea and A. sativum was conducted. Most of the tested phytocompounds were present in the acetone and methanol extracts of C. longa and acetone extract of A. sativum. The total phenol, flavonoid and tannins varied in the different plant extracts ranging from 0.23 to 50.56 mg GAE/g, 0.65 to 17.73 mg QE/g and 2.48 to 129.65 mg TE/g, respectively. The acetone and methanol extracts of T. violacea and A. sativum showed inhibition zones against the FOC (17–26 mm), while the water extract showed no inhibition. The minimum inhibitory concentration of the extracts ranged from 1.56 mg/mL to 50 mg/mL, with T. violacea and A. sativum showing the best activity. The methanol and acetone extracts of T. violacea and acetone extracts of A. sativum fully inhibited the mycelial growth of FOC. HPLC analysis of the extracts with the best antifungal activity revealed the presence of the following phenolic compounds: tannic acid, ascorbic acid, benzoic acid and acetyl acid in the acetone and methanol extracts of T. violacea and acetone extract of A. sativum. This research shows that T. violacea and A. sativum may be used to formulate new, safer, and ecofriendly fungicides for F. oxysporum f. sp cubense. Therefore, plant extracts could be a good alternative in managing fusarium wilt in bananas.
Assessing the effectiveness of the water purification process in removing clostridium perfringens spores as a surrogate for protozoan parasites
(Vaal University of Technology, 2022-12) Schubart, Annah Lindiwe; Swanepoel, Annelie, Dr.; Marrengane, Zinhle; Ssemakalu, Cornelius Cano, Prof.
The World Health Organization (WHO) provides guidelines for assessing the microbiological risk associated with drinking water using a Quantitative Microbial Risk Assessment (QMRA). Microbiological risk in water may arise from pathogens such as protozoan parasites Giardia and Cryptosporidium. The risk presented by Giardia and Cryptosporidium in water is increased by the fact that these pathogens are resistant to disinfection by chlorine. It is costly to monitor treated water for the presence of Cryptosporidium and Giardia, therefore a surrogate was used to carry out the evaluations. This research first determined the efficacy of the conventional water treatment processes in removing Clostridium perfringens spores as a surrogate for protozoan parasites (Cryptosporidium oocysts and Giardia cysts). We estimated the number of protozoan parasites that can pass through the drinking water treatment barriers. This removal efficiency can then estimate the number of protozoan parasites that can survive drinking water purification. The study conducted a simulated jar test under predetermined conditions using three different coagulation combinations: (i) Polyelectrolyte, (ii) polyelectrolyte and slaked lime, and (iii) slaked lime and activated sodium silicate. The three regimens (polyelectrolyte, polyelectrolyte and slaked lime, and slaked lime and activated sodium silicate) were tested each at low temperatures (12.8 ± 0.4°C), normal temperatures (17.2 ± 0.9°C), and at high temperatures (20.3 ± 0.1°C). The three coagulant combinations (polyelectrolyte, polyelectrolyte and slaked lime, and slaked lime and activated sodium silicate) were also tested under normal temperature conditions at high water turbidity. Percentage and log reduction for C. perfringens spores were calculated for each water treatment unit. A percentage reduction for turbidity was calculated for each water treatment unit. Pre-experiments were conducted to determine the suitability of the filter membranes and media to be used for analysing the water samples for the study. The 0.45 μm filter membrane and the Perfringens Agar Base (PAB) were selected and used. Experiments conducted at low temperatures (12.8 ± 0.4°C) showed C. perfringens spore log reductions of infinity or 100% when the polyelectrolyte and a combination of polyelectrolyte and slaked lime were used. Under normal conditions (17.2 ± 0.9°C), C. perfringens spores log reductions of up to 2.0 or 98.9 ± 0.4% were observed using a combination of polyelectrolyte and slaked lime. However, when experiments were conducted at high temperatures (20.3 ± 0.1°C), C. perfringens spore log reductions of infinity or 100% were observed with the polyelectrolyte. At increased turbidity, C. perfringens spores log reductions of up to 2.0 or 99.1 ± 0.1% were observed with the polyelectrolyte. The lowest turbidity reduction of up to 24.1 ± 0.8% was observed when slaked lime and activated sodium silicate were used at 20.3 ± 0.1°C. The highest turbidity reduction of up to 99.0 ± 0.1% was observed using a combination of polyelectrolyte and slaked lime for high-turbidity water. This study showed that water purification steps could remove up to 100% of C. perfringens spores when a polyelectrolyte or a combination of polyelectrolyte and slaked lime are used under varying conditions. Therefore, this study recommends using a polyelectrolyte or a combination of a polyelectrolyte and slaked lime for water treatment under specified conditions. A polyelectrolyte and slaked lime combination is recommended for high-turbidity water.

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