Faculty of Engineering & Technology

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A testing and verification protocol for a modern bus bar transfer scheme based on the transfer philosophy and theory of voltage decay
(Vaal University of Technology, 2020-04) Van Rooyen, Johannes Petrus; Le Roux, B. J.; Walker, J. J., Prof.
This dissertation focuses on the creation of a testing protocol or procedure for verification of a modern motor bus bar transfer scheme. There are four main transfer methods addressed during this study and with it the main parameters affecting the operation of such a system. The complete construction of the simulation and training panel is described and with it the outline of the testing protocol for using this panel is given. Some simulation work was done to calculate the correct verification times based on mathematical formulation to lay out the criteria for verification of transfer methods when testing with a modern three phase test bench. On completion of result documentation, a detailed analysis is conducted to generate the testing protocol which is also discussed in detail. From the test results obtained it was possible to accurately test the 4 common transfer methods using the theory of voltage decay as a guideline, but the protocol will have to be adjusted to suit individual transfer system needs as each transfer system may be unique in design and function although the basic principles outlined during this report will stay the same. Possible steps to take when adjusting the protocol were addressed and some future work for testing motor bus bar transfer schemes was suggested.
Activation of the carbonaceous material from the pyrolysis of waste tires for wastewater treatment.
(Vaal University of Technology, 2017-07) Malise, Lucky; Seodigeng, T., Dr.; Rutto, H. L., Dr.
The generation of waste tires is one of the most serious environmental problems in the modern world due to the increased use of auto mobiles all over the world. Currently there is a problem with the disposal of waste tires generated since there are strict regulations concerning their disposal through landfill sites. Therefore, there is a need to find ways of disposing these waste tires which pose serious health and environmental problem. The pyrolysis of the waste tires has been recognised as the most promising method to dispose the waste tires because it can reduce the weight of the waste tires to 10% of its original weight and produce products such as pyrolysis oil, pyrolysis char, and pyrolysis char. These products can be further processed to produce value added products. The char produced from the pyrolysis of waste tires can be further activated to produce activated carbon. This study is based on the chemical activation of waste tire pyrolysis char to produce activated carbon for the removal of lead ions from aqueous solution. This was done by impregnating the waste tire pyrolysis char with Potassium hydroxide and activating it inside a tube furnace under inert conditions to produce waste tire activated carbon. Adsorbent characterisation techniques (SEM, FTIR, TGA, XRF, XRD, BET, and Proximate analysis) were performed on the waste tire pyrolysis char and the activated carbon produced to make a comparison between the two samples. The results showed that the waste tire activated carbon produced has better physical and chemical properties compared to the raw waste tire pyrolysis char. Adsorption results revealed that waste tire activated carbon achieves higher removal percentages of lead ions from aqueous solution compared to waste tire pyrolysis char. The results also showed the effect of various process variables on the adsorption process. Adsorption isotherms, kinetics, and thermodynamics were also studied. The adsorption of lead ions agreed with the Freundlich isotherm model for both the waste tire pyrolysis char and waste tire activated carbon. In terms of adsorption kinetics, the experimental data provided best fits for the pseudo-first order kinetic model for both the waste tire pyrolysis char and the waste tire activated carbon. The adsorption thermodynamics study revealed that the process is an exothermic process and spontaneous in nature. Response surface methodology was used to determine the combined effect of process variables on the adsorption of lead ions onto waste tire activated carbon and to optimise the process using numerical optimisation. The optimum conditions were found to be adsorbent dosage = 1g/100ml, pH = 7, contact time = 115.2 min, initial meta concentration = 100 mg/l, and temperature = 25°C to achieve a maximum adsorption capacity of 93.176 mg/l.
The adsorption of Cu(II) ions by polyaniline grafted chitosan beads.
(Vaal University of Technology, 2013-11-06) Igberase, Ephraim; Ofomaja, A., Dr; Osifo, P.O., Dr
This work investigates the possible use of chitosan beads and polyaniline grafted chitosan beads (PGCB) for the adsorption of copper ions from copper contaminated water. For this purpose chitosan flakes were converted to chitosan beads. However, a variable from a number of reaction variables (aniline concentration, chitosan concentration, temperature, acid concentration, reaction time and initiator concentration) was varied while others was kept constant, in an attempt to determine the best conditions for grafting of polyaniline onto chitosan beads. Percentage (%) grafting and % efficiency were key parameters used to determine such conditions. The chitosan beads and PGCB were characterized using physical techniques such as Fourier transformed infra red (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The beads were used as an adsorbent for copper ions removal. The effect of pH on the removal rate of copper (II) by PGCB was investigated on by varying the pH values from pH 3 to 8 at an initial concentration of 40 mg/l. The effect of contact time, initial concentration and temperature was also investigated. The Langmuir and Freundlich model were used to describe adsorption isotherms for chitosan beads and PGCB, with correlation coefficient (R2) as the determining factor of best fit model. The thermodynamics of adsorption of copper (II) onto PGCB was described by parameters such as standard Gibb’s free energy change (ΔGo), standard enthalpy change (ΔHo), and standard entropy change (ΔSo) while the pseudo first-order and pseudo second-order kinetic model was used to describe kinetic data for the PGCB, with R2 and chi- square test (  2) as the determinant factor of best fit model. From the desorption studies, the effect of eluants (HCl and HNO3) and contact time on percentage desorption of PGCB loaded copper (II) ion was investigated upon. In determining the reusability of the PGCB loaded copper (II) ion, three cycles of adsorption/desorption studies was carried out. The results obtained from determining the best conditions for grafting polyaniline onto chitosan beads revealed the following grafting conditions; [Aniline] 0.1 g/l, [temperature] 35oC, [chitosan] 0.45 g/l, [HCl] 0.4 g/l, [(NH4)2S2O8] 0.35 g/l, and [time] 1 h. These conditions were applied in the grafting of polyaniline onto chitosan beads. FTIR analysis showed increase intensity in the grafted beads which provided evidence of grafting, XRD measurement showed a decrease in crystallinity in the PGCB as against the partial crystalline nature of chitosan. In SEM analysis, evidence of grafting was revealed by the closed gap between the polysaccharide particles in the PGCB. From the investigation carried out on the effect of pH on the percentage removal of Cu(II) ions by PGCB, the optimal pH value was found to be pH 5 with a percentage removal of 100% and this value was used for all adsorption experiment. Also from the investigation performed on the effect of contact time and initial concentration, it was observed that there was a sharp increase in the amount of Cu(II) ions adsorbed by PGCB up until contact time of 30 min and thereafter, it increases gradually. From the experiment carried out on the effect of temperature on adsorption capacity, there was an increase in adsorption capacity with increase in temperature. Moreover, at temperatures of 25oC, 35 oC and 45oC the Langmuir model gave the best fit for the chitosan beads having R2 values that are equal and greater than 0.942 in contrast to Freundlich having R2 values that is equal and greater than 0.932. The maximum adsorption capacity (Qm) from Langmuir model at these temperatures were 30.3 mg/g, 47.6 mg/g and 52.6 mg/g respectively. Also, the Langmuir model gave the best fit for the PGCB having R2 values that are equal and greater than 0.956 in contrast to Freundlich model with R2 values that is equal and greater than 0.935. The Qm from Langmuir model at these temperatures were 80.3 mg/g, 90.9 mg/g and 100 mg/g respectively. The values of Qm for PGCB appears to be significantly higher when compared to that of chitosan beads and this makes PGCB a better adsorbent than chitosan beads. From the thermodynamic studies carried out on PGCB, the values of ΔGo were negative and this denotes that the adsorption of copper ions onto PGCB is favorable and spontaneous, the positive value of ΔHo shows the adsorption process is endothermic and the positive value of ΔSo illustrate increased randomness at the solid-liquid interface during the adsorption process. Also, from the kinetic studies carried out on the PGCB, the pseudo second-order kinetic model best described the kinetic data having R2 values that are equal and greater than 0.994 in contrast to the pseudo first-order kinetic model with R2 values that is equal and greater than 0.913. The  2 values for the pseudo first-order and pseudo second-order kinetic model were similar; however, there was a large difference for qe between the calculated (qeCal) values of the first-order kinetic model and experimental (qeExp) values. In the case of the pseudo second-order model, the calculated qe values agree very well with the experimental data. Desorption of the metal ions from PGCB was efficient. 0.5 M HCl was successfully used in desorbing the beads loaded with copper ions and a percentage desorption of 97.1% was achieved at contact time of 180 min. PGCB were successfully re-used for adsorption/desorption studies were a Qm of 83.3 mg/g, 83.3 mg/g and 76.9 mg/g was achieved in the first, second and third cycle respectively.
Advanced modelling of porous screens in aerodynamic diffusers using variable resistance factors
(2014-12) Janse van Rensburg, Jacobus Johannes; Van Staden, M. P.; Jacobs, G. G.
Strict emission legislation has forced industry in general to seriously consider the negative impact it has on the environment, specifically concerning emissions from burning fossil fuel into the atmosphere. In cases where emission levels exceed the allowable limit, companies are forced to operate at lower operating conditions and these load losses can result in a significant loss of revenue. This has forced companies to improve their ash filtering capabilities by optimising electrostatic precipitation systems. One of the main factors impacting on the efficiency of such a system is the distribution of the flow across the collection plates. The design of the inlet diffuser plays a major role in the ultimate distribution of the flow through the precipitator. Porous screens are positioned in the diffuser in order to distribute the flow across the total flow area with the aim to achieve a uniform distribution of the flow. CFD is widely used in industry to simulate the flow through precipitators in order to optimise the flow distribution and thus increase the efficiency of the system. It was found however that the current methods used to simulate these screens in CFD models were not well researched and employed fixed resistance values that could not reliably compensate for changes in the resistance coefficient due to a change in the angle of incidence. This study investigates advanced numerical methods for the simulation of porous screens in applications where the angle of incidence changes continuously across the face of the screen. New methods are introduced where the resistance of the screen is calculated as a function of the changing angle of incidence. The methods currently used are also investigated and compared with results from the new methods. Extensive experimental work was required to supply empirical data for the validation of the numerical methods that are proposed. For this reason, the first part of this study focused on the design construction and commissioning of a low speed wind tunnel. Results are presented and discussed for flow profiles through wide-angle diffusers at different angles and also for a number of different screens positioned in the centre of the diffuser. This study also investigates the sensitivity of a CFD simulation code to factors such as numerical discretisation schemes, turbulence models and solution relaxation specifically for wide-angle diffusers. These factors were tested for diffusers at different angles and included tests on open diffusers and also with screens positioned inside the diffuser. It was concluded that the current methods used are not adequate to capture the true flow profiles for a range of different screen geometries. Although the proposed models did improve on the limitations of the current methods, it was found that the applicability of these models is still limited and that further research would be required to develop numerical methods that are valid for a wide range of applications.
An investigation of the damping response and structural strength of a fibreglass and rubber particle composite sleeper
(Vaal University of Technology, 2022-09-12) Mbatha, Abednigo Jabu; Maube, O., Dr.; Nkomo, N. Z., Dr.; Alugongo, Prof.
A railway sleeper is a supporting and dampening beam placed underneath the railway track and can be made of different materials. There are four main types of railroad sleeper materials: timber or wooden, steel, concrete and composite material. The railway structural material often suffers from aggressive loading and vibration in the locomotive industry, and the sleepers' current durability and their vibration properties are not sufficiently resilient to vibration. There is a need for a structural material that can withstand significantly higher static and dynamic loads as trains become heavier and faster. Tyre disposal is a global challenge to the environment, with approximately 1.5 billion tyre waste generated annually. Tyres are non-biodegradable, making their disposal extremely difficult.This study seeks to find a way to recycle the waste tyres in an environmentally friendly manner in accordance with Sustainable Development Goal 11, which focuses on sustainable cities and communities. The study aimed to optimize a hybrid composite sleeper using waste tyres ground into particles, fibreglass reinforcement and polyester resin to enhance the composites' structural strength while increasing the composite sleeper's damping. The specific objectictives were to characterized rubber particles of waste tyres and fabricate a composite railroad sleeper material using waste rubber particles, glass fibre, and polyester resin..Thereafter , evaluate the mechanical properties of the composite sleeper under loading conditions and damped vibration properties .Lastly , determine the optimal composite sleeper . The rubber particles were characterized through sieving, moisture analysis and SEM. Thereafter, the composite was fabricated following the full experimental design. After that composite was fabricated using the hand lay-up method where the rubber volume fraction of 5, 10, 15 and 20% were varied, and fibreglass volume fractions of 5, 6, 7 and 8 % were obtained. The UTM (universal testing machine) was used to carry out mechanical tests, which included tensile strength, compression strength and flexural strength. Then Leeb hardness was carried out, and the damping properties of composites were determined using a shaker table. Minitab software was used for the optimisation of the composite mix The ANOVA test showed the model's accuracy in predicting tensile strength, compression strength, flexural strength, and vibrational damping, as shown by R2 values of 60.69%, 86.60%, 60.05% and 81.41 %, respectively. However, the model was not reliable for hardness which had an R2 value of 37.87%. The optimisation model indicated that rubber particles of size 150 μm with 7.48% volume fraction of rubber particles and fibreglass volume fraction of 8% are optimum. The corresponding mechanical properties responses for the optimum are tensile strength of 13.3851 MPa, the compression strength of 36.0272 MPa, the flexural strength of 36.5865 MPa and Leeb hardness of 647.7510. The damping properties of composite gave a value of 0.1416. Thereafter, optimum results were validated experimentally, and the model was shown to represent the data accurately. The fabricated composite could help to absorb aggressive forces caused by heavily loaded trains. At the same time, maintain the composite's mechanical strength and eliminate pollution caused by tyres in our environment. Further investigation is required into the impact of using a variety of rubber particle sizes 75 m on the vibrational damping and mechanical characteristics of the composite railway sleeper. Studying the impacts of various synthetic and natural rubber kinds on composite characteristics is also necessary.
Anaerobic co-digestion of abattoir and textile industry wastewater in a UASB reactor
(2015-04) Ondari, James Maati; Ndege, Maurice S.; Aoyi, Ochieng
Textile industry effluents are carcinogenic and highly recalcitrant hence difficult to degrade especially through biological methods. Abattoir effluents are classified under high-strength wastewaters because of their characteristic high organic load hence highly biodegradable. Anaerobic co-digestion is the concept of degrading two effluent streams with complementary characteristics in order to improve the substrate removal rate. The feasibility of co-digesting abattoir and textile wastewater in a UASB reactor was evaluated at mesophilic and ambient temperature conditions. Preliminary experiments were conducted in 500 ml batch reactors to evaluate the optimum abattoir to textile synthetic wastewater ratio. The effect of COD, TVFA, alkalinity and pH on biogas yield was examined at both ambient and mesophilic temperatures. Anaerobic co-digestion of abattoir to textile wastewater in the ratio determined in the batch process was carried out in a 3 L UASB reactor by a continuous process. The continuous biodegradation process was executed at three different HRTs (22, 18 and 14 hrs) over a 60 day operation period. UASB reactor efficiency was achieved at organic loads ranging from 3.0 – 10.8 gCOD L-1 day-1. Continuous mode experiments were carried out at influent flow rates which corresponded to HRTs ranging between 1 to 8 days in order to evaluate the steady state operating parameters for the co-digestion process. The abattoir to textile effluent ratio was found to be 60:40 respectively. The COD, TVFA, alkalinity and pH and biogas yield followed a similar pattern over time at both mesophilic and ambient temperature conditions. Experimental data adequately fit the Grau first order kinetic model and average COD removal efficiencies of 85% and BOD5 of around 96% were achieved. The average biogas yield remained essentially constant, around 0.19 L/g CODremoved. The co-digested mixture was found to be biodegradable judging from the BOD:COD ratio of 0.53. TCOD removal efficiency decreased from 93% to 16% as HRT decreased from 8 days to 1 day. The kinetics of a UASB reactor co-digesting the mixture of synthetic abattoir and textile wastewater was evaluated in this study using Grau second order multicomponent substrate removal kinetic model. The Grau second order kinetic model, whose kinetic coefficient (ks) was 0.389, was found to be suitable for predicting the performance of a lab-scale UASB reactor.
Analysis of the environmental impact on the design of fuel cells
(2013-08-22) Sibiya, Petros Mandla; Pienaar, H. C. v Z
The air-breathing Direct Methanol Fuel Cell (DMFC) and Zinc Air Fuel Cell (ZAFC)were experimentally studied in a climate chamber in order to investigate the impact of climatic environmental parameters such as varying temperature and relative humidity conditions on their performance. The experimental results presented in the form of polarization curves and discharge characteristic curves indicated that these parameters have a significant effect on the performance of these fuel cells. The results showed that temperature levels below 0ºc are not suitable for the operation of these fuel cells. Instead, it was found that air-breathing DMFC is favored by high temperature conditions while both positive and negative effects were noticed for the air-breathing ZAFC. The results of the varying humidity conditions showed a negative impact on the air-breathing DMFC at a lower temperature level but a performance increase was noticed at a higher temperature level. For air-breathing ZAFC, the effect of humidity on the performance was also found to be influence by the operating temperature. Furthermore, common atmospheric air pollutants such as N20, S02, CO and N02 were experimentally investigated on the air-breathing DMFC and ZAFC. At the concentration of 20 ppm, these air contaminants showed to have a negative effect on the performance of both air-breathing DMFC and ZAFC. For both air-breathing DMFC and ZAFC, performance degradations were found to be irreversible. It is therefore evident from this research that the performance of the air-breathing fuel cell will be affected in an application situated in a highly air-polluted area such as Vaal Triangle or Southern Durban. It is recommended the air-breathing fuel cell design include air filters to counter the day-to-day variations in concentration of air pollutants.
Application of integrated water resources management in computer simulation of River Basin's status - case study of River Rwizi
(2012-03-28) Atim, Janet; Ngirana-Katashaya, G.; Ndambuki, J. M.
During the last few years, concern has been growing among many stakeholders all over the world about declining levels of surface water bodies accompanied by reduced water availability predominantly due to ever increasing demand and misuse. Furthermore, overexploitation of environmental resources and haphazard dumping of waste has made the little water remaining to be so contaminated that a dedicated rehabilitation/remediation of the environment is the only proactive way forward. River Rwizi Catchment is an environment in the focus of this statement. The overall objective of this research was to plan, restore and rationally allocate the water resources in any river basin with similar attributes to the study area. In this research, Integrated Water Resources Management (IWRM) methodology was applied through Watershed/Basin Simulation Models for general river basins. The model chosen and used after subjection to several criteria was DHI Model, MIKE BASIN 2009 Version. It was then appropriately developed through calibration on data from the study catchment, input data formatting and its adaptation to the catchment characteristics. The methodology involved using spatio-temporal demographic and hydrometeorological data. It was established that the model can be used to predict the impact of projects on the already existing enviro-hydrological system while assigning priority to water users and usage as would be deemed necessary, which is a significant procedure in IWRM-based environmental rehabilitation/remediation. The setback was that the available records from the various offices visited had a lot of data gaps that would affect the degree of accuracy of the output. These gaps were appropriately infilled and gave an overall output that was adequate for inferences made therefrom. Several scenarios tested included; use and abstraction for the present river situation, the effect of wet/dry seasons on the resultant water available for use, and proposed projects being constructed on and along the river. Results indicated that the river had insufficient flow to sustain both the current and proposed water users. It was concluded that irrespective of over exploitation, lack of adequate rainfall was not a reason for the low discharge but rather the loss of rainwater as evaporation, storage in swamps/wetlands, and a considerable amount of water recharging groundwater aquifers. Thus, the proposed remedy is to increase the exploitation of the groundwater resource in the area and reduce the number of direct river water users, improve farming methods and conjunctive use of groundwater and surface water - the latter as a dam on River Rwizi. The advantage of the dam is that the water usage can be controlled as necessary in contrast to unregulated direct abstraction, thus reducing the risk of subsequent over-exploitation.
Application of neural network techniques to predict the heavy metals in acid mine drainage from South African mines
(Vaal University of Technology, 2022-04) Maliehe, Andani Valentia; Osifo, P., Prof.; Matjie, H., Dr.; Tshilenge, John Kabuba, Prof.
Acid mine drainage (AMD) refers to acidic water generated during mining activities and is characterised by a low pH, high salt content, and the presence of heavy metals. To treat water sources contaminated with AMD, sampling and laboratory analysis will have to be done for each water source to determine the concentrations of heavy metals. This process is time-consuming, high in cost and may involve human error or negligence. The application of neural network (NN) techniques to predict the heavy metals in AMD from South African mines has been presented. Four specific objectives were pursued in this dissertation. The first one was to identify AMD and analyse for heavy metals in the AMD. Heavy metals that were identified and found to be in high concentrations in the AMD sample from Sibanye Western Basin AMD Treatment Plant are Zn, Fe, Mn, Si, and Ni. The other objectives of the study were to determine the input, output, and hidden layers of the NN structure (application of NN); (2) to find the appropriate algorithm to train the NN, and to compare the NN results (outputs) with the measured concentrations of major heavy metals sampled (targets). The Backpropagation Neural Network (BPNN) model had three layers which included the input layer (pH, SO42−, and TDS), the hidden layer (five neurons) with a tangent sigmoid transfer function (tansig) and the output layer (Cu, Fe, Mn, and Zn) with linear transfer function (purelin). The predictions for heavy metals (Zn, Fe, Mn, Si, and Ni) using the NN method focusing on a BP forward pass (feed-forward backpropagation NN) with ten different algorithms were presented and compared with the measured data. The mean square error (MSE) value was calculated for ten algorithms and compared to identify the one that is most appropriate for the prediction process and the model by having the lowest value. It was determined that the Levenberg-Marquardt back-propagation (trainlm) algorithm resulted in the best fitting during training because it resulted in an MSE value of 0.00041, meaning the error was very low when this algorithm was used.
Application of nonwoven microfiltration membrane on activated sludge final effluent: improving wastewater quality for re-use
(Vaal University of Technology, 2022-04) Masala, Murendeni Shonisani; Topkin, James; Tshilenge, J. Kabuba, Prof.
Water scarcity is one of the biggest problems that South Africa is facing currently, as a results it limits economic and social development. The application of membrane technology in wastewater treatment for re-use is one of the alternatives to reduce the demand of water in domestic, agricultural and industrial sectors. The primary aim of this study was to improve effluent wastewater quality prior to disinfection for re-use. This was done by diverting biological nutrient removal (BNR) clarifier effluent to a pilot nonwoven membrane filtration unit. The physical barrier provided by this unit, together with the effect of aeration within this system, provided particulate, physicochemical, and microbial removal. Monitoring of water quality was attained from the BNR clarifier effluent, and the nonwoven membrane permeate. Water quality trends against the standards were analysed for compliance with a water use license (WUL), and the removal efficiency for the permeate was also determined. The Single Factor Pollution Index (Pi) was used to determine the extent of pollution in the BNR clarifier effluent and the permeate, while the Water Quality Index (WQI) was utilised to determine the suitability of water derived from the BNR clarifier effluent and the permeate for re-use. Water Use Licence standards were utilised to determine the Water Quality Index of the BNR clarifier effluent and the permeate. Results for the BNR clarifier effluent showed that the physicochemical water quality parameters comply with the limits however, electrical conductivity (EC) and microbial water quality Escherichia coli (E. coli) were exceeded. Permeate results indicated that physicochemical and microbial parameters were compliant with the limits of the WUL. E. coli reduction was the highest with a removal efficiency of 90%, followed by chemical oxygen demand (COD) at 25%, NH4N at 22%, NO3 at 12.6%, PO4 at 7.8%, suspended solids (SS) at 6.3%, and the lowest was EC at 5.2%. The Single Factor Pollution Index has revealed that the BNR clarifier effluent water quality is medium polluted and the permeate water quality is slightly polluted. The WQI results for the BNR clarifier effluent showed good water quality and the water can be re-used for domestic, irrigation, and industrial purposes, while permeate WQI results indicated excellent water quality and the water can be re-used for drinking, domestic, irrigation, and industrial purposes. Outstanding permeate water quality improvement was observed on E. coli counts improving from 4974.48 counts/L to 294.33 counts/L. The standard of E. coli according to the WUL at Waterval WCW is 500 counts/L. The results indicate that nonwoven membrane filtration can improve microbial contamination and decrease the demand of chlorine for disinfection of wastewater final effluent. The nonwoven membrane filtration can decrease the water scarcity gap in South Africa for direct water reclamation by improving effluent wastewater.
An application of reverse osmosis process on effluent treatment for the rubber industry
(2009-05) Ralengole, Galebone; Van der Merwe, H.; Modise, S. J.
The methods used to remove potassium sulphate (K2S04) and other impurities contained within Karbochem finishing plant effluent were investigated. Reverse osmosis was explored for this application. The study was conducted in two steps. The first step focuses mainly on the effluent treatment using BW30 flatsheet as well as BW30-2540 spiral-wound reverse osmosis membranes for the rejection of potassium and sulphate ions. The membranes were supplied by Filmtec. The second step reveals the possible use of potassium sulphate obtained from the brine stream in the fertiliser and fertigation industry by a literature search. Reverse osmosis study was conducted on a laboratory scale unit using flat sheet membranes and also on a pilot plant scale using spiral wound membrane modules. The tests were conducted at a feed pressure of 20 bar(g) with the membrane rejections being 98% and 99.1% on flat sheet membrane, and 96.9% and 99.4% on spiral wound membrane for potassium and sulphates respectively. The results show that both membranes have completely desalinated. Significant reduction in the concentrations of all problematic quality parameters, especially of potassium and the sulphate ions was noted. Granular activated carbon (GAC) bed treatment was recommended for pretreatment of the effluent prior to exposure of the membrane to avoid organic fouling of the membrane. GAC treatment was tested to illustrate its effectiveness to adsorb the COD's.
Biocompatibility evaluation of sintered biomedical Ti-24Nb-4Zr-8Sn (Ti2448) alloy produced using spark plasma sintering (SPS).
(Vaal University of Technology, 2018) Madonsela, Jerman S.; Yamamoto, Akiko, Dr.; Machaka, Ronald, Dr.; Shongwe, Brendon, Dr.; Matizamhuka, Wallace R., Dr.
Solid titanium (Ti), Ti-6Al-4V (wt.%), and Ti-24Nb-4Zr-8Sn (wt.%) materials were fabricated from powders using spark plasma sintering (SPS). The starting materials comprised of elemental powders of ASTM Grade 4 titanium (Ti), aluminium (Al), vanadium (V), niobium (Nb), zirconium (Zr), and tin (Sn). The powders were initially characterised and milled prior to sintering. The micronpowders were milled in an attempt to produce materials with nanostructured grains and as a result improved hardness and wear resistance. The produced solid Ti-24Nb-4Zr-8Sn alloy was compared to solid titanium (Ti) and Ti-6Al-4V (Ti64) on the basis of density, microstructure, hardness, corrosion, and biocompatibility. Relative densities above 99.0% were achieved for all three systems. CP-Ti and Ti64 had both 100% relative density, and Ti2448 showed a slightly lower density of 99.8%. Corrosion results showed that all three materials exhibited good corrosion resistance due to the formation of a protective passive film. In 0.9% NaCl Ti2448 had the highest current density (9.05 nA/cm2), implying that its corrosion resistance is relatively poor in comparison to Ti (6.41 nA/cm2) and Ti64 (5.43 nA/cm2), respectively. The same behavior was observed in Hank's solution. In cell culture medium, Ti2448 showed better corrosion resistance with the lowest current density of 2.96 nA/cm2 compared to 4.86 nA/cm2 and 5.62 nA/cm2 of Ti and Ti64 respectively. However, the current densities observed are quite low and insignificant that they lie within acceptable ranges for Ti2448 to be qualified as a biomaterial. Cell proliferation test was performed using murine osteoblastic cells, MC3T3-E1 at two cell densities; 400 and 4000 cells/mL for 7 days incubation. Pure titanium showed better cell attachment and proliferation under both conditions suggesting that the presence of other oxide layers influence cell proliferation. No significant difference in cell proliferation was observed between Ti64 and Ti2448.
Biodiesel production and evaluation of heterogeneous catalyst using South African oil producing trees
(Vaal University of Technology, 2014-01) Modiba, Edward Magoma; Osifo, Peter, Prof.; Rutto, Hillary, Dr.
This study presents the use of sodium methoxide as a homogeneous catalyst and impregnated Perlite (potassium hydroxide/perlite) as heterogeneous catalyst for production of biodiesel using Baobab and Marula oil respectively. One factor at a time experimental design was used to study the effect of temperature, time, amount of catalyst and methanol to oil ratio on the transesterification of baobab oil using sodium methoxide as a catalyst. Response surface methodology was used to study the effect of temperature, time, amount of catalyst and methanol to oil ratio on the transesterification of marula oil using perlite as a catalyst. Biodiesel yield produced using sodium methoxide and baobab oil was 96% at 1 hr reaction time, 30 wt.% methanol to oil ratio, 1 gram of catalyst and 60°C reaction conditions. Biodiesel yield produced using perlite and marula oil was 91.38% at 3.55 hr reaction time, 29.86 wt.% methanol to oil ratio, 3.46 grams of catalyst and 70.41°C reaction conditions. Perlite catalyst was reusable for transesterification of marula oil while sodium methoxide was not reusable for transesterification of baobab oil. Baobab and Marula biodiesel fuel properties are comparable to American Society for Testing Materials standard (ASTM).
Biodiesel production using cellulose-supported calcium hydroxide heterogeneous catalyst. phosphate rock as a catalyst precursor
(Vaal University of Technology, 2022-06) Kiprono, Janet Jematia; Rutto, H. L., Prof.
Due to rising gasoline prices and growing worldwide worries about climate change and environmental pollution, the need for a clean, environmentally friendly fuel such as biodiesel has recently gained traction. This has demanded greater study into more efficient techniques to boost biodiesel production. The current study focuses on making and improving the efficiency of calcium hydroxide heterogeneous catalyst to be used in biodiesel manufacturing from waste cooking oil. Phosphate rock, a primary mineral mined in South Africa, containing the compound calcium carbonate in higher quantities, was used to prepare calcium nitrate, a useful compound in nature. Calcium nitrate was then reacted with cellulose nanoparticles and sodium hydroxide solution to obtain cellulose-supported calcium hydroxide catalyst through the co-precipitation method. Characterization techniques such as SEM and FTIR were used to confirm calcium hydroxide loading on the cellulose support material. The efficiency of the synthesized catalyst in the transesterification process was studied by varying the alcohol to oil ratio, amount of catalyst, the reaction temperature, reaction time, and the reusability cycles of the catalyst through one factor at a time method and response surface methodology. Artificial neuron network was later used in the prediction of biodiesel yield. High regression coefficient values were obtained, indicating the efficiency of artificial neuron network tool in the prediction of biodiesel. Calcined phosphate rock is also tested for use as a heterogeneous catalyst for biodiesel production. This is based on the fact that when calcium carbonate in the rock is subjected to extremely high temperatures, the carbonates undergo decomposition releasing carbon iv oxide gas thus forming calcium oxide. This oxide also proved to be an active catalyst for transesterification. The efficiency of this catalyst was also tested through one factor at a time and response surface methodology. Both cases obtained a higher biodiesel yield.
Biogas production from solid food waste and its use for electricity production
(Vaal University of Technology, 2021-10-15) Khune, Selebogo Mervyn; Ochieng, Aoyi, Prof.; Otieno, Benton, Dr.; Osifo, Peter, Prof.
An enormous amount of food waste (FW) is generated worldwide. Most of this waste is discarded in landfills, where it undergoes uncontrolled anaerobic digestion (AD) process, which emits excessive amounts of greenhouse gases, (methane and carbon dioxide), thereby contributing to global warming. A controlled AD of FW is key for organic waste management with a positive impact on the environment and economy. In South Africa (SA) there is little uptake of biogas technology for FW management due to little research on biogas potential at small to large scale. Furthermore, there is an over reliance on foreign data, which leads to misfit parameters to local raw materials; consequently, producing biogas of low quality and quantity with low degradation of waste. Biogas with poor quality reduces the efficiency of biogas conversion to energy and the low production rate makes the system less feasible. Considering the challenges faced with FW management and the little uptake of the AD technology in SA, this study aimed to treat FW through AD and convert the biogas produced to electricity. A complete-mix biogas pilot plant (VUT-1000C) was designed, constructed and commissioned. The materials used for constructing the pilot plant were sourced locally to prove the applicability of the AD technology in SA. The biodigester was operated at mesophilic temperature, 37 oC, aided by a solar system. A stand-alone 1 m3 plug-flow ambient biodigester (STH-1000A) was operated semi-continuously as well as a control. Cow dung (CD) was used to inoculate the biodigesters, which were then operated semi-continuously at their optimum organic loading rate (OLR). The STH-1000A digester was operated at 0.446 kgVS/m3/day OLR, according to the manufacturer’s specification, while for VUT-1000C, the OLR was determined. The highest biogas and methane yields obtained were 582 and 332 L/kgVS/m3, respectively, at the determined optimal OLR of 1.5 kgVS/m3/day for the VUT-1000C digester this was supported by the modified Gompertz model with an R2 value of 0.9836. VUT-1000C produced 1200 L/day while STH-1000A produced 150 L/day. VUT-1000C proved to be a more effective biodigester than STH-1000A owing to the digester design and operation at mesophilic conditions. The key design findings are higher reactor working volume and high digester temperature. From the 1000 L of biogas produced from VUT-1000C, 1.8 kW of electricity was generated, which is equivalent to powering 300 6W light bulbs for 1 hour. The energy balance of the pilot plant showed that only 10 percent of the energy output was required to operate the plant. These results show that SA has a 475 GWh energy potential based on the current FW figures. Furthermore, the study has shown that biogas technology is readily available for South Africans and that the designed biogas plant was very efficient in FW-to-energy conversion.
Characterisation and flowability of titanium grade 5 alloy powders
(Vaal University of Technology, 2013-09) Nziu, P. K.; Mendonidis, P., Prof.; Labuschagne, D., Dr.; Masu, L. M., Prof.
Flowability is one of the essential physical characteristics considered during the use of any powder in a manufacturing process. However, very little research on flowability of titanium powder has been conducted. To this end, this study dealt with global market survey of titanium powder manufacturers and suppliers. In addition, the effects of various physical parameters such particle size, shape, chemical analysis, density and soundness on flowability of titanium grade 5 alloys powder in additive manufacturing application were investigated. Twelve powder samples of titanium alloy grade 5 (Ti6Al4V) were sourced, tested and analyzed using various methods. The choice of the characterization method used depended on its accuracy, equipment availability and application. Particle size and shape were characterized using laser diffraction and scanning electron microscope techniques, respectively. Quantitative and crystallographic analyses were done to determine the chemical composition as well as alpha and beta phases. Shear cell and dynamic tests were performed to determine bulk density, stability, flow energy and flowability where as particle density was performed by a pcynometer. Research on potential manufacturers was conducted using questionnaires. It was established that high cost of titanium powder is partly driven by titanium powder firms that are not willing to disclose information about the product. It was observed that powder flowability is affected by particle size, shape, chemical composition, density and soundness. The particle density was found to be a function of chemical composition that is the alloying elements and impurities present in the powder. It was noted that bulk density, porosity, cohesion and agglomeration were affected by particle size. Soundness of the powder was also found to improve with sphericity of the particles. Among the physical parameters studied, particle size had the highest effect on powder flowability. The highest flowability was noted at particle size of 41 μm.
Characterisation of Ti6Al4V lattice structures produced by direct metal laser sintering for possible biomedical applications
(Vaal University of Technology, 2022) Raselabe, Kabelo Matome; Baloyi, N.; Mendonidis, P., Prof.
The use of Ti6Al4V lattice structures as a new detergent to the stress shielding phenomenon caused during implantation has been growing. The stress shielding phenomenon is caused by the inhomogeneous transfer of load between the implant and the surrounding bone. This is mainly due to the implants containing modulus (110 GPa) being higher than that of the surrounding bone (2-20 GPa). Due to high cost and tedious process involved in manufacturing lattice structures using conventional technique, as a result of the complexity in lattice structure’s geometry, a process known as additive Manufacturing is highly recommended. Additive manufacturing processes like the use of Direct metal laser sintering (DMLS) process to create three-dimensional (3D) parts, layer by layer using computer-aided design (CAD) allows to freely build parts with geometric complexities In this dissertation, the DMLS process was used to manufacture Ti6Al4V lattice structures with Young’s modulus like that of cortical bone or within the range of 2-20 GPa. These structures were manufactured at different build orientations (Horizontal and Vertical) and strut sizes (1 and 1.5 mm). The Ti6Al4V lattice structures post-manufacturing were subjected to stress-relieving (SR) post-treatment of 650 ºC under argon atmosphere for 2 hours and 950 ºC under vacuum (VHT) atmosphere for 2 hours. The purpose of stress-relieving is to remove the residual stresses caused by the thermal gradients during manufacturing. While the vacuum heat treatment is for promoting ductility. Under these conditions (stress relieving and vacuum heat-treatment) the lattice structures were then analysed for microstructure, hardness, compression, and corrosion. For stress relieved lattice structures, DMLS's Ti6Al4V SR lattice structures possessed α' martensite and prior β grains along the build orientation. When comparing the mechanical properties of vertical and horizontal lattices, it was discovered that vertical lattice has higher hardness, compressive strength (324.1 MPa), and ductility (12%), as well as a lower Young's modulus (1.5 GPa). Vertically built lattices corroded at a faster pace than horizontally built. To change the microstructure and characteristics of Ti6Al4V lattices, vacuum heat treatment at 950 °C was performed on the SR lattices. The microstructure study demonstrated a change of α' to α+β lamellar type structure. Furthermore, the VHT enhanced ductility (18-29%) and demonstrated a Young modulus value of 2.8-3.3 GPa which is within the range for the biomedical area. The corrosion rate of horizontally built lattices was lower than that of vertically built lattices. It was then concluded that, the DMLS Ti6Al4V lattice structures yielded a Young's Modulus within the range necessary for cortical bone replacement. Which in turn mean that the Ti6Al4V lattice is more likely to be accepted in the biomedical area than fully solid/dense DMLS made Ti6Al4V, which ranges from 110 – 120 GPa. Other properties of Ti6Al4V lattice structures demonstrate that VHT lattices have higher hardness than SR lattices and that VHT lattices corrode less than SR lattices. This ultimately led to both 1 and 1,5 mm strut sizes, the Horizontally formed lattice was more corrosion resistant than the Vertically created lattice.
Chitosan modification with cellulose - gelatin to remove heavy oil from wastewater
(Vaal University of Technology, 2022-08-30) Fundji, Wato Nathan; Igberase, Ephraim, Dr.; Tshilenge, John Kabuba, Prof.
In this study, Chitosan was modified with cellulose and gelatin for the removal of Cu2+, Fe2+, and Pb2+ from oily wastewater. Membranes were prepared and characterized using Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X - Ray Diffraction (XRD). Their changes and permeabilities were studied and showed that pH values slightly changed. The effects of pH solution and conductivity were investigated. Adsorption study was performed to remove the heavy metals. The results revealed that the highest % removal of Cu2+ was 96.62 (pH = 7.52 and conductivity = -12 mV), of Fe2+ was 97.95 (pH = 6.30 and conductivity = +68 mV) and of Pb2+ was 98.86 (pH = 10.58 and conductivity = -170 mV) for the 12: 2: 2 ratio and for the other ratio, results were quite similar. To analyse the impacts of experimental factors, experiments were developed using Central Composite Design (CCD) based and the Response Surface Methodology (RSM). R2 values were 0.99, 0.99 and 0.98 correspondingly to the analysis of variances of Cu2+, Fe2+, and Pb2+, respectively while using the 12: 2: 2 ratio but for the other ratio, results were almost the same. In interpreting the experimental data, the quadratic models were significant and appropriate. For all models, the variations between experimental and predicted values of % Removal were insignificant. The resulting 3D response surface graphs allowed for a paired investigation of variable influences upon every response model. This study aimed to develop a new chitosan membrane as a film-forming material with a lower acid content and improved mechanical properties in order to remove heavy oil from wastewater.
Controllability and stability of selectively wettable nanostructured membrane for oil/water separation
(Vaal University of Technology, 2019-12) Sob, Peter Baonhe; Alugongo, A. A., Prof.; Tengen, T. B., Prof.
Presently, the current membrane technologies used in oil/water separation are inefficient with poor controllability and stability during oil/water separation. The has led to the current problem of membrane fouling and degradation during oil/water separation. Several approaches have been used to modify or design a better wettable surface with limited success since the current problem of membrane fouling is persisting. It is, therefore, necessary for scientists, engineers, and researchers to come up with a new membrane technology that will be more efficient with stable wettability and controllability during oil/water separation. Membranes are made up of nanoparticles on their surface, which are both random in nature. Furthermore, the collection of membrane particles to form mesh membranes are made of pores with further ransom spatial distribution. Thus, it was necessary to use the tools of stochastic processes to theoretically characterize these parameters. These parameters affect both internal and external factors as well as characteristics of random membrane particle and pores on wettability like surface tension and surface energy were established in the current project. Design and production of the membrane material according to established relationships was by both low and high-pressure spay jet coating in a controlled laboratory environment, and microscopic characterization performed using SEM. TEM, EDS, statistical analysis, and Image J particle analyzer. The spread, orientation, morphology, spatial distribution, inter-separation distances, surface roughness, surface smoothness, contact angles, surface density of the particle, mean size of the coated nanoparticle on the membrane surface after different coating rounds were analyzed so as to establish conditions for optimal wettability. The testing of produced membranes under the application of external and internal factors was done. A centrifugal pump was used to pump contaminated oil and water mixture through the membrane under a steady flow rate of 10 L/s with a gauge pressure of 180 kPa at room temperature conditions. The membrane materials from different coating rounds were tested for their abilities to produce pure collected water or oil particles in the collected water. The separated water was analyzed using oil and grease analysis US EPA method 1664B with the SPE-DEX 1000 oil and grease system. As revealed theoretically and validated experimentally, it was found that the random natures of nanoparticle size, the spatial distribution of membrane channels, and their morphology have impacts on surface energy-driven separability of oil and water mixture. It was also observed that the scattering of nanoparticles on the membrane surface during coating lowered surface energy, which enhanced oil/water separation. It was also revealed that there is an optimal nanoparticle size, scattering, morphology, and spatial distribution of membrane channels that offer better separation of water from oil. From the microscopy analysis, different microstructures were revealed for glass, ceramics, and sediment during LP and HP coating. The microstructure characterization showed different surface densities of nanoparticles, mean particle sizes, surface roughness or smoothness, and nanoparticles inter-separation distances. It was also revealed that the materials, which were more stable and efficient with more controlled wettability were glass, sediment, and ceramic HP 3rd rounds of coating. Clusters were observed on the membrane surface during HP and LP coating rounds with more clusters observed in LP coating when compared with HP coating. These clusters increased surface energy, which negatively affected oil/water separation. It was concluded that to improved the wettability surface. membrane clusters must be minimized during coating rounds. This thesis contributed new knowledge to existing body knowledge of membrane technology used in oil/water separation in a number of ways by: (1) Designing a new membrane surface with a more controlled, efficient, and stable wettability process during oil/water separation. (2) Applying the logic of surface energy-driven separability, which has not been previously used extensively to study membrane wettability. (3) Establishing a model for the optimal membrane pore sizes that offer optimal membrane wettability during oil/water separation. (4) Establishing a model for optimal nanoparticle coating that offers optimal membrane wettability during oil /water separation. (5) A great attempt was made in characterizing nanoparticle surface densities, spread, particle coating, and nanoparticles intensity on a wettable membrane surface.
Controlling a photovoltaic module's surface temperature to ensure high conversion efficiency
(2015-06) Ozemoya, Augustine; Swart, James; Pienaar, Christo
In order to facilitate sustainable development, it is necessary to further improve and increase the energy efficiency and use of renewable energy and its related technologies. The main limiting factors to the extensive use of photovoltaic (PV) modules include the high initial investment cost and the relatively low conversion efficiency. However, other factors, such as an increase in ambient temperature, exert a considerable negative influence on PV modules, with cell efficiencies decreasing as the cell’s operating temperature increases. Higher PV module surface temperatures mean lower output voltages and subsequent lower output power. Therefore, this dissertation focuses on optimizing the available output power from a PV module by investigating and controlling the effect that the PV module’s surface temperature exerts on the amount of electrical energy produced. A pilot study was conducted by using a PV module set to three different tilt angles with an orientation angle and temperature sensors placed at different points. This was done to determine temperature distribution on the PV module surfaces as well as identify which tilt angle produces the highest PV module surface temperature. The main study was designed to investigate the electrical performance of a PV module with different cooling systems (water and forced air) as against a referenced measurement (no cooling). The cooling systems will be switched on and off at specific time intervals with the help of an electronic timer circuit incorporating a PIC microcontroller. The pilot study was conducted for a 50 week period where the results indicated a direct correlation between temperature rise and voltage decrease. The PV module’s temperature is highest at a tilt angle of 16° during the day and lowest at night time. It further reveals that the PV module’s front and back surface temperature can be distinctly different, with the highest recorded values occurring at the back of the PV module. The main study was conducted for a period of 15 weeks with results indicating that the water cooling system resulted in an average higher output power of 49.6% when compared to the reference system (no cooling system). Recommendations are made that sufficient space should be included between the module frames and mounting structure to reduce high operating temperatures owing to poor air circulation.

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