Chemical Engineering

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Cellulose nanocrystals: plant design for up-scaled production and applications in green construction materials.
(2021) Roopchund, Rishen.; Andrew, Jerome Edward.; Sithole, Bishop Bruce.
Two main problems were addressed in this project. Firstly, upscaling technologies from the laboratory scale to industrial scale is difficult in the absence of pilot scale facilities. This research entailed the development of upscaling protocols for large scale production of cellulose nanocrystals (CNC) from sawdust waste biomass to meet increasing end-user demands at the Biorefinery Industry Development Facility (BIDF). Secondly, despite CNC having excellent properties for potential applications in high performance products and materials, CNC applications are still in their infancy, thus needing the demonstration of high impact applications. To propose potential solutions to these problems, the purpose of this research was to firstly design up-scaled CNC production plants with production capacities ranging from 1 kg/day to 1000 kg/day. These upscaling protocols will ease the difficulty of upscaling the CNC production from the laboratory scale to industrial scale without pilot scale facilities. The second research purpose was to demonstrate the application of CNC in novel green construction materials. The widespread use of ordinary Portland cement (OPC) in the construction industry, and the current landfilling of fly ash are environmentally-degrading. Hence, the CNC-enhanced novel green construction materials used fly ash as a precursor to potentially replace OPC in the construction industry. Furthermore, a database of the mechanical, electrical, thermal, and microstructural properties of the novel green construction material was produced to guide further research and optimizations. Additionally, a universal iterative empirical framework was produced to develop novel green construction materials, whose properties can be customized per the requirements of the target application. Based on the two main research purposes, the dissertation was divided into two parts: Part A dealt with the up-scaled CNC production process design, and Part B dealt with the application of CNC in the development of novel green construction materials. Regarding the research design and methodology, the Project Life Cycle Management framework commonly applied in Industry, in conjunction with literary design standards and guidelines, were used in the process design. Software simulations were also used for certain aspects of the process design. The CNC production process design included a de-mineralization (process) water plant and an acid recovery plant. The equipment sizing and degree of automation were different for each production scale. For the development of the novel green construction material, meta-analyses coupled with statistical experimental design were used to optimize the experimental trials. The mechanical and electrical test results were used to generate three-dimensional response plots of the CNC effects, thus forming the property database. CNC was found to improve the strength, density, and corrosion resistance (dictated by the electrical resistivity) of the fly ash-based geopolymer construction materials produced at small quantities (optimally 1.7% by volume) when cured for 48 hours with sample rotation. The geopolymer exhibited endothermic properties based on the heat flow analysis, implying its suitability in thermal resistance applications. Furthermore, higher CNC concentrations were found to induce thermal stability during thermal variations in the curing and elevated temperature exposure. Overall, the application of CNC in green construction materials and the empirical framework for the custom development of green construction materials showed substantial potential, thus holding the ability to improve the commercial viability of novel green construction materials to improve their competition against OPC. The study concluded that the up-scaling protocols developed for CNC production from sawdust waste biomass can be applied in the absence of pilot scale facilities. Furthermore, this study demonstrated that CNC can be applied to develop high performance green construction materials. Only small quantities of CNC (less than 0.5% concentration) were required to improve the thermal and mechanical properties of the novel green construction materials. These small CNC concentrations yielded compressive strengths of up to 8000 kPa and generally reduced the mass loss of samples when exposed to elevated temperatures up to 7%. The broader implication of this project is that the implementation of the desired up-scaled CNC production plant can create employment and boost the economy while providing a steady supply of CNC to meet the growing end-user requirements. Furthermore, the two environmental issues of unsustainable industrial waste disposal and unsustainable OPC building materials can be solved by applying suitable industrial waste materials to produce novel green construction materials as alternatives to OPC using the empirical framework provided in this work.
Evaluation of paper substrates for microfluidic application in medical diagnostic kits.
(2018) Moodley, Revesa Sadasivan.; Land, Kevin.; Sithole, Bishop Bruce.; Van Zyl, Werner Ewald.; Andrew, Jerome Edward.
Recent studies in the biomedical field have shown the use of paper in microfluidic analytical devices. However, no studies have been undertaken to ascertain what type(s) of paper substrates are ideal for such microfluidic applications. Hence, this study was conducted to determine the feasibility of using different paper substrates for implementation in microfluidic analytical devices, specifically in the South African context, compared to currently used materials such as glass and silicone. In addition, fibres in paper substrates were substituted with nanofibrillated cellulose (NFC) fibres to ascertain the impact of NFC on the microfluidics of the paper substrates. The wicking rate of the substrates was the focus of the study, with high -resolution field emission gun-scanning electron microscopy and contact angle tests being used to support the results obtained. Solid wax printing was also conducted to determine whether the paper substrates were suited to fabrication for microfluidic applications. High-resolution morphological studies of the paper substrates showed that pore sizes of the pulp fibres were in the order sulphite> bleached kraft > unbleached kraft > Whatman No. 1 Chromatography Filter Paper > Whatman 3MM Chromatography Filter Paper > thermo-mechanical > recycled. It was concluded that the larger pore size of fibres correlated with faster wicking rates of the relevant paper substrates. The substitution of pulp fibres with NFC led to reduced pore size of the fibres thus leading to reduced wicking rates due to the presence of the small NFC particles. Contact angle is directly linked to the hydrophobicity of the substrate and is indicative of the resistance to absorption of a liquid. The results revealed that all the paper substrates were hydrophilic. However, the hydrophilicity of two of the substrates (sheets substituted with 100% NFC unbleached kraft pulp and 100% NFC recycled pulp) were higher than those of the other substrates indicating that, although these substrates were still hydrophilic in nature, their absorption of aqueous liquid would take longer periods of time. The results showed that Whatman glass microfiber GF/D filter paper was the fastest wicking substrate, using both dye and blood simulant as wicking liquids. Similarly, paper substrates made with recycled fibres exhibited the slowest wicking rates when using both wicking liquids. These results can be used when determining which of the substrates to use for paper-based microfluidic device (μPAD) application, whereby the desired detection time would be the factor used to establish which of the substrates to use. Comparison of vertical and horizontal tests showed varying results. In theory, the horizontal wicking test should result in a faster wicking rate than the vertical test, taking hydrostatic pressure into consideration. The majority of the substrates showed that the horizontal wicking rate was faster when using the dye solution, whereas vertical wicking was faster when using the blood simulant. Discrepancies between the results obtained from the dye and blood simulant experiments could be attributed to the additional viscosity drag when using the higher viscosity liquid (blood simulant), as well as possible capillarity differences of the samples. The results were used in conjunction with the morphological studies, whereby the pore size was correlated with the wicking rate. The solid wax printing test revealed that, in general, the substrates were not well suited to the fabrication method. The results showed that the wax was not able to penetrate through the depth of the sheet, hence allowing for the possibility of leakage of liquid from the channels. Two of the substrates (Whatman No. 1 Chromatography filter paper and paper made from sulphite pulp fibres containing 20% nanofibrillated cellulose) exhibited 100% wax penetration and could be considered for μPAD application. However, for paper substrates that do not meet requirements for μPAD applications, their pulp fibres could be chemically modified to induce hydrophobicity thus altering the microfluidic characteristics of the paper substrates.
Fractionation and valorisation of bark extractives from Eucalyptus species.
(2018) Masetlwa, Jethro.; Sithole, Bishop Bruce.; Andrew, Jerome Edward.
The notion of zero-waste in industrial production processes of widely used materials has gained momentum, as industries aim to gain revenue from waste materials which were previously considered as waste. Tree bark from wood obtained from sustainably managed plantations used in the production of timber and pulp industries is an underutilised waste that is mainly used for energy production in mills or left on plantations after debarking. Eucalyptus tree species are commonly used as raw-material in the pulp and paper industry throughout the world. In this thesis, the potential beneficiation of bark from South African planted Eucalyptus tree species (Eucalyptus grandis, Eucalyptus dunnii, Eucalyptus smithii and Eucalyptus nitens) as a source of valuable materials is investigated. Secondary metabolites such as phenolic components, terpenes, steroids and alkaloids can extracted from Eucalyptus bark. In this study, accelerated solvent extraction was investigated for extraction of components in the bark and the components were characterised by a variety of analytical techniques. The investigation was undertaken by optimising the extraction process using the following parameters, temperature (80 to 160℃), number of static extraction cycles (1-3 cycles), solvent type (80% v/v of ethanol or 50% acetone v/v), Eucalyptus species, and particle size (850-500 μm, 500-375 μm and <375 μm). The extraction process was optimised and response surface methodology (RSM) was used to model experimental data for statistical analysis of the Box-Beheknen design of the extraction process. A quadratic model was fitted, and optimum extraction parameters were a temperature of 117℃ with greater than 2 number of static extraction cycles, and bark particles greater than 355 μm. The two target objectives were total phenolic content and total extractive content when using ethanol as the extraction solvent. The amount of phenolic components in the bark extracts was determined by the Folin–Ciocalteu method which using gallic acid as a calibration standard and detection on a UV-vis spectrophotometer. Amongst the four Eucalyptus bark species studied, Eucalyptus dunnii contained the highest amount of phenolic components (5.52g/100g GAE) In addition to using the Folin–Ciocalteu method, the chemical compositions of acetone and ethanol extracts of the bark samples were determined using Pyrolysis-Gas Chromography/Mass Spectrometry. The analysis showed that condensed tannins, with a building block of catechol units, were the most abundant phenolic components present in the bark extracts. Other components that were detected in high amounts were terpenes and terpenoids, and smaller amounts of monoterpenes and sesquiterpenes. Steroid components were also detected, with 𝛽-sitosterol being the most predominant one. The extractive-free bark samples, remaining after removal of solvent extracts, was analysed using high pressure liquid chromatography to determine their chemical content of cellulose, hemicellulose and lignin.
Impact of hexenuronic acid on the physical and chemical properties of eucalyptus clonal pulps during ECF bleaching .
(2007) Andrew, Jerome Edward.
The work described in this dissertation was aimed at obtaining an understanding of

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Browsing Chemical Engineering by Author "Andrew, Jerome Edward."