Theses and dissertations (Engineering and Built Environment)
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Item Biosorption of Fe2+ from potable water using natural and modified sugarcane bagasse(2023-05) Ndebele, Nompumelelo Lindi GelsiahEven though some metals are crucial for the health and development of human bodies, their presence in higher concentrations is worrisome because it has a detrimental effect on people's health. These heavy metals cause cancer and cannot be broken down by biological processes. The removal of heavy metals from water using traditional techniques; such as reverse osmosis, precipitation, ion exchange; has been the subject of extensive investigation. However, because these processes are so expensive to run, a lot of research is currently focusing on using agricultural biomasses to remove these heavy metals. Dumping of this agricultural waste (sugarcane bagasse) in landfills creates dangers of spontaneous combustion, because of microbial activities. The functionality of circular economy depends on waste resources being utilized to their fullest potential, with almost no production of recoverable waste. In a circular economy, sugarcane bagasse is utilized as a fuel source for the boilers that generate process steam and electricity in the sugar mill facilities. Sugarcane bagasse is used in the manufacturing of paper and paper goods, as well as in the agricultural sector. Stakeholders across the value chain, from product design to waste management, This study fulfils the functionality of the circular economy where it looks at extracting the valuable components of the sugarcane bagasse, then further using the sugarcane bagasse to remove heavy metals from potable water. In this study, the adsorption capacities of unmodified and modified sugarcane bagasse for removing Fe2+ from potable water were investigated in batch experiment studies. Sugarcane bagasse comprises cellulose, hemicellulose and lignin. In order to determine the effect of removing/ extracting each component from the sugarcane bagasse, sugarcane bagasse was pretreated with different concentrations of sodium hydroxide and sulphuric acid, ranging between 0.5 wt% and 2.5 wt%, predominantly used to extract lignin and hemicellulose. A cellulosic structure was left behind after the simultaneous removal of both amorphous components (the lignin and the hemicellulose) using the combined pretreatments of sodium hydroxide and sulfuric acid. The advantages of extracting or eliminating these components came from their high value in many sectors. Lignin is used in the paper business and costs between R11 300 and R17 420 per ton, hemicellulose is used in the pharmaceutical sector and costs between R500 and R1000 per ton, and cellulose is utilized in the textile sector. The concentrations of all chemical pretreatments used on the sugarcane bagasse ranged from 0.5 to 2.5%, with alkaline pretreatments intended to extract lignin, acid pretreatments intended to extract hemicellulose, and combination pretreatments intended to remove both lignin and hemicellulose. While cellulose content increased from 32.02 to 65.65% after sodium hydroxide pretreatment, lignin and hemicellulose content reduced from 22.30 and 24.30% to 7.56% and 13.63%, respectively. Lignin and hemicellulose concentration for the sulphuric acid pretreatment went from 22.30 and 24.30% to 14.90% and 13.63%, respectively, while cellulose content went from 35.02 to 65.65%. After the sugarcane bagasse underwent chemical pretreatments, batch studies were conducted on both the natural and chemically pretreated sugarcane bagasse in order to determine how the removal of lignin, hemicellulose, and cellulose affected the performance of the biosorbents in the biosorption of Fe2+ from drinkable water. To assess the efficacy of natural and modified sugarcane bagasse on the Fe2+ removal, the operational parameters investigated in the batch experiments were initial concentration ranging from 1 to 30 mg/L; pH ranging from 2 to 7, contact time ranging from 5 -100 minutes, and adsorbent dose ranging from 0.2 to 1.4 g. For every variation investigation, one variable was varied at a time while keeping the other variables constant. The experimental runs done were repeated thrice and average values are reported throughout the study. According to the biosorption results, 1% NaOH was the best performing biosorbent for the alkali-pretreatment. The most effective biosorbent for the acidpretreatment variation was 2.5% H2SO4. The optimal combination for the pretreatment was (0.5% NaOH + 0.5% H2SO4). Regarding initial concentration variations, all biosorbents were most effective at a concentration of 1 mg/L, where natural sugarcane bagasse was able to remove 50% of Fe2+, 1% NaOH was able to remove 99.7% Fe2+, 2.5% H2SO4 removed 75.93% Fe2+, and the combined-pretreated biosorbent of (0.5% NaOH + 0.5% H2SO4) removed 87.17% Fe2+ . The increase in biosorbent dose led to an increase efficiency of the natural and chemically pretreated biosorbents. The highest removal of Fe2+ was obtained at 1 g (both for the natural and for all the pretreated biosorbents), with 32.2% for the natural; 79.04% for the 1% NaOH; 58.79% for the 2.5% H2SO4 and 70.73% for (0.5% NaOH + 0.5% H2SO4). Results of the study also showed that the highest removal of Fe2+ for the pH variation of 2-7 was at pH “6” for both the natural and pretreated biosorbents. For the variation of the agitation speed, the highest Fe2+ removal was at 160 rpm with 52% Fe2+ removal for the natural sugarcane bagasse. The Langmuir and Freundlich adsorption isotherms were used to study the biosorption mechanisms. Good correlation coefficients (R 2 ) of > 0.95 were obtained for both the Langmuir and Freundlich isotherms for both the natural and modified sugarcane bagasse, indicating that the biosorption followed both homogeneous and heterogeneity interaction between Fe2+ ions and active functional groups of the surface and pores of the biosorbents. Biosorption results for the natural sugarcane bagasse best fitted with the Langmuir isotherm with qmax of 0.770 mg/g, R 2 of 0.987 and RL of 0.938. The alkali and acid-pretreated biosorbents favoured both the Langmuir and Freundlich isotherms with R 2 > 0.95; RL < 1 and 1 𝑛 < 1. The highest qmax of 9.199 and 5.743 mg/g was obtained at 1% NaOH and 2.5% H2SO4, respectively. The combined pretreatment fitted best with only the Langmuir isotherm with R 2 of 0.987, the R 2 of the Freundlich isotherm was less than 0.9. The biosorption of Fe2+ followed both the pseudo-first-order and pseudo-second-order kinetic reactions with 𝑞𝑒(𝑒𝑥𝑝) in close proximity to 𝑞𝑒(𝑐𝑎𝑙𝑐) and R 2 > 0.9. These results showed that sugarcane bagasse had great adsorption capacity after removing the valued components, namely, lignin and hemicellulose. Characterization studies, which included FTIR, XRD, BET and SEM, were also carried out on the natural and pretreated bagasse before and after adsorption experiments. FTIR confirmed the existence of carbonyl, hydroxyl and carboxyl functional groups as major groups responsible for the adsorption of Fe2+ onto the natural and pretreated sugarcane bagasse. XRD revealed that the natural structure of the sugarcane bagasse was of native cellulose consisting of both amorphous and crystalline regions; this structure became more crystalline after the chemical pretreatments as the crystallinity index increased from 39.04% to 66.85% at 1% NaOH; 57.47% at 2.5% H2SO4; and 57.92% at (0.5% NaOH + 0.5%H2SO4). The natural sugarcane bagasse structure featured rough surfaces, according to SEM data, and the main constituents were silicon (Si), carbon (C), and oxygen (O). According to the BET data, employing 1% NaOH, 2.5% H2SO4, and (0.5% NaOH + 0.5% H2SO4), respectively, the initial surface area of 0.904 cm3 /g rose to 1.503, 1.233, and 1.376 cm3 /g and the pore size of 56.33 ̊A increased to 99.63, 93.680, and 99.10 ̊A. According to the EDS data, sodium hydroxide pretreatment performed better in terms of adsorption, followed by combined pretreatment and sulphuric acid. The natural sugarcane bagasse, 1% NaOH, 2.5% H2SO4, and (0.5% NaOH + 0.5% H2SO4) were able to biosorb 0.77, 7.89, 1.63, and 3.8% Fe2+, respectively.Item Evaluating the performance of an eggshell-bagasse biosorption system in removing lead and cadmium from aqueous solutions(2021-02) Harripersadth, Charlene; Musonge, Paul; Isa, Yusuf MakarfiIn this research investigation, the simultaneous use of 2 biomaterials, sugarcane bagasse and eggshells, were applied as biosorbents in the treatment of metal laden effluent. Under the characterisation measurements investigated, it was found that carbon, calcium and oxygen atoms which constitute carboxylic and carbonate functional groups were prominent in eggshells, whereas for bagasse, it was carbon, hydrogen and oxygen atoms constituting hydroxyl and carbonyl groups. Batch studies were conducted to investigate the effect of fundamental process variables such as particle size (75 – 250 μm), initial metal ion concentration (40 – 240 mg/L), pH (2 – 7) and contact time (0 – 120 min). With respect to the equilibrium studies, the applicability of the Langmuir isotherm implied a monolayer formation of metal ions onto the surface of both biomaterials with the maximum amounts of Pb and Cd adsorbed based on 1 g of biosorbent being 277.8 and 13.62 mg/g for eggshells and 31.45 and 19.49 mg/g for bagasse, respectively. Moreover, kinetic modelling revealed that the process was well described by the pseudo – second order model for both Pb and Cd using eggshells and bagasse. Fixed bed studies were used to assess the dynamic adsorption behaviour of the eggshell – bagasse system using a lab – scale adsorption column of 2.3 cm in diameter and 30 cm in height. The effect of bed depth (4 – 12 cm) on 5 adsorbents (eggshells, bagasse, adsorbent A, adsorbent B and adsorbent C) in the removal of Pb were investigated. Adsorbents A, B and C were a combination of both eggshells and bagasse with adsorbent A constituting 75wt % bagasse and 25wt % eggshells, adsorbent B constituting 50wt % bagasse and 50wt % eggshells and adsorbent C constituting 25wt % bagasse and 75wt % eggshells. The column experiments highlighted an improvement in bed performance with an increase in bed depth resulting in greater mass transfer zones, breakthrough times and larger quantities of effluents treated. Two kinetic models (Thomas and Yoon–Nelson) were used to interpret the breakthrough curves where the data showed good fits to both models used. In determining the efficacy of the eggshell – bagasse biosorption system, adsorbent C was found to be most proficient in the removal of Pb with eggshells, adsorbent B, adsorbent A and bagasse following suit. The results from this investigation strongly suggest the plausible reuse of agricultural waste materials in the treatment of contaminated effluent through the biosorption process.Item The effect of heavy metal composition on the performance of sugarcane bagasse as an adsorbant in water treatment(2021-04) Buthelezi, Nokulunga Priscilla; Isa, Yusuf MakarfiWastewater produced by the industries is potentially harmful to the ecosystem because of various contaminants like heavy metals that find their way into soil and water supplies. Industrial waste constitutes different kinds of metal which contaminate natural water. Heavy metals can build up in the environment and enter living organisms through chain elements such as the food chain and therefore, pose a major health risk to living organisms. The situation has been worsened by the absence of broadly accepted heavy metal treatment techniques, thus this challenge continues to receive considerable attention from stakeholders including scientists and researchers. While many technologies have been proposed such as reverse osmosis, flocculation, ion exchange and so on and so forth, they continue to suffer from a number of drawbacks including generation of secondary wastes and cost ineffectiveness. Thus, in the present study, adsorption was chosen as a cost effective, efficient, and environmentally friendly treatment process. Sugar cane milling production produces a lot of sugar cane bagasse which is considered as environmental waste if not disposed properly. It is imperative to remove heavy metals from polluted water before discharging it into the environment, rivers and lakes using sustainable techniques. Heavy metal removal from wastewater using low-cost adsorbents like sugarcane bagasse addresses two problems: removal of pollutants from water and utilization of agricultural waste. This study evaluated the performance of sugarcane bagasse in the removal of heavy metals. Sugarcane bagasse was characterized to determine the functional groups, the porosity and surface area, crystallinity and morphology using FTIR, SEM and XRD. One factor at a time (OFAT) approach was used to evaluate the effect of operating parameters on the removal of heavy metal ions. A 3-system component of the stock solution of synthesized wastewater namely single, binary and ternary were studied. The 3 metal ions evaluated were Copper, Chromium and Cadmium. The factors considered in the OFAT design of experiments were contact time (30-240 mins), adsorbent dosage (5-30g/L), initial concentration (50-500 mg/L), pH(2-9), and particle size (75-600 μm). It was observed that all adsorption parameters had an effect on the adsorption rate. However, an adsorption dosage had a greater impact on the adsorption rate. An increase in the adsorption dosage from (5-20 g) showed that the percentage removal efficiency for chromium, copper and cadmium increased from (40-72%, 44-75% and 39-59%) in a single metal system. In addition, the percentage removal increased from (34-62% for chromium, 47- 78% for copper, and 34-62% for cadmium) in a binary metal system. Furthermore, the percentage removal increased from (38-52%, 40-59% and 24-43%) for chromium, copper, and cadmium in a ternary metal system. Adsorption capacity of the adsorbent was determined using the optimal operating parameters obtained from the OFAT design of experiments. Langmuir and Freundlich isotherms were used to analyze the adsorption data. The OFAT design of experiments resulted in producing the optimum conditions for adsorption. The optimum conditions for maximum adsorption were, contact time (180 mins), initial concentration (50 mg/L), pH (7), dosage (20 g), particle size (340-450 μm) and a mixing speed of 150 rpm. Adsorption capacities differed between the 3 system components. Maximum adsorption capacities of 38.41 mg/L were registered for copper ions and was recorded for the single component system. Stock solutions containing copper ions registered the highest adsorption capacity. There was a significant decrease in the maximum adsorption capacities for copper ions of the binary and ternary system components which were 21.45 mg/L and 1.237 mg/L respectively. This was attributed to the co-metal ion dependence in both the binary and ternary system components. In conclusion, the study showed that sugarcane bagasse can be used as an adsorbent in the efficient removal of heavy metal ions present in wastewater.Item Evaluation of Kaolinite and activated carbon performance for CO2 capture(2021-03) Akpasi, Stephen Okiemute; Isa, Yusuf MakarfiGlobal climate change is one of the major threats facing the world today and can be due to increased atmospheric concentrations of greenhouse gases (GHGs), such as carbon dioxide (CO2). There is also an immediate need to reduce CO2 emissions, and one of the potential solutions for reducing CO2 emissions is carbon capture and storage (CCS). This work investigated the performance assessment of kaolinite and activated carbon (AC) adsorbent for CO2 capture. In particular, the effect of operating parameters such as temperature, bed height, inlet gas flow rate etc. on CO2 adsorption behaviour of the adsorbents was also investigated. Extensive research on the development of adsorbents that can adsorb large amounts of CO2 with low energy consumption has recently been carried out. In CO2 adsorption technology, the challenge is to develop an adsorbent that is not only non-toxic, eco-friendly, and cost-effective, but also has the potential to extract CO2 gas from a mixed gas stream selectively and effectively. Due to the possibility of a potential adsorbent due to its low cost, rich natural abundance and high mechanical and chemical stability, this study proposes kaolinite. As the presence of clay minerals in soils serves as a pollutant collector to enhance the atmosphere, kaolinite has the potential to be an efficient adsorbent for CO2 capture. Kaolinite was investigated as an adsorbent in this research to confirm if it is suitable for CO2 capture. Kaolinite/activated carbon composite adsorbents were synthesized. Sugarcane bagasse was used in preparing the activated carbon (AC). ZnCl2 was impregnated onto sugarcane bagasse during the preparation of activated carbon (AC) to improve the physical properties (surface area, pore size and pore volume) and the CO2 adsorption capacity of the activated carbon (AC) adsorbent developed. The materials were characterized and tested for CO2 adsorption (activated carbon and kaolinite). BET, FTIR and SEM studies were used to classify the adsorbents for their surface area and pore properties, functional groups, and surface morphology, respectively. BET analysis was conducted and the pore volume, pore size and surface area of the adsorbent materials were reported. Functional groups were actively present in the adsorption process. This was verified using FTIR spectroscopy. The kaolinite adsorbent was not feasible for CO2 capture. BET, SEM, and custom-built CO2 adsorption equipment have confirmed this. In contrast to literature, the CO2 adsorption capacity of kaolinite was low. This is due to the fact that kaolinite used in this study is not suitable as adsorbent for CO2 capture as they exhibited a low CO2 adsorption capacity. The results obtained in this study show that temperature, bed height and inlet gas flow rate influenced the adsorption behaviour of activated carbon (AC), kaolinite and kaolinite/activated carbon composite adsorbent during CO2 capture. At 30 0C, activated carbon (AC) exhibited an adsorption capacity of 28.97 mg CO2/g, the highest capacity among all the adsorbents tested. Kaolinite-activated carbon composite adsorbent offered CO2 adsorption capacities of 18.54 mg CO2/g. Kaolinite provides the lowest capacity of 12.98 mg CO2/g. In conclusion, this research verified that CO2 adsorption with kaolinite and activated carbon is favoured at low temperatures, low operating CO2 flowrates and high column bed height.Item Production of biogas from sugarcane residues(2018) Malunga, Sthembiso Patrick; Isa, Yusuf MakarfiDue to high production costs facing South African sugar manufacturing industries, production of sugar alone may not be profitable. For sugar manufacturing industries to be economically viable, a novel approach research on other value-added potential products is of paramount importance. The aim of this work was to conduct a feasibility study on biogas production from anaerobic digestion (AD) of sugarcane bagasse, molasses and leaves using cow dung as co- substrate. Three sets of 12 independent batch laboratory experiments for each residue were carried out at temperature of 35oC and hydraulic retention time (HRT) of 14 days using 500 ml bottles as digesters. Design-Expert software was used for design of experiment, process optimisation and process modelling. One variable at a time (OVAT) and 2-Dimensional (2-D) graphical analysis methods were used to analyse the effects of cow dung to sugarcane residues (C:SR) feed ratio, media solution pH and digester’s moisture content on biogas volume, methane yield and kinetic constants. The results indicated that the effect of C:SR feed ratio, media solution pH and digester’s moisture content on biogas volume, methane yield, biogas production potential, maximum biogas production rate and lag phase is mutually reliant between all variables, i.e., depended on conditions of other process variables. The optimum biogas volume generated by bagasse, sugarcane leaves, and molasses experiments were found to be 305.87 ml, 522.69 ml and 719.24 ml and respectively. The results showed that the optimum methane yield achieved by bagasse, sugarcane leaves, and molasses experiments were 28.75 ml/gVS, 87.18 ml/gVS, and 85.32 ml/gVS respectively. The overall results showed that sugarcane bagasse, molasses and leaves can be potentially converted into biogas through AD process.