Theses and dissertations (Applied Sciences)
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Item Conversion of sugarcane bagasse into carboxymethl cellulose(2020-11) Makhanya, Fezokuhle Mfundo; Deenadayalu, NirmalaThe process of converting sugarcane into sugar has a high percentage of dry residue that remains after the juice has been extracted, the dry residue is referred to as sugarcane bagasse (SCB). The focus of this study has been on using sugarcane bagasse to extract cellulose from the matrix and converting it into carboxymethylcellulose (CMC). This has been achieved via a two-step synthesis process. Mill run sugarcane bagasse was used as received and was pre-treated using NaOH for the purpose of extracting cellulose from the sugarcane bagasse. The extractant was refluxed separately using two different nitric acid (HNO3) concentrations namely 8 M (cellulose sample 1) and 4 M (cellulose sample 2) in 20 % (v/v) ethanol to obtain cellulose. The extracted cellulose was obtained in yields of 37 % and 40 % for the 8 M and 4 M HNO3 concentrations. The extracted cellulose was converted into carboxymethyl cellulose. The synthesis was done by a carboxymethylation reaction where the cellulose was reacted with different NaOH concentrations (m/v %) namely 20 %, 25 % and 30 %. The CMC yield (m/m %) %) was 120 %, 125 % and 140 %, respectively at the different NaOH concentrations (20 %, 25 % and 30 %). The higher concentration of NaOH facilitates greater carboxymethylation. The extracted cellulose, synthesised CMC and the commercial samples of cellulose and CMC were characterized using Fourier transform infra-red spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The FTIR spectrum of the commercial cellulose exhibited peaks at 3334 cm-1, this peak was characteristic of the –OH stretching vibration. Cellulose samples 1 and 2 showed peaks at 3306 cm-1 and 3331 cm-1, respectively for the similar vibration. The commercial CMC sample showed FTIR peaks at 1400 cm-1 and 1600 cm-1, which corresponded to the carboxymethyl substituent. The extracted CMC from sugarcane bagasse showed the similar peaks at 1439 and 1631 cm-1, respectively. The TEM and SEM images for all cellulose samples showed that the spherical shape of commercial and extracted cellulose were similar in length and width, the extracted cellulose samples appear to be longer in length compared to the commercial cellulose. The TEM results for all cellulose samples appear to be similar from the images. Both commercial and extracted CMC sample TEM images showed highly dispersed and crystalline particles that are consistent with those observed for carboxymethylated cellulose. The CMC particles observed appear to be dark spots that are spherical. SEM images for CMC samples showed a contrast to cellulose samples, the surface was smoother in appearance that correlated strongly with CMC SEM images observed in literature and the commercial sample. XRD diffraction patterns showed two significant peaks at 2Ɵ = 15° and 22.5° that confirmed the presence of cellulose I and cellulose II, respectively, in both the commercial and extracted cellulose samples. Both commercial and synthesised CMC samples had a single peak at approximately 2Ɵ = 20°, characteristic cellulose peaks are no longer visible on the diffractograms. The TGA scans showed that the cellulose sample degraded similarly to the commercial cellulose sample. The TGA scans of synthesised CMC and the commercial CMC samples showed similar degradation patterns. DSC scans also showed similar trends for the commercial and synthesised CMC samples. The DSC curves showed that all samples had two major peaks: a small peak for moisture loss between 50 °C - 90 °C and a more significant peak at approximately 350 °C due to decarboxylation and CO2 bond breakage. The degree of substitution (DS) for the commercial CMC sample was 0.420 and for the extracted CMC samples there was an increase in DS to 0.357, 0.366 and 0.420 which correlated with an increase in NaOH concentration (20 %, 25 % and 30 % (w/v)), respectively. Characterization for this study confirmed the successful delignification of sugarcane bagasse as confirmed by the similar properties of commercial cellulose. Furthermore, the carboxymethylation was successfully achieved at various NaOH concentrations. The study gave insight on how each of the parameters optimized affected the production of the bio-derived cellulose and CMCs. A comparision of the commercial cellulose and CMCs with the bio-derived cellulose and CMCs showed that they were successfully extracted and synthesised, respectively.Item Comparison of lignin yield from sugarcane bagasse pellets using liquid hot water and ionic liquid pretreatment methods(2019) Gnana, Gueh Charles; Deenadayalu, NirmalaIn this research work, lignin yield from sugarcane bagasse pellets (SBP) was investigated after treatment of sugar cane bagasse with liquid hot water (LHW) and enzymatic hydrolysis followed by ionic liquids (ILs) and only ionic liquids pretreatment methods. In the LHW and ionic liquid methods, the SBP were first treated with LHW at 200 °C, for 30 minutes in a suitable reactor, for removal of hemicellulose. The complex cellulignin residue was treated separately with either of two ionic liquids namely: 1-ethyl-3- methylimidazolium acetate ([Emim][OAc]) or 1-butyl-3- methylimidazolium hydrogen sulphate ([Bmim][HSO4]), using microwave digestion at varying time intervals. Theionicliquidmethodinvolvedthepretreatmentofsugarcanebagasse pelletswith either 1-ethyl-3-methylimidazolium acetate or 1-butyl-3-methylimidazolium hydrogen sulphate followed by microwave digestion at varying time intervals. Ultraviolet (UV) spectroscopy at a wavelength of 280 nm was used as a tool for quantification of lignin. The different functional groups of the extracted lignin were confirmed using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Thermogravimetric analysis (TGA) provided information on thermal characteristics of the extracted lignin. In addition to material characterization, mixed factorial ANOVA was performed to compare the extracted lignin yield using the LHW and IL and the ionic liquid pretreatment methods. High performance liquid chromatography (HPLC) was used to identify the C5 sugars in the hydrolysate after LHW pretreatment. X-ray diffraction (XRD) was used to identify cellulose peaks of cellulignin and SBP and ILs treated samples. The results indicated that the lignin yield from sugarcane bagasse pellets after liquid hot water treatment and enzymatic hydrolysis was 37.8 % (m/v). The highest percentage yield of lignin extracted from the complex cellulignin (LHW and IL) was found to be 68.00 % (m/v) and 32.04 % (m/v) for [Emim][OAc] and [Bmim][HSO4], respectively for the optimized reaction time of 10 minutes. However, 67.25 % (m/v) and 48.94 % (m/v) of the extracted lignin were obtained for the pretreated SBP with [Emim][OAc] and [Bmim][HSO4], respectively for a reaction time of 20 minutes. This comparative study revealed that, there is no significant difference between the yield of lignin extracted from the complex cellulignin (68.00%) and sugarcane bagasse pellets (67.25 %).The sugarcane bagasse pellets is the preferred method since it doesn’t require high energy input.Item Extraction and characterisation of cellulose nanocrystals (CNCs) from sugarcane bagasse using ionic liquids(2019) Mdletshe, Gcinile Pretty; Deenadayalu, Nirmala; Suprakas, S.Lignocellulosic materials have the potential to partly replace fossil-based resources as a source of bio-fuels, bio-chemicals, bio-composites and other bio-products. In this study, ionic liquids (ILs) were used in the pre-treatment of ground sugarcane bagasse (SCB). The ILs used were 1-butyl-3-methylimidazolium hydrogen sulphate or 1-butyl-3-methylimidazolium methyl sulphate at varied times. The ILs were able to remove lignin and hemicellulose from biomass. The IL [bmim][HSO4] had the highest amount of lignin removed after 12 h than all samples. Moreover, it resulted in the greatest cellulose amount. Milled SCB was pre-treated with IL/dimethyl sulphoxide (DMSO) mixtures. The IL [bmim][HSO4] was able to produce cellulose nanocrystals (CNCs) at 90 % IL and 100 % IL. The other IL failed to produce CNCs. Freeze drying the CNC suspension showed morphologies of long fibrous structures and rods which were evident in the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The crystallinity index of cellulose in the form of CNCs was calculated from powder X-ray diffraction (P-XRD). Thermal analysis of the CNCs was obtained from thermogravimetric analysis (TGA). Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to confirm the absence of lignin and hemicellulose in CNCs. The size distribution of CNCs was obtained by using a dynamic light scattering (DLS) which showed that all the CNCs for the 100 % IL [bmim][HSO4] pre-treatment had a length < 500 nm. It was found that [bmim][HSO4], with no DMSO, was the most effective in terms of cellulose dissolution and the crystal sizes of CNCs. The conversion of cellulose to CNCs was successful with a 80 % and 100 % conversion for 90 % [bmim][HSO4]/DMSO and 100 % [bmim][HSO4], respectively.Item A study to identify a feasible route for the production of the monomer 2-vinylfuran from furan by evaluating the effect of variables on the final yield and to recommend suitable conditions applicable to the chemical industry(1992) Gengan, Robert Moonsamy; Reimann, R. H.2- Vinylfuran has been synthesised from furan, obtained from furfural a degradation product of bagasse, and has the potential to be used as a monomer in the Polymer Industry. Furan was successfully reacted with ethylene under catalytic conditions of palladium (II) acetate and copper (II) acetate to produce 2-vinylfuran, via a direct substitution reaction, at atmospheric pressure and a temperature of 9Y C for two hours in dimethylformamide.Item Selective extraction of lignin from lignocellulosic biomas using ionic liquids(2016) Mkhize, Thandeka, Y.; Deenadayalu, Nirmala; Reddy, P.Globally there is a drive for the use of renewable materials for the production of biofuels or high-end value chemicals. The current production of chemicals from crude oil refining is unsustainable and leads to global warming effects. Biomass is the most attractive renewable energy source for biofuel or fine chemical production. Sugarcane bagasse is a by-product of the sugar milling industry and is abundantly available. In this study lignin was sequentially extracted using ionic liquids. The ionic liquids (ILs) 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) and triethylammonium hydrogen sulfate ([HNEt3][HSO4]) were used to fractionate the sugarcane bagasse. The pre-treatment of sugarcane bagasse was carried out at different temperatures ranging from 90 - 150 0C and reaction times ranging from 1 - 24 h in a convection oven at a 10 % biomass loading. Both ILs were able to dissolve the raw bagasse samples at 120 0C with [Emim][OAc] giving a lignin maxima of 28.8 % and a low pulp yield of 57 % after 12 h; [HNEt3][HSO4] gave a lignin recovery of 17.2 % and low pulp yield of 58.5 % after 6 h. Regenerated lignin was obtained by adding ethanol/ water to the mixture followed by vacuum filtration. The regenerated pulp materials were characterized by Scanning Electron Microscope (SEM) to study the morphology; Fourier Transform Infrared Spectroscopy (FTIR) to study the characteristic bands and thermal analysis to study the thermal stability.Item Evaluation of biohydrogen production potential of sugarcane bagasse using activated sludge in a dark fermentation process(2016) Reddy, Karen; Bux, Faizal; Kuttun Pillai, Sheena Kumari; Gupta, Sanjay KumarAnaerobic dark fermentation is an efficient biological process to produce hydrogen from waste material. In South Africa, this technology has not been explored adequately to extract energy from biological wastes. Within the KwaZulu Natal region of South Africa, the sugar industry is a prominent venture that produces mass quantities of sugarcane bagasse amongst other waste products. This by-product can be an ideal source of substrate for biohydrogen generation. In this study, sugarcane bagasse was used as the main substrate for biohydrogen production by anaerobic fermentation using sewage sludge as the inoculum. Different pre-treatment methods were employed to maximize the release of fermentable sugars from the lignocellulosic biomass. Among the different pre-treatment methods employed, the maximum sugar yield (294.4 mg/g) was achieved with 0.25% H2SO4 for 60 minutes at 121°C. Prior to inoculation, the sewage sludge was also subjected to thermal pre-treatment to eliminate methanogens. Thermal pre-treatment of inoculum sludge for 30 min was effective in eliminating methanogens. Fluorescence in situ hybridization was used to positively identify the hydrogen producing bacteria present before and after treatment. The pre-treated substrate and inoculum was integrated into a dark fermentation process to further optimize the effect of pH, substrate to biomass, iron and magnetite nanoparticles on hydrogen production. The maximum hydrogen production (1.2 mol/mol glucose) was achieved at a pH range of 5-6, a substrate to biomass ratio of 3.5, and iron and magnetite nanoparticle concentration of 200 mg/L. Microbial analysis using quantitative polymerase chain reaction has confirmed the dominance of Clostridium spp. in the reactor. The highest hydrogenase gene activity (number of copies of hydrogenase gene expression/ng DNA) was recorded in the reactor supplemented with magnetite nanoparticles with lowest being in the raw sludge. There was a direct positive correlation between the hydrogenase gene copy number and the hydrogen yield obtained at different reactor conditions. Scanning electron microscopy was a useful to visually analyse the interaction of microorganisms with activated sludge. This study highlights the significance of anaerobic microorganisms from waste sludge being able to utilize agricultural waste material to produce biohydrogen which could be further scaled up for continuous hydrogen production. In addition, statistical tools used to predict the possible sugar (Design of experiments) and hydrogen yields (Gompertz model) produced would be helpful in saving time during full-scale operation of biohydrogen producing reactors.Item Production of levulinic acid from sugarcane bagasse(2016) Mthembu, Lethiwe Debra; Deenadayalu, Nirmala; Reddy, P.The main aim of this work was to produce levulinic acid (LA) from sugarcane bagasse (SB) and since there is approximately 3 000 000 tons of bagasse produced per annum by 16 factories that are located on the north coast of Kwa-Zulu Natal, after the extraction of sugar. For this project fructose was firstly used for the production of LA, thereafter SB was used to produce LA. Cellulose was extracted from sugarcane bagasse using two types of pre-treatments namely (i) acid-alkali pre-treatment and (ii) liquid hot water (LHW). In the latter method acid hydrolysis and enzymatic hydrolysis was used to hydrolyse cellulose to glucose. For the acid-alkali pre-treatment work, two types of bagasse was used namely (i) mill-run bagasse and (ii) depithed bagasse and for the LHW a mill-run bagasse (pellets form) was used. In both pre-treatment methods the glucose solution was then acid catalysed by two different acids (i) an environment friendly acid, methanesulfonic acid (MSA) and (ii) sulphuric acid, producing levulinic acid. The results showed that MSA and sulphuric acid produced almost the same yield of LA but, MSA is preferred for the production of LA since it is less toxic and less corrosive than sulphuric acid.Item Preparation, isolation and characterization of nanocellulose from sugarcane bagasse(2016) Mashego, Ditiro Victor; Deenadayalu, NirmalaCellulose is a sustainable, abundant biopolymer derived from a variety of living species such as plants, animals, bacteria and some amoebas. An attractive source of cellulose for industrial uses is agricultural waste, as this use does not jeopardize food supplies and improves the local rural economy. Sugarcane bagasse (SCB) is one of the main biomass wastes from sugar production and represents 30–40 wt % of sugar production waste. In 2008, South Africa produced on average 22 million tons of sugar cane each season from 14 sugar mill supply areas which resulted in 7,9 million tons of “waste” bagasse. In this study cellulose nanocrystals were prepared from soda pulped sugarcane bagasse by acid hydrolysis followed by separation using centrifugation, ultrasonication and dialysis. Transmission Electron Microscopy (TEM) images showed nanocrystals of approximately 300 nm in length and 20 nm in width. Thermogravimetric Analysis and Differential Thermogravimetry (TGA and DTG) profiles of FD CNC, MCC and Pulped bagasse all had characteristic onset and decomposition temperatures indicating a change in the structure after chemical treatments. Particle size distribution measurements corroborated with the TEM and FE - SEM results and showed that the majority of the nanocrystals were in the 100 – 300 nm range. Attenuated Total Reflectance – Fourier Transform Infra Red (ATR - FTIR) analysis showed functional group changes as the amorphous regions of the polymer were removed revealing the ordered crystalline portions. These were further confirmed by an increase in the Lateral Orientation Index (LOI) of the samples as the nanocrystals were isolated. X - Ray Diffraction (XRD) Crystallinity Index (CrI) calculations showed a steady increase in the crystallinity of the materials from pulped bagasse to MCC to FD CNC.