Theses and dissertations (Applied Sciences)
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Item A comparative study of supercritical fluid extraction and accelerated solvent extraction of lipophilic compounds from lignocellulosic biomass(2022-09) Khanyile Andile; Sithole, B.B.; Paul, Vimla; Andrew, Jerome EdwardLipophilic compounds are non-structural, heterogeneous compounds rich in terpenes, sterols, fatty acids, hydrocarbons, and glycerides. They have found widespread uses in different industries, such as the pharmaceutical, medical, cosmetic and nutraceutical sectors. They are typically extracted from wood using traditional techniques such as solvent extraction hydro- and steam- distillation. However, these techniques have several drawbacks such as long extraction times, high energy consumption, extensive solvent use and degradation of thermosensitive compounds, which are highly volatile. In this study, supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE) were evaluated to extract lipophilic compounds from lignocellulosic biomass such as pinewood sawdust and Cannabis Sativa L. Their advantages of using low amounts of solvent, short extraction times and high selectivity allow them to be used as an alternative extraction technique to traditional methods. Moreover, SFE uses carbon dioxide, which is safe, cheap and readily available, and it does not alter the structure of the compounds. In contrast, ASE uses elevated temperatures and high pressures to prevent the evaporation of highly volatile compounds. In order to solve challenges from both an economic and an environmental perspective, the interaction of process conditions on lipophilic compounds extraction efficiency was modelled and optimized using Response Surface Methodology (RSM) and BoxBehnken design (BBD). The extraction variables optimized for pinewood sawdust compounds were, SFE: co-solvent (ethanol) flow rate (1-2 ml/min), carbon dioxide (CO2) flow rate (1-3 ml/min), Temperature (40-60 °C) and pressure (200-300 bar), and for ASE: static time (10-15 mins), static cycle (1-3) and temperature (80-160 °C). The process parameters were optimized, and the experimental data was modelled using RSM for statistical analysis of the BBD extraction process. The experimental data's quadratic polynomial models gave a coefficient of determination (R2 ) of 0.87 and 0.80 for ASE and SFE, respectively. The optimum conditions of ASE were temperature (160 °C), static time (12.5 mins), and static cycle (1), which resulted in a maximum yield of 4.2%. The optimum SFE conditions were temperature (50 °C), pressure (300 bar), CO2 flow rate (3.2 ml/min), and a 2 ml/min co-solvent (ethanol) flow rate that yielded 2.5% lipophilic compounds. The extraction efficiency of pinewood sawdust lipophilic compounds with ASE was higher compared to the SFE. Although ASE uses high temperatures that may degrade thermolabile compounds, the short extraction times may work in their favor since the extracts are not exposed to high temperatures for long periods. SFE uses low temperatures and long extraction times compared to ASE. Several properties affect the extraction efficiency, such as volatility, dissolving power, solubility, and fluid density of the extracting solvent. The extraction efficiency of lipophilic compounds by SFE may be affected by the supercritical fluid's solubility and differences in densities at different pressures. In ASE, the high yields were influenced by the high polarity of the solvent mixture and temperature with a short extraction time. The extraction variables optimized using RSM for Cannabis Sativa L. for SFE were pressure (200-300 bar), co-solvent (ethanol) flow rate (1-2 ml/min) and CO2 flow rate (1-2 ml/min). The R2 was determined to be 0.9108. The optimum conditions were 300 bar pressure, 1 ml/min co-solvent (ethanol) flowrate, and 2 ml/min CO2 flowrate, which gave a maximum yield of 88%. The high efficiency observed was brought by the increase in the flow rate of CO2 at high pressures, which reduces the mass transfer resistance, while the cosolvent enhanced the solvating power of CO2. The ASE had a high extraction efficiency for the pinewood sawdust lipophilic compounds. However, the method's selectivity was very low according to the results obtained by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). The thermosensitive compounds, such as terpenes, decreased from 2.01% to 1.69% upon the addition of Tetramethylammonium hydroxide (TMAH). The initial concentration of terpenes was 7.21% in pinewood sawdust by SFE. Upon the addition of TMAH, the concentration of terpenes of the pinewood sawdust decreased to undetectable levels. The initial concentration of the terpenes of Cannabis Sativa L. was 14.29% and decreased in the presence of TMAH to 0.39%. The Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of lipophilic compounds functional groups and a fingerprint region of lipophilic compounds of pinewood sawdust and Cannabis Sativa L. Thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) showed high thermal stability (250 – 400 ℃). This research demonstrated the ability of SFE to extract lipophilic compounds from pinewood sawdust Cannabis Sativa L.Item Synthesis of lactic acid using hydrogen cyanide extracted from cassava (Manihot esculenta) leaves(2022-05) Ilunga, Monga; Paul, Vimla; Zinyemba, Orpah; Muniyasamy, SudhakarRacemic lactic acid (2-hydroxypropanoic acid) has gained interest in the food and non-food industries and in producing biodegradable and biocompatible lactic acid polymers. Although racemic lactic acid is conveniently synthesised by chemical synthesis via the DL-lactonitrile route, it can also be produced by the fermentation process provided that suitable microorganisms and substrates are used. However, regardless of the sustainability issues associated with the fermentation process, it is the preferred production method since the chemical process relies on fossil fuel resources. In this context, this study aims to extract hydrogen cyanide (HCN) from cassava (Manihot esculenta Crantz) leaves and then use it to chemically produce racemic lactic acid. Cassava leaves were chosen as a natural source of HCN since they release 20 times more HCN than the tubers. HCN is produced by endogenous enzymes (linamarase and hydroxynitrile lyase) hydrolysing the cyanogenic glucosides (linamarin and lotaustralin). Following 120 minutes of maceration at 30 °C, the released HCN was extracted for 45 minutes under vacuum at 35 °C – 45 °C and collected in 400 mL of 5.104 mol/L sodium hydroxide (NaOH) solution (absorbing solution) to give sodium cyanide (NaCN) solution. The extraction process was repeated until saturation of the absorbing solution was achieved. The final concentration of NaCN solution determined by the alkaline picrate method was found to be 4.0421 mol/L. Furthermore, the sodium carbonate (Na2CO3) and residual NaOH content in control and sample sodium cyanide solutions were also determined. The Na2CO3 content was 0.72 % in the control NaCN solution and 2.49 % in the sample NaCN solution. The residual sodium hydroxide content was 2.61 % in the control sodium cyanide solution and 4.20 % in the prepared sodium cyanide solution. 79.241 g of NaCN crystals (0.19 % yield, green NaCN) were obtained from 42.750 kg of fresh cassava leaves. The suggested approach was successful in preparing NaCN, as evidenced by X-Ray Diffraction (XRD), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS) results. Control and green NaCN both contained sodium carbonate impurities, as shown by these spectral techniques. Titration tests revealed that the latter was 0.61 % and 2.29 % in control and green NaCN, respectively. In addition, titration studies indicated that the residual NaOH content in control NaCN was 1.63 % and 4.68 % in green NaCN. The high carbonate content can be explained by the reaction between residual sodium hydroxide and atmospheric CO2. Reproducibility and repeatability tests were done to evaluate the reliability of the hydrogen cyanide extraction method. Racemic lactic acid was synthesised using a four-step process. 73 mL of DL-lactonitrile (2- hydroxypropanenitrile) (81.1 % yield, 59.7 % pure) was prepared by reacting 75 mL of acetaldehyde with hydrogen cyanide generated in-situ from green sodium cyanide (62.190 g in 150 mL of Milli-Q water) in the presence of 37 % hydrochloric acid (100 mL). 35 mL of crude racemic lactic acid (84.1 % yield, 14.9 % pure) was prepared by hydrolysing 40 mL of DLlactonitrile with 8 mol/L hydrochloric acid (40 mL). Crude racemic lactic acid underwent a two-step purification process in the presence of concentrated sulphuric acid (5 mL), used as the catalyst. 35 mL of crude lactic acid was first esterified with excess methanol (50 mL) to produce 32 mL of methyl DL-lactate (methyl 2-hydroxypropanoate) (71.6 % yield, 46.1 % pure). The ester was then hydrolysed with excess water (20 mL) to give 22 mL of purified racemic lactic acid (88.0 % yield, 56.0 % pure). The identity of the synthesised products was confirmed by comparing them against control samples using 1H Quantitative Nuclear Magnetic Resonance (1H QNMR) and ATR-FTIR. Their purity was determined by 1H QNMR, using dimethylformamide as the internal standard. The overall yield of synthesised racemic lactic acid was 43.0 %.Item Optimization of extraction techniques for the isolation and pre-concentration of pharmaceuticals in aquatic environments(2021) Sigonya, Sisonke; Mdluli, Phumlane Selby; Chimuka, LukeThe occurrence of pharmaceuticals in South African aquatic environments has been reported in several studies. However, most of these reports focused on the occurrence of organic compounds in wastewater and surface water. There are very few studies reporting the presence and concentration of these compounds in seawater and coastal areas. Further, most studies have looked at only on one season. This study focussed on the optimisation of a SPE extraction method using Bond Elut Plexa cartridges for the identification and quantification three nonsteroidal anti-inflammatory drugs (NSAIDs), three antiretroviral drugs (ARVs) and a lipid regulator in coastal area of Durban city, South Africa covering four seasons. The optimised SPE conditions were as follows: 500 mL sample volume and at pH 5.8, 5 and 5 mL as conditioning and elution volumes, respectively. The flow rate ranging from 5 to 10 mL/min 10 and 5 mL/min as sample and elution flow rates. The extracted compounds were qualitatively and quantitatively detected by a high-performance liquid phase chromatographic instrument coupled to a photodiode array detector (HPLC-PDA). The recoveries ranged from 62 -102% with RSD values of 0.56 to 4.68% respectively for the determination of emtricitabine, tenofovir, naproxen, diclofenac, ibuprofen, efavirenz, and gemfibrozil. The analytical method was validated by spiking estuarine water samples with 5 µg L-1 of a mixture containing the target pharmaceuticals and the matrix detection limits (MDL) were established to be 0.62- 1.78 µg L-1 for the target compounds. The optimized method was applied to seasonal monitoring of pharmaceuticals at chosen study sites from winter and spring of 2019 and summer and autumn of 2020.The sum of emerging pollutants (ƩEP) were calculated based on each study site. The influent of the Kingsburgh WWTP (EFK) had the highest ƩEP of 144.88 µg L-1 in winter between the two wastewater treatment plants area in this study. The Northern WWTP influent (INN) had a total ƩEP of 117.11 µg L-1 in autumn, the Kingsburgh WWTP effluent (EFK) had a concentration 63.8 µg L-1 in autumn and a concentration 63.8 µg L-1 in summer and the Northern (EFN) had a total ƩEP of 43.97 µg L-1 in winter. A comparison between UMgeni (UR) and Kingsburgh river (KR) showed that the KR had the highest concentration of total ƩEP of 22.66 µg L-1 and UR with the total ƩEP of 18.3 µg L-1 both in winter and spring, respectively. The seawater EPs Blue Lagoon (BL) had the highest ƩEP of 46.75 µg L-1 in spring, subsequently Warner Beach bottom (WBB), Glen Ashley (GA) and Warner Beach top (WBT) with concentrations of 24.96 µg L-1 in summer, 13.29 µg L-1 in spring and 6.94 µg L-1 in autumn, respectively. Estuarine EPs had concentrations of 37.9 µg L-1 and 20.97 µg L-1 for Warner beach estuary (WE) and UMgeni estuary (UE) in winter. WBE having the highest concentration between the two. This showed a significant variation on the presence of these pharmaceuticals in different season.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 Hollow fibre liquid phase microextraction of pharmaceuticals in water and Eichhornia crassipes(2019) Mlunguza, Nomchenge Yamkelani; Madikizela, Lawrence Mzukisi; Chimuka, Luke; Mahlambi, Precious N.This work describes a simple and rapid method for the simultaneous isolation, enrichment, and quantitation of selected pharmaceuticals in aqueous environmental samples and Eichhornia crassipes. This was achieved by developing a hollow fiber liquid phase microextraction (HF-LPME) technique coupled with ultra-high-pressure liquid chromatography-high resolution mass spectrometry for the simultaneous extraction, pre- concentration and quantitation of four non-steroidal anti-inflammatory drugs (NSAIDs) and three antiretroviral drugs (ARVDs) from aqueous matrices and different segments of water hyacinth plant species. The target compounds for NSAIDs were naproxen (NAP), fenoprofen (FENO), diclofenac (DICLO) and ibuprofen (IBU) whereas the selected ARVDs included emtricitabine (FTC), tenofovir disoproxil (TD) and efavirenz (EFV). A multivariate approach by means of a half-fractional factorial design was used to optimize the HF-LPME technique focusing on six factors; donor phase (DP) pH, acceptor phase (AP) pH, extraction time, stirring rate, supported liquid membrane carrier composition (SLM carrier comp.) and salt content. Four of these factors (DP pH, AP pH, stirring rate and extraction time) were identified as vital for an enhanced enrichment of each of the selected NSAIDs and four of the previously mentioned vital factors including the SLM carrier composition were classified as significant for the selected ARVDs from aqueous samples into the hollow fiber. These essential factors were further paired according to their level of significance. The paired significant factors were then optimized using central composite designs (CCD) where empirical quadratic response models were used to visualize the response surface through contour plots, surface plots and optimization plots of the response outputs. The optimized factors for individual analytes belonging to each class were then altered to universal conditions for their simultaneous extraction from same sample solution. The acceptability of the universal conditions was defined using desirability studies. A composite desirability value of 0.7144 was obtained when the optimum factors of the three ARVDs were applied for their simultaneous extraction while a simultaneous extraction of NSAIDs had a desirability value of 0.7735. This implied that the set conditions were ideal for a combined extraction of the target compounds from the donor phase into the acceptor phase across a supported liquid membrane impregnated with a carrier molecule. For the simultaneous extraction of ARVDs, the universal optimum HF- LPME conditions were found to be DP pH of 4, AP HCl conc. of 200 mM (pH = 0.4) with SLM carrier comp. set at 4.5 (%w/w) and stirring at 1000 rpm. Under optimum conditions, the enrichment factors (EF) for ARVDs from aqueous phase were 78 (FTC), 111 (TD) and 24 (EFV). These conditions yielded recoveries in the range of 96 to 111%. The sensitivity of the analytical method through limits of quantification (LOQ) for the selected ARVDs in wastewater samples were 0.033 μg L-1 (FTC), 0.10 μg L-1 (TD) and 0.53 μg L-1 (EFV). The LOQ values were computed for surface water samples using the same target ARVDs were 0.169 μg L-1 (FTC), 0.018 μg L-1 (TD) and 0.113 μg L-1 (EFV). For NSAIDs, the overall conditions were DP pH of 10, AP pH of 3 at an extraction time of 60 min with stirring rate at 1000 rpm. The recoveries yielded under these optimum conditions for the target compounds ranged from 86 to 116%. The EF for the target NSAIDs from aqueous media were 49 (NAP), 126 (FENO), 93 (DICLO) and 156 (IBU). The LOQ values for each target NSAID in wastewater samples were 0.47 μg L-1 (NAP), 0.09 μg L-1 (FENO), 0.59 μg L-1 (DICLO) and 0.49 μg L-1 (IBU). The specific universal conditions were then used in the analysis of ARVDs in wastewater and surface water whereas for NSAIDs analysis, only wastewater samples were analysed. The surface water samples were obtained from North of Johannesburg in Hartbeespoort dam and the wastewater samples were collected from various wastewater treatment plants located in Durban, KwaZulu-Natal. The technique was also applied in the analysis of the target compounds in plant samples obtained from Hartbeespoort dam in North of Johannesburg, Umgeni river located in Springfield (Durban in KwaZulu-Natal) and Mbokodweni river located in south of Durban city, KwaZulu-Natal. The plant samples were first cut and separated into different segments (roots, stems and leaves) and the target analytes then extracted into 20 mL water using an optimized microwave assisted extraction technique (MAE). The HF-LPME technique initially optimized for water samples was then applied for pre-concentration of the target pharmaceuticals from the MAE water extract. Factors that were optimized for MAE technique were irradiation time and temperature for ARVDs whereas irradiation time and solvent volume were optimized for the extraction of NSAIDs. For extraction of both ARVDs and NSAIDs, the optimum irradiation time was 20 min while the irradiation temperature was set at 90 ̊C during the extraction of ARVDs and 100 ̊C for NSAIDs. Generally, the studied ARVDs were all detected in most samples with concentrations for FTC (0.11 – 3.10), TD (0.10 – 0.25) and EFV (1.09 up to 37.3) μg L-1 recorded in wastewater samples. EFV had the highest concentration of 37.3 μg L-1 in the wastewater effluent. The concentration of ARVDs in the roots of the water hyacinth ranged from 7.4 to 29.6 μg kg-1, 0.97 to 11.42 μg kg-1 in the stem and 0.98 to 9.98 μg kg-1 in the leaves of the aquatic plant. Roots of the water hyacinth plant had higher concentrations of the investigated ARVDs. Lastly, the NSAIDs were also detected in various wastewater samples with concentration for NAP (1.15 to 3.30) μg L-1, FENO (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 Solid-phase extraction of selected acidic pharmaceuticals from wastewater using a molecularly imprinted polymer(2017) Zunngu, Silindile Senamile; Mdluli, Phumlane S.; Madikizela, Lawrence Mzukisi; Chimuka, LukeIn this study, molecular modeling was used to investigate the intermolecular interactions between the functional monomer and ketoprofen which is an acidic pharmaceutical that possesses anti-inflammatory and analgesic activities. Ketoprofen is widely employed in medical care for treating musculoskeletal injury. This led to rational design of a molecularly imprinted polymer (MIP) that is selective to ketoprofen. Density functional theory (DFT) at B3LYP/6-31 level was used to investigate the intermolecular interaction between functional monomers and ketoprofen. Binding energy, ΔE, was used as an indication of the strength of the interaction that occurs between functional monomers and ketoprofen. 2-vinylpyridine (2-VP) as one of the functional monomers gave the lowest binding energy when compared to all the functional monomers investigated. Monomer-template interactions were further experimentally investigated using spectroscopic techniques such as Ultraviolet-visible and Fourier transform infrared (FTIR). A selective MIP for ketoprofen was synthesized using 2-vinylpyridine, ethylene glycol dimethacrylate, 1,1’-azobis(cyclohexanecarbonitrile), toluene/acetonitrile (9:1, v/v), and ketoprofen as a functional monomer, cross-linker, initiator, porogenic mixture, and template, respectively. The polymerization was performed at 60 °C for 16 h, and thereafter the temperature was increased to 80 °C for 24 h to achieve a solid monolith polymer. The non-imprinted polymer (NIP) was synthesized in a similar manner with the omission of ketoprofen. Characterization with thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD) showed that the synthesized polymers were thermally stable and amorphous. Morphology of the particles were clearly visible, with MIP showing rough and irregular surface compared to NIP on the scanning electron microscopy (SEM). The characterization of the prominent functional groups on both MIP and NIP were performed using FTIR and nuclear magnetic resonance (NMR). The existence of hydroxyl was observed in the MIP; this was due to the presence of ketoprofen in the cavity. Prominent carbonyl group was an indication of the cross-linker present in both polymers. The synthesized MIP was applied as a selective sorbent in the solid-phase extraction of ketoprofen from the water. The extracted ketoprofen was monitored by high performance liquid chromatography (HPLC) coupled with UV/Vis detector. Several parameters were investigated for maximum recovery of ketoprofen from the spiked deionized water. The optimum method involved the conditioning of 14 mg MIP sorbent with 5 mL of methanol followed by equilibrating with 5 mL of deionized water adjusted to pH 2.5. Thereafter, 50 mL sample (pH 5) was loaded into the cartridge containing MIP sorbent followed by washing and eluting with 1% TEA/H2O and 100% methanol, respectively. Eluted compounds were quantified with HPLC. MIP was more selective to ketoprofen in the presence of other structural related competitors. The analytical method gave detection limits of 0.23, 0.17, and 0.09 mg L-1 in wastewater influent, effluent, and deionized water, respectively. The recovery for the wastewater influent and effluent spiked with 5 µg L-1 of ketoprofen was 68%, whereas 114% was obtained for deionized water. The concentrations of ketoprofen in the influent and effluent samples were in the ranges of 22.5 - 34.0 and 1.14 - 5.33 mg.L-1, respectively. The relative standard deviation (RSD) given as ± values indicates that the developed analytical method for the analysis of ketoprofen in wastewater was rapid, affordable, accurate, precise, sensitive, and selective.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 Analysis of selected organic pollutants in water using various concentration techniques(2014-08-08) Ramphal, Sayjil Rohith; Moodley, Kandasamy Govindsamy; Chetty, Deenadayalan KistenAmong persistent organic pollutants, chlorobenzenes are some of the most frequently encountered compounds in aqueous systems. These compounds can enter the environment via natural and anthropogenic sources, and are ubiquitous due to their extensive use over the past several decades. Several chlorobenzene compounds, once in the environment, can biologically accumulate, and are reputed to be carcinogens and extremely hazardous to health. Several chlorobenzenes are listed as priority pollutants by the United States Environmental Protection Agency. Excessive exposure to these compounds affects the central nervous system, irritates skin and upper respiratory tract, hardens skin and leads to haematological disorders including anaemia. In spite of these harmful effects, chlorobenzenes are still used widely as process solvents and raw materials in the manufacture of pesticides, chlorinated phenols, lubricants, disinfectants, pigments and dyes. In the light of the above, it is imperative to monitor the levels of chlorinated benzenes in all types of surface waters, using low-cost but sensitive methods of preconcentration and detection. In this study, a simple and relatively cheap preconcentration method using direct immersion solid phase microextraction (DI-SPME) followed by gas chromatography equipped with a flame ionisation detector (GC-FID) was developed for the analysis of 7 chlorinated benzenes in dam water. Experimental parameters affecting the extraction efficiency of the selected chlorobenzenes, such as fibre type, sample size, rate of agitation, salting-out effect and extraction time, were optimised and applied to the Grootdraai Dam water samples. The optimised method comprises the use of a 100 µm polydimethylsiloxane (PDMS) fibre coating; 5 ml sample size; 700 revolutions per minute rate of agitation and an extraction time of 30 minutes. The calibration curves were linear with correlation coefficients ranging from 0.9957–0.9995 for a concentration range of 1–100 ng/ml. The respective limits of detection and quantification for each analyte was as follows: 1,3-dichlorobenzene, 0.02 and 0.2 ng/ml; 1,4-dichlorobenzene, 0.04 and 0.4 ng/ml; 1,2-dichlorobenzene, 0.02 and 0.2 ng/ml; 1,2,4-trichlorobenzene, 0.3 and 2.7 ng/ml; 1,2,4,5-tetrachlorobenzene, 0.09 and 0.9 ng/ml; 1,2,3,4-tetrachlorobenzene, 0.07 and 0.7 ng/ml; pentachlorobenzene, 0.07 and 0.7 ng/ml. Recoveries ranged from 83.6–107.2% with relative standard deviation of less than 9%, indicating that the method has good precision, is reliable and free of matrix interferences. Water samples collected from the Grootdraai Dam were analysed using the optimised conditions to assess the potential of the method for trace level screening and quantification of chlorobenzenes. The method proved to be efficient, as 1,3 dichlorobenzene, 1,4-dichlorobenzene and pentachlorobenzene were detected at concentrations of 0.4 ng/ml, 1.7 ng/ml and 1.4 ng/ml, respectively.