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Thesis (MSc)--Stellenbosch University, 2005. / No english abstract available. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van warm water uitloging van houtspaanders by hoë temperature en onder hoë druk voor alkaliese verpulping te ondersoek. Warm water uitloging van houtspaanders onder druk voor alkaliese verpulping was baie belowend, aangesien dit ekstrakstowwe verwyder het wat andersins verteringschemikalieë sou opgebruik het en ook verbertede verpulpingstoestande meegebring het. Gedurende uitloging het die houtstruktuur verander agv die verwydering van die ekstrakstowwe. Dit het veroorsaak dat die houtstruktuur meer toeganglik geword het, en dit het gelei tot 'n verbeterde diffusie van die kookloog. Die versnelde kookloogdiffusie het 'n verbeterde en meer gelykmatige delignifikasie meegebring. Warm water uitloging by verhoogde druk is ondersoek vir drie houtsoorte nl. Eucalyptus grandis, Acacia mearnsii en Pinus patuia. 'n Twee-uur en 'n een-uur uitlogingstyd van die houtspaanders voorafgaande Kraft en soda-AQ verpulping is ondersoek.Vergelyk met 'n een-uur uitloging is daar gevind dat die twee-uur uitloging van die houtspaanders te drasties was, met 'n gevolg van 'n vermindering in pulpopbrengs, vesellengte en pulpsterkte. Die verlaging III pulpsterkte kon toegeskryf word aan polisaggariedafbreking. Die een-uur uitloging het 'n hoër opbrengs opgelewer as beide die kontrole (nie uitgeloogde houspaanders) en die twee-uur uitgeloogde houtspaanders. Die een-uur uitlogingsperiode het besonder goeie verpulpingsresultate vir die ekstrakstofryke Acacia mearnsii houtspaanders getoon, met 'n bykomstige verbetering in pulpsterkte eienskappe.

A Masters dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfillment of the requirements of the degree of Master of Science, January 2018 / Modern developments on nanoparticles (NPs) has led to new innovation in nanoparticles that can be used for the treatment of polluted water. Magnetic NPs are of great interest because of their unique properties and promising applications. Their stability is essential to prevent them from agglomeration, hence, modification with a specific coating layer can assist in the selectivity function and stability of the magnetic NPs. In this work, a magnetic organic nano-adsorbent was synthesized and investigated for the application in the extraction of nitroaromatic explosive compounds from aqueous solutions. The approach was to find a possible synergy between the adsorptive properties of Moringa oleifera and the high surface area of the NPs. The magnetic NPs were utilized for their ferromagnetic properties which assist in the extraction procedure. M. oleifera was used as a natural coating agent to functionalize the magnetic NPs and also to provide stability. There are numerous chemical procedures to synthesize magnetite and one of the simplest and convenient procedures, co-precipitation, was used in this study. Magnetite can be easily oxidized under ambient conditions, hence, in order to prevent oxidation, M. oleifera extracts were used as a coating agent. The synthesized uncoated magnetite NPs and M. oleifera coated magnetite NPs were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), Brunauer, Emmett and Teller (BET) and thermogravimetric analysis (TGA). The M. oleifera leaf extract was obtained using pressurized hot water extraction (PHWE) at 80°C and the seed extract was purchased as a pure oil. Both the M. oleifera leaf and seed extracts were characterized by FTIR and gas chromatography–mass spectrometry (GC-MS) for possible organic compounds assisting in the stability of the magnetite. From the BET results of the coated magnetic NPs at different times, it was observed that with increasing coating time, the surface area decreased while the pore size increased. To optimize the extraction of nitroaromatic explosive compounds (NAECs), the parameters that were investigated were sample pH, contact time, mass of adsorbent and initial concentration. The optimum value for pH of the sample was found at pH8 and for the contact time an optimum of 120 min was found. The mass of M. oleifera coated magnetic NPs for the maximum removal of explosives were found to be 100 mg. The adsorption capacity of the NAECs was obtained in the range of 0.45 and 0.76 mg g-1 at optimum conditions. During kinetic studies it was observed that the pseudo second order model explained the extent of the adsorption mechanism. It was observed that the Langmuir model was favourable as compared to the Freundlich model. The order of selectivity for the NAECs studied was observed as follows: 2-NT ≈ 3-NT > 4NT > NB > 2,6-DNT > 1,3-DNB. The limit of detection (LOD) found was 0.37 – 4.47 and 0.45 – 5.66 ng.mL-1 for extraction using magnetic NPs coated with M. oleifera leaf and seed extract, respectively. The percentage recovery for the extraction of NAECs at optimum conditions was obtained in the range 14 – 46%. / XL2018

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Call number: LD2668 .T4 1948 F75 / Master of Science

Submitted in complete fulfillment for the Degree of Master of Technology: Biotechnology, Durban University of Technology, Durban, South Africa, 2014. / Among 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.

Submitted in fulfillment of the requirements for the degree of Master of Engineering, Durban University of Technology, Durban, South Africa, 2015. / There are various types of separation processes used in industries, such as, distillation, liquid-liquid extraction and gas absorption. Liquid-liquid extraction (LLE) is a separation process that involves mass transfer from a liquid mixture to an immiscible extraction solvent. This process is generally used where the mixture cannot be separated by fractional distillation due to close relative volatilities of the mixture components or for heat sensitive components. LLE is rated as the second most important separation process after distillation and it is widely used in chemical engineering industries. Different types of columns are available for LLE. Reciprocating and vibrating plate extraction columns are mechanically agitated extraction columns. In this research a vibrating plate extraction column was utilised. It uses perforated plates with down-comers. The perforations provide passage for the dispersed phase, while down-comers provide passage for the continuous phase. The effectiveness of a vibrating plate extractor was previously investigated but limited research was conducted on the effect of the different tray designs and agitation levels (as the product of amplitude and frequency of vibration). These variables affect the hydrodynamics and mass transfer in the column. The determination of the optimum process parameters is important in achieving the highest separation efficiency of the vibrating extraction column. The focus of this research is to test the effect of different tray designs in order to enhance the separation process efficiency. All tests were conducted using the toluene-acetone-water system as a standard test system proposed by the European Federation for Chemical Engineering, (1985). The experiments were conducted to test the effect of mass transfer on the hydrodynamics of the system while changing the agitation levels, downcomers and hole diameters. A comparative investigation was conducted on straight segment and circular downcomers, then hole diameters analysis was performed on the effective downcomer Comparison of the effect of the tray design types on the amount of acetone extracted was utilised to select the effective tray. Tray with the circular downcomer and 3.0 mm hole diameter had high dispersed phase holdup values and with the highest percentage amount of acetone extracted (95.05%) was obtained compared to other tray designs investigated.

The equilibrium and the kinetics of the reaction of Mo (VI) with 8-hydroxyquinoline; 8-hydroxyquinaldine; KELEX 100; LIX63; and LIX65N were studied by solvent extraction. From the equilibrium studies it was concluded that in weakly acidic solution (pH 5 to 6) the overall extraction reaction is (UNFORMATTED TABLE FOLLOWS) MoO₄²⁻ + 2H⁺ + 2HL(o) ↔ (K(ex)) MoO₂L ₂(o) + 2H₂O (TABLE ENDS) where HL is the monoprotic bidentate ligand, "(o)" refers to the organic phase, and K(,ex) is the extraction constant. It was concluded that the complexation reaction requires four protons to convert molybdate into molybdenyl. The extractions constants for LIX63 and 8-hydroxyquinaldine, corrected for the side reaction of the ligand and metal, are 10¹⁶·⁴³ and 10¹⁴·⁴⁰, respectively. In the case of LIX65N, the plot of log(D) vs pH has a maximum at pH 1.0, which was explained qualitatively in terms of protonation of the ligand and molybdic acid at low pH. The extraction constant for the reaction of molybdic acid and the neutral ligand was estimated to be 100,000. The kinetics of extraction Mo (VI) with LIX63, 8-hydroxyquinoline, 8-hydroxyquinaldine, and Kelex 100 were studied in this work. In all cases, except 8-hydroxyquinoline, the rate-determining step of the reaction involves the formation of a 1:1 complex between the neutral ligand and several Mo(VI) species differing in the degree of protonation. The rate-determining step for the reaction of Mo(VI) with 8-hydroxyquinoline involves the formation of a 1:2 complex. The rate constant for the reaction of HMoO₄ with 8-hydroxyquinaldine is four orders of magnitude smaller than the corresponding value reported in the literature for 8-hydroxyquinoline. The slower reaction with 8-hydroxyquinaldine was attributed to the presence of the methyl group next to the nitrogen atom of the ligand which hinders its binding with molybdenum in the rate determining step of the reaction.

A comparative study was undertaken of different extraction methods for the isolation of volatile organic compounds from Murraya koenigii (curry leaf plant). The techniques studied included the traditional methods of extraction, namely, Soxhlet and solvent extraction as well as steam distillation. The solvent–free extraction techniques of headspace analysis and headspace solid phase micro-extraction (HS-SPME) were also investigated. In the evaluation of SPME, two different fibre coatings, poly(dimethylsiloxane) and poly(acrylate), were compared. Preliminary work to determine the effect of extraction parameters, such as extraction time, was carried out. The volatile oils in the fresh leaves of Murraya koenigii were isolated by the above-mentioned extraction methods and analysed by gas chromatography-mass spectrometry. The main aroma contributing compounds were identified by comparison of their retention times with those of standards and their mass spectra with those of known compounds contained in the National Institute of Science and Technology Standard Reference Database 1A (NIST 98). The essential oil contained mainly terpenes: monoterpene and sesquiterpene hydrocarbons. The constituents were identified and only the five selected analytes of interest, a-pinene, β-pinene, a-phellandrene, β-caryophyllene and a-caryophyllene were quantified in three of the methods, namely solvent extraction, soxhlet extraction and steam distillation. From the quantitative determination of the compounds of interest, steam distillation favoured the extraction of β-caryophyllene. The solvent and Soxhlet extractions showed no significant differences between the quantities obtained for a- and β- caryophyllene. The steam distillation and Soxhlet methods showed similar quantities of a-caryophyllene extracted. The extraction of the monoterpenes, a-pinene, β-pinene, and a-phellandrene, was favoured by the Soxhlet method of extraction. Quantification was difficult with HS-SPME and headspace analysis. Headspace analysis proved effective in the detection of the very volatile analytes. Headspace-SPME combined with GC-MS was found to be suitable for the identification of both monoterpenes and sesquiterpenes of M. koenigii. From this study, solvent extraction and Soxhlet extraction were found to be superior to the other methods studied for the characterisation and quantitation of the volatile organic compounds in essential oils of Murraya koenigii. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Germanium can be extracted from aqueous solutions by KELEX 100 dissolved in an appropriate diluent. KELEX 100 is a commercially available chelating extractant containing the active constituent 7-(4ethyl-l-methyloctyl)-8-hydroxyquinoline. Previous work in the solvent extraction of germanium with this reagent has shown that germanium is extracted most efficiently at low pH. When the germanium is present in sulphuric acid solutions at pH less than 2, the extracted complex is GeL3+HS04-,however at pH 3 to 8, the metal is extracted as GeL2(OH)2 (where HL = KELEX 100). In this work, the extraction kinetics and equilibrium extraction of germanium in the GeKELEX 100 solvent extraction system is examined by AKUFVE and shaking assemblies, which both employ rapid mixing of the organic and aqueous phases, and by a quiescent interface Lewis Cell. The AKUFVE is a Swedish designed apparatus for solvent extraction, its performance and suitability for solvent extraction studies is evaluated using the extraction experiments carried out on the GeKELEX 100 solvent extraction system. Experiments conducted using an experimental set-up with a large interfacial area to phase volume ratio reveal that the extraction of germanium occurs in two distinct kinetic regimes. The first regime occurs in the first few minutes of an extraction experiment and is fast relative to the second kinetic regime which follows this fast initial extraction period and occurs until the extraction of germanium attains the equilibrium value. In this work an extraction mechanism involving interfacial reaction of germanium and extractant is proposed to explain this kinetic behaviour. An increase in ionic strength is shown to reduce the rate of germanium extraction in the Ge-KELEX 100 solvent extraction system. Modifiers, such as organic alcohols, are shown to greatly improve extraction kinetics. / Thesis (M.Sc.)-University of Natal, Durban, 1990.