Dissertations / Theses on the topic 'Effect of sulphates on'

Froth flotation is a mineral beneficiation process implemented in the recovery of valuable minerals from unwanted gangue material. Copper sulphate is used as an activator in the flotation of base metal sulphides (BMS) as it promotes interaction of collector molecules with the mineral surfaces. It is also used in certain platinum group minerals (PGM) flotation operations in South Africa although the mechanism by which improvements in flotation performance are achieved is not well understood. Some investigations suggest that changes in flotation performance are affected by changes in the froth phase, rather than activation of minerals by true flotation in the pulp zone. The present study focussed on exploring the effect of using copper sulphate as an activator and sodium isobutyl xanthate (SIBX) as a collector on froth stability in Platinum Group Mineral (PGM) operations. This was done on two PGM containing ores namely Merensky and UG2 (Upper Group 2) ores from the Bushveld Complex of South Africa. The dynamic froth stability factor (Σ) and froth half life time (t1/2) were used as measures of froth stability. These were obtained using a froth stability column which is a non-overflowing system. The effect of activation on pure minerals in the pulp phase was also analysed using a microflotation cell which eliminates the froth phase and hydrodynamic interactions found in normal flotation cells. The microflotation cell was used as a measure of hydrophobicity which was directly linked to the flotation recovery. The adsorption of reagents onto the mineral surfaces was confirmed by the use of zeta potential and ethylenediaminetetraacetic acid (EDTA) extraction of surface products. The pulp phase effects were analysed through the floatability of pure minerals and analysis of surface products after copper sulphate activation and these were linked to the outcomes from the froth stability tests. It was hypothesised that copper sulphate destabilised the froth for a Merensky ore and for a UG2 ore but due to different reasons because of the mineralogical compositions of the two ores. For the Merensky ore, the froth destabilisation was postulated to be due to the formation of Cu(I) on the base metal sulphide surfaces which promotes the formation of hydrophobic copper-xanthate species. This would result in an increase in contact angle which promotes bubble coalescence. For the UG2 ore which has far less base metal sulphides than Merensky ore, it was hypothesised that the destabilisation of the froth would be due to the non-selective precipitation of hydrophilic colloidal hydroxides on mineral surfaces which reduce the amount of hydrophobic froth stabilising particles reporting to the froth phase.

The steps involved in plant reductive assimilation of sulphate to sulphide for incorporation into cysteine are not clear. The aim of the project described in this thesis was the isolation of genes encoding sulphate assimilation enzymes which will provide molecular tools for unravelling this key metabolic pathway. Functional complementation of the Escherichia coli cysteine auxotrophic strain JM15 (serine acetyltransferase deficient) using an Arabidopsis thaliana cDNA library in the expression vector YES resulted in the isolation of at least three members of an A. thaliana multigene family encoding serine acetyltransferase. Characterisation of one clone, Sat-1, showed that it conferred serine acetyltransferase activity (with apparent KM for substrates acetyl CoA and L-serine of 0.043 and 3.47 mM, respectively) on strain JM15. The 1515 bp full-length cDNA encodes a deduced protein of 391 amino acids, SAT-1, that has significant identity with bacterial and plant serine acetyltransferases, and that contains a putative N-terminal organellar targeting peptide. Southern hybridisation indicated that Sat-1 is present as a single copy in A. thaliana, while northern analysis revealed a single message of 1.5 kb. Using the A. thaliana cDNA library in the expression vector YES, cDNAs encoding a novel putative "APS reductase" were obtained by functional complementation of E. coli cysteine auxotrophic strains JM81A (adenosine 5'-phosphosulphate [APS] kinase deficient) and JM96 (3'-phosphoadenosine-5'-phosphosulphate [PAPS] reductase deficient). Retransformation of three clones (Papsr-19, Papsr-26 and Papsr-43) encoding different putative APS kinase isoforms into strain JM96 conferred low PAPS reductase activity on the mutant, although this activity was thioredoxin-independent unlike wild-type bacterial activity. The putative APS reductase has a PAPS reductase-like C-terminal domain, but further analysis demonstrated that the enzyme accepts APS in preference to PAPS as substrate and has a thioredoxin-like C-terminal domain. Isolation and characterisation of these genes invites a new hypothesis for plant reductive sulphate assimilation and provides direction for future research.

Traditionally, the extent of sulphate attack is qualified through visual rating as suggested by the Portland Cement Association, or quantified by the percent expansion of slender bars submerged in sulphate solution, the ASTM C 1012 standard. There are no standard methods that take into account the change in engineering properties due to sulphate attack's deleterious mechanisms. Moreover, the exposure regime used to evaluate sulphate attack, complete immersion, is not necessarily representative of that encountered in the field. For these reasons, the objective of this thesis is to quantify the degree of sodium sulphate attack through the degradation of mechanical properties, specifically the compressive and splitting tensile load capacities of standard cylindrical specimens. The research work presented herein also utilizes a novel exposure regime wherein the specimens are only partially submerged in 5% sodium sulphate solution, creating an evaporation front similar to that of field exposure.
Traditionnellement, la méthode par inspection visuelle est suggérée pour qualifier le degré d'une attaque sulfatique du béton. Pour sa part, la norme ASTM C 1012 est régulièrement utilisée dans le cas où le pourcentage d'allongement d'un prisme en mortier submergé dans une solution de sulfate de sodium quantifie la résistance du ciment composant le mortier par rapport aux mécanismes d'expansion. Toutefois, le changement des propriétés d'ingénierie du béton, causé par les effets néfastes de l'attaque sulfatique, n'est pas pris en considération dans les normes existantes. Ainsi, le régime d'exposition aux sulfates de la norme ASTM C 1012, soit l'immersion complète, ne représente pas nécessairement ceux des ouvrages en béton. Pour ces raisons, l'objectif de cette thèse est de quantifier le niveau d'une attaque sulfatique à travers la dégradation des propriétés mécaniques du béton, soient les capacités en compression et tension d'un cylindre standard en béton. De plus, les travaux de recherche incluent un nouveau régime d'exposition afin de recréer un front d'évaporation similaire à celui d'un ouvrage en béton semi-saturé. Comparativement, les spécimens en béton sont submergés jusqu'à leur mi-hauteur dans une solution de sulfate de sodium.

In this work, the nucleation and growth of pores in anodic films formed on aluminium in chromic acid and the effect of low levels of sulphate impurity in the anodizing bath on the formation of the films on aluminium and AA 2024 alloy are investigated. The sulphate concentrations considered include levels within specified limits for industrial processing. The anodizing is carried out either potentiostatically or by stepping the voltage. The films are examined by scanning electron microscopy, transmission electron microscopy and atomic force microscopy to determine the pore spacing, pore population densities, pore diameters and film thicknesses. Film compositions were determined using energy-dispersive X-ray spectroscopy, Rutherford backscattered microscopy and nuclear reaction analysis. In order to investigate the mechanism of pore formation, two tracer methods are employed. In one method, anodic films are formed first in an arsenate electrolyte in the second method, a tungsten tracer band deposited by magnetron sputtering. The behaviours of arsenic and the tungsten are investigated during the subsequent anodizing in chromic acid. The results suggest that the initiation and growth of pores in occurred as a result of electric field assisted chemical dissolution. The effect of sulphate impurity in the chromic acid is investigated using electrolytes with different sulphate content. In the initial stages of anodizing aluminium at 100 V, sulphate impurity at a level of 38 ppm in the chromic acid is shown to lead to significant incorporation of sulphate ions into the anodic film, a lower current density, a smaller cell size and less feathering of the pore walls. In addition, the efficiency of film formation is increased. In later stages of anodizing, the growth of larger pores and cells, leads to a duplex film morphology, with finer pores in the outer region. The change in pore size correlates with a reduction in the incorporation of sulphate into the film. From the results of sequential anodizing experiments, it is suggested that incorporated sulphate ions generate a space charge layer, which has an important role in determining the current density. The effects of higher sulphate concentrations up to 3000 ppm are investigated, which are shown to significantly affect the current density and the pore diameter. Anodizing of aluminium and AA 2024 alloy was also carried out according to industrial practice. The results show that there is significant effect of sulphur impurity on the film thickness. Corrosion tests in 3.5 % NaCl solution for the alloy after anodizing in low (smaller or equal to 1.5 ppm) and high (~38 ppm) sulphate-containing chromic acid electrolytes demonstrate a better corrosion resistance with films formed in the latter electrolyte.

Includes bibliography.
The objectives of this work were to provide rigorous kinetic information on the effects of feed sulphate concentration and temperature on the anaerobic sulphate reduction process and to develop a kinetic model to explain this dependency. These objectives were addressed by performing batch and continuous sulphate reduction experiments using a mixed sulphate reducing microbial culture with acetate as the organic carbon and electron donor source. Sulphate concentration, acetate concentration and biomass concentration was used to determine the metabolic activity of the microorganisms and the rate of sulphate conversion.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2006.
Producing high quality end products, rather than focusing on volume production, is slowly but surely becoming the main driving force in the wood processing industry of South Africa. Drying defects such as surface checks and discolouration by yellow stain and kiln brown stain are major factors in softwood timber downgrades when selecting furniture grade timber. Previous efforts to control these defects have focused on schedule adaptation, but as the industry is still mainly concerned with volume production, and because of the varying lumber price, longer schedules to control these drying defects have not yet been that attractive for the larger sawmills. In ongoing research in this laboratory, a dip treatment of freshly sawn softwood boards in an aqueous solution containing a surfactant called sodium lauryl sulphate (SLS) was used to try to influence the mechanism involved in the development of these stains. Further, complementary research is reported in this study. Firstly, the possibility of using SLS solutions to control surface mould development and bluestain was investigated. Results showed that SLS did control the development of blue stain and mould growth in open-stacked boards for up to three weeks, using concentrations as low as 0.1%, and up to two weeks in closed-stacked timber when using concentrations of 0.2%. Secondly, it was investigated whether SLS treatment would have a detrimental effect on downstream product quality; in particular, kiln dried boards and glued components for furniture manufacturing. Since SLS influenced fluid water flow during kiln drying, the treatment could have exacerbated the occurrence of surface checking due to altered moisture distribution profiles. Results of this investigation showed that the SLS treatment did not result in increased surface checking. Thirdly, as furniture quality timber treated with SLS would be glued, (and also finished with surface coatings), it was further considered important to determine if SLS treatment influenced adhesion properties of wood surfaces. Based on shear test results, it was established that SLS did not influence the adhesion properties of wood when glued with two most commonly used glues in the furniture industry i.e. polyvinyl acetate (PVAc) and urea formaldehyde (UF).

Organisms synthesize stress proteins in response to a variety of stressors. The 68/70-kDa proteins (synonymous to the 72/73-kDa proteins) have shown to be the most promising stress proteins, and have been proposed as a biomarker of general organismal stress. The 68/70-kDa proteins were used in an antigen/antibody based approach to determine the duration of the stress protein response of Pimephales promelas following an acute exposure to copper sulphate.

Biological sulphate reduction (BSR) has been identified as a promising alternative technology for the treatment of acid mine drainage. BSR is a process that uses sulphate reducing bacteria to reduce sulphate to sulphide using substrates as nutrients under anaerobic conditions. The performance of BSR is dependent on several factors including substrate, pH, temperature and hydraulic retention time (HRT). In a quest to find a cost effective technology, Mintek conducted bench-scale tests on BSR that led to the commissioning of a pilot plant at a coal mine in Mpumalanga province, South Africa. This current study forms part of the ongoing tests that are conducted to improve Mintek’s process. The purpose of this study was to investigate the robustness of Mintek’s process and to develop a tool that can be used to predict the process’ performance with varying pH, temperature and HRT. Design Expert version 11.1.2.0 was used to design the experiments using the Box-Behnken design. In the design, pH ranged from 4 to 6, temperature from 10 °C to 30 °C and HRT from 2 d to 7 d with sulphate reduction efficiency, sulphate reduction rate and sulphide production as response variables. Experiments were carried out in water jacketed packed bed reactors that were operated in a down-flow mode. The reactors were packed with woodchips, wood shaving, hay, lucerne straw and cow manure as support for sulphate reducing bacteria (SRB) biofilm. Cow manure and lucerne pellets were used as the main substrates and they were replenished once a week. These reactors mimicked the pilot plant. The data obtained were statistically analysed using response surface methodology. The results showed that pH did not have a significant impact on the responses (p>0.05). Temperature and HRT, on the other hand, greatly impacted the process (p<0.05) and the interaction between these two factors was found to be strong. Sulphate reduction efficiency and sulphate reduction rate decreased by over 60 % with a decrease in temperature 30 °C to 10 °C. Generally, a decrease in sulphide production was observed with a decrease in temperature. Overall, a decrease in HRT resulted in a decline of sulphate reduction efficiency and sulphide production but favoured sulphate reduction rate. This study demonstrated that Mintek’s process can be operated at pH as low as 4 without any significant impact on the performance. This decreases the lime requirements and sludge production during the pre-neutralisation stage by close to 50 %. There was, however, a strong interaction between temperature and HRT which can be used to improve the performance especially during the winter season.
Dissertation (MEng)--University of Pretoria, 2020.
Chemical Engineering
MEng
Unrestricted

The hydrogen embrittlement of two HSLA steels was studied in conditions typical of the marine environment. Double cantilever beam specimens, heat treated to produce the microstructure in the heat affected zone of a weld, were tested in seawater containing sulphate reducing bacteria (SRB) over a range of cathodic protection (CP) potentials and the threshold stress intensities ([Threshold Stress Intensity]) were recorded. The hydrogen concentration absorbed by the steel ([Surface Hydrogen Concentration]) was measured and shown to be higher at more negative CP potentials and significantly increased when SRB were present. An inverse relationship was established between log [Threshold Stress Intensity] and [Surface Hydrogen Concentration]. It was concluded that crack propagation occurs by a single mechanism whether or not SRB are present. Three point bend specimens of both steels were machined from welded plate. Corrosion fatigue tests were carried out in seawater with and without SRB. The presence of active SRB caused increased crack growth rates. Sediment samples were collected from the River Mersey and the base of a North Sea platform. In addition, SRB were added as an inoculum to artificial seawater. SRB numbers were enumerated and their activities assessed by measuring the concentrations of sulphide generated. Hydrogen permeation tests were performed on steel held at a range of CP potentials and exposed to each environment. Measurements were also carried out in seawater containing chemically prepared sulphides. Hydrogen absorption was shown to be enhanced when SRB were present and to be related to the total sulphide (TS) concentration in the environment. High hydrogen concentrations were produced by chemically prepared sulphides and the nature and thickness of the sulphide film appeared to be important in determining the extent of hydrogen absorption. Chemically produced sulphide gave sustained levels of absorbed hydrogen, but those generated biogenically decayed rapidly unless the TS concentration was maintained in the solution.

The alum shale of Sweden is a sulphidic black shale which was mined for its contents of alum during the 17th-19th centuries. During the thirst half of the 20th century alum shale from Kvarntorp was pyrolysed for refinement of its organic matter. The refuse from the pyrolysis process were deposited in a deposit area which is today known as Kvarntorpshögen. This deposit is still hot due to on-going oxidation of the organic matter, pyrite oxidation and the neutralisation of acid by limestone. This heat generation prevents percolation of water to any greater extent due to evaporation. Once it cools the deposit will be susceptible to extraction. Three materials from the Kvarntorp deposit and a block of alum shale were sampled from the Kvarntorp area. These four materials were crushed, sieved and extracted. The extraction experiment was performed at controlled pH which corresponded to dissolution equilibrium of pyrite, carbon dioxide/oxygen, calcite and slaked lime. In the fifth extraction series the material was allowed to set the pH of the water phase. The extraction procedure lasted for 26 days. Metal content of the four shale materials were analysed by XRF (including contents of sulphur, phosphorous and chloride) and by digestion followed by ICP-MS analysis. Mineralogy of the four materials and the extraction residues were studied by XRD analysis. Metal concentrations of the aqueous samples were analysed by ICP-MS and concentrations of dissolved organic- and inorganic carbon by TOC. Electrical conductivity and concentrations of sulphate was also analysed in aqueous phases with non-manipulated pH. Sulphate and calcium concentrations were highest in aqueous samples from weathered fines indicating the presence of gypsum. Presence of gypsum was also confirmed by XRD. Gypsum indicates weathering since it is a neutralisation product of calcite and the sulphuric acid generated by pyrite oxidation. Concentrations of dissolved organic carbon in samples with pH 12.5 were found to be highest from red processed shale and lowest from samples of shale. This indicates different hydrolysis properties or origin of the organic matter in the materials. The majority of analysed metals had highest solid solution distribution under acidic, i.e. pH 3.0, conditions. Under these conditions it was samples from the relatively non-weathered shale that had the highest release of metals, with a few exceptions. At pH 12.5 high concentrations of V, As and Mo was extracted from almost all four materials. The red processed shale released the highest percentages of its total contents of V, As and Mo under these conditions; 28 %, 55 % and 61 % respectively. The high release of V, As and Mo from red processed shale was most likely a result from the pyrolysis process. The roasting induced the formation of oxides which then easily forms vanadate, arsenate and molybdate when exposed to water. Water percolating the Kvarntorp deposit in the future will initially most likely have a near neutral or slightly acidic pH. Lowest concentrations of metals were found in aqueous samples with pH between 5.5-8.5. There is a great risk that the pH of the drainage from the Kvarntorp deposit will in time become acidic due to depletion of buffering capacity. Thus the environmental threat will increase.

The theme of this thesis is the high-temperature phase studies of inorganic metal sulphates and the aspects specifically dealt with are phase diagrams and drop calorimetry. Chapters 1,2, and 3 are concerned with the first of these. Chapter 1 briefly describes the features encountered in one and two-component systems and provides the thermodynamic background which allows such systems to be calculated. Chapter 2 describes a selection of experimental techniques used to determine phase diagrams. Apparatus to perform Differential Thermal Analysis (DTA) was constructed as part of the work of this thesis and so this technique is fully described, including details of the apparatus, and a section on interpretation of DTA results relating to phase studies. Pointers are included as to further applications of this technique and improvements or modifications that might be made to the present apparatus. Chapter 3 presents the phase diagram of the previously undetermined system Ag2SO4-LA2(SO4)3 and also includes some observations on the kinetics of some phase changes and a description of the optical furnace which was built to study them. Also presented is a re-investigation of the system Ag2SO4-CdSO4, which contains many features not evident in an earlier study. Chapter 4 is concerned with the thermodynamics of substances at high-temperatures and describes in detail the design, construction and experimental procedure for a drop calorimeter. This apparatus allows the equilibrium temperature of high-temperature polymorphic phase transitions and their enthalpies of transition to be determined. A preliminary study on CdSO4 was performed, which ties in with the study in Chapter 3, and an attempt was made to resolve the long standing controversy on the temperatures of the CdSO4 phase transitions. Drop Calorimetry can provide some of the data necessary for the calculation of phase diagrams as described in Chapter 1, and so a brief introduction to the thermodynamics of non-reacting systems and the treatment of results is presented.

Three artificial stream designs, termed Large Artificial Stream Units (LASUs), Raceways, and Channels, at two major scales (1700 L, 12.5 L and 20 L recirculated volume) were developed at the Institute for Water Research, Rhodes University, Grahamstown, in order to explore the possibilities of using indigenous rheophilic macroinvertebrates in routine toxicity tests. This study compared these systems, using 96h-EC50 values from sodium sulphate toxicity tests as the experimental response. Two local Ephemeroptera (Leptophlebiidae: Adenophlebia auriculata Eaton, and Baetidae: Afroptilum sudafricanum Lestage) were evaluated for their suitability in routine toxicity tests; and the possible effects of elevated salinity levels in South African rivers on the test species were assessed. Two sets of experiments with each mayfly species were conducted, following an unreplicated regression design. Dechlorinated tap water was used as the water source. Experiments in the Channels were repeated to determine experimental variability. Results were compared statistically by testing for overlap of 95% confidence limits (95%Cls) of EC50 values. The differences between A. auriculata EC50 values in the different systems were statistically significant (no overlap of 95%CLs), but they were not more variable than has been considered normal for biological systems (Coefficient of variation 20.1 %; ratio of greatest EC50 / smallest EC50 1.63). The differences were not related to the scale or the average current velocity characteristic of each stream design (average current velocity LASUs - Raceways - Channels 0.090 - 0.083 - 0.038 m/s). The Channels proved to be most efficient with regard to practical performance as they are portable and easily transportable, user-friendly, reliable, splash-free, cost effective to construct, and can easily be adapted to specific requirements. These systems are therefore recommended for regular use. The suitability of the two mayfly species for routine toxicity testing was evaluated. A. auriculata EC50 values showed a significant negative correlation with the corresponding average body-size (range 1476 - 1610 μm, mean 1555 μm). The different average body-sizes probably reflected the abundance of a certain size range present in the Palmiet River at the time of collection. Both species reacted similarly to Na₂S0₄ (similar slopes of the toxicity curves), identifying this salt as a slow acting toxicant. A. sudafricanum populations were more sensitive to Na₂S0₄ (EC50 3.404 g/L) than A. auriculata (EC50 8.090 g/L), probably because of its smaller body-size (mean 709 μm) and a lack of extremely tolerant individuals. In comparison to other freshwater macro invertebrates, including the standard toxicity test organism Daphnia spp., both mayfly species seemed to be moderately tolerant of Na₂S0₄; therefore there was no particular advantage to using these indigenous taxa rather than Daphnia spp. An assessment of the effects of elevated salinity/TDS levels on the test taxa yielded preliminary insights. A NaCI-EC50 for A. sudafricanum could be extrapolated and suggested a higher sensitivity to Na₂S0₄ than to NaCl. When Na₂S0₄ EC50 values of both species were compared to selected TDS levels of South African rivers, 4. auriculata would mostly not be affected, but A. sudafricanum might occasionally suffer from sub-lethal effects, depending on the sulphate proportion of the TDS. The South African guideline for TDS seemed to protect both species sufficiently.

La modelisation du comportement des actinides dans l'environnement necessite l'acquisition de donnees structurales et thermodynamiques sur les especes susceptibles d'etre presentes dans les milieux naturels. Le protactinium est un element possedant une tendance tres marquee vis–à–vis de l'hydrolyse, de la polymerisation et de la sorption sur tout support solide. Dans ce cas, la determination des constantes d'equilibre relatives a des especes monomeres ne peut etre effectuee qu'a l'echelle des traces (CPa < 10-10M) avec l'isotope 233Pa. Les constantes de complexation de Pa(V) avec les ions sulfate ont donc ete determinees a partir d'une etude systematique des variations du coefficient de partage de Pa(V) dans le systeme TTA/toluene/H2O/Na2SO4/HClO4/NaClO4, en fonction de differents parametres tels que les concentrations de sulfate et de protons libres, la force ionique, la temperature, et la concentration de l'extractant. Compte tenu de l'interdependance des especes en phase aqueuse, il a ete necessaire de developper un code de calcul iteratif prenant en compte les reactions de dissociation de HSO4- et de formation de NaSO4- , mais egalement l'influence de la temperature et de la force ionique. Pour chaque valeur de µ et de temperature, et pour une concentration de proton libre fixee, le programme permet de calculer l'ensemble des concentrations des especes libres en solution. Les donnees de sortie sont les volumes de solutions meres de NaClO4, HClO4 et Na2SO4 a introduire pour realiser les solutions retenues. La mesure directe de la quantite de 233Pa en phase organique et aqueuse, par spectrometrie gamma, nous a permis de calculer le coefficient de partage (D) en fonction de la concentration des ions libres SO42-. Les experiences, effectuees en changeant differents parametres, montrent une forte dependance de D avec : la temperature, la concentration de la tta, la concentration des ions libres H+ et la concentration des ions sulfate libres. Les constantes de complexation ont ete determinees à l'aide d'un traitement mathematique des donnees de partage. L'extrapolation de ces constantes à force ionique nulle a ete realisee en utilisant le modele sit pour differentes valeurs de temperature. Parallelement, une etude structurale de Pa(V) en milieu sulfurique (13 et 4 M) et en milieu fluorhydrique (HF 0, 5 et 0, 05 M) a ete realisee avec l'isotope 231Pa. Les spectres exafs et xanes ont montre l'absence de liaison Pa = O dans le cas du milieu fluorhydrique. En milieu sulfurique une seule liaison oxo a ete mise en evidence, ce qui differe des actinides V et VI qui conservent toujours leur liaison trans-dioxo.

A guinea pig model of dextran sulphate-induced colitis was developed to investigate nutritional strategies in improving gastrointestinal inflammation. The present study aimed to determine if a diet rich in docosahexaenoic acid (DHA) improves clinical and physical symptoms of inflammatory bowel disease (IBD) and whether DHA alters inflammatory lipid mediator production, and subsequent systemic effects on the acute phase response (APR). DHA improved symptoms of IBD, including; fecal blood, diarrhea, lethargy, survival, and dietary intake. Feeding of DHA increased the percent of DHA in livers (1.2% vs 0.3%), tended to decrease inflammatory mediator production, but did not decrease intestinal damage or alter protein kinetics. These results demonstrate that DHA improves clinical and physical symptoms associated with IBD, possibly involving decreased lipid mediator production. The mechanism of action does not appear to involve a blunting of the APR nor decreases in intestinal damage.
Un modèle de cochon-dinde injecté de dextran sulfate colite a été développé pour investiguer les stratégies nutritionnelles afin d'amenuiser les symptômes d'inflammation gastro-intestinale (IBD). La présente étude visait à déterminer si une diète riche en acide docosahexaenoic (DHA) améliore les symptômes cliniques ainsi que physiques de la maladie inflammatoire de l'intestin, si le DHA altère la production de lipides inflammatoires médiateurs et, les effets systémiques subséquents sur la phase de réponse aigue (APR). Le DHA à amélioré les symptômes de l'IBD, incluant; sang fécal, diarrhée, léthargie, survie et l'apport diététique. L'apport de DHA à augmenté le pourcentage de DHA dans le foie (1.2% vs 0.3%), à tendu à diminuer la production de médiateur d'inflammation mais n'a pas diminué le dommage intestinal ou altéré la cinétique des protéines. Ces résultats démontrent que le DHA améliore les symptômes cliniques et physiques associés avec l'IBD, possiblement à travers la diminution la production de lipides médiateurs. La mécanique ne semble pas provoquer un émoussement de l'APR ou diminuer le dommage intestinal.

Sulphate-rich wastewater is an increasing concern for industries as LKAB. The water chemistry of the LKAB Kiruna water system is characterized by high alkalinity, high pH (pH 7.5-9.0) and high concentrations of chemical species and soluble minerals. The sulphate content in the water system of Kiruna is associated with the dissolution of calcium sulphate as anhydrite (CaSO4) and gypsum (CaSO4 2H2O). However, the high concentrations of sulphate in the effluents from the LKAB Kiruna operation are unique for iron ore mining.    The aim of the thesis was to study and evaluate the behavior of sulphate in the process water system of the Kiruna concentrator plants. This was done by laboratory grinding (leaching tests), equilibrium calculations with the HSC software and mass balancing of the concentrator KA3 in Kiruna. The highest concentrations of sulphate have been detected in the process water of KA3, hence the focus has been on KA3 regarding sampling, evaluation and comparison. Water treatment technologies for sulphate and the effect of process water on ore processing have not been included in this project.   The laboratory grinding was done using process water and ore from the concentrator KA3. During the experimental work with laboratory grinding the parameters pH, temperature and operating times for primary- and secondary grinding, respectively, were varied. The observations from the experimental work were further confirmed by equilibrium calculations and mass balancing. The following conclusions were drawn.     Anhydrite/gypsum is not leached from the ore during ore processing with process water having concentrations of sulphate already close to the saturation point at approximately 1800 mg/L. If the process water is diluted with water with lower sulphate content, e.g. mine water or a diluted return water from the pond system (e.g. during spring flood), anhydrite/gypsum in ore will be dissolved until the sulphate concentration reaches the saturation point. The ionic strength of the process water controls the saturation point and thus the sulphate concentration. Leaching of anhydrite/gypsum in saturated process water, with respect to sulphate, is not affected by grinding time or adjusted conditions in the process water, such as temperature or pH value.    For further work, it is recommended to investigate the behavior of sulphate in the tailings pond system to increase knowledge of the overall behavior in the water system. In addition, a similar investigation of the behavior of uranium in the process water is recommended in order to face future environmental standards.

The coal industry of Mpumalanga Province is faced with the problem of developing cost effective ways of using large volumes of calcium and magnesium sulphate enriched waste waters. Use of the waste waters for agricultural production may contribute as a stabilising factor with regard to yields in this high potential agricultural area. The objectives of this study were to determine the effect of such waste waters on yield and to compare crop response to calcium and magnesium sulphate salinity at different nutrient levels. Two separate glasshouse experiments were conducted. Wheat (Triticum aestivum L. cv. SST 825) was grown in calcium and magnesium sulphate salinised nutrient solutions (Ca:Mg 2: 1) with differential levels of NO3, NH4, P and K. A soil pot experiment was subsequently conducted with maize (Zea mays, cv. PAN 6256), three gypsum and magnesium sulphate salinity levels and a 6 x 2 x 3 factorial combination of N, P and K. Calcium and magnesium sulphate salinity decreased the biomass production of both crops. This was mainly due to interactions of Mg with the uptake of essential nutrients in wheat and a Mg toxicity andlor Ca deficiency induced by high levels of Mg andlor SO4 in maize. The application of NO3, NH4, and K at rates different from the level considered beneficial for non-saline conditions improved wheat growth under sulphate saline conditions. Strongly inhibitory salinity levels controlled the maize yield of the highest salinity treatment regardless of the level of fertiliser application. A beneficial effect of higher NH4 supply was observed in both experiments. This can be ascribed to the antagonistic effect that NH4 exerted on Mg concentrations in plants (both experiments) and SO4 (soil pot experiment) and/or to a higher N-utilization efficiency where N was supplied as NH4 compared to NO3. Differential application levels of P had no effect on the yield of wheat. Phosphorus concentrations in maize were marginal to low, even at extremely high soil Bray I-P levels. This was probably caused by the precipitation of P as insoluble calcium phosphate complexes in the soil andlor between the free space of the cortex cells of plant roots. These results could also indicate that the Bray I extraction method does not give a true reflection of plant available P in sulphate saline soil. Further experimentation is needed to verify these results under field conditions and determine the optimal rate, method and timing of especially NH4 and PO4 fertilisers when irrigating crops with these calcium and magnesium sulphate enriched waste waters.
Dissertation (MSc (Plant Production and Soil Science))--University of Pretoria, 2007.
Plant Production and Soil Science
unrestricted

This study evaluated SO4 2- removal from circumneutral mine water (CMW) collected from Middleburg coal mine using coal FA collected from Hendrina power station. The following parameters were investigated: the effect of the amount of FA, the effect of the final pH achieved during treatment, the effect of the initial pH of the mine water and the effect of Fe and Al on SO4 2- removal from mine water. The precipitation of ettringite at alkaline pH was evaluated to further reduce the SO4 2- concentration to below the DWAF limit for potable water. Removal of SO4 2- from mine water was found to be dependent on: the final pH achieved during treatment, the amount of FA used to treat the mine water and the presence of Fe and Al in the mine water. Treatment of CMW using different CMW:FA ratios
5:1, 4:1, 3:1, and 2:1 resulted in 55, 60, 70 and 71 % SO4 2- removal respectively. Treatment of CMW to pH 8.98, 9.88, 10.21, 10.96, 11.77 and 12.35 resulted in 6, 19, 37, 45, 63 and 71 % SO4 2- removal respectively. When the CMW was modified by adding Fe and Al by mixing with Navigation coal mine AMD and treated to pH 10, 93 % SO4 2- removal was observed. Further studies were done to evaluate the effects of Fe and Al separately. Treatment of simulated Fe containing AMD (Fe-AMD) to pH 9.54, 10.2, 11.8, and 12.1 resulted in 47, 52, 65, and 68 % SO4 2- removal respectively. When Al containing AMD was treated to pH 9.46, 10.3, 11.5 and 12 percentage SO4 2- removal of 39, 51, 55 and 67 % was observed respectively.

The fate and behaviour of estrogens in the environment are of concern due to the compounds’ endocrine disruption potential. Estrogens, namely 17β-estradiol (E2), estrone (E1), and estrogen sulphates, i.e. 17β-estradiol-3-sulphate (E2-3S) and estrone-3-sulphate (E1-3S) excreted by livestock constitute a potential source for estrogen contamination in the environment. A method was developed to separate and quantify the hormones by high-performance-liquid-chromatography (HPLC) and ultraviolet detection (UV). A combination of dichloromethane (DCM) and dicyclohexylamine hydrochloride (DCH·HCl) gave recoveries from 97.3 to 107% for E1-3S extraction from aqueous solutions. The recoveries from soil samples ranged from 80.9 to 95.2% (E2-3S), and from 86.3 to 91.7% (E1-3S), respectively. Results of batch sorption studies showed that Freundlich isotherms were nonlinear (N ≠ 1) with Kf values ranging from 34.2 to 57.2, and from 3.42 to 4.18 mg¹-N LN kg⁻¹ for E1, and E1-3S, respectively, indicating the sorption affinity of E1-3S was about an order of magnitude lower than that of E1. The hydrophilic sulphate group of E1-3S possibly shielded the compound from hydrophobic interactions with the soil organic matter and allophanic clay minerals that were proposed as sorbents for E1. Contraction of clay minerals, “salting out” and competitive sorption of artificial urine constituents were likely to have been responsible for observed changes in Freundlich parameters when artificial urine was used as mediator matrix. Plotting the effective distribution coefficient as a function of hypothetical exposure concentrations facilitated the comparison of the sorption behaviour of both compounds as influenced by the mediator solution. The results emphasized that using the CaCl₂ matrix might result in false inferences for the sorption behaviour of these compounds in a dairying environment. The four hormones rapidly degraded in the agricultural soils under aerobic conditions, and the majority of the compounds degraded > 50% within the first 24 hrs. Soil arylsulphatase activities were directly correlated with degradation rate constants of the estrogen sulphates. Estrone was identified as a metabolite of E2 and E1-3S, and these three compounds were observed as metabolites of E2-3S. Single-first order (SFO) and double first-order in parallel (DFOP) kinetics were used to model the degradation and metabolite formation data. The results showed that the DFOP model was in most cases better able to predict the parent compound degradation than the SFO model, and also enabled to estimate accurate degradation endpoints. ER-CALUX® analysis revealed the formation of estrogenicity during E2-3S degradation, which could partly be explained by the formation of the metabolites E2 and E1. Transport studies with E1-3S and E1 showed that the transport and retention of both compounds were significantly influenced by the mediator matrix. While no breakthrough curves (BTCs) were recorded during hormone application in CaCl₂ (10 mM) both hormones were detected in the leachate when applied in artificial urine. Rate-limited sorption processes were proposed for the delayed arrival of the hormone BTCs compared with a conservative bromide tracer. Intense colouration of the leachate during the artificial urine experiments suggested the hormones were likely to be moved by colloid-facilitated transport. Furthermore, the detection of residue hormone and metabolite concentrations implied that degradation of E1-3S and E1 was hampered by urine constituents such as glycine and urea.

Luminescence measurements have been applied to three different structures namely, sulphate, fluorides and YAG. In all cases the RE doping suppresses the intrinsic emission and results in intense luminescence characteristic of the RE dopant. Additionally, in double doped samples, or contaminated ones, the TL data show that each dopant defines a glow peak, which is displaced in temperature relative to the others. Examples of this were discussed for CaS04:Ce,Mn; YAG:Nd,Tb,Cr,Mn; BaF2:Ho,Ce and BaF2:Tm,Ce. The data are discussed in terms of an energy transfer model between different parts of extended defect complexes which encompass the RE ion and the lattice defects. Calcium sulphate doped with Dy define a TL peak near 200°C suitable for radiation measurements, but when co-doped with Ag the TL peak move to higher temperatures with minor effects on the peak sensitivity. In Ce,Mn double doped samples, the peak temperatures differ by -7°C between the Ce and Mn sites. The TL glow curves from alkaline earth fluorides are complex and contain several overlapping peaks. Curve fitting show that the peak maxima below room temperature are insensitive to the RE dopant. Additionally the host material has a modest effect on the peak positions. Above room temperature each dopant provides a TL curve specific to the added RE ion and do not show common peaks. Concentration has many effects on the resultant glow curve, and even at the lowest concentration used here (0.01%) there is evidence of cluster formation. Samples with high RE content show low values of the frequency factor consistent with the energy transfer model in that the emission from RE-RE cluster dominates over the emission from direct charge recombination within the defect complex. The effect of concentration and the TL mechanism operating below room temperature are also discussed. Luminescence signals from the near surface of YAG:Nd (via CL) were contrasted with those from the bulk material via RL. Results indicate that the outer few micron layers differ significantly in luminescence response from the bulk crystal. The differences were ascribed to result from solvents that enter the YAG lattice during the growth stage or subsequently from cleaning treatments via the dislocations caused by cutting and polishing. Additionally, the growth stage may include gases from the residual air in the growth furnace trapped into the YAG lattice. In each case there is a discontinuity in luminescence intensity and/or emission wavelengths at temperatures which mach the phase transitions of the contaminants. At the transition temperature there will be a sudden pressure change and this will induce surface expansion or bulk compression. The differences between the two cases were detected by the alternatives of CL and RL excitation, where the Nd or Er lines have moved in opposite directions. The detection of such low concentrations of solvents/trapped gases by luminescence is extremely difficult due to experimental limitations. Hence their role in luminescence generation is normally ignored.

Peripheral neuropathies (PN) represent a significant health burden, due to chronic and debilitating symptoms, that can be inherited or caused by everything from alcohol,chemotherapy and diabetes. PN are associated with both demyelination and axon degeneration, which play a fundamental role in their pathogenesis. The aim of this thesis is to identify novel mechanisms and/or potential therapeutics for protecting axon degeneration and promoting myelination. This is significant because there are currently no specific therapeutics, for PN, that have passed clinical trial successfully. Recent work in the Barnett lab has implicated heparan sulphate proteoglycans (HSPGs), as therapeutic targets in central nervous system (CNS) injury. HSPGs are able to bind a plethora of proteins, including chemokines and growth factors, where they facilitate binding to their corresponding receptors. We therefore hypothesised that HSPGs may have a regulatory role in PNS injury. To address this I data mined previously published microarrays for sciatic nerve (SN) injury. This principally identified the candidate heparanase (Hpse),which was up-regulated after injury in several different microarray analyses. Hpse is able to regulate HSPG signalling and is already implicated in several diseases including: cancer, diabetes and Alzheimer’s disease, making it an interesting candidate for further research. In order to question the role of Hpse in PNS injury we used two models of Wallerian degeneration:ex vivo SN injury model and an ex vivo neuromuscular junction (NMJ) injury model. Inhibiting Hpse acutely accelerated axon loss, while its exogenous treatment was protective. Furthermore we found that Hpse can regulate β-catenin protein levels and the transcription of genes, predicted to be regulated by β-catenin. This included Sox2, which led to an acceleration in Schwann cell dedifferentiation after in-jury. Recent evidence has linked Schwann cell dedifferentiation to early events in axon fragmentation. We also found that heparin sulphate mimetics significantly promote in vitro myelination, the mechanism for which requires further research. In conclusion, we have identified Hpse, an up-regulated enzyme after SN injury, in protecting axon loss during SN degeneration. Within the field, Wallerian degeneration is considered a useful model for studying the mechanisms behind axon loss in peripheral neuropathies, for which the role of Hpse warrants further investigation as a potential therapeutic target. Lastly we also identified heparin sulphate mimetics in promoting peripheral myelination, also making them potential therapeutic targets.

Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: When desalinating brackish water by reverse osmosis (RO) or other techniques, high overall water recoveries are essential to minimize brine production and the associated disposal costs thereof. As the overall water recovery increases, concentrations of sparingly soluble salts (e.g. barium sulphate, calcium sulphate) reach levels above saturation, especially near the membrane surface, drastically increasing the scaling propensity. Antiscalants are typically dosed into the feed water to prevent such scaling during RO desalination. However, the carry-over of antiscalant into the concentrate stream can complicate subsequent salt precipitation processes that may be used to increase overall water recovery. These precipitation techniques are sometimes used to reduce the levels of super-saturation in the RO concentrate prior to a subsequent RO desalination step. The purpose of this study was to assess the feasibility of reducing calcium sulphate scaling on RO membranes, by using periodic permeate flushing when feeding a lab-scale RO unit with a supersaturated calcium sulphate solution in the absence of anti-scalant. The overall water recovery was increased by recycling the concentrate, after an intermediate de-supersaturation step. This simulated a multiple-stage RO system, typical of processes used in high-recovery acid mine drainage (AMD) treatment plants. De-supersaturation of the concentrate intermediate was achieved with direct seeded gypsum precipitation, in the absence of any antiscalant. On the membrane surface inside the membrane unit, calcium sulphate concentrations greatly exceeded saturation levels – a combined consequence of the normal concentration process and the well-known surface-based concentration polarisation phenomenon. Therefore, periodic forward-flushing of the supersaturated solution from the membrane unit was performed with permeate. In theory, the periodic flushing removes the highly concentrated layer at the membrane surface during every flush, before scaling can occur. Various flushing regimes were evaluated to assess the effectiveness of the process. A lab-scale desalination unit with a 0.106 m2 flat sheet polyamide RO membrane was designed and constructed. The unit could operate at a feed rate of 12-14 L/h and at permeate fluxes of 12-24 LMH. Super-saturated feed solutions were prepared by mixing sodium sulphate and calcium chloride dihydrate salts with demineralised water, with an initial salinity of ± 5300 mg/L TDS, corresponding to a gypsum saturation index (SIg) of 1.2 for most experiments. The total production time, net permeate production and flux decline were used to compare the flushing efficiency in different experimental runs. Initial tests showed that scaling could be prevented (when operating the unit in full recycle mode, i.e. where both concentrate and permeate were recycled to feed), at flushing frequencies between 12 and 2.4 h-1, when the membrane feed and concentrate were slightly under-saturated (SIg = 0.9) and slightly super-saturated (SIg = 1.1) respectively. However, when switching the same system to non-flushing mode after 24 hours of operation, membrane scaling occurred within 2-3 hours, as indicated by a strong decline in flux. However, when operating the system in concentrate recycle mode (i.e. permeate is withdrawn) with super-saturated feed solutions (e.g. SIg = 1.2), and thus a notably more super-saturated solution in the membrane concentrate, scaling could not be prevented (albeit delayed for some time) with intermittent permeate flushing. A fractional 25-1 factorial design was used to determine which factors had the most significant effect on total production time and permeate production rate, testing five factors: 1) flushing frequency, 2) flushing volume, 3) permeate soak time, 4) permeate flux and 5) instantaneous recovery. The ANOVA analysis showed that total production times were, not surprisingly, primarily affected by the permeate flux, where operation at 24 LMH resulted in a lower net permeate production between 3.0 - 4.2 L, compared to 7.6 - 9.7 L at 12 LMH. Higher permeate fluxes clearly resulted in higher levels of concentration polarisation at the membrane surface, thus increasing the propensity for membrane scaling. Flushing frequency and instantaneous recovery also affected the net permeate production, where 6 h-1 and 10 % were the optimal values respectively within the range of test conditions. The lowest permeate production rate resulted in the highest net permeate volume production (i.e. also longest total production time), confirmed by a least squares regression. In summary: This study showed that periodic permeate flushing could delay the membrane scaling process. However, it failed to prevent membrane scaling completely when operating the system with supersaturated calcium sulphate solutions in the absence of antiscalants. The flushing technique effectively delayed the onset of precipitation, but scaling eventually occurred if the lab-scale RO system was operated in concentrate recycle mode with oversaturated feed solutions (SIg = 1.2). Additional experiments at different cross-flow velocities during permeate flushing, while using an optimised RO test cell flow channel design, are recommended for future studies.
AFRIKAANSE OPSOMMING: Gedurende die ontsouting van brakwater deur tegnieke soos tru-osmose (TO), is ʼn maksimum herwinning van water noodsaaklik om die produksie, en die gepaardgaande kostes van verwydering, van die sout/brak neweproduk te minimeer. Soos die herwinning van water verhoog, so ook verhoog die konsentrasie van moeilik-oplosbare soute (soos bariumsulfaat, kalsiumsulfaat) in die sout konsentraat stroom, totdat die soute uiteindelik superversadiging bereik. Hierdie superversadiging gebeur veral naby die membraanoppervlak, waar dit lei tot ʼn verhoogde kans van presipitasie en skaalvorming. Om dit te voorkom word die voerwater na ʼn TO stelsel tipies gedoseer met antiskaalmiddels. Hierdie antiskaalmiddels verlaat die stelsel saam met die konsentraat, waar hulle gevolglike die presipitasie van soute bemoeilik. Presipitasie van soute uit die konsentraat kan tipies gebruik word om die vlak van superversadiging in die konsentraat te verlaag, waarna verdere TO behandeling gebruik word om selfs ʼn hoër algehele waterherwinning te bewerkstellig. Die doel van hierdie studie was om die vatbaarheid van die vermindering van kalsiumsulfaat (gips) skaalvorming in die afwesigheid van antiskaalmiddels op TO membrane te toets. Dit is bewerkstellig deur ʼn laboratoriumskaal TO eenheid te voer met ʼn superversadigde kalsiumsulfaat oplossing en die membraan periodies met skoon produkwater (permeaat) te was. Die algehele waterherwinning is verhoog deur met ʼn tussenstap die versadigingsvlak van gips in die konsentraat te verlaag, waarna dit hersirkuleer is na die voertenk. Sodoende is ʼn multi-stadium TO stelsel nageboots, soos dit tipies in hoë herwinningsaanlegte, soos met die herwinning van suur mynwater (E: acid mine drainage, AMD), gebruik word. ʼn Verlaging in superversadiging van die konsentraat in die tussenstap is behaal deur die konsentraat direk aan gipskristalle bloot te stel om presipitasie te bewerkstellig in die afwesigheid van enige antiskaalmiddels. Gedurende eksperimente het die soutkonsentrasie op die membraanoppervlak in die TO eenheid superversadigingsvlakke vêr oorskry, as gevolg van die natuurlike konsentrasie proses en die bekende konsentrasie polarisasie oppervlaksverskynsel. Om hierdie superversadiging teen te werk is periodiese saamstroom spoeling van die membraan met skoon produkwater uitgevoer. In teorie het die periodiese spoeling die hoogs gekonsentreerde oplossing van die membraan oppervlak verwyder voor skaalvorming kan plaasvind. Verskillende spoelpatrone is ondersoek om die doeltreffendheid van die spoeling te bepaal. Om die eksperimente uit te voer is ʼn laboratoriumskaal ontsoutingsaanleg met ʼn maklik verwyderbare 0.106 m2 plat-vel poli-amied TO membraan ontwerp en gebou. Die aanleg kan vloeistof voertempo’s tussen 12-24 L/h hanteer en skoon produkwater teen 12-24 LHM lewer. Die superversadigde voer oplossings, soos gebruik in die meerderheid van die eksperimentes is voorberei deur natriumsulfaat en kalsiumchloried-dihidraat soute te meng in gedemineraliseerde water, tot ʼn soutgehalte van ± 5300 mg/L TDS bereik is. Hierdie soutgehalte stem ooreen met ʼn gips versadigingsindeks (E: gypsum saturation index, SIg) van 1.2. Die skoon produkwater totale produksietyd en netto produksie, asook die membraan vloed afname, is gebruik as veranderlikes om die spoel doeltreffendheid tussen eksperimentele lopies te vergelyk. Aanvanklike toetse het getoon dat skalering voorkom is by effens onderversadigde (SIg = 0.9) en effens superversadigde (SIg = 1.1) voer oplossings met die onderskeie spoel frekwensies van 12 en 2.4 h-1, (terwyl die aanleg in algehele hersirkulasie bedryf is, m.a.w. wanneer beide die konsentraat en produkwater gedurig na die voertenk hersirkuleer word). ʼn Effens-superversadigde eksperiment is ook sonder spoeling uitgevoer vir 24 uur. In hierdie geval het skaalvorming binne twee tot drie uur gebeur, soos bevestig deur ʼn skerp afname in die membraan vloed. Skaalvorming kon nie verhoed word terwyl die aanleg bedryf word met superversadigde (SIg = 1.2) voeroplossings en slegs konsentraat hersirkulasie nie (m.a.w. skoon produkwater word opgevang), alhoewel skaalvorming vertraag kon word. Hierdie operasie het tot beduidend meer gekonsentreerde oplossings in die membraan gelei. Om te bepaal watter faktore die grootste invloed op totale produksietyd en netto produksie van skoon produkwater het, is ʼn fraksionele faktoriaalontwerp van 25-1 uitgelê wat vyf faktore toets, naamlik: 1) spoel frekwensie, 2) spoel volume, 3) skoon produkwater weektyd, 4) membraanvloed en 5) oombliklike herwinning. ʼn AVOVA analise het getoon dat totale produksietyd hoofsaaklik deur membraanvloed beïnvloed is, soos verwag kan word. Dit word gestaaf deurdat die aanleg, bedryf teen 24 LMH, slegs 3 - 4.2 L netto produkwater gelewer het, teenoor 7.6 - 9.7 L by 12 LMH. Hoër membraan vloedtempo’s het tot hoër vlakke van konsentrasie polarisasie op die membraanoppervlak gelei, wat ʼn groter neiging tot skaalvorming tot gevolg gehad het. Spoelfrekwensie en oombliklike herwinning het ʼn invloed op die netto produksie van skoon produkwater gehad, met 6 h-1 en 10 % as die onderskeie optimale waardes. ʼn Kleinstekwadraat regressie het aangedui dat die laagste produksietempo van skoon produkwater die hoogste netto produksie van skoon produkwater gelewer het, (asook die langste produksietyd). In opsomming: Hierdie studie het getoon dat gereelde spoeling met skoon produkwater die membraan skaalproses kan vertraag. Gedurende bedryf met superversadigde kalsiumsulfaat oplossings sonder enige antiskaalmiddels is daar gevind dat skaalvorming nie geheel en al vermy kon word nie. Die spoeltegniek, soos gebruik in hierdie studie, het die aanvang van skaalvorming in die laboratorium skaal TO eenheid vertraag, maar bedryf met konsentraat hersirkulasie en superversadigde oplossings (SIg = 1.2) het steeds skaal gevorm. Bykomende eksperimente teen verskeie kruisvloei snelhede gedurende die spoel stap word aanbeveel vir toekomstige studies.

Fibroblast growth factors (FGFs) regulate a broad spectrum of biological processes and aberrant FGF signalling has been linked to many disorders and diseases. Heparan sulphate (HS) is a highly sulphated glycosaminoglycan, which regulates the activity of its protein ligands, mainly through anionic interactions. The interactions between HS, FGF and FGF receptors (FGFRs) depend on the size and the spatial distribution of the anionic moieties of the saccharides. To test the effects of these on FGF signalling, the activities of well-defined HS oligosaccharides were screened in bioassays. The aim of this thesis was to study the structural determinants which underpin the specificity/selectivity in HS-FGF-FGFR interactions. Two approaches were initially explored to generate suitable saccharides for screening. Firstly, the preparation of libraries of HS oligosaccharides was attempted by enzymatic digestion of porcine mucosal HS using heparinase III. This was followed by the sequential fractionation using size exclusion chromatography, strong anion-exchange and cetyltrimethylammonium strong anion-exchange chromatography. However, with regards to preparing saccharides of sufficient purity and amounts, this was found to be a limiting factor for bioassay screening. Secondly, the dimeric modular synthesis of HS octasaccharides was attempted by means of in-solution multi-step synthesis. The synthesis of a small oligosaccharide library was partially successful and resulted in novel synthetic routes for generation of pentasaccharide precursors, but not sulphated saccharides for screening. An alternative strategy was taken to exploit nineteen existing fully defined chemically and chemoenzymatically prepared oligosaccharides. Screening in bioassays of specific FGF ligands, using BaF3 cells expressing single receptors, showed that both general and specific structural changes, as subtle as a single additional sulphate moiety, significantly impact the ability of saccharides to support FGF signalling in a ligand-receptor complex-dependent manner. The size of the saccharides, the presence/absence of 2-O-, 6-O- and N-sulphate groups were shown to be crucial factors for functional activity. Most notably, the presence of a single 3-O-sulphate group towards the non-reducing end of the saccharides was related to high levels of activation for FGF1-FGFR1c, FGF1-FGFR2b and FGF7-FGFR2b and was demonstrated for the first time. Overall, this thesis provides new evidence concerning structural determinants in HS that modulate FGF signalling, using fully defined saccharides for the first time. The results support the view that significant selectivity is involved, and contribute to a better fundamental understanding of how HS modulates FGF-FGFR-HS complex formation. Ultimately, this information could be relevant for the development of better targeted HS saccharide-based therapeutics.

Mestrado em Toxicologia e Ecotoxicologia
In the past years, an intensive usage of fertilizers and pesticides has been reported, mainly in the Mediterranean region, due to the wide agriculture production required to increase food production to respond to world exponential growth of human population. Copper, with several applications at industrial and agricultural activities is often discharged in the aquatic systems and this input can lead to damages to the ecosystems and its communities. Copper sulphate, is found in pesticides and fertilizers formulations, frequently used in the agricultural practice to control the pests. These chemicals once released into the environmental may have different fates and behaviour. Due to the adverse effects copper may have on aquatic species and to the aquatic systems, it becomes pivotal to evaluate the effects of this chemical in non-target species. Thus, the present study proposes to address the toxic and biochemical impacts of copper sulphate in two important commercial bivalve species, Cerastoderma edule and Scrobicularia plana, and two size classes, big (B) and small (S). Organisms were collected at the Mondego estuary (Figueira da Foz, Portugal) and transported to the laboratory in cold boxes with water from the estuary. After a depuration period, organisms from different size classes and both species were exposed to a range of concentrations of copper sulphate (0.6 mg/L; 0.9 mg/L; 1.2 mg/L; 1.5 mg/L; 1.8 mg/L; and 2.1 mg/L to both size classes of C.edule, and 1.0 mg/L; 1.5 mg/L; 2.0 mg/L; 2.5 mg/L; 3.0 mg/L; 3.5 mg/L; 4.0 mg/L to both size classes of S. plana) under laboratorial conditions. Changes in the fatty acid profiles and at the activity of the enzymes Glutathione reductase (GR), Glutathione S-transferase (GST) and Glutathione peroxidase (GPx) and the occurrence of lipid peroxidation, by the measurement of the thiobarbituric acid reactive species (TBARS) levels, were then determined to both size classes of the two bivalve species Biochemical analyses were conducted to: 1) organisms collected in the field, 2) organisms collected at the field and under a depuration period in the lab, and 3) organisms exposed to a range of copper sulphate concentrations under laboratory conditions. The results showed C. edule is more sensitive to the chemical (LC50= 0.818 (0.595- 0.987) mg/L; 1.129 (0.968 - 1.289) mg/L, to big and small organisms, respectively) action than S. plana (LC50= 2.563 (2.229 - 2.903) mg/L; 4.705 (3.540 -12.292) mg/L, to big and small organisms, correspondingly), with the small size exhibiting higher tolerance to the compound than the big size class in both bivalve species. At the biochemical level, S. plana also present a higher nutritive value than C. edule. S. plana show greater abundance and variety of FA and essential fatty acids (EFA), namely DHA and EPA, rates than C. edule. The behaviour and enzymatic activities were also affected by the copper sulphate concentrations, although C. edule exhibited a more consistent response to the chemical exposure than S. plana with C. edule being more affected. In conclusion, this study highlights Although the lower effects in biochemical and molecular pathways of S. plana, C. edule exhibits a more the coherent behavioural pattern in terms of fatty acid content and enzymatic of C. edule suggesting the usage of this species as a good bio-indicator in ecotoxicological studies to detect the presence of copper sulphate in aquatic systems, and the determination of fatty acid profile and enzymatic activity as good biomarkers to this chemical. The muscle (foot) proved to be a suitable tissue to determine the effect of pollutants in the antioxidant defence system of bivalve species, in addition to the digestive gland and gills.
Nos últimos anos tem-se registado um uso intensivo de fertilizantes e de pesticidas, principalmente na região do Mediterrâneo, devido à crescente produção agrícola necessária para aumentar a produção de alimentos de modo a responder ao crescimento exponencial da população humana mundial. O cobre, com várias aplicações em atividades industriais e agrícolas, é, muitas vezes, arrastado por escorrência para sistemas aquáticos, podendo representar uma ameaça para os ecossistemas e para as comunidades aquáticas que habitam nesses sistemas. O sulfato de cobre está presente em formulações de pesticidas e fertilizantes e é frequentemente utilizado em práticas agrícolas para controlo de pragas. Estes produtos químicos, uma vez libertados para o ambiente, podem ter diferentes destinos e comportamentos. Devido aos efeitos adversos que o cobre pode ter em espécies aquáticas e nos sistemas aquáticos, é fundamental avaliar os efeitos deste produto químico em espécies não-alvo. Assim, o presente estudo pretende determinar os impactos tóxicos e bioquímicos do sulfato de cobre em duas espécies de bivalves com importante valor comercial, Cerastoderma edule e Scrobicularia plana, e em duas classes de tamanho. Os organismos foram recolhidos no estuário do Mondego (Figueira da Foz, Portugal) e transportados para o laboratório em malas térmicas, que no interior continham água do estuário. Após um período de depuração no laboratório, os organismos foram expostos a uma gama de concentrações de sulfato de cobre (0,6 mg / L; 0,9 mg / L, 1,2 mg / L, 1,5 mg / L, 1,8 mg / L e 2,1 mg / L para ambas as classes de tamanho de C.edule, e 1,0 mg / L, 1,5 mg / L, 2,0 mg / L, 2,5 mg / L; 3,0 mg / L; 3,5 mg / L; 4,0 mg / L para ambas as classes de tamanho de S. plana) sob condições de temperatura e fotoperíodo controladas. Posteriormente avaliaram-se alterações no perfil de ácidos gordos e na atividade das enzimas Glutationa redutase (GR), Glutationa S-transferase (GST) e Glutationa peroxidase (GPx), bem como a ocorrência de peroxidação lipídica, pela medição das espécies reativas ao ácido tiobarbitúrico (TBARS), para ambas as classes de tamanho em ambas as espécies de bivalves. As análises bioquímicas foram realizadas em: 1) organismos recolhidos no campo, 2) organismos após um período de depuração no laboratório, e 3) organismos expostos a uma gama de concentrações de sulfato de cobre. Os resultados mostraram que C. edule é mais sensível à ação do químico (LC50 = 0,818 (0,595- 0,987) mg / L; 1,129 (0,968 - 1,289) mg / L, para organismos grandes e pequenos, respetivamente) do que S. plana (LC50 = 2,563 (2,229 – 2,903) mg / L; 4,705 (3,540 -12,292) mg / L, para organismos grandes e pequenos, respetivamente), com a classe de tamanho pequeno a apresentar maior tolerância ao composto do que a classe de tamanho grande em ambas as espécies. Ao nível bioquímico, S. plana também apresentou um valor nutritivo maior do que C. edule. S. plana apresentou maior abundância e variedade em FA e ácidos gordos essenciais (EFA), nomeadamente DHA e EPA, do que C. edule. O comportamento e as atividades enzimáticas também foram afetados pelas concentrações de sulfato de cobre. No entanto, C. edule exibiu uma resposta mais constante à exposição ao químico do que S. plana, com C. edule a revelar ser a espécie mais sensível. Em conclusão, apesar dos efeitos observados nas vias bioquímicas e moleculares de S. plana serem menos acentuados, C. edule apresentou um padrão nutricional mais coerente no teor em ácidos gordos e na atividade enzimática. Assim, C. edule pode ser considerado um bom bioindicador em estudos ecotoxicológicos para detetar a presença de sulfato de cobre em sistemas aquáticos, através da medição do perfil em ácidos gordos e da atividade enzimática que revelaram ser bons biomarcadores para detetar a presença deste químico. O músculo (pé) revelou ser um tecido adequado na determinação do efeito de poluentes no sistema de defesa anti-oxidante de bivalves aquáticos, para além da glândula digestiva e das brânquias.

A detailed study has been conducted on the crystallisation kinetics and growth of some inorganic sulphates and carbonates, in view of their growing importance as enviromentally friendly high surface area powders in detergent applications. Predictions of the crystal morphology based on lattice geometry laws have been obtained and compared to the growth morphology. A mechanism for habit modification has been postulated and compared to experimental studies of the effects of impurities on the crystallisation of sodium carbonate monohydrate and sodium carbonate decahydrate. Intermolecular force potentials have been empirically derived for β potassium sulphate which accurately predict its solid state properties. The intermolecular force potentials are successfully transferred and applied to a simulation of the low temperature phase of sodium sulphate. The phase diagram of the Na₂CO₃-Na₂SO₄-H₂0 system has been redetermined using powder diffraction, chemical analysis and Scanning Electron Microscopy as analysis tools. Evidence for burkeite supercell formation has been noted at a variety of solution compositions and crystallisation temperatures. The degree of agglomeration present in the system has been determined to be a function of the carbonate content of the crystallising solution. Burkeite is noted to act as an agglomeration nucleator, extensively binding to the other phases present. A reduction in precipitation temperature leads to a corresponding increase in the particle size distribution. The application of nucleation theory to inorganic systems is examined through the use of an automated crystallisation cell employing solution turbidometry, conductivity and temperature, to probe nuclei formation in the cases of potash alum (AIK(SO₄)₂.12H₂0), ammonium dihydrogen orthophosphate (NH₄H₂PO₄), sodium carbonate decahydrate (Na₂CO₃.10H₂0) and sodium sulphate decahydrate (Na₂SO₄.10H₂0). Turbidometry is determined to be the most reliable means of detecting the onset of nucleation. Reasonable correlation is noted for the systems studied, between measured saturation curves as determined by this instrument and previous observations. Interfacial energies based on induction time measurements are determined to be significantly smaller than those determined in previous kinetic and dissolution enthalpy studies. The preparation of highly porous, high surface area powders for carrying liquids in detergent powders has been examined. It was determined that a significant proportion of the desirable powder porosity for a burkeite powder occurred during the initial batch crystallisation stage. No evidence for a burkeite powder to tend towards a monosize particle distribution was noted. Milling and spray drying of slurry lead to a significant increase in powder porosity. Increasing the drying time during spray drying led to a corresponding increase in the powder porosity. It was observed that further studies of the spray drying conditions employed for burkeite production are required, for optimisation of the liquid uptake of the resultant powder.

Content: In this study, different proportions 2.5%, 5%, 10% of aluminum sulfate were used as tanning agents during parchment production. The research was carried out on goat skin and also there were no usage of any tanning agents as control groups. Finished leathers have been exposed to ageing conditions. Before and after ageing color measurements on all finished leathers have been conducted with Konica Minolta CM-3600d brand spectrophotometer. The impacts of the aluminum sulfate utilized in the research on light fastness were also inspected by using an ATLAS-XENOTEST ALPHA+ test instrument. Visible whitening on the color of parchment was observeded when tanning process with aluminum sulphate was performed. Take-Away: -Aluminum sulfate has tanning effects -Aluminium gave white color to the parchment -Aluminum sulfate changed collagen structure.

The effects of sulphate and curing temperature play an important role on the strength development and durability of Cemented Paste Backfill (CPBs). Depending on the application of the CPB, different strength values, measured as unconfined compressive strength (UCS), are targeted. There is a lack of proven theory to predict the UCS for a specific CPB mix due to the complexity of the interactions between the variables that affect the CPB strength. This thesis presents an approach to use the artificial neural network (ANN) methodology in order to develop two models that can predict the effects of sulphate and curing temperature on the UCS of CPBs. The ANN models here developed illustrate an outstanding accuracy in the UCS prediction for the simulation of sulphate and its coupled effect with curing temperature. The ANN models provide a better understanding of the effects of sulphate and/or temperature on the strength of CPBs.