Co-precipitation and absorption methods were investigated for removal of boron from produced water, which is groundwater brought to the surface during oil and natural gas extraction. Boron can be toxic to many crops and often needs to be controlled to low levels in irrigation water. The present research focused on synthetic reverse osmosis (RO) concentrate modeled on concentrate expected from a future treatment facility at the Arroyo Grande Oil Field on the central coast of California. The produced water at this site is brackish with a boron concentration of 8 mg/L and an expected temperature of 80°C. The future overall produced water treatment process will include lime softening, micro-filtration, cooling, ion exchange, and finally RO. Projected boron concentrations in the RO concentrate are 20 to 25 mg/L. Concentrate temperature will be near ambient. This RO concentrate will be injected back into the formation. To prevent an accumulation of boron in the formation, it is desired to reduce boron concentrations in this concentrate and partition the boron into a solid sludge that could be transported out of the area. The primary method explored for boron removal during this study was adsorption and co-precipitation by magnesium chloride. Some magnesium oxide tests were also conducted. Jar testing was used to determine the degree of boron removal as a function of initial concentration, pH, temperature, and reaction time. Synthetic RO concentrate was used to control background water quality factors that could potentially influence boron removal. The standard synthetic RO concentrate contained 8 g NaCl/L, 150 mg Si/L and 30 mg B/L. After synthetic RO concentrate was prepared, amendments (e.g. sulfate, sodium chloride) were added and the pH adjusted to the desired value. Each solution was then carried through a mixing and settling protocol (5 min at 200 RPM, 10 min at 20 RPM, followed by 30 min settling and filtration). Boron concentrations from the jar tests were determined using the Carmine colorimetric method. Boron removal with magnesium chloride was greatest at a pH of 11.0. At this pH 87% of boron was removed using 5.0 g/L MgCl2◦6H2O at 20°C. Mixing time did not greatly affect boron removal for mixing periods of 5 to 1321 minutes. This result indicates equilibrium was achieved during the 45-min experimental protocol. Maximum boron removal was observed in the temperature range of 29°C to 41°C. At 68°C boron removal decreased five-fold compared to the reduction observed at 29°C to 41°C. For treatment of the cool concentrate, this relatively low optimal temperature range gives magnesium chloride an advantage over magnesium oxide, which is effective only at high temperatures. Neither sodium chloride nor sodium sulfate affected boron removal by magnesium chloride for the chloride and sulfate concentrations expected in the produced water at this site. In contrast, silica did inhibit boron removal, with removal decreasing from 30% to 5% when silica concentration was increased from 0 to 100 mmols/L. This result was unexpected because other researchers have reported silica is necessary for effective removal of boron by magnesium chloride. To investigate the reasons for the differing boron removal results for magnesium chloride and magnesium oxide, solids produced by the two reagents were compared using X-ray diffraction spectroscopy (XRD). Solids from magnesium chloride contained 30% amorphous material versus 10% for magnesium oxide. The crystalline components from the magnesium oxide treatment were for the most part magnesium oxide, whereas magnesium chloride crystalline solids were a combination of brucite (Mg(OH)2) and magnesium chloride hydroxide. The greater boron adsorption observed with magnesium chloride could thus either be attributed to the greater surface area of the amorphous precipitate and/or the higher boron affinity of brucite and magnesium chloride hydroxide. Adsorption isotherms were plotted for boron removal by magnesium compounds formed during precipitation. Boron adsorption followed a linear isotherm (r2= 0.92) for boron concentrations up to 37.8 mg B/L. While the data also fit Langmuir and Freundlich models the data fell in the linear range of those models. The linearity of the adsorption curves indicates that adsorption sites for boron were not saturated at these concentrations. The linearity means that higher boron concentrations in the RO concentrate will lead to greater mass removal, up to concentrations of at least 37.8 mg/L boron. Using magnesium chloride, boron removal by co-precipitation was more effective than by adsorption to pre-formed precipitate. Removal approximately doubled for a given dose of magnesium chloride. The effectiveness of co-precipitation presumably occurs due to entrapment of boron as the precipitate forms. This study has shown the potential of magnesium chloride as an agent for boron removal by determining those conditions most effective for boron co-precipitation and adsorption. Magnesium chloride has been shown to be more effective than magnesium oxide. Magnesium chloride also out-performed treatment with slaked quicklime, which was tested previously by others. Two important limitations of boron removal with magnesium chloride are the high chemical requirements (5 g/L MgCl2) and sludge production (1 g/g MgCl2 used). These are greatly mitigated by treatment of RO concentrate rather than the full produced water flow. In addition, reagent use and sludge production might be decreased by recycling sludge from the up-front lime softening process. Compared to magnesium oxide, magnesium chloride removes greater quantities of boron per mole of magnesium added (20 mg B/g MgCl2). The magnesium chloride isotherm demonstrated that treatment of RO concentrate required less reagent and produced less sludge per mass of boron removed than treatment of the more dilute feed water.

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Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The facilities for radionuclide production at iThemba LABS have undergone a number of significant upgrades over the last decade in order to increase the production capacity and to diversify the product portfolio. Central to this effort is a new vertical beam target station (VBTS) and its associated targetry, designed and built to operate at higher proton beam intensities for the large-scale production of relatively long-lived, high-value radionuclides such as 22Na, 68Ge and 82Sr. Along with the VBTS, an existing smaller horizontal beam target station was adapted to accommodate targetry for 18F production, mainly to supply 18F-FDG for use in positron emission tomography (PET). The production capacity was further enhanced by means of a beam splitter to enable bombardments in two target stations simultaneously. This required new developments on several systems, e.g. beam diagnostics, control, interlocking and cooling. This project brings together a number of different aspects of the upgraded facilities as well as the associated research and development that enable the production of radionuclides in the medium energy region, up to approximately 70 MeV. Investigations were performed on the cooling of the interfacial windows between the cyclotron vacuum and the targets as well as the direct cooling of the targets themselves during intense proton bombardments. For this purpose, empirical as well as computational fluid dynamics (CFD) calculations were performed. In addition, the local radiation shield of the VBTS as well as the beam transport in some of the targetry was investigated by means of Monte Carlo radiation transport calculations. Excitation functions for the production of various radionuclides in the 66 MeV proton bombardment of 192Os, 159Tb, natGd, 155Gd, 152Gd, 93Nb, natZr and 89Y were measured and compared with theoretical predictions by means of statistical nuclear model calculations as well as the TENDL-2012 library. In particular, the production of 186Re, selected radioterbiums (149;152;155Tb) and radiozirconiums (88;89Zr) is of interest in existing and emerging diagnostic and therapeutic applications in nuclear medicine. A study on 28Mg production in the proton bombardment of natCl using stacked chloride targets was also performed at 200 MeV. This radionuclide is of interest as 28Mg is the only practical radiotracer of Mg. Finally, new targetry for the production of 18F was developed, modelled and optimized for the non-standard degraded beam employed in this particular case. / AFRIKAANSE OPSOMMING: Die fasiliteite vir die produksie van radionukliede by iThemba LABS is gedurende die afgelope dekade aansienlik opgegradeer om die produksiekapasiteit te verhoog en om die portfolio van produkte te diversifiseer. Sentraal tot hierdie poging is ’n vertikale-bundel skyfstasie (VBTS) wat gebou is om skywe met hoër intensiteit protonbundels te bombardeer ten einde relatief langlewende, hoë-waarde radionukliede op grootmaat te produseer, insluitende 22Na, 68Ge en 82Sr. Terselfdetyd is ’n bestaande, kleiner horisontale-bundel skyfstasie aangepas om skywe vir die produksie van 18F te huisves, meestal om 18FFDG vir positronemissietomografie (PET) te lewer. Die produksiekapasiteit is verder verhoog d.m.v. ’n bundeldeler sodat bundel gelyktyding aan twee skyfstasies gelewer kan word. Dit het ontwikkelingswerk vereis aan verskeie stelsels, insluitende diagnostiek, beheer, vergrendeling en verkoeling. Hierdie projek bring verskeie aspekte bymekaar t.o.v. die opgegradeerde produksiefasiliteite sowel as die geassosieerde navorsing en ontwikkeling benodig vir radionukliedproduksie in die middelenergiegebied tot ongeveer 70 MeV. Die verkoeling van die foelievensters tussen die vakuum van die siklotron en die skyfgerei is ondersoek sowel as die direkte verkoeling van skywe onder intense protonbombardement. Hierdie studie sluit beide empiriese sowel as numeriese vloeidinamika berekeninge in. Verder is die afskerming van die VBTS asook die bundeltransport in verskeie skywe ondersoek m.b.v. Monte Carlo stralingstransport berekeninge. Opwekkrommes vir die produksie van verskeie radionukliede met protongeïnduseerde reaksies tot en met 66 MeV op 192Os, 159Tb, natGd, 155Gd, 152Gd, 93Nb, natZr en 89Y is gemeet en vergelyk met statistiese kernmodel berekeninge sowel as die TENDL-2012 biblioteek. Die produksie van 186Re, verskeie radioterbiums (149;152;155Tb) en radiozirkoniums (88;89Zr) is van spesifieke belang vir bestaande en toekomstige diagnostiese en terapeutiese toepassings in die kerngeneeskunde. ’n Studie op die produksie van 28Mg in die bombardement van natCl met 200 MeV protone is ook onderneem. In hierdie ondersoek is ’n stapel chloriedskywe gebruik. Die 28Mg is van belang omdat dit die enigste Mg radioisotoop is wat geskik is as ’n radiospoorder van dié element. Laastens is nuwe skyfgerei vir die produksie van 18F ontwikkel, gemodelleer en geoptimiseer vir die nie-standaard afgeremde bundel wat benut word in hierdie geval.

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As propriedades requeridas em relação à resistência e à durabilidade de um concreto no estado endurecido estão diretamente ligadas às suas condições no estado fresco, sendo assim, etapas como processo de mistura, transporte, lançamento e adensamento do concreto devem ser adequadamente monitoradas e controladas ao longo do tempo, durante seu estado fresco. A norma brasileira NBR 7212 (ABNT, 2012), para execução de concreto dosado em central, estipula o tempo máximo para que o concreto seja completamente descarregado (aplicado) em 150 minutos. No entanto, em diversas situações práticas observam-se contratempos relacionados com atrasos na execução da obra ou no transporte para entrega do concreto, fazendo com que no momento de lançamento este concreto seja rejeitado em função do tempo decorrido entre o início da mistura dos materiais e a aplicação do concreto no canteiro de obra, além de apresentar considerável perda em sua trabalhabilidade. Porém, principalmente, em função de cronogramas de obras, de custo e da preocupação ambiental, fica clara a necessidade de alternativas que viabilizem sua utilização, garantindo as condições adequadas para lançamento e adensamento, sem que haja impactos negativos em suas propriedades finais. O objetivo desta pesquisa consiste na avaliação das propriedades mecânicas e de durabilidade do concreto, quando mantido em mistura prolongada e utilizado após esse tempo máximo de mistura e transporte especificado pela norma, a partir do primeiro contato do cimento com a água. Os concretos foram produzidos com dois tipos de cimento, CPIV e CPII, e seu abatimento foi mantido ao longo de 6 horas de mistura com a incorporação de aditivo superplastificante à base policarboxilato. Nesse estudo adotaram-se três relações a/c e a produção dos concretos foi realizada em laboratório e em condição real numa central dosadora de concreto. Os resultados obtidos, para os materiais e procedimento utilizados, avaliando o comportamento do concreto em relação ao módulo de deformação, calor de hidratação gerado, carbonatação e penetração de cloretos pela exposição à condição natural, mostram que não há perda no seu desempenho final, quando utilizado acima do tempo especificado por norma, adotando o procedimento de manutenção do abatimento com a incorporação de aditivo superplastificante à base de policarboxilato, conforme proposta deste estudo. Análises do comportamento reológico e microestruturais em pastas de cimento, com as mesmas características utilizadas na produção dos concretos, corroboram com os resultados obtidos. / The required properties in relation to the concrete strength and durability in the hardened state are directly linked to its fresh state conditions, thus, steps such as concrete mixing, transporting, launching and compacting must be properly monitored and controlled during this material production. The Brazilian Standard (NBR 7212/2012) for central mixed concrete stipulates as 150 minutes the maximum time for completely concrete discharging (applying). However, there are setbacks related to execution or transportation delays, resulting in workability loss, often causing this concrete rejection in building plants. Therefore, due to work schedules, cost and environmental concern, it is clear the need for alternatives that make feasible this concrete use, guaranteeing the appropriate launching conditions and densification, without negative impacts on its hardened properties. In this context, this research subject is to evaluate the concrete mechanical properties and durability, when kept in prolonged mixing conditions and used after the maximum mixing and transport time specified by the Brazilian standard. The concretes were produced with two kinds of Portland Brazilian cement, called CP IV e CP II, with fixed consistency and with polycarboxylate superplasticizer addition. Additionally, three water/cement ratios were analyzed in concretes mixed in the laboratory and central mixed conditions. In this research, where analyzed concretes with an overpass time of application, maintaining the consistency with superplasticizer addition. With the materials and procedures utilized, it was not observed loss on concrete performance related to the modulus of elasticity, hydration heat, carbonation and chloride penetration under natural exposure. The rheological and microstructural analysis in cement pastes, reproducing the concrete proprieties, corroborates with this conclusion.

The purpose of this study is to investigate upper secondary school teachers’ perception of publisher produced digital tools within the frame of each teachers’ subject teaching in Swedish. The study questions following the issues: (1) what attitude do teachers have towards publisher produced digital tools within the field of their subject Swedish? (2) Which, if any, expectations from the principal/ school administration do the teachers have of using the publisher produced digital tool in their education? And (3) how is the publisher produced digital tool applied in the education? To answer these questions, semi-structured interviews were conducted with six upper secondary school teachers who, among other subjects, teach Swedish. This study relies on a phenomenographic method and the phenomenon is the publisher produced digital tool. The result shows that the six interviewed teachers use publisher produced digital tools between 10 and 20 percent of their lesson time in subject of Swedish. That low utilization can partially be explained by the teachers’ long tradition of constructing their own teaching materials. Another explanation could be that publisher produced digital tools are relatively new and that the teachers feel uncomfortable using them. The expectations from the principal/school administration about the teachers’ usage of these digital tools in their teaching is relatively low. Whether the usage of publisher produced digital tools is going to increase or not in the future is unknown – it is up to the teachers of Swedish to determine.