Naphthenic acids (NAs) are natural constituents of bitumen and crude oil, and predominantly obtained as the by-product of petroleum refining with variable composition and ingredients. Naphthenic acids are composed of alkyl-substituted cycloaliphatic carboxylic acids, with smaller amounts of acyclic aliphatic acids. Naphthenic acids become a significant part of the tailings pond water (TPW) after separation from oil sands material. NAs are soluble in water and are concentrated in TPW as a result of caustic oil sands extraction processes. Tailings ponds near the Athabasca oil sands region near Fort McMurray, Alberta, Canada are contaminated with a variety of toxic organic compounds released in industrial effluent from the oil extraction processes. NAs are among the major water contaminants in those regions because of their toxicity and environmental recalcitrance. They may enter surface water systems due to erosion of riverbank oil sands deposits and through groundwater mixing. Significant environmental and regulatory attention has been focused on the naphthenic acids fraction of oil sands material to address these challenges and potential hazards. Biological, chemical, and photolytic treatments of water contaminated with NAs have been studied, but are either time consuming or involve significant capital investment. There is a growing need to develop more efficient and cost-effective treatment methods. Based on existing literature, microwave and photocatalysis for degradation of naphthenic acids in water may be one solution. A knowledge gap exists in determining the effect of microwave energy and/or photocatalysis on the rate and extent of NAs degradation in contaminated water.<p> Part of this work included evaluation of the physical and chemical properties of NAs. Dielectric properties, important for designing a microwave system, were investigated. Effects of temperature, concentration, and frequency of microwaves on the dielectric properties of NA-water mixtures were studied and were used in designing the treatment systems for NAs. Three laboratory scale systems, (1) photocatalysis, (2) microwave, and (3) microwave assisted photocatalysis systems were designed and developed. Experiments were conducted to determine the NA degradation efficiency of these systems for both commercially available Fluka NAs and those extracted from oil sand process water (OSPW). Effects of water source (deionised and river water) and use of TiO2 catalyst in the degradation process, were also investigated. Degradation kinetics for total NAs as well as individual z-family were calculated.<p> Results show that the three developed treatment systems were able to degrade NAs at a faster rate than the methods reported to date. The concentration of higher molecular weight NAs (z = -4 to -12) decreased more significantly than the lower molecular weight NAs in all the three treatment systems. Toxicity assessments of the NAs samples before and after treatment indicated that photocatalysis and microwave assisted photocatalysis systems decreased the toxicity of Fluka and OSPW NAs completely (up to 5 min IC50 v/v > 90%). The microwave system reduced the toxicity of water containing Fluka NAs from high (5 min IC50 v/v = 15.85%) to moderate (5 min IC50 v/v = 36.45%) toxicity. However, a slight increase in toxicity was noted post-treatment in OSPW NAs.<p> Microwave-assisted photocatalysis was the most rapid degradation system for OSPW NA extracts in water with a half-life of 0.56 h in the presence of TiO2. The microwave system degraded OSPW NAs in water at a more moderate half-life of 3.32 h. The photocatalysis system was the slowest with a half-life of 3.99 h under similar conditions.<p> High and ultra high resolution analysis of NA sample, estimations of cost and further efficiency related research of the developed systems to treat water with microbial load along with chemical contaminants are recommended for future work to further validate these treatment systems.

Naphthenic acids (NAs) are natural constituents of bitumen and crude oil, and predominantly obtained as the by-product of petroleum refining with variable composition and ingredients. Naphthenic acids are composed of alkyl-substituted cycloaliphatic carboxylic acids, with smaller amounts of acyclic aliphatic acids. Naphthenic acids become a significant part of the tailings pond water (TPW) after separation from oil sands material. NAs are soluble in water and are concentrated in TPW as a result of caustic oil sands extraction processes. Tailings ponds near the Athabasca oil sands region near Fort McMurray, Alberta, Canada are contaminated with a variety of toxic organic compounds released in industrial effluent from the oil extraction processes. NAs are among the major water contaminants in those regions because of their toxicity and environmental recalcitrance. They may enter surface water systems due to erosion of riverbank oil sands deposits and through groundwater mixing. Significant environmental and regulatory attention has been focused on the naphthenic acids fraction of oil sands material to address these challenges and potential hazards. Biological, chemical, and photolytic treatments of water contaminated with NAs have been studied, but are either time consuming or involve significant capital investment. There is a growing need to develop more efficient and cost-effective treatment methods. Based on existing literature, microwave and photocatalysis for degradation of naphthenic acids in water may be one solution. A knowledge gap exists in determining the effect of microwave energy and/or photocatalysis on the rate and extent of NAs degradation in contaminated water.<p> Part of this work included evaluation of the physical and chemical properties of NAs. Dielectric properties, important for designing a microwave system, were investigated. Effects of temperature, concentration, and frequency of microwaves on the dielectric properties of NA-water mixtures were studied and were used in designing the treatment systems for NAs. Three laboratory scale systems, (1) photocatalysis, (2) microwave, and (3) microwave assisted photocatalysis systems were designed and developed. Experiments were conducted to determine the NA degradation efficiency of these systems for both commercially available Fluka NAs and those extracted from oil sand process water (OSPW). Effects of water source (deionised and river water) and use of TiO2 catalyst in the degradation process, were also investigated. Degradation kinetics for total NAs as well as individual z-family were calculated.<p> Results show that the three developed treatment systems were able to degrade NAs at a faster rate than the methods reported to date. The concentration of higher molecular weight NAs (z = -4 to -12) decreased more significantly than the lower molecular weight NAs in all the three treatment systems. Toxicity assessments of the NAs samples before and after treatment indicated that photocatalysis and microwave assisted photocatalysis systems decreased the toxicity of Fluka and OSPW NAs completely (up to 5 min IC50 v/v > 90%). The microwave system reduced the toxicity of water containing Fluka NAs from high (5 min IC50 v/v = 15.85%) to moderate (5 min IC50 v/v = 36.45%) toxicity. However, a slight increase in toxicity was noted post-treatment in OSPW NAs.<p> Microwave-assisted photocatalysis was the most rapid degradation system for OSPW NA extracts in water with a half-life of 0.56 h in the presence of TiO2. The microwave system degraded OSPW NAs in water at a more moderate half-life of 3.32 h. The photocatalysis system was the slowest with a half-life of 3.99 h under similar conditions.<p> High and ultra high resolution analysis of NA sample, estimations of cost and further efficiency related research of the developed systems to treat water with microbial load along with chemical contaminants are recommended for future work to further validate these treatment systems.

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Previous work has shown that microwave heating of mineral ores induces fractures around grain boundaries due to the differences in absorption of microwaves and the resulting differential thermal expansion among the various mineral phases in the ore particles. As a consequence, this reduces the energy required in subsequent grinding and enhances liberation of valuable minerals. In this study, first, the influences of different variables on bulk strength reduction of microwave treated ores have been investigated. Nine different binary ore models were constructed by randomly disseminating 10 vol.% microwave absorbing minerals in transparent matrices. Computational simulations of heating, thermal damage and unconfined compressive strength (UCS) tests on the conceptual binary ores have been undertaken by using finite-difference modelling techniques. The influence of thermo-mechanical properties of minerals on strength reduction of microwave treated ores was examined. It was shown that in general the thermal properties of the microwave absorbing mineral and the mechanical properties of the transparent matrix have the most significant effect on the strength reduction. Binary ores containing a microwave absorbing mineral that has a high thermal expansion coefficient in a strong transparent matrix achieved higher reductions in strength. The influence of absorbent phase grain size on strength reduction of ores was also quantified. It was shown that for the same energy inputs and mineral types, the reductions in strength were much higher in coarse-grained ores. It has also been shown that for the same mineralogy and treatment condition, ores with poorly disseminated heated phase achieved much higher strength reduction. The effect of microwave treatment on the mechanical state of an ore sample was also examined. It was demonstrated that unconfined compressive strength is less sensitive to microwave-induced micro-fractures and found to be a poor descriptor of liberation behaviour. A new method of characterizing damage in microwave treated ore using a continuum approach was developed. The method measures the damage around the grain boundary regions during the heating process. Using the method, it was possible to elucidate in detail the influences of power density, mineralogy, ore texture on microwave treatment of ore. It was shown that the amount of grain boundary damage incurred at a specific power density and energy input is dependent both on the ore mineralogy and its texture. The energy inputs that were required for significant (> 10%) grain boundary damage in the ores range from 0.09 to 7.06 kWh/t depending on the power density applied, the ore mineralogy and its texture. It was also shown that for a given mineralogy and ore texture there is a power density level below which no further increase in grain boundary damage is possible by increasing exposure time. The effect of pulse repetition frequency on grain boundary damage was also elucidated using the method. It was found that high pulse repetition frequencies (³ 50 Hz) resulted in an amount of grain boundary damage that was indistinguishable from that caused by continuous wave operation for a fixed energy input. It has also been shown that for a fixed microwave energy input the best result would be obtained by using the lowest possible pulse repetition frequency and highest peak pulse power. The effect of microwave treatment of ores at different treatment conditions on the extent of damage and crack pattern was also investigated in detail using bondedparticle model (BPM). It has been shown that the amount of micro-cracks and also the cracks pattern in an ore sample after microwave treatment significantly depend on its mineralogy, microwave treatment condition (power density) and absorbent phase grain size. It has also been shown that a minimum power density is required to localize damage around the grain boundary in an ore sample. This minimum power density was found to strongly depend on the ore mineralogy and its texture. Initial simulation test work concerning the effect of microwave treatment on liberation of minerals is also presented. It has been shown that microwave irradiation considerably changed the fracture pattern of an ore in simulated single particle crushing. The fracture pattern of the ore treated at high power density (Pd = 0.1 kW /mm3abs for 1 ms) was along the grain boundary and the absorbent mineral was intact. In the ore treated at lower power density for the same energy input (Pd = 1 W/mm3abs for 0.1 s) both intergranular and transgranular fractures were observed. However, in all cases the fracture patterns were preferentially localized around the grain boundary compared to that of the untreated ore. / AFRIKAANSE OPSOMMING: Vorige studies het getoon dat mikrogolfverhitting van mineraalertse tot breuke om die ertskorrelgrense aanleiding gee, omdat die verskillende mineraalfases in die ertsdeeltjies die mikrogolwe verskillend absorbeer, en dus ook verskillend uitsit. Korrelgrensbreuke verminder die vereiste energie vir latere slypwerk, en verhoog die vrystelling van waardevolle minerale. Hierdie studie het eerstens die uitwerking van verskillende veranderlikes op die algehele sterktevermindering van mikrogolfbehandelde ertse ondersoek. Hiervoor is nege verskillende binêre ertsmodelle vervaardig deur mikrogolfabsorberende minerale met ʼn volumepersentasie van 10% lukraak in deursigtige matrikse te versprei. Met behulp van eindigeverskilmodelleringstegnieke is berekeningsimulasies van verhitting, warmteskade en onbegrensde druksterkte (“unconfined compressive strength”) op die konseptuele binêre ertse uitgevoer. Die invloed van termomeganiese mineraaleienskappe op die sterktevermindering van mikrogolfbehandelde ertse is eerste onder die loep geneem. Daar is bevind dat die warmte-eienskappe van die mikrogolfabsorberende mineraal, en die meganiese eienskappe van die deursigtige matriks, die beduidendste uitwerking op sterktevermindering het. Binêre ertse wat ʼn mikrogolfabsorberende mineraal bevat met ʼn hoë warmte-uitsettingskoëffisiënt in ʼn sterk deursigtige matriks, het groter sterkteverminderings getoon. Die invloed van korrelgrootte in die absorbeerfase op die sterktevermindering van ertse is volgende versyfer. Die studie het getoon dat, op grond van dieselfde energie-insette en mineraalsoorte, grofkorrelrige ertse groter sterktevermindering ondergaan het. Eweneens is bewys dat, met dieselfde mineralogie en behandelingsomstandighede, ertse met ʼn swak verspreide verhittingsfase ook groter sterktevermindering ervaar. Die uitwerking van mikrogolfbehandeling op die meganiese toestand van ʼn ertsmonster is boonop ondersoek. Die studie het getoon dat onbegrensde druksterkte minder gevoelig vir mikrogolfgeïnduseerde mikrobreuke is, en as ʼn swak aanwyser van vrystellingsgedrag beskou word. ʼn Nuwe metode om skade by mikrogolfbehandelde ertse te tipeer is gevolglik met behulp van ʼn kontinuumbenadering ontwikkel. Dié metode meet die skade rondom die korrelgrens gedurende die verhittingsproses. Deur middel van voormelde metode was dit dus moontlik om die invloed van kragdigtheid, mineralogie en ertstekstuur op die mikrogolfbehandeling van erts deeglik te ondersoek. Daar is bevind dat die mate van korrelgrensskade by ʼn bepaalde kragdigtheid en energie-inset, van sowel die ertsmineralogie as ertstekstuur afhang. Na gelang van die toegepaste kragdigtheid, die ertsmineralogie en ertstekstuur, het die vereiste energie-insette vir beduidende (>10%) korrelgrensskade van 0,09 tot 7,06 kWh/t gewissel. Dit het voorts geblyk dat enige bepaalde mineralogie en ertstekstuur oor ʼn minimum kragdigtheidsvlak beskik, onder welke vlak geen verlenging in blootstellingstyd enige verdere korrelgrensskade kan veroorsaak nie. Die uitwerking van pulsherhaalfrekwensie op korrelgrensskade is ook met behulp van bogenoemde metode verklaar. Die studie het getoon dat, op grond van ʼn vaste energie-inset, hoë pulsherhaalfrekwensies (≥50 Hz) en gelykgolfwerking presies dieselfde hoeveelheid korrelgrensskade tot gevolg het. Volgende is daar met behulp van ʼn gebondedeeltjiemodel (“bonded-particle model”) noukeurig ondersoek ingestel na die uitwerking van verskillende mikrogolfbehandelingsomstandighede op die hoeveelheid skade en die kraakpatroon by ertse. Die studie het getoon dat die hoeveelheid mikrokrake sowel as die kraakpatroon in ʼn mikrogolfbehandelde ertsmonster in ʼn groot mate van die betrokke erts se mineralogie, mikrogolfbehandelingsomstandighede (kragdigtheid) en korrelgrootte in die absorbeerfase afhang. Daar is ook bevind dat ʼn minimum kragdigtheid nodig is om skade tot die gebied om die korrelgrens te beperk, welke minimum kragdigtheid oënskynlik grotendeels deur die ertsmineralogie en -tekstuur bepaal word. Die studie bevat ook die resultate van aanvangsimulasietoetse oor die uitwerking van mikrogolfbehandeling op mineraalvrystelling. Die toetse het getoon dat mikrogolfbestraling ʼn beduidende verandering tot gevolg het in die ertsbreekpatroon met gesimuleerde enkeldeeltjievergruising. Die breekpatroon van die erts wat by hoë kragdigtheid (Pd = 0,1 kW/mm3abs vir 1 ms) behandel is, het ál langs die korrelgrens gestrek, terwyl die absorberende mineraal nog ongeskonde was. In die erts wat by laer kragdigtheid dog dieselfde energie-inset behandel is (Pd = 1 W/mm3abs vir 0,1 s), is sowel tussenkorrel- as oorkorrelbreuke opgemerk. In teenstelling met die onbehandelde erts, was die breekpatrone by die behandelde erts egter in alle gevalle steeds merendeels rondom die korrelgrens geleë.

Estruturas de sílica mesoporosa cúbica em forma de gaiola (originalmente identificadas como FDU-1) altamente ordenadas, estáveis térmica e hidrotermicamente, com tamanhos de poros da ordem de 12 nm, foram sintetizadas a partir de TEOS e como molde utilizou-se o copolímero tribloco poli(óxido de etileno)-poli(óxido de butileno)-poli(óxido de etileno) 850-6600 (EO39BO47EO39), em meio ácido. Foi desenvolvido um procedimento de síntese, empregando um forno de microondas no tratamento hidrotérmico para obtenção da sílica FDU-1. Após tratamento hidrotérmico, as amostras foram calcinadas a 540°C, em duas etapas, empregando atmosferas de N2 e ar. Os materiais foram caracterizados por análise elementar, FTIR, TG, SAXS e Isotermas de adsorção de N2 a 77 K. Os dados de SAXS, associados aos das Isotermas de adsorção de N2, demonstraram que os materiais obtidos com 45 e 60 min de exposição a microondas, apresentaram propriedades texturais compatíveis com aquelas do material obtido pelo método convencional. Os ensaios de termogravimetria evidenciam a faixa de temperatura em que ocorrem as decomposições térmicas do copolímero no material como sintetizado e conduziram a uma otimização das melhores condições para calcinação. As curvas TG/DTG indicaram que no aquecimento dos materiais até 1200ºC, há a transformação completa dos grupos silanóis em siloxanos a partir da eliminação de água. Esse fato é confirmado a partir dos espectros de absorção na região do IV e possibilitou estimar que a quantidade dos grupos Si-OH na superfície do material varia com o tempo de tratamento hidrotérmico na etapa de síntese. / Highly ordered, thermally and hidrotermally stable, with large pore size of 12 nm, caged-like cubic mesoporous silica structures (originally denoted FDU-1) were synthesized from TEOS and poly(ethylene oxide)-poly(butylene oxide)poly(ethylene oxide) B50-6600 triblock copolymer template (EO39BO47EO39) under acidic conditions.The synthesis procedure was developed using microwave oven for hydrothermal treatment to obtain FDU-1 silica. After hydrothermal treatment, the samples were calcined to 540 ºC, in two stages, using N2 and air atmospheres. The materials characterized by elementary analysis, FTIR, TG, DRX and nitrogen adsorption isothermal at 77 K. The data association of SAXS and the nitrogen adsorption isothermal demonstrated that the material isolated with 45 and 60 minutes of the exposition to the microwaves in the hydrothermal treatment showed testure properties compatible to that one of material obtained by the conventional method. Thermogravimetric experiments evidenced the temperature range where occur copolymer thermal decomposition according to the synthesis, as synthesized materials. This information was important to optimize the material calcination conditions. The TG/DTG curves indicated that, in the material heated up to 1200 ºC, occurs complete transformation of silanol in to siloxane groups with water elimination. This fact is confirmed through the IR spectra and enabled to calculate the quantity of the Si-OH groups in the material surface which vary hydrothermal treatment time in the syntesis stage.

Estruturas de sílica mesoporosa cúbica em forma de gaiola (originalmente identificadas como FDU-1) altamente ordenadas, estáveis térmica e hidrotermicamente, com tamanhos de poros da ordem de 12 nm, foram sintetizadas a partir de TEOS e como molde utilizou-se o copolímero tribloco poli(óxido de etileno)-poli(óxido de butileno)-poli(óxido de etileno) 850-6600 (EO39BO47EO39), em meio ácido. Foi desenvolvido um procedimento de síntese, empregando um forno de microondas no tratamento hidrotérmico para obtenção da sílica FDU-1. Após tratamento hidrotérmico, as amostras foram calcinadas a 540°C, em duas etapas, empregando atmosferas de N2 e ar. Os materiais foram caracterizados por análise elementar, FTIR, TG, SAXS e Isotermas de adsorção de N2 a 77 K. Os dados de SAXS, associados aos das Isotermas de adsorção de N2, demonstraram que os materiais obtidos com 45 e 60 min de exposição a microondas, apresentaram propriedades texturais compatíveis com aquelas do material obtido pelo método convencional. Os ensaios de termogravimetria evidenciam a faixa de temperatura em que ocorrem as decomposições térmicas do copolímero no material como sintetizado e conduziram a uma otimização das melhores condições para calcinação. As curvas TG/DTG indicaram que no aquecimento dos materiais até 1200ºC, há a transformação completa dos grupos silanóis em siloxanos a partir da eliminação de água. Esse fato é confirmado a partir dos espectros de absorção na região do IV e possibilitou estimar que a quantidade dos grupos Si-OH na superfície do material varia com o tempo de tratamento hidrotérmico na etapa de síntese. / Highly ordered, thermally and hidrotermally stable, with large pore size of 12 nm, caged-like cubic mesoporous silica structures (originally denoted FDU-1) were synthesized from TEOS and poly(ethylene oxide)-poly(butylene oxide)poly(ethylene oxide) B50-6600 triblock copolymer template (EO39BO47EO39) under acidic conditions.The synthesis procedure was developed using microwave oven for hydrothermal treatment to obtain FDU-1 silica. After hydrothermal treatment, the samples were calcined to 540 ºC, in two stages, using N2 and air atmospheres. The materials characterized by elementary analysis, FTIR, TG, DRX and nitrogen adsorption isothermal at 77 K. The data association of SAXS and the nitrogen adsorption isothermal demonstrated that the material isolated with 45 and 60 minutes of the exposition to the microwaves in the hydrothermal treatment showed testure properties compatible to that one of material obtained by the conventional method. Thermogravimetric experiments evidenced the temperature range where occur copolymer thermal decomposition according to the synthesis, as synthesized materials. This information was important to optimize the material calcination conditions. The TG/DTG curves indicated that, in the material heated up to 1200 ºC, occurs complete transformation of silanol in to siloxane groups with water elimination. This fact is confirmed through the IR spectra and enabled to calculate the quantity of the Si-OH groups in the material surface which vary hydrothermal treatment time in the syntesis stage.