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Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2019. / A shortage of water has resulted in the need to enhance the quality of wastewater that is released into the environment. The advanced oxidation process (AOP) using heterogeneous catalysis is a promising treatment process for the management of wastewater containing recalcitrant pollutants as compared to conventional processes. As AOP is a reliable wastewater treatment process, it is expected to be a sustainable answer to the shortage of clean water. AOP using heterogeneous catalysis based on Co3O4 particles and PMS, in particular has been found to be a powerful procedure for the degradation and mineralization of recalcitrant organic contaminants. In addition, due to the growing application of Co3O4 in lithium batteries, large quantities of these particles will be recovered as waste from spent lithium batteries, so there is a need to find a use for them. Although this method has received some promising feedback, challenges still need to be addressed, such as the toxicity of cobalt particles, the poor chemical and thermal stability and particle aggregation, and the prompting of lower catalytic efficiency in long haul application. Furthermore, the removal of the catalyst after the treatment of pollutants is also an issue. In order to be applicable, a novel catalyst must be produced requiring the combination of Co3O4 with a support material in order to inhibit cobalt leaching and generate better particle stability. From the available literature, TiO2 was found to be the best support material because it not only provides a large surface area for well dispersed Co3O4, but it also forms strong Co-O-Ti bonds which greatly reduced cobalt leaching as compared to other support materials. Moreover, it also greatly encourages the formation of surface Co–OH complexes, which is considered a crucial step for PMS activation. Therefore, the issues cited above could be avoided by producing a Co3O4/TiO2 heterojunction catalyst.

In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 ???/O2 ??????, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 ???/O2 ??????). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by ???OH (HCOO???/CO2 ?????? and 3HGA???2???). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that ???OH and CO3 ?????? are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 ??????, is suggested to be generated by the interaction of ???OH and O2 ?????? with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 ?????? and the previously dismissed ???OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).

In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 ???/O2 ??????, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 ???/O2 ??????). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by ???OH (HCOO???/CO2 ?????? and 3HGA???2???). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that ???OH and CO3 ?????? are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 ??????, is suggested to be generated by the interaction of ???OH and O2 ?????? with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 ?????? and the previously dismissed ???OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).

Orientador: Giuseppina Pace Pereira Lima / Coorientador: Juan Saavedra del Aguila / Banca: Fabio Vianello / Banca: Francisco Artes Calero / Banca: Camila Renata Correa Camacho / Banca: Igor Otavio Minatel / Resumo: O objetivo deste estudo foi verificar a influencia de sanitizantes (ozônio e hipoclorito de sódio) no conteúdo de compostos bioativos e na atividade antioxidante durante o armazenamento refrigerado e na simulação de comercialização de mangas (Mangifera indica L.) 'Palmer' cultivadas em sistema orgânico e convencional e verificar as alterações durante o armazenamento de dois diferentes smoothies. Para atingir esse objetivo a tese foi dividida em cinco capítulos, no primeiro as mangas 'Palmer' orgânicas adquiridas no município de Borborema-SP e as convencionais, doadas pela Ogata Citrus (Taquaritinga-SP) foram transportadas ao laboratório de Bioquímica, onde foram submetidas a quatro tratamentos de imersão: imersão em água; em água clorada com 100 mg L-1 de hipoclorito de sódio por 10 minutos e em água ozonizada por 10 ou 20 minutos. As avaliações foram realizadas após a colheita e aos 7 e 15 dias de armazenamento refrigerado. Aos 7 dias, os frutos foram levados ao ambiente e as avaliações seguiram por 4 e 8 dias, para simular o período de comercialização. Determinaram-se a firmeza da polpa, pH, ácido ascórbico, sólidos solúveis, acidez titulável, polifenóis totais, flavonóides totais, β-caroteno, DPPH e FRAP. As análises microbiológicas foram realizadas após a colheita, aos 7 dias de armazenando refrigerado e aos 7 dias mais 4 em ambiente. O delineamento utilizado foi inteiramente casualizado (DIC) com esquema fatorial 5 x 8 (dias de avaliação x tratamentos) com 3 repetições. Houve uma tendência dos frutos orgânicos e ozonizados apresentarem maiores conteúdos dos compostos bioativos, com isso maior atividade antioxidante, o que evidenciou que o ozônio pode substituir o cloro sem prejuízos aos frutos. No segundo capitulo, foi realizada a quantificação das aminas bioativas das polpas de manga 'Palmer' orgânicas e convencionais, submetidas a ... / Abstract: The aim of this study was to investigate the influence of sanitizers (ozone and sodium hypochlorite) in the bioactive compounds content and antioxidant activity during cold storage and marketing simulation grown in mango (Mangifera indica L.) grown in organic and conventional system and verify changes during storage of two different smoothies. To achieve this thesis objective was divided into five sections, the first the mango 'Palmer' organic acquired in Borborema-SP and conventional, donated by Ogata Citrus (Taquaritinga-SP) were transported to the laboratory of Biochemistry, which were submitted four immersion treatments: immersion in water; in chlorinated water with 100 mg L-1 of sodium hypochlorite for 10 minutes and ozonated water for 10 and 20 minutes. The evaluations were performed after harvest and at 7 and 15 days of cold storage. At 7 days, fruit were taken to the environment and evaluations followed by 4 and 8 days, to simulate marketing period. Were determined firmness, pH, ascorbic acid, soluble solids, titratable acidity, total polyphenols, total flavonoids, β-carotene, DPPH and FRAP. The microbiological analyzes were carried out after harvest, after 7 days of cold storage and 7 days over 4 environment. The design was completely randomized (CRD) with factorial 5 x 8 (day trial x treatments) with three repetitions. There was a trend of organic fruit and ozonated have higher bioactive compounds contents, therefore higher antioxidant activity, which shows that ozone could replace chlorine without damage to fruit. In the second chapter, it performed the bioactive amines quantification of the pulp mango 'Palmer' organic and conventional, undergo four sanitization treatments: immersion in the tap water; in chlorinated water with 100 mg L-1 of sodium hypochlorite for 10 minutes and ozonization for 10 and 20 minutes postharvest and after seven days of cold storage followed by 4 and 8 ... / Doutor

The ever-increasing detection of harmful organic and inorganic compounds in habitable areas throughout the world has led to mounting research into applications and techniques for the treatment of contaminated soils, surface and groundwaters, and chemical and industrial wastewaters. Chemical oxidation technologies, in particular Fenton-based remediation systems, have exhibited considerable potential for the effective treatment and remediation of such contaminated waters and soils. The use of Fenton-based oxidation systems for the treatment of contaminated waters and wastewaters warrants the development of kinetic models capable of accurately simulating system behaviour. In this thesis, the kinetics of Fenton-mediated oxidation systems and kinetic models based on its governing reaction mechanism are investigated in order to highlight those parameters and conditions that effect Fenton chemistry and oxidation performance, and to demonstrate the application of such kinetic models to design and improve treatment systems. Experimental and simulated data describing the oxidation of formic acid by Fenton's reagent at low pH (3 to 4) and under a variety of initial conditions, operating regimes, and solution environments supports a proposed reaction mechanism that nominates the hydroxyl radical (OH) as the active oxidizing intermediate in Fenton-based oxidation systems. Laboratory experiments demonstrate that formic acid oxidation is inhibited in the presence of oxygen, and model simulations of these systems reveals that such behaviour is due to the effect organic radical intermediates and/or by-products have in assisting or hindering the redox cycling of the catalytic iron species. The critical role that iron redox cycling plays in affecting oxidation performance is further highlighted by experimental and simulated studies at alternate pHs and using different target organics, including those that react directly with iron in a redox capacity. Experiments at pH 4 reveal an increase in the redox cycling of iron and improved oxidation performance compared to pH 3 as the higher pH favours the superoxide radical, a stronger reductant than the hydroperoxyl radical that predominates at pH 3. Other laboratory and modelling studies on the Fenton-mediated oxidation of certain aromatic compounds highlight the manner in which quinone and quinone-like compounds, being added directly or generated as oxidation by-products, can improve oxidation performance via redox reactions with iron. Further simulations reveal the type of practical design and operating information kinetic models can provide for treatment processes, though it is noted an appropriate understanding of the oxidation mechanism of the target species is necessary for the accurate application of the model.

The deteriorating water quality in South Africa and changing legislation requiring the industrial implementation of waste minimisation and pollution prevention technologies has highlighted the need for the investigation of new effluent treatment technologies such as advanced oxidation processes. This investigation details the evaluation of ultrasound, an emerging advanced oxidation process, to degrade organic compounds during water treatment. The objectives of the investigation included the design of a suitable ultrasonic laboratory reactor to investigate ultrasound chemistry and the sub-processes occurring during sonication. Atrazine was used as a model compound to compare the performance of ultrasound with that of ozone and hydrogen peroxide, already established advanced oxidation processes. Recommendations have also been made for the scale-up of ultrasonic processes. A 500 mL ultrasonic cell containing an ultrasonic horn as an energy source was designed and constructed. The measurement of hydrogen peroxide concentration was used as a tool to indicate the process conditions under which the formation of free radical reactions during sonication are enhanced. These include the application of oxygen and air sparging or the addition of a commercial source of hydrogen peroxide. It was found that oxygen sparging and a high acoustic power input should be used in ultrasonic processes with a short retention time, and conversely, that air sparging and a lower acoustic energy source should be used in processes with a long retention time. A flow loop system should be considered to maximise oxidation both within and beyond the sonicated zone, gas sparging should only occur within the sonication zone else the degradation of hydrogen peroxide is encouraged. Ultrasound is most effectively applied in water treatment as a pretreatment stage in combination with other technologies and not as a stand-alone process. Atrazine was used. as a model compound to compare the performance of ultrasound with ozone because of its persistence in the environment and resistance to degradation. Atrazine was degraded during sonication and ozonation. degradation increased wim the addition of hydrogen peroxide. Ozone decomposition (and hence free radical reactions) was enhanced when ozone was combined with ultrasound or hydrogen peroxide. Enhanced ozone decomposition during ozonation combined with sonication is due to the conditions (high temperatures and pressures) as well as the free radical reactions occurring within the collapsing cavitation bubbles and at the gas-liquid interface. The enhancing effect of combining ultrasound with ozone was greatest at the low ozone concentrations typically applied during water treatment. Atrazine degradation during sonication and ozonation is predominantly due to the reaction with hydroxyl radicals. Atrazine degradation products identified using gas chromatography and mass spectrometry were deethylatrazine. hydroxyatrazine and deethyldeisopropylatrazine (tentatively identified). / Thesis (Ph.D.)-University of Natal, Durban, 2001.

The ever-increasing detection of harmful organic and inorganic compounds in habitable areas throughout the world has led to mounting research into applications and techniques for the treatment of contaminated soils, surface and groundwaters, and chemical and industrial wastewaters. Chemical oxidation technologies, in particular Fenton-based remediation systems, have exhibited considerable potential for the effective treatment and remediation of such contaminated waters and soils. The use of Fenton-based oxidation systems for the treatment of contaminated waters and wastewaters warrants the development of kinetic models capable of accurately simulating system behaviour. In this thesis, the kinetics of Fenton-mediated oxidation systems and kinetic models based on its governing reaction mechanism are investigated in order to highlight those parameters and conditions that effect Fenton chemistry and oxidation performance, and to demonstrate the application of such kinetic models to design and improve treatment systems. Experimental and simulated data describing the oxidation of formic acid by Fenton's reagent at low pH (3 to 4) and under a variety of initial conditions, operating regimes, and solution environments supports a proposed reaction mechanism that nominates the hydroxyl radical (OH) as the active oxidizing intermediate in Fenton-based oxidation systems. Laboratory experiments demonstrate that formic acid oxidation is inhibited in the presence of oxygen, and model simulations of these systems reveals that such behaviour is due to the effect organic radical intermediates and/or by-products have in assisting or hindering the redox cycling of the catalytic iron species. The critical role that iron redox cycling plays in affecting oxidation performance is further highlighted by experimental and simulated studies at alternate pHs and using different target organics, including those that react directly with iron in a redox capacity. Experiments at pH 4 reveal an increase in the redox cycling of iron and improved oxidation performance compared to pH 3 as the higher pH favours the superoxide radical, a stronger reductant than the hydroperoxyl radical that predominates at pH 3. Other laboratory and modelling studies on the Fenton-mediated oxidation of certain aromatic compounds highlight the manner in which quinone and quinone-like compounds, being added directly or generated as oxidation by-products, can improve oxidation performance via redox reactions with iron. Further simulations reveal the type of practical design and operating information kinetic models can provide for treatment processes, though it is noted an appropriate understanding of the oxidation mechanism of the target species is necessary for the accurate application of the model.

Made available in DSpace on 2016-06-07T17:12:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-12-09. Added 1 bitstream(s) on 2016-06-07T17:17:17Z : No. of bitstreams: 1 000865160.pdf: 1577133 bytes, checksum: fa6f674f6ae9f7985a865454ae460228 (MD5) / O objetivo deste estudo foi verificar a influencia de sanitizantes (ozônio e hipoclorito de sódio) no conteúdo de compostos bioativos e na atividade antioxidante durante o armazenamento refrigerado e na simulação de comercialização de mangas (Mangifera indica L.) 'Palmer' cultivadas em sistema orgânico e convencional e verificar as alterações durante o armazenamento de dois diferentes smoothies. Para atingir esse objetivo a tese foi dividida em cinco capítulos, no primeiro as mangas 'Palmer' orgânicas adquiridas no município de Borborema-SP e as convencionais, doadas pela Ogata Citrus (Taquaritinga-SP) foram transportadas ao laboratório de Bioquímica, onde foram submetidas a quatro tratamentos de imersão: imersão em água; em água clorada com 100 mg L-1 de hipoclorito de sódio por 10 minutos e em água ozonizada por 10 ou 20 minutos. As avaliações foram realizadas após a colheita e aos 7 e 15 dias de armazenamento refrigerado. Aos 7 dias, os frutos foram levados ao ambiente e as avaliações seguiram por 4 e 8 dias, para simular o período de comercialização. Determinaram-se a firmeza da polpa, pH, ácido ascórbico, sólidos solúveis, acidez titulável, polifenóis totais, flavonóides totais, β-caroteno, DPPH e FRAP. As análises microbiológicas foram realizadas após a colheita, aos 7 dias de armazenando refrigerado e aos 7 dias mais 4 em ambiente. O delineamento utilizado foi inteiramente casualizado (DIC) com esquema fatorial 5 x 8 (dias de avaliação x tratamentos) com 3 repetições. Houve uma tendência dos frutos orgânicos e ozonizados apresentarem maiores conteúdos dos compostos bioativos, com isso maior atividade antioxidante, o que evidenciou que o ozônio pode substituir o cloro sem prejuízos aos frutos. No segundo capitulo, foi realizada a quantificação das aminas bioativas das polpas de manga 'Palmer' orgânicas e convencionais, submetidas a ... / The aim of this study was to investigate the influence of sanitizers (ozone and sodium hypochlorite) in the bioactive compounds content and antioxidant activity during cold storage and marketing simulation grown in mango (Mangifera indica L.) grown in organic and conventional system and verify changes during storage of two different smoothies. To achieve this thesis objective was divided into five sections, the first the mango 'Palmer' organic acquired in Borborema-SP and conventional, donated by Ogata Citrus (Taquaritinga-SP) were transported to the laboratory of Biochemistry, which were submitted four immersion treatments: immersion in water; in chlorinated water with 100 mg L-1 of sodium hypochlorite for 10 minutes and ozonated water for 10 and 20 minutes. The evaluations were performed after harvest and at 7 and 15 days of cold storage. At 7 days, fruit were taken to the environment and evaluations followed by 4 and 8 days, to simulate marketing period. Were determined firmness, pH, ascorbic acid, soluble solids, titratable acidity, total polyphenols, total flavonoids, β-carotene, DPPH and FRAP. The microbiological analyzes were carried out after harvest, after 7 days of cold storage and 7 days over 4 environment. The design was completely randomized (CRD) with factorial 5 x 8 (day trial x treatments) with three repetitions. There was a trend of organic fruit and ozonated have higher bioactive compounds contents, therefore higher antioxidant activity, which shows that ozone could replace chlorine without damage to fruit. In the second chapter, it performed the bioactive amines quantification of the pulp mango 'Palmer' organic and conventional, undergo four sanitization treatments: immersion in the tap water; in chlorinated water with 100 mg L-1 of sodium hypochlorite for 10 minutes and ozonization for 10 and 20 minutes postharvest and after seven days of cold storage followed by 4 and 8 ...

The fate of iron complexed by various organic compounds was investigated as a function of both chemical oxidative and coagulation removal methods. Dissolved organic carbon (DOC) utilized in the studies was obtained from a variety of sources and included humic and fulvic acids, tannic acid and oxalic acid. Oxidants evaluated were potassium permanganate, free chlorine, and chlorine dioxide. Both laboratory-scale and field monitoring studies were performed. The relative molecular weight distribution (MWD) of the DOC present was analyzed to evaluate how changes in this parameter affected the efficiency of soluble iron removal by oxidation. In addition, the MWD of selected coagulated samples was evaluated to determine how this parameter affected the fate of complexed iron during the coagulation of dissolved organic matter with alum. A high degree of ferrous iron complexation occurred with the DOC dominated by higher molecular weight organics. This complexation rendered the iron stable against the addition of each of the oxidants evaluated. However, soluble Fe(II) complexed by low molecular weight organics was successfully removed by chemical oxidation. Potassium permanganate was found to be the most effective oxidant of the three oxidants utilized in the study. The results indicated that soluble Fe(II) complexed by high molecular weight DOC can be efficiently removed by alum coagulation. The pH and alum dose utilized to produce effective DOC removal was also found to promote efficient complexed Fe(II) removal. / Master of Science