L’oxyde de zinc (ZnO) est un semi-conducteur II-VI remarquable et très prometteur dans le développement des nouveaux matériaux pour l’énergie renouvelable et pour l’environnement. ZnO est l’un des rares matériaux multifonctionnels. Grâce à ses nombreuses propriétés physiques, chimiques et optoélectroniques très intéressantes, lui confèrent d’être un matériau utilisé dans différents domaines d’applications telles que les cellules solaires, les diodes électroluminescentes, les capteurs de gaz, la dépollution de l’eau et de l’air par effet photocatalytique, etc.Dans cette thèse, nous nous sommes intéressés tout d’abords à optimiser l’élaboration de nanofils de ZnO (ZnO NWs) par méthode hydrothermale. Un procédé à deux étapes a été optimisé qui nous a permis d’obtenir des nanofils de ZnO ayant des excellentes propriétés morphologiques et structurales, avec une très bonne reproductibilité. Une nouvelle méthode d’élaboration, dite Electrospinning, a été mise au point. Ce procédé nous permet d’obtenir des micro- et nanofibres contenant des nanocristallites de ZnO. La combinaison des deux méthodes de synthèse nous a permis d’obtenir des nanostructures hiérarchiques de ZnO (NWs/NFs) possédant une surface effective beaucoup plus importante que la nanostructure classique (ZnO NWs).Deux applications ont été développées dans cette thèse. Dans un premier temps, des tests de détection de trois gaz réducteurs ont été réalisés sur les deux types de nanostructures de ZnO. Par la suite, une étude de purification de l’eau par effet photocatalytique a été réalisée sur un réseau de nanofils de ZnO sous irradiation UV pour les trois colorants (MB, MO et AR14). Afin d'améliorer la performance de la photocatalyse, deux nouvelles méthodes ont été développées. La première consiste à mettre en place un système microfluidique en utilisant des microréacteurs contenant des nanofils de ZnO comme photocatalyseur permettant ainsi à raccourcir considérablement le temps de dépollution. La seconde méthode est basée sur un procédé de dopage de ZnO permettant ainsi d’améliorer l'efficacité de la photocatalyse / Zinc oxide (ZnO) is a remarkable and very promising wide-gap II-VI semiconductor in the development of new materials for renewable energy and for the environment. Thanks to its many interesting physical, chemical and optoelectronic properties, this multifunctional material is used in many application fields such as solar cells, light emitting diodes, gas sensors, and water & air purification by photocatalytic effect, etc.In this thesis, we were interested in optimizing the synthesis of ZnO nanowires (ZnO NWs) by hydrothermal method. A two-step process has been optimized allowing us to obtain ZnO NWs having excellent morphological and structural properties, with very good reproducibility. A new synthesis method “Electrospinning” has been developed and the micro- & nanofibers containing ZnO nanocristallites can be obtained by this process. The combination of the two synthesis methods results a hierarchical nanostructure of ZnO (NWs/NFs) with an effective surface much larger than the classical one (ZnO NWs).Two applications have been developed in this thesis. Firstly, three reducing gases sensing tests have been carried out on the two types of ZnO nanostructures. Then, a photocatalytic water purification study has been carried out on a ZnO nanowire array under UV irradiation for the three dyes (MB, MO and AR14). In order to improve the photocatalysis performance, two new methods have been developed. The first is to set up a microfluidic system using microreactors containing ZnO NWs as a photocatalyst, thus the depollution time has been considerably shortened. The second method is based on the ZnO doping in order to improve the photocatalysis efficiency

Submitted in fulfilment of the requirements for the Degree of Master of Engineering, Durban University of Technology, 2017. / In this research, the woven fibre microfiltration (WFMF) fabric which is produced locally in South Africa is used as a membrane material. It is cheaper in price in comparison with the current commercial membrane materials that are in use. The WFMF is also more robust when compared with the commercial membrane materials thus is able to withstand harsh working conditions. From previous studies on the WFMF, it has been shown that it can be used as a membrane material without any compromise to permeate quality. This research seeks to optimize the working conditions of this membrane material (WFMF) with an aim of achieving lower running costs and better anti fouling strategies in comparison to the commercial MBRs. The objectives and aims of this research was to come up with a MBR system whose running cost is lower than that for the commercial systems, which can be adapted for use in any environment, especially in the hardship regions where its robustness would be an added advantage. The performance of the WFMF submerged MBR was also optimised including antifouling operating regimes. This study was done in a pilot plant that was set up at Veolia wastewater treatment plant, Durban Metro Southern Works. The feed water for the pilot plant was pumped from the return activated sludge mixing chamber by means of a submersible pump. The MLSS concentration of the feed water was about 12 g/l. The various investigations that were conducted in the course of this research included the effect of spacing between membrane modules, relaxation steps and frequencies, evaluation of aeration rates and evaluation of coarse vs. fine bubbles which were all aimed at optimizing the performance of the immersed WFMF MBR. The permeate was checked for turbidity and COD levels to ensure that they were within the accepted water standards. From the experiments it is shown that the critical flux increased with an increase in aeration rate which is in concurrence with the literature and a starting flux of 30 LMH was chosen for the running of the pilot plant for the various experimental runs to be carried out. For the pipe diffuser height effect experimental run, the best results were achieved at a height of 5 cm below the membrane modules and the use of a pipe diffuser gave better results than the use of a disc diffuser. For the membrane module spacing effect the best results were obtained at the smallest possible width i.e. 3.5 mm. The best relaxation step sequence was found to be 9 mins on and 1 min off. COD, turbidity and DO was continuously determined during the course of the experimentation. Further studies should be done on use of the disc diffuser with increased surface area of aeration holes and also hole sizes of smaller diameters to check on its effectiveness as a means of reducing fouling on the membrane surface. / M

M.Sc. / The contamination of water by toxic compounds is one of the most serious environmental problems today. These toxic compounds mostly originate from industrial effluents, agriculture runoff, natural sources (e.g. heavy metals in water from rocks and soil erosion) and human waste. The contamination, which is both “organic” and “inorganic” has an impact on the environment and human health. The demand for water and the pressure to re-use this valuable resource has increased the need for improved techniques and materials to remove pollutants from water. The Nanomaterials Science research group at the University of Johannesburg has focused on developing synthetic polymers that can be employed in water treatment and pollutant monitoring. Recently, cyclodextrins (CD) and carbon nanotubes (CNTs) have been included in polymers for this application. For example, CD-co-hexamethylene-/toluene-diisocyanate polyurethanes and CNT-modified equivalents have been developed and have been successfully applied in removing organic contaminants from water to very low levels.1 Calixarenes are synthetic analogues of cyclodextrins that can be exploited via chemical modification to express a range of properties. In the present study, calixarenes, thiacalixarenes and carbon nanotube-based polymeric materials incorporating these molecules have been synthesised, characterised and tested for removing both organic pollutants (such as p-nitrophenol) and inorganic pollutants (Cd2+, Pb2+) from water. Lead(II) and Cadmium(II) are a threat in South Africa because of their toxicity, and while p-nitrophenol is much less of a problem it represents a useful model organic pollutant. The absorption capacity of the polymers towards heavy metals and organic contaminants was tested by mixing the polymer with synthetic water containing known concentration of the contaminants at about 10 mg/L. Atomic absorption spectrometry (AAS) and ultraviolet-visible spectrometry (UV-vis) were used to determine the levels of heavy metals and organic contaminants, respectively. The target pollutants (Cd2+, 1 see KL Salipira MTech dissertation, University of Johannesburg 2008 Pb2+ and p-nitrophenol) were all successfully removed from water by the various polymers, however the degree of removal and loading capacities of the polymers differed. This information gives some insight into what functional components are needed for making successful adsorbents. It was observed, for example, that ptert- butylcalix[8]arene/hexamethylene diisocyanate (C8A/HMDI) had a higher adsorption capacity towards p-nitrophenol and Pb2+ than towards Cd2+, and also a higher capacity than the corresponding calix[4]arene polymers with smaller calixarene cavities.

Abstract available in file 07summary.pdf / Thesis (PhD (Microbiology))--University of Pretoria, 2007. / Microbiology and Plant Pathology / unrestricted

No description available.

Excess fluoride (F-) in drinking water poses a health threat to millions of people around the world. In the present work, activated alumina (AA) has been used as an adsorbent. Data obtained from batch experiments were fitted to the (i) pseudo-first order, (ii) pseudo-second order, and (iii) Langmuir kinetic model. Model (ii) performed better than model (i), and fitted the data well. However, the rate constant for adsorption ka had to be varied as a function of the initial concentration of F- in the liquid phase c0. A more satisfactory approach is provided by Langmuir model, which fitted the data reasonably even though ka was independent of c0. Shreyas (2008) developed a model for the batch adsorption of F- onto porous pellets of AA. Some errors were detected in his computer program were corrected. The parameters of the model were estimated by fitting predictions to data. The parameter values suggest that the adsorption process is likely to be diffusion limited. Column experiments were conducted as follows. The pellets were soaked in deionized water for a time ts before they were loaded into columns. A feed solution having a fluoride concentration cf = 3 mg/L was fed to column and the concentration of F- in the exit stream ce was measured at regular intervals. Breakthrough was deemed to have occurred when ce exceeded the permissible limit (= 1 mg/L). Constant values of the bed height H, and the empty bed contact time tc were used in the experiments. The volume of treated water V, scaled by the volume of the bed Vb, varied strongly with the soaking time ts, with a maximum at ts = 24 h. To understand the possible reasons for this behaviour, XRD, FESEM, and FTIR were used to characterize the surface of AA. Though the concentrations of the surface hydroxyl groups may influence the adsorption of F-, FTIR studies show there is no direct correlation between V/Vb and the concentrations of these groups. The FESEM and XRD studies indicate that fresh AA consists mainly of boehmite, which gradually converted to gibbsite during soaking. For fixed values of H and tc, the dimensionless volume of treated water V/Vb was a maximum at D = 45 mm. This behaviour may be caused by wall effects for small values of D and by occurrence of quasi-static regions near the wall for large values of D. The cost of treated of water was Rs. 0.42/L. It decreased slightly to Rs. 0.37/L after one regeneration cycle, but increased to Rs. 0.41/L after two cycles. The volume of treated water after two regeneration cycles was 595 L/kg. The concentration of Al3+ ions ca in the treated water increased and exceeded the permissible limit of 0.2 mg/L as the number of regeneration cycles increased. The concentration of F- in regeneration effluent cre was in the range 32-70 mg/L. The effluent was subjected to solar distillation, leading to a distillate whose fluoride concentration F- was in the range 9-12 mg/L. The distillate can be discharged into the public sewers, as the permissible limit is 15 mg/L.

Made available in DSpace on 2017-06-01T18:20:28Z (GMT). No. of bitstreams: 1 dissertacao_andrea_costa.pdf: 1097191 bytes, checksum: 2034dceff8e34b803bcf36f5c6ab617c (MD5) Previous issue date: 2008-05-29 / The industrial effluents with dyes are recalcitrant pollutants exhibiting toxicity to the living being and are difficult to remove by conventional processes. The treatment process of jeans uses large volumes of water and various chemicals, including synthetic dyes. This study investigated the influence of biological and physico-chemical factors in the removal of color and turbidity in the effluent treatment from laundry and dyeing industries. Factorial designs with central point were used in biodegradation and coagulation-flocculation treatments using analysis of interactions between the investigated factors. The independent variables were microbial consortium, aeration, agitation, tannin and the floculation polymer (POLICAP - 32) concentrations, whereas the response variables were color and turbidity. The microbial consortium with capacity of dye decolorization was obtained from the effluent in the absence of nutrients at 28 to 30 ° C, aeration of 1 vvm under agitation of 150 rpm. The biological treatment of the effluent occurred during 48 hours. In the experimental design of the biodegradation, the aeration and the increase of the agitation unfavored significantly the decolorization. The higher removal of color was obtained from the central point of the factorial design 1.25 % v/v consortium concentration and 50 rpm agitation. In this condition, the color average reached approximately 138 mgPt/L, corresponding to a decolorization of the untreated effluent of approximately 90 %. In the physico-chemical treatment, the increase of the tannin concentration and the interactions between tannin and polymer concentrations significantly favored the decolorization of the effluent. The higher removal of color and further reduction of turbidity were obtained at the central point of the factorial design 0.3 g/mL tannin concentration, 15 ppm polymer floculation at pH 7.5 for 20 minutes. In this experimental condition, the average color was approximately 50 mgPt/L and the average turbidity, approximately 4 NTU. The decolorization reached 96 % and the turbidity reduction, 79 % of the untreated effluent in the physical-chemical treatment / Os corantes presentes em efluentes industriais são poluentes recalcitrantes que apresentam toxicidade aos seres vivos e são de difícil remoção por tratamentos convencionais. O processo de beneficiamento de jeans utiliza grande volume de água e produtos químicos diversos, incluindo os corantes sintéticos. O presente estudo investigou a influência de fatores biológicos e físico-químicos na remoção de cor e turbidez em tratamentos de efluentes de lavanderia e tinturaria industriais. Planejamentos fatoriais com ponto central foram empregados em biodegradações e em tratamentos por coagulação-floculação, utilizando delineamento experimental com análise de interação entre os fatores investigados. As variáveis independentes foram consórcio microbiano, aeração, agitação, concentrações de tanino e do polímero auxiliar de floculação (POLICAP - 32) sobre as variáveis respostas, cor e turbidez. O consórcio microbiano com capacidade de descolorir corantes foi obtido a partir do efluente na ausência de nutrientes, a 28 - 30 ºC, sob agitação de 150 rpm e aeração de 1 vvm. No tratamento biológico, a aeração e o aumento da agitação desfavoreceram significativamente a descoloração; a maior remoção de cor foi obtida no ponto central do planejamento - concentração do consórcio a 1,25 % v/v e agitação de 50 rpm. Nessa condição experimental, a cor média atingiu aproximadamente 138 mgPt/L, correspondendo a uma descoloração do efluente não tratado de cerca de 90 %. No tratamento físico-químico, o aumento da concentração de tanino e a interação entre as concentrações de tanino e do polímero favoreceram significativamente a descoloração do efluente. A maior remoção de cor e redução de turbidez foram obtidas no ponto central do planejamento - concentração do tanino 0,3 g/mL, polímero auxiliar de floculação 15 ppm em pH 7,5 durante 20 minutos. Nessa condição experimental, a cor média foi aproximadamente 50 mgPt/L e a turbidez média, aproximadamente 4 UNT. A descoloração atingiu 96 % e a redução de turbidez, 79 % do efluente não tratado no tratamento físico-químico

Submitted by Biblioteca Central (biblioteca@unicap.br) on 2017-12-04T18:01:57Z No. of bitstreams: 1 pedro_manoel_araujo_santana.pdf: 1113895 bytes, checksum: aa89178214fa87d770781fc12019f31b (MD5) / Made available in DSpace on 2017-12-04T18:01:57Z (GMT). No. of bitstreams: 1 pedro_manoel_araujo_santana.pdf: 1113895 bytes, checksum: aa89178214fa87d770781fc12019f31b (MD5) Previous issue date: 2017-02-21 / Industrial processes have historically been an important factor in environmental degradation. Improper disposal of industrial waste containing potentially toxic metals in water supplies is a major physical, biotic and anthropic problem. The objective of this study was to evaluate the adsorptive capacity of the ground seeds of Moringa oleifera Lam. As an alternative material to synthetic biosorbents for removal of cadmium ions in water. Before and after the treatments were carried out chemical analysis according to official methodology. The results were analyzed by ANOVA and Pearson table chart with a significance level of 5% and correlation between variables. The results showed a better performance of the alternate method, employing pitcher for removing cadmium in water treatment under the following conditions: slightly basic pH (7.11); Contact time between pitcher and water was six hours; moringa one gram per liter of water. Under these conditions there was a reduction in the concentration of 70.28% cadmium proving that the alternative methodology in addition to being inexpensive, easy to perform, helps to minimize severe impacts that metal brings to people's health and the environment. / Os processos industriais têm sido historicamente um importante fator de degradação ambiental. A disposição inadequada de resíduos industriais contendo metais potencialmente tóxicos em fontes de águas representa um grande problema físico, biótico e antrópico. O objetivo deste trabalho foi avaliar a capacidade adsortiva das sementes trituradas de Moringa oleifera Lam. como um material alternativo aos biossorventes sintéticos, para remoção de íons cádmio em águas. Antes e após os tratamentos foram realizadas determinações químicas de acordo com metodologia oficial. Os resultados foram analisados pela tabela ANOVA e o gráfico de Pearson com um nível de significância de 5 % e correlação entre as variáveis. Os resultados mostraram a melhor eficiência do método alternativo, empregando moringa, para remoção de cádmio, em tratamento de água nas seguintes condições: pH levemente básico (7,11); tempo de contato entre moringa e água de seis horas; um grama de moringa por litro de água. Nestas condições houve uma redução da concentração do cádmio de 70,28 % comprovando que a metodologia alternativa além de ser barata, de fácil execução, contribui para minimizar severos impactos que esse metal traz para a saúde das pessoas e para o ambiente.

Submitted by Biblioteca Central (biblioteca@unicap.br) on 2018-11-20T18:51:24Z No. of bitstreams: 2 renata_kelly_lima_santana.pdf: 1101025 bytes, checksum: a6b7adb81731f8710c249fee6ad58062 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-11-20T18:51:24Z (GMT). No. of bitstreams: 2 renata_kelly_lima_santana.pdf: 1101025 bytes, checksum: a6b7adb81731f8710c249fee6ad58062 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-11-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / A methodology was developed for the treatment of an effluent from the metalworking industry composed of water, cutting fluid and graphite. The recovery of components from an effluent from the machining process becomes complex due to the coexistence of solids such as graphite, mixed with a water-oil emulsion. Due to the use of graphite in very small particles and emulsified in water with the aid of an emulsifier, distributing in both phases (aqueous and organic), making the treatment process difficult. In general, treating such an effluent requires, in the preliminary step, the breaking of the emulsion so that the graphite dispersed in the liquid medium is recovered. The treatment was initially performed in a prototype phase separation in laboratory scale, counting on recirculation tanks, pumps, hydrocyclones and continuous decanter. In an initial stage the effluent was acidified by the addition of sulfuric acid PA as a way of breaking the solid-liquid emulsion. Subsequently, the solid phase was reered with the aid of a hydrocyclone, resulting in an overflow of the equipment of a mixture of water and residual oil. The mixture of part of the water and the water-cutting fluid, after acid destabilization of the emulsion, was separated into the continuous decanter, giving rise to a stream of cutting fluid and an aqueous phase containing residual oil, contaminated by about 130 ppm Of organic phase. The aqueous phase was then subjected to a dissolved air flotation (FAD) process, aided by a demulsifying biosurfactant in a FAD prototype, also on a laboratory scale. In order to define adequate conditions to obtain an aqueous phase with contamination level that allowed its return to the process, the operational conditions of application of the FAD technique were determined with the aid of an experimental design of the type rotational central compost (CDCR). At the end of the aqueous phase recovery process, a residual oil content of 12% was obtained, below that required by the Brazilian environmental regulatory agency (CONAMA) for discharge in water bodies, which is 20 ppm. The recoveries of graphite and cutting fluid are suggested studies for the next works. / Foi desenvolvida uma metodologia para tratamento de um efluente da indústria metalmecânica composto de água, fluido de corte e grafite. A recuperação de componentes de um efluente do processo de usinagem torna-se complexa devido à coexistência de sólidos como o grafite, misturado a uma emulsão do tipo água-óleo. Devido ao uso do grafite em partículas muito pequenas e emulsionado em água com auxílio de um emulsificante, distribuindo-se em ambas as fases (aquosa e orgânica), dificultando o processo de tratamento. De modo geral o tratamento de um efluente desse tipo exige, na etapa preliminar, a quebra da emulsão para que seja recuperado o grafite disperso no meio líquido. O tratamento foi inicialmente realizado em um protótipo de separação de fases em escala de laboratório, contando com tanques de recirculação, bombas, hidrociclones e decantador contínuo. Numa etapa inicial o efluente foi acidificado através da adição de ácido sulfúrico PA como forma de quebrar a emulsão sólido-líquido. Posteriormente, foi recuperada a fase sólida com auxílio de um hidrociclone, dando origem a uma descarga pelo overflow do equipamento de uma mistura de água e óleo de corte residual. A mistura de parte da água e do água-fluido de corte, após a desestabilização ácida da emulsão, foi separada no decantador contínuo, dando origem a uma corrente de fluido de corte e uma fase aquosa contendo óleo residual, contaminada por cerca de 130 ppm de fase orgânica. A fase aquosa foi então submetida a um processo de flotação por ar dissolvido (FAD), auxiliada por biossurfactante desemulsificante em um protótipo FAD, também em escala de laboratório. Para definir condições adequadas à obtenção de uma fase aquosa com nível de contaminação que permitisse seu retorno ao processo, as condições operacionais de aplicação da técnica de FAD foram determinadas com auxílio de um planejamento experimental do tipo Delineamento Compost Central Rotacional (DCCR). Ao final do processo de recuperação da fase aquosa foi obtido um teor óleo residual de 12 %, abaixo do exigido pelo órgão brasileiro de regulamentação ambiental (CONAMA) para descarte em corpos hídricos, que é de 20 ppm. As recuperações do grafite e do fluido de corte são estudos sugeridos para os próximos trabalhos.

Membrane-based filtration and separation processes are widely used in various fields, such as for clean drinking water, food, dairy industry, medical, biotechnology, and environmental applications. Providing clean and safe drinking water has been regarded as one of the global biggest challenges because of increasing world population, impacts of climate changes, increased wastewater production, and increased contamination of surface and groundwater. The most important technologies contributing substantially in this field are based on pressure-driven membrane technologies such as microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. Recently, in situ synthesis of nanoparticles based on molecular level design and tailoring in the membrane matrix have been reported to prepare next generation nano-enhanced membranes. In this work similar technique was utilized to construct PSF-Silica nanocomposite membranes in which hydrolysis and condensation of silica precursor (TEOS, APTES, and TPAPS) and phase inversion of polymer film was achieved simultaneously in one step under acidic condition. This unique process has led to the formation of extremely small silica nanoparticles with high dispersion in every region of the membrane. Such type of distribution of silica nanoparticles is very difficult to achieve using conventional silica nanoparticle blending with polymer solution. The prepared membranes were extensively characterized for their morphology, surface properties, nanoparticle distribution, fouling and permeation properties. Finally, the membranes were tested with rejection experiments with protein and dye solutions to assess their usefulness for water filtration and separation applications. The silica nanoparticles were mostly generated during the phase inversion under acidic condition by hydrolysis and polycondensation reaction of silica precursors mixed with PSF solution. The properties and structure of membranes were characterized by different analytic and physicochemical techniques. The prepared membranes exhibit an asymmetric nature with a dense skin layer, followed by finger-like porous structure at the bottom. The microscopic and elemental analysis confirmed the presence and homogeneous distribution of nanoscopic small silica particles throughout the membrane matrix. Hydrophilic SiO2, SiO2-NH2, SO2-NH-SO3H nanoparticles were respectively formed in situ within PSF membrane matrix during the phase inversion under acidic condition by hydrolysis and polycondensation reaction of corresponding silica precursors mixed with PSF solution. Because the nanosize and good distribution of the pores, the presence and well distribution of silica nanoparticles, the presence and exposure of the hydrophilic charged functional groups form a hydrate layer on the membranes and provide hydration repulsion and electrostatic repulsion against solutes from feed under aqueous medium, the PSF-TEOS, PSF-APTES, PSF-TPAPS membranes respectively with SiO2, SiO2-NH2, and SO2-NH-SO3H nanoparticles exhibited high hydrophilicity, stability, water permeation, rejection, and antifouling performance as compared to the neat PSF membrane for water purification application. The overall membrane properties were highly dependent on the concentration of the silica nanoparticles and can be tuned by adjusting the concentration of initial silica precursors during membrane formation. The low protein fouling, high water permeation, protein rejection, and flux recovery results make those membranes attractive for separation and filtration applications. Thus, the prepared membranes can be used in different applications ranging from separation of biomolecules, desalination/purification of water, and for other charge and size-based separation processes.