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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Investigation Of Zinc And Lead Removal From Aqueous Solutions Using Clinoptilolite

Morali, Nihan 01 January 2006 (has links) (PDF)
Natural zeolites, especially clinoptilolite, have the ability of removing certain cations from wastewater by utilizing ion exchange and adsorption. In this study, clinoptilolite originated from Bigadi&ccedil / , Balikesir deposit was investigated in its natural and conditioned form for its effectiveness in removing Zn2+ and Pb2+ ions from aqueous solutions. In addition, relevant mechanisms involved in heavy metal removal by clinoptilolite were examined in this study. Throughout this work, equilibrium and kinetic studies were performed with as-received and conditioned clinoptilolite, having particle size of 0.15 &ndash / 0.80 mm. Conditioning aimed to replace exchangeable cations (Na+, K+, Ca2+, Mg2+) on clinoptilolite with a cation that is more willing to undergo ion exchange. The results of equilibrium studies revealed that clinoptilolite had different capacities for Zn2+ and Pb2+ ions. Clinoptilolite had high capacity for Pb2+ ions, whereas lower capacities were attained for Zn2+. Conditioning with concentrated NaCl solution increased the removal capacity for both metals. Maximum capacities attained were 0.14 meq/g (as-received) and 0.39 meq/g (conditioned) for Zn2+, and 0.51 meq/g (as-received) and 1.10 meq/g (conditioned) for Pb2+. Furthermore, kinetic studies performed under pH-uncontrolled and pH-controlled conditions revealed that heavy metal removal can not only be explained by ion exchange. These studies also indicated that Zn2+ ions were weakly bound to clinoptilolite structure, whereas there was a strong bonding between Pb2+ ions and clinoptilolite structure. To examine possible removal mechanisms, relationship between exchangeable ions released from clinoptilolite structure and Zn2+ and Pb2+ ions removed from aqueous solutions were investigated during equilibrium and kinetic studies. For equilibrium studies, it was observed that the higher the heavy metal equilibrium concentration, the higher is the amount of exchangeable ions released. However, the results indicated that the release of exchangeable ions were not only due to ion exchange. Examination of Si4+, the main central metal ion of clinoptilolite, during kinetic studies showed that destruction of clinoptilolite framework was partly responsible for the release of exchangeable ions. Release of Si4+ was more pronounced in Pb2+ removal studies, indicating dependency of framework destruction on the type of heavy metal species.
312

Magnesium in hemipelagic environments : surface reactions in the sediment-pore water system

von Breymann, Marta T. 18 November 1987 (has links)
Graduation date: 1988
313

Treatment of Reverse Osmosis Concentrates from Recycled Water

Arseto Yekti Bagastyo Unknown Date (has links)
Water recycling by membrane treatment is widely accepted as a leading alternative water source. This separation process creates a concentrated stream (called concentrates), containing most of the pollutants in 10%-20% of the flow; and a treated water stream. As nitrogen is a major concern, environmental regulations have become more stringent, requiring additional treatment to meet effluent standards. Other concerns include organic contaminants and potential production of halogenated organics if disinfection of the reject was applied. One option to address the problem of dissolved organic nitrogen and carbon is advanced oxidation. This oxidation could lead to degradation of refractory organic materials, which are poorly removed in conventional treatment. This project aims to evaluate treatment extent and cost of alternatives for organic (particularly nitrogen) removal in reject water addressing the following research gaps: (i) identifying the key organic pollutants present in the concentrated stream, (ii) the effectiveness and optimisation of coagulation, ion exchange and advanced oxidation; (iii) apparent cost of the different treatment methods. The untreated reverse osmosis concentrates were collected from two treatment plants:- Luggage Point, and Bundamba, both near Brisbane, Queensland, Australia. The first contains more colourful of organics than the second plant. Stirred cell fractionation with ultrafiltration membranes was used to characterise the removed key pollutants, as it offers better accuracy and reproducibility compared to centrifugation fractionation. Fluorescence spectral was used to monitor and identify specific organic compounds. The largest fraction was smaller sized <1kDa. This is probably small humic substances and fulvic acids, as indicated by Excitation Emission Matrix (EEM) analysis. A smaller portion of soluble microbial products (SMPs) also contributes to the concentrates. Bundamba contains large non coloured organics including organic nitrogen with elevated ammonia-N. In contrast, Luggage Point has higher colour, inorganic carbon and conductivity with less ammonia-N. Advanced Oxidation Process (AOP) was the most effective treatment method (high removal of organics, e.g. 55% COD of initial), followed by magnetised ion exchange (MIEX) and coagulations. For UV/H2O2 AOP, the optimal operating condition 400mg.L-1 H2O2 and 3.1kWh.m-3 energy input resulted in organics removals up to 55% with complete decolourisation. The effective reduction was found in all size ranges, preferably in >1kDa. Low inorganic carbon and salinity in Bundamba may allow better overall oxidation rates. MIEX also performed better in Bundamba with organic removals up to 43% and 80% decolourisation at the optimum resin dose of 15mL.L-1. Removal was preferential in size range of >3kDa, with more proportional percentage for decolourisation. Similarly, ferric coagulation removed a wider size range of organics. Further, ferric achieved better organic removal in Luggage Point with up to 49%. At the same molar dose (1.5mM), ferric is superior to alum, especially in Bundamba where there were less hydrophobic compounds according to EEM. Alum is poor for treatment of high organics with less coloured water. MIEX with an operational cost (chemicals and power only) of $0.14-$0.20.m-3 treated water seemed to be the most effective treatment overall. The resin achieved better results with a slightly higher cost than coagulation, and had a lower environmental impact due to reduced sludge production. AOP offers better treatment, but at a higher cost ($0.47.m-3 treated). Combined alternatives may benefit the removal effectiveness. Furthermore, more specific identification of contaminants should be investigated separately to choose appropriate treatment for priority chemicals. Another issue is further investigation of costing, including capital, and full environmental impact of treatment.
314

Treatment of Reverse Osmosis Concentrates from Recycled Water

Arseto Yekti Bagastyo Unknown Date (has links)
Water recycling by membrane treatment is widely accepted as a leading alternative water source. This separation process creates a concentrated stream (called concentrates), containing most of the pollutants in 10%-20% of the flow; and a treated water stream. As nitrogen is a major concern, environmental regulations have become more stringent, requiring additional treatment to meet effluent standards. Other concerns include organic contaminants and potential production of halogenated organics if disinfection of the reject was applied. One option to address the problem of dissolved organic nitrogen and carbon is advanced oxidation. This oxidation could lead to degradation of refractory organic materials, which are poorly removed in conventional treatment. This project aims to evaluate treatment extent and cost of alternatives for organic (particularly nitrogen) removal in reject water addressing the following research gaps: (i) identifying the key organic pollutants present in the concentrated stream, (ii) the effectiveness and optimisation of coagulation, ion exchange and advanced oxidation; (iii) apparent cost of the different treatment methods. The untreated reverse osmosis concentrates were collected from two treatment plants:- Luggage Point, and Bundamba, both near Brisbane, Queensland, Australia. The first contains more colourful of organics than the second plant. Stirred cell fractionation with ultrafiltration membranes was used to characterise the removed key pollutants, as it offers better accuracy and reproducibility compared to centrifugation fractionation. Fluorescence spectral was used to monitor and identify specific organic compounds. The largest fraction was smaller sized <1kDa. This is probably small humic substances and fulvic acids, as indicated by Excitation Emission Matrix (EEM) analysis. A smaller portion of soluble microbial products (SMPs) also contributes to the concentrates. Bundamba contains large non coloured organics including organic nitrogen with elevated ammonia-N. In contrast, Luggage Point has higher colour, inorganic carbon and conductivity with less ammonia-N. Advanced Oxidation Process (AOP) was the most effective treatment method (high removal of organics, e.g. 55% COD of initial), followed by magnetised ion exchange (MIEX) and coagulations. For UV/H2O2 AOP, the optimal operating condition 400mg.L-1 H2O2 and 3.1kWh.m-3 energy input resulted in organics removals up to 55% with complete decolourisation. The effective reduction was found in all size ranges, preferably in >1kDa. Low inorganic carbon and salinity in Bundamba may allow better overall oxidation rates. MIEX also performed better in Bundamba with organic removals up to 43% and 80% decolourisation at the optimum resin dose of 15mL.L-1. Removal was preferential in size range of >3kDa, with more proportional percentage for decolourisation. Similarly, ferric coagulation removed a wider size range of organics. Further, ferric achieved better organic removal in Luggage Point with up to 49%. At the same molar dose (1.5mM), ferric is superior to alum, especially in Bundamba where there were less hydrophobic compounds according to EEM. Alum is poor for treatment of high organics with less coloured water. MIEX with an operational cost (chemicals and power only) of $0.14-$0.20.m-3 treated water seemed to be the most effective treatment overall. The resin achieved better results with a slightly higher cost than coagulation, and had a lower environmental impact due to reduced sludge production. AOP offers better treatment, but at a higher cost ($0.47.m-3 treated). Combined alternatives may benefit the removal effectiveness. Furthermore, more specific identification of contaminants should be investigated separately to choose appropriate treatment for priority chemicals. Another issue is further investigation of costing, including capital, and full environmental impact of treatment.
315

Synthesis and evaluation of an inorganic microsphere composite for the selective removal of ¹³⁷cesium from acidic nuclear waste solutions /

Tranter, Troy J. January 1900 (has links)
Thesis (Ph. D., Chemical Engineering)--University of Idaho, May 2006. / Major professor: Vivek Utgikar. Includes bibliographical references (leaves 99-107). Also available online (PDF file) by subscription or by purchasing the individual file.
316

The effect of ion exchange on the diametral strength of porcelain a dissertation submitted in partial fulfillment ... Master of Science in Prosthodontics ... /

Kim, Ih Hoon. January 1991 (has links)
Thesis (M.S.)--University of Michigan, 1991.
317

Recuperação do íon amônio gerado durante a evaporação de lixiviados de aterros utilizando resinas poliméricas de troca iônica / Recovery of ammonium ion generated during the evaporation of landfill leachate using polymeric ion exchange resins

Jackeline Maria Cardoso de França Bahé 17 December 2014 (has links)
O lixiviado gerado em aterro sanitário possui substâncias de difícil degradação e amônia, que dificulta o tratamento biológico. O tratamento do lixiviado gerado em aterros sanitários requer uma série de processos de elevado custo e, outras técnicas de tratamento têm sido investigadas no intuito de reduzir custos e aumentar a eficiência do tratamento. A evaporação do lixiviado é uma técnica que aproveita o gás de aterro como fonte de calor, e é utilizada na redução do volume a tratar; porém as emissões atmosféricas geradas durante essa evaporação indicam a presença de amônia, o que pode causar impactos negativos em torno do aterro. Desta forma, é importante a realização de estudos que aprimorem esta técnica, para que a evaporação torne-se ambientalmente e economicamente viável. A amônia presente em amostras com pH em torno de 8,0 e temperatura em torno de 25C, está na forma de íon amônio, o que favorece ao processo de troca iônica. A troca iônica é um processo que tem sido estudado por muitos pesquisadores e consiste na troca de um ou mais constituintes de uma fase fluida para a superfície de uma fase sólida (resinas poliméricas). Este trabalho apresenta a eficiência de quatro tipos diferentes de resinas poliméricas: Amberlyst 15 Wet, Lewatit VPOC 1800, Dowex Mac-3 e Purolite MN250 na remoção e posterior, recuperação do íon amônio presente nos vapores condensados da evaporação de lixiviados. A princípio foi investigado a quantidade e o momento em que o amônio é lançado durante o processo de evaporação. Em seguida, caracterizaram-se as resinas quanto à eficiência de remoção, o tempo de contato e a quantidade ideal da resina. Estão apresentadas neste estudo as isotermas de adsorção de Langmuir, Freundlich e Temkin em diferentes temperaturas (298-318 K) e as condições ideais do processo. Os resultados apontaram duas resinas com eficiência de remoção, em torno de 40%, para concentrações acima de 1000 mg dm-3 de amônio, utilizando 0,5 g de resina e um tempo de contato de 20 minutos. Diferentes modelos cinéticos foram aplicados: Pseudo-Primeira Ordem, Pseudo-Segunda Ordem, difusão intrapartícula, Elovich e o modelo cinético de difusão externa e os resultados discutidos. Foi possível tratar Através da condensação dos vapores emitidos durante a evaporação do lixiviado, foi possível tratar foi possível obter uma recuperação em torno de 70% do íon amônio contido no vapor condensado proveniente da evaporação do lixiviado. / The leachate generated at the landfill has substances are difficult to degrade and ammonia, which hinders the biological treatment. The treatment of the leachate generated in landfills requires a number of high-cost procedures and other treatment techniques have been investigated in order to reduce costs and increase the efficiency of treatment. Evaporation of leachate is a technique that takes advantage of landfill gas as a heat source , and is used in reducing the volume to be treated, but atmospheric emissions generated during this evaporation indicate the presence of ammonia, which can cause negative impact on the surrounding the landfill. Thus, it is important to conduct studies that will improve this technique, so that evaporation to become environmentally and economically viable. The present in samples with pH around 8.0 and temperature around 25 C, ammonia is in the form of ammonium ion, which favors the ion exchange process. Ion exchange is a process that has been studied by many researchers and consists of the exchange of one or more constituents of a fluid phase to the surface of a solid phase ( polymer resin ). This paper shows the efficiency of four different types of polymeric resins: Amberlyst 15 Wet, Lewatit VPOC 1800 Dowex Mac - 3 and Purolite MN250 removal and later, recovery of ammonium ion present in the vapor condensate evaporation of leachate. At first it was investigated how much and when ammonium is released during the evaporation process. Then, the resins were characterized as to the removal efficiency, the contact time and the optimum amount of the resin. Are presented in this study, adsorption isotherms of Langmuir, Freundlich and Temkin at different temperatures (298-318 K) and the optimal process conditions. The results showed two resins with removal efficiency of around 40% for concentrations above 1000 mg dm-3 ammonium, using 0.5 g of resin and a contact time of 20 minutes. Different kinetic models were applied: pseudo-first order , pseudo-second order, intraparticle diffusion and Elovich kinetic model of external diffusion and results discussed. It can be treated by the condensation of the vapors emitted during the evaporation of the leachate was possible to treat it was possible to obtain a recovery of around 70% of the ammonium ion contained in the condensed steam from the evaporation of leachate.
318

Separacao de elementos das terras raras individuais, por associacao das tecnicas de precipitacao homogenea e de troca ionica

UMEDA, KIYOE 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:23:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:09Z (GMT). No. of bitstreams: 1 00622.pdf: 2326364 bytes, checksum: 665ea383abf1ee58d4ae5e2198a0bebb (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
319

Avaliacao da toxicidade de aguas de chuva a organismos aquaticos / Evaluation of toxicity of rainwater on aquatic organisms

MARTINS, RENATA de S.L. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:27:07Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:20Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
320

Comparison of two HPLC columns: An attempt to improve analysis of carbohydrate-deficient transferrin

Engström, Ida January 2018 (has links)
1ABSTRACTCarbohydrate-deficient transferrin (CDT) is a biomarker for excessive and long-running intake of alcohol. It is a form of transferrin called disialotransferrin that under normal circumstances is &lt;2 % of total transferrin in human blood. An increase is seen when alcohol consumption exceeds450 g per week. CDT is analyzed in serum usinghigh performance liquid chromatography (HPLC) and UV/VIS detection. The purpose of this study was to investigate if an “in routine” method could be improved by switching columns.With ion exchange chromatography transferrin glycoforms are separated and quantified. The carbohydrate-deficient transferrin glycoforms have an isoelectric point between 5,7-5,9 that depends on the number of sialic acids on the molecule. With the use of a salt gradient and pH above the isoelectric point the glycoforms can beseparated depending on their affinity to the stationary phase. Batches with patient and control serum was first analyzed on the routine column Source 15Q PE and then on the alternative column Reprospher 200 SAX 5μm.Student’s t-test showed that the two methods’results correlated but were significantly different. A Bland-Altman plot illustrated differences between the two columns. High and low control serum values from Reprospher were lower than the accepted interval. In this study Reprospher’s stationary phase seemed to be affected to such an extent that stabile retention time, better resolution, and stabile values could not be achieved and because the information about the column was lacking an attempt to regeneratethe columnwas not conducted.

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