• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • Tagged with
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 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.
1

Tratamento de efluente têxtil através de processos redox e separação com membranas combinados / Treatment of textile wastewater by combination of redox and membrane separation processes

Alvarenga, Rodrigo Neder 14 August 2009 (has links)
O processamento têxtil gera grande quantidade de despejos altamente poluidores, contendo valores elevados de carga orgânica, cor acentuada e compostos químicos tóxicos ao homem e ao meio ambiente. Os efluentes têxteis apresentam uma variação muito grande na sua composição devido aos vários tipos de corantes e produtos químicos utilizados e isto faz o seu tratamento ser um problema complexo. Devido a estas implicações, novas tecnologias têm sido buscadas para a degradação ou imobilização destes compostos em efluentes têxteis dentre os quais a combinação de processos oxidativos avançados, redutivo e separação por membranas. Os processos de separação por membranas têm sido cada vez mais aplicados para separação, purificação e concentração de constituintes industriais, principalmente pelo desenvolvimento e eficiência da técnica e redução de custos com o passar dos anos. O processo redutivo utilizando Fe0 é bastante promissor, em função do custo relativamente baixo do ferro metálico e da sua elevada efetividade na degradação de contaminantes ambientais, sendo que após a oxidação do Fe0 a íons Fe2+ e Fe3+ estes íons podem ser aproveitados em sequência nos Processos Oxidativos Avançados (POAs). Os processos oxidativos avançados são tecnologias extremamente eficientes para destruição de compostos orgânicos de difícil degradação. Podem ser consideradas tecnologias limpas, pois não há a formação de subprodutos sólidos e nem a transferência de fase dos poluentes. Os POAs são baseados na geração de radicais fortemente oxidativos, principalmente o radical hidroxila (HOo), que destroem inúmeros compostos de maneira rápida e pouco seletiva, quando comparado aos processos convencionais, conduzindo a mineralização parcial ou completa dos contaminantes. Com o objetivo de estudar o efeito destes processos na melhoria do efluente têxtil foi utilizado um efluente de uma indústria têxtil de grande porte do interior de São Paulo. Ao ser coletado, este efluente foi caracterizado e submetido à permeação por membranas de microfiltração (0,45 μm). Este tratamento possibilitou a redução de 37,7 % do COT e 40,9 % da Área Espectral (200-800 nm) em comparação com o efluente original. O efluente oriundo do tratamento com membranas foi submetido, através de planejamento de experimentos, aos processos oxidativos avançados do tipo foto-Fenton e foto-Fenton avançado (utilizando Fe0) visando à melhoria para despejo ou reúso deste efluente. Na melhor condição de reação foi possível alcançar uma redução de aproximadamente 73,0 % em COT e 93,0 % em área espectral após uma hora de reação para os dois tipos de POAs. A combinação das tecnologias de membranas e processos oxidativos avançados mostrou-se extremamente positiva quanto à melhoria da deste efluente têxtil, possibilitando a redução em torno de 83,0 % do COT e 95,0 % da área espectral. / The textile manufacturing generates large amounts of highly polluting sewage containing high levels of organic load, color and chemical compounds toxic to human beings and to the environment. This textile wastewater has a great variation in its composition due to various types of dyes and chemicals used. All these considerations make the textile wastewater treatment a complex problem. Due to these implications, new technologies have been studied for degradation or immobilization of these compounds in textile wastewater among which the combination of advanced oxidative, reductive and separation with membranes processes. The separation processes with membranes have been increasingly applied for separation, purification and concentration of industrial components, mainly development in technology and efficient cost savings over the years. The reductive process using Fe0 is very promising because of the relatively low cost of metallic iron and its high effectiveness in the degradation of environmental contaminants. After the oxidation of Fe0 to Fe2+ and Fe3+ these ions can be used in sequence in the Advanced Oxidative Process (AOPs). The advanced oxidative process technologies are extremely effective for degradation of organic compounds with difficult degradation. It can be considered as a clean technology, because there is no formation of solid subproducts, neither the phase transfer of pollutants. The AOPs are based on the generation of highly oxidative radicals, particularly hydroxyl radical (HOo), which destroys many compounds to a rapid and low selective way compared with conventional process of treatment, leading to partial or complete mineralization of contaminants. A wastewater from a large textile industry in São Paulo was used in order to study the effect of these processes in the improvement of textile wastewater quality. Firstly, the wastewater was characterized and subjected to permeation by microfiltration membrane (0.45 μm). This treatment allowed a reduction of 37.7 % of TOC and 40.9 % of spectral area (200-800 nm) compared to the original wastewater. The wastewater from the treatment with membranes was subjected, through design of experiments, the advanced oxidative processes of the type photo-Fenton and advanced photo-Fenton (using Fe0) aiming to improve the disposal or to reuse of wastewater. In the best experimental condition it was achieved a 73 % in TOC and 93 % in spectral area reduction after one hour of reaction for both types of AOPs. The membrane technologies and advanced oxidative combination process proved to be extremely positive on the textile wastewater quality improvement, resulting in a reduction of around 83 % of TOC and 95 % of spectral area.
2

Tratamento de efluente têxtil através de processos redox e separação com membranas combinados / Treatment of textile wastewater by combination of redox and membrane separation processes

Rodrigo Neder Alvarenga 14 August 2009 (has links)
O processamento têxtil gera grande quantidade de despejos altamente poluidores, contendo valores elevados de carga orgânica, cor acentuada e compostos químicos tóxicos ao homem e ao meio ambiente. Os efluentes têxteis apresentam uma variação muito grande na sua composição devido aos vários tipos de corantes e produtos químicos utilizados e isto faz o seu tratamento ser um problema complexo. Devido a estas implicações, novas tecnologias têm sido buscadas para a degradação ou imobilização destes compostos em efluentes têxteis dentre os quais a combinação de processos oxidativos avançados, redutivo e separação por membranas. Os processos de separação por membranas têm sido cada vez mais aplicados para separação, purificação e concentração de constituintes industriais, principalmente pelo desenvolvimento e eficiência da técnica e redução de custos com o passar dos anos. O processo redutivo utilizando Fe0 é bastante promissor, em função do custo relativamente baixo do ferro metálico e da sua elevada efetividade na degradação de contaminantes ambientais, sendo que após a oxidação do Fe0 a íons Fe2+ e Fe3+ estes íons podem ser aproveitados em sequência nos Processos Oxidativos Avançados (POAs). Os processos oxidativos avançados são tecnologias extremamente eficientes para destruição de compostos orgânicos de difícil degradação. Podem ser consideradas tecnologias limpas, pois não há a formação de subprodutos sólidos e nem a transferência de fase dos poluentes. Os POAs são baseados na geração de radicais fortemente oxidativos, principalmente o radical hidroxila (HOo), que destroem inúmeros compostos de maneira rápida e pouco seletiva, quando comparado aos processos convencionais, conduzindo a mineralização parcial ou completa dos contaminantes. Com o objetivo de estudar o efeito destes processos na melhoria do efluente têxtil foi utilizado um efluente de uma indústria têxtil de grande porte do interior de São Paulo. Ao ser coletado, este efluente foi caracterizado e submetido à permeação por membranas de microfiltração (0,45 μm). Este tratamento possibilitou a redução de 37,7 % do COT e 40,9 % da Área Espectral (200-800 nm) em comparação com o efluente original. O efluente oriundo do tratamento com membranas foi submetido, através de planejamento de experimentos, aos processos oxidativos avançados do tipo foto-Fenton e foto-Fenton avançado (utilizando Fe0) visando à melhoria para despejo ou reúso deste efluente. Na melhor condição de reação foi possível alcançar uma redução de aproximadamente 73,0 % em COT e 93,0 % em área espectral após uma hora de reação para os dois tipos de POAs. A combinação das tecnologias de membranas e processos oxidativos avançados mostrou-se extremamente positiva quanto à melhoria da deste efluente têxtil, possibilitando a redução em torno de 83,0 % do COT e 95,0 % da área espectral. / The textile manufacturing generates large amounts of highly polluting sewage containing high levels of organic load, color and chemical compounds toxic to human beings and to the environment. This textile wastewater has a great variation in its composition due to various types of dyes and chemicals used. All these considerations make the textile wastewater treatment a complex problem. Due to these implications, new technologies have been studied for degradation or immobilization of these compounds in textile wastewater among which the combination of advanced oxidative, reductive and separation with membranes processes. The separation processes with membranes have been increasingly applied for separation, purification and concentration of industrial components, mainly development in technology and efficient cost savings over the years. The reductive process using Fe0 is very promising because of the relatively low cost of metallic iron and its high effectiveness in the degradation of environmental contaminants. After the oxidation of Fe0 to Fe2+ and Fe3+ these ions can be used in sequence in the Advanced Oxidative Process (AOPs). The advanced oxidative process technologies are extremely effective for degradation of organic compounds with difficult degradation. It can be considered as a clean technology, because there is no formation of solid subproducts, neither the phase transfer of pollutants. The AOPs are based on the generation of highly oxidative radicals, particularly hydroxyl radical (HOo), which destroys many compounds to a rapid and low selective way compared with conventional process of treatment, leading to partial or complete mineralization of contaminants. A wastewater from a large textile industry in São Paulo was used in order to study the effect of these processes in the improvement of textile wastewater quality. Firstly, the wastewater was characterized and subjected to permeation by microfiltration membrane (0.45 μm). This treatment allowed a reduction of 37.7 % of TOC and 40.9 % of spectral area (200-800 nm) compared to the original wastewater. The wastewater from the treatment with membranes was subjected, through design of experiments, the advanced oxidative processes of the type photo-Fenton and advanced photo-Fenton (using Fe0) aiming to improve the disposal or to reuse of wastewater. In the best experimental condition it was achieved a 73 % in TOC and 93 % in spectral area reduction after one hour of reaction for both types of AOPs. The membrane technologies and advanced oxidative combination process proved to be extremely positive on the textile wastewater quality improvement, resulting in a reduction of around 83 % of TOC and 95 % of spectral area.
3

PER- AND POLYFLUOROALKYL SUBSTANCES (PFAS) DEGRADATION BY NANOSCALE ZERO-VALENT IRON UNDER LIGHT FOR WATER REUSE

Xia, Chunjie 01 May 2022 (has links) (PDF)
Wastewater reclamation and reuse have been increasingly practiced as sustainable strategies to meet water demands, particularly in regions threatened by water shortages. However, one of the biggest challenges for reusing wastewater effluents (WEs) as irrigation water is to remove emerging organic contaminants such as persistent and potentially bioaccumulated per- and polyfluoroalkyl substances (PFAS), whose presence may result in adverse impacts on crops, soils, aqueous ecosystems, and human health. Photocatalysis is an effective and promising technique to remediate PFAS in aqueous media. This dissertation aims to: i) Develop a novel, environmental-friendly, and low-cost treatment process for PFAS removal and degradation for water reuse; ii) Optimize the experimental conditions and investigate the removal mechanisms of PFAS with different structures in this novel process; iii) Scale up this treatment process and apply it to treatment of WEs in a point-of-use (POU) system. First, ultraviolet (UV) C /nanoscale zero-valent iron (nZVI, Fe0 nanoparticles (NPs)) system is used for the first time to induce PFAS photocatalytic removal from aqueous solution. Oxidative and/or reductive degradation of three representative PFAS - perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS) was achieved using Fe0 NPs under UVC light both with and without presence of oxygen. However, no PFAS removal was observed either under visible light and in the dark, and much lower PFAS degradation was achieved under UVA light. Higher degradation and defluorination efficiencies were obtained for longer chain PFNA compared to PFOA, and higher degradation and defluorination of PFAS were achieved without presence of O2 compared to with O2. The degradation of PFOA and PFOS followed first order reaction kinetics with the highest efficiencies achieved of 97.6, >99.9, and 98.5% without presence of O2 for PFOA, PFNA, and PFOS, respectively. The degradation efficiencies increased with the increase of nZVI concentrations in the range of 1-100 mg/L. The degradation efficiency of PFOA using bare Fe0 NPs was higher than that using 1% PVP-coated Fe0 NPs in the initial 6 h. Second, the removal mechanism of PFAS in UVC/Fe0 NPs system was obtained by testing the concentrations of iron ions (Fe2+/Fe3+), intermediate products, and reactive oxygen species (ROS, e.g., ·O2- and ·OH) generated, and conducting ROS quenching experiments. The proposed degradation pathway of PFCAs (PFNA and PFOA) was initiated from PFOA/PFNA oxidation by transferring an electron of the carboxylate terminal group of PFOA/PFNA to the Fe(III)-carboxylate complex, then followed by decarboxylation−hydroxylation−elimination−hydrolysis (DHEH) pathway and the accompanying CO2 and F− release. The generated shorter chain PFCAs also underwent degradation with time in the system. This proposed degradation pathway was confirmed by the formation of shorter chain PFCAs, e.g. PFHpA, PFHxA, PFPeA, and PFBA, F- ions, and rapid consumption of Fe3+. For PFOS, besides H/F exchange pathway and chain-shortening (DHEH pathway) to form short chain PFAS during PFCA degradation, desulfonation to form PFOA followed by PFOA degradation also happened. These pathways were suggested by the formation of intermediates — trace amount of shorter chain PFCAs, 6:2 FTS, PFHpS, and F- ions. ·O2- and ·OH were not involved in PFOA degradation in the UVC/Fe0 NPs system with presence of O2, while they may be involved in PFOS degradation, e.g., desulfonation to form PFOA, which were suggested by the results of quenching experiments. And introducing H2O2 into the UVC/Fe0 NPs system resulted in lower PFOA degradation efficiency and defluorination efficiency, which also indicated that ·OH may not be involved in PFOA degradation. Hydrated electrons e-aq that can be involved in desulfonation, defluorination, and C-C bond scission processes were likely quenched by the presence of oxygen to reduce the degradation and defluorination efficiencies; plus, presence of Fe0 NPs may promote the generation of hydrated electrons. Last, UVC/Fe0 NPs system was used to degrade PFAS from WEs in both bench scale and in a scale up POU system. The degradation efficiencies of PFAS in WEs from both wastewater treatment plants (WWTP) were lower than that in deionized water, likely reflecting the complex compositions in the environmental media. Optimal degradation efficiencies of 90±1%, 88±1%, and 46±2% were obtained for PFNA, PFOS, and PFOA, respectively, each starting from 0.5 µg/L using bare Fe0 at pH 3.0 after 2 h. PFAS removal and bacterial inactivation were achieved simultaneously in the POU system using Fe0 NPs without and with rGO support under UVC irradiation in WEs, although the PFAS levels were still above the regulation levels for discard. These pilot tests provided more data and experiences for the real applications of UVC/Fe0 NP system to PFAS contaminated wastewater or other water matrix treatment. Overall, this research demonstrated a cost-effective and environment-friendly method — UVC/Fe0 NPs method for PFAS (i.e., PFOA, PFNA, and PFOS) degradation from WEs for water reuse both with and without presence of oxygen. The possible degradation mechanisms of PFAS with different structures were obtained by testing the concentrations of iron ions, intermediate products, and reactive oxygen species (ROS) involved in the reactions. The developed technology can be potentially applied to treat other environmental media (e.g., groundwater, landfill leachate) that are contaminated by PFAS from previous anthropogenic activities.
4

Aplica??o de nanopart?culas bimet?licas de Fe-Ni estabilizadas com CMC para remedia??o de ?gua contaminada com nimesulida e ranitidina

Ara?jo, Annelise Fran?a 19 February 2016 (has links)
Submitted by M?rden L?les (marden.inacio@ufvjm.edu.br) on 2016-07-14T23:23:32Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Annelise Fran?a Ara?jo.pdf: 2722328 bytes, checksum: 24fe96c2c5e7a6dd79e50d8862a82e63 (MD5) / Rejected by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br), reason: Renomear o arquivo em caixa baixa, nomes separados por _ on 2016-07-18T15:00:35Z (GMT) / Submitted by M?rden L?les (marden.inacio@ufvjm.edu.br) on 2016-07-19T20:32:21Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Annelise Fran?a Ara?jo.pdf: 2722328 bytes, checksum: 24fe96c2c5e7a6dd79e50d8862a82e63 (MD5) / Rejected by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br), reason: renomear arquivo on 2016-07-21T16:57:28Z (GMT) / Submitted by M?rden L?les (marden.inacio@ufvjm.edu.br) on 2016-07-21T17:36:11Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Annelise_Fran?a_Ara?jo.pdf: 2722328 bytes, checksum: 24fe96c2c5e7a6dd79e50d8862a82e63 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-07-22T15:32:43Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Annelise_Fran?a_Ara?jo.pdf: 2722328 bytes, checksum: 24fe96c2c5e7a6dd79e50d8862a82e63 (MD5) / Made available in DSpace on 2016-07-22T15:32:43Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Annelise_Fran?a_Ara?jo.pdf: 2722328 bytes, checksum: 24fe96c2c5e7a6dd79e50d8862a82e63 (MD5) Previous issue date: 2016 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Funda??o de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) / RESUMO Nanopart?culas bimet?licas de Fe-Ni estabilizadas com carboximetilcelulose (CMC-bNP-Fe-Ni) foram sintetizadas, caracterizadas e aplicadas na remo??o dos f?rmacos nimesulida (NMS) e ranitidina (RNTD) em ?gua. Para os ensaios em batelada em solu??es aquosas fatores que afetam a remo??o dos f?rmacos tais como a sua concentra??o e a dosagem de CMC-bNP-Fe-Ni foram investigados sistematicamente. Os resultados experimentais revelaram uma remo??o completa de NMS e de 84% de remo??o de RNTD. Como esperado para uma rea??o heterog?nea realizada em batelada, sob vigorosa agita??o, foi verificado que a taxa de remo??o aumentou com o aumento da dosagem de CMC-bNP-Fe-Ni e a concentra??o dos f?rmacos. Foi realizado um estudo do efeito da velocidade de agita??o do sistema, verificando que este ? um fator que influencia diretamente a taxa de remo??o. O estudo de remo??o na presen?a e na aus?ncia de oxig?nio dissolvido revelou que a presen?a deste exerceu uma pequena influ?ncia no processo de remo??o. Um estudo comparativo utilizando a CMC-bNP-Fe-Ni e a carboximetilcelulose (CMC) como estabilizante de nanopart?culas de ferro de val?ncia zero (CMC-nFZV) foi realizado nas mesmas propor??es, sendo verificado que os n?veis de remo??o foram superiores para o sistema CMC-bNP-Fe-Ni. A an?lise do subproduto formado da NMS mostrou que este ? menos t?xico que o composto original. O presente trabalho demonstra que o processo de tratamento redutivo alternativo fazendo uso de nanopart?culas bimet?licas contendo Fe e Ni ? muito promissor para a elimina??o de f?rmacos, como ? o caso de NMS e RNTD. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016. / ABSTRACT Fe-Ni bimetallic nanoparticles stabilized with carboxymethylcellulose (CMC-bNP-Fe-Ni) were synthesized, characterized and applied to remove nimesulide drugs (NMS), and ranitidine (RNTD) drugs in water. For the test batch in aqueous solutions, factors affecting the removal of drugs such as the dosage of CMC-bNP-Fe-Ni and the concentration of NMS and RNTD were investigated systematically. The experimental results showed a complete removal of NMS and 84% for the RNTD at concentrations ranging up to 60 mg L-1 and at a dosage of CMC-bNP-Fe-Ni 0.2 and 0.4 g L-1, respectively. As expected for a heterogeneous reaction carried out in batch, under vigorous stirring, it was found that the removal rate increased with the increase of the dosage of CMC-bNP-Fe-Ni and concentration of the drugs. A study of the effect of system stirring speed was carried out by checking that this is a factor that directly influence the removal rate. The removal of the presence and in the absence of dissolved oxygen showed that the presence of the latter exerts a small influence on the removal process. A comparison of removal using CMC-bNP-Fe-Ni and carboxymethylcellulose (CMC) as a stabilizer of zero-valent iron nanoparticles (CMC-nFZV) was performed in the same proportions, and found that the removal rates were higher for system CMC-bNP-Fe-Ni. The analysis of the byproduct formed from the NMS showed that it is less toxic than the parent compound. The present work demonstrates that the reductive treatment process alternative making use of bimetallic nanoparticles containing Fe and Ni is very promising for the elimination of drugs, such as NMS and RNTD.

Page generated in 0.0341 seconds