Adsor??o dos corantes Auramina-O e Safranina-T em baga?o de cana carboxilado : estudos em sistemas mono- e bicomponente em batelada.

Programa de P?s-Gradua??o em Engenharia Ambiental. N?cleo de Pesquisas e P?s-Gradua??o em Recursos H?dricos, Universidade Federal de Ouro Preto.As ind?strias t?xteis s?o as grandes respons?veis pelo lan?amento de efluentes contendo corantes em corpos d??gua, os quais contribuem para o desequil?brio ambiental, al?m de serem nocivos ? sa?de humana. Logo, faz-se necess?rio o estudo de m?todos que sejam capazes de remover corantes de efluentes. Diante da busca por m?todos de remo??o de corantes, aqueles baseados em fontes renov?veis t?m despertado um grande interesse cient?fico. Os materiais lignocelul?sicos s?o alguns dos biomateriais mais estudados, os quais permitem introduzir em suas superf?cies uma diversidade de grupos funcionais, obtendo-se materiais de baixo custo com elevada capacidade de adsor??o em meio aquoso. Neste trabalho foi sintetizado, a partir do baga?o de cana-de-a??car, um adsorvente para ser utilizado na remo??o de corantes de solu??es sinteticamente contaminadas, por processo de adsor??o em batelada. A modifica??o qu?mica do baga?o de cana foi realizada utilizando o anidrido trimel?tico (AT), sendo obtido um novo material contendo grupos carbox?licos introduzidos em sua estrutura (BAT). O material modificado foi caracterizado pelo ganho de massa, quantidade de grupos funcionais introduzidos no material (nCOOH) e ponto de carga zero (PCZ), al?m das t?cnicas de FTIR, MEV, EDX, BET e an?lise elementar de C, H e N. Para os estudos de adsor??o em sistemas mono- e bicomponente, utilizaram-se os corantes b?sicos modelo Auramina-O (AO) e Safranina-T (ST). Foram avaliados no processo de adsor??o a influ?ncia da dosagem de BAT, velocidade de rota??o, pH da solu??o, tempo (cin?tica) e concentra??o inicial de AO e ST (isoterma). A adsor??o foi estudada nos valores de pH 4,5 e 7,0. A capacidade de adsor??o m?xima (Qm?x) obtida em sistema monocomponente em valor de pH 4,5 para AO foi 0,985 mmol g-1 e em valor de pH 7,0 foi 1,119 mmol g-1, enquanto para ST em valor de pH 4,5 foi 0,660 mmol g-1 e em valor de pH 7,0 foi 1,322 mmol g-1. Em sistema bicomponente, em valor de pH 4,5, os valores de Qm?x foram 0,373 mmol g-1 para AO e 0,476 mmol g-1 para ST e em valor de pH 7,0 foram 0,752 mmol g-1 para AO e 1,160 mmol g-1 para ST. Os modelos de isoterma utilizados para avaliar os dados de equil?brio em sistemas monocomponente foram o de Langmuir, Sips, Redlich-Peterson, Dubinin-Radushkevich, Hill-de Boer, Fowler-Guggenheim, enquanto a Teoria da Solu??o Adsorvida Real (RAST) foi usada para avaliar os dados de equil?brio em sistemas bicomponente. Os modelos de cin?tica de pseudo primeira ordem, pseudo segunda ordem e Elovich foram utilizados para modelar os dados de cin?tica em sistemas monocomponente, enquanto o modelo de Corsel foi usado para modelar o sistema bicomponente. A afinidade dos s?tios de adsor??o pelos corantes foi analisada usando o modelo de Scatchard. As varia??es na entalpia de adsor??o (?adsH?) foram medidas por meio da t?cnica da calorimetria de titula??o isot?rmica (ITC) para os sistemas monocomponente em valores de pH 4,5 e 7,0. Esses valores foram usados juntamente com os valores de varia??o na energia livre de adsor??o (?adsG?) para se obter as varia??es na entropia de adsor??o (?adsS?) para um melhor entendimento da intera??o entre os corantes AO e ST e BAT. Estudos de dessor??o e re-adsor??o foram realizados e o adsorvente BAT apresentou um grande potencial para ser empregado em mais de um ciclo de adsor??o.Textile industries are largely responsible for the release of synthetic dyes into water bodies, which contribute to environmental imbalance. In addition, dyes are harmful to the health of animals and humans. Therefore, it is necessary to study methods capable of removing synthetic dyes from the effluents. In the search for methods to remove synthetic dyes from effluents, materials derived from renewable macromolecules have attracted a great scientific interest. The lignocellulose materials are some of the most studied biomaterials, which allow to introduce in their surfaces a great variety of functional chelating groups. This also allows the obtaining new materials with a lower cost and a high adsorption capacity for removal of pollutants from liquid phase. In this study, an adsorbent material (BAT) was synthesized from the sugarcane bagasse to be used in the removal of dyes from spiked aqueous solutions in batch adsorption process. The chemical modification of sugarcane bagasse (BC) was carried out using the trimellitic anhydride (AT), which allows the introduction of carboxylic acid groups on the surface of BC. The adsorbent BAT was characterized by weight gain, amount of carboxylic acid groups (nCOOH), point of zero charge (PZC), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and elemental analysis (C, H and N). Surface area and porosity were determined by BET and BJH methods. Auramine-O and Safranin-T were chosen as model basic dyes for adsorption studies in mono- and bicomponent systems at pH values of 4.5 and 7.0. The influence of BAT dosage, agitation speed, solution pH, contact time and initial dye concentration on the adsorption capacity of BAT was evaluated. The maximum adsorption capacities (Qmax) obtained in monocomponent system at pH 4.5 and 7.0 were 0.985 and 1.119 mmol g-1 for AO and 0.660 and 1.322 mmol g- 1 for ST, respectively. In addition, Qmax in bicomponent system at pH 4.5 were 0.373 and 0.476 mmol g-1 for AO and ST and at pH 7.0 were 0.752 and 1.160 mmol g-1 for AO and ST, respectively. The isotherm models used to evaluate the equilibrium data in monocomponent system were the models of Langmuir, Sips, Redlich-Peterson, Dubinin-Radushkevich, Hill-de Boer, Fowler-Guggenheim, while Real Adsorbed Solution Theory (RAST) was used to model the equilibrium data in bicomponent system. The kinetic models of pseudo-first- and pseudo-second-order and Elovich were used to evaluate the kinetic data in monocomponent system, while the Corsel model was used to model the bicomponent data. The affinity of the adsorption sites of BAT for both dyes was evaluated using the Scatchard plot. The changes in adsorption enthalpy (?adsH?) were measured by isothermal titration calorimetry (ITC) only for monocomponent systems at pH 4.5 and 7.0. The values of ?adsH? together with changes in adsorption free energy (?adsG?) were used to obtain the changes in adsorption entropy (?adsS?) in order to clarify the magnitude of interaction between AO and ST dyes and adsorption sites of BAT. Desorption and re-adsorption studies were performed and the adsorbent BAT exhibited a great potential to be used in more than one adsorption cycle

Partition study of textile dye Remazol Yellow Gold RNL in aqueous two-phase systems.

Submitted by Karine Ribeiro ([email protected]) on 2015-04-08T17:01:39Z No. of bitstreams: 1 ARTIGO_PartitionStudyTextile.pdf: 440611 bytes, checksum: e3f2457db7f140ff24122a7f6a594572 (MD5)Approved for entry into archive by Oliveira Flávia ([email protected]) on 2015-04-10T20:52:32Z (GMT) No. of bitstreams: 1 ARTIGO_PartitionStudyTextile.pdf: 440611 bytes, checksum: e3f2457db7f140ff24122a7f6a594572 (MD5)Made available in DSpace on 2015-04-14T17:57:02Z (GMT). No. of bitstreams: 1 ARTIGO_PartitionStudyTextile.pdf: 440611 bytes, checksum: e3f2457db7f140ff24122a7f6a594572 (MD5) Previous issue date: 2015The removal of organic dye pollutants from wastewater produced by the textile industry is a complex problem that presents potential health risks to the general public. Remazol Yellow Gold RNL (YR) dye is readily used to dye cellulose base materials and the methods developed for its removal from aqueous systems are either inefficient or too expensive to be adopted by smaller textile manufactures. Our approach is based on aqueous two-phase system (ATPS) using salts and either polymers or ionic liquids to extract Remazol Yellow Gold RNL from wastewater. Parameters such as the nature of the electrolyte, molecular mass of polymer and tie line length (TLL) on the dye partition coefficient (KYR) were all evaluated. A phase diagram for the polyethylene glycol (PEG 4000 g mol_1) and magnesiumsulfate system at 298.15 Kwas obtained and used to study the partitioning of YR. The KYR values demonstrate the potential of both systems for the removal of dyes from industrial effluents. The partition mechanismwas discussed based on the Haynes model and using the of Gibbs standard energy change (DtrG_). The driving force (enthalpy and/or entropy) that governs the partitioning of the dye depends on the nature of the ATPS. The optimized conditions that gave the best system was successfully applied to the removal of YR from wastewater obtained from a local textile manufacturer. The high KYR values in the presence of the effluent demonstrate the potential and robustness of the ATPS for the treatment of effluents from textile industries

Trimellitated sugarcane bagasse: A versatile adsorbent for removal of cationic dyes from aqueous solution. Part I: Batch adsorption in a monocomponent system

Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g−1 at pH 4.5, and 1.734 and 1.230 mmol g−1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol−1, indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions

Trimellitated sugarcane bagasse : a versatile adsorbent for removal of cationic dyes from aqueous solution. Part II: batch and continuous adsorption in a bicomponent system.

In the second part of this series of studies, the bicomponent adsorption of safranin-T (ST) and auramine-O (AO) on trimellitated sugarcane bagasse (STA) was evaluated using equimolar dye aqueous solutions at two pH values. Bicomponent batch adsorption was investigated as a function of contact time, solution pH and initial concentration of dyes. Bicomponent kinetic data were fitted by the pseudo-first-order and pseudo-second-order models and the competitive model of Corsel. Bicomponent equilibrium data were fitted by the real adsorbed solution theory model. The antagonistic interactions between ST and AO in the adsorption systems studied contributed to obtain values of maximum adsorption capacity in mono- (Qmax,mono) and bicomponent (Qmax,multi) lower than unity (Qmax,multi/Qmax,mono at pH 4.5 for ST of 0.75 and AO of 0.37 and at pH 7 for ST of 0.94 and AO of 0.43). Mono- and bicomponent adsorption of dyes in a fixed-bed column was evaluated at pH 4.5. The breakthrough curves were fitted by the Thomas and Bohart-Adams original models. Desorption of ST in a fixed-bed column was studied. The results obtained from the bicomponent batch and continuous adsorption showed that the presence of ST most affected the AO adsorption than the presence of AO affected the ST adsorption

Trimellitated sugarcane bagasse : a versatile adsorbent for removal of cationic dyes from aqueous solution. Part I : batch adsorption in a monocomponent system.

Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g 1 at pH 4.5, and 1.734 and 1.230 mmol g 1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration energy and entropy of adsorption were calculated. These thermodynamic parameters were also used to evaluate the adsorption mechanism at both pH values

Imagens, analogias, modelos e charge : distintas abordagens no ensino de química envolvendo o tema polímeros.

No presente trabalho, a equipe do PIBID Química da Universidade Federal de Ouro Preto proporcionou, aos alunos da educação básica da região, a participação ativa no processo de construção do conceito de polímeros. Para a execução da proposta, foi solicitado aos alunos que selecionassem imagens por meio da internet. A partir daí, atividades desenvolvidas pelos alunos do PIBID baseadas em analogias, modelos e charge foram usadas com o intuito de proporcionar uma ampla discussão sobre simbologia e estrutura em química, ligação química e sobre questões importantes para todos os cidadãos como reciclagem e uso consciente de matéria-prima