Metodologia de análise de dioxinas em cinzas obtidas da incineração de couro Wet-Blue

O presente trabalho trata da validação de uma metodologia de análise para a determinação de dibenzo-p-dioxinas policloradas (PCDDs) em cinzas obtidas através de um processo de incineração de aparas de couro wet-blue. As dioxinas, compostos de extrema toxicidade, podem ser formadas na superfície das partículas de cinzas em reações de combustão. O mecanismo de formação de PCDDs requer uma atmosfera rica em oxigênio, uma fonte de cloro e a presença na cinza de um metal capaz de catalizar uma reação Deacon. O couro wet-blue apresenta em sua composição os precursores para a formação de dioxinas tais como o cloro e o metal catalisador sódio, cuja presença destes elementos foi comprovada por análises de superfície realizadas no couro e nas cinzas usando as técnicas de Rutherford Back-scattering Spectrometry (RBS) e Microscopia Eletrônica de Varredura (MEV). Desta forma, torna-se necessária a análise de dioxinas em cinzas de couro para especificar seu tratamento e destino final. As cinzas de couro foram obtidas numa unidade de bancada de incineração com reator de leito fixo, processo conhecido como GCC (Gaseificação e Combustão Combinadas). A metodologia utilizada para analisar dioxinas nas cinzas de couro foi baseada no Método 8280B da Agência de Proteção Ambiental dos Estados Unidos da América (EPA-USA). Este método descreve os procedimentos de extração de matrizes específicas, o clean-up para os analitos específicos e a determinação de dioxinas através das técnicas de cromatografia gasosa de alta resolução e espectrometria de massa de baixa resolução. O sucesso da análise depende da preparação dos extratos das amostras, etapa conhecida como clean-up, a qual é descrita minuciosamente neste trabalho, incluindo a montagem das colunas cromatográficas. A eficiência de extração das dioxinas foi obtida com os resultados comparativos das análises entre matrizes contaminadas com solução padrão de dioxinas e o padrão analítico. A validação deste método para análise de dioxinas policloradas em cinzas de couro wet-blue foi considerada satisfatória para os objetivos do trabalho, uma vez que a eficiência de extração de dioxinas obtida ficou dentro dos critérios estabelecidos pelo método.

Determinação das espécies de cromo nas cinzas da incineração de couro wet-blue em reatores de leito fixo e leito fluidizado

Este trabalho tem como objetivo a determinação quantitativa da concentração de cromo (III, VI e total) nas cinzas de serragem de couro wet-blue, incineradas em reatores de leito fixo nas temperaturas de 450, 550 e 650 C e reator de leito fluidizado nas temperaturas de 730, 780, 830 e 850 C, verificando se estes resultados estão dentro dos limites permitidos pelas normas ambientais brasileiras e, consequentemente, se em relação à concentração de cromo, os processos de incineração utilizados são uma maneira adequada de promover a eliminação ambientalmente aceitável da serragem de couro wet-blue. Realizou-se, neste trabalho, o estudo dos procedimentos para digestão da amostra, dos métodos analíticos quantitativos para a determinação da concentração de cromo que constatou-se depender da valência a ser analisada. As determinações de cromo total e cromo hexavalente contido nas cinzas foram realizadas após digestão ácida e digestão alcalina da amostra, respectivamente. Após o processo de digestão o cromo total (na forma de Cr (VI)) e o cromo hexavalente foram determinados por dois métodos espectrofotométricos na forma de Cr (VI) em meio ácido com difenilcarbazida (DPC) e após redução na forma de Cr (III), complexado com EDTA. O cromo total também foi determinado por volumetria empregando o método titulométrico. Este método não foi empregado na determinação de cromo hexavalente devido aos baixos teores deste nas cinzas. O teor de Cr (III) foi obtido pela diferença entre o cromo total e cromo hexavalente Procedendo-se a análise estatística dos resultados de cromo hexavalente e total nas cinzas pelos diferentes técnicas analíticas, independente do tipo de incinerador, verificou-se que não há diferenças significativas entre os mesmos. Podendo, portanto, utilizar quaisquer uma das técnicas para avaliá-los. Comparando-se os resultados das análises obtidos na incineração da serragem de couro wet-blue em reator de leito fixo e reator de leito fluidizado em diferentes temperaturas, verificou-se que no reator de leito fixo o teor de Cr (VI) nas cinzas geradas foi muito baixa, praticamente inexistente; enquanto que no reator de leito fluidizado se a temperatura de combustão não for muito alta o teor de Cr (VI) ficará dentro dos limites aceitáveis. As cinzas provenientes de qualquer um dos processos de incineração analisadas, neste trabalho, tanto do reator de leito fixo como de leito fluidizado não é conveniente que seja descartada diretamente no solo. As mesmas devem ser aproveitadas na indústria de cerâmicos, ou mesmo em algum processo que visa recuperar o cromo.

Membrana de alumina anódica: comportamento da microestrutura e estudo das propriedades ópticas após tratamento térmico

Thin commercial aluminum electrolytic and passed through reactions was obtained with anodic alumina membranes nanopores. These materials have applications in areas recognized electronic, biomedical, chemical and biological weapons, especially in obtaining nanostructures using these membranes as a substrate or template for processing nanowires, nanodots and nanofibers for applications noble. Previous studies showed that the membranes that have undergone heat treatment temperature to 1300° C underwent changes in morphology, crystal structure and optical properties. This aim, this thesis, a study of the heat treatment of porous anodic alumina membranes, in order to obtain and to characterize the behavior changes structures during the crystallization process of the membranes, at temperatures ranging between 300 and 1700° C. It was therefore necessary to mount a system formed by a tubular furnace resistive alumina tube and controlled environment, applying flux with special blend of Ag-87% and 13% N2, in which argon had the role of carrying out the oxygen nitrogen system and induce the closing of the pores during the densification of the membrane. The duration of heat treatment ranged from 60 to 15 minutes, at temperatures from 300 to 1700° C respectively. With the heat treatment occurred: a drastic reduction of porosity, grain growth and increased translucency of the membrane. For the characterization of the membranes were analyzed properties: Physical - thermogravimetric, X-ray diffraction, BET surface area; morphological - SEM, EDS through compositional and, optical absorbance, and transmittance in the UV-VIS, and FTIR. The results using the SEM showed that crystallization has occurred, densification and significant changes in membrane structure, as well as obtaining microtube, the BET analysis showed a decrease in specific surface area of the membranes has to 44.381 m2.g-1 to less than 1.8 m2.g-1 and in the analysis of transmittance and absorbance was found a value of 16.5% in the range of 800 nm, characteristic of the near infrared and FTIR have confirmed the molecular groups of the material. Thus, one can say that the membranes were mixed characteristics and properties which qualify for use in gas filtration system, as well as applications in the range of optical wavelength of the infra-red, and as a substrate of nanomaterials. This requires the continuation and deepening of additional study

Desenvolvimento de membranas porosas de alumina para fins de tratamento de efluente industrial têxtil

Textile production has been considered as an activity of high environmental impact due to the generation of large volumes of waste water with high load of organic compounds and strongly colored effluents, toxic and difficult biodegradability. This thesis deals with obtaining porous alumina ceramic membranes for filtration of textile effluent in the removal of contaminants, mainly color and turbidity. Two types of alumina with different particle sizes as a basis for the preparation of formulation for mass production of ceramic samples and membranes. The technological properties of the samples were evaluated after using sintering conditions: 1,350ºC-2H, 1,450ºC-30M, 1,450ºC-2H, 1,475ºC-30M and 1,475ºC-2H. The sintered samples were characterized by XRD, XRF, AG, TG, DSC, DL, AA, MEA, RL, MRF-3P, SEM and Intrusion Porosimetry by Mercury. After the characterization, a standard membrane was selected with their respective sintering condition for the filterability tests. The effluent was provided by a local Textile Industry and characterized at the entry and exit of the treatment plant. A statistical analysis was used to study the effluent using the following parameters: pH, temperature, EC, SS, SD, oil and grease, turbidity, COD, DO, total phosphorus, chlorides, phenols, metals and fecal coliform. The filtered effluent was evaluated by using the same parameters. These results demonstrate that the feasibility of the use of porous alumina ceramic membranes for removing contaminants from textile effluent with improved average pore size of 0.4 micrometre (distribution range varying from 0,025 to 2.0 micrometre), with total porosity of 29.66%, and average percentages of color removal efficiency of 89.02%, 92.49% of SS, turbidity of 94.55%, metals 2.70% (manganese) to 71.52% (iron) according to each metal and COD removal of 72.80%

Compósitos de matriz metálica à base níquel com adição de TaC e NbC produzidos via metalurgia do pó

Carbide reinforced metallic alloys potentially improve some important mechanical properties required for the overall use of important engineering materials such as steel and nickel. Nevertheless, improved performance is achieved not only by composition enhancement but also by adequate processing techniques, such as novel sintering methods in the case of powder metallurgy. The method minimizes energy losses in addition to providing uniform heating during sintering. Thus, the general objective of this study was to evaluate the density, hardness, flexural strength, dilatometric behavior and to analyze the microstructure of metal matrix composites based nickel with addition of carbides of tantalum and / or niobium when sintered in a conventional furnace and Plasma assisted debinding and sintering (PADS). Initially, were defineds best parameters of granulation, screening and mixing procedure. After, mixtures of carbonyl Ni and 5%, 10% and 15 wt.% NbC and TaC were prepared in a Y-type mixer under wet conditions during 60 minutes. The mixtures were then dried and granulated using 1.5 wt. % paraffin diluted in hexane. Granulates were cold pressed under 600 MPa. Paraffin was then removed from the pressed pellets during a pre-sintering process carried out in a tubular furnace at 500 °C during 30 min. The heating rate was 3 ºC/min. The pellets were then sintered using either a plasma assisted reactor or a conventional resistive tubular furnace. For both methods, the heating rate was set to 8 ºC/min up to 1150 °C. The holding time was 60 minutes. The microstructure of the sintered samples was evaluated by SEM. Brinell hardness tests were also carried out. The results revealed that higher density and higher hardness values were observed in the plasma-assisted sintered samples. Hardness increased with the concentration of carbides in the Ni-matrix. The flexural strength also increased by adding the carbides. The decline was larger for the sample with addition of 5% 5% TaC and NbC. In general, compositions containing added carbide 10% showed less porous and more uniform distribution of carbides in the nickel matrix microstructural appearance. Thus, both added carbide and plasma sintering improved density, hardness, flexural strength and microstructural appearance of the composites

Modelagem analítica e experimental da filtração em meios porosos

Deep bed filtration occurs in several industrial and environmental processes like water filtration and soil contamination. In petroleum industry, deep bed filtration occurs near to injection wells during water injection, causing injectivity reduction. It also takes place during well drilling, sand production control, produced water disposal in aquifers, etc. The particle capture in porous media can be caused by different physical mechanisms (size exclusion, electrical forces, bridging, gravity, etc). A statistical model for filtration in porous media is proposed and analytical solutions for suspended and retained particles are derived. The model, which incorporates particle retention probability, is compared with the classical deep bed filtration model allowing a physical interpretation of the filtration coefficients. Comparison of the obtained analytical solutions for the proposed model with the classical model solutions allows concluding that the larger the particle capture probability, the larger the discrepancy between the proposed and the classical models

Modelagem e previsão da perda de injetividade em poços canhoneados

Waterflooding is a technique largely applied in the oil industry. The injected water displaces oil to the producer wells and avoid reservoir pressure decline. However, suspended particles in the injected water may cause plugging of pore throats causing formation damage (permeability reduction) and injectivity decline during waterflooding. When injectivity decline occurs it is necessary to increase the injection pressure in order to maintain water flow injection. Therefore, a reliable prediction of injectivity decline is essential in waterflooding projects. In this dissertation, a simulator based on the traditional porous medium filtration model (including deep bed filtration and external filter cake formation) was developed and applied to predict injectivity decline in perforated wells (this prediction was made from history data). Experimental modeling and injectivity decline in open-hole wells is also discussed. The injectivity of modeling showed good agreement with field data, which can be used to support plan stimulation injection wells

Modelo Estocástico para bloqueio de poros e redução de permeabilidade

Modeling transport of particulate suspensions in porous media is essential for understanding various processes of industrial and scientific interest. During these processes, particles are retained due to mechanisms like size exclusion (straining), adsorption, sedimentation and diffusion. In this thesis, a mathematical model is proposed and analytical solutions are obtained. The obtained analytic solutions for the proposed model, which takes pore and particle size distributions into account, were applied to predict the particle retention, pore blocking and permeability reduction during dead-end microfiltration in membranes. Various scenarios, considering different particle and pore size distributions were studied. The obtained results showed that pore blocking and permeability reduction are highly influenced by the initial pore and particle size distributions. This feature was observed even when different initial pore and particle size distributions with the same average pore size and injected particle size were considered. Finally, a mathematical model for predicting equivalent permeability in porous media during particle retention (and pore blocking) is proposed and the obtained solutions were applied to study permeability decline in different scenarios

Modelagem matemática para o transporte de partículas sujeitas a múltiplos mecanismos de retenção

Discrepancies between classical model predictions and experimental data for deep bed filtration have been reported by various authors. In order to understand these discrepancies, an analytic continuum model for deep bed filtration is proposed. In this model, a filter coefficient is attributed to each distinct retention mechanism (straining, diffusion, gravity interception, etc.). It was shown that these coefficients generally cannot be merged into an effective filter coefficient, as considered in the classical model. Furthermore, the derived analytic solutions for the proposed model were applied for fitting experimental data, and a very good agreement between experimental data and proposed model predictions were obtained. Comparison of the obtained results with empirical correlations allowed identifying the dominant retention mechanisms. In addition, it was shown that the larger the ratio of particle to pore sizes, the more intensive the straining mechanism and the larger the discrepancies between experimental data and classical model predictions. The classical model and proposed model were compared via statistical analysis. The obtained p values allow concluding that the proposed model should be preferred especially when straining plays an important role. In addition, deep bed filtration with finite retention capacity was studied. This work also involves the study of filtration of particles through porous media with a finite capacity of filtration. It was observed, in this case, that is necessary to consider changes in the boundary conditions through time evolution. It was obtained a solution for such a model using different functions of filtration coefficients. Besides that, it was shown how to build a solution for any filtration coefficient. It was seen that, even considering the same filtration coefficient, the classic model and the one here propposed, show different predictions for the concentration of particles retained in the porous media and for the suspended particles at the exit of the media

CERAMIC MATERIAL FROM SEWAGE SLUDGE AS SUPPORT MATERIAL SUPPLY WATER FILTRATION

This study shows a possibility of using municipal sewage sludge after thermal treatment in the production of a filtering material to water treatment. Due to the fast urbanization and implementation of high standards for effluent in many countries in recent years, the sewage sludge is being produced in an ever increasing amount. Therefore, the use of sludge is a suitable solution for the expected large quantity of sludge. Dehydration of sludge was performed by controlled heating at temperatures of 1100 degrees C, 850 degrees C, 650 degrees C, 350 degrees C for 3 hours. After thermal treatment the sludge was characterized by X-ray fluorescence, TG/DTG/DTA, residue solubilization and residue lixiviation tests. The aim of the present work was to observe, thought the characterization techniques, if the treated sewage sludge is or not adequate to be used as filter material to water treatment. It will be verified which treatment temperature of the sludge offer possibility to its use in water treatment without carrying pollutants in concentrations out of the standards.

Sintered Sewage Sludge As Support Material Used In Drinking Water Filtration

The processing of industry and domestic effluents in wastewater treatment plants reduces the amount of polluted material and forms reusable water and dehydrated sludge. the generation of hazardous municipal sludge can be decreased, as well as the impact on surface and underground water and the risk to human health. The aim this study is to verify the possibility to use sintered sewage sludge as support material after thermal treatment in the production of a filtering material to water supply systems. After thermal treatment the sewage sludge ash was characterized by X-ray fluorescence (XRF), leaching test and water solubilization. Dehydration of sludge was performed by controlled heating at temperatures of 180 degrees C, 350 degrees C, 600 degrees C, 850 degrees C and 1000 degrees C for 3 hours.

Anaerobic bio-digestion of concentrate obtained in the process of ultra filtration of effluents from tilapia processing unit

The objective of the present study was to evaluate the efficiency of the process of biodigestion of the protein concentrate resulting from the ultrafiltration of the effluent from a slaughterhouse freezer of Nile tilapia. Bench digesters were used with excrements and water (control) in comparison with a mixture of cattle manure and effluent from the stages of filleting and bleeding of tilapias. The effluent obtained in the continuous process (bleeding + filleting) was the one with highest accumulated population from the 37th day, as well as greatest daily production. Gases composition did not differ between the protein concentrates, but the gas obtained with the use of the effluent from the filleting stage presented highest methane gas average (78.05%) in comparison with those obtained in the bleeding stage (69.95%) and in the continuous process (70.02%) or by the control method (68.59%).

EFFECT of DIFFERENT SOLID AMOUNTS IN THE PHYSICAL and MICROSCOPICAL PROPERTIES of SiC POROUS CERAMICS

The presence of pores in ceramics is directly related to the chosen forming process. So, in the starch consolidation method, the ceramics show, after burning, pores with morphology similar to that presented by this organic material. on the other hand, the increase in solid load leads up to alterations in dispersion viscosity, increasing the thermal stresses during drying and sintering processes. In order to verify the solid percentage influence in ceramic final properties, samples were prepared with silicon carbide in different compositions using or not starch as binder agent and pore forming element. The characterization of the ceramic pieces was performed by superficial roughness measurements, porosity besides by optical and scanning electron microscopy. The results showed ceramics with SiC and starch presented physical and microscopic properties slightly higher in relation to those with only ceramic powder in their composition. The presence of organic material, agglomerated and foam during the forming were essential for the final properties of the studied samples.