Disposal of effluent from pulp and paper industry is one of the major problems faced by entrepreneur in view of increasing environmental standards day by day. In addition to this, industry loses economic value by disposing the effluent or selling it for a low price to other industries. Therefore, to address this problem, in the present study, 2 pulp mill effluents were selected to recover the economic value namely Hemi caustic stream and brown stock filtrate. As far as the recovery of value of hemi caustic stream is concerned, freeze concentration technique was used to recover water in its pure form and membrane separation was used to separate hemi cellulose from effluent so that permeate can be used as a pure source of caustic elsewhere. In addition to this, hemi caustic stream was subjected to acid hydrolysis to convert hemi cellulose into sugars. These sugars can be used to produce bioethanol. As far as the recovery of values of brown stock filtrate is concerned, it was proposed to recycle brown stock filtrate as a source of washing water for brown stock washers in the mill. However, continuous recycling of brown stock filtrate into the process causes building up of extractives in the recycle stream which in turn might deposit on the pulp and affects the quality of the pulp. Therefore, it was decided to separate extractives from the brown stock filtrate before recycle it into the mill. Dissolved Air flotation technique was used to achieve the above mentioned objective. An attempt was made to develop an improved and most reliable version of existing extractives measurement method to quantify the performance of Dissolved air flotation technique.

A principal limitação do uso de MgO em refratários é a facilidade com que reage com água formando hidróxido de magnésio (Mg(OH)2) que, devido à sua menor densidade, causa tensões destrutivas nesses materiais. Para outras aplicações, no entanto, a reação de hidroxilação do MgO é necessária, como em produção de agentes antichamas, em compósitos poliméricos e na correção de pH de solos. Observações empíricas na literatura demonstraram que diferentes fontes de MgO possuem reatividades e sensibilidades à hidroxilação distintas. Este estudo analisou o impacto de variáveis externas (por exemplo, a liberação de calor que ocorre durante a reação ou o volume das amostras) que ainda não foi completamente compreendido. O impacto auto-catalítico da temperatura reacional e da exotermia da reação foi avaliado. Por meio de medidas de temperatura in situ e de grau de hidroxilação termogravimétrico, também foram estudados os impactos do volume das amostras testadas e da concentração de sólidos nas suspensões, por meio de medidas de temperatura in situ e termogravimetria. Analisou-se também as principais diferenças estruturais entre duas principais fontes de MgO (sínter de MgO e magnésia cáustica): morfologia de partículas, densidade e área superficial específica. Em seguida, os mecanismos de hidroxilação em suspensões aquosas e seus efeitos foram avaliados por meio de testes de hidroxilação seguidos de termogravimetria, difração de raios-X, medidas de condutividade iônica, densidade, área superficial específica e microscopia eletrônica, e relacionado com as características físico-químicas e morfológicas das respectivas fontes de MgO. Pôde-se constatar que diferenças significativas entre a temperatura nominal do meio reacional e no interior da amostra podem afetar a cinética de hidroxilação do material. O volume e a concentração de sólidos variáveis também podem acentuar consideravelmente os efeitos da exotermia e gerar gradientes de hidroxilação. Também se verificou que a morfologia e a quantidade do Mg(OH)2 formado mudam significativamente dependendo do precursor e em função das condições de tempo-temperatura. / The use of MgO in refractories is restrict due to the easy reaction with water forming magnesium hydroxide (Mg(OH)2). Its lower density causes compressive stresses that can crack their structure. On the other hand, for applications such as the production of flame retardant agents for polymer composites and pH correcting of contaminated soil, this reaction is necessary. Empirical observations in the literature have shown that different sources of MgO have district levels of chemical reactiveness. The present study analyzed the main structural differences between the two main sources of MgO (magnesia sinter and caustic magnesia): particle morphology, density and specific surface area. The mechanisms of hydroxylation of these raw materials in aqueous suspensions and their effects were followed by hydroxylation tests, X-ray diffraction, ionic conductivity, density, specific surface area and scanning electron microscopy. They were associated with the physical characteristics morphological, chemical of these MgO sources. The impact of external variables (e.g., heat release during the reaction or the sample volume), that was not yet completely understood, was also evaluated through temperature measurements carried out in situ and hydroxylation degree accessed by thermogravimetry. The effects of samples volume and solid concentration in aqueous suspension were also investigated. The results showed that differences between the ambient temperature and reaction inside sample temperature can affect the kinetics of hydroxylation of the material. The samples volume and solids concentration can also enhance significantly the effects of heat release and generate gradients of hydroxylation. It was also found out that the morphology and the amount of Mg(OH)2 formed can change depending on the precursor and on the time-temperature conditions.

Spent caustic liquors (SCL) generated from crude oil refineries have characteristics of high COD (chemical oxygen demand) contents and relatively small generation rates as compared with general wastewater ones. The odorous naphthenates, phenolates, and sulfides in the liquors adversely affect the normal operation of the related wastewater treatment plants and effluent water qualities. This study aims at the reduction of COD in a naphthenic spent caustic liquor generated from a domestic refinery with crude processing and naphtha cracking units. Primary tests indicated that around 50% of the COD in the SCL could be biodegraded. Chemical oxidation methods were tried to possibly upgrade the COD removal. Experiments indicated that acidification of the SCL sample to pH 2-3 could reduce the COD from an average of 51,600 to 20,800 mg/L by removing the separated naphthenic acids. Fenton¡¦s method with oxidants of 20 mL/L 35% H2O2 and FeSO4.7H2O 5 g/L, oxidation time of 1 hour at conditions of pH 2-3 and 80-100oC, could reduce the COD of the acidified SCL from an average of 20,800 to 11,100 mg/L. The overall COD removal was around 78% and the efficiency is comparable to that of a traditional Wet Air Oxidation (WAO) process of around 75%. Economic analysis indicated that for treating the SCL of 80 m3/day by the traditional WAO process, an initial equipment cost of 10 millions USD and annual operating cost of around 1.5 millions USD are required. By the developed acidification-Fenton¡¦s process, an initial equipment cost of 0.7 million USD and annual operating cost of around 0.5 million USD are expected. The developed process can be superior to the WAO one.

Recovery of caustic solution from mercerizing wastewaters of a denim producing textile mill was performed by using membrane technologies. A comprehensive characterization study was conducted to develop the treatment scheme. Highly alkaline and warm condition of wastewater has induced using membranes made of Polyethersulfone (PES). Conducted pretreatment applications such as microfiltration, flocculation and centrifuge have been found unsuccessful to improve further treatment capacities. Hence recovery studies which are UF, NF and pilot-system membrane applications have been implemented without any pretreatment. Effects of TMP and CFV on UF and NF processes were investigated and optimum operating conditions have been defined. UF has accomplished almost complete caustic solution recovery beside high COD and color retentions 84 % and 94 % under 4.03 bar TMP and 0.79 m/s CFV at 20&plusmn / 2 0C. Because of higher capacity of NF membranes also in acid and alkali recovery area, NF process has been studied in addition to UF. NF has also provided nearly complete NaOH recoveries with 92 % COD and 98 % color retentions under 4.03 bar TMP and 0.79 m/s CFV at 20&plusmn / 2 0C. Furthermore temperature effect was also studies by repeating the same processes at 40&plusmn / 2 0C considering the real operating conditions. Temperature has affected the system performance positively with regards to flux increases with insignificant loses in recovery and retention capacities. Lastly a pilot plant study has been conducted and it was found successful despite some operational difficulties due to high inorganic content and temperature of wastewater.

Corrosion and stress corrosion cracking of structural components cost an estimated $300 billion annually in the United States alone and are a safety concern for a number of industries using hot alkaline environments. These process environments may contain different amounts of sulfide and chloride; however, the combined role of these ions on the stress corrosion cracking of duplex stainless steels, which are widely used because of their generally reliable performance, had never been studied. This study shows that chlorides in sulfide-containing caustic environments actually have a significant influence on the performance of these alloys. A mechanism for stress corrosion cracking of duplex stainless steels in hot alkaline environments in the presence of sulfide and/or chloride was proposed. Microstructural and environmental aspects were studied using mechanical, electrochemical, and film characterization techniques. The results showed that selective corrosion of the austenite phase depended on percent sulfidity, alkalinity, and chloride content. Chlorides enhanced crack initiation and coalescence along the austenite/ferrite phase boundaries. Unstable passivity of duplex stainless steels in hot alkaline-sulfide environments was due to anion adsorption on the surface leading to defective film formation. Chlorides and sulfide available at the electrolyte/film surface reduced the charge transfer resistance and shifted the response of the films to lower frequencies indicating the films became more defective. The surface films consisted of an outer, discontinuous layer, and an inner, barrier layer. Fe, Mo, and Mn were selectively dissolved in alkaline and alkaline-sulfide environments. The onset of stress corrosion cracking was related to the extent of selective dissolution and was consistent with a film breakdown and repair mechanism similar to slip-step dissolution. Recommendations for reducing the susceptibility of duplex stainless steels to stress corrosion cracking in sulfide-containing caustic environments include reducing the chloride to hydroxide ratio and alloying with less Mo and Mn. The results will impact the petrochemical, pulp and paper, and other process industries as new duplex grades can be developed with optimal compositions and environments can be controlled to extend equipment life.

Duplex stainless steels (DSS) with roughly equal amount of austenite and ferrite phases are being used in industries such as petrochemical and pulp and paper mills. However, many DSS grades have been reported to undergo corrosion and stress corrosion cracking in some aggressive environments such as chlorides and sulfide-containing caustic solutions. Although stress corrosion cracking of duplex stainless steels in chloride solution has been investigated and well documented in the literature, SCC mechanisms for DSS in caustic solutions were unknown. Microstructural changes and environmental factors, such as pH of the solution, temperature, and resulting electrochemical potential also influence the SCC susceptibility of duplex stainless steels. In this study, the role of material and environmental parameters on corrosion and stress corrosion cracking of duplex stainless steels in caustic solutions were investigated. Results showed that the austenite phase in the DSS is more susceptible to crack initiation and propagation in caustic environment, which is different from that in the low pH chloride environment where the ferrite phase is the more susceptible phase. This study also showed that alloy composition and microstructural changes in duplex stainless steels due to different heat treatments could affect their SCC susceptibility. Moreover, corrosion rates and SCC susceptibility of DSS was found to increase with addition of sulfide to caustic solutions. Corrosion films on DSS indicated that the metal sulfide compounds formed along with oxides at the metal surface in the presence of sulfide containing caustic environments made the steel susceptible to SCC initiations. The overall results from this study helped in understanding the mechanism of SCC in caustic solutions. Favorable slip systems in the austenite phase of DSS favors slip-induced local film damage thereby initiating a stress corrosion crack. Repeated film repassivation and breaking, followed by crack tip dissolution results in crack propagation in the austenite phase of DSS alloys. Result from this study will have a significant impact in terms of identifying the alloy compositions, fabrication processes, microstructures, and environmental conditions that may be avoided to mitigate corrosion and stress corrosion cracking of DSS in caustic solutions.

Orientador: Erika Veruska Paiva Ortolan / Resumo: Introdução: Por volta de oitenta por cento dos acidentes envolvendo ingestão de cáusticos ocorrem em crianças. A estenose cáustica do esôfago é a sua principal complicação com grande morbidade. Lesões neoplásicas esofágicas podem desenvolver-se como uma complicação tardia desta estenose com um tempo médio de aparecimento entre o acidente e o desenvolvimento neoplásico de 15 a 30 anos. Considerando este risco, biopsias seriadas do esôfago são recomendadas com o objetivo de detecção precoce de displasias. Assim, um conhecimento abrangente da relação biológica entre cáusticos e neoplasia esofágica é de grande importância na identificação de novos biomarcadores que possibilitariam tratamento precoce. MicroRNAs (miRNAs) são RNAs pequenos, não codificadores de proteínas que regulam importantes processos celulares e têm se mostrado como robustos biomarcadores. O perfil global de expressão de miRNAs nesta população, seguida da identificação dos miRNA-alvo, pode levar à identificação da presença e magnitude do dano ao material genético em amostra de tecido esofágico obtido de pacientes portadores de estenose cáustica. Objetivos: Determinar o perfil global da expressão de miRNAs em células da mucosa esofágica de crianças portadoras de lesões por ingestão de cáusticos, com o objetivo de identificar miRNAs como biomarcadores associados a tumorigênese esofágica nesta população específica. Materiais e Métodos: Vinte e sete amostras esofágicas fixadas em formalina e embebidas em parafina (F... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Background: 80% of the caustic ingestions occur in children. Esophageal stricture is a major chronic complication with great morbidity. Esophageal neoplasms may develop as a late complication of caustic injury with a mean time between caustic ingestion and cancer development of 15-30 years. Serial biopsies are recommended aiming early detection of premalignant changes. Thus a comprehensive knowledge of biological relation between caustic and esophageal cancer is of major importance to identify the biomarkers that could enable an early treatment. MicroRNAs (miRNAs) are small non-coding RNA molecules and regulate key cellular processes during tumorigenesis and have been demonstrated as an useful diagnostic, prognostic and predictive biomarkers. Global miRNA expression profiling analysis in this population, followed by the identification of miRNA target genes, may lead to the identification of the presence and magnitude of damage to genetic material in a sample of esophageal tissue obtained from patients with caustic stenosis. Objectives: We aimed to identify global microRNA (miRNA) expression changes in cells of the esophageal mucosa from children with caustic lesions compared to paired macroscopic and microscopically normal esophageal tissue. Patient and Methods: 27 formalin fixed, paraffin embedded (FFPE) esophageal samples from 15 patients were divided into two groups according to the time elapsed after the injury (Group A: less than 5 years, Group B: more than 5 years). Tho... (Complete abstract click electronic access below) / Doutor

[pt] Este trabalho apresenta um estudo do comportamento mecânico, em especial nas características de resistência, de um solo laterítico submetido à contaminação de licores cáusticos a diferentes concentrações. O programa experimental envolveu ensaios de caracterização, ensaios químicos, difração de raios-X, microscopia eletrônica de varredura e ensaios triaxiais com diferentes valores de concentrações cáusticas. Propriedades mecânicas foram determinadas mediante a execução de ensaios triaxiais CID a diferentes concentrações cáusticas, assim como as interações físico- químicas que foram determinadas mediante ensaios químicos de pH, capacidade de troca catiônica e ataque sulfúrico. Os resultados do programa experimental demonstraram uma acentuada variação de volume do solo, a qual está ligada à presença dos licores cáusticos e, por outro lado, também indicaram que os parâmetros de resistência ao cisalhamento do solo são pouco afetados pelos licores cáusticos. / [en] This work presents the results of a laboratory study on the effects of infiltration of a caustic liqueur on the stress- strain- strength behavior of a sandy lateritic soil. The experimental program consisted of general characterization,chemicals tests, X-ray diffraction analysis, electron microscopy and triaxial tests using the caustic liqueur at different concentrations.Mechanic and hydraulic properties were obtained performing triaxial CID tests with different caustic concentrations. Physical- chemical interactions were evaluated through of determination of pH, cation exchange capacity and sulfuric attack tests. The results obtained showed that soil suffers large volume changes under percolation of the liqueur, with these changes being a function of the caustic concentration, on the other hand, the shear strength parameters are little affected by the liqueur.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Esta pesquisa avaliou o sistema microaerÃbio como estratÃgia simples de remoÃÃo de sulfeto de hidrogÃnio da fraÃÃo gasosa com vistas ao controle de odor e qualidade do biogÃs em estaÃÃes de tratamento de esgotos (ETE). Adicionalmente, foi avaliado o impacto da microaeraÃÃo na estabilidade operacional do sistema anaerÃbio, alÃm de um estudo comparativo entre a tecnologia microaerÃbia e absorÃÃo quÃmica (NaOH) na remoÃÃo de H2S presente no biogÃs. Os experimentos foram conduzidos em fluxo contÃnuo em dois reatores mesofÃlicos (28ÂC) construÃdos em acrÃlico e alimentados com Ãgua residuÃria sintÃtica. O experimento foi dividido em quatro fases de operaÃÃo, para ambos os reatores, de modo que as duas primeiras fases foram para a estabilizaÃÃo dos reatores. Na fase III foi introduzido sulfato de sÃdio, em uma relaÃÃo DQO/SO42- de aproximadamente 7. Por fim, na fase IV foram adicionados aos reatores os sistemas de remoÃÃo de H2S, ou seja, o reator 1 (R1) foi operado em condiÃÃes estritamente anaerÃbias com lavagem cÃustica do biogÃs, enquanto que o reator 2 (R2) foi modificado para operar em condiÃÃes microaerÃbias a partir da injeÃÃo de 0,2 mL.min-1 de ar atmosfÃrico em seu headspace. Foram realizadas anÃlises fÃsico-quÃmicas no afluente e efluente dos reatores, como DQO, pH, alcalinidade, sulfato, sulfeto dissolvido e feita a caracterizaÃÃo do biogÃs em termos de N2, O2, CH4, CO2, H2S, NH3. Foi observado nas fases III e IV que ambos os reatores apresentaram boa estabilidade em termos de remoÃÃo de DQO (>80%) e remoÃÃo de sulfato (>90%). Durante o processo microaerÃbio o oxigÃnio adicionado nÃo modificou a remoÃÃo da matÃria orgÃnica. Em relaÃÃo à qualidade do biogÃs, observou-se que o conteÃdo de metano no sistema provido de microaeraÃÃo foi reduzido de 76% (Fase III) para 52% (Fase IV), devido à diluiÃÃo com o nitrogÃnio presente no ar atmosfÃrico. Entretanto, ao retirar a interferÃncia do N2 foram obtidas concentraÃÃes prÃximas ao da fase totalmente anaerÃbia (Fase III), indicando, portanto, que as arquÃias produtoras de metano nÃo foram afetadas significativamente pelo oxigÃnio introduzido. Em relaÃÃo à remoÃÃo de sulfeto, o processo microaerÃbio foi efetivo na reduÃÃo tanto na fase lÃquida como na gasosa, com remoÃÃo mÃdia de 42% e 94%, respectivamente. O processo de lavagem do biogÃs aplicado no R1 promoveu remoÃÃo de 100% do H2S do biogÃs bem como 100% de CO2 e NH3. Dessa forma, tanto o processo microaerÃbio como a lavagem foram eficientes na remoÃÃo do H2S e podem ser empregados no controle de odor em ETE. O estudo econÃmico preliminar das duas tecnologias (microaerÃbio e lavagem cÃustica) mostra que apesar do investimento inicial necessÃrio para a instalaÃÃo do processo microaerÃbio e os custos de eletricidade para aeraÃÃo contÃnua dos reatores, os custos operacionais com a aquisiÃÃo do reagente quÃmico no processo de lavagem superam os custos totais ao longo do tempo. Por fim, espera-se que o sistema microaerÃbio seja mais vantajoso do que a lavagem quÃmica tanto sob o ponto de vista econÃmico em uma anÃlise mais detalhada quanto na anÃlise de ciclo de vida, mas que novos estudos devam ser conduzidos para comprovar tais hipÃteses. / This research work evaluated the feasibility of the micro-aerobic process to remove sulfide from biogas in order to control biogas quality and odors in wastewater treatment plants (WWTP). Moreover, the impact of micro-aeration over the anaerobic system stability was evaluated, and a comparison of the micro-aerobic biotechnology with a chemical absorption process (NaOH) for sulfide removal from biogas was performed. The experiments were performed in a continuous mode in two acrylic-constructed mesophilic (28 C) bioreactors fed with synthetic wastewater. The experiment consisted into four operation phases for both reactors, being the two first phases used for the stabilization of the systems. During the operation phase III, sodium sulfate was introduced into the reactors at a COD/SO42- ratio of ~7. At the operation phase IV, the hydrogen sulfide removal systems were applied into the reactors, i.e. the reactor 1 (R1) was operated under strictly anaerobic conditions with a biogas caustic scrubbing, and the reactor 2 (R2) was operated at micro-aerobic conditions by using a 0,2 mL.min-1 atmospheric air injection into the headspace of the system. Physical-chemical analyses, such as COD, pH, alkalinity, sulfate, dissolved sulfide was performed, and biogas was characterized in terms of N2, O2, CH4, CO2, H2S, NH3. During the operation phases III and IV, both rectors showed a good stability in terms of COD removal (>80%) and sulfate removal (>90%). During the micro-aerobic process, the introduced oxygen did not affect organic matter removal. Regarding biogas quality, content of methane in the micro-aerobic system decreased to a value of 76% (phase III) and 52% (phase IV), due to the dilution with the nitrogen present in air. Meanwhile, when nitrogen interference was removed, similar concentrations to the anaerobic phase (phase III) were obtained, suggesting that methanogenic archaea was not significantly affected by the introduced oxygen. Regarding to sulfide removal, the micro-aerobic process was effective, both removing sulfide from the liquid and the gaseous phases, showing an average removal of 42% e 94%, respectively. The biogas cleaning process applied to R1 showed a 100% sulfide removal from biogas and 100% removal of CO2 and NH3. In this way, both, the micro-aerobic and the scrubbing processes were efficient for sulfide removal and can be used for odor control in WWTP. The preliminary economical study considering two technologies (micro-aerobic and the scrubbing) showed that even taking into account the initial investment for the aeration and the electricity costs for the continuous aeration, the operational costs with the chemical acquisition for the scrubbing process are much higher. Likely, the micro-aerobic process will be more advantageous than the scrubbing process after a detailed economic analysis or a life cycle assessment, however, it is necessary to perform more research in order to confirm these hypotheses.

A principal limitação do uso de MgO em refratários é a facilidade com que reage com água formando hidróxido de magnésio (Mg(OH)2) que, devido à sua menor densidade, causa tensões destrutivas nesses materiais. Para outras aplicações, no entanto, a reação de hidroxilação do MgO é necessária, como em produção de agentes antichamas, em compósitos poliméricos e na correção de pH de solos. Observações empíricas na literatura demonstraram que diferentes fontes de MgO possuem reatividades e sensibilidades à hidroxilação distintas. Este estudo analisou o impacto de variáveis externas (por exemplo, a liberação de calor que ocorre durante a reação ou o volume das amostras) que ainda não foi completamente compreendido. O impacto auto-catalítico da temperatura reacional e da exotermia da reação foi avaliado. Por meio de medidas de temperatura in situ e de grau de hidroxilação termogravimétrico, também foram estudados os impactos do volume das amostras testadas e da concentração de sólidos nas suspensões, por meio de medidas de temperatura in situ e termogravimetria. Analisou-se também as principais diferenças estruturais entre duas principais fontes de MgO (sínter de MgO e magnésia cáustica): morfologia de partículas, densidade e área superficial específica. Em seguida, os mecanismos de hidroxilação em suspensões aquosas e seus efeitos foram avaliados por meio de testes de hidroxilação seguidos de termogravimetria, difração de raios-X, medidas de condutividade iônica, densidade, área superficial específica e microscopia eletrônica, e relacionado com as características físico-químicas e morfológicas das respectivas fontes de MgO. Pôde-se constatar que diferenças significativas entre a temperatura nominal do meio reacional e no interior da amostra podem afetar a cinética de hidroxilação do material. O volume e a concentração de sólidos variáveis também podem acentuar consideravelmente os efeitos da exotermia e gerar gradientes de hidroxilação. Também se verificou que a morfologia e a quantidade do Mg(OH)2 formado mudam significativamente dependendo do precursor e em função das condições de tempo-temperatura. / The use of MgO in refractories is restrict due to the easy reaction with water forming magnesium hydroxide (Mg(OH)2). Its lower density causes compressive stresses that can crack their structure. On the other hand, for applications such as the production of flame retardant agents for polymer composites and pH correcting of contaminated soil, this reaction is necessary. Empirical observations in the literature have shown that different sources of MgO have district levels of chemical reactiveness. The present study analyzed the main structural differences between the two main sources of MgO (magnesia sinter and caustic magnesia): particle morphology, density and specific surface area. The mechanisms of hydroxylation of these raw materials in aqueous suspensions and their effects were followed by hydroxylation tests, X-ray diffraction, ionic conductivity, density, specific surface area and scanning electron microscopy. They were associated with the physical characteristics morphological, chemical of these MgO sources. The impact of external variables (e.g., heat release during the reaction or the sample volume), that was not yet completely understood, was also evaluated through temperature measurements carried out in situ and hydroxylation degree accessed by thermogravimetry. The effects of samples volume and solid concentration in aqueous suspension were also investigated. The results showed that differences between the ambient temperature and reaction inside sample temperature can affect the kinetics of hydroxylation of the material. The samples volume and solids concentration can also enhance significantly the effects of heat release and generate gradients of hydroxylation. It was also found out that the morphology and the amount of Mg(OH)2 formed can change depending on the precursor and on the time-temperature conditions.