Esta pesquisa se propõe a investigar as representações sociais acerca do termo \"Química Ambiental\" entre estudantes iniciantes (segundo semestre) e depois de quatro anos em andamento nos cursos de Bacharelado em Química Ambiental e Licenciatura em Química do Instituto de Química da Universidade de São Paulo. Adotamos como referencial de investigação a Teoria das Representações Sociais e como metodologia a técnica da associação livre de palavras associada à elaboração de um texto. Os resultados foram analisados através da freqüência e ordem média de evocação das palavras para delinear o núcleo central da representação social, além dos elementos periféricos. Nos textos são identificadas unidades de análise que são utilizadas para construção de mapas cognitivos. A associação das palavras mais evocadas com as leituras dos mapas cognitivos para cada aluno proporcionou a construção de um mapa conceitual representativo da visão sobre \"Química Ambiental\" para cada uma das turmas analisadas. De uma forma geral, os iniciantes tanto da Licenciatura em Química como da Química Ambiental apresentaram uma visão naturalista de meio ambiente e também revelaram uma concepção de Educação Ambiental sobre o ambiente, em que bastaria munir as pessoas com informações e fatos relacionados aos problemas ambientais para resolvê-los. Os estudantes iniciantes de ambos os cursos apresentaram uma concepção preservacionista do meio ambiente, sendo mais enfatizada a necessidade de conscientização das pessoas pelos licenciandos. Por outro lado, os bacharelandos em Química Ambiental fazem bastante menção à pesquisa com vistas ao tratamento da poluição e uma visão de remediação é predominante. A diferença entre as representações sociais verificadas entre os alunos das duas modalidades podem estar relacionadas, em parte, à representação social dos alunos sobre o seu papel enquanto profissionais nos aspectos que envolvem a Química Ambiental. Os alunos concluintes representam a Química Ambiental ainda com idéias preservacionistas. Um aspecto positivo, porém, é o aparecimento da idéia de Química Verde em ambos os grupos. As idéias centrais apresentadas pelos estudantes iniciantes em ambos os cursos incluem poluição, meio ambiente, reciclagem, e preservação. Essas mesmas idéias estavam presentes também no grupo de concluintes, o que significa que poderiam ser consideradas constituintes do núcleo central da representação, e que se mantém durante os cursos. Entretanto, foi possível notar a emergência de um elemento periférico de destaque: a Química Verde, que pode ser considerado representativo do amadurecimento do conhecimento técnico dos alunos ao longo do curso de graduação, podendo ser visto como incorporado ao flexível sistema periférico. / This research aims to investigate social representations of environmental chemistry among chemistry student-teachers and environmental chemistry majors from the Institute of Chemistry at the University of São Paulo. Two groups were considered: students enrolled in the second and in the eighth semesters of their respective courses, in order to investigate changes over time. The Theory of Social Representations was adopted as the theoretical reference for this study. The methodology included the technique of free evocation of words, as well as the writing of a text. Results were analyzed considering the frequency and the word evocation mean order, to define the central core and the peripheral elements of the social representation for each group of students. Analysis units were identified in the texts and were used to construct cognitive maps. The association between the most evocated words and individual cognitive maps resulted in a collective conceptual map for each group. Freshmen students from both investigated majors presented a naturalist view of the environment, and a conception of environmental education that can be described as \"about the environment\", in which it would be enough to provide people with information and facts related to the environment to address environmental problems. A preservationist view of the environment was also dominant in both groups, and the need to enhance awareness of people towards environmental issues is specially emphasized by the student-teachers. On the other hand, environmental chemistry majors lay emphasis on the relation between environmental chemistry and research on pollution treatment, and the remediation view is prevalent. The differences between social representations verified in both groups can be partially related to the roles as regard to environmental chemistry within the different professions. Students in the eighth semesters of their respective courses still present strong influence from a preservationist view of the environment. A positive aspect that can be stressed is the rising of ideas related to Green Chemistry in both groups. Representations of freshmen students show a central core founded upon the ideas of pollution, environment, recycling and preservation. The social representation for the group of advanced students rests on the very same ideas. This means that these ideas can be considered as part of the central core of the representation and are maintained during the courses. However, it was possible to notice the incorporation of the peripheral idea associated to Green Chemistry during the undergraduate courses. This can be considered as a result of a growth on technical knowledge which is incorporated to the flexible peripheral elements of the social representations

<p>Organic nitrogen compounds are important in environmental systems because they are prevalent in natural waters but are also components of polymers within membrane filters that are used for water treatment. In both of these cases, these compounds can be exposed to free chlorine during disinfection, which can trigger a set of reactions that can form a host of different halogenated by-products. When such by-products form during water treatment disinfection, these by-products, known as nitrogen-based disinfection by-products (N-DBPs), can be highly toxic and affect human and ecosystem health. Alternatively, when such reactions occur during membrane filtration, the organic nitrogen compounds, which are embedded within the upper layer polymer structure of the membrane filter, can degrade when free chlorine is applied. Therefore, this research was aimed at exploring the chemistry behind how specific types of organic nitrogen compounds which are found in these applications, such as tertiary amines and amides, react with free chlorine. It particularly focused on assessing the kinetics and by-product formation of these reactions under variable water quality conditions (e.g., pH, halide concentrations, and precursor doses).</p> <p> </p> <p>More specifically, in the first phase of this work, the roles of tertiary amines in enhancing disinfection by-product (DBP) formation, such as trihalomethanes (THMs) and haloacetic acids (HAAs), during chlorination of aromatic compounds were studied. The results indicated that in synthetic solutions, chloroform (CHCl₃) and trichloroacetic acid (TCAA) were enhanced by up to 20× with tertiary amines at low dose ([tertiary amine]₀ = 0.5×[aromatic compound]₀). The enhancement effect was also dependent on the aromatic compound type, tertiary amine type and dose, and water conditions such as pH and bromide concentrations. Thus, THMs and HAAs were predicted to be enhanced when the aromatic compound reacted with R₃N-X⁺ (X=Br or Cl) and was not outcompeted by aromatic compound or tertiary amine reaction with free chlorine or bromine alone. In the second phase of this work, the reaction kinetics, by-product formation, and overall mechanisms of a polyamide-based monomer with chlorine were evaluated under varying water conditions. The current known mechanism, Orton Rearrangement, was reevaluated, and new mechanisms were proposed, where it was found that N-halogenation and ring halogenation were two independent pathways. The ability to choose either pathway was highly dependent on the water quality condition of the aqueous solution. The roles of different chlorinating/brominating agents were also investigated where certain species-specific rate constants were obtained. For the N-halogenation pathway, only chlorination and no bromination occurred in which the reactivity of the chlorinating agents likely decreased such that ClO^->HOCl. However, for the ring halogenation pathway, both chlorination and bromination occurred in which the reactivity of the chlorinating and brominating agents decreased such that Cl₂ >HOCl, and BrCl > BrOCl > Br₂ > Br₂O > HOBr, respectively. Overall, this study suggests that a number of unique reactions can occur for various types of organic nitrogen compounds which: (i) allow them to affect water quality by enhancing DBP formation, (ii) but, when integrated into a polymer matrix used for water treatment, can induce reactions that lead to permanent structural damage of the polymer. In all cases, the extent of these reactions is strongly governed by the surrounding water matrix.</p>

Uma importante classe de poluentes do ar são os compostos orgânicos voláteis (VOCs), comumente encontrados na atmosfera de centros urbanos e industriais, em quantidades muito baixas. Os VOCs contribuem para episódios sérios de poluição. Eles participam ativamente na formação do smog fotoquímico, problema encontrado em muitos centros urbanos. Além do efeito tóxico à saúde humana, os VOCs podem apresentar impactos indiretos via produção fotoquímica de ozônio. Alguns VOCs encontrados no ar urbano são carcinogênicos. Diante do papel importante dos VOCs na química atmosférica, o objetivo geral deste projeto de pesquisa foi avaliar os VOCs emitidos por fontes antropogênicas e biogênicas na atmosfera urbana da cidade de São Paulo. As emissões antropogênicas foram avaliadas através de estudos de emissões veiculares em dois túneis da cidade de São Paulo. A atmosfera de um túnel fornece condições apropriadas para a medida da composição média das emissões veiculares. A caracterização química da atmosfera dos túneis mostra que as emissões veiculares se acumulam ao longo dos túneis causando níveis altos de poluição. Os freqüentes congestionamentos nas principais vias de acesso e nos túneis da Cidade de São Paulo tomam preocupante a exposição humana a poluentes tóxicos no ar. Para a avaliação das emissões biogênicas foram empregadas câmaras fechadas (sistema cuvette) para coletar os VOCs emitidos por plantas. Espécies de plantas que emitem uma quantidade significativa de isopreno e monoterpenos foram estudadas em alguns países do mundo. No entanto, nenhum estudo sobre emissão de VOCs por plantas foi feito na vegetação encontrada na cidade de São Paulo. Dessa maneira, foram realizadas amostragens de algumas plantas da vegetação típica da Mata Atlântica. Os valores de taxas de emissão de VOCs em &#181;g de carbono por hora e massa de folha seca (&#181;gC h-1 g-1) foram calculados para cada planta. Ocorreram variações nas taxas de emissão tanto entre as diferentes espécies de plantas (inter-espécies), como entre exemplares diferentes de uma mesma espécie (intra-espécies). / Volatile organic compounds (VOCs) are an important class of air pollutants, commonly found in urban and industrial atmospheres at low concentrations. VOCs contribute to serious episodes of air pollution. They play a major role in the formation of the photochemical smog, an air pollution problem often encountered in many urban centers. Besides the toxic effect to human health, VOCs may be responsible by indirect impacts, such as the photochemical production of ozone. Some VOCs found in urban air are carcinogenic. The goal of this study was to evaluate VOCs emitted by anthropogenic and biogenic sources in the urban atmosphere of São Paulo City since they have an important role in atmospheric chemistry. VOCs anthropogenic emissions were evaluated through vehicular emissions inside two urban road tunnels of São Paulo City. A tunnel atmosphere provides appropriate conditions for the measurement of the average composition of vehicular emission. The chemical characterization of the atmosphere of both tunnels showed that vehicular emissions accumulate inside the tunnels leading to high pollutants levels. VOCs biogenic emissions from plants were evaluated by using closed chambers (cuvette system). Species of plants that emit significant amounts of isoprene and monoterpenes were studied in some countries of the world. Nevertheless, no study about VOCs emissions had been done in the vegetation found in São Paulo City. Some typical plants of the Mata Atlântica were investigated. The VOCs emission rates expressed in &#181;g of carbon per hour and leaves dry weight (&#181;gC h-1 g-1) were calculated for each plant. Variations in the emissions rates were observed between different plants species (inter-species) and between different plants of the same species (intra-species).

Nanoparticles are increasingly incorporated into consumer products because of their unique, size-dependent properties. Although these properties are commercially appealing, data are lacking regarding the fate and reactivity of nanoparticles once incorporated into materials. This information gap prevents accurate assessment of hazards that these materials potentially present to consumers and the environment. To address this concern, new research is needed to investigate the reactivity and transformations of nanoparticles. This dissertation describes the use of an electron transparent characterization platform to observe nanoparticle transformations. Nanoparticles were tethered to the surface of an analysis platform, exposed to a variety of conditions, and evaluated for reactivity and response. The characterization of silver nanoparticles revealed the generation of new daughter nanoparticles on surfaces in ambient humid conditions. Our observations showed that the transport of material is highly dependent on relative humidity and that pH equilibria drives the deposition of new particles and degradation. We discovered, by applying these findings to macro-silver objects, that bulk silver generates new nanoparticles on surfaces. This illuminated the possibility of other, yet undiscovered, naturally occurring nanoparticles. In the second model system, 1.5 nm gold nanoparticles were tethered by a robust metal oxide bond from the terminal group of the stabilizing ligand. This strategy facilitated precise control over thiol ligand removal using a dilute ozone oxidation. Tracking particle oxidation over time allowed us to gain unprecedented control over core exposure, size maintenance, and surface tethering. This platform was also utilized as a proof-of-concept for direct observation of transformations in complex media. Ligand and core transformations were monitored in a variety of biologically relevant conditions using tethered nanoparticles. Morphological and chemical transformations were characterized and correlated to results from solution monitoring. The use of a platform based approach to evaluating the reactivity of nanoparticles in the environment holds promise for evaluations of nanoparticles and their transformation products. The demonstration of monitoring reactivity in systems equilibria, carefully controlled transformations, or complex media shows the versatility of this strategy. Only through the use of this analysis platform was the direct observation of nanoparticle transformations possible. This dissertation includes previously published, unpublished, and co-authored materials. / 10000-01-01

Foram efetuados estudos sistemáticos visando-se a determinação conjunta de As(III) e PbIII) por polarografia de pulso diferencial, conseguindo-se determinar 75 ppb de As(III) e 100 ppb de Po(II) em mistura, em eletrolito de suporte H2S04 2,0 M + NaCl 2,0 M, com Ep, respectivamente, -0.260 mV e -0.470 mV, com varredura de 2 mV/s e 1,0 s de tempo de gotejamento. Outros eletrolitos de suporte foram testados, sendo equivalentes na sua eficiência, tais como H2S04 2,0 M + HCl 2.0 M e Hcl 3,0 M. Conseguiu-se por biamperometria a determinação de 75 ppb de As(III) por titulação com íons bromato em H2S04 0,5 M e de 37,5 ppb de As (V) pelo método da adição de padrão, em H2S04 0,5 M e I- 1,0 x 10-3 M (a diferença de potencial entre os eletrodos foi de 100 mV). 37,5 ppb de As(III) podem ser determinados via coulométrica em tampão 7,0 - 8,5, com I2 gerado e biamperornetria como detector. / A systematic study was carried out for the simultaneous determination of As(III) and Pb(II) through differential pulse polarography and analytical method for both was established with 75 ppb As(III) and Pb(II) in 2.0 M H2S04 + 2.0 M NaCl, with Ep, respectively -0.260 mV and -0.470 mV at 25.0 ºC, 1.0 s dropping time and rate of 2 mV/s. Other support eletrolites were tested, being eguivalents in perfomance. They were 2.0 M H2S04 + 2.0 M HCl and 3.0 M HCl. Through biamperometry was achieved and analysis of 75 ppb As(III) by titration with KBr03 in H2S04 and 37.5 ppb As(V) by the standard addition method in 0.5 M H2S04 and 1.0 x 10-3 M I-. 37.5 ppb As(III) can be determined by titration with iodine generated coulometric cally with biamperometry being the sensor.

O uso de técnicas espectroscópicas para o estudo de questões ambientais é uma área de pesquisa que vem experimentando importante desenvolvimento em tempos recentes, e muitas linhas de investigação vêm sendo abertas. As características de sensibilidade e seletividade da técnica Raman intensificada pela superfície (SERS - Surface-enhanced Raman scattering) sugerem que ela pode ser muito útil para o estudo de amostras complexas, como as relacionadas à investigação de poluentes no ambiente. O enfoque dessa tese está voltado para o desenvolvimento de metodologias para a utilização do efeito SERS no estudo espectroscópico de diferentes classes de espécies químicas de interesse ambiental. É proposta a construção de substratos SERS de alto desempenho para uso como sensores analíticos na identificação, quantificação e estudo de aspectos relacionados à reatividade de hidrocarbonetos policíclicos aromáticos (HPA), compostos organofosforados, compostos triazínicos e compostos organoclorados. Dentre os substratos investigados, podemos mencionar nanopartículas de ouro e prata (nanobastões, nanocubos, nanofios e partículas bimetálicas) e nanopartículas de ouro e prata imobilizadas em filmes poliméricos. Buscamos estabelecer correlações entre morfologia e composição química das nanoestruturas e os mecanismos de adsorção das moléculas investigadas sobre os substratos metálicos. Utilizamos cálculos DFT (Density Functional Theory) para simular as interações adsorbato-nanopartícula possíveis, buscando o melhor entendimento dos processos de interação química entre as nanoestruturas metálicas e as substâncias de interesse. / The use of spectroscopic techniques to the study of environmental issues is an area of research that has been experiencing major development in recent times. The sensitivity and selectivity characteristics of surface-enhanced Raman scattering (SERS) suggest that this technique can be very useful for the study of complex samples, such as those related to the investigation of pollutants in the environment. The focus of this thesis is dedicated to the development of methodologies for the use of the SERS effect to the spectroscopic study of different classes of chemical species of environmental interest. The construction of high-performance substrates for SERS is investigated aiming for their use as analytical sensors, identification, quantification and study of aspects related to the reactivity of polycyclic aromatic hydrocarbons (PAH), organophosphorus compounds, organochlorine compounds and triazinic compounds. Among the investigated substrates, we mention colloidal gold and silver nanoparticles of different shapes (nanorods, nanocubes, nanowires and bimetallic particles) and gold and silver nanoparticles immobilized on polymeric films. We seek to establish correlations between morphology and chemical composition of nanostructures and adsorption mechanisms of the investigated molecules on the metal substrates. We use DFT calculations (Density Functional Theory) to simulate possible adsorbate-nanoparticle interactions, allowing a better understanding of the processes of chemical interaction between the metal nanostructures and the substances of interest.

Visando a determinação de baixas concentrações de H2O2, HSO3- e Hidroximetanosulfonato (HMS) em água de chuva, desenvolveu-se novos métodos amperométricos em fluxo com detecção em eletrodo de gota pendente de mercúrio. A determinação analítica de H2O2 baseou-se na sua oxidação (reversível) em meio alcalino (NaOH 11mM), no potencial de -0,07V vs Ag/AgCI, em célula de fluxo adaptada a polarógrafo comercial. O limite de detecção foi 0,1 &#181;M. Para obter melhor seletividade, utilizou-se medidas diferenciais com e sem adição da enzima catalase. Para o HSO3- mostrou-se mais favorável sua redução a -0,8V, em meio ácido (tampão de HAc/Ac· 12/12mM). A interferência do oxigênio dissolvido foi eliminada por desgaseificação contínua com nova versão de dispositivo anteriormente desenvolvido. A corrente residual foi determinada mascarando o sinal do HSO3- por adição de HCHO. O HM:S foi determinado indiretamente. Após sua decomposição em HSO3- e HCHO, em pH em tomo de 12, reverteu-se o pH do fluxo para meio ácido e procedeu-se a determinação do HSO3- liberado. Aplicou-se as metodologias desenvolvidas às amostras de água de chuva, durante período de 12 meses. Foram observadas variações das concentrações das referidas espécies químicas em diversos eventos de precipitações, acompanhando-se o ciclo das estações climáticas e a intensidade da radiação solar. As concentrações de H2O2 variaram entre 0,3 a 34&#181;M, HSO3- não foi encontrado no período, enquanto HMS apresentou concentrações entre 0,1 e 1,5&#181;M. / Aiming the detennination of traces of H2O2, HSO3- an hydroximethanesulfonate (HMS) in rain water, a new flow method was developed, with amperometric detection at the hanging mercury drop electrode. The analytical detennination of H2O2 was based on its (reversible) oxidation in alkaline mediwn (NaOH 11 mM), by fitting a new flow adapter to a commercial multimode stand with the electrode operated as HMDE at -0.07V versus Ag/AgCl. Detection limit was 0.1&#181;M. To increase selectivity, differential measurements were done by subtracting the residual current after destruction of the analyte with the enzyme catalase. For the determination of HSO3-, results were more favorable for its reduction at -0.8V in acidic medium (HAc/Ac-) buffer, 12mM/12mM). The residual current was determined by masking the HSO3- signal with HCHO. HMS was determined indirectly. After its decomposition in alkaline medium (pH around 12) into SO3-2 and HCHO, the pH is lowered to 1.5 before detection of the HSO3-. Interference of oxygen was overcome by in-line degassing with a new two channel version of a previously described vacuum operated permeation device. The new methods were applied to rain samples collected during a one year period. Concentration of H2O2 ranged from 0.3 to 34&#181;M. HSO3- was not detected during the period and HMS appeared at concentrations between 0.1 to 1.5&#181;M. Although difficult to interpret, the results show correlation with intensity of solar radiation and, less clearly, with the seasons of the year.

The objective of this study was to evaluate the chemical resistance of common shoe materials regularly worn in undergraduate chemistry laboratories by subjecting the materials to hydrochloric acid and sodium hydroxide. The materials tested were leather, canvas cotton, and polyester. Due to the lack of restriction on undergraduate laboratory footwear, the research discussed in this thesis is important to undergraduate universities. Currently, many universities across the nation only require undergraduate students to wear close-toed, close-heeled shoes in chemistry laboratories, and often the resistance of the shoe material to acids and bases may not be taken into careful consideration. Overall, the results of this experiment revealed that exposure to the different chemical concentrations of NaOH and HCl did not appear to negatively affect the structural integrity of the fabrics, but according to the mass spectrometry results gathered in this experiment, the three fabrics differed in individual complexities as well as in the compounds extracted following acid and base treatments.

Renewable sources such as cellulose derived biofuels are sought after in order to replace fossil fuel sources that are currently used to meet energy demands. Cellulose is a biological polymer composed of a chain of glucose molecules. Hydrolysis of cellulosic materials then has potential to serve as a source of renewable energy in the form of biofuels. The crystalline structure of cellulose is very stable, and current methods of catalyzed hydrolysis are inefficient for industrial application. This project explores the use of phosphomolybdic acid (PMA) in water to catalyze hydrolysis of microcrystalline cellulose. Temperature of hydrolysis was varied from 40 °C – 100 °C. The amount of soluble hydrolysis product was determined through wet oxidative total organic carbon analysis using a Hach method kit. Total organic carbon content is compared between equimolar amounts of PMA and sulfuric acid, the current industry preference. The yield of total organic carbon in parts per thousand (ppt) is directly correlated to increasing temperatures. Across these temperatures, PMA is more efficient than sulfuric acid in hydrolysis of cellulosic materials. Work is ongoing for glucose-specific product detection as well as evaluating the recyclability of the catalyst.

To investigate the interaction between nanoparticles and electromagnetic waves, a numerical simulation model based on FEM was built in this thesis. Numerical simulation is an important auxiliary research method besides experiments. The optical properties of nanoparticles consist of scattering, absorption, and extinction, and in the case of nanoparticle suspension, the transmission is also involved. This thesis addressed two typical applications based on the established model, one was regarding the nanofluids for solar energy harvesting, and the other was regarding the optical properties of atmospheric soot. In the case of the nanofluids solar energy harvesting, the established model provided a convenient and rapid screening of potential nanoparticles and nanofluids candidates for solar energy harvesting. A core-shell structure nanoparticle, using Cu as the core material in a diameter of 90 nm coated with 5 nm thickness graphene, exhibited a better photothermal property under the solar radiation. In the second case regarding atmospheric soot, the established model provided an efficient method for understandings on the optical properties and warming effects of realistic soot particles. It was found that the sizes and material characteristics of soot, would greatly affect their scattering and absorption of light. Moreover, two submodels were introduced and integrated, which can better predict behaviors of real atmospheric soot involving their core-shell structures (moisture or organic condensates) and their fractal agglomerate structures. In conclusion, the established model helps to understand the interaction between nanoparticles and electromagnetic waves, which shows great potentials of wide applications.