Made available in DSpace on 2015-04-22T22:01:57Z (GMT). No. of bitstreams: 1 Wamber Boni de Souza.pdf: 2659314 bytes, checksum: 7f9a2f165e36496d3cc87db36897ea3e (MD5) Previous issue date: 2013-06-03 / Fundação de Amparo à Pesquisa do Estado do Amazonas / This work describes the mercury and a summary on toxicity of organomercury, as well as environmental importance of the HS, addressing structural aspects of the interaction between carboxylic groups from humic and fulvic acids and Hg, in two reviews. A third review is presented the Density Functional Theory (DFT) applied to theoretical study of mercury and its compounds. Environmental chemistry of Hg is extensively revised, especially the reduction process Hg2+  Hg+  Hg0. The Hg can also be found in forms organomercury, which the methylmercury (methyl-Hg, CH3Hg+) and dimethylmercury (dimethyl-Hg, CH3(Hg)2) are the most important. Structurally, the difference between the two forms of Hg is the number of methyl groups. Important tool in the consolidation of experimental data, theoretical calculations have proven that they are capable of complementing experimental results. The DFT B3LYP functional with LANL2DZ basis set are performed for the neutral structures dimethylmercury (Dimetil-Hg), methylmercury (MetHgCl), methylmercury bromide (MetHgBr), methylmercury iodide (MetHgI) and charged methylmercury (Met-Hg), methylmercury oxide ion (MetHgO-), methylmercury sulfide ion (METHgS-), methylmercury selenide ion (MetHgSe-). Additionally, the interaction of the Model of Humic Substance Molecules (MHSM) (Benzoic acid (AB), Phthalic acid (AFT), Salicylic acid (AS) e 2,4-dihydroxybenzoic acid (2,4-ADHBC) and carboxylic groups from fulvic acid (AFRS) structure proposed for the Suwannee River with Hg2+ has been investigated theoretically by using DFT method with high level B3LYP/ LANL2DZ model in order to contribute to the understanding of the behavior of Hg in nature. Findings show that the structure of methyl-Hg is more stable and less reactive than dimethyl-Hg. The bond lengths C-Hg on Met-Hg-X (X = Cl-, Br- and I-) increase with increasing volume. In the case of Met-Hg-X (X = O2-, S2- and Se2-), the bond length C-Hg remains virtually unchanged. The charge distribution analysis has revealed that the Hg oxidation tendency to reduce or anion depending on what is on. The trend of reduction/oxidation is accompanied by a greater stabilization energy (NBO) and ΔEL. The HUMO-LUMO orbital shows the structures Met-Hg-X (X = Cl-, Br- and I-) that has a larger Δε Met-Hg-X (X = O2-, S2- and Se2-). Finally, the use of B3LYP/LANL2DZ shows errors in bond length in relation to the experimental data varying between 4.74 and 6.43%. The results showed that the interaction between the carboxylic acid and Hg2+ ions indicate the occurrence of a reduction process rather than complexation in the MMSH. The interaction AB Hg ions formed with the carboxylic AB proved to be the most stable among all the MMSH-Hg. The highest values of stabilization energy of second order were observed by the molecules AB Hg e AFT Hg. Findings showed that the complexation and reduction depends on the location of the carboxyl groups in the structure of fulvic acid in the AFRS. Furthermore, the binding energy, geometry and energy gap is altered by interaction with the carboxylic groups of AFRS with Hg2+. / Esta tese descreve o mercúrio e um resumo sobre a toxicidade dos compostos organomercuriais, bem como a importância ambiental da SH, abordando aspectos estruturais da interação entre grupos carboxílicos dos ácidos húmicos e fúlvicos e Hg, em duas revisões. A terceira revisão é apresentada a Teoria do Funcional da Densidade (DFT) aplicada ao estudo teórico de mercúrio e seus compostos. A química ambiental do Hg é revista extensivamente, especialmente o processo de redução do Hg2+  Hg+  Hg0. O Hg pode ser encontrado também em formas organomercurais, das quais o metilmercúrio (metil-Hg, CH3Hg+) e dimetil-Hg (dimetil-Hg CH3(Hg)2) são as mais importantes. Estruturalmente a diferença entre as duas formas de Hg é a quantidade de grupos metilas. Ferramenta importante na consolidação de dados experimentais, os cálculos teóricos já comprovaram que são capazes de complementar resultados experimentais. A DFT e o funcional B3LYP com o conjunto de base LANL2DZ foram usados para a otimizações de geometria para as estruturas neutras dimetilmercúrio (Dimetil-Hg), cloreto de metilmercúrio (MetHgCl), brometo de metilmercúrio (MetHgBr), Iodeto de metilmercúrio (MetHgI) e carregadas metilmercúrio (Met-Hg), íon óxido de metilmercúrio(MetHgO-), íon sulfeto de metilmercúrio (METHgS-) e íon seleneto de metilmercúrio (MetHgSe-). Além disso, a interação dos grupos carboxílicos de moléculas modelos de substâncias húmicas (MMSH), (Ácido benzoico (AB), Ácido ftálico (AFT), ácido salicílico (AS) e ácido 2,4-diidroxibenzocarboxílico) e de ácido fúlvico (AFRS) de estrutura proposta do rio Suwannee com Hg2+ foi investigado teoricamente por DFT no nível de cálculos B3LYP/LANL2DZ, a fim de contribuir para o entendimento do comportamento do mercúrio na natureza. Os resultados mostram que a estrutura do metil-Hg é mais reativa e menos estável que a estrutura do dimetil-Hg. Os comprimentos de ligação C Hg no Met-Hg-X (X = Cl-, Br- e I-) aumentam com o aumento do volume. No caso do Met-Hg-X- (X = O2-, S2- e Se2-) o comprimento de ligação C Hg permanece praticamente inalterado. A análise de distribuição de carga revelou que o Hg apresenta tendência para redução ou oxidação dependendo do ânion que está ligado. A tendência de redução/oxidação é acompanhada por uma maior energia de estabilização (NBO) e ΔEL. Os orbitais HOMO-LUMO mostram que as estruturas Met-Hg-X (X = Cl-, Br- e I-) possuem maior Δε que Met-Hg-X- (X = O2-, S2- e Se2- ). Finalmente o uso do B3LYP/LANL2DZ apresentou erros nos comprimento de ligação em relação aos dados experimentais variando entre 4,74 e 6,43%. Para as MMSH os resultados mostraram de modo geral, que a interação entre os íons carboxílicos e Hg2+ indicam a ocorrência de um processo de redução ao invés de complexação. Entre todas as MMSH-Hg, a interação AB Hg formada com os íons carboxílicos da AB mostrou ser a mais estável. As moléculas AB Hg e AFT Hg possuem os maiores valores de energia de estabilização de segunda ordem. Especificamente para os AFRS, os resultados indicam que a complexação e redução dependem da localização dos grupos carboxílicos na estrutura de ácido fúlvico. Além disso, a energia de ligação, a geometria

Chemical components in wood contain multiple anionic groups, including carboxyl groups and hydroxyl groups. During kraft cooking and bleaching, such structures are also formed, degraded or modified by the action of reactions both deliberate and unwanted. It has previously been found by Laine that anionic groups with pKa values of 3.3 and 5.5 can explain the observed anionic charge on chemical fibres, corresponding to carboxylic acids on hemicelluloses as well as oxidized lignin structures, respectively. It has further been found that most of the fibre charge can be accounted for through the contribution from methylglucuronic acids as well as hexenuronic acids. This study aimed to provide additional information regarding the charge component unaffiliated with either of the aforementioned uronic acids by studying kraft pulps procured from an industrial kraft mill corresponding to unit operations through a fibreline using the ODHot(EOP)D1D2 bleaching sequence. Each sample had its total charge determined by means of conductometric titration, its content of methylglucuronic acid determined by means of methanolysis followed by GC, and its content of hexenuronic acids determined by means of the HUT-method for the determination of hexenuronic acids, followed by either UV absorbance measurements or calculations based on the reduction in kappa number during the selective acid hydrolysis. The lignin content was determined by means of kappa number analysis as well as by calculations based on the kappa number after selective acid hydrolysis, which was assumed to be characteristic of the kappa number addition from the lignin content of the samples. The hexenuronic acid content was successfully determined according to the HUT-method. A difference in content was observed when results for the unbleached and oxygen delignified samples that was obtained from UV measurements were compared with the observed difference in kappa number prior and after selective acid hydrolysis for said samples. In both cases, the results based on the difference in kappa number was higher. No correlation between remaining charge and lignin content could be made. It was instead observed that individual bleaching steps had binary effects on each of the analysed components of the fibre charge. A significant increase in charge unaffiliated with methylglucuronic acid or hexenuronic acid was observed during the EOP step, indicating an oxidation of chemical structures in the pulp: this effect could not be correlated to lignin content. / Kemisk massa kan ses som ett kompositmaterial bestående av cellulosa, hemicellulosa och lignin. Dessa beståndsdelar, liksom separata lågmolekylära föreningar, innehåller anjoniska kemiska grupper som bidrar till att ge träfibrer en anjonisk laddning. Ytterligare sådana grupper kan bildas under reaktioner vid kokning och blekning, tillika kan sådana grupper modifieras eller brytas ner. Laine har tidigare visat att fiberladdningen kan förklaras genom två skilda kategorier av kemiska grupper med pKa värden på 3,3 samt 5,5, vilka kan kopplas till karboxylsyragrupper på hemicellulosor respektive till lignin. Man har därtill funnit att stora delar av fiberladdningen kan förklaras genom tillskott från de två uronsyrorna metylglukuronsyra och hexenuronsyra. Denna studie syftar till att undersöka det laddningstillskott som inte kan länkas till någon av dessa två uronsyror. Detta har gjorts genom att studera kemiska massor från industrin, tagna från de olika stegen i en bleksekvens av typen ODHot(EOP)D1D2. Massornas totalladdning mättes medelst konduktometrisk titrering, emedan metylglukuronsyrahalten mättes via methanolysis följt av GC och hexenuronsyrahalten mättes via selektiv syrahydrolys per HUT-metoden följt av UV-karakterisering respektive beräkningar baserade på differensen i kappa tal före och efter sagda hydrolys. Ligninhalten i samtliga prov mättes via kappatalsmätningar samt genom beräkningar baserade på kappatalet efter selektiv syrahydrolys, vilket anses vara kappatalsbidraget från ligninföreningarna. Hexenuronsyrahalterna uppmätta medelst UV-karakterisering respektive kappatalsdifferens jämfördes mot varandra och fanns ge olika resultat för de oblekta och syrgasdelignifierade massorna. I bägge fallen gav mätningen baserade på kappatalsdifferens högre utslag. Ingen korrelation mellan kvarvarande laddning - totalladdning minus tillskottet från uronsyrorna - och ligninhalt kunde observeras. Istället observerades binära effekter för varje uppmätt komponent under vardera blekningssteg. Under EOP-steget observerades ett tillskott till den kvarvarande laddningen, vilket skulle kunna förklaras genom oxidation av trästrukturer. Dock kan ej heller detta relateras till ligninhalten i proverna.