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Cellulose derivatives have been synthesized and used in various applications with emphasis on possible application in environmental remediation. In this context, the present work theoretically studied the adsorption of Cr 3+ , Cu 2+ and Cd 2+ metal ions in the carboxymethylcellulose (CMC) and cellulose xanthate (CX) matrices, both derived from cellulose. From the calculations, it was possible to obtain map of electrostatic potential, frontier molecular orbitals, reactivity indices, and with these, analyses infer that the cations would interact with the CMC and CX oxygen and also with the CX sulfo group. After complexation, the results showed that the CX and CMC matrices studied have potential to be used to remove toxic metals and presented chemical adsorption and the processes occur spontaneously (ΔG < 0). The topological analysis of quantum theory of atoms in molecules allowed to characterize the nature of the interaction, in which the interactions in position "b" of CMC-Cu 2+ , CMC-Cd 2+ and position "a" of CMC-Cd 2+ and "a" in the complexes XC-Cu 2+ , XC-Cd 2+ and "b" in the XC-Cr 3+ site (1) presented electrostatic characteristics, and the other interactions were partially covalent. The results found when compared to the study of cellulose and cellulose acetate adsorption with the same metal ions showed that the theoretical data provide insights for a possible experimental approach and use of this matrices.

O presente trabalho compara o desempenho de dois coagulantes, o sulfato de alumínio ferroso (SAF) e o policloreto de alumínio (PAC) na remoção de turbidez para o tratamento de água para abastecimento público, utilizando como estudo de caso a represa Bananal que abastece o Município de Gurupi, TO. Para os estudos referentes aos processos de coagulação, floculação, sedimentação foram realizados ensaios em equipamento de bancada Jar test, o processo de filtração foi avaliado em filtro em escala de bancada utilizando areia própria para filtro de ETA. Para avaliar a eficiência do sistema foram testadas: diferentes dosagens dos coagulantes em distintas faixas de pH, a velocidade de sedimentação e a taxa de filtração. O coagulante PAC, na dosagem de 12mg.L-1, apresentou melhor desempenho na remoção de cor aparente e turbidez, com a menor concentração de ferro total e alumínio total residual. A dosagem de 15mg.L-1 do coagulante SAF demonstrou um desempenho inferior, no entanto, ambos apresentaram resultados dentro dos limites estabelecidos pela Portaria MS nº 2.914/2011. O estudo de custos indicou que economicamente a utilização do SAF é mais viável, logo que ambos os coagulantes não necessitaram de adição de alcalinizante no processo devido as características da água avaliada.

The presence of internal rotation in sigma bonds is essential for conformational analysis of organic molecules and its understanding is of great relevance in chemistry, as well as in several other areas. However, for aromatic compounds that have substituent groups, withdrawers or donors of electron, there are no data in the literature to explain their rotational barriers. In this context, the work studied the internal rotational barriers of electron donating and withdrawing groups in aromatic compounds using the MP3, MP4, and CCSD(T) methods and the influence of substituents' nature on barrier heights was investigated through calculations based on the theory of Natural Bond Orbitals (NBO) and Quantum Theory of Atoms in Molecules (QTAIM). The results obtained showed that the CCSD(T) method is the one that best describes the internal rotational barriers, followed by MP4 and MP3 and the electron donating groups decrease the barrier, whereas electron withdrawing groups increase. Through the NBO analysis it was possible to observe that for withdrawing groups the interaction of the molecular orbitals is more accentuated promoting the increase of the rotational barrier of these compounds. Through the QTAIM analysis it was possible to show that, for electron donating groups, the internal rotation is influenced by the loss of electronic density when the substituents is perpendicular to the ring plane, however, for withdrawing groups the density is little influenced, regardless of the two conformations (minimum and maximum energy). Two molecules showed free rotation, trichloromethylbenzene and methylbenzene, and the theoretical calculations NBO and QTAIM showed that for these species there is no difference in the properties studied when there is rotation of the dihedral angle.

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