Characterization of design and economic sensitivity of vapor phase carbon adsorption systems to environmental uncertainties

Vapor phase carbon adsorption systems are used to remove aromatics, aliphatics, and halogenated hydrocarbons. The adsorption capacity of granular activated carbon is reduced when environmental parameters (temperature, pressure, and humidity) interfere with homogeneous surface diffusion and pore distribution dynamics. The purpose of this study was to investigate the effects of parametric uncertainties in adsorption efficiency. ^ Modified versions of the Langmuir isotherm in conjunction with thermodynamic equations described gaseous adsorption of single component influent onto microporous media. Experimental test results derived from Wang et al. (1999) simulated adsorption kinetics while the Myer and monsoon Langmuir constant accounted for isothermal gas compression and energetic heterogeneity under thermodynamic equilibrium conditions. Responsiveness of adsorption capacity to environmental uncertainties was analyzed by statistical sensitivity and modeled by breakthrough curves. Results indicated that extensive fluctuations in adsorption capacity significantly reduced carbon consumption while isothermal variations had a pronounced effect on saturation capacity. ^

Development, validation and uncertainty analysis of quantitative structure and activity relationship models for Log P of disinfection by -products

Hydrophobicity as measured by Log P is an important molecular property related to toxicity and carcinogenicity. With increasing public health concerns for the effects of Disinfection By-Products (DBPs), there are considerable benefits in developing Quantitative Structure and Activity Relationship (QSAR) models capable of accurately predicting Log P. In this research, Log P values of 173 DBP compounds in 6 functional classes were used to develop QSAR models, by applying 3 molecular descriptors, namely, Energy of the Lowest Unoccupied Molecular Orbital (ELUMO), Number of Chlorine (NCl) and Number of Carbon (NC) by Multiple Linear Regression (MLR) analysis. The QSAR models developed were validated based on the Organization for Economic Co-operation and Development (OECD) principles. The model Applicability Domain (AD) and mechanistic interpretation were explored. Considering the very complex nature of DBPs, the established QSAR models performed very well with respect to goodness-of-fit, robustness and predictability. The predicted values of Log P of DBPs by the QSAR models were found to be significant with a correlation coefficient R2 from 81% to 98%. The Leverage Approach by Williams Plot was applied to detect and remove outliers, consequently increasing R 2 by approximately 2% to 13% for different DBP classes. The developed QSAR models were statistically validated for their predictive power by the Leave-One-Out (LOO) and Leave-Many-Out (LMO) cross validation methods. Finally, Monte Carlo simulation was used to assess the variations and inherent uncertainties in the QSAR models of Log P and determine the most influential parameters in connection with Log P prediction. The developed QSAR models in this dissertation will have a broad applicability domain because the research data set covered six out of eight common DBP classes, including halogenated alkane, halogenated alkene, halogenated aromatic, halogenated aldehyde, halogenated ketone, and halogenated carboxylic acid, which have been brought to the attention of regulatory agencies in recent years. Furthermore, the QSAR models are suitable to be used for prediction of similar DBP compounds within the same applicability domain. The selection and integration of various methodologies developed in this research may also benefit future research in similar fields.

Mineralogy of northern Indian Ocean surface sediments and of suspended sediments of Indian rivers (Table 2 and 5)

The solid phases from surface sediments, atmospheric dusts, and rivers of the Indian Ocean environment have been analyzed for their clay minerals and quartz. Such data have been used to delimit the transport paths and sources of the detrital minerals in the oceanic deposits. Diagnostic in distinguishing fluvial and eolian inputs to the northern Indian Ocean is a combination of the clay mineral assemblages and of their geographic distributions. River borne solids are the primary components of the Bay of Bengal deposits. The eastern part receives its continental input through the Ganges-Brahmaputra river system, while drainage of the Indian Peninsula by rivers introduces solids to the western part. The former materials are characterized by high illite and chlorite in the clay mineral assemblages; the latter by montmorillonite. The winds over the Bay bear distinctive dust burdens based upon their directions. However, their contributions to the sediments are insignificant. The eastern sector of the Arabian Sea receives major contributions of continental debris from the rivers and the high montmorillonite levels clearly indicate a source in the Indian Peninsula. The rest of the Sea appears to receive most of its land-derived materials from the north, perhaps the desert regions of northern India and West Pakistan, and they are wind-borne. These materials are also transported to the equatorial regions of the Indian Ocean. A gradient in attapulgite, just north of the equator, may indicate an eolian contribution to the Arabian Sea from the African continent. The halogenated hydrocarbon pesticides were assayed in the southwest monsoon winds and enter the Bay of Bengal at levels of a half ton per month, an amount comparable to those introduced by other wind and river systems to the marine environment.

Biogenic halocarbons from the Peruvian upwelling region during METEOR cruise M91

Halocarbons, halogenated short-chained hydrocarbons, are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling obtained during the M91 cruise onboard the research vessel Meteor in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group as likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L-1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L-1 and diiodomethane (CH2I2) of up to 32.4 pmol L-1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. The enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels.

A importância do uso de métodos complementares para a avaliação da toxicidade de hidrocarbonetos aromáticos policíclicos

Hidrocarbonetos Aromáticos Policíclicos (HAPs) e seus derivados Halogenados (HHAPs) são conhecidos como um conjunto de contaminantes ambientais, classificados como potencialmente tóxicos, mutagénicos e carcinogénicos, sendo um assunto de extrema importância e preocupação para a saúde pública. Diversos estudos têm reportado o potencial efeito tóxico destes compostos após longos períodos de exposição, pelo uso de métodos colorimétricos como o ensaio de brometo de 3-[4,5- dimetil-tiazol-2-il]-2,5-difeniltetrazólio (MTT) e vermelho neutro. Contudo, apesar de estes métodos clássicos de avaliação da citotoxicidade in vitro permitirem, de forma rápida, identificar as propriedades nocivas dos compostos, não permitem compreender os mecanismos moleculares subjacentes responsáveis pela sua toxicidade. Deste modo, no presente estudo, para avaliar os efeitos à exposição aos compostos Pireno (Pir) e seu derivado resultante da desinfeção de águas por bromação, 1-BromoPireno (1-BrPir), foram utilizados outros métodos complementares como avaliação do stress oxidativo e vários fenómenos associados à morte celular programada. Os resultados obtidos comprovam não só a existência de efeitos citotóxicos dos poluentes quando acumulados, como também possíveis efeitos genotóxicos. Assim, pelos métodos complementares, foi possível a identificação de alvos moleculares passiveis de ação farmacológica, o que pode constituir o primeiro passo para o desenho de estratégias terapêuticas que visem prevenir ou tratar os danos provocados por estes poluentes no Homem.

Bis(arylene-ethynylene)-s-tetrazines: A Promising Family of n-Type Organic Semiconductors?

We theoretically describe in this work the n-type semiconducting behavior of a set of bis(arylene-ethynylene)-s-tetrazines ((ArCC)2Tz), by comparing their electronic properties with those of their parent diaryl-s-tetrazines (Ar2Tz) after the introduction of ethynylene bridges. The significantly reduced internal reorganization energy for electron transfer is ascribed to an extended delocalization of the LUMO for (ArCC)2Tz as opposite to that for Ar2Tz, which was described mostly localized on the s-tetrazine ring. The largest electronic coupling and the corresponding electron transfer rates found for bis(phenyl-ethynylene)-s-tetrazine, as well as for some halogenated derivatives, are comparable to those reported for the best performing n-type organic semiconductor materials such as diimides and perylenes. The theoretical mobilities for the studied compounds turn out to be in the range 0.3–1.3 cm2 V–1 s–1, close to values experimentally determined for common n-type organic semiconductors used in real devices. In addition, ohmic contacts can be expected when these compounds are coupled to metallic cathodes such as Na, Ca, and Sm. For these reasons, the future application of semiconducting bis(phenyl-ethynylene)-s-tetrazine and its fluorinated and brominated derivatives in optoelectronic devices is envisioned.

Fotodegradação de pesticidas: caso do fenarimol

Tese dout. em Química, Unidade de Ciências Exactas e Humanas, Univ. do Algarve, 1997

Ação de anestésicos gerais em canais iônicos

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Biologia Molecular, 2016.