ABSTRACT The adsorption of Violet Remazol 5R (VR 5) on wood sawdust modified with succinic anhydride (SSA) as a function of contact time, pH, and initial dye concentrations was investigated using a batch technique under ambient conditions. The SSA obtained was confirmed by IR spectroscopy, thermogravimetry and 13C NMR, and degrees of substitution (DS) were calculated. A study on the effect of the pH on the adsorption of VR 5 showed that the optimum pH was 2.0. The interactions were assayed with respect to the pseudo-first-order and pseudo-second-order kinetic models, and were found to follow closely the pseudo-second-order. The isotherm was adjusted to the Langmuir, the Freundlich and the Temkin sorption models. SSA is a promising material for the removal of dye textile from aqueous solutions, and under conditions studied the removal percentage achieved was 51.7%.

Cellulose was first modified with thionyl chloride, followed by reaction with 2-aminomethylpyridine to yield 6-(2'-aminomethylpyridine)-6-deoxycellulose. The resulting chemically-immobilized surface was characterized by elemental analysis, FTIR, 13C NMR and thermogravimetry. From 0.28% of nitrogen incorporated in the polysaccharide backbone, the amount of 0.10 ± 0.01 mmol of the proposed molecule was anchored per gram of the chemically modified cellulose. The available basic nitrogen centers attached to the covalent pendant chain bonded to the biopolymer skeleton were investigated for copper, cobalt, nickel and zinc adsorption from aqueous solution at room temperature. The newly synthesized biopolymer gave maximum sorption capacities of 0.100 ± 0.012, 0.093 ± 0.021, 0.074 ± 0.011 and 0.071 ± 0.019 mmol.g-1 for copper, cobalt, nickel and zinc cations, respectively, using the batchwise method, whose data was fitted to different sorption models, the best fit being obtained with the Langmuir model. The results suggested the use of this anchored biopolymer for cation removal from the environment.

A atividade enzimática é uma propriedade importante para avaliação da qualidade do solo. Duas sequências de experimentos foram realizadas com o objetivo de avaliar a atividade enzimática em amostras de solo (Latossolo Vermelho eutroférrico típico), tratadas com esterco bovino, húmus de minhoca ou lodos de esgoto dos municípios de Barueri e Franca. A atividade de enzimas comerciais nas mesmas amostras de solo, após serem esterilizadas, foi medida por microcalorimetria. No primeiro experimento, a atividade das enzimas celulase, protease e urease foi determinada em amostras de solo durante um período de três meses. Na segunda sequência de experimentos, o efeito térmico das enzimas comerciais celulase, protease e urease em amostras de solo, esterilizadas sob os mesmos tratamentos, foi monitorado por um período de 46 dias. O delineamento experimental foi inteiramente casualizado, em esquema fatorial cinco tratamentos x sete amostragens, com cinco repetições. O efeito dos tratamentos foi avaliado estatisticamente pela análise de variância. O teste de Tukey foi usado para comparar médias a p < 0,05. A presença de diferentes fontes de materiais orgânicos aumentou a atividade enzimática durante o período de amostragem. O esterco bovino propiciou os maiores valores, seguido pelos lodos de esgoto. O húmus de minhoca ocasionou os valores mais baixos, mas que diferiram significativamente do tratamento controle. O efeito térmico para a atividade das enzimas comerciais celulase, protease e urease mostrou uma variedade de picos ao longo do tempo. Esses valores oscilaram provavelmente devido aos fatores físico-químicos do solo, alterando a atividade enzimática nos resíduos.

Enzymatic activity is an important property for soil quality evaluation. Two sequences of experiments were carried out in order to evaluate the enzymatic activity in a soil (Rhodic Eutrudox) amended with cattle manure, earthworm casts, or sewage sludges from the municipalities of Barueri and Franca. The activity of commercial enzymes was measured by microcalorimetry in the same soil samples after sterilization. In the first experiment, the enzyme activities of cellulase, protease, and urease were determined in the soil samples during a three month period. In the second sequence of experiments, the thermal effect of the commercial enzymes cellulase, protease, and urease on sterilized soil samples under the same tretaments was monitored for a period of 46 days. The experimental design was randomized and arranged as factorial scheme in five treatments x seven samplings with five replications. The treatment effects were statistically evaluated by one-way analysis of variance. Tukey´s test was used to compare means at p < 0.05. The presence of different sources of organic residues increased the enzymatic activity in the sampling period. Cattle manure induced the highest enzymatic activity, followed by municipal sewage sludge, whereas earthworm casts induced the lowest activity, but differed from control treatment. The thermal effect on the enzyme activity of commercial cellulase, protease, and urease showed a variety of time peaks. These values probably oscillated due to soil physical-chemical factors affecting the enzyme activity on the residues.

Os componentes mesocarpo e epicarpo do coco babaçu foram utilizados como novos biossorventes alternativos para remoção do corante têxtil ftalocianina de cobre de soluções aquosas. Esses biopolímeros foram caracterizados por análise elementar, RMN de 13C no estado sólido, espectroscopia de absorção na região do infravermelho, análise termogravimétrica e difratometria de raios X. Os resultados mostraram que a composição do mesocarpo e do epicarpo é similar à de outros materiais lignocelulósicos e que ambos os componentes são efetivos na remoção do corante têxtil Turqueza Remazol. O modelo cinético de pseudo-segunda ordem resultou no melhor coeficiente de correlação tanto para o epicarpo quanto para o mesocarpo (R² = 0,999), com constantes de velocidade de sorção, k2, de 0,31 e 1,43 g mg-1 min-1, respectivamente. Os modelos de Langmuir e Freundlich foram empregados para analisar os dados experimentais em sua forma linearizada. O segundo modelo apresentou melhor adequação para a adsorção do corante Turqueza Remazol com sorção máxima de 1,44 e 2,38 mg g-1 a pH 6,0 para mesocarpo e epicarpo, respectivamente.

The mesocarp and epicarp components of the babassu palm tree were applied as novel alternative biosorbents for copper phtalocyanine textile dye removal from aqueous solutions. The natural biopolymers were characterized by elemental analyses, solid state 13C NMR, infrared spectroscopy, thermogravimetric analysis and X-ray diffractometry. Results demonstrated that the compositions of the mesocarp and epicarp are similar to those of other lignocellulosic materials, and that they were very effective for removal of the textile dye Turquoise Remazol. A pseudo second-order kinetic model resulted in the best fit with experimental data for both epicarp and mesocarp (R² = 0.999), providing rate constants of sorption, k2, of 0.31 and 1.43 g mg-1 min-1, respectively. The Langmuir and Freundlich isotherm models were employed for adsorption analysis of the experimental data in their linearized forms. The second model resulted in the better fit for Turquoise Remazol dye, which presented maximum adsorption of 1.44 and 2.38 mg g-1 at pH 6.0 for mesocarp and epicarp, respectively.

Uma amostra natural de esmectita oriunda do estado do Piauí, Brasil, foi organofuncionalizada com 3-mercaptopropiltrimethoxissilano e 3-aminopropiltriethoxissilano. O espaçamento basal da argila natural é de 0,99 nm e área superficial 48 m² g-1. Houve um aumento no espaçamento basal para 1,84 e 2,01 nm e o aumento da área específica para 781 e 795 m² g-1 para as argilas quimicamente modificadas, respectivamente. A argila natural e a argila quimicamente modificada adsorveram cátions mercúrio em solução aquosa em pH 3,0 e 298 ± 1 K. Os modelos de isotermas de adsorção de Langmuir, Redlich-Peterson e Toth foram aplicados para ajuste dos dados experimentais com aproximação não linear. Para as interações cátion/centros básicos para cada esmectita na interface sólido/líquido foi utilizada metodologia calorimétrica e foram obtidas as constantes de equilíbrio e os efeitos térmicos exotérmicos. Considerando o número interativo de moles para cada cátion e as constantes de equilíbrio, a entalpia, "intHº (-11,98 a -13,93 kJ mol-1) e a energia livre de Gibbs negativa, "intGº (-22,4 ± 0,1 a -23,9 ± 0,1 kJ mol-1) foram calculadas, o que permitiram a determinação da entropia positiva "intSº (51 ± 01 a 55 ± 2 J K-1 mol-1). As interações cátion/centros básicos são de natureza espontânea como demonstram os valores de energia livre de Gibbs, dando o conjunto de dados favoráveis como expressam a entalpia exotérmica e a entropia positiva, mostrando que a esmectita natural e as quimicamente modificadas têm habilidade em complexar mercúrio. Logo, esses materiais são úteis na remoção de mercúrio em um ecossistema.

A natural smectite clay sample from Piauí State, Brazil, was organofunctionalized with 3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane silyating agents. The basal spacing of 0.99 nm and surface area of 48 m² g-1 for natural clay increased to 1.84 and 2.01 nm, and 781 and 795 m² g-1 for modified clays, respectively. The natural and chemically immobilized clay samples adsorb mercury cations from aqueous solutions at pH 3.0 at 298 ± 1 K. The Langmuir, Redlich-Peterson and Toth adsorption isotherm models were applied to fit the experimental data with a nonlinear approach. From the cation/basic center interactions for each smectite at the solid-liquid interface, by using calorimetry methodology, the equilibrium constant and exothermic thermal effects were obtained. By considering the net interactive number of moles for each cation and the equilibrium constant, the enthalpy, "intHº (-11.98 to -13.93 kJ mol-1) and negative free Gibbs energy, "intGº (-22.4 ± 0.1 to -23.9 ± 0.1 kJ mol-1) were calculated. These values enabled the determination of positive entropy, "intSº (51 ± 01 to 55 ± 2 J K-1 mol-1). The cation-basic center interactions are spontaneous in nature as demonstrated from favorable enthalpic and entropic results. Natural and anchored smectites have the ability to complex mercury, acting as useful materials for removal of this hazardous metal from an ecosystem.

Amostras de caulinita e esmectita oriundas da região Amazônica, Brasil, foram modificadas com 2-mercaptobenzimidazol (MBI) usando rotas homogênea e heterogênea. As amostras de argilas modificadas (K HOM, S HOM, K HET e S HET) foram caracterizadas por análise textural, MEV e espectroscopia 13C NMR. As argilas modificadas quimicamente apresentaram modificações em suas propriedades físico-químicas incluindo: área específica 48,0 (S) para 869,8 m² g-1 (S HET). A habilidade destes materiais para remover tório(IV) em soluções aquosas foi investigada por um série de isotermas de adsorção ajustadas pela equação de Sips em temperatura ambiente e pH 2,0. O número máximo de mols adsorvidos foi determinado em 8,29, 8,86, 9,57 e 9,89 10-1 mmol g-1 para K HOM, K HET, S HOM e S HET, respectivamente. Os efeitos energéticos causados pela adsorção do cation tório(IV) foram determinados através de metodologia calorimétrica.

Kaolinite and smectite clay samples from the Amazon region, Brazil, were modified with 2-mercaptobenzimidazole (MBI) using homogeneous and heterogeneous routes. The modified clay samples (K HOM, S HOM, K HET and S HET) were characterized by textural analysis, SEM and 13C NMR spectroscopy. The chemically modified clay samples showed modifications of their physical-chemical properties including: specific area 48.0 (S) to 869.8 m² g-1 (S HET). The ability of these materials to remove thorium(IV) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature, and pH 2.0. The maximum number of moles adsorbed was determined to be 8.29, 8.86, 9.57 and 9.89 10-1 mmol g-1 for K HOM, K HET, S HOM and S HET, respectively. The energetic effects (ΔintH, ΔintG and ΔintS) caused by thorium(IV) cation adsorption were determined through calorimetry.

Amostras brasileiras de caulinita foram usadas no estudo dos processos de intercalação com uréia (K UR) e de deslaminação (K UR/DL). A amostra intercalada foi deslaminada por tratamento com ultra-som em solução ácida. A distância basal inicial de 0,72 nm passa a 1,08 nm com aumento na área superficial de 20,3 para 90,5 m²g-1 para K NAT e K UR/DL. Amostras de argila intercalada e deslaminada adsorveram cátions cobre e chumbo na interface sólido/líquido. Os modelos de isotermas de adsorção de Langmuir, Redlich-Peterson e Toth foram utilizados em processo de regressão linear e não linear para a obtenção de valores de b e K L para todas as amostras de caulinita. A capacidade de adsorção mais alta, de 12,8 mmol g-1, foi obtida com a caulinita deslaminada. Os parâmetros cinéticos analisados pelos modelos de Lagergren e Elovich forneceram um bom ajuste para uma reação de pseudo-segunda ordem com valores de k2 variando de 5,0 a 11,0 e de 4,9 a 13,0 mmol-1 min-1 para cátions cobre e chumbo, respectivamente.

Brazilian kaolinite clay was used to study urea intercalation (K UR) and delamination (Kur/DL) processes. The intercalated sample was delaminated by ultrasonic treatment in acidic solution. The basal distance changed from 0.72 to 1.08 nm with increasing surface area from 20.3 to 90.5 m² g-1 for K UR and K UR/DL. Suspended pristine, intercalated and delaminated clays at pH 5.0 adsorbed copper and lead cations at the solid/liquid interface. The Langmuir, Redlich-Peterson and Toth adsorption isotherm models were employed in linear and nonlinear regression processes, to give b and K L values for all kaolinites. The highest adsorption capacity of 12.8 mmol g-1 was obtained with delaminated kaolinite. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k2 in the 5.0 to 11.0 and the 4.9 to 13.0 mmol-1 min-1 ranges for copper and lead cations, respectively.

The aim of this investigation is to study how Zr/Ti-PILC adsorbs metals. The physico-chemical proprieties of Zr/Ti-PILC have been optimized with pillarization processes and Cu(II), Ni(II) and Co(II) adsorption from aqueous solution has been carried out, with maximum adsorption values of 8.85, 8.30 and 7.78 x10-1 mmol g-1, respectively. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data with a linear regression process. The energetic effect caused by metal interaction was determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant.

This review reports the application of inorganic and organic polymeric materials for cation removal by using nitrogenated basic centers. The data demonstrate the importance of the desired groups when free or immobilized on natural or synthesized inorganic polymers through silanol groups. Thus, the most studied silica gel is followed by natural crysotile and talc polymers, and the synthesized mesopore silicas, talc-like, silicic acids, phosphates and phyllosilicates. The organic natural biopolymeric chitin and cellulose were chemically modified to improve the availability of the amine groups or the reactivity with desirable molecules to enlarge the content of basic centers. The cation removal takes place at the solid/liquid interface and some interactive effects have their thermodynamic data determined.

This report has an objective to contribute the understanding of some historical features associated with the preceding period before SBQ foundation on 8th July of 1977. There are some descriptions involving chemist meetings to decide the strategy of splitting from the Brazilian Society for the Progress of Science (SBPC), in order to be independent on annual meeting organizations. The military political situation forced the annual SBPC meeting transference from Fortaleza to São Paulo, where the chemist assembly took place in PUC and the SBQ was definitively founded. The actual powerful of the Society and its successful in completing the thirty years anniversary is also exalted.

As amostras de solos tropicais brasileiros foram analisadas pelas técnicas térmicas termogravimetria (TG) e calorimetria exploratória diferencial (DSC) em atmosferas de ar sintético ou argônio. Nesse processo foi investigado o solo eutrudox Ródico com vegetação de floresta, queimado ou não em plantação de cana de açúcar, e aquele de fase arenosa com vegetação de cerrado. A partir da fração orgânica do solo, foram extraídos ácidos húmicos que se decompõem similarmente ao produto comercial, de acordo com as etapas: i) água adsorvida, desidratação, descarboxilação e perda de moléculas orgânicas, ii) decomposição da fração termolábil, iii) matéria orgânica macromolecular e iv) resíduos acima de 950 ºC. As curvas de DSC deram correspondentes picos de perda de água perto de 100 ºC e exotérmicos em temperatura maior que 300 ºC, atribuídos à combustão de fração de matéria orgânica termolábil. As curvas TG dos solos são mais complexas que os ácidos húmicos, devido aos componentes inorgânicos, caracterizando os estágios: i) desidratação, ii) matéria orgânica termolábil, iii) domínio orgânico macromolecular, e iv) resíduos de óxidos. Essas decomposições correspondem a três picos endotérmicos em DSC e um exotérmico mostrado em atmosfera de ar sintético, atribuído à combustão da fração orgânica macromolecular na região de 300 ºC. As curvas de DSC dos solos provenientes de plantação de cana de açúcar mostraram picos endotérmicos mais intensos do que aqueles de solo de floresta. Os resultados térmicos demonstram a influência do material orgânico, que é altamente influenciado pelo componente mineral com alto teor de resíduo, pelo uso na atividade da terra e também pelos processos de queimadas.

Brazilian tropical Latosol soil samples were thermally analyzed associating thermogravimetric (TG) and differential scanning calorimetric (DSC) techniques under synthetic air or argon atmospheres. Rhodic eutrudox soils with forest vegetation, from unburnt and burnt cane plantations and that of a sandy phase having cerrado vegetation were investigated. From the organic soil fraction humic acids were extracted that decompose similarly to the commercial product, following the steps: i) adsorbed water, dehydrations, decarboxylations and release of organic molecules, ii) thermolabile decomposition fraction, iii) macromolecular organic matter and iv) residues. The DSC curves gave the corresponding peak for water release near 100 ºC and exothermic peaks at temperatures higher than 300 ºC, attributed to the combustion of thermolabile organic matter. The TG curves for all soil samples are more complex than those of the humic acids due to the inorganic components, being characterized by stages i) dehydration process, ii) thermolabile organic matter, iii) macromolecular organic domain and iv) oxide residues. These steps of decomposition correspond to three endothermic DSC peaks and one exothermic peak clearly shown under a synthetic air atmosphere, being attributed to the combustion of the macromolecular organic fraction near 300 ºC. The DSC curves from burnt and unburnt red Latosol soils from sugar cane cultivation showed more intense endothermic peaks than those of the forest. These thermal results show the influence of both the type and the organic matter contents on curve profiles, which are highly influenced by the soil mineral compositions and land-use activities, as well as the burning processes.

The adsorption capacity of alpha-chitosan and its modified form with succinic anhydride was compared with the traditional adsorbent active carbon by using the dye methylene blue, employed in the textile industry. The isotherms for both biopolymers were classified as SSA systems in the Giles model, more specifically in L class and subgroup 3. The dye concentration in the supernatant in the adsorption assay was determined through electronic spectroscopy. By calorimetric titration thermodynamic data of the interaction between methyene blue and the chemically modified chitosan at the solid/liquid interface were obtained. The enthalpy of the dye/chitosan interaction gave 2.47 ± 0.02 kJ mol-1 with an equilibrium constant of 7350 ± 10 and for the carbon/dye interaction this constant gave 5951 ± 8. The spontaneity of these adsorptions are reflected by the free Gibbs energies of -22.1 ± 0.4 and -21.5 ± 0.2 kJ mol-1, respectively, found for these systems. This new adsorbent derived from a natural polysaccharide is as efficient as activated carbon. However 97% of the bonded dye can be eluted by sodium chloride solution, while this same operation elutes only 42% from carbon. Chitosan is efficient in dye removal with the additional advantage of being cheap, non-toxic, biocompatible and biodegradable.

The present work reviews recent advances in the preparation of new reversed phase packing materials such as sterically protected, bidentate, hybrid organic-inorganic and monolithic phases and phases containing embedded polar groups. The bonding chemistry involved in the preparation of these phases as well as their advantages over conventional C8 and C18 reversed phases are discussed. Understanding the reasons behind the development of these newer column packings helps analysts select the best stationary phase for a given application.

An overview about the role of alkoxides in the most recent uses of the sol-gel process in the synthesis of new materials is presented. Special attention is focused on the uses of silicon, aluminum, zirconium and titanium alkoxides. This review shows that the alkoxides enable the synthesis of new matrices with controlled surface area, acidity and porosity, as well as some unusual properties. The property associated with the solubility of metal alkoxides opens enormous possibilities of combining them for the synthesis films of powders with a very large range of metal compositions.