Avaliação físico-química de efluente gerado em biodigestor anaeróbio para fins de avaliação de eficiência e aplicação como fertilizante agrícola

The use of biodigester for basic and environmental sanitation has large demand in Brazil. A biodigester was built to treat conjunctly the human and pig feces and urine, regarding to its future application in rural small towns. The results show that the biodigester can reduce 90% of COD and BOD and, up to 99.99% of thermotolerant coliforms. The treated effluent has variable quantities of macro- and micro-nutrients; and organic matter. However, the concentration variability of the nutrients makes difficult a dosed application into soil. The soluble salts (mainly as Na+ form) make necessary a controlled use to avoid environmental degradation.

Investigando a presença da história da ciência em livros didáticos de Química Geral para o ensino superior

This paper aims at analyzing the history of science content of three general chemistry textbooks used in Brazilian universities: the translations of Kotz and Treichel's Chemistry & Chemical Reactivity, Atkins and Jones's Chemical Principles, and Garritz and Chamizo's Química. Results revealed different trends for the inclusion of history of science in chemistry teaching. Kotz & Treichel and Atkins & Jones used history mainly as curiosity and ornament. Garritz & Chamizo adopted the historical approach as one of the organizing axis of their textbook. Nevertheless, the historical content of the three textbooks may be criticized from current historiographical standpoint.

O trabalho experimental no ensino de Química

This article deals with conceptions of the experimental work in the Chemistry teaching, developed among teachers and students. The research was carried out using qualitative methodology, based on Gaston Bachelard's thoughts. The results showed dispersion of conceptions among both students and teachers. This dispersion, interpreted as a profile of conceptions, was discussed based on the notions of Bachelard's epistemological profile and Mortimer's conceptual profile. This work points out the need to rethinking and finding new directions for experimental activities in the training courses for Chemistry teachers, in order to meet Chemistry educators' social goals.

Composição química e avaliação da atividade antimicrobiana do óleo essencial das folhas de Piper malacophyllum (C. Presl.) C. DC.

This work reports the chemical composition as well as the antibacterial, antifungal and antiparasitic activities of the leaf essential oil from Piper malacophyllum. The oil was extracted by hydrodistillation and analyzed by GC-FID, GC-MS and polarimetry. Among the 28 compounds identified, (+)-camphor was the major constituent. The essential oil showed activity against most of the microorganisms tested, especially antifungal action, with a MIC of 500 µg mL-1 against Trichophyton mentagrophytes and Cryptococcus neoformans. This is the first study reporting the composition and biological properties of leaf essential oil from P. malacophyllum.

Caracterização físico-química de filmes comestíveis de amido adicionado de acerola (Malphigia emarginata D.C.)

Edibles films are an alternative to synthetic materials used for packing food products. Barbados cherry is rich in vitamin C and carotenoids. The aim of this study was to characterize and develop films by casting from cassava starch, lyophilized Barbados cherry pulp and glycerol. The films were characterized with respect to thickness, water vapor permeability (WVP), water solubility, vitamin C, carotene and mechanical properties. The interaction of pulp and glycerol reduced film thickness. An increase in pulp concentration up to 60% increased WVP but beyond this concentration reduced both WVP and solubility leading to an increased level of vitamin C and β carotene in the films.

Biomassa em aula prática de Química Orgânica Verde: cravo-da-índia como fonte simultânea de óleo essencial e de furfural

This work presents an optimized integrated experiment for isolation of clove bud essential oil, rich in eugenol, and subsequent utilization of the solid residue for furfural synthesis. The operationally simple laboratory protocols and utilization of water as a solvent in both operations, plus the use of biomass as the starting material for preparation of versatile intermediates in organic synthesis, make the experiments attractive for undergraduate experimental organic chemistry courses in the context of green chemistry. In addition, this is the first description of the use of biomass (clove bud) in the simultaneous preparation of two chemical feedstocks, eugenol and furfural, on experimental organic chemistry courses.

Condensação de Knoevenagel de aldeídos aromáticos com o ácido de Meldrum em água: uma aula experimental de Química Orgânica Verde

This work describes an undergraduate experiment for the synthesis of Knoevenagel adduct of Meldrum's acid with nine aromatic aldehydes, using water as the solvent, in an adaptation of a previously reported synthetic protocol. The synthesis was straightforward, requiring a period of two hours, and is suitable for undergraduate experimental courses on green chemistry. In addition, quantitative analyses of the relative reactivity of p-nitro-benzaldehyde and p-metoxi-benzaldehyde was evaluated through the competitive reaction of equimolar amounts of these aldehydes with one equivalent of Meldrum's acid, using gas chromatography to quantify the composition of the reaction mixture.

Redes de colaboração científica na área de química no Brasil: um estudo baseado nas coautorias dos artigos da revista Química Nova

In this paper we built three co-authorship networks displaying the acquaintances between countries, universities and authors that have published papers in Quimica Nova from 1995 to 2008. Our research was conducted applying a bibliometric approach to 1782 papers and over 4200 authors. Centrality measures were used and the most significant actors of each network were pointed out. The results using the centrality metrics and the network structures indicated that Quimica Nova resembles a typical scientific community.

Caracterização química dos géis produzidos pelas bactérias diazotróficas Rhizobium tropici e Mesorhizobium sp.

The exopolysaccharides with characteristics of gel produced by Rhizobium tropici (EPS RT) and Mesorhizobium sp (EPS MR) are acidic heteropolysaccharide composed mainly of glucose and galactose in a molar ratio of 4:1 and 5:1 respectively, with traces of mannose (~ 1%). Chemical analysis showed the presence of uronic acid, pyruvate and acetyl-substituents in the structures of both polymers. Experiments of gel permeation chromatography and polyacrylamide gel electrophoresis showed that EPS RT and EPS MR are homogeneous molecules with low grade of polydispersity. The EPS were characterized using spectroscopic techniques of FT-IR, ¹H and 13C-NMR.

Influência da secagem sobre o rendimento e composição química dos compostos voláteis das raízes de Piper piscatorum Trel. & Yunck. (Piperaceae)

In this study, we evaluated the yield and chemical composition of volatile compounds obtained from fresh, dried at 30 and 40 ºC respectively of Piper piscatorum, employing the technique of hydrodistillation. The volatile were chemically characterized by GC-MS and GC-FID. The main volatile compounds were selin-11-en-4-a-ol (57,63 ± 3,07%; 53,95 ± 1,56% and 56,20 ± 0,43%) and benzyl benzoate (15,40 ± 0,36%; 16,32 ± 0,85% and 15,04 ± 0,24%).The drying of the raw material reduced yield of volatile compounds, changing their chemical compositions.

A problematização das atividades experimentais na educação superior em Química: uma pesquisa com produções textuais docentes - parte II

Through the analysis of articles with proposals for experimental activities and with current pedagogical, epistemological and environmental discussion on experimentation by Chemistry professors, this paper investigates ways of highlighting relevant methodological characteristics that can be incorporated in experiments. 102 articles from national periodicals were analysed, all of which suggested experiments for use in Chemistry higher education. Based on analysis of the suggestions for experiments it appears that of particular importance are: visions, such as those that explain a belief that experimentation incentivizes motivation and conceptual learning; awareness of observation influenced by empiricism; and "errors" of students, which enrich their knowledge.

Diferentes olhares acerca dos conhecimentos necessários na formação inicial do professor de Química

This study investigated different understandings about the educational needs of a professor of Chemistry, related to "know" and "know-how". It was verified the convergence and divergence of perceptions of high school students from that point to literature and education legislation. The research was conducted in five states in northern Brazil. The results show the little dialogue between training institutions and secondary schools, since the different understandings about the training needs go in opposite directions.

A retórica da linguagem científica: das bases teóricas à elaboração de material didático para o ensino superior de Química

This work is part of a study that focused on analyzing the contributions of didactic activities related to scientific language rhetoric characteristics aimed at developing students' abilities to identify such characteristics in chemistry scientific texts and critical reading of those texts. In this study, we present the theoretical basis adopted to determine the scientific discourse characteristics and for the production of the didactic material used in those activities. Latour, Coracini and Campanario studies on persuasive rhetorical strategies present in scientific articles aided the production of such material.

Furfural - da biomassa ao laboratório de química orgânica

The goal of this manuscript is provide to students of Chemistry and related areas an alternative experiment in which they can obtain a compound and learn to observe and interpret properties and predict organic structure by obtaining furfural from biomass. Furfural is an organic compound, obtained through acid hydrolysis of pentosans, commonly used in the chemical and pharmaceutical industries. Students are guided to get furfural through extractive procedures and chemical reactions adapted to semi-micro laboratory scale. Characterization of furfural was done by chemical tests and physical properties. Identification was accomplished by a series of spectroscopic and spectrometric techniques.