Ambiental volatile organic compounds in the megacity of São Paulo

In order to characterize the composition of the main urban air organic compounds in the megacity of Sao Paulo, analysis of samples collected during the winter of 2003 downtown was carried out. The samplings were performed on the roof of a building in the commercial center of São Paulo. Hydrocarbons and carbonyls compounds were collected on August 4, 5 and 6. Comparing to previous data, the concentration of hydrocarbons presented no decrease in the concentration, except for the aldehydes, which decreased when compared to previous data. Among the HCs species analyzed, the highest concentrations observed were those of toluene (7.5 ± 3.4 ppbv), n-decane (3.2 ± 2.0 ppbv), benzene (2.7 ± 1.4 ppbv) and 1,3,5-trimethylbenzene (2.2 ± 1.5 ppbv).

Experimento didático sobre cromatografia gasosa: uma abordagem analítica e ambiental

This paper describes an experiment to teach the principles of gas chromatography exploring the boiling points and polarities to explain the elution order of a series of alcohols, benzene and n-propanone, as well as to teach the response factor concept and the internal standard addition method. Retention times and response factors are used for qualitative identification and quantitative analysis of a hypothetical contamination source in a simulated water sample. The internal standard n-propanol is further used for quantification of benzene and n-butanol in the water sample. This experiment has been taught in the instrumental analysis course offered to chemistry and oceanography students.

Degradação fotoeletroquímica de corantes dispersos em efluente têxtil utilizando fotoanodos de Ti/TiO2

The degradation of disperses dyes in aqueous solution and in effluents from textile industry has been investigated by photoelectrocatalytic oxidation using nanoporous thin films electrodes of Ti/TiO2. Samples of dispersil black dye and dispersil blue dye after 300 min of photoelectrolyzed at applied potential of +1.0 V and UV irradiation exhibited 100% of discoloration and 90% and 64% reduction total organic carbon, respectively. The proposed method was applied with success in a textile industry effluent containing residues of these dyes, which after 300 min of treatment leads to reduction of 60% of COD and 64% removal of TOC.

Estudo da degradação de ranitidina via H2O2 eletrogerado/Fenton em um reator eletroquímico com eletrodos de difusão gasosa

The study of the electrochemical degradation of the ranitidine was developed using an electrochemical reactor with a gas diffusion electrode (GDE) as cathode. The electrolysis experiments was performed at constant current (1 < A < 10) and flow rate of 200 L h-1. The process of drug degradation, chemical/electrochemical and electro-Fenton ways, using electrochemical reactor showed best efficiency at current values of > 4 A. The process reached a production of 630 mg L-1 of the H2O2 at 7 A. The ranitidine concentrations was reduced in 99.9% (HPLC) and chemical oxygen demand (COD) was reduced in 86.7% by electro-Fenton.

Degradação de fármacos residuais por processos oxidativos avançados

The concern about aquatic ecosystems and the potential risk of drinking water contamination by pharmaceuticals have stimulated the study of processes for the efficient degradation of these contaminants, since the conventional treatment have been inefficient on that purpose. The advanced oxidation processes (AOPs) appear as viable alternatives due to their efficiency on the degradation of different classes of organic contaminants. This review presents an overview of the main AOP (O3, H2O2/UV, TiO2/UV, Fenton and photo-Fenton) which have been applied to the degradation of different pharmaceuticals. The main results obtained, intermediates identified and toxicity data are presented.

Salir de la escuela: entre la tradición y la educación ambiental para la sostenibilidad = Excursions from school: between tradition and environmental education for sustainability

Las actividades escolares fuera del centro constituyen una marca de calidad del pasado y del presente educativo, y tienen que seguir siéndolo en el futuro. A partir de una investigación cualitativa se identifican las razones aducidas por enseñantes para salir del aula y, con ejemplos concretos, quedan plasmados algunos de los objetivos perseguidos, así como otros que se añaden a la propia actividad. Se identifican salidas vivenciales y otras más experimentales, se reconocen valores positivos, pero también se echa en falta un trabajo más coherente con los principios actuales de la educación ambiental. Precisamente esta educación es la propuesta como el camino a seguir para renovar objetivos, técnicas y procedimientos para salir del aula

Estudo da degradação fotocatalítica de dimetil dissulfeto: avaliação estatistica do efeito do pH da temperatura e concentração do contaminante orgânico

This work aimed to assess the photocatalytic degradation of a model odor compound (dimethyl disulfide, DMDS), found in liquid and gaseous wastes of plants for processing poultry byproducts. The effect of pH and temperature on adsorption and photocatalytic degradation was evaluated through factorial experimental designs. The results suggest the presence of an optimum region for adsorption, at 45.0 ºC and pH 4.0. In the photocatalytic runs an optimum for temperature and pH was also observed. At 45 ºC and pH 4.0 the removal of DMDS was 99% after 60 min of irradiation.

Avaliação da degradação do diclofenaco sódico utilizando H2O2/fenton em reator eletroquímico

This paper describes a degradation study of the anti-inflammatory sodium diclofenac in aqueous medium using an electro-chemical flow reactor with a gas diffusion electrode as cathode. Two degradation processes were compared: by H2O2 electro-generated and H2O2 electro-generated/Fe(II). Concentration of sodium diclofenac was determined during the experiments by HPLC. The changes in chemical oxigen demand (COD) were also evaluated. Under the specific reaction conditions, 350 mg L-1 of H2O2 was electro-generated and 99.2% of sodium diclofenac was degradated, with 27.4% COD reduction. At the same conditions, but using Fe(II), drug degradation was 99.4% and the COD reduction was 63.2%.

Um panorama sobre a abordagem ambiental no currículo de cursos de formação inicial de professores de química da região sudeste

This work analysed the contents of 701 disciplines from 22 chemistry courses that prepare chemistry teachers in 16 public Universities in Southeastern Brazil. Only a small number (23) of disciplines showed an explicit relationship between human activities and the environment. A total of 11 theoretical and 193 experimental disciplines explored to some extent scientific and technological aspects related to the environment, but did not include their relationship with society. As the experimental disciplines supposedly include some kind of waste treatment, this may explain why secondary school chemistry teachers work mainly on recycling programs and waste issues at their schools. The aim of this work is to provide information on which to base a much needed discussion about how to better prepare our chemistry teachers to act as Environmental Educators at school, as the Brazilian Education Legislation requires.

Estudo da especiação de arsênio inorgânico e determinação de arsênio total no monitoramento ambiental da qualidade de águas subterrâneas

This work reports an alternative, fast and robust method, for the determination of total As, As(III) and As(V) by HG-AAS without the use of prereductants. The method is based on the different rates of arsine formation of the inorganic As species and the effect of As(III) in the signal obtained for total As. Groundwater and mineral spiked waters were used to sample preservation evaluation. The method was validated by the determination of As in SRM 1640 and used in the determination of total As and its inorganic species in groundwater samples collected from mines in the Iron Quadrangle - MG.