Desenvolvimento sustentável e química verde

The world is in a process of awakening with respect to the environment. Our society has started to recognize that the environment is one of our largest resources and has begun legally enforce its protection. In Brazil, the environmental law is constitutionally guaranteed. International treaties have been signed, amongst them the Agenda 21 which is a commitment to sustainable development. Green Chemistry is a strategy that helps make this commitment. The literature presents many examples of studies of the application of Green Chemistry philosophy. In this paper we will present some points that we believe to be important and promising.

Uso da casca de coco verde como adsorbente na remoção de metais tóxicos

Green coconut shells were treated with acid, base and hydrogen peroxide solutions for 3, 6, 12 and 24 h for removing toxic metals from synthetic wastewater. The removal of ions by the adsorbent treated with 0.1 mol L-1 NaOH/ 3h was 99.5% for Pb2+ and 97.9% for Cu2+. The removal of Cd2+, Ni2+, Zn2+, using adsorbent treated with 1.0 mol L-1 NaOH/3 h, was 98.5, 90.3 and 95.4%, respectively. Particle size, adsorbent concentration and adsorption kinetics were also studied. An adsorbent size of 60-99 mesh and a concentration of 30-40 g/L for 5 min exposure were satisfactory for maximum uptake of Pb2+, Ni2+, Cd2+, Zn2+ and Cu2+ and can be considered as promising parameters for treatment the aqueous effluents contaminated with toxic metals.

Teor de fluoretos em infusões de chá verde (Camellia sinensis)

The aim of this work was to study the influence of green tea consumption on fluoride ingestion. The extraction conditions of fluorides from green tea infusions were defined and nine brands of green tea available in Portugal were analyzed. The quantification of fluorides in the green tea was preceded by the implementation and validation of the potentiometric method (commercial fluoride selective electrode). The concentration of fluorides in the samples ranged from 0. 8 to 2. 0 mg L-1.

Síntese do pigmento cerâmico verde vitória (Ca3Cr2Si3O12) a partir de CaCO3, Cr2O3 e SiO2

The synthesis of the ceramic pigment Victoria Green (Ca3Cr2Si3O12 ) is described. As raw materials CaCO3, Cr2O3, and SiO2 obtained from rice husk were used. Borax was used as mineralizer. Raw materials were formulated stoichiometrically and calcined from 1000 to 1200 ºC for 180 min. The main phase detected was uvarovite with particle size below 45 mm. The pigments were applied on ceramic tiles and sintered at 1150 ºC for 40 min. The synthesis process showed to be adequate to produce the green pigment, whose characteristics resemble those of a commercial pigment.

Produção e caracterização de carvão ativado produzido a partir do defeito preto, verde, ardido (PVA) do café

The black, green and sour coffee defect (PVA) contributes with 20% of the total coffee production. It should be separate from the normal coffee grains in order to improve the final quality of the beverage. In this way, the present work has the objective to use the PVA reject for the production of activated carbon. The activated carbon (CA) was prepared from PVA defect using zinc chloride as activating agent. The prepared material (CA PVA) was characterized and the adsorption tests were carried out using as organic models methylene blue (AM) and reactive red (VR). The CA PVA revealed to be more efficient in the removal of the organic contaminants compared to a commercial activated carbon.

Validação de métodos cromatográficos de análise: um experimento de fácil aplicação utilizando cromatografia líquida de alta eficiência (CLAE) e os princípios da "Química Verde" na determinação de metilxantinas em bebidas

The validation of analytical methods is an important step in quality control. The main objective of this study is to propose an HPLC experiment to verify the parameters of validation of chromatographic methods, based on green chemistry principles, which can be used in experimental courses of chemistry and related areas.

Compostos bioativos do café: atividade antioxidante in vitro do café verde e torrado antes e após a descafeinação

This study aimed to evaluate the effect of coffee decaffeination with dichloromethane on the in vitro antioxidant activity of this matrix. It were determined the content of total phenolics, chlorogenic acid and caffeine of the coffee samples. The assessment of the antioxidant potential was investigated by DPPH radical scavenging method, reducer power and Fe2+chelation activity. The process of decaffeination and roasting caused changes in the levels of the compounds investigated. The results show that the decaffeination by the dichloromethane method reduces the in vitro antioxidant potential of coffee.

Uma métrica gráfica para avaliação holística da verdura de reacções laboratoriais - "Estrela Verde"

A new semi-quantitative metrics, Green Star (GS), for evaluation of the global greenishness of chemical reactions used in teaching laboratories has been developed. Its aim is to help choosing the more acceptable reactions for implementing Green Chemistry (GC) and to identify suitable modifications of reaction protocols to improve the greenishness of chemistry. GS considers globally all the Twelve Principles of GC. To illustrate its construction, the tetraamminecopper(II) sulfate monohydrate laboratory synthesis, performed under several sets of conditions to pursue greenishness, is presented. A comparative study with other GC metrics showed the advantages of GS and that it accomplishes its purpose.

Um método verde, rápido e simples para determinar o valor energético de farinhas e cereais matinais

The Energy Value (EV) corresponds to the sum of the energetic contributions from food macronutrients (proteins, carbohydrates and fats) and is required on the labels of pre-packaged foods. The determinations of these parameters are based on distinct analytical procedures, each one being time-consuming, laborious and producing residues. This work presents multivariate models to determine the EV contents of industrialized foods for human consumption by using X-ray fluorescence spectra of samples with known parameters, determined through conventional methods. The proposed method is an alternative to conventional analytical methods and does not require any reagent, given the demands of the "green chemistry".

Estudo químico de uma amostra de própolis verde de Passa Quatro, Minas Gerais, Brasil

The phytochemical investigation of a sample of propolis from Passa Quatro-Minas Gerais State, Brazil, where nine constituents were isolated: a mixture of α- and β-amyrin, lupeol, a mixture of flavonols ramnocitrin and eupalitin, acacetin, 3-prenyl-4-hydroxycinnamic acid, 3,5-diprenyl-4-hydroxycinnamic acid the new compound, the (E)-3-[4-(3-phenylpropanoiloxy)]-3,5-diprenil-cinnamic acid. The structures of the isolated compounds were characterized by 1D- and 2D-NMR experiments, MS and IR spectrometry, and comparison with data described in the literature.