A tecnologia da reciclagem de polímeros

Solid municipal waste contains a large volume of polymers and its final disposal is a serious environmental problem. Consequently, the recycling of the principal polymers present in the solid waste is an alternative. In this review we describe the mechanical and chemical recycling of polymers and the energy recovery from plastic wastes. Polymer recycling involves not only the development of processing technologies, but also the solution of many chemical and analytical problems. The technological, economical and social aspects of polymer recycling are also considered.

Análise sistemática de reagentes e resíduos sem identificação

This work presents a detailed routine applied to the identification of unknown chemicals and wastes. 786 specimens were analyzed during 20 months. Unknown materials fell into three basic classes: (i) commercial chemicals without labels or illegible ones; (ii) laboratory synthesis products; (iii) used solvents (including mixtures). Uranium and thorium were recovered form their wastes. Unknown chemicals were mainly inorganic compounds, many of which had never been opened. Alkaline salts were dominant, but also precious metal compounds were identified. Laboratory synthesis products were organic compounds. The final destination depended on the nature of the chemical. Most organic compounds were sent to incineration; inorganic salts were distributed among several public organizations, including secondary and technical schools. The work described in this paper greatly reduced the amount of wastes that had to be sent to disposal.

Resíduos sólidos de curtumes como adsorventes para a remoção de corantes em meio aquoso

The tanning process in the leather industry generates very high quantities of chromium-containing solid waste ("wet blue" leather). Environmental concerns and escalating landfill-costs are becoming increasingly serious problems for the leather industry and an alternative disposal is needed. In this work, we are presenting a novel application for this solid waste, which is the removal of organic contaminants from aqueous-solution. The adsorption isotherm of "wet blue" leather waste from the AUREA tanning company in Erechim-RS (Brazil) showed that this material presents high adsorption capacities of the reactive textile dyes.

Uso de lodo de estação de tratamento de água centrifugado em matriz de concreto de cimento portland para reduzir o impacto ambiental

An alternative application of the humid sludge from the Passaúna WTP, located in Curitiba's metropolitan area, is proposed for concrete structures, partially replacing aggregates and cement. For the investigation, a reference concrete and four concrete mixtures with sludge were produced, and from these, two mixtures, containing 4% and 8% of sludge (m/m), were analyzed by different techniques: X ray fluorescence, X ray diffraction, thermo-gravimetric analysis, physicochemical analysis, compressive strength, etc. The properties were evaluated and the results indicate that the mixtures can be applied in different situations as cast structures for construction of concrete walls. Mixtures with more than 4% of sludge are restricted to applications where the workability of the concrete is not required, such as for residential pavements, sidewalks and stepping floors.

Caracterização de 2,2',4,4',6,6'-hexanitroestilbeno via análises instrumentais

2,2',4,4',6,6'-hexanitrostilbene (HNS) is a very important high explosive that is used in a range of military, aerospace and industrial formulations owing to its suitable properties. It is an insensitive and thermaly stable explosive that can be produced from 2,4,6-trinitrotoluene (TNT). This paper shows the characterization of synthesized HNS by different techniques, such as elementary analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR) and through the determination of the heat of combustion in a calorimeter.

Incorporação de CuSO4 residual em argamassa, como método de disposição final

Residual CuSO4 was incorporated into the mass utilized for cement preparation. To a cement mass with 1:0.5:5 of cement, lime and sand to 0.25, 0.50, 0.75 and 1.00% of residual CuSO4 were added. The sulfate was mixed separately with lime and water to induce metal precipitation. The hardened test bodies were submerged in Milli-Q water for three months. No Cu was detected in the water by Atomic Absorption Spectrometry. The best proportion for mechanical resistance and porosity is 0.50%. The cement is adequate for non-structural objects.

Polímeros biodegradáveis - uma solução parcial para diminuir a quantidade dos resíduos plásticos

The large use of plastics has generated a waste deposit problem. Today plastic wastes represent 20% in volume of the total waste in the municipal landfills. To solve the disposal problem of plastics methods have been employed such as incineration, recycling, landfill disposal, biodegradation and the use of biodegradable polymers. Incineration of plastic wastes provokes pollution due to the production of poisonous gases. Recycling is important to reduce final costs of plastic materials, but is not enough in face of the amount of discarded plastic. In landfills plastic wastes remain undegraded for a long time, causing space and pollution problems. Biodegradation is a feasible method to treat some plastics, but intensive research is necessary to find conditions for the action of microorganisms. All of these methods are important and the practical application of each one depends on the type and amount of the plastic wastes and the environmental conditions. Therefore, a great deal of research has focused on developing biodegradable plastics and its application because it is an important way for minimizing the effect of the large volume of plastic waste discarded in the world.

Alilação e crotilação catalítica e enantiosseletiva de aldeídos

The field of chiral catalysis has experienced explosive growth over the last two decades. By now, many of the classical reactions in organic synthesis can be carried out efficiently in asymmetric manner. As one of the fundamental and powerful C-C bond-forming reactions, enantioselective catalytic allylation (ECA) and crotylation (ECC) of aldehydes has attracted considerable attention. In this article, we present an overview about the importance of chiral Lewis acids and bases in catalytic enantioselective addition of allyl- and crotyl metals to aldehydes and the application of this methodology in the total synthesis of natural and non-natural products.

Sistema aquoso bifásico: uma alternativa eficiente para extração de íons

Solvent extraction has been successfully applied to metal ion preconcentration and often meant the use of toxic organic diluents. However, regulatory pressure is increasingly focusing on the use and disposal of organic solvents, and thus the development of nonhazardous alternatives is important. In this review, we examine the application of aqueous biphasic systems (ABS) to extraction of ions, analyzing their potential and limitations and suggest that ABSs could be an efficient substitute for oil/water biphasic systems. ABSs are formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two water-soluble polymers.

Interferentes endócrinos no ambiente

Although the hypothesis that environmental chemicals may exhibit endocrine disrupting effects is not new, the issue has been a growing level of concern due to reports of increased incidences of endocrine-related disease in humans, including declining male fertility, and more significantly, to adverse physiological effects observed in wildlife where cause and effect relationships are more evident. The list of endocrine disrupting chemicals (EDCs) includes a range of anthropogenic compounds, phytoestrogens, naturally occurring sex steroids and synthetic estrogens. Within the aquatic environment, the presence of EDCs has concerned many scientists and water quality regulators. Discharge of effluents from treatment facilities is likely to be a significant source of input of contaminants to many systems, and the potential for concentration of hydrophilic compounds and transformation products within sludges has implications for their disposal. Then, understanding the processes and the fate of EDCs on the environment, as well as the mechanisms of endocrine disruption, may facilitate controlling or limiting exposure of both humans and the environment to these compounds.

Teores de nitrato (NO3-) e amônio (NH4+) nas águas do aqüífero Barreiras nos bairros do Reduto, Nazaré e Umarizal - Belém/PA

This paper evaluates the occurrence of nitrate and ammonium in the Barreiras aquifer in the metropolitan area of Belém, Pará State, Brazil. The results show that some wells display ammonium and nitrate concentrations above or close to the limits of water potability regulations. The main cause of the pollution of these waters is related the local disposal of domestic effluents and/or leakage from pipes of old sewage systems.

Avaliação das técnicas de precipitação química e encapsulamento no tratamento e destinação conjunta de resíduos líquidos contendo cromo e vidrarias de laboratório

In this paper, we present procedures for the treatment and final disposal of residual solutions containing chromium, in order to evaluate the effectiveness of chemical precipitation of the metal and the potential of the glass encapsulation technique, using broken laboratory glassware. The results demonstrated that pH-values convenient for chemical precipitation are between 10 - 11. With regard to Cr(OH)3 encapsulation, the leaching and solubilization tests allowed to classify the waste as non-dangerous and non-inert. Finally, it is pointed out that the adoption of waste management practices in universities should be encouraged, helping to train professionals skilled in good laboratory practices.

Educação ambiental nas escolas da região de Ribeirão Preto (SP): concepções orientadoras da prática docente e reflexões sobre a formação inicial de professores de química

During short courses, 95 secondary school teachers from 49 state schools and 421 students from the Ribeirão Preto region (in Sao Paulo state, Brazil, with a population of 530,000) were asked to fill in different questionnaires. The points raised in the teacher's questionnaire were used as a guide to establish a continuous dialogue during the short courses. Most of the schools claimed to have some kind of environmental education (EE). Based on the questionnaires and dialogues we analyzed how the teachers' perceptions on EE reflect on the views secondary students hold about their own responsibility for preserving the environment. The role of universities in the preparation of chemistry teachers capable of effectively approaching EE is also discussed.

Estudo sobre a utilização da lama vermelha para a remoção de corantes em efluentes têxteis

Red mud is the principal residue of the alumina (Al2O3) industry. Generated during the Bayer process, it is characterized by strong alkalinity and ion exchange. Iron oxides are the principal component (30 to 60%). Annually millions of tons of red mud are generated in the world. Red mud disposal is responsible for a large part of the cost of alumina production. On the other hand, textile industry wastewaters containing dyes have a great impact on the environment and on human health. In this paper the possibility of applying red mud for the removal of dyes was investigated by two processes: adsorption and degradation by the Fenton reagent.

Determinação quantitativa de TNT e HNS por TG e FT-IR

2,4,6-trinitrotoluene (TNT) is an energetic material that shows scarce crystalline properties that can be improved by addition of 2,2',4,4',6,6'-hexanitrostilbene (HNS) in the crystallization process. HNS is a very important high explosive used in a variety of military, aerospace and industrial formulations owing to its suitable properties. It is an insensitive and thermal stable explosive that can be produced from 2,4,6-trinitrotoluene (TNT). The purpose of this work is the quantitative determination of HNS and TNT in explosives by thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR).