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.

Recuperação de metais de catalisadores de hidrorrefino usados via fusão com KHSO4

This work describes a process for metal recovery from spent NiMo and CoMo/Al2O3 commercial hydrorefining catalysts. The samples were treated by fusion with potassium hydrogen sulfate (5 h, 600 ºC) with a KHSO4/catalyst mass ratio of 10:1. After fusion the solid was solubilized in water (100 ºC), leaving silicon compounds as residue. Losses of nickel and cobalt may reach 16 wt% of the amount present in the sample, depending on the silicon content. Soluble metals were isolated by selective precipitation techniques (nickel, cobalt, aluminum) or by solvent extraction with methyl-isobutyl ketone (molybdenum) in a hydrochloric acid medium. All metals were recovered in very good yields except for nickel and cobalt in the presence of considerable amounts of silicon. Soluble wastes consist of potassium/sodium sulfates/chlorides. Solid wastes correspond to about 4 wt% of the catalyst and can be discarded in industrial dumps.

Alquilbenzeno sulfonato linear: uma abordagem ambiental e analítica

The environmental impact of detergents and other consumer products is behind the continued interest in the chemistry of the surfactants used. Of these, linear alkylbenzene sulfonates (LASs) are most widely employed in detergent formulations. The precursors to LASs are linear alkylbenzenes (LABs). There is also interest in the chemistry of these hydrocarbons, because they are usually present in commercial LASs (due to incomplete sulfonation), or form as one of their degradation products. Additionally, they may be employed as molecular tracers of domestic waste in the aquatic environment. The following aspects are covered in the present review: The chemistry of surfactants, in particular LAS; environmental impact of the production of LAS; environmental and toxicological effects of LAS; mechanisms of removal of LAS in the environment, and methods for monitoring LAS and LAB, the latter in domestic wastes. Classical and novel analytical methods employed for the determination of LAS and LAB are discussed in detail, and a brief comment on detergents in Brazil is given.

Química Analítica de Processos

Process Analytical Chemistry (PAC) is an important and growing area in analytical chemistry, that has received little attention in academic centers devoted to the gathering of knowledge and to optimization of chemical processes. PAC is an area devoted to optimization and knowledge acquisition of chemical processes, to reducing costs and wastes and to making an important contribution to sustainable development. The main aim of this review is to present to the Brazilian community the development and state of the art of PAC, discussing concepts, analytical techniques currently employed in the industry and some applications.

Parâmetros operacionais no processamento de zeólitas desativadas por fusão com KHSO4

This work presents a study on the determination of the optimal experimental conditions for processing spent commercial zeolites in order to recover lanthanide elements and eventually other elements. The process is based on the fusion of the sample with potassium hydrogenosulfate (KHSO4). Three experimental parameters were studied: temperature, reaction time and catalyst/flux mass ratio. After fusion the solid was dissolved in water and the amount of insoluble matter was used to determine the efficiency of the process. The optimized experimental parameters depend on the composition of the sample processed. Under such conditions the insoluble residue corresponds to SiO2. Lanthanide elements and aluminum present in solution were isolated by conventional precipitation techniques; the yields were at least 75 wt%. The final generated wastes correspond to neutral colorless solutions containing alkali chlorides/sulfates and solids that can be disposed of in industrial dumps.

Recuperação de cádmio de baterias níquel-cádmio via extração seletiva com tributilfosfato (TBP)

This work describes a recovery process of cadmium from spent nickel-cadmium batteries by a new hydrometallurgical route based on the selective extraction in hydrochloric acid medium with tributylphosphate (TBP), alone or dissolved in kerosene. The best results were obtained when TBP concentration was at least 75 vol%. Nickel extraction was negligible under these conditions. It was isolated after processing the rafinate through an anionic ion-exchange column. Final wastes generated are basically sodium chloride solutions, with no turbidity, color or heavy metals present in significant amounts.

Pré-tratamentos de melaço de cana-de-açúcar e água de maceração de milho para a bioprodução de carotenóides

This work studied the pretreatment of sugarcane molasses (CM) and corn steep liquor (CS) for the production of carotenoids by Sporidiobolus salmonicolor (CBS 2636). The acid pretreatment removed less micronutrients than that with activated carbon and led to high removals of Cu and Mn. Reduction in optical density of the prepared medium and removal of glucose from it were 22% and 7% for CM and 95% and 38% for CS, respectively. Total carotenoids obtained with substrates pretreated with acids (541 mg/L) were higher than the results obtained when the medium was treated with activated carbon (208 mg/L).

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.

Rota hidrometalúrgica de recuperação de molibdênio, cobalto, níquel e alumínio de catalisadores gastos de hidrotratamento em meio ácido

This work describes a hydrometallurgical route for processing spent commercial catalysts (CoMo and NiMo/Al2O3). Samples were preoxidized (500 ºC, 5 h) in order to eliminate coke and other volatile species present. The calcined solid was dissolved in concentrated H2SO4 and water (1:1 vol/vol) at 90 ºC; the insoluble matter was separated from the solution. Molybdenum was recovered by solvent extraction using tertiary amines at pH around 1.8. Cobalt (or nickel) was separated by addition of aqueous ammonium oxalate at the above pH. Phosphorus was removed by passing the liquid through a strong anion exchange column. Aluminum was recovered by neutralizing the solution with NaOH. The route presented in this work generates less final aqueous wastes because it is not necessary to use alkaline medium during the metal recovery steps.

Extração líquido-líquido de ferro(III) e titânio(IV) pelo ácido bis-(2-etil-hexil) fosfórico (D2EHPA) em meio de ácido sulfúrico

This work presents a study on the separation of Fe(III) and Ti(IV) from sulfuric acid leaching solutions of ilmenite (FeTiO3) using liquid-liquid extraction with D2EHPA in n-dodecane as extracting agent. The distribution coefficients (K D) of the elements related to free acidity and concentration of Fe(III) and Ti(IV) were determined. Free acidity was changed from 3x10-2 to 11.88 mol L-1 and D2EHPA concentration was fixed at 1.5 mol L-1. Recovery of final products as well as recycling of wastes generated in the process were also investigated. The LLE process as a feasible alternative to obtain high-purity TiO2.

Preparação de carvão ativado em baixas temperaturas de carbonização a partir de rejeitos de café: utilização de FeCl3 como agente ativante

Ferric chloride as a new activating agent was used to obtain activated carbons from agroindustrial waste. This material was prepared at three temperatures of pyrolysis, 200, 280 and 400 ºC. The carbonaceous materials obtained after the activation processes showed high specific surface areas (BET), with values higher than 900 m² g-1. The materials showed different behaviors in the adsorption of methylene blue dye and reactive red textile dye in water solutions. An important fact in the use of FeCl3 as an activating agent is that the activation temperature is at 280 ºC, well below of those commonly employed in chemical or physical activations described in the literature.

Caracterização e classificação de resíduo sólido "pó de rocha granítica" gerado na indústria de rochas ornamentais

The ornamental rock industry generates huge amounts of wastes during the process of extraction and sawing of rock blocks. The ornamental rock powder waste is a non-biodegradable material, which represents the increase in environmental problem. The waste was collected from a granitic rock sawing plant located in Santo Antônio de Pádua, Rio de Janeiro. The chemical-environmental characterization and classification of the waste were done according to ABNT standards. The results showed that the granitic rock powder waste should be classified as Class II A - "No Inert", because of its high concentrations of lead, chrome, iron and manganese.

Processamento de pilhas do tipo botão

This work presents hydrometallurgical routes for recovering valuable elements from spent button cells, based on leaching of internal components with sulfuric acid (Li/MnO2 and Zn-air) or nitric acid (Ag-Zn), at 90 ºC for 2h. Slow evaporation of the leachate crystallized MnSO4.H2O, whereas lithium was partially recovered as LiF. Mercury present in Zn-air and Ag-Zn samples was precipitated as HgS. Silver was recovered as AgCl before mercury precipitation. Zinc and iron were precipitated as hydroxides. The amount of iron varied according to the intensity of the corrosion of the external cell case. Final wastes are neutral and colorless sodium sulfate/nitrate solutions.

A gestão de resíduos de laboratório na visão de alunos de um curso de graduação de quimica e áreas afins

This work presents the students´ profile before and after working in the course "Laboratory Chemical Waste Treatment" in the last ten years. The structure of the course is also described. Although students have shown an increasing previous experience on waste management, many fundamental aspects are missing, especially knowledge on the directives focusing environmental aspects. Visits to industrial plants are also essential to better understand the impact of wastes in environment. Most students nowadays consider waste management as an essential part of their professional formation. A good waste management program must consider several topics of extreme relevance.

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.