Quantificação e utilização das frações húmicas como característica diferencial em horizontes diagnósticos de solos Brasileiros

As informações obtidas pela distribuição das frações húmicas podem ser utilizadas em estudos pedológicos brasileiros como atributo diagnóstico ou característica diferencial e, assim, contribuir para a evolução do Sistema Brasileiro de Classificação de Solos (SiBCS). Os objetivos deste trabalho foam quantificar o C orgânico das frações húmicas de horizontes diagnósticos superficiais e subsuperficiais de solos e propor a utilização no Sistema Brasileiro de Classificação de Solos. Foram utilizados 169 horizontes diagnósticos distribuídos entre O hístico, H hístico, A chernozêmico, A húmico e B espódico. Eles foram avaliados quanto à composição química e física. Quantificaram-se os teores de C orgânico nas frações: ácidos fúlvicos (C-FAF), ácidos húmicos (C-FAH) e humina (C-HUM). Foram calculadas as relações C-FAH/C-FAF, C-EA/C-HUM e C-EA/COT (C-EA = C-FAF + C-FAH) e o percentual de cada fração em relação a C orgânico total (COT), %FAF, %FAH, %HUM e %EA (extrato alcalino). Os horizontes O e H hístico apresentaram predomínio do C-HUM, seguido do C-FAH; o A chernozêmico, dominância absoluta do C-HUM; o A húmico, predomínio da C-HUM, seguido do C-FAH; e o B espódico, maior expressividade de C-FAH ou do C-FAF. Com base na avaliação da distribuição das frações húmicas, propõe-se o uso das seguintes características diferenciais para os níveis de família e série do SiBCS: matéria orgânica estável (horizontes minerais superficiais) - C-EA/C-HUM (< 0,5); matéria orgânica iluvial (horizontes minerais subsuperficiais) - C-EA/C-HUM (> 2,0); e potencial de lixiviação (sistema ou solo) - C-FAH/C-FAF e C-EA/C-HUM (> 1,0).

New methods to quantify NH3 volatilization from fertilized surface soil with urea

Gaseous N losses from soil are considerable, resulting mostly from ammonia volatilization linked to agricultural activities such as pasture fertilization. The use of simple and accessible measurement methods of such losses is fundamental in the evaluation of the N cycle in agricultural systems. The purpose of this study was to evaluate quantification methods of NH3 volatilization from fertilized surface soil with urea, with minimal influence on the volatilization processes. The greenhouse experiment was arranged in a completely randomized design with 13 treatments and five replications, with the following treatments: (1) Polyurethane foam (density 20 kg m-3) with phosphoric acid solution absorber (foam absorber), installed 1, 5, 10 and 20 cm above the soil surface; (2) Paper filter with sulfuric acid solution absorber (paper absorber, 1, 5, 10 and 20 cm above the soil surface); (3) Sulfuric acid solution absorber (1, 5 and 10 cm above the soil surface); (4) Semi-open static collector; (5) 15N balance (control). The foam absorber placed 1 cm above the soil surface estimated the real daily rate of loss and accumulated loss of NH3N and proved efficient in capturing NH3 volatized from urea-treated soil. The estimates based on acid absorbers 1, 5 and 10 cm above the soil surface and paper absorbers 1 and 5 cm above the soil surface were only realistic for accumulated N-NH3 losses. Foam absorbers can be indicated to quantify accumulated and daily rates of NH3 volatilization losses similarly to an open static chamber, making calibration equations or correction factors unnecessary.

Ciência de espumas - aplicação na extinção de incêndios

The structural characteristics of foams are responsible for a broad range of applications of this system. Foams produced by aqueous solutions of surfactant concentrates are used in fire-fighting due to their special properties as extinguishing agents. In the present paper we discuss the main aspects involved in fire-fighting, based on some properties of foams. Thermal and chemical stability, good wetting of surfaces, cooling effect by water drained from the bubbles, isolation of the air from the burning surface and suppression of flammable vapors are some of the factors involved in the extinguishment of fire by foams.

Fundamentals of beer and hop chemistry

Beer brewing is an intricate process encompassing mixing and further elaboration of four essential raw materials, including barley malt, brewing water, hops and yeast. Particularly hops determine to a great extent typical beer qualities such as bitter taste, hoppy flavour, and foam stability. Conversely, hop-derived bitter acids account for an offending lightstruck flavour, which is formed on exposure of beer to light. These various processes are presented in detail, while due emphasis is placed on state-of-the-art hop technology, which provides brewers with efficient means to control bitterness, foam, and light-stability thereby allowing for the production of beers with consistent quality.

Espectrofotometria derivativa: uma estratégia simples para a determinação simultânea de corantes em alimentos

A very simple spectrophotometric method is described for resolving binary mixture of the food colorants Sunset Yellow (INS 110) and Tartrazine Yellow (INS 102) by using the first derivative spectra with measurements at zero-crossing wavelengths. Before the spectrophotometric measurements, the dyes were sorbed onto polyurethane foam and recovered in N,N-dimethilformamide. Commercial food products (gelatine and juice powder) were analysed by using the proposed method and the HPLC technique. The results are in very good agreement and the differences between the methods is not statistically important. Therefore, the first-order derivative spectrophotometric method is accurate, precise, reliable and could be applied to the routine analysis of food samples.

Polipeptídeos e proteínas com influência na qualidade da espuma da cerveja e métodos analíticos utilizados no seu estudo

A review of polypeptides and proteins that influence, direct or indirectly, beer foam quality, as well as the most relevant analytical methods used in their study, are presented. Protein Z, LTP1 and hordein/glutelin fragments originated from malt have a direct influence on beer foam quality. Other proteins, like malt hordeins and albumins and wheat puroindolines, are, to some degree, also important for beer foam quality. Protein hydrophobicity is pointed out as a key parameter to enhance foam quality. Electrophoretic, chromatographic and immunological analytical methods are currently used to study polypeptides and proteins present in barley, malt, wort, beer, and foam. Best results are obtained when combinations of these methods are applied.

Uso da pressão gerada por uma coluna de água para controle da vazão em sistemas de análises em fluxo

This work presents a new approach to control the flow rate in hydrodynamic flow experiments. The combination of air pressure generated by an aquarium air pump and the pressure generated by a water column were used for this purpose. This device supports a stable flow rate without pulsation for a long period of time. Furthermore, the flow rate can be easily controlled at various values in one or more streams. The performance of this approach was investigated using Fe(CN)6(4-) solutions in flowing systems using amperometric and voltammetric detection in wall-jet configuration. The results showed that the performance of the proposed device was better than a commercial peristaltic pump. It suggests that this approach can be used successfully in flow analysis systems.

Construção de um sistema simples e compacto de recirculação d'água sob pressão para trompa d'água

Vacuum pumps are very useful in physical, chemical and biological experiments. In this communication it is described the design of a compact and low cost water recirculating system employing a water-jet aspirator pump as the vacuum source. The system requires only a water pump, water-jet aspirator pump, commercial PVC water tubes and a drain connection.

Estudo da sorção do corante catiônico violeta cristal por espuma de poliuretano em meio aquoso contendo dodecilsulfato de sódio

This work presents a detailed study about the sorption of crystal violet (CV) cationic dye onto polyether type polyurethane foam (PUF). The sorption process was based on the formation of an ionic-pair between cationic dye and dodecylsulfate anion (SDS), which presented high affinity by PUF. Set-up employed in the study was built up by adjusting a 200 mg cylinder of PUF to the arm of an overhead stirrer. The system was characterized in relation to equilibrium and kinetic aspects and it was modeled by employing Langmuir and Freundlich isotherms. Obtained results showed that the ratio between SDS and MB concentrations played an important role on the sorption process. According to results found it was possible to retain up to 3.4 mg of dye from 200 mL of a 5.0 x 10-5 mol L-1 CV solution containing 1.25 x 10-4 mol L-1 SDS, which represented a removal efficiency of around 92%.

Construção e caracterização de um detector eletroquímico para análises em fluxo

The present work describes a low-cost electrochemical "wall-jet" detector for flow analysis. The electrolytic solution enters into the cell through a tube of stainless steel (200 to 300 µm i.d), reaching to the center of the working electrode perpendicularly and then being mixed to the remaining solution in the cell, which flows under atmospheric pressure into a waste reservoir. The proposed electrochemical detector can be used with any type of working electrode, from commercial to home-made, such as glassy carbon and metallic electrodes (modified or unmodified), which enlarge the applications of the electrochemical detector.

Produção e caracterização de espumas cerâmicas obtidas a partir de lodo de anodização de alumínio

Ceramic foams were produced from a sludge generated in the aluminum anodizing process by using an industrial polyurethane foam (replication method) with open cell sizes of 10 ± 5 ppi (porosity = 97%) which were impregnated with suspensions containing 50-61 wt.% alumina, 1 wt.% citric acid, 6 wt.% bentonite and fired at 1600 ºC for 2 h. The aluminum anodizing sludge shows a high alumina content (87.5 wt.%) and a low particle size (~1.7 mm) after calcination and milling. The obtained filters show porosity of approximately 70%, filtration capability (mass water flow) of 1.7 kg/s and mechanical strength under compression of 2.40 MPa.

Processamento de cartuchos de impressoras de jato de tinta: um exemplo de gestão de produto pós-consumo

This work presents a route for processing spent ink-jet cartridges in an experimental course. The disassembly of the cartridges requires several steps and the recognition of their different components is essential to define the best final destination (recycling, co-processing). The plastic strips were chemically processed so as to recover gold and copper. The students recognized the difficulty of processing multicomponent wastes and the importance of the chemical work under the best safety conditions; they also experienced many laboratory techniques and recognized the value of the selective collection and the reverse logistics to reach a viable commercial scale recycling.

Química e sustentabilidade: novas fronteiras em biocombustíveis

This contribution discusses the state of the art and the challenges in producing biofuels, as well as the need to develop chemical conversion processes of CO2 in Brazil. Biofuels are sustainable alternatives to fossil fuels for providing energy, whilst minimizing the effects of CO2 emissions into the atmosphere. Ethanol from fermentation of simple sugars and biodiesel produced from oils and fats are the first-generation of biofuels available in the country. However, they are preferentially produced from edible feedstocks (sugar cane and vegetable oils), which limits the expansion of national production. In addition, environmental issues, as well as political and societal pressures, have promoted the development of 2nd and 3rd generation biofuels. These biofuels are based on lignocellulosic biomass from agricultural waste and wood processing, and on algae, respectively. Cellulosic ethanol, from fermentation of cellulose-derived sugars, and hydrocarbons in the range of liquid fuels (gasoline, jet, and diesel fuels) produced through thermochemical conversion processes are considered biofuels of the new generation. Nevertheless, the available 2nd and 3rd generation biofuels, and those under development, have to be subsidized for inclusion in the consumer market. Therefore, one of the greatest challenges in the biofuels area is their competitive large-scale production in relation to fossil fuels. Owing to this, fossil fuels, based on petroleum, coal and natural gas, will be around for many years to come. Thus, it is necessary to utilize the inevitable CO2 released by the combustion processes in a rational and economical way. Chemical transformation processes of CO2 into methanol, hydrocarbons and organic carbonates are attractive and relatively easy to implement in the short-to-medium terms. However, the low reactivity of CO2 and the thermodynamic limitations in terms of conversion and yield of products remain challenges to be overcome in the development of sustainable CO2 conversion processes.

Use of experimental design in the optimisation of a solid phase preconcentration system for Cobalt determination by GFAAS

In this work is proposed a solid phase preconcentration system of Co2+ ions and its posterior determination by GFAAS in which fractional factorial design and response surface methodology (RSM) were used for optimization of the variables associated with preconcentration system performance. The method is based on cobalt extraction as a complex Co2+-PAN (1:2) in a mini-column of polyurethane foam (PUF) impregnated with 1-(2-pyridylazo)-naphthol (PAN) followed by elution with HCl solution and its determination by GFAAS. The chemical and flow variables studied were pH, buffer concentration, eluent concentration and preconcentration and elution flow rates. Results obtained from fractional factorial design 2(5-1) showed that only the variables pH, buffer concentration and interaction (pH X buffer concentration) based on analysis of variance (ANOVA) were statistically significant at 95% confidence level. Under optimised conditions, the method provided an enrichment factor of 11.6 fold with limit of detection and quantification of 38 and 130 ng L-1, respectively, and linear range varying from 0.13 to 10 µg L-1. The precision (n = 9) assessed by relative standard deviation (RSD) was respectively 5.18 and 2.87% for 0.3 and 3.0 µg L-1 cobalt concentrations.

Determinação amperométrica de iodeto em soluções expectorantes orais com análise por injeção em fluxo usando a reação iodeto/nitrito

Neste trabalho foi desenvolvido um sistema de injeção em fluxo visando à determinação amperométrica de íons iodeto em soluções expectorantes. O método é baseado na reação do iodeto com íons nitrito em meio ácido. O iodo formado é monitorado por amperometria no potencial de +200 mV vs. Ag/AgCl (3 mol L-1), usando um eletrodo de trabalho de disco de platina (RDE) com raio = 0,75 mm adaptado a uma célula eletroquímica "wall-jet". O sistema em fluxo foi usado com o carregador impulsionado pela pressão gravitacional dos reagentes (carregador: solução 2 x 10-4 mol L-1 em NaNO2 e 0,2 mol L-1 em H2SO4), na vazão de 4 mL min-1. O método é rápido (acima de 100 injeções h-1) e preciso (RSD = 1,9%; n=10 e C I 8 x 10-6 mol L-1), apresentando um limite de detecção de 20 ng I- ou 8 x 10-7 mol L-1 (3SD). A validação do método proposto foi realizada seguindo as normas USP, ou seja, titulação potenciométrica com AgNO3 0,100 mol L-1 e os resultados obtidos mostraramse concordantes com os valores de referência do fabricante.