Birnessite type manganese oxide (δ-MnO2) was synthesized for use in degradation of the cationic dye methylene blue in aqueous solution. The material was characterized using infrared spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller (BET) surface area calculations. The removal of the dye from aqueous solutions was evaluated considering the effects of the following variables: pH, manganese oxide concentration, contact time, and temperature. UV-Vis spectroscopy analyses indicated achievement of 99 and 95% removal of methylene blue (7 mg L-1) at pH 2.0 and 4.0, respectively, after 120 min of contact with the birnessite (100 mg L-1). At higher pH of 6.0 and 8.0, removals of around 99 and 80%, respectively, were obtained after a longer time of 1860 min. Analyses of total organic carbon (TOC) revealed that 80% reduction of organic matter was obtained at pH 4.0. The method of multivariate curve resolution-alternating least squares (MCR-ALS) was used together with UV-Vis spectroscopy to evaluate the removal process, confirming the degradation of methylene blue. Thionine (λmax = 601 nm) was identified as one of the byproducts of N-demethylation of methylene blue. The results indicated that the degradation process started with N-demethylations of the methylene blue molecule.

Effluents from pulp mills have a high organic load and can still contain high organic bio-recalcitrant material that is harmful to the aquatic environment, even after undergoing biological treatment in effluent treatment plants. This study presents a novel treatment method tested on effluents (prior to and after biotreatment) from a Brazilian kraft pulp mill, based on hydroxyl radical production and hydrogen peroxide obtained by plasma generated by high-voltage electrolysis. These species present significant oxidation potential that could enable the complete breakdown of the organic matter. From the application of plasma to treat pulp mill effluent for a 7-hour period, it was obtained a chemical oxygen demand (COD) removal between 88.2 and 99.7%, total organic carbon (TOC) removal of 90.3 to 95.6%, and a color removal of 95.0 to 98.0%. The final pH of the treated effluent was 11.6 to 11.9. The results obtained in this study showed that the high-tension plasma treatment, applied on effluent from kraft pulp mills before and after biological treatment, can be an attractive alternative.

Improper disposal of electronic waste in the environment facilitates migration of heavy metals, especially lead, into the soil and can contribute to the bioavailability of this species. Based on a simplex-centroid mixture experimental design, small-scale tests were performed for incubation of printed circuit boards (PCBs) in mixtures containing organic matter (OM), kaolinite (KA) and iron oxides (IO) to verify lead migration. Regression equations were acquired and were adjusted to the obtained responses. Results showed high total content of Pb, ranging from 400 to 4000 mg kg-1, depending on the mixture and incubation time. Mobility and/or bioavailability of lead in the mixtures were evaluated by a three-step sequential extraction. The bioavailability factor (BF) was obtained from the ratio of the sum of exchangeable fraction (F1) and the organically bound fraction (F2) by F1, F2 and the residual fraction (F3) and the values of bioavailability factor for Pb, the heavy metal considered of greatest environmental concern in this study, ranged between 0.16 and 0.52.

Electrodegradation of atrazine in water was performed using homemade (PA and PB) and purchased (PC) boron-doped diamond anodes. The degradation was monitored off-line by analyzing total organic carbon and high performance liquid chromatography with diode array detector (HPLC-DAD) and at-line by UV spectroscopy. The spectra were recorded every 2 min. The rank deficiency problem was resolved by assembling an augmented column-wise matrix. HPLC was employed to separate the original and byproducts degradation components. Aiming the same goal, multivariate curve resolution - alternating least squares (MCR-ALS) was applied to resolve the UV spectroscopic data. Comparison between HPLC and MCR-ALS separations is presented. By using MCR-ALS the spectra of atrazine and two byproducts were successfully resolved and the resulted concentration profiles properly represented the system studied. The ALS explained variance (R2) for PA, PB and PC was equal to 99.99% for all of them and the lack of fit for PA, PB and PC were 0.39, 0.34 and 0.54 respectively. The correlation (R) between the recovered and pure spectra were calculate for each electrodegradation, validating the MCR-ALS results. The average R was equal to 0.997. The spectral and concentration profiles described with this new approach are in agreement with HPLC-DAD results. The proposed method is an alternative to classical analyses for monitoring of the degradation process, mainly due to the simplicity, fast results and economy.

Loss of N through volatilization of ammonia is the main limitation for agricultural use of urea. The aim of this study was to evaluate the volatilization of NH3 from urea granulated (Ug) or urea coated (Ur) with two oxidized charcoals produced by the oxidation of eucalyptus charcoal with 4.0 mol L-1 HNO3, followed by the post-treatment with NaOH (CHox) or without post-treatment with NaOH (CHox-OH). Ug and Ur were produced with 5, 10, 15 and 20% (m/m) of CHox or CHox-OH. The volatilization of NH3 was evaluated as 100 mg of N in the form of Ug or Ur applied to samples of a Hapludalf placed in a system with continuous and controlled air flow. The Ug with CHox-OH or with CHox was more effective in reducing the volatilization of NH3 than the Ur. It was estimated that the Ug with 16% of CHox or CHox-OH, with 39% N, reduced the volatilization by 40% in relation to urea without the additives. Results show that charcoal oxidized is an effective additive for reducing ammonia volatilization of urea.

Mabea fistulifera Mart. (Euphorbiaceae) é uma planta arbórea com altura variando de 5 a 14 m, típica da vegetação secundária de terrenos arenosos, principalmente de savana. No Brasil, é encontrada nos estados do Rio de Janeiro, Minas Gerais e São Paulo. O processo de extração Soxhlet das sementes desta espécie vegetal com hexano produziu um óleo rico em triacilglicerídeos dos ácidos linolênico e linoléico e que apresenta índice de iodo igual a 182,15 g de I2 per 100 g de óleo. Descreve-se neste trabalho a produção de um biopoliol a partir do óleo de M. fistulifera Mart., empregando-se um processo de hidroxilação in situ. Ensaios univariados permitiram determinar o tempo ótimo de reação como sendo 720 min. Além disso, realizou-se ainda um planejamento fatorial 2² composto central (CCD) contendo 12 ensaios experimentais que permitiram investigar diferentes razões molares dos reagentes empregados na síntese do biopoliol, bem como avaliar sua aplicabilidade como matéria-prima na síntese de poliuretanos com característica rígida.

Mabea fistulifera Mart. (Euphorbiaceae) is an arboreal plant with height varying from 5 to 14 m, typical of secondary vegetation of sandy lands, mainly savannah. In Brazil, it is found in the Rio de Janeiro, Minas Gerais and São Paulo States. Soxhlet extraction of M. fistulifera seeds with hexane provided an oil rich in tryacylglycerides of linolenic and linoleic acids, presenting iodine index of 182.15 g of I2 per 100 g of oil. In this study, the synthesis of polyols from M. fistulifera oil using an in situ hydroxylation procedure is described. Univariate assays were applied to determine the optimal reaction time of 720 min. In addition, a 2² factorial central composite design was carried out containing 12 experimental assays that allowed the investigation of different molar ratios of the reagents used in polyol synthesis, as well as the applicability of polyols for the preparation of rigid polyurethanes.

A voltammetric procedure optimized by experimental design for glyphosate determination in soil, water and vegetable samples is described. The voltammetry experiments were performed using a hanging mercury drop electrode (HMDE). The DPV variables involved in the optimization process were: voltage step, pulse amplitude, pulse interval, voltage step time and concentration of the supporting electrolyte. A full 2(5) factorial design was chosen to evaluate these effects. From the results obtained by the factorial design the three most important factors were determined. These variables were evaluated with a central composite design. Under the optimized conditions, the operational range was from 0.050 to 100.0 mg dm-3 and the detection and quantification limits were 14 and 48 µg dm-3, respectively. The optimized method was successfully applied to glyphosate determination in soil, water and vegetables after purifying with an ion exchange resin and derivation.

A corrente de pico de redução do derivativo N-nitroso do herbicida glifosato foi otimizada por planejamentos experimentais, para sua determinação. As variáveis envolvidas na otimização da voltametria de onda quadrada (SWV) foram: incremento de voltagem, amplitude, freqüência, concentração do eletrólito de suporte e a área da gota de mercúrio. Um planejamento fatorial completo 2(5) foi usado para avaliar os efeitos das variáveis. Dos resultados obtidos foram escolhidos três dos fatores mais importantes. Estas variáveis foram estudadas com o planejamento composto central. As condições que proporcionaram a melhor resposta voltamétrica foram: 0,025 volt, 0,125 volt, 70 Hz, 1,25 mol L-1 e 0,60 mm² para o incremento de voltagem, amplitude, freqüência, concentração do eletrólito e área da gota de mercúrio, respectivamente. Nestas condições a faixa operacional foi de 0,050 a 100,0 µg mL-1, os limites de detecção e quantificação foram de 0,025 e 0,080 µg mL-1, respectivamente.

The reduction peak current of the derivative N-nitroso of glyphosate herbicide was optimized by experimental design for their determination. The variables involved in the optimization of the square wave voltammetry (SWV) were: voltage step, amplitude, frequency, concentration of the supporting electrolyte and the area of the mercury drop electrode. A complete 2(5) factorial design was used to evaluate the effects of the variables. From the results obtained by the factorial design was set the three more important factors. These variables were evaluated with a central composite design. The conditions that proportionate the best voltammetric response were: 0.025 volt, 0.125 volt, 70 Hz, 1.25 mol L-1 e 0.60 mm² for step voltage, amplitude, frequency, electrolyte concentration and area of the mercury drop, respectively. In these conditions the operational range was from 0.050 up to 100.0 µg mL-1, the detection and quantification limits were 0.025 and 0.080 µg mL-1, respectively.

Em razão das poucas de informações existente na literatura, sobre a mobilidade do glyphosate e do imazapyr, em solos de baixa atividade, comum em países tropicais, foi conduzido, em laboratório, um estudo sobre a mobilidade vertical desses herbicida s em dois solos com diferente s composições químicas e fisicas. Para estudar essa mobilidade, foram utilizadas colunas de solo com diferentes alturas, as quais, após aplicação dos produtos na dose comerc ial de 4 L ha-1, foram submetida s a um regime hídrico de 40 mm h-1, por um período de 4 h. As análises dos resíduos nas diferentes profundidades foram feitas utilizando-se os métodos voltamétrico (polarografia) e HPLC, para o glyphosate e imazapyr, respectivame nte. Com base nos resultados, foi possível concluir que: a) os métodos voltamétrico, para o glyphosate, e HPLC, para o imazapyr, são adequados para os estudos de identificação e quantificação de resíduos em água e solo; b) os limites de quantificação dos resíduos foram de 0,4 μg mL-1 e 5 μg L-1 para o glyphosate e o imazapyr, respectivamente; c) a taxa de recuperação do glyphosate, nas amostr as de solo (76 e 78% para os solos de Viçosa e Sabará, respectivamente) foi menor que na amostra de água (83%); d) a taxa de recuperação do imazapyr, em água e solo, foi próxima de 100%; e) a lixiviação do glyphosate nos solos foi muito baixa; e f) o imazapyr apresentou alta lix iviação, porém dif ere nciada entre os solos estudados, sendo essa maior no solo de tex tura franco -are nosa de Viçosa que no de argila de Sabará.

Due to the scarce information available in the lit eratu re on the glyphosa te and imazapyr mobility in low activity soils, which is common in the tropical countries, a laboratory study was conducted on the vertical mobility of these herbicides in two soils with different physical and chemical compositions . For studying this mobility, the soil columns with different heights were submitted to a water flux of 40 mm h-1 over a 4 h period after the product applications in a commer ci al d os ag e of 4 L ha -1. The residue analyses at different depths were realized by the voltametric (polarographic) and HPLC methods for glyphosate and imazapyr respect ively. Based on the results it was possible to conclud e that: a) the voltametric method for glyphosat e and the HPLC for imazapyr are both adequate for st udying the identification and quantification of residues in water and soil; b) the boundaries of residue quantification were 0.4 μg mL-1 and 5 μg L-1 fo r glyphosa te and imaza pyrrespectively; c) the glyphosate recuperation rate in the soil samples (76 and 78% for Viçosa and Sabará soi ls, res pectively) was lower th an in the wat er sampl e (83%); d) the imazapyr recuperation rate in water and soil was about 100%; e) the glyphosate leaching in the studied soils was very low;f) the imazapyr presented high leaching although differentiate between the studied soil s being highe r in th e sandy loam texture soil of Viçosa than in the one of clay in Sabará.