Fotocatálise eletroquímica de atrazina sobre dióxido de titânio: efeito de diferentes parâmetros experimentais

The atrazine photoelectrochemical degradation has been examined in solutions containing TiO2 on immobilized films under a variety of experimental conditions. It was possible to observe that the supporting electrolyte nature affects the intensity of the photocurrent, being an indicative of the adsorption process. The disappearance of the organic molecule follows approximately a pseudo-first order kinetic. As mineralization product, NH4+ and NO3- ion have been identified. These results indicated that the formation of NH4+ ion can be associated to the effect of atrazine adsorption, due to need of potential adaptation together with a variation in the supporting electrolyte concentration.

Factors affecting Hg (II) adsorption in soils from the Rio Negro basin (Amazon)

Mercury (II) adsorption studies in top soils (top 10 cm) from the Rio Negro basin show this process depends strongly on some selected parameters of the aqueous phase in contact with the soils. Maximum adsorption occurred in the pH range 3.0-5.0 (>90%). Dissolved organic matter shows an inhibitory effect on the availability of Hg (II) to be adsorbed by the soils, whereas a higher chloride content of the solution resulted in a lower adsorption of Hg (II) at pH 5.0. Soils with higher organic matter content were less affected by changes in the salinity. An increase in the initial Hg (II) concentration increased the amount of Hg (II) adsorbed by the soil and decreased the time needed to reach equilibrium. A Freundlich isotherm provided a good model for Hg (II) adsorption in the two types of soil studied. The kinetics of Hg (II) adsorption on Amazonian soils showed to be very fast and followed pseudo-second order kinetics. An environmental implication of these results is discussed under the real scenario present in the Negro River basin, where acidic waters are in contact with a soil naturally rich in mercury.

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.

Indirect likelihood inference (revised)

Standard indirect Inference (II) estimators take a given finite-dimensional statistic, Z_{n} , and then estimate the parameters by matching the sample statistic with the model-implied population moment. We here propose a novel estimation method that utilizes all available information contained in the distribution of Z_{n} , not just its first moment. This is done by computing the likelihood of Z_{n}, and then estimating the parameters by either maximizing the likelihood or computing the posterior mean for a given prior of the parameters. These are referred to as the maximum indirect likelihood (MIL) and Bayesian Indirect Likelihood (BIL) estimators, respectively. We show that the IL estimators are first-order equivalent to the corresponding moment-based II estimator that employs the optimal weighting matrix. However, due to higher-order features of Z_{n} , the IL estimators are higher order efficient relative to the standard II estimator. The likelihood of Z_{n} will in general be unknown and so simulated versions of IL estimators are developed. Monte Carlo results for a structural auction model and a DSGE model show that the proposed estimators indeed have attractive finite sample properties.

Validation of an instrument to evaluate quality of life in the aging population: WHOQOL-AGE.

BACKGROUND: There is a need for short, specific instruments that assess quality of life (QOL) adequately in the older adult population. The aims of the present study were to obtain evidence on the validity of the inferences that could be drawn from an instrument to measure QOL in the aging population (people 50+ years old), and to test its psychometric properties. METHODS: The instrument, WHOQOL-AGE, comprised 13 positive items, assessed on a five-point rating scale, and was administered to nationally representative samples (n = 9987) from Finland, Poland, and Spain. Cronbach's alpha was employed to assess internal consistency reliability, whereas the validity of the questionnaire was assessed by means of factor analysis, graded response model, Pearson's correlation coefficient and unpaired t-test. Normative values were calculated across countries and for different age groups. RESULTS: The satisfactory goodness-of-fit indices confirmed that the factorial structure of WHOQOL-AGE comprises two first-order factors. Cronbach's alpha was 0.88 for factor 1, and 0.84 for factor 2. Evidence supporting a global score was found with a second-order factor model, according to the goodness-of-fit indices: CFI = 0.93, TLI = 0.91, RMSEA = 0.073. Convergent validity was estimated at r = 0.75 and adequate discriminant validity was also found. Significant differences were found between healthy individuals (74.19 ± 13.21) and individuals with at least one chronic condition (64.29 ± 16.29), supporting adequate known-groups validity. CONCLUSIONS: WHOQOL-AGE has shown good psychometric properties in Finland, Poland, and Spain. Therefore, considerable support is provided to using the WHOQOL-AGE to measure QOL in older adults in these countries, and to compare the QOL of older and younger adults.

Efeitos dos parâmetros operacionais na fotodegradação do azo corante direct red 23 na interface dióxido de titânio/água

The decolorization and degradation of direct red 23 azo dye have been investigated in aqueous suspension of titanium dioxide under artificial irradiation. The effects of some operational parameters such as azo dye concentration, catalyst loading, and solution pH were investigated at 30.0 ºC and optimized values were obtained. The first-order kinetic model was used to discuss the results. The UV-Vis spectra changes showed that the azo dye sample, collected after 6 h irradiation, was 98% decolorized while the residual total carbon was 97.9% degraded, indicating simultaneous photodecolorization and degradation.

Degradação de corantes ácidos por processos oxidativos avançados usando um reator com disco rotatório de baixa velocidade

Three technologies were tested (TiO2/UV, H2O2/UV, and TiO2/H2O2/UV) for the degradation and color removal of a 25 mg L-1 mixture of three acid dyes: Blue 9, Red 18, and Yellow 23. A low speed rotating disc reactor (20 rpm) and a H2O2 concentration of 2.5 mmol L-1 were used. The dyes did not significantly undergo photolysis, although they were all degraded by the studied advanced oxidation processes. With the TiO2/H2O2/UV process, a strong synergism was observed (color removal reached 100%). Pseudo first order kinetic constants were estimated for all processes, as well as the respective apparent photonic efficiencies.

Extracción y medida de peroxidasa en pulpa de arazá (Eugenia stipitata MC Vaugh)

A technique for both extraction and activity measurement of peroxidase extracted from arazá (Eugenia stipitata Mc Vaugh) is described. Peroxidase from arazá pulp fruit was extracted using a combination of protein precipitation with acetone and extraction with 50 mM sodium buffer phosphate (pH 6.0). Optimum activity using guaiacol as H-donor was obtained at pH from 5.0 to 6.5, temperature from 60 to 75 °C, H2O2 between 10 to 15 mM and guaiacol from 80 to 160 mM. Thermal inactivation showed a first-order inactivation kinetic. Reactivation was observed when extracts were heated at 80 °C and afterwards incubated at 25 °C.

Estudio cinético de la descomposición catalizada de peróxido de hidrógeno sobre carbón activado

The kinetic study of decomposition of hydrogen peroxide catalyzed by activated carbon was carried out. The effect of concentrations of reactants and temperature were experimentally studied. Kinetic data were evaluated using differential method of initial rates of reaction. When a typical kinetic law for reactions in homogeneous phase is used, first order of reaction is obtained for hydrogen peroxide and activated carbon, and activation energy of 27 kJ mol-1 for the reaction was estimated. Experimentally was observed that surface of activated carbon is chemically modified during decomposition of hydrogen peroxide, based on this result a scheme of reaction was proposed and evaluated. Experimental data fits very well to a Langmuir- Hinshelwood kinetic model and activation energy of 40 kJ mol-1 was estimated for reaction in heterogeneous phase.

Estado da arte de figuras de mérito em calibração multivariada

The validation of an analytical procedure must be certified through the determination of parameters known as figures of merit. For first order data, the acuracy, precision, robustness and bias is similar to the methods of univariate calibration. Linearity, sensitivity, signal to noise ratio, adjustment, selectivity and confidence intervals need different approaches, specific for multivariate data. Selectivity and signal to noise ratio are more critical and they only can be estimated by means of the calculation of the net analyte signal. In second order calibration, some differentes approaches are necessary due to data structure.

Biomassa residual para remoção de íons uranilo

Activities related to nuclear industry, production of phosphoric acid and hospitals have generated considerable volumes of radioactive waste containing uranyl ions. Banana pith was characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy and was investigated as a biosorbent for uranyl ions from nitric solutions by batch experiments. Influences of adsorbent size, kinetics and equilibrium adsorption were studied. The biosorption of the uranyl ions followed pseudo-second-order kinetics. The adsorption isotherm data were closely fitted to the Freundlich equation.

UV derivative spectrophotometric method for determination of estradiol valerate in tablets

A derivative UV spectrophotometric method for determination of estradiol valerate in tablets was validated. The parameters specificity, linearity, precision, accuracy, limit of detection and limit of quantitation were studied according to validation guidelines. The first-order derivative spectra were obtained at N = 5, Δλ = 4.0 nm, and determinations were made at 270 nm. The method showed specificity and linearity in the concentration range of 0.20 to 0.40 mg mL-1. The intra and interday precision data demonstrated the method has good reproducibility. Accuracy was also evaluated and results were satisfactory. The proposed method was successfully applied to a pharmaceutical formulation.

Cloreto de n-(2-hidroxil) propil-3-trimetil amônio quitosana como adsorvente de corantes reativos em solução aquosa

The quaternary chitosan was synthesized by reaction of chitosan with glycidyl trimethylammonium chloride. it was characterized by infrared spectra and conductometric titration. Adsorption of reactive blue 4 (RB4) and reactive red 120 (RR120) by quaternary chitosan was studied from aqueous medium. Two kinetic adsorption models were tested: pseudo first-order and pseudo second-order. The experimental data best fitted the pseudo second-order model. The Langmuir isotherm model provided the best fit to the equilibrium data in the concentration range investigated and the maximum adsorption capacity determined was 415 mg (RR120) and 637 mg (RB4) of reactive dye per gram of adsorbent.

Adsorção do corante vermelho congo por derivados da o-carboximetilquitosana hidrofobicamente modificados

Hydrophobically modified O-carboxymethylchitosan derivatives were synthesized through a reaction with lauroyl chloride and applied for adsorption of congo red dye. The Langmuir-Freundlich isotherm model was found to be the most suitable one for the VC adsorption and maximum adsorption capacity obtained was 281.97 mg g-1 at a pH value of 7.0 for HL 1.0. The adsorption process follows the pseudo-second-order kinetics and the corresponding rate constants were obtained. The thermodynamic parameters showed that adsorption process is spontaneous (positive ∆Hº) and favorable (negative ∆Gº). The hydrophobic derivatives are able to adsorb the dye even in high pH values.

Fe (ii) adsorption on Ucides Cordatus crab shells

In this study Ucides cordatus crab shells were utilized as Fe (II) sorbent as material of low cost and simple preparation. Values of pH of standard solution, biosorbent mass, particles size, contact time (t c) and initial concentration of the standard solution were optimized. The best conditions were pH = 2.00, t c = 840 min and Mc = 0.25 g. The kinetic pseudo first-order model displayed the best description of the adsorption process and the equilibrium study showed that the Langmuir model better describes the adsorption of the Fe (II). There is great affinity between the Fe (II) and the biosorbent.