ABSTRACT In this work, numerical approximations for solving the one dimensional Smoluchowski coagulation equation on non-uniform meshes has been analyzed. Among the various available numerical methods, finite volume and sectional methods have explicit advantage such as mass conservation and an accurate prediction of different order moments. Here, a recently developed efficient finite volume scheme (Singh et al., 2015) and the cell average technique (Kumar et al., 2006) are compared. The numerical comparison is established for both analytically tractable as well as physically relevant kernels. It is concluded that the finite volume scheme predicts both number density as well as different order moments with higher accuracy than the cell average technique. Moreover, the finite volume scheme is computationally less expensive than the cell average technique.

Extração líquido-líquido de zircônio e háfnio tetravalentes, a partir de soluções de ácido clorídrico, foi investigada usando-se 3-fenil-4-acil-5-isoxazolonas em xileno, tais como 3-fenil-4-benzoil-5-isoxazolonas (HPBI), 3-fenil-4-(4-fluorobenzoil)-5-isoxazolona (HFBPI) e 3-fenil-4-(4-toluoil)-5-isoxazolona (HTPI). A extração de zircônio(IV) / háfnio(IV) mostrou um mecanismo de troca iônica: MO2+ (aq) + 2 HA (org) <FONT FACE=Symbol>«</FONT> MOA2 (org) + 2 H+(aq), onde M = Zr(IV) / Hf(IV) e HA = HPBI ou HFBPI ou HTPI. A variação dos valores D (razão [MOA2] (org) / [MO2+](aq); prováveis espécies em equilíbrio durante a extração) com o aumento da concentração ácido/extrator mostrou um gráfico linear com inclinação 2. O efeito da natureza dos diluentes, como tetracloreto de carbono, ciclohexano, n-hexano, benzeno, nitrobenzeno, xileno, tolueno e clorofórmio na extração de zirônio(IV) / háfnio(IV) foi estudado. O comportamento da extração de zircônio(IV) / háfnio(IV) foi também comparado com o de outros íons metálicos, como titânio(IV), alumínio(III) e ferro(III), e pode, genericamente, ser aplicado aos íons metálicos estudados.

Liquid liquid extraction of tetravalent zirconium and hafnium from acidic chloride solutions has been investigated using 3-phenyl-4-acyl-5-isoxazolones in xylene such as 3-phenyl-4-benzoyl-5-isoxazolones (HPBI), 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone (HFBPI) and 3-phenyl-4-(4-toluoyl)-5-isoxazolone (HTPI). The extraction of zirconium(IV) / hafnium(IV) shows a ion exchange mechanism: MO2+ (aq) + 2 HA (org) <FONT FACE=Symbol>«</FONT> MOA2 (org) + 2 H+(aq), where M = Zr(IV) / Hf(IV) and HA = HPBI or HFBPI or HTPI. The variation of the D ([MOA2] (org) / [MO2+](aq); ratio of the possible extraction equilibrium species) values with an increase of the acid / extractant concentration showed a linear plot with a slope of 2. The effect of the nature of the diluents like carbon tetrachloride, cyclohexane, n-hexane, benzene, nitrobenzene, xylene, toluene and chloroform on the extraction of zirconium(IV) / hafnium(IV) has been studied. The extraction behavior of zirconium(IV) / hafnium(IV) was also compared with that of other metal ions like titanium(IV), aluminium(III) and iron(III), which can be generally associated with the metal ions studied.

Piridoxal-4-fenil-3-tiossemicarbazona (PPT) é proposto como um novo reagente sensível para a determinação espectrofotométrica de zinco(II). PPT reage com zinco(II) no intervalo de pH entre 5,0 e 6,0, para formar um complexo colorido amarelo, o qual foi adequadamente extraído em n-butanol. A absorbância do complexo Zn(II)-PPT foi medida em diferentes intervalos de tempo, a 430 nm, para averiguar a estabilidade do complexo. Foi observado que o desenvolvimento da cor foi instantâneo e estável por mais de 48 h. O sistema obedece a lei de Beer até 6,0 µg mL-1 de zinco(II), com uma excelente linearidade em termos do valor do coeficiente de correlação, de 0,999. A absortividade molar e sensitividade de Sandell da espécie extraída é 1,6 X 10(4) L mol-1 cm-1 e 4,085 X 10-3 µg cm-2, respectivamente, a 430 nm. O limite de detecção do método é 0,04 µg mL-1. Para avaliar a precisão do método, determinações foram efetuadas em diferentes concentrações; o desvio padrão relativo não excedeu 3,1%. A composição do complexo de zinco(II) com PPT foi estudada pelos métodos de variação contínua de Job, da razão molar, método de Asmus e da razão da inclinação. PPT tem sido empregado satisfatoriamente para a determinação de zinco(II) isoladamente, ou na presença de outros íons, normalmente associados ao zinco(II) em amostras farmacêuticas e biológicas. Vários materiais de referência (NIST 1573, NBS 1572 e NIST SRM 8435) têm sido testados para a determinação de zinco, com o propósito de avaliar a exatidão do presente método. Os resultados do método proposto são concordantes com os obtidos por espectrometria de absorção atômica com chama.

Pyridoxal-4-phenyl-3-thiosemicarbazone (PPT) is proposed as a new sensitive reagent for the sensitive extractive spectrophotometric determination of zinc(II). PPT reacts with zinc(II) in the pH range 5.0-6.0 to form a yellow colored complex, which was well extracted into n-butanol. The absorbance value of Zn(II)-PPT complex was measured at different intervals of time at 430 nm, to ascertain the stability of the complex. It was observed that the color development was instantaneous and stable for more than 48 h. The system obeyed Beer's law up to 6.0 µg mL-1 of zinc(II), with an excellent linearity in terms of correlation coefficient value of 0.999. The molar absorptivity and Sandell's sensitivity of the extracted species is 1.6 X 10(4) L mol-1 cm-1 and 4.085 X 10-3 µg cm-2 at 430 nm. The detection limit of the method is 0.04 µg mL-1. To assess precision of the method, determinations were carried out at different concentrations; the relative standard deviation does not exceed 3.1%. The composition of the zinc(II) complex with PPT was studied by the method of Job's continuous variation, molar ratio method, Asmus' method and slope ratio method. It has been satisfactorily applied for the determination of zinc(II), when present alone or in presence of diverse ions, which are usually associated with zinc(II) in pharmaceutical and biological samples. Various certified reference materials (NIST 1573, NBS 1572 and NIST SRM 8435) have been tested for the determination of zinc for evaluating the accuracy of the developed method. The results of the proposed method are in agreement with flame atomic absorption spectometry.

In this paper a model for fluidized bed spray agglomeration is presented. To describe the processes of heat and mass transfer, a physical based model is derived. The model takes evaporation process from the wetted particles as well as the effects of transfer phenomena between suspension gas and bypass gas into account. The change of particle size distribution during agglomeration, modeled by population balances, is linked to the heat and mass transfer model. A new technique is derived to extract agglomeration and nucleation rates from experimental data. Comparisons of experiments and simulations are presented.