Non-dispersive selective extraction of Ge(IV) tartrates was carried out from simulated fly ash solutions containing heavy metals through supported liquid membranes (SLM). The optimum transport was ...obtained using a PTFE membrane containing Alamine 336 5%v/v in the condition of tartaric acid 2.76 mmol/L and HCl 1 mol/L in feed and strip phases, respectively. Under this condition, a hollow fiber (HF) SLM experiment was conducted. The results showed that this system could transport germanium from the feed to the strip phase so much faster than the flat sheet (FS) SLM system. The rate of transport through HFSLMs is comparable to dispersive extractions.
Abbreviation: A: Effective area of the membrane (cm
2
); BDL: Below detection limit; C
f
,: Feed concentration (mg/L); C
t
,: Initial concentration (mg/L); D: Distribution coefficient; ELM: Emulasion liquid membranes; FSSLM: Flat sheet supported liquid membrane; HF: Hollow fiber; LLX: Liquid-liquid extraction; P: Permeation coefficient (m/h); PTFE: Poly tetra fluoro ethylene; PVDF: Polyvinylidene difluoride; T: Tartrate species (C
4
H
4
O
6
); T: Temperature (K); %T:Germanium transport effeciency; V: Volume of feed solution (cm
3
); t: time (h); η: Viscosity (P.s (c.P)); κ: Boltzmann constant; r: Ionic radius of species; τ: Tortuosity of the membrane; ρ: Porosity; α: Separation factor.
Transport process of germanium from an aqueous solution containing oxalic acid and 100 mg/L Ge was studied. Cyanex 923 immobilized in a polytetrafluoroethylene membrane was employed as a carrier in a ...flat-sheet supported liquid membrane (FSSLM) system. The speciation of the germanium ion in the oxalic acid medium and related diagrams were applied to study the transport of germanium. The effective parameters such as oxalic acid, carrier concentration, and strip reagent composition were evaluated in this study. Based on the experimental data, the oxalic acid and carrier concentrations of 0.075 mol/L and 20% v/v were the condition in which the efficient germanium transport was achieved, respectively. The concentration range of 0.04–0.1 mol/L was selected for sodium hydroxide (NaOH) as a strip reagent providing the best efficiency to transport germanium through the supported liquid membrane (SLM) system. Furthermore, the permeation model was obtained to calculate the mass transfer resistance of the membrane (Δm) and feed (Δf) phases. According to the results, the values of 1 and 1345 s/cm were found for Δm and Δf, respectively.
A new method for the site-selective synthesis of nanowires has been developed to enable material growth with defined morphology and at the same time different composition on the same chip surface. ...The chemical vapour deposition approach for the growth of these nanowire-based resistive devices using micromembranes can be easily modified and represents a simple, adjustable fabrica-tion process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study includes the deposition of SnO2, WO3 and Ge nanowires on the same chip. The individual resistors exhibit adequate gas sensing responses to-wards changing gas concentration of CO, NO2 and humidity diluted in synthetic air. The data have been processed by principal component analysis with cluster responses that can be easily separated and thus the devices described herein are in principle suita-ble for environmental monitoring.
In this work, the mathematical modeling of the facilitated transport of germanium (non-dispersive extraction) through a flat sheet membrane with an Aliquat 336 carrier was described. The flat sheet ...supported liquid membrane (FSSLM) experiments were performed under conditions germanium ≈ 100 mg/L, tartaric acid concentration of 2.76 mmol/L, and carrier concentrations of 2.5-10%v/v. The extraction equilibrium, mass transfer, and diffusion equations based on Fick's law were the principles of modeling. Modeling was carried out by programming in Matlab mathematical software to obtain the extraction (K
) and mass transfer constants (K
) as the objective parameters. According to the model resolution, K
and K
were found to be 0.178 and 9.25 × 10
cm/s, respectively. The correlation coefficients between model and experimental data relating to the Aliquat 336 concentrations of 2.5, 5, 7.5, and 10%v/v were found as 0.96, 0.98, 0.99, and 0.92. The parameters of root mean square error, bias, and scatter index showed the model accuracy. In addition, diffusion coefficients relating to Aliquat 336 concentrations of 2.5, 5, 7.5, and 10%v/v were calculated using mass transfer coefficients to be 2.4 × 10
, 2.23 × 10
, 1.91 × 10
, and 1.79 × 10
cm
/s, respectively.
A mathematical model was developed to monitor the facilitated transport of germanium(IV) from oxalic acid solutions through a flat sheet supported liquid membrane (FSSLM) containing four ...trialkylphosphine oxides (Cyanex 923). The FSSLM modeling was based on the extraction constant (Kext) calculated from the liquid−liquid extraction (LLX) modeling. The LLX model presented a reliable calculation of the extraction constant (Kex= 2.057×103 L/mol4). The FSSLM model was solved using Matlab® software according to extraction constant, Fick's law, and diffusional principles. The model predicts the overall mass transfer coefficient (Korg) to be 3.84 cm/s. Using this value, diffusion coefficients (Dm) for various Cyanex 923 concentrations of 0.126, 0.252, 0.378, 0.505, 0.631 and 0.757 mol/L are found to be 8.50×10−4, 4.30×10−4, 1.87×10−4, 5.87×10−5, 2.57×10−5, 2.09×10−5 cm2/s, respectively. The results show that the diffusion rate of the current study is approximately more than that of similar FSSLM systems containing Cyanex 923 used to transport various metals. The modeling values are in good agreement with the experimental data, showing the good reliability of the mathematical model.
El objetivo de este trabajo es ofrecer un perfil unitario del pensamiento de Gino Germani. Para tal fin son abordados analíticamente los temas centrales de su pensamiento y también todos aquellos ...problemas que aún hoy generan su nombre y su obra. Centrado en la problemática de la relación entre la modernidad y la secularización en sus relaciones con el autoritarismo moderno, el artículo focaliza las diferentes etapas del desarrollo de este tema en Germani, y las diversas cuestiones que se cruzan con él en varias etapas de su investigación, desde los años cuarenta del siglo XX hasta 1979, año de su muerte, y que constituyen, aún hoy, herramientas esenciales para la comprensión de la crisis contemporánea.
A mathematical model was developed for the germanium-facilitated transport from a medium containing tartaric acid using Alamine 336 as a carrier. Modeling was carried out based on the extraction ...constant (
K
ext
) obtained from the liquid–liquid extraction (LLX) modeling. The LLX data were achieved from experiments with conditions being Alamine 336 concentrations of 0.1–10% v/v from a solution containing about 1.378 mmol/L Ge (100 mg/L) and tartaric acid as an anionic complexant. The LLX model was attained using the equilibrium-based procedure and fitted to extraction experimental data for various carrier concentrations. This model presented an accurate extraction constant (
K
ext
= 0.02) used in the facilitated transport modeling. The flat sheet supported liquid membrane (FSSLM) experiments were conducted in the condition of 1.378 mmol/L Ge (100 mg/L), tartaric acid concentration of 2.760 mmol/L, 1 M HCl as a stripping phase and various Alamine 336 concentrations in the range of 0–35% v/v. The FSSLM model was developed according to the Fick’s law, the diffusional transport, and equilibrium equations. According to the model, mass transfer and diffusion coefficients for various concentrations of the carrier were found. In addition, the calculated and experimental values had a good correlation with together showing the validity of the model. This model can be used in the further process simulation such as hollow fiber SLMs.
El conocimiento sociológico es fundamental para analizar, concreta y eficazmente, los fenómenos sociales. Desde su origen, ha sido difícil lograr construir y mantener relaciones significativas entre ...el pensamiento sociológico y la autonomía de las demás ciencias. De hecho, lo que ha caracterizado a la evolución de la sociología no ha sido tanto el objeto de estudio, sino la necesidad de convertirla en autónoma. Este debate se desarrolló sobre todo en Europa y Estados Unidos, mientras que en los países de América Latina se necesitó de acciones específicas para que la sociología se desarrollara y adquiriera un papel significativo en el ámbito académico. El objetivo de este artículo de investigación es profundizar: a) en las etapas evolutivas de esta disciplina, de forma general; b) en las etapas distintivas del desarrollo de las ciencias sociales y, en particular, de la sociología en América Latina; y c) en el papel de Gino Germani para la renovación de la sociología y de las ciencias sociales en Argentina.
El presente trabajo tiene por objetivos comprender e interpretar los cambios y continuidades en la dinámica relacional entre el oficialismo peronista a cargo del Gobierno municipal y los partidos de ...la oposición entre 1946 y 1955. Al mismo tiempo, la investigación pretende analizar el tipo de relaciones entabladas entre el Estado municipal y el provincial. Al respecto cabe apuntar que dos procesos —inaugurados casi simultáneamente con el surgimiento del peronismo— influyeron fuertemente sobre las características que asumieron sus relaciones con los partidos opositores. Por una parte, el creciente cercenamiento del régimen de autonomía municipal; y por la otra, la estrecha vinculación entre el peronismo y la esfera estatal. Para llevar a cabo estos objetivos se recurrió a una metodología cualitativa, basada en la lectura y análisis de diversas fuentes (diarios locales y provinciales, documentación oficial y escritos de dirigentes peronistas). La información recopilada no fue abordada en forma aislada sino debidamente enmarcada en los procesos desarrollados a nivel provincial y nacional. La articulación de los niveles macro y micro nos permite estudiar con mayor grado de detalle los procesos políticos examinadosy complementar y matizar los estudios sobre el peronismo enfocados desde perspectivas más generales.
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