Marcelo Borges Mansur

Equilibrium analysis of the reactive liquid-liquid test system ZnSO4/D2EHPA/n-heptane

An equilibrium model is proposed for the reactive system ZnSO4/di-2-ethylhexyl phosphoric acid (D2EHPA)/diluent being considered by the European Federation of Chemical Engineering as a test system, valid over a wide concentration range of extraction and stripping conditions. The model is supported by the statistical analysis of estimated parameters. Two simple consecutive reactions are assumed to give two zinc complexes with relative proportions changing as conditions change from extraction to stripping. The model was solved by Newtons method, and all parameters were estimated by data fitting using the direct search method of Hooke and Jeaves. The model predicts aqueous concentrations with an average relative error lower than 11% by assuming activity coefficients of 1.0. The incorporation of the activity coefficients may improve the model accuracy but cannot validate other simpler extraction mechanisms.

Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

ABSTRACT The hydrodynamics of a rotating disc contactor (76.2 mm diameter, 19 stages, and operating height of 815 mm) has been investigated at limiting operational conditions of low holdup (φ ≤ 3%) and low agitation (Re R ≤ 22,000) for the water/n-heptane system in the absence of mass transfer. Water was chosen as the continuous phase, and it was kept stagnant inside the column. Local drop size distribution, local mean drop diameter, and total holdup have been measured at different flow rates of the dispersed phase (70 to 640 mL/min) and rotor speeds (0 to 700 rpm). Drop size distributions along the column were suitably described using the log-normal probability density function, and empirical expressions were derived to predict the parameters of the distribution curve as a function of operating conditions. An empirical expression was also proposed to predict the Sauter mean drop diameter along the column with a mean deviation of 3.4%. Statistical analysis has revealed no significant effect of the rotor speed on the total holdup, which changed solely with the dispersed phase flow rate for the operating conditions investigated.

Kinetic analysis of the reactive liquid-liquid test system ZnSO4/D2EHPA/n-heptane

Abstract The kinetics of zinc extraction and stripping have been investigated for the ZnSO4/D2EHPA/diluent system (D2EHPA=di(2-ethylhexyl) phosphoric acid), which is under consideration as a proposed reactive extraction liquid–liquid test system by the European Federation of Chemical Engineering. Data in low and high concentration domains have been fitted to chemical kinetic and kinetic–diffusive models in order to discern the mechanism of zinc extraction and stripping for practical operational conditions. The existence of the correlation between the estimated parameters and the contributions to the overall flux of the reactive species through the interface has been determined by statistical analysis. The study has concluded that both extraction and stripping rate processes are described by the same reaction mechanism scheme as suggested by Ajawin et al. [Chem. Eng. Res. Des. 61 (1983) 62] but with the stoichiometry and complexes proposed by Mansur et al. [Hydrometallurgy (2002)]. Flux equations lead to the calculation of the individual resistance terms for mass transfer and chemical reaction using simple equations with activity coefficients equal to unity. The extraction process shows mixed controlled kinetics, whereas the mass transfer of the zinc complex was found to be rate-determining for stripping conditions. The model satisfactorily explains the data with a relative error lower than 10%.

Submerged-arc welding slags: Characterization and leaching strategies for the removal of aluminum and titanium

In the present study, submerged-arc welding slags were characterized by applying a variety of methods, including X-ray fluorescence, X-ray diffraction, particle size, Raman spectroscopy, and scanning electron microscope with energy dispersive X-ray analysis. The content of Al proved to be quite similar within neutral and acid slags (10-14%), while that of Ti proved to be much higher in acid slags (approximately 10%) than in neutral slags (<1%). The presence of spinel structures associated with Al species could also be identified in the analyzed samples. This characterization study was accompanied by leaching tests performed under changing operating conditions in an attempt to evaluate to what extent the Al and Ti bearing components could be removed from the slags. The leaching work involved three distinct strategies: (i) NaOH leaching followed by H(2)SO(4) leaching, (ii) acid leaching (HCl and H(2)SO(4)) using oxidizing/reducing agents, and (iii) slag calcination followed by H(2)SO(4) leaching. In the best result, 80% of Al was extracted in one single leaching stage after calcination of the acid slag with NaCl+C at 900 °C. By contrast, the removal of Ti proved to be unsatisfactory.

Alternativas para o tratamento de efluentes da indústria galvânica

Os metodos de precipitacao quimica, cristalizacao e extracao liquido-liquido foram aplicados visando propor alternativas para o tratamento de efluentes liquidos gerados pela industria de galvanoplastia. Efluentes de diversas empresas do setor, localizadas no estado de Minas Gerais (Brasil), foram coletados e caracterizados. O efluente estudado, proveniente de empresa de galvanizacao de zinco a quente, continha cerca de 90 g/L de ferro total, 35 g/L de zinco e menores quantidades de Al, Ni e Cu, em meio acido cloridrico (pH = 0,6). A separacao seletiva entre ferro e zinco nao se mostrou eficiente por precipitacao, sendo a tecnica adequada somente no tratamento do efluente, ao contrario da cristalizacao e extracao liquido-liquido utilizando-se TBP como agente extratante. A integracao destas tecnicas ainda requer estudos mais detalhados visando a otimizacao de custos e das condicoes operacionais.Separation methods such as chemical precipitation, crystallization and liquid-liquid extraction have been investigated aiming to treat effluents generated by the galvanic industry. Effluent samples generated by several companies located in the state of Minas Gerais (Brazil) were collected and chemically characterized. For this work, a typical zinc hot-dip galvanizing effluent containing about 90 g/L of total iron, 35 g/L of zinc and minor amounts of Al, Ni, Cu, in HCl medium (pH = 0.6) was treated. A selective separation between metals zinc and iron was not achieved by chemical precipitation, which was found adequate to threat water only. On contrary, zinc and iron was separated very efficiently by crystallization and liquid-liquid extraction using TBP as extractant agent. The integration of these methods to recover zinc and iron from effluent still requires more detailed studies.

A moving boundary problem and orthogonal collocation in solving a dynamic liquid surfactant membrane model including osmosis and breakage

A dynamic kinetic-diffusive model for the extraction of metallic ions from aqueous liquors using liquid surfactant membranes is proposed. The model incorporates undesirable intrinsic phenomena such as swelling and breakage of the emulsion globules that have to be controlled during process operation. These phenomena change the spatial location of the chemical reaction during the course of extraction, resulting in a transient moving boundary problem. The orthogonal collocation method was used to transform the partial differential equations into an ordinary differential equation set that was solved by an implicit numerical routine. The model was found to be numerically stable and reliable in predicting the behaviour of zinc extraction with acidic extractant for long residence times.

Extração por solventes aplicada à recuperação de metais e da água a partir de resíduos industriais e efluentes líquidos

The use of solvent extraction to recover metals and water from industrial residues is highlighted in this work. The method was applied (1) to selectively concentrate Zn from effluents generated by the zinc industry, (2) to separate Zn and Fe from spent pickling effluents produced by the hot-dip galvanizing industry, and (3) to recover Co and Ni from spent batteries. Batch and pilot scale data was used to point out solvent extraction as a feasible method to reuse both metals and water thus resulting in energy savings with reducing environmental impacts, minimizing costs required to transport hazardous materials to waste sites, to replace the discharged wastewater and to produce the raw material that would be previously discharged as wastes.

Leaching of the fine fraction of the argon oxygen decarburization with lance (AOD-L) sludge for the preferential removal of iron.

The fine fraction of the argon oxygen decarburization with lance (AOD-L) sludge is a hazardous waste generated by the stainless steel industry which is normally disposed in landfills. Due to the relative high content of Fe, Cr and Ni as well as its low granulometry, a hydrometallurgical route based on sequential leaching steps is being investigated to treat it. In this paper, an attempt made to remove Fe from the sludge and concentrate Cr and Ni in the solid is highlighted. Leaching was carried out at atmospheric pressure using H(2)SO(4) and HCl at varying temperature (25, 40, 55 and 70 degrees C) and acid concentration (3, 6 and 12%, v/v). For both acids, leaching rate increased with temperature and acid concentration, and higher dissolutions of Fe and Ni were obtained in comparison with that of Cr. HCl was found more selective for Fe over Ni and Cr. The content of Fe was reduced nearly 50% (w/w) at 70 degrees C and HCl 12% (v/v), while Cr remained mostly in the solid; however, around 40% (w/w) of Ni was dissolved and it may hinder such leaching step in the studied route. The study points out that total metal leaching of sludge under high temperature and pressure conditions must be considered.

Solvent extraction of gadolinium (III) from hydrochloric acid solutions with cationic extractants D2EHPA and Ionquest 801

Abstract The solvent extraction of gadolinium (III) from hydrochloric acid solutions with cationic extractants D2EHPA and Ionquest 801 dissolved in Exxsol D100 was investigated. The study was carried out with concentrated solutions in order to better reproduce industrial process conditions. The following operational variables were investigated: initial concentration of gadolinium (16–40 g L−1, i.e., 0·104–0·255 mol L−1), initial concentration of extractant (0·5–1·5 mol L−1), initial pH of the aqueous phase (1–5) and aqueous/organic volumetric ratio (0·5–2·0). Data fitting including the statistical analysis of the estimated equilibrium parameters indicated that gadolinium (III) is extracted from hydrochloric acid solutions with D2EHPA and Ionquest 801 according to the overall reaction Gd3++3(HX)2⇆GdX3(HX)3+3H+. The apparent equilibrium constant at 298±1 K was found to be 1·9±0·3 for the system Gd(III)–D2EHPA and 0·028±0·003 for the system Gd(III)–Ionquest 801.

Elemental Analysis Of Defective And Non-Defective Beans In Green And Roasted Coffee

The study aimed at an evaluation of the mineral content of defective and non-defective coffee beans, prior to and after roasting. The types of defects studied were immature, brown (sour) and black beans. Atomic absorption analysis was performed for quantification of calcium, potassium, zinc and magnesium, prior to and after roasting. Potassium was found to be the main constituent of the ashed mineral content, and significant differences were detected among all samples. Potassium levels were the highest for black beans and the lowest for non-defective ones, prior to and after roasting. A small decrease in potassium content was observed with roasting, but differences among all samples still remained. No significant differences were found in magnesium and zinc levels.