[13] H.Y. Sohn, and M.E. Wadsworth, Cinética de los procesos de metalurgia extractiva, Edited by Trillas, Mexico City, Mexico, , p [14] A.R. Geyne, C. 1 Centro de Investigaciones en Materiales y Metalurgia, Universidad Sohn, H. Y.; Wadsworth, M. E., Cinética de los Procesos de la Metalurgia Extractiva, Ed. 3Instituto de Metalurgia, Universidad Autónoma de San Luis Potosí, Av. Sierra .. [12] A. Ballester, L.F. Verdeja, and J. Sancho, Metalurgia Extractiva, Vol. 1, [13] H.Y. Sohn, and M.E. Wadsworth, Cinética de los procesos de metalurgia.

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Therefore, jarosites containing arsenic have an environmental importance, not only as a means to control the As in water, but it is also well known that the hydrometallurgical industries, mainly the zinc industry, use jarosite precipitation as a means to control iron, sulfates and alkaline metals among others. There are no morphological changes or formation of any detectable solid layer at practical resolution levels of the EDS technique ca.

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Introduction The arsenic pollution of water is considered a problem of catastrophic proportions. Besides, in both media, t ind is independent from the particle size Figure 9which confirms that the activation process is a phenomenon occurring at levels of molecular thickness, involving only the initial surface.

The solid residues are amorphous, and do not evolve into crystal phases under the conditions of alkaline decomposition herein studied as observed in Figure 4. Vice Presidente abasagoi adsl.

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Arsenic incorporated in the structure could influence the solubility of jarosite, potentially stabilizing the structure under a extracitva range of conditions that are tolerated by the pure jarosite.

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The objective of this article is to present a detailed kinetic study on the alkaline reactivity in NaOH and CaO media of the sodium jarosite with arsenic in order to provide information regarding the stability of these compounds in these kind of media, because, as previously mentioned, jarosites are very stable in acidic media.

It was proved that surface attack of the arsenical jarosite with HCl a way to create surface defects or to l submicron films reduces the induction period. For these analyses, standards with an identical matrix were used. The alkaline decomposition of the arsenical natrojarosite is characterized by the removal of sulfate and sodium ions from the lattice and their diffusion to the solution, ds a gel of iron hydroxide with adsorbed arsenate is formed.

oa In Ca OH 2 medium, the reaction order was of 1. Horacio Aros Meneses Rate experimental constant values corrected by the size factor are shown in Table 1. Arsenical natrojarosite was used for the reactivity study. Recently, it has been drawn attention to the jarosite-type compounds as a means to control the arsenic in water.

This induction period exponentially decreases as the temperature rises, and was independent of the initial particle size in the studied range. SEM analysis indicated the formation of a reaction front. Therefore, ols reaction takes place only in the interface Figure 5aand that is the reason why the kinetics have been described by separating the induction period from the conversion period.

The kinetic expression of the arsenical natrojarosite decomposition in NaOH medium for [OH – ] concentrations ranging from 3. For [OH – ] concentrations below 2. Manuel Soto vice presidente. Alkaline reactivity is characterized by the removal of sulfate and sodium ions clnetica the lattice and by the formation of a gel consisting of iron hydroxides with adsorbed arsenate.

R; Handbook of Chemistry and Physics89 th ed. Carlos Carlesi Jara Jefe de Docencia. The values of the induction times t ind were obtained from the intersections of the regression straight line with the time axis. In order to study the stoichiometry of the reaction, samples of arsenical natrojarosite were treated for long periods with NaOH and Ca OH 2. The conversion period is characterized by the formation of a reaction front with an unreacted arsenical natrojarosite core and a gel halo of iron hydroxide with adsorbed arsenate.

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However, since it is a common phenomenon in the decomposition of this type of compounds, the induction period has not been eliminated in this research work, and its dependence on OH – concentration, temperature and particle size have been determined. In NaOH medium, the decomposition of the arsenical natrojarosite is of a fractional order of 0.

Millions of people who have been exposed to high concentrations of arsenic through potable water have developed serious health problems. During the induction period, there are no morphological changes or formation of any detectable solid layer at practical resolution levels of the EDS technique ca.

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Soils Sediments5 Activity coefficients of NaBF 4 in aqueous solution. Temperature effect indicates an activation energy of A plot of the rate experimental constants determined at constant temperature and concentration vs. The arsenic pollution of water is considered a problem of catastrophic proportions. Experimental Materials Arsenical natrojarosite was used for the reactivity study.