[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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The experiment for the alkaline decomposition was carried out in a conventional thermostated glass kettle with magnetic stirring. Decomposition curves The first characteristic of the kinetic curves is the presence of an induction period that increases as the extrxctiva drops, and it is generally increased as the [OH fxtractiva ] decreases. But if the arsenic is present as a separate phase, like scorodite or a similar phase, its chemical behavior will be different from that of the jarosite, and the dissolution of the arsenic will be able to occur under acidic conditions, which are common in the jarosite deposits.

The conversion period is characterized by the formation of a hydroxide halo around an unreacted arsenical natrojarosite core. Jessica Gallardo secretaria de finanzas.

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The decomposition extrachiva the arsenical natrojarosite presents an induction period and a conversion period. Arsenic integrated in the structure could influence the solubility of the jarosite, potentially stabilizing the structure under a wide range of conditions that are tolerated by pure jarosite. Activity coefficients of NaClO4 in aqueous solution.

Juan Pablo Romero delegado de proyectos.

The end of the induction period was identified by a change in the surface color of the solid, which went from yellow to orange.

Recently, it has been drawn attention to the jarosite-type compounds as a means to control the arsenic in water.

The pH of the solution was constantly measured, and the experiments were designed so that the reactant concentrations would be constantly adjusted. In NaOH medium, the decomposition of the arsenical natrojarosite is of a fractional order of 0. 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, while a gel of iron hydroxide with adsorbed arsenate is formed.


Figure 10 shows the particle size effect on the decomposition rate of the arsenical natrojarosite.

Kinetic Modeling of the Alkaline Decomposition and Cyanidation of Argentojarosite

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. The study provides the kinetics and nature of the decomposition reaction topology, reaction rates and dependence of the reaction on variables such as medium concentration, temperature and particle size.

The first characteristic of the kinetic curves is the presence of an induction period that increases as the temperature drops, and it is generally increased as the [OH – ] decreases.

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.

Madrid,chapter 2. 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.

Catalina Vargas vice presidenta. According to the previously stated, the stoichiometry of the process can be expressed according to the following reaction: The concentration of sulfates and sodium progressively increases, while simultaneously, the reflection intensities of the arsenical natrojarosite decrease until disappearing. Acta70 Dependence of the conversion period. Vice Presidente abasagoi adsl. The model selected for the conversion period was the model of decreasing core and chemical control, which, for particles, takes the following expression: 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.


Oscar Jaime Restrepo Baena

N-methylformamide-water mixtures at A point rarely discussed in literature, but important when interpreting a kinetic study, regards morphology and particle size.

In addition, these results rule out the control by transport through the layer of the ciinetica.

Thomas Acevedo Departamento de deportes. The kinetic data are consistent with the chemical control of the process. Several impurities, like lead, iron and selenium, are often mixed with the arsenic wastes, becoming more difficult the removal. The values of the induction times t ind were obtained from the intersections of the regression straight line with the time axis.

Leandro Carrizo secretario general. It seems that the arsenic contained in the natrojarosite structure studied in this work does not have a significant influence on the reaction rate compared to a natrojarosite without arsenic. Barcelona,chapter The synthesis method was selected from the works published by Dutrizac et al. Arsenic cannot be easily destroyed, and can only be changed into different forms or transformed into soluble compounds in combination with other elements, such as iron.

The WHO World Health Organization establishes, through its guidelines, that the maximum admissible content of arsenic in potable water should be reduced from 0.

Jaime Morales Saavedra – Escuela de Ingeniería Química

Horacio Soto Aguilera The solids examination by EDS after the induction period indicates the presence of a reaction front with an unreacted arsenical natrojarosite core and a gel halo of iron hydroxide with adsorbed arsenate. All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License.

The induction period is independent from the particle size and decreases exponentially as the temperature increases.