The widespread use of jarosite-type compounds to eliminate impurities in the hydrometallurgical industry is due to their capability to incorporate several elements into their structures. Some of these elements are of environmental importance (Pb²⁺, Cr⁶⁺, As⁵⁺, Cd²⁺, Hg²⁺). For the present paper, AsO₄ ^3- was incorporated into the lattice of synthetic jarosite in order to carry out a reactivity study. Alkaline decomposition is characterized by removal of sulfate and potassium ions from the lattice and formation of a gel consisting of iron hydroxides with absorbed arsenate. Decomposition curves show an induction period followed by a conversion period. The induction period is independent of particle size and exponentially decreases with temperature. The conversion period is characterized by formation of a hydroxide halo that surrounds an unreacted jarosite core. During the conversion period in NaOH media for [OH^-] > 8 × 10^-3 mol L^-1, the process showed a reaction order of 1.86, and an apparent activation energy of 60.3 kJ mol^-1 was obtained. On the other hand, during the conversion period in Ca(OH)₂ media for [OH^-] > 1.90 × 10^-2 mol L^-1, the reaction order was 1.15, and an apparent activation energy of 74.4 kJ mol^-1 was obtained. The results are consistent with the spherical particle model with decreasing core and chemical control.

In Zimapan, Mexico abundant mineral species have been identified. However, a significant number of these precious metals appear to be related to complex sulfides, as is the case of silver (Ag) in sulfosalts. In this work, a kinetic study of the formation of Ag complexes in the AgAsS₂-S₂O₃²⁻-O₂-NaOH system from a Zn concentrate found in the Zimapan mining district was conducted. The kinetic model application on Ag leaching shows a linear adjustment in the valuation of the particle size effect. The rate of formation of Ag complexes is dependent of temperature, leaching agent concentration and OH⁻ concentration. Furthermore, graphical verification of the kinetic models indicates that the kinetics of the formation of Ag complexes correspond to the shrinking core model with chemical controls as the controlling stage. The formation of Ag complexes was confirmed by Fourier transform infrared (FTIR) spectroscopy.

Arsenic, an element of environmental impact, can be incorporated into jarosite–type compounds and remain stabilised within the structure under a wide range of environmental conditions. In this study, a sample of ammonium–arsenic jarosite was synthesised by precipitation in sulphate medium at controlled pH of 1.2–1.8. The behaviour of arsenic during the thermal and chemical decomposition of jarosite was analysed; the degradation in alkaline medium of jarosite was also studied. According to the results, the synthesised jarosite is composed of joined rhombohedral crystals, forming tightly spherical shaped particles, 37–54 μm size. The ammonium jarosite produced possessed a high arsenic concentration; its calculated stoichiometry being (NH₄)Fe_2.45[(SO₄)_1.80(AsO₄)_0.20][(OH)_4.15(H₂0)_1.85]. It was found that arsenic is stabilised in the jarosite structure; upon heating, it remains in residual solids above 700°C, whilst in alkaline medium an incongruent dissolution takes place, with the arsenic retained in the solid phase along with iron. These solids, when exposed to high temperatures (1200°C), transform into a type of iron oxide known as hematite, so with arsenic it is retained an iron compound forming a stable compound which withstands high temperatures.

Durante la molienda de sulfuros minerales en molinos de bolas, los elementos molturadores se oxidan y forman una variedad de óxidos, hidróxidos y oxi hidróxidos de hierro; previas investigaciones han establecido que la adsorción de estas especies al mineral contamina la superficie y afectan la etapa de flotación. En esta investigación, se estudió la flotación de esfalerita en presencia de precipitados de hierro férrico y ferroso en diferentes concentraciones, los productos de la flotación se caracterizaron por espectroscopia de infrarrojo por transformada de Fourier. Los resultados muestran que el incremento de la flotación, depende de la formación de óxidos de hierro con una banda de enlace en 619 cm-1 correspondiente a goetita y de los óxidos de zinc con bandas de enlace del Zn–O en 1737, 1378, 1244, y 1031 cm-1, Se detectó además una banda en 1120 cm-1 indicando la formación de ion sulfato tetragonal libre. Similares resultados de flotación y composición superficial se obtienen cuando se tiene 75 ppm de ion férrico o ion ferroso. La esfalerita pulverizada en mortero de ágata, exhibió bandas de enlace del Zn–O, y la formación de sulfatos enlazados de manera mono dentada con el zinc con tres bandas de absorción.

La pirargirita es una sulfosal de plata de formula Ag3SbS3 caracterizada por su alto contenido de plata, lo cual la convierte en una importante fuente de este metal, sin embargo, esta fase se considera altamente refractaria a la lixiviación de plata con cianuro. Por tal motivo se estudió la oxidación de pirargirita bajo diferentes concentraciones de sulfuro de sodio nona hidratado, Na2S.9H2O y tiempos de reacción, los sólidos resultantes de todas las pruebas se caracterizaron por técnicas de: microscopia, difracción de rayos X y espectroscopia de infrarrojo por transformada de Fourier. El análisis por MEB- EDS y DRX confirmaron la presencia de una única fase cristalina de pirargirita con la siguiente composición 58.54 % de Ag, 17.01 de S, 19.49 de Sb y Cu 4.95 %. Los sólidos obtenidos después de cada prueba de oxidación del antimonio con sulfuro de sodio, se caracterizaron y muestran claramente la presencia de sulfuro de plata Ag2S, las fases oxidadas de antimonio no se detectaron por esta vía, sin embargo, la técnica FTIR pudo verificar la formación de enlaces Sb – O del Sb2O3 con las principales bandas de absorción en: 1384, 1019, 534, 760 cm-1.