Kinetics of Alkaline Decomposition and Cyaniding of Argentian Rubidium Jarosite in NaOH Medium
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THE family of jarosite type compounds is represented by the following formula: M Fe3 (SO4)2 (OH)6, where M can include some of the following cations: H3O+, Na+ K+, Rb+, Ag+, NH4+, Tl+, ½ Pb2+, or ½ Hg2+. Jarosite-type compounds are of interest to mineralogists and to metallurgists devoted to extractive metallurgy. Although nine jarosites have been synthesized, only six of these have been recognized in nature as mineral species, while the remaining three are rubidium jarosite, thallium jarosite, and mercury jarosite, which only have been obtained by way of synthesis.[1] Chemical names are used to label synthetic products, and mineral names are reserved to jarosites found in nature. For the case presented in this study, Argentian rubidium jarosite[2,3] has no analogous equivalent that is found in nature, and it is, therefore, called by its chemical name. Jarosite minerals—principally natrojarosite, potassium jarosite, argentian jarosite and plumbojarosite— have a long and impressive history as a source of silver. Historically, humans had the first contact with these types of minerals at around 1200 B.C. in the Spanish southeast, where it was first found in the Jaroso Ravine ELEAZAR SALINAS RODRI´GUEZ, EDUARDO CERECEDO SA´ENZ, MARIUS RAMI´REZ, FRANCISCO PATIN˜O CARDONA, and MIGUEL PE´REZ LABRA, Professors, are with the Universidad Auto´noma del Estado de Hidalgo, A´rea Acade´mica de Ciencias de la Tierra y Materiales, Hidalgo 42184, Me´xico. Contact e-mail: salinasr@ uaeh.edu.mx Manuscript submitted January 10, 2012. Article published online July 19, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
in the Almagrera Sierra. This is where its name came from.[4,5] Minerals from Spanish Gossan were formed by a natural leaching in situ of pyritic ores, leading a gradual substitution of original iron sulfurs by iron oxides with (among other elements) some contents of silver, gold, lead, and arsenic.[6] In Mexico, it is known that jarosites occurred by meteorization processes, with principal deposit sites of jarosites noted in Hidalgo,[7] Zacatecas, Durango, and Chihuahua. On the other hand, it is known that the application of conventional cyaniding of these minerals for silver extraction presents some problems, as this process yields erratic and sometimes problematic recoveries of silver. Rubidium jarosite was first synthesized in 1975, in Dutrizac and Kaiman[2]; at this time, rubidium was also first characterized. Moreover, Dutrizac and Kaiman obtained it as a jarositic product of precipitation from an aqueous solution using the technique of slow addition. Dutrizac and Kaiman concluded that hydonium ion (H3O+) is substituted in part for the alkaline metal, and therefore, the resulting jarosite is hexagonal (R3m). This analysis was done by thermal gravimetric analysis. Some researchers have discussed their work pertaining to jarosites synthesized in Mexico. For instance, Patin˜o et al.,[8] who have worked with both synthetic jarosites and with jarosites generated in the zinc hydrometallurgy industry, found in all cases
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