A study on the leaching kinetics of silver involved in the system S2O3(2-) -O2-Cu2+ that is found in the tailings of Dos Carlos in the state of Hidalgo in Mexico. The concentration of [S2O3(2-)] considerably affects the leaching rate obtaining a value of 0.o98 for the order of reaction in the range of concentrations from15.8 to 126.4 gL-1 of S2O3(2-), achieving silver recovery of 73%. The effect of temperature and of the addition of copper has been also analyzed. Temperature has a remarkable effect over the overall reaction rate in the range from 15 to 60 °C. Solutions of silver of 97% were obtained at the highest temperature of the study obtaining a value of 43 kJ mol-1 for the activation energy. Copper addition favored the leaching rate of silver, obtaining a reaction order of 0.35 with respect to the concentration of [Cu2+] and reaching 95% of leached silver.

Se ha realizado un estudio sobre la cinética de lixiviación de plata en el sistema S2O3(2-)-O2-Cu2+ que se encuentra contenida en las escombreras de Dos Carlos del Estado de Hidalgo en México. La concentración de [S2O3(2-)] influye considerablemente sobre la velocidad de lixiviación obteniéndose un orden de reacción de 0.98 en el rango de 15.8 a 126.4 gL-1, logrando recuperaciones de plata en solución del 73%. Se ha analizado también el efecto de la temperatura y la adición de cobre en la cinética. La temperatura tiene una marcada influencia sobre la velocidad global de la reacción en el rango de 15 a 60°C. Se logró disoluciones de plata del 97% a la más alta temperatura estudiada, obteniendo un valor de 43 kJ mol-1 para la energía de activación. La adición de cobre favoreció la velocidad de lixiviación de la plata, obteniendo un orden de reacción de 0.35 respecto a la [Cu2+] y alcanzando un 95% de plata lixiviada.

Uma amostra de arsenojarosita de potássio foi sintetizada e completamente caracterizada. A amostra obtida é uma solução sólida de arsenojarosita de potássio, cuja fórmula aproximada é [K0,75(H3O)0,25 ]Fe1,84[(SO4)1,82(AsO 4)0,18][(OH)2,34(H 2O)3,66]. O processo de decomposição em meio alcalino foi estudado no período de indução e de conversão progressiva, e a ordem de reação e a energia de ativação foram determinadas para cada caso. Nas condições experimentais utilizadas, os resultados são consistentes com modelo de partícula esférica com núcleo decrescente e controle químico. Em ambos os processos, quatro modelos parciais e dois modelos globais foram desenvolvidos para descrever seu comportamento básico. Os modelos foram validados, e foi provado que descrevem favoravelmente o processo de decomposição em meio alcalino.

A sample of potassium arsenojarosite was synthesized and thoroughly characterized. The obtained sample is a solid solution of potassium arsenojarosite, whose approximate formula is [K0.75(H3O)0.25 ]Fe1.84[(SO4)1.82(AsO 4)0.18][(OH)2.34(H 2O)3.66]. The decomposition process in alkaline medium was studied in the induction and progressive conversion periods, and the reaction order and activation energy were determined for each case. Under the used experimental conditions, results are consistent with the spherical particle model with decreasing core and chemical control. In both processes, four partial models and two global models were developed in order to describe their basic behavior. The models were validated, and it was proved that they favorably describe the decomposition process in alkaline medium.

The effect of the temperature and thiosulfate concentration on the dissolution rate of silver contained in mining wastes, using the system S2O3(2-)-O2-Zn2+ was studied. In the State of Hidalgo in México, thousands of tons of waste mining having around 71 grams of silver per ton of waste have been accumulated over the years. This is the main reason that motivates this study. It was observed that the temperature drastically affects the leaching rate of the silver showing an activation energy Ea= 55.85 kJ mol-1, implying that the dissolution reaction is controlled by the chemical reaction. The thiosulfate concentration shows a considerable influence on the precious metal dissolution rate. The maximum silver dissolution was found to be approximately 97% at 45 °C and 40 gL-1 of [S2O3(2-)]. It is concluded that the process studied represents a good alternative when compared to other processes such as the toxic cyanidation reaction.

Se estudió el efecto de la temperatura y la concentración de tiosulfatos sobre la velocidad de disolución de la plata contenida en desechos mineros, utilizando el sistema S2O3(2-)-O2-Zn2+. En el Estado de Hidalgo en México hay miles de toneladas de desechos mineros con contenidos de plata del orden de 71 gramos de plata por tonelada de desecho, razón que motiva el estudio. Se observó que la temperatura influye drásticamente sobre la velocidad de lixiviación de la plata, presentando una energía de activación Ea= 55.85 kJ mol-1, indicando que la reacción de disolución está controlada por la reacción química. La concentración de tiosulfatos presenta una considerable influencia sobre la velocidad de disolución del metal precioso. La máxima disolución de plata fue de aproximadamente 97% a 45 °C y 40 gL-1 de [S2O3(2-)]. Se concluye que el proceso estudiado parece una buena alternativa a otros procesos como la tóxica cianuración.