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Interaction of cu-bearing solutions with calcite, aragonite and gypsum: a comparative study

AuthorsJiménez, Amalia; Astilleros, José Manuel CSIC ORCID; Fernández Díaz, Lurdes ; Fernández González, Ángeles; Pérez-Garrido, Carlos; Cubillas, P.; Prieto, Manuel
Issue Date11-Sep-2016
Citation2nd European Mineralogical Conference (2016)
AbstractCopper is present in igneous and sedimentary rocks in minor to trace amounts. Copper participates in numerous essential to life biological processes and is considered a strategic element for a variety of industrial and agricultural applications. Copper can be released to the environments as a component of wastewaters, which can increase its concentration in natural waters to reach values considered toxic for the health of organisms. Previous works have demonstrated that the surfaces of abundant calcium bearing rock-forming minerals like calcite, aragonite and gypsum are efficient uptakers of dissolved metals. Understanding the mechanism involved in the interaction between these minerals and waters bearing metals should help to develop improved strategies for the treatment of mining wastes. In this work, we focus on waters bearing copper and study their interaction with calcite, aragonite and gypsum combining microscopic and nanoscopic observations. We aim to obtain information on their relative effectiveness as copper uptakers, for which we have conducted series of batch type and AFM experiments at room temperature. The batch type sorption experiments involved the reaction of ~1 g of 1.0-1.5 mm sized fragments of the corresponding calcium bearing mineral with CuNO3 (1.0, 5.0 and 10mM) in thermostat closed polypropylene vessels during increasing reaction times (between 1 and 12 days). Chemical analyses of the aqueous solution after different elapsed times evidence that the interaction with any of the three calcium-bearing minerals results in the removal of dissolved copper. The characterization of the interacted mineral fragments by scanning electron microscopy (SEM) and conventional powder glancing X-ray diffraction (XRD) shows the development of rough surfaces on the minerals accompanied by the formation of randomly distributed malachite (Cu2CO3(OH)2) spherulites. The reaction mechanisms involve the continuous dissolution of the primary phase followed by the precipitation of malachite regardless the calcium-bearing primary phase. The rate of dissolution directly relates to the initial concentration of copper in the aqueous solution in all three cases. However, the degree of surface coverage by malachite precipitates significantly differs depending on the substrate. Thus, while precipitates cover wide areas of aragonite surfaces, they form isolated patches on specific areas of the surfaces of calcite and gypsum. AFM observations confirm the strong interaction between all solid and copper-bearing aqueous solutions, with etch pits rapidly forming and coalescing and a new, epitactic-related phase immediately forming on the substrate. Our results once again evidence the relevance of mineral-water interactions in controlling the fate of pollutants and the suitability of mineral/water interaction-based strategies to control and remedy mining-related contamination.
DescriptionTrabajo presentado en la 2nd European Mineralogical Conference (EMC), celebrada en Rimini (Italia) del 11 al 15 de septiembre de 2016
Appears in Collections:(IGEO) Comunicaciones congresos
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