Preliminary study of the suitability of an abandoned mining area for harvesting efflorescent sulfate salts in the Iberian pyrite Belt, Nerva (Spain)

• During summer, efflorescent sulfate salts cover an area near Río Tinto (Spain). • The efflorescence sulfate salts present highly soluble copper and zinc contents. • Harvesting efflorescences could potentially be beneficial for recovering Cu and Zn. • Some operations could increase performance and would be worth investigating. This preliminary research was aimed at identifying a suitable area for producing efflorescent sulfate salts enriched in elements of interest. An old retention impoundment of heap-leaching liquors situated in the municipal district of Nerva, southwest of Minas de Riotinto (Iberian Pyrite Belt, Huelva, Spain), was chosen for the study. The study zone has a higher part composed of leached mine spoils containing washed ore and some roasted pyrite, and a lower part consists of a mixture of materials eroded from the higher parts. All the water that ends up soaking the lower, flatter surface, called the production area, comes from the rain that falls on it, plus the water that leaches and runs off in the old leaching heaps. Water and solid samples from old leaching heaps, substrates at the base of these heaps, and efflorescent sulfate salts formed over them in summer were collected. The efflorescent sulfate salts were highly acidic and concentrated in As, Cu, Pb, and Zn while relatively diluted in Co, Ni, and Sb. However, the average dissolved amounts, proportionally to the total content, were very high for Cu, Co, Ni, and Zn. Based on the results, it was concluded that harvesting efflorescent sulfate salts could be interesting for recovering Cu and Zn and, with more uncertainty, As, Co, and Ni.