Tailings waters, chemical analysis

In the metal refining of ores, the metal is solubilized in an aqueous solution. The optical control of metal refining requires quick, accurate analysis of the major chemical species present in solution. Raman spectroscopy and resonance Raman are used to identify the amine complexes of Co, Ni, and Cu species, as well as ammonia sulfate and sulfamate, present in these industrial solutions. The Raman spectra of an industrial plant solution from mine tailings are shown in Fig. 7-15. Each solution contains one or more metal species, sulfate, sulfamate, ammonia, ammonium sulfate, and water. From a comparison with model ammine complexes, the vibrations in the spectra are identifiable. Bands were observed at 615, 980 and 1,110 cm-1 and were assigned to the sulfate ion. No bands were observed for free ammonia. A band at 376 cm-1 was assigned to the Ni(NH3)j + specie. A band at 490 cm-1 was assigned to the Co(NH3)g+ specie. 

Batch leach experiments were performed on tailings material to determine the nature of contaminants distributed on sand and silt and clay-sized fractions. For the batch leach experiments, a mixture of tailings material was prepared using a chemical dispersant (sodium hexametaphosphate (NaPO ) ). The mixture was shaken and allowed to settle in covered beakers for sufficient time such that no particles with a diameter > 50 /im remained in suspension. The fines, which remained in suspension, represented the silt and clay-sized fraction of the samples. At the end of the settling period, the liquid was decanted from the beaker. The remaining sand-sized tailings were dried and transferred to a sealed vial. The decanted solution was passed through a 0.45 /im membrane filter, previously washed with distilled water, and the filtrate was collected and placed in a sealed container. The solids were dried and transferred to a sealed vial. The samples were then analyzed by instrumental neutron activation analysis. 

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