An EIS study of the effects of inorganic salts in the adsorption of flotation reagents on galena
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abstract
The adsorption of some flotation reagents on galena is affected by the chemical composition of the process water used. This study evaluated the effects of water quality on the adsorption of the collector xanthate and the depressant dextrin. For this purpose, the effect on the adsorption of ions typically present in process water of a copper-lead flotation operation was studied. The evaluation was made using solutions prepared with individual salts resembling the concentrations found in process water. The superficial modifications suffered by galena exposed to these solutions were evaluated by means of open circuit potential, electrochemical impedance spectroscopy (EIS), and contact angle measurements. These results showed that the effects on the flotation reagents could be grouped depending on the salts used. Hence, group 1 involves the salts (NaCl, Na2SO4, and MgSO4) that improve the performance of xanthate, which was inferred by the highest adsorption of xanthate measured and the lowest capacitance values registered, while group 2 includes the salts (CaCl2, Ca(OH)2, CaSO4, MgCl2, and NaNO3) that negatively affected the adsorption of xanthate. On the other hand, it was found that divalent ions, such as Ca2 and Mg2 , generally favor the adsorption of dextrin and inhibit the adsorption of xanthate. From EIS measurements, an equivalent circuit (EC) was adjusted and validated, and it was found that it correlates well with contact angle, adsorption and microflotation test results. Hence, the kinetics parameters obtained from EC are useful for the evaluation of water quality effects on either the flotation or depression of galena.
