Evaluation of collector adsorption by electrochemical impedance spectroscopy

•EIS and SERS techniques were used to evaluate adsorption of collectors on pyrite.•Coating resistance (Rc) was used as a proxy to measure rate of adsorption of collectors.•The order of adsorption of collectors was determined based on Rc values.

Laboratory bench-scale flotation test is generally used as a standard method to investigate effects of different flotation reagents on flotation performance. A comprehensive test program requires large amount of representative samples, takes long time and could be costly. Hence, developing alternative cost effective, fast and low cost methods have recently been in the subject of many research studies. Microflotation, induction time measurement, electrochemical methods, etc. have been used to measure adsorption of flotation reagents and derive a proxy to correlate with flotation behaviors of sulfide minerals. In this study, Electrochemical Impedance Spectroscopy (EIS) method was used to measure rate of collector adsorption on two different pyrite rich samples from flotation plants processing Carlin and Yanacocha Verde ores. Eight different types of collectors were selected based on their chemistry and applications in flotation operations. Adsorption of the collectors were also measured by using Surface Enhanced Raman Spectroscopy (SERS) technique and correlated with EIS results. The results showed clearly that Carlin pyrite was more electrochemically reactive than Verde pyrite. Rate of adsorption of the collectors was related to coating resistance (Rc), which was calculated using an equivalent electrical circuit model fitted to the EIS data. Based on Rc values, order of adsorption of the collectors for Carlin and Verde samples were discussed. It is therefore shown that preliminary reagent selection for a specific ore can be done using EIS technique, which is considerably faster and low cost compared to the other techniques.