Sphalerite is a zinc-bearing mineral available in abundance. Unfortunately, it has both inferior natural floatability and collector molecules adsorption thereby demanding the use of additional activators like copper sulfate for treating the mineral surface to improve its adsorption properties. Presence of impurities on the mineral lattice results in the variation in the chemical composition of the natural sphalerite. For instance, iron impurities substitute for zinc to form marmatite. Generally, iron impurities affect the sphalerite floatation, copper activation, collector adsorption, and surface reactivity. This has led to intense research work on the effects of iron impurities on the sphalerite mineral.
However, the mechanisms that are responsible for the effects of iron impurities in sphalerite especially on collector adsorption and copper activation are not fully explored. For example, the study of the mineral surface layer coated by collector molecules as well as copper has varied results. Besides,different techniques such as the scanning electrochemical microscopy have been utilized in the investigation of various properties of the surface substrate.
Recently, researchers at Kunming University of Science and Technology Dr. Jian Liu and colleagues comparatively investigated subsequent xanthate adsorption and the copper activation on marmatite and sphalerite surfaces. They utilized local electrochemical impedance spectroscopy (LEIS) followed by the time of flight secondary ion mass spectrometry to analyses further the compositions of marmatite and sphalerite surface layers. Furthermore, they investigated the adsorption of copper and potassium butyl xanthate using inductively coupled plasma-atomic mission spectrometry. Their main aim was to clarify the discrepancies of xanthate adsorption and copper activation on marmatite and sphalerite surfaces. Their research work is published in the journal, Applied Surface Science.
The authors observed a significant decrease in the electrochemical impedance on the surfaces of marmatite and sphalerite as a result of copper activation due to the formation of a compound (CuxS) at the interface of the two minerals. However, the electrochemical impedance increased rapidly after the adsorption of potassium butyl xanthate on copper-activated surfaces that led to the formation of metal-organic compounds on the mineral’s surfaces.
The study is the first to employ local electrochemical impedance spectroscopy technique to comparatively investigate subsequent xanthate adsorption and copper activation on marmatite and sphalerite surfaces. From the comparison of the surface adsorption and LEIS experimental results, the authors noted that activation time is a key influence of copper activation and potassium butyl xanthate adsorption on the surface of marmatite while it has almost negligible effects of the sphalerite surface. For instance, an iron impurity in marmatite exhibited significant influence on the subsequent potassium butyl xanthate (PBX) adsorption, ion exchange and copper absorption speed for a short activation time of about 10 minutes. However, for a longer activation time of about 30 minutes, the experimental results showed improvement in the copper absorption due to the presence of impurities. Unfortunately, no improvement was observed in the adsorption of PBX.
According to Dr. Jian Liu and the research team, iron impurity led to harmful effects on the interaction of the potassium butyl xanthate with the copper activated surface due to the increase in activation energy. After copper activation, the outermost surfaces of marmatite was composed of Cu-Fe while that of sphalerite was composed of copper. Therefore, the distribution of copper in the outermost marmatite surface is less than that of sphalerite thus leading to high copper absorption and less potassium butyl xanthate adsorption on the marmatite surface.
Liu, J., Wang, Y., Luo, D., Chen, L., & Deng, J. (2018). Comparative study on the copper activation and xanthate adsorption on sphalerite and marmatite surfaces Applied Surface Science, 439, 263-271.Go To Applied Surface Science