Near-Field Optical Examination of Potassium n-Butyl Xanthate/Chalcopyrite Flotation Products

Tamás Firkala,Martin Rudolph,Tobias Nörenberg,Alexej Pashkin,Harald Foerstendorf,J Klopf,Susanne Kehr,Lukas Eng,Frederik Kuschewski

doi:10.3390/min8030118

Abstract

The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used in beneficiation. We thus identified KBX reaction products both by IR optical far- and near-field techniques, applying attenuated total internal reflection Fourier-transform infrared spectroscopy (ATR FT-IR) in comparison to s-SNIM, respectively. The major KBX band around 880 cm−1 was probed in s-SNIM using both the tunable free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf facility, Germany, and table-top CO2 laser illumination. We then were able to monitor the KBX agglomeration in patches <500 nm in diameter at the CCP surface, as well as nanospectroscopically identify the presence of KBX reaction products down to the 10−4 M concentration.

Highlights

Flotation is known as one of the most frequently used technologies in the mineral processing industries, annually separating billions of tons of valuable minerals from worthless material.Many primary resources of copper, zinc, lead, gold, platinum group metals (PGM), graphite, etc.may be recovered by this process
We addressed the fingerprint region of KBX by combining s-SNIM with mid-IR laser sources, i.e., a table-top CO2 laser and the free-electron laser (FEL) FELBE at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
CCP and KBX raw materials as well as CCPX-2a, CCPX-3a, and CCPX-4a products were firstly investigated by macroscopic mid-IR spectroscopy with the goal of retrieving their relevant IR

Summary

Introduction

Flotation is known as one of the most frequently used technologies in the mineral processing industries, annually separating billions of tons of valuable minerals from worthless material.Many primary resources of copper, zinc, lead, gold, platinum group metals (PGM), graphite, etc.may be recovered by this process. Flotation is known as one of the most frequently used technologies in the mineral processing industries, annually separating billions of tons of valuable minerals from worthless material. The technology is based on the control of the wettability of mineral surfaces using the selective adsorption of amphiphilic molecules. Even though the process has been established for more than a century, the microscopic understanding of flotation still stands in its infancy; little is known, for instance, about the spatial coverage and adsorption of the mediating amphiphilic molecules, e.g., when varying the local chemical environment or the surface potential, influencing the recovery of valuables and the separation efficiency of the flotation process. We introduced optical near-field techniques as a valuable methodology to collect both spectroscopic and microscopic data from such sample systems, down to the nanometer scale. We used potassium n-butyl xanthate (C4 H9 OCSSK: KBX) adsorbed to chalcopyrite (CCP) as the model system, and tracked the relevant optical fingerprint regions for the amphiphilic KBX reaction products by both the infrared (IR) optical far and near field using attenuated total reflection Fourier-transform infrared spectroscopy (ATR FT-IR) and scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM), respectively

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Results

Conclusion