Depression mechanism of peracetic acid for flotation separation of chalcopyrite from arsenopyrite based on coordination chemistry
Graphical abstract
Introduction
Arsenic is a highly toxic inorganic pollutant that causes serious environmental and health problems (Mandal and Suzuki, 2002, Neil et al., 2014). Arsenopyrite is one of the most common arsenic-bearing minerals and is often found with chalcopyrite in polymetallic sulfide deposits (Huang et al., 2006). The quality the copper concentrate obtained from chalcopyrite is significantly reduced by the presence of arsenopyrite, which limits its sales potential owing to the strict controls related to the presence of arsenic during the subsequent smelting process (Ma and Bruckard, 2009). The removal of arsenopyrite by flotation in the early stage of mineral processing therefore has significant economic and environmental benefits (Ma and Bruckard, 2009, Yu et al., 2019).
However, both chalcopyrite and arsenopyrite have similar surface properties and high floatability. In addition, the various metal ions present in the slurry, such as those of copper and lead, enhance the flotation of arsenopyrite, thereby inhibiting the separation of the desired mineral by flotation (Chandraprabha et al., 2004, Chandraprabha et al., 2005). The flotation separation of chalcopyrite and arsenopyrite is typically performed through arsenic depression and copper flotation. Conventional depressants of arsenopyrite include inorganic oxidants such as CaO, H2O2, KMnO4, Na2SO3, and Ca(ClO)2, as well as organic compounds containing polyhydroxyl and carboxyl groups, such as humic acids and tannins (Forson et al., 2021, Suyantara et al., 2020, Tapley and Yan, 2003, Zanin et al., 2019). The depression mechanism involves the formation of a hydrophilic oxide film on the arsenopyrite surface after oxidation treatment the formation of hydrogen bonds with the organic groups on the mineral’s surface, resulting in an increase in the hydrophilicity (Lin et al., 2018, Matveeva et al., 2017, Zhang et al., 2020a).
Previous studies (Khoso et al., 2019, Matveeva et al., 2017, Suyantara et al., 2020, Yin et al., 2018) primarily investigated the depression mechanism using chemical characterisation methods such as X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry to elucidate the effects of the depressant on the surface properties of the mineral. However, quantum theory has been increasingly applied in such studies in recent years owing to its advantages in obtaining microscopic information related to minerals. Density functional theory (DFT) simulations are an effective tool for modelling the surface microstructures and adsorption mechanisms of minerals, thus enabling the prediction and elucidation of the interactions between the mineral surface and various reagents at the atomic or electronic level (Chen, 2021, Foucaud et al., 2019, He et al., 2022, Nie et al., 2020, Sit et al., 2012). DFT calculations give information about the adsorption energies of the reagent and atoms present on the mineral surface and, thus, enable the energy differences to be determined (Silva et al., 2018, Wang et al., 2021). Molecular dynamics (MD) simulations are also used widely to study the behaviour of various molecules on mineral surfaces, and are an effective tool for exploring the mechanism underlying the microscopic adsorption of flotation agents on mineral surfaces (Di et al., 2022, Kalinichev et al., 2007, Li et al., 2017, Mabudi et al., 2019, Tang et al., 2021, Zhang et al., 2020b). Furthermore, coordination chemistry are used to describe metal ions in both minerals and coordination complexes(Chen, 2021), which are useful for analysing the interactions between flotation reagents and the metal ions present on mineral surfaces (Chen, 2021, Hounfodji et al., 2021).
In a previous study (Liu et al., 2022), we investigated the depression mechanism of peracetic acid (PAA) during the flotation separation of arsenopyrite and chalcopyrite by chemical characterisation. the depression mechanism of PAA on arsenopyrite. Accordingly, in this study, we herein employed coordination chemistry, MD simulations, DFT calculations, and XPS to further elucidate the depression mechanism of PAA on arsenopyrite. The mechanisms of PAA adsorption on the surfaces of arsenopyrite and chalcopyrite and the differences between them were revealed. Moreover, the highly selective depression mechanism of PAA on arsenopyrite was elucidated. This work provides a deeper understanding of the interaction of PAA with the surface of arsenopyrite and facilitates the development of new, practical arsenopyrite-based depressants with significant industrial importance.
Section snippets
MD simulations
MD simulations use appropriate simplified conditions to model the interactions between atoms in terms of the motion of a particle system. The motion of the atoms obeys Newton's second law while the particle system as a whole obeys Hamilton's principle. Therefore, MD simulations are an advanced method for studying flotation systems and can elucidate the mechanism of adsorption of the treatment agents on the minerals to be separated.
The Forcite module in Materials Studio 2019 was employed to
Adsorption of PAA onto CuFeS2 (1 1 2) and FeAsS (0 0 1) surfaces
MD simulations were performed to explore the interactions between PAA and the CuFeS2 (1 1 2) and FeAsS (0 0 1) surfaces at the molecular level (Fig. 4).
Snapshots of the MD simulations of the initial configuration and that 100 ps after the adsorption of PAA on the CuFeS2 (1 1 2) and FeAsS (0 0 1) surfaces show that the PAA molecules continued to diffuse on the FeAsS (0 0 1) surface but agglomerated on the CuFeS2 (1 1 2) surface after 100 ps (Fig. 4), demonstrating the selectivity of PAA for arsenopyrite
Conclusions
The depression mechanism of PAA in the flotation separation of chalcopyrite and arsenopyrite was investigated using coordination chemistry, and the main conclusions of the study are listed below.
PAA can be adsorbed on the surfaces of both arsenopyrite and chalcopyrite, but is strongly selective for arsenopyrite. The adsorption energy of PAA on the arsenopyrite (0 0 1) surface was − 550.5 kJ/mol, while those for the adsorbtion of PAA by Cu and Fe on the chalcopyrite (1 1 2) surface are −60.3 kJ/mol
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
Financial supports from the High-Level Talent Recruitment Program of Yunnan Province (No. CCC21321005A), and the Yangtze River Scholar Program in Kunming University of Science and Technology (No. 109720190145) are sincerely appreciated.
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