638
W. Zhang et al.
prepared by adding 30 mg single sample (−5 μm) to 60 mL KCl electrolyte solution
(0.01 mol/L) in a beaker (100 mL) at a given pH and required solution. Then, the
suspension was used for zeta potential measurement after being magnetically stirred
for 20 min and left for 5 min. Under each test condition, zeta potential was tested for
three times and the average value was obtained.
DFT Calculation and Wavefunction Analysis of Simplified
Coordination Model
DFT calculation [23] is a suitable method to analyze the interaction between the
collectors and the metal ions on mineral surfaces [24, 25]. In this work, high-precision
DFT calculation was carried out to explore the properties of the coordination model
(between collectors and metal ions), using Gaussian 09 software and under M06D3/6-311++G (d, p) (SDD) (SMD, water) level of theory. In the calculation process,
we simplified the metal ions on mineral surfaces as isolated metal ions in water
because such simplification could decrease the computational costs and ensure an
almost identical simulation of the experiments [26, 27]. Visualization of coordination
structures was done using ChemDraw. Energy decomposition method was utilized
to quantify the distortion energy that the collector molecules have to overcome.
To further probe into the electronic structure of CSC-1, several wavefunction analysis methods were performed using Multiwfn [28], including electrostatic potential
surface (EPS), natural population analysis (NPA), and electron localization function
(ELF). EPS and NPA charge are both qualitative tools to plot and elucidate the electron distribution of the molecule and thus provide us insight into its interaction with
metal ions. ELF plot, on the other hand, is a promising way to describe how localized
or delocalized the electrons are; thus, we can analyze the alignment of the lone pairs
and how they affect the distortion energy.
Results
Micro-Flotation Tests of Single Mineral
To examine the feasibility of the envisaged selectivity of CSC-1, individual microflotation tests were selected as a model experiment to optimize the reagent scheme. In
initial studies, the flotation recoveries of pyrite, sphalerite, and galena were compared
by using EX or CSC-1 with different collector concentrations (show in Fig. 3).
Results of single mineral flotation tests using EX as a collector indicate that flotation
recoveries of three kinds of minerals are almost indistinctive, especially at ultra-low
collector concentrations (below 1 × 10
−5 mol/L). However, using CSC-1 as the
collector, flotation recoveries of sphalerite and galena turn remarkably higher than
W. Zhang et al.
prepared by adding 30 mg single sample (−5 μm) to 60 mL KCl electrolyte solution
(0.01 mol/L) in a beaker (100 mL) at a given pH and required solution. Then, the
suspension was used for zeta potential measurement after being magnetically stirred
for 20 min and left for 5 min. Under each test condition, zeta potential was tested for
three times and the average value was obtained.
DFT Calculation and Wavefunction Analysis of Simplified
Coordination Model
DFT calculation [23] is a suitable method to analyze the interaction between the
collectors and the metal ions on mineral surfaces [24, 25]. In this work, high-precision
DFT calculation was carried out to explore the properties of the coordination model
(between collectors and metal ions), using Gaussian 09 software and under M06D3/6-311++G (d, p) (SDD) (SMD, water) level of theory. In the calculation process,
we simplified the metal ions on mineral surfaces as isolated metal ions in water
because such simplification could decrease the computational costs and ensure an
almost identical simulation of the experiments [26, 27]. Visualization of coordination
structures was done using ChemDraw. Energy decomposition method was utilized
to quantify the distortion energy that the collector molecules have to overcome.
To further probe into the electronic structure of CSC-1, several wavefunction analysis methods were performed using Multiwfn [28], including electrostatic potential
surface (EPS), natural population analysis (NPA), and electron localization function
(ELF). EPS and NPA charge are both qualitative tools to plot and elucidate the electron distribution of the molecule and thus provide us insight into its interaction with
metal ions. ELF plot, on the other hand, is a promising way to describe how localized
or delocalized the electrons are; thus, we can analyze the alignment of the lone pairs
and how they affect the distortion energy.
Results
Micro-Flotation Tests of Single Mineral
To examine the feasibility of the envisaged selectivity of CSC-1, individual microflotation tests were selected as a model experiment to optimize the reagent scheme. In
initial studies, the flotation recoveries of pyrite, sphalerite, and galena were compared
by using EX or CSC-1 with different collector concentrations (show in Fig. 3).
Results of single mineral flotation tests using EX as a collector indicate that flotation
recoveries of three kinds of minerals are almost indistinctive, especially at ultra-low
collector concentrations (below 1 × 10
−5 mol/L). However, using CSC-1 as the
collector, flotation recoveries of sphalerite and galena turn remarkably higher than