Journal Information
Share
Share
Download PDF
More article options
Visits
0
Original Article
DOI: 10.1016/j.jmrt.2019.09.009
Open Access
Available online 25 September 2019
Adsorption and depression mechanism of an environmentally friendly reagent in differential flotation of Cu–Fe sulphides
Visits
0
Sultan Ahmed Khosoa,b, Zhiyong Gaoa,b, Mengjie Tiana,b, Yuehua Hua,b,
Corresponding author
huyuehuacsu@126.com

Corresponding authors at: School of Minerals Processing and Bioengineering, Central South University, Changsha, 410083, China.
, Wei Suna,b,
Corresponding author
sunmenghu@csu.edu.cn

Corresponding authors at: School of Minerals Processing and Bioengineering, Central South University, Changsha, 410083, China.
a School of Minerals Processing and Bioengineering, Central South University, Changsha, 410083, China
b Key Laboratory of Hunan Province for Clean and Efficient Utilization of Strategic Calcium-Containing Mineral Resources, Central South University, 410083 Changsha, China
This item has received
0
Visits

Under a Creative Commons license
Article information
Abstract
Full Text
Bibliography
Download PDF
Statistics
Figures (10)
Show moreShow less
Tables (2)
Table 1. Characteristic peaks of major functional groups in TCSS.
Table 2. Flotation separation of a mixture of pyrrhotite and chalcopyrite in presence of 60mg/L TCSS and 20mg/L SBX at pH 7.
Show moreShow less
Abstract

Utilization of large doses of inorganic reagents in mineral industry not only leads to high cost but also increases the toxicity in the environment. This research provides a new, environmentally friendly, biodegradable, and cost-effective depressant reagent, namely tricarboxylate sodium starch (TCSS), in chalcopyrite and pyrrhotite flotation systems. The selective depression and adsorption mechanism of TCSS on the two minerals were studied through the laboratory based measurements such as microflotation experiments, XPS spectral analysis, IR spectral analysis, adsorption amount analysis and zeta potential measurements. The addition of TCSS exhibited a much better depressive performance towards pyrrhotite than chalcopyrite in a wide pH range. Binary mineral flotation experiments indicated that an effective separation between the two minerals could be possible at a low concentration of TCSS, at which an improved recovery and grade of chalcopyrite of more than 75% could be achieved. All of the analytical measurements justified the flotation results and revealed that TCSS behaved differently with the two minerals. TCSS showed significantly much greater affinity towards pyrrhotite, the reason of which may be the presence of large amount of metal hydroxyl species on its surface.

Keywords:
Organic depressant
Flotation
Pyrrhotite
Chalcopyrite
Tricarboxylate sodium starch
Full Text
1Introduction

Upgrading of copper ore by selective separation of copper bearing minerals from either pyrite or pyrrhotite is very important and challenging. Both of these sulphide gangues have very little economic value and are closely associated with copper minerals in the natural ore deposits [1–4]. Compared with pyrite, pyrrhotite contains relatively large amount of iron (60% from its chemical formula), therefore its inclusion in mineral concentrates dilutes the grade of copper metal and reduces its economic value [5,6]. More, the presence of pyrrhotite in copper concentrates is the significant contributor of SO2 emissions at the smelting stage [7–10]. Therefore, the removal of pyrrhotite from copper concentrates at preliminary stage operations is of great economic and environmental advantages.

Several approaches have been applied to separate the copper bearing minerals from pyrrhotite. Among others, froth flotation route is proved to be the more effective technique for the sulphide minerals enrichment [9–12]. Flotation method is based mainly on the surface characteristics of minerals [13–16], which can be modified using various flotation reagents including collectors, depressants, frothers, and modifiers. Extensive research investigations have been carried over the last few decades, which have studied the flotation behaviors of pyrrhotite, but different researchers drew different conclusions. Most important factors including crystal structure, chemical composition, and physical properties of pyrrhotite determine its floatability [9,10,17]. Overall, the pyrrhotite is commonly rejected to the flotation tailings as a waste product [18–21]. Therefore, in the massive sulfide ores treatment, the flotation process often aims to depress the pyrrhotite. However, the depression of pyrrhotite in conventional flotation systems using xanthate as the collector is quite difficult. It is well known that the xanthate also adsorbs onto pyrrhotite surface and floats it with other copper minerals [8,10,17]. Hence, to depress the flotation of pyrrhotite gauges, copper industry mostly needs an effective depressant or depressant system.

To date, the inorganic reagents are regularly applied for the depression of pyrrhotite flotation. Lime, cyanides, sulphites, potassium dichromates or a combination of these reagents are the common depressants of pyrrhotite or other iron sulphide gangue minerals in Cu–Fe conventional flotation circuits [22–27]. The inorganic depressants have shown to be effective; however, their larger doses are commonly required which not only lead to high operational cost but also increase the toxicity in the environment. Organic polymers, on the other hand, have benefits of better selectivity, low costs, and low pollutions. Organic polymers are environmentally friendly reagents and have been considered as more favorable flotation depressants.

The major advantages of biopolymers over inorganic reagents are that the polymers have greater flexibility to be modified, which can effectively improve their selectivity as well as the depression effect. Most commonly investigated organic depressants for pyrrhotite flotation include DMPS [28], guar gum [29], diethylenetriamine [30], sodium metabisulphite and triethylenetetramine [5], leptospirillum ferriphilum and acidithiobacillus caldus [6]. Many of them have presented promising possibilities in the pyrrhotite rejection when used in the laboratory-based flotation experiments at carefully controlled conditions. In general, the hydrophilic functional groups in a polymer enhance the hydrophilic character of mineral surface, facilitating the depression of mineral via the reduced possibility of bubble-particle attachment [31–33].

Recently, our research group has prepared a series of starch-based novel biopolymers aiming at introducing some new, ecologically and economically efficient flotation depressants in the mineral industry. This paper describes the successful depression and adsorption mechanism of tricarboxylate sodium starch (TCSS) on pyrrhotite and chalcopyrite with sodium butyl xanthate (SBX) as the collector. The depressant performance of TCSS on single and mixed minerals was examined using a serious of microflotation tests. The mechanism was investigated through analytical measurement techniques including zeta potential measurements, XPS spectral analysis, IR spectral analysis and adsorption amount analysis.

2Experimental2.1Minerals and reagents

Mineral samples of pyrrhotite and chalcopyrite used in this investigation were supplied by Yunfu, Guangdong Province, China. Fig. 1 shows the X-ray diffraction (XRD) results of given mineral samples. Samples were carefully handpicked, crushed, ground in the laboratory porcelain mill and sieved to obtain a maximum amount of 38–74μm size fraction for flotation experiments. The undersized samples (size <38μm) were further ground to −2μm for zeta potential measurements, adsorption amount analysis, IR spectral analysis and XPS spectral analysis. The ground samples were stored in the sealed glass bottles under the well-controlled conditions to protect them from oxidation.

Fig. 1.

XRD results of pyrrhotite and chalcopyrite samples.

(0.08MB).

Tricarboxylate sodium starch (TCSS) was the main depressant reagent in this study. TCSS was prepared through the chemical treatment of starch with H2O2 and NaOH. The IR spectrum and main characteristic peaks of major functional groups in TCSS are presented in Fig. 2 and Table 1, respectively. Sodium butyl xanthate (industrial grade, 92% purity), from chemical factory of Zhuzhou, China, was used as the collector. Terpineol (analytical grade, 95% purity) from Guangdong Xilong chemical Co., Ltd., China was used as the frother. Sodium hydroxide and nitric acid (analytical grade, Tianjin Kemiou Chemical Reagent Co., Ltd., China) were used as the pH modifiers in flotation experiments. The deionized (DI) water with a resistivity of 18.2MΩ.cm was used in all of the experiments.

Fig. 2.

IR spectrum of TCSS.

(0.08MB).
Table 1.

Characteristic peaks of major functional groups in TCSS.

Wavenumber (cm−1Assignment 
1024.12  CO stretching vibrations 
1415.15  Carboxylate (CO2, symmetric) stretching 
1605.29  Carboxylate (CO2, asymmetric) stretching 
2901.75  CH stretching vibrations 
3404.63  OH stretching vibrations 
2.2Flotation experimental procedures

Flotation experiments were performed in the XFG flotation machine (Jilin Exploration Machinery Plant, Changchun, China). The speed of an impeller was kept constant at 1700rpm for all the experiments. In single mineral experiments, flotation pulp was prepared by adding 2g of mineral into a 40mL plexiglass cell containing 35mL of DI water. Following the pH adjustment with a stirring time of 2min, the flotation reagent(s) was/were added to the mineral suspension and conditioned for desired time. The addition order and conditioning time of each reagent are displayed in Fig. 3. Finally, the frother was added and tails and concentrates were collected for 5min. The collected products were oven-dried at 60°C for 12h and weighed for recovery calculations. Flotation experiments were repeated three times and the average recovery was reported as the final value.

Fig. 3.

Flowsheet for flotation experiments under TCSS (depressant) and SBX (collector).

(0.09MB).

In selective flotation experiments, a mixture of the two minerals was used as the flotation feed. For this, chalcopyrite and pyrrhotite were manually mixed in a 1:1 ratio. Flotation procedure, reagent addition order, and conditioning time of each reagent were the same as that shown in Fig. 3. The recovery and grade of chalcopyrite and pyrrhotite were determined from the solid mass distribution between the concentrates and tailings and their chemical assays. All of the experiments were conducted at a room temperature (25±1°C).

2.3Interaction mechanism via zeta potential measurements

Essential interaction mechanism of TCSS on mineral surfaces was revealed through the zeta potential measurements. Zeta potential measurements were carried out using a ZETASIZER spectrometer (Nano-Zs90 series, Malvern Instruments, UK). Mineral suspension was prepared by mixing 20mg of mineral into 40mL of 1×10–3 mol/L KCl as the background electrolyte solution. Following the pH adjustment with a stirring time of 2min, flotation reagent(s) was/were added as the same manner as shown in Fig. 3 and conditioned for 10min. After allowing the coarser grains to settle down for 5min, the pH of suspension was noted and the supernatant containing fine particles was transferred to a capillary cell for zeta potential measurements. Zeta potential was determined three times for each sample, and the average was reported as a final value. All of the measurements were conducted at a room temperature (25±1°C).

2.4Interaction mechanism via reagent adsorbed amount measurements

Adsorbed amounts of TCSS onto pyrrhotite and chalcopyrite surface at different concentration of TCSS were determined based on the solution depletion method. Mineral suspension was prepared by adding 2g of mineral into a 40mL plexiglass cell containing 35mL of DI water. Following the pH adjustment with a stirring time of 2min, a pre-determined dose of TCSS was added and conditioned for 3min. Finally, the supernants were centrifuged for 30min at 10,000rpm and residual concentration of TCSS in solutions was determined via a Total Organic Carbon analyzer (TOC-VCPH, Shimadzu, Japan). TCSS amounts adsorbed on the mineral surfaces were calculated using Eq. (1). All of the measurements were conducted at a room temperature (25±1°C).

where, Γ represents the adsorbed amount of reagent (mg/g); V is the volume of the solution(L); Co and C are the TCSS concentrations in initial solution and supernatant, respectively, and m represents the mass of the mineral sample (g).

2.5Interaction mechanism via infrared spectral measurements

Infrared spectral (IR) analysis was carried out using a Bruker Alpha FTIR spectrometer (Nicolet 6700, Thermo Scientific, USA) in the range from 4000 to 400cm−1. About 1.0% (mass fraction) of the each mineral treated or untreated with TCSS was blended with a spectroscopic grade KBr. All of the measurements were performed at a room temperature (25±1°C), and data were processed using the software OPUS. Samples were prepared by adding 1g of mineral into a 40mL plexiglass cell containing 35mL of DI water. Following the pH adjustment with a stirring time of 2min, flotation reagent(s) was/were added as the same manner as shown in Fig. 3 and conditioned for 20min each. Finally, the treated samples were washed three times with DI water, filtered, and dried in a vacuum desiccator over 24h prior to IR spectral measurements.

2.6Interaction mechanism via X-ray photoelectron spectroscopy measurements

X-ray photoelectron spectroscopy (XPS) analysis was performed using an ESCALAB 250Xi spectrometer (Thermo Fisher-VG Scientific, USA) with Al Kα as the sputtering source at 12kV and 6mA. The pressure of analyzer chamber was set at 1.0×10−12 Pa. For calibration, the binding energy of C1s was set at 284.8eV. Curve fittings and quantification of spectra were measured by using Thermo Scientific Avantage software. Samples were prepared by adding 1g of mineral into a 40mL plexiglass cell containing 35mL of DI water. Following the pH adjustment with a stirring time of 2min, flotation reagent(s) was/were added as the same manner as shown in Fig. 3 and conditioned for 20min each. Finally, the treated samples were washed three times with DI water, filtered, and dried in a vacuum desiccator over 24h prior to XPS spectral measurements. All of the measurements were conducted at a room temperature (25±1°C).

3Results and discussion3.1Flotation results (single minerals)

Fig. 4 shows flotation behaviors of pyrrhotite and chalcopyrite at different pH values in the absence and presence of TCSS. In the absence of TCSS, pyrrhotite and chalcopyrite exhibited excellent flotation with SBX throughout the investigated pH range (2–12). This indicates that, pyrrhotite and chalcopyrite respond well to SBX and their selective separation is impossible without adding any depressant. However, the addition of TCSS (added before SBX) affected the flotation behaviors of two minerals and reduced the flotation recovery of pyrrhotite much greater than that of the chalcopyrite. Under the same experimental conditions, the recovery of pyrrhotite was decreased from 90% to 15% and that of chalcopyrite was decreased from 90% to 83%. This largest recovery difference between the two minerals indicates that TCSS had a much greater depression effect on flotation of pyrrhotite than that of the chalcopyrite. These results provide the preliminary information and suggest that TCSS could cause the flotation separation of chalcopyrite from pyrrhotite.

Fig. 4.

Flotation behaviors of pyrrhotite (Pyt) and chalcopyrite (Clp) at different pH values with 20mg/L SBX in absence and presence of 50mg/L TCSS.

(0.14MB).

In order to investigate the effects of different doses of TCSS on flotation behaviors of pyrrhotite and chalcopyrite, flotation tests on single minerals were extended further by fixing pH at neutral conditions. Fig. 5 displays flotation behaviors of pyrrhotite and chalcopyrite as a function of TCSS doses at pH 7. Flotation of pyrrhotite and chalcopyrite were gradually decreased with increasing doses of TCSS from 15 to 90mg/L. A promising recovery difference between the two minerals was again achieved at relatively lower doses of TCSS (15–60mg/L). The larger doses more than 60mg/L TCSS significantly impacted the chalcopyrite flotation and reduced the recovery difference between the two minerals. From these encouraging results, it was concluded that TCSS, which is non-hazardous, biodegradable, widely available and cost-effective reagent, has a great potential to be applied in selective flotation separation of chalcopyrite and pyrrhotite.

Fig. 5.

Flotation behaviors of pyrrhotite (Pyt) and chalcopyrite (Clp) at different doses of TCSS with 20mg/L SBX and pH 7.

(0.1MB).
3.2Flotation results (mixed minerals)

After achieving the optimized conditions from single mineral flotation tests, the effectiveness of TCSS was further examined via selective flotation experiments. Selective flotation experiments were performed on a mixture of chalcopyrite and pyrrhotite (1:1 ratio) using 60mg/L TCSS, 20mg/L SBX at pH 7. Results of the selective flotation experiments are illustrated in Table 2.

Table 2.

Flotation separation of a mixture of pyrrhotite and chalcopyrite in presence of 60mg/L TCSS and 20mg/L SBX at pH 7.

Products  Yield  Recovery (%)Grade (%)
  (wt./%)  CuFeS2  Fe1-xCuFeS2  Fe1-x
Flotation concentrate  46.50±0.61  75.64±0.30  17.62±0.34  80.97±0.37  19.03±0.37 
Flotation tailing  53.50±0.61  24.36±0.30  82.38±0.34  22.67±0.39  77.33±0.39 
Flotation feed  100  100  100  50  50 

The addition of TCSS provided an improved flotation separation between pyrrhotite and chalcopyrite. As shown in Table 2, the grade of chalcopyrite in flotation concentrate was over 80%, which is a more than 60% improvement in chalcopyrite grade compared to that in feed before flotation. In contrast, the grade of pyrrhotite in flotation concentrate was very poor and less than 20%, indicating a more than 60% reduction from the pyrrhotite grade in the flotation feed. More, the recovery of pyrrhotite in concentrate was only 17% and that of chalcopyrite was over 75%. This largest difference between the recovery of two minerals shows that when both pyrrhotite and chalcopyrite were present together in the suspension, TCSS preferentially adsorbed onto pyrrhotite surface depressed its flotation and allowed the chalcopyrite to float in the mixture.

At this stage it is quite difficult to explain why TCSS is more selective depressant for pyrrhotite flotation. To gain comprehensive information further analytical measurements were carried out, and the results are described in the following sections. However, in flotation experiments, the addition of TCSS achieved a good level of pyrrhotite depression with a minor compromise in terms of chalcopyrite recovery. This study therefore concluded that TCSS has a great potential to replace other toxic depressants in copper industry.

3.3Zeta potential results

Zeta potentials of mineral particles in the absence and presence of reagents are illustrated in Fig. 6. Zeta potential results of pyrrhotite and chalcopyrite before the interaction with reagents are quite consistent with previously published literature. The surface of pyrrhotite was comparatively more positive than that of chalcopyrite, the reason of which may be the presence of oxidation species on its surface.

Fig. 6.

Zeta potential results of (a) pyrrhotite (Pyt) and (b) chalcopyrite (Clp) at different pH values in presence of 60mg/L TCSS and 20mg/L SBX.

(0.26MB).

The addition of TCSS shifted the zeta potentials of pyrrhotite and chalcopyrite towards more negative side. Negative shifts in zeta potentials of minerals with addition of TCSS may be due to adsorption of negative functional groups of TCSS. The addition of TCSS achieved a decrease of more than 10mV in the zeta potentials of pyrrhotite compared to a decrease of approximately 3mV for chalcopyrite in a wide pH range of 3–9. This signifies the worth of electrostatic interactions in the adsorption of TCSS. The magnitude of positive charges on pyrrhotite surface between pH 3 and 9 was much greater than that on chalcopyrite since the isoelectric points (IEP) for the two minerals are pH 7 and 3.4, respectively. Therefore, the negative functional groups of TCSS interacted with the highly positive surface of pyrrhotite more than chalcopyrite. Moreover, the zeta potentials of pyrrhotite particles were not significantly shifted after the addition of collector (SBX), indicating that the pre-adsorbed TCSS inhibited the adsorption of collector on pyrrhotite surface. On the contrary, the zeta potentials of chalcopyrite were significantly shifted to more than 9mV, representing that the adsorption of TCSS was much weaker on chalcopyrite surface.

To summarize, zeta potential results show that the surface of pyrrhotite adsorbs much greater amount of TCSS than that of the chalcopyrite. The greater affinity of TCSS towards pyrrhotite compared to chalcopyrite can be attributed to its highly positive surface. However, the presence of metal hydroxyl species can also promote the adsorption of TCSS onto pyrrhotite surface [34–36].

3.4Reagent adsorbed amount

Zeta potential measurements indicated the different interaction behavior of TCSS with the two minerals. The adsorbed amounts of TCSS on surface of pyrrhotite and chalcopyrite were calculated to quantify the adsorption behaviors. Fig. 7 shows the adsorbed amounts of TCSS on pyrrhotite and chalcopyrite at different doses of TCSS. The adsorption of reagent on these minerals was increased progressively with increasing concentration of TCSS. As can be seen in Fig. 7, at same concentration of TCSS the adsorbed amount on pyrrhotite surface was much greater than that on chalcopyrite surface. This largest difference between the adsorbed amounts on two minerals indicates that TCSS had a much greater affinity towards pyrrhotite compared to chalcopyrite. The substantial adsorption of TCSS prevented the further adsorption of collector on pyrrhotite surface and thus depressed its flotation more than chalcopyrite.

Fig. 7.

Adsorbed amounts on pyrrhotite (Pyt) and chalcopyrite (Clp) at different concentrations of TCSS at pH 7.

(0.1MB).
3.5IR spectral results

Infrared spectroscopy was further applied to understand the interaction mechanism of TCSS on two minerals. Fig. 8 illustrates the infrared (IR) spectra of minerals before and after interaction with reagents. IR spectra of minerals particles before the treatment with reagents are consistent with previous reports [29,32]. Compared with chalcopyrite, IR spectrum of pyrrhotite before the treatment with reagents indicated some pronounced peaks at 1090.17, 1026.88, and 797.68cm−1, which may be assigned to surface oxidation species [37]. These results confirmed the zeta potential measurements and showed that the surface of pyrrhotite was oxidized during the sample preparation procedures.

Fig. 8.

IR spectra of (a) pyrrhotite (Pyt) and (b) chalcopyrite (Clp) in presence of 60mg/L TCSS and 20mg/L SBX at pH 7.

(0.28MB).

Fig. 8(a) shows that the addition of TCSS heavily adsorbed on pyrrhotite and produced some strong infrared peaks on its surface. The adsorption peaks around 1617.08 and 1416.91cm–1 were corresponded to asymmetric and symmetric stretching vibrations of −COOH groups in TCSS. More, the characteristic adsorption peaks of −CH groups (2917.15 and 2848.71cm−1) and −OH groups (3404.69cm−1) on pyrrhotite surface were significantly appeared after the addition of TCSS. The intensities of all of the surface oxidation species were also reduced, indicating that TCSS had a much greater affinity towards the hydroxyl species on mineral surface. Interestingly, no adsorption peaks of xanthate or its oxidation products (dixanthogen) were shown on TCSS pre-adsorbed pyrrhotite surface. These results closely followed the zeta potential measurements and showed that the prior addition of TCSS prevented the further adsorption of collector on pyrrhotite surface.

Fig. 8(b) shows the IR spectra of chalcopyrite particles under the same conditions. As can be seen, TCSS brought very limited effects on chalcopyrite surface; the characteristics adsorption peaks of all the functional groups of TCSS were very weak. The surface of chalcopyrite indicated only some weak adsorption peaks of −CH groups, indicating that TCSS was adsorbed mainly via the −CH groups through hydrogen bonding. Obviously, the significant adsorption peaks of copper-xanthate compounds (1057.03 and 1138.01 cm−1) and dixanthogen (1267.61cm−1) can be noted on the surface of TCSS-treated chalcopyrite. The adsorption of collector and its oxidation to dixanthogen on surface clearly indicate that TCSS had a weaker interaction towards chalcopyrite. Due to limited effects of TCSS, chalcopyrite surface adsorbed a significant amount of collector that enhanced its flotation more than pyrrhotite.

As explained previously, the greater affinity of TCSS towards pyrrhotite compared to chalcopyrite can be due to the presence of larger amounts of metal hydroxyl species on pyrrhotite surface. Similar adsorption mechanisms of some other organic depressants have also been reported on the oxidized pyrite surface [38,39]. The difference in mineralogical structures may also be the reason of different behaviour of TCSS with the two minerals.

3.6XPS spectral results

X-ray photoelectron spectroscopy analysis is widely used to expose the chemical state of a mineral surface. In this regard, the surface characteristics of mineral particles in absence and presence of reagents were further studied through X-ray photoelectron spectroscopy (XPS).

Fig. 9 shows the high resolution XPS spectra of O (1s) from the surface of pyrrhotite and chalcopyrite in the absence and presence of TCSS. In Fig. 9 (a), the pyrrhotite surface in absence of TCSS indicated peaks around 530.33 and 530.93eV, which may be corresponded to O2− and −OH, respectively [40,41]. It is generally considered that Fe(III) and Fe(II) oxides have peaks around 530.56eV; therefore, the peak at a binding energy of 530.93eV can be allotted to iron oxide/hydroxide species on pyrrhotite surface. After the treatment with TCSS, the peak of −OH at 530.93eV was broaden and increased in intensity, and the new intensive peaks at 531.79 and 532.35eV corresponding to carboxylic groups were appeared [42,43]. This result indicates that both functional groups (COOH, OH) of TCSS were adsorbed onto the surface of pyrrhotite. In Fig. 9(b), the chalcopyrite surface in absence of TCSS indicated peaks around 529.69 and 530.41eV, which may be corresponded to lattice oxygen and adsorbed oxygen, respectively [44]. As can be noted, there was a very limited effect of TCSS on the chalcopyrite surface; little to no changes took place in intensities and binding energies of the existing peaks after the addition of TCSS. Hence, these results are also consistent with IR spectral analysis and revealed that the chalcopyrite surface remained mildly inert to TCSS treatment at the investigated concentrations.

Fig. 9.

High resolution XPS spectra of O (1s) from surface of (a) pyrrhotite (Pyt) and (b) chalcopyrite (Clp) in absence and presence of 60mg/L TCSS.

(0.27MB).

Fig. 10 shows the high resolution XPS spectra of Fe (2p) and S (2p) from the surface of pyrrhotite and chalcopyrite in the absence and presence of TCSS. In pyrrhotite and chalcopyrite before the treatment with TCSS, the peaks around 707.45±0.05 and 720.0±0.05eV from Fe (2p) spectra, and 161.47±0.5 and 162.43±0.5 from S (2p) spectra were corresponded to spin-orbitals of 2p3/2 and 2p1/2, respectively. Fe (2p) and S (2p) spectra of pyrrhotite surface indicated the oxidation species peaks, thus confirming zeta potential measurements and IR spectral analysis. However, the surface of chalcopyrite was relatively clear and free of oxidation species, as reflected from Fe (2p) and S (2p) spectra of chalcopyrite. By comparing, the addition of TCSS changed the surface characteristics of pyrrhotite much greater than that of the chalcopyrite. The most affected peaks in Fe (2p) and S (2p) spectra of pyrrhotite were the surface oxidation peaks that were significantly reduced and shifted from their positions. This result justifies the conclusions drawn from zeta potential measurements and IR spectral analysis and showed that TCSS was mainly adsorbed due to the presence of surface oxidation species on pyrrhotite. As the surface of chalcopyrite contained little to no oxidation species, therefore, its surface remained mildly inert to TCSS adsorption.

Fig. 10.

High resolution XPS spectra of Fe (2p) and S (2p) from surface of (a, b) pyrrhotite (Pyt) and (c, d) chalcopyrite (Clp) in absence and presence of 60mg/L TCSS.

(0.37MB).
4Conclusions

Present research systematically investigated the depression and adsorption mechanism of a new, environmentally friendly, biodegradable, and cost-effective depressant reagent, namely tricarboxylate sodium starch (TCSS), on chalcopyrite and pyrrhotite flotation systems. A series of laboratory scale measurements including microflotation experiments, zeta potential measurements, XPS spectral analysis, IR spectral analysis and adsorption amount analysis were performed to evaluate its depressive effectiveness. Following outcomes were drawn:

  • 1.

    Flotation results indicated that TCSS strongly and selectively depressed the flotation of pyrrhotite than that of the chalcopyrite in a low pH range. The effective separation of chalcopyrite from pyrrhotite, with an improved recovery and grade of chalcopyrite of more than 75%, was achieved with the addition of low concentrations of TCSS.

  • 2.

    All of the analytical measurements justified the flotation results and revealed that TCSS interacted differently with the two minerals. TCSS showed comparatively much greater affinity towards the surface of pyrrhotite than that of the chalcopyrite.

  • 3.

    Zeta potential measurements and reagent adsorption analysis showed that the surface of pyrrhotite adsorbed significantly much greater amount of TCSS than that of the chalcopyrite.

  • 4.

    IR spectral and XPS spectral analyses indicated that the presence of large amounts of metal hydroxyl species promoted the adsorption of TCSS on the pyrrhotite surface.

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgments

This research was supported by the Natural Science Foundation of China (No. 51634009); the Innovation Driven Plan of Central South University (No. 2015CX005); the National 111 Project (No. B14034); the Collaborative Innovation Centre for Clean and Efficient Utilization of Strategic Metal Mineral Resources, the Key Laboratory of Hunan Province for Clean and Efficient Utilization of Strategic Calcium-containing Mineral Resources (No. 2018TP1002), and the Fundamental Research Funds for the Central Universities of Central South University (No. 2018zzts227).

References
[1]
H. Moslemi, P. Shamsi, F. Habashi.
Pyrite and pyrrhotite open circuit potentials study: effects on flotation.
Miner Eng, 24 (2011), pp. 1038-1045
[2]
L. October, K. Corin, N. Schreithofer, M. Manono, J. Wiese.
Water quality effects on bubble-particle attachment of pyrrhotite.
Miner Eng, 131 (2019), pp. 230-236
[3]
J.D. Miller, J. Li, J.C. Davidtz, F. Vos.
A review of pyrrhotite flotation chemistry in the processing of PGM ores.
Miner Eng, 18 (2005), pp. 855-865
[4]
V. Lawson, G. Hill, L. Kormos, G. Marrs.
The separation of pentlandite from chalcopyrite, pyrrhotite and gangue in nickel projects throughout the world.
Proceedings Twelfth Mill Operators Conference, (2014), pp. 153-162
[5]
S. Kelebek, C. Tukel.
The effect of sodium metabisulfite and triethylenetetramine system on pentlandite–pyrrhotite separation.
Int J Miner Process, 57 (1999), pp. 135-152
[6]
G. Gu, K. Zhao, G. Qiu, Y. Hu, X. Sun.
Effects of Leptospirillum ferriphilum and Acidithiobacillus caldus on surface properties of pyrrhotite.
Hydrometallurgy, 100 (2009), pp. 72-75
[7]
Z. Ekmekçi, M. Becker, E.B. Tekes, D. Bradshaw.
The relationship between the electrochemical, mineralogical and flotation characteristics of pyrrhotite samples from different Ni Ores.
J Electroanal Chem, 647 (2010), pp. 133-143
[8]
B. Arvidson, M. Klemetti, T. Knuutinen, M. Kuusisto, Y.T. Man, C. Hughes-Narborough.
Flotation of pyrrhotite to produce magnetite concentrates with a sulphur level below 0.05% w/w.
Miner Eng, 50-51 (2013), pp. 4-12
[9]
S.A. Allison, C.T. O’Connor.
An investigation into the flotation behaviour of pyrrhotite.
Int J Miner Process, 98 (2011), pp. 202-207
[10]
G.E. Agar.
Flotation of chalcopyrite, pentlandite, pyrrhotite ores.
Int J Miner Process, 33 (1991), pp. 1-19
[11]
X. Cheng, I. Iwasaki.
Effect of chalcopyrite and pyrrhotite interaction on flotation separation.
Trans Soc Min Metall Explor Inc, 9 (1992), pp. 73-79
[12]
I. Bunkholt, R.A. Kleiv.
Pyrrhotite oxidation and its influence on alkaline amine flotation.
Miner Eng, 71 (2015), pp. 65-72
[13]
S.A. Khoso, M.I. Abro, M.H. Agheem.
Evaluation of mesh of liberation of Zard Koh and kulli koh Iron ores of Pakistan.
Mehran Univ Res J Eng Technol, 37 (2018), pp. 569-580
[14]
S.A. Khoso, M.I. Abro, M.H. Agheem.
Mineralogical study of Zard Koh and kulli koh Iron ore deposits of Pakistan.
Mehran Univ Res J Eng Technol, 36 (2017), pp. 1017-1024
[15]
Z. Yin, L. Xu, J. He, H. Wu, S. Fang, S.A. Khoso, et al.
Evaluation of l-cysteine as an eco-friendly depressant for the selective separation of MoS2 from PbS by flotation.
J Mol Liq, 282 (2019), pp. 177-186
[16]
H. Wu, J. Tian, L. Xu, S. Fang, Z. Zhang, R. Chi.
Flotation and adsorption of a new mixed anionic/cationic collector in the spodumene-feldspar system.
Miner Eng, 127 (2018), pp. 42-47
[17]
V. Bozkurt, Z. Xu, J. Finch.
Pentlandite/pyrrhotite interaction and xanthate adsorption.
Int J Miner Process, 52 (1998), pp. 203-214
[18]
D. Fornasiero, M. Montalti, J. Ralston.
Kinetics of adsorption of ethyl xanthate on pyrrhotite: in situ UV and infrared spectroscopic studies.
J Colloid Interface Sci, 172 (1995), pp. 467-478
[19]
Dong J, Xu M. Method for improving selectivity and recovery in the flotation of nickel sulphide ores that contain pyrrhotite by exploiting the synergy of multiple depressants. Google Patents; 2016.
[20]
G.R. da Silva, K.E. Waters.
The effects of microwave irradiation on the floatability of chalcopyrite, pentlandite and pyrrhotite.
Adv Powder Technol, 29 (2018), pp. 3049-3061
[21]
T. Chimbganda, M. Becker, J.L. Broadhurst, S.T.L. Harrison, J.P. Franzidis.
A comparison of pyrrhotite rejection and passivation in two nickel ores.
Miner Eng, 46-47 (2013), pp. 38-44
[22]
Y. Mu, Y. Peng, R.A. Lauten.
The depression of pyrite in selective flotation by different reagent systems—a literature review.
Miner Eng, 96-97 (2016), pp. 143-156
[23]
C. Zhao, D. Huang, J. Chen, Y. Li, Y. Chen, W. Li.
The interaction of cyanide with pyrite, marcasite and pyrrhotite.
Miner Eng, 95 (2016), pp. 131-137
[24]
C. Tukel, S. Kelebek.
Modulation of xanthate action by sulphite ions in pyrrhotite deactivation/depression.
Int J Miner Process, 95 (2010), pp. 47-52
[25]
C.A. Prestidge, J. Ralston, R.S.C. Smart.
The competitive adsorption of cyanide and ethyl xanthate on pyrite and pyrrhotite surfaces.
Int J Miner Process, 38 (1993), pp. 205-233
[26]
J. Liu, S. Yuan, Y. Han, Y. Li.
The effects of various activators on flotation performance of lime-depressed pyrrhotite.
Can Metall Q, (2018), pp. 1-8
[27]
J. Liu, Li E-l, K. Jiang, Li Y-j, Y.-x. Han.
Effect of acidic activators on the flotation of oxidized pyrrhotite.
Miner Eng, 120 (2018), pp. 75-79
[28]
W. Sun, L. Runqing, X. Cao, H. Yuehua.
Flotation separation of marmatite from pyrrhotite using DMPS as depressant.
Trans Nonferrous Met Soc China, 16 (2006), pp. 671-675
[29]
X. Chen, G. Guohua, L. Lijuan, C. Zhixiang.
Effect of food-grade guar gum on flotation separation of chalcopyrite and monoclinic pyrrhotite in low-alkali systems.
Physicochem Probl Miner Process, 55 (2019), pp. 437-447
[30]
R.H. Yoon, C.I. Basilio, M.A. Marticorena, A.N. Kerr, R. Stratton-Crawley.
A study of the pyrrhotite depression mechanism by diethylenetriamine.
Miner Eng, 8 (1995), pp. 807-816
[31]
Y. Mu, Y. Peng, R.A. Lauten.
The mechanism of pyrite depression at acidic pH by lignosulfonate-based biopolymers with different molecular compositions.
Miner Eng, 92 (2016), pp. 37-46
[32]
S.A. Khoso, Y. Hu, R. Liu, M. Tian, W. Sun, Y. Gao, et al.
Selective depression of pyrite with a novel functionally modified biopolymer in a Cu–Fe flotation system.
Miner Eng, 135 (2019), pp. 55-63
[33]
S.A. Khoso, Y. Hu, F. Lyu, R. Liu, W. Sun.
Selective separation of chalcopyrite from pyrite with a novel non-hazardous biodegradable depressant.
J Clean Prod, (2019),
[34]
K. Shrimali, V. Atluri, X. Wang, J.D. Miller.
Adsorption of corn starch molecules at hydrophobic mineral surfaces.
Colloids Surf A Physicochem Eng Asp, (2018), pp. 546
[35]
Q. Liu, J.S. Laskowski.
The interactions between dextrin and metal hydroxides in aqueous solutions.
J Colloid Interface Sci, 130 (1989), pp. 101-111
[36]
N.K. Khosla, R.P. Bhagat, K.S. Gandhi, A.K. Biswas.
Calorimetric and other interaction studies on mineral—starch adsorption systems.
Colloids Surf, 8 (1984), pp. 321-336
[37]
R.H. Lara, M.G. Monroy, M. Mallet, M. Dossot, M.A. González, R. Cruz.
An experimental study of iron sulfides weathering under simulated calcareous soil conditions.
Environ Earth Sci, 73 (2014), pp. 1849-1869
[38]
A. López-Valdivieso, A.A. Sánchez-López, E. Padilla-Ortega, A. Robledo-Cabrera, E. Galvez, L. Cisternas.
Pyrite depression by dextrin in flotation with xanthates. Adsorption and floatability studies.
Physicochem Probl Miner Process, (2018), pp. 54
[39]
A. Lopez Valdivieso, A. Sánchez López, S. Song, H. García Martínez, S. Licón Almada.
Dextrin as a regulator for the selective flotation of chalcopyrite, galena and pyrite.
Can Metall Q, 46 (2007), pp. 301-309
[40]
D.L. Legrand.
Oxidation/alteration of pentlandite and pyrrhotite surfaces at pH 9.3: part 1. Assignment of XPS spectra and chemical trends.
Am Mineral, 90 (2005), pp. 1042-1054
[41]
Y. Mikhlin, V. Varnek, I. Asanov, Y. Tomashevich, A. Okotrub, A. Livshits, et al.
Reactivity of pyrrhotite (Fe9S10) surfaces: spectroscopic studies.
J Chem Soc Faraday Trans, 2 (2000), pp. 4393-4398
[42]
G.F. Moreira, E.R. Peçanha, M.B.M. Monte, L.S. Leal Filho, F. Stavale.
XPS study on the mechanism of starch-hematite surface chemical complexation.
Miner Eng, 110 (2017), pp. 96-103
[43]
M. Sanchez-Arenillas, E. Mateo-Marti.
Spectroscopic study of cystine adsorption on pyrite surface: from vacuum to solution conditions.
Chem Phys, 458 (2015), pp. 92-98
[44]
T. Hirajima, H. Miki, G.P.W. Suyantara, H. Matsuoka, A.M. Elmahdy, K. Sasaki, et al.
Selective flotation of chalcopyrite and molybdenite with H 2 O 2 oxidation.
Miner Eng, 100 (2017), pp. 83-92
Copyright © 2019. The Authors
Journal of Materials Research and Technology

Subscribe to our newsletter

Article options
Tools
Cookies policy
To improve our services and products, we use cookies (own or third parties authorized) to show advertising related to client preferences through the analyses of navigation customer behavior. Continuing navigation will be considered as acceptance of this use. You can change the settings or obtain more information by clicking here.