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Article

Application of Thionocarbamates in Copper Slag Flotation

by
Zoran Štirbanović
1,*,
Daniela Urošević
2,
Milica Đorđević
3,
Jovica Sokolović
1,
Nemanja Aksić
2,
Novka Živadinović
3 and
Sandra Milutinović
2
1
University of Belgrade, Technical Faculty in Bor, Vojske Jugoslavije 12, 19210 Bor, Serbia
2
Mining and Metallurgy Institute Bor, Zeleni Bulevar 35, 19210 Bor, Serbia
3
Serbia ZiJin Copper d.o.o., Đorđa Vajferta 29, 19210 Bor, Serbia
*
Author to whom correspondence should be addressed.
Metals 2022, 12(5), 832; https://doi.org/10.3390/met12050832
Submission received: 1 April 2022 / Revised: 29 April 2022 / Accepted: 10 May 2022 / Published: 12 May 2022
(This article belongs to the Special Issue Flotation and Leaching Processes in Metallurgy)
Browse Figures
Versions Notes

Abstract

:
Thionocarbamates are the group of collectors that are mostly used for flotation of sulphide copper minerals, alone or in combination with xanthates depending on a mineralogical composition of the ore. In this paper, the results of the study of application of thionocarbamates in copper slag flotation are presented. Chemical analysis of smelter slag sample obtained from Flotation plant in Bor, Serbia, showed that it contains 3.56% of copper, of which over 73% is in the sulphide form, as well as 0.58 g/t of gold and 11.30 g/t of silver. XRD analysis identified fayalite and magnetite as main minerals present in the slag and SEM-EDS analysis showed that copper is mainly present in the form of sulphide minerals, thus making it suitable for flotation with thionocarbamates. Two thionocarbamates MX 980 and TC 1000 and one xanthate SIPX, along with their mixtures MX 980 + SIPX and TC 1000 + SIPX, were investigated. The influence of parameters such as collector type and dosage, grinding fineness, pulps’ pH and flotation time, on flotation indicators (recovery, yield and copper grade in concentrate) were determined. Smaller dosages of thionocarbamates (40 g/t) provided concentrates with high copper grades, 22.34% (MX 980) and 18.42% (TC 1000) and lower recovery rates, 83.98% (MX 980) and 87.78% (TC 1000), while the increase of dosages to 200 g/t led to the increase of recovery rates for more than 4% and a significant decrease in copper grades. The increase of grinding fineness from 50% to 70% of grain size < 0.074 mm showed a positive impact on flotation indicators, recovery rate, copper grade and yield, for all investigated collectors and their mixtures, while, with the further increase from 70% to 90%, recovery rates continued to increase while copper grades decreased. The increase of pulps’ pH had a positive influence, especially for MX 980, for which recovery rates increased with the increase of pH from 8 to 10 (12). A flotation kinetics test showed that flotation with TC 1000 was the fastest, i.e., recovery rate after 20 min of flotation was over 91%, while recoveries obtained with other collectors were a few percentage points lower.

1. Introduction

Collectors are a group of reagents used in flotation for enhancing hydrophobicity of wanted minerals. They are organic compounds which are being adsorbed on surfaces of desired minerals, thus making them hydrophobic, reducing the stability of the hydrated layer separating the mineral from the air bubble to such extent that attachment of the particle to the bubble can be made, i.e., collectors reduce the induction time.
Another purpose of collectors is to provide selectivity of minerals with similar floatability properties [1,2,3].
The selection of collector in copper flotation is in close correlation with nature and appearance of copper minerals and other sulfides that are associated with them [4]. Xanthates are mostly used collectors in copper flotation and they can be applied alone or in combination with other collectors, such as dithiophosphates or thionocarbamates, which are normally used for flotation of secondary copper minerals or in the case when flotation is performed at lower pH [2].
Thionocarbamates are classified as chelating collectors, in which stabile complexes are formed by chelation with surface metal ions through the C=S and N-H groups [3]. Thionocarbamates are mostly used for copper sulphide minerals flotation, alone or in combination with xanthates depending on a mineralogical composition of the ore [1,2]. Thionocarbamates in combination with xantates represent an efficient collector mixture for flotation of two or more copper minerals, e.g., chalcocite, covellite, chalcopyrite, and bornite, present in the ore [2,5]. O-isobutyl-N-ethyl thionocarbamate (IPETC) can be used for the flotation of variety of copper minerals such as chalcocite, chalcopyrite, cubanite, and bornite [6,7]. Thionocarbamates are also well-known selective collectors used for selective flotation of sulfide copper minerals from other sulfides such as pyrite, arsenopyrite, galena, sphalerite, marmatite, etc., or selection of one sulfide mineral from other sulfides. Bu et al. [8] applied IPETC for selection of chalcopyrite from galena. The same collector, i.e., IPETC, was used by for decoupling pyrite and arsenopyrite, with the addition of CuSO4 for activation of both oxidised pyrite and arsenopyrite [9]. The separation of Cu sulfide minerals (chalcopyrite, chalcocite, covellite, and bornite) from Fe sulfide minerals (pyrite and marcasite) by using dialkyl thionocarbamates and ethoxycarbonyl thionocarbamates was studied by Guang-yi et al. [10]. The results of the study showed that ethoxycarbonyl thionocarbamates (ECTC) had very good recovery rates for copper minerals, and they were also very selective against iron sulfide minerals at pH 8–9. Thionocarbamates can be also used as secondary collectors for processing copper-zinc ores, in both copper and zinc flotation circuits. Their main role in copper flotation circuit is to increase copper recovery [1] and in zinc flotation circuit, when sulfide iron minerals are present, they are used for selection of zinc minerals (sphalerite or marmatite) from sulfide iron minerals (pyrite or pyrrhotite) [2,3].
Copper slag represents a residue of pyro-metallurgical treatment of copper concentrates [11]. Since the concentrates are obtained from copper ores that differ in mineralogical composition and are being processed by different smelting technologies, large amounts of copper and other valuable metals can be present in the slag [12,13,14]. In addition, quantities of slag that are being generated vary on applied technology and, according to some sources, approximately 2,2 t of slag are generated for production of 1 t of pure copper [12].
The main minerals present in the slag are fayalite and magnetite [14,15,16]. Copper can be present in the form of sulfide minerals, oxide minerals or as a native copper [17,18].
Copper and other valuable metals can be recovered from slag by flotation [13,19,20,21], leaching [22,23,24], roasting [25,26], or their combination [27,28,29]. Some of these methods were briefly reviewed by Gorai et al. (2002) [12].
Copper slag and/or residues from slag’ processing can be also used for various purposes such as cement production, construction of roads and buildings, etc. [30,31,32,33,34,35,36,37,38,39,40,41].
Flotation is the main process for processing slag for valorization of copper and other metals. In order to achieve the best copper recovery and quality of the concentrate, it is necessary to optimize the whole process starting from grinding, i.e., liberation of copper bearing minerals from gangue [19,21,42], flotation parameters such as pulp’ density, pH, conditioning and flotation time, etc. [13] and also types and dosages of applied flotation reagents: collectors, frothers and others [43]. Xanthates are most commonly used collectors for recovery of copper bearing minerals from slag. However, some recent research has shown that a combination of xantahes with some other secondary collectors can result in enhanced copper recovery [21,43]. Application of thionocarbamates as collectors for flotation of copper bearing minerals from slag was investigated by very few researchers, and the research conducted with this collector type on copper minerals from copper ores indicates the necessity for more thorough investigation since copper in slag mainly appears in correlation with sulfur, i.e., in sulfide form. This was the main reason why the application of thionocarbamates for copper slag flotation was the objective of this study.

Adsorption Mechanism of Thionocarbamates

The mechanisms of the adsorption of collectors on sulfide mineral surfaces play an important role in the flotation process. A large number of studies have been conducted with a focus on the adsorption of thionocarbamates on sulfide copper minerals, but there are no studies dealing with adsorption of thionocarbamates on surfaces of copper bearing particles present in copper slag.
Ethoxycarbonyl thionocarbamates (ECTC) collectors are powerful for chalcopyrite and very selective against pyrite in alkaline and neutral pH conditions. The adsorption on chalcopyrite preferentially occurs at Cu atoms instead of Fe atoms [44].
The separation of Cu and Fe sulfide minerals by flotation can be achieved at pH 8.5 for ECTC. It was reported that ECTC collectors were powerful for copper minerals and very selective against iron sulfide minerals at pH 8–9 [10].
Flotation effect of O-isobutyl-N-ethyl thionocarbamates (IBET) on Cu minerals, at pH 10, is very good. IBET has the ability to collect most copper-bearing minerals in porphyry copper ores, especially chalcocite and chalcopyrite. IBET is primarily adsorbed by sulfur atoms combined with monovalent copper ions (Cu−) or divalent copper ions (Cu2+) on the surface of the chalcocite and chalcopyrite [7].
Flotation collector O-isopropyl N-ethylthionocarbamate (IPETC), often referred to as Z-200, is widely used for separation of sulfides ores, and numerous research studies were conducted on the adsorption of IPECT on the mineral surface [6,8,9,45,46].
IPETC interacts strongly with Cu atoms on the mineral surface of chalcopyrite. Most of the IPETC is strongly adsorbed on the chalcopyrite surface as HIPETC, with minor IPETC chemisorbed to Cu atoms [6].
IPETC adsorbs most strongly on chalcocite at pH 4–10, while on chalcopyrite and pyrite, adsorption continues to increase with decreasing pH. Adsorption on chalcocite is 3–20 times higher than on chalcopyrite and pyrite. IPETC chemisorbs on chalcocite through sulfur below pH 6 and through both sulfur and oxygen above pH 6 [45].
The floatability of chalcopyrite is better than that of galena in the presence of IPETC, and the recovery difference between chalcopyrite and galena is about 20% when IPETC is 7 × 10−4 mol/L at pH 9.5, while the floatability difference between the two minerals is significant. Competitive adsorption of OH- and IPETC on mineral surfaces leads to lower floatability of galena than that of chalcopyrite. IPETC is able to remove the hydration layer on mineral surfaces and then adsorb on active sites [8].
The adsorption of IPETC (Z-200) is more exothermic on chalcopyrite than on pyrite, which indicates the strong selectivity against pyrite [46].

2. Materials and Methods

2.1. Materials

Copper slag sample was taken out from the industrial process in Flotation plant Bor, as a definite crushing product < 12 mm. The sample was dried, crushed in the laboratory jaw crusher, and sieved through a sieve in order to obtain grain size < 3 mm. Afterwards, samples of 0.73 kg were taken for grinding and flotation tests.

2.2. Collectors

2.2.1. Sodium Isopropyl Xanthate

Sodium isopropyl xanthate (SIPX) is a collector which, due to its high collector power and low price, is the most widespread xanthate in the industrial practice of sulfide ore flotation. It is also suitable for flotation of native copper and pyrite in acidic environments.

2.2.2. AERO MX 980

AERO MX 980 (Cytec Industries, Woodland Park, NJ, USA) is a collector belonging to the group of thionocarbamates (n-butyoxycarbonyl-O-n-butyl thionocarbamate-15–30%). According to the manufacturer—Cytec Industries Inc.—MX 980 is a powerful collector (with frother properties) used in the flotation of primary and secondary copper minerals in combination with pyrite and gold (chalcopyrite + secondary copper sulfides + metallic copper + copper oxides). The MX 980 collector is colored orange, with a density of 0.960–1.020 g/cm3, and is insoluble in water.

2.2.3. TC 1000

TC 1000 (Beijing Techrich Development Co., Ltd., Beijing, China) is a collector belonging to the group of modified thionocarbamates and consists of thionocarbamates (>90%) and isobutanol (<10%). The molecular composition of this collector is similar to mustard oil and is biodegradable. The collector has modified characteristics that improve the effect of the collector from the xanthate group and is an effective co-collector in the flotation of copper, lead, zinc, etc. The TC 1000 collector is amber in color, insoluble in water, but soluble in alcohols, esters, and ethers.

2.3. Methods

2.3.1. Chemical Composition

In order to determine copper content, Atomic Absorption Spectrophotometer–Perkin Elmer 2380 (Leko, Prague, Czech Republic) was used, by dissolving 0.1 g of the sample with the mixture of acids: HCl, HNO3, and HF. The same instrument was also used for determination of oxide copper content and the only difference was that the sample was dissolved with diluted H2SO4. The instrument Carbon and Sulfur Analyzer–HORIBA EMIA 920 (HORIBA, Ltd., Kyoto, Japan) was used for sulfur content, by adding tungsten, potassium, and iron to 0.01 g of the sample, in order to accelerate its burning. Inductively Coupled Plasma Optical Emission (ICP-OES) Spectrometer–Spectro Ciros Vision (Spectro., Cleve, Germany) was used for determination of contents of Al2O3, SiO2, and Fe. In order to determine Si content, 0.5 g of sample was mixed with the mixture of sodium and potassium carbonates and melted, while contents of Al and Fe were determined from the remaining filtrate.

2.3.2. X-ray Diffraction (XRD) Analysis

X-ray diffraction (XRD) analysis was used for identification of mineral species present in the smelter slag. The sample was first powdered in agate mortar in order to prepare it for the analysis, which was performed by XRD analyzer “Rigaku MiniFlex 600” (Rigaku, Tokyo, Japan) with a “D/teX Ultra 250” high-speed detector (Rigaku, Tokyo, Japan) and copper anode X-ray tube. The angle range during the analysis was 3–90°, step 0.02°, and recording speed 10°/min. The voltage of the X-ray tube was 40 kV and the current was 15 mA. For the identification of the minerals, the software PDXL 2 (Version 2.4.2.0, Rigaku, Tokyo, Japan) was used, and XRD patterns were compared with data from the ICDD database (PDF-2 Release 2015 RDB).

2.3.3. Scanning Electron Microscopy (SEM) Analysis

Scanning electron microscope “Tescan Vega 3 LMU” (TESCAN, a.s., Brno, Czech Republic) was used for scanning electron microscopy (SEM) analysis while the energy-dispersive spectrometer (EDS) “Oxford instruments X-act” (Oxford instruments Inc., Abingdon, UK) was used for the elemental analysis. The surface of the samples was scanned by a focused electron beam. In order to achieve a conductivity of the examined sample, a thin film of graphite in a vacuum was evaporated on its surface. The imaging was done at 20 kV with a 15 mm working distance (WD) by using backscattered (BSE) electrons, which belong to the primary electron beam. The analysis was performed with magnification 200×. Qualitative and semi-quantitative chemical compositions were determined by an EDS detector equipped with the INCA microanalysis software package (INCA Energy 250, Oxford Instruments Analytical, High Wycombe, UK).

2.3.4. Grinding and Flotation Tests

Prior to flotation, test samples (0.73 kg in mass) were grinded in the laboratory ball mill with standard ball charge in order to achieve certain openness. The content of solid in the mill was 70% in weight.
After the samples were prepared, flotation machine Denver DR-12 (Denver Equipment Devision, Surrey, UK), with a stainless steel cell, was used for rough flotation tests. The useful pulp volume of the cell was 2.4 L. The rate of the impeller was 1500 rpm, and the flow of air added during flotation was 360 L/min. The content of the solid in the flotation pulp was 25% by weight. The pulp was conditioned for 5 min, followed by 40 min of flotation. Flotation tests were carried out in four series. In the first series, the influence of type and dosages of flotation collectors on recovery of copper, yield, and copper grade in concentrate were investigated. Flotation collectors were: SIPX (100; 300; 600 g/t), MX 980 (40; 100; 200 g/t), TC 1000 (40; 100; 200 g/t), and their mixtures SIPX (100 g/t) + MX 980 (40; 100 g/t) and SIPX (100 g/t) + TC 1000 (40; 100 g/t). In the second series of tests, the influence of finesse of grinding was investigated, i.e., openness of grinding products (50%; 70%; 90% −0.074 mm), on technological indicators of flotation process, recovery of copper, yield, and copper grade in concentrate, for all three collectors (SIPX, MX 980 and TC 1000). The third series of flotation tests was carried out in order to investigate the influence of pulps’ pH (8; 10; 12) on flotation indicators, for all collectors and their mixtures. Frother Dowfroth D-250 (Dow Chemical Co., Midland, MI, USA) was used for all flotation tests in the following way: 4 g/t was added in conditioning and 6 g/t in flotation. The pulps’ pH was regulated by using CaO. In the fourth series of experiments, flotation kinetics was done for all collectors and their mixtures with parameters that showed the best results in the previous three series.

3. Results and Discussion

3.1. Chemical Composition

In order to determine chemical composition of smelter slag, chemical analysis of the slag sample was performed. The results of the analysis are shown in Table 1.
The results given in Table 1 show a high content of copper, 3.56%, of which over 73% is in the sulphide form. Iron content is also very high, which was expected bearing in mind previous research that showed the high presence of iron minerals in slag, especially fayalite. The contents of gold and silver, 0.58 g/t and 11.30 g/t respectively confirm that slag is an interesting material from the point of its processing and valorization of metals.

3.2. XRD Analysis

XRD analysis was performed for the purpose of determining mineralogical composition of the slag, i.e., identifying mineral species present in the slag. The results of the analysis are presented in Figure 1.
From the XRD pattern shown in Figure 1, it can be seen that fayalite and magnetite are the main minerals present in the slag, which is in accordance with previous research conducted on various types of slag [16,17].

3.3. Scanning Electron Microscopy (SEM) Analysis

The main objective of the study was to investigate the possibility of using thionocarbamates for flotation of copper from smelter slag. Since thionocarbamates are mainly collectors for flotation of sulphide minerals, scanning electron microscope was used to determine the type of mineral species present in the slag, with special regard to copper minerals. The results of SEM and EDS analysis are shown in Figure 2.
As it can be seen from Figure 2, the results of EDS analysis show that copper is mainly present in association with sulphur and iron, i.e., in the form of sulphide minerals. According to these findings, thionocarbamates can be used for flotation of copper from smelter slag.

3.4. Flotation Tests

3.4.1. Collector Type and Dosage

The first series of flotation tests were carried out in order to determine the influence of collector type and dosage on flotation indicators, copper recovery rate, yield, and copper grade in concentrate. One collector from xanthate group of collectors, sodium isopropyl xanthate (SIPX), and two from the group of thionocarbamates, AERO MX 980 and TC 1000, as well as their mixtures, were under study.
Figure 3 shows the results of flotation tests with regard to the influence of collector type and dosages on smelter slag flotation indicators (Cu grade, yield and recovery) for all investigated collectors: SIPX, MX 98, TC 1000, and their mixtures SIPX and MX 980 and SIPX and TC 1000.
Analyzing the results of flotation tests presented in Figure 3a, it can be concluded that SIPX provided high copper recovery, especially with higher dosages 300 g/t and 600 g/t. Yield was also high with these two dosages, while copper grade in concentrate with dosage 600 g/t was significantly lower, 9.63%; then, it was with 300 g/t, 13.16%. Bearing this in mind, it can be said that SIPX collected both liberated particles of copper and middlings. Therefore, dosage 300 g/t was selected for further experiments because the results it gave were as good as or even better than the double dosage.
The recovery rates that were obtained with collector MX 980 were slightly lower than with SIPX (Figure 3b), but it showed better selectivity especially with lower dosages 40 g/t and 100 g/t, which can be concluded from copper grades in concentrate. Yield and copper grade in concentrate obtained with dosage 200 g/t show that with the increase of dosages of AERO MX 980 selectivity has the tendency of getting lower. Further testing with this collector was conducted with dosage 200 g/t.
The results obtained with collector TC 1000 (Figure 3c) showed similar trends as with MX 980. Lower dosages provided lower recovery rates and higher copper grades in concentrates, while the recovery rate obtained with 200 g/t was the highest of all investigated collectors and dosages along with high yield and lower copper grade so it was also used in the continuation of the research.
The mixture of SIPX and MX 980 provided high recovery rates and yield with both dosages, 100 g/t SIPX + 40 g/t MX 980 and 100 g/t SIPX + 100 g/t MX 980 (Figure 3d). In the case of the mixture SIPX and TC 1000, recovery rate was slightly lower with the dosage 100 g/t SIPX + 40 g/t TC 1000 (Figure 3e). The further experimental research was continued with the dosage 100 g/t of SIPX and 100 g/t of thionocarbamate (MX 980 and TC 1000) for both mixtures.

3.4.2. Fineness of Grinding

In the second series of flotation tests, it was investigated how the grinding fineness, i.e., the content of grain size < 0.074 mm, influences the recovery rate, yield, and copper grade in concentrate. The results of the second series of testing are shown in Figure 4.
As it can be seen from Figure 4, the increase of grinding fineness, i.e., the content of grain size < 0.074 mm resulted in the increase of recovery rates for all investigated collectors and their mixtures. Grinding products with 50% of grain size < 0.074 mm (Figure 4a) provided concentrates with higher copper grades. The reason for this could be that the share of liberated particles was lower due to lower grinding fineness. On the other side, the recovery of liberated particles in concentrates was higher compared to middlings, which floated in much lesser extent, causing the recovery rates to be lower and copper grades higher than in the other experiments in this series of testing.
The increase of grinding fineness, from 50% to 70% of grain size < 0.074 mm (Figure 4b) resulted in the increase of recovery rates and yield, and decrease of copper grades for all investigated collectors and their mixtures. The finer grinding increased the liberation of copper bearing particles but also the average size of middlings was lower allowing their better flotation. This can be seen from the values of the yield which are approximately 8–10% higher in average for all collectors except for the mixture of SIPX and TC 1000.
Flotation recovery rates and yield continued to grow with the further increase of grinding fineness. Recovery rates at 90% of grain size < 0.074 mm (Figure 4c) were higher for all collectors and mixtures compared to 50% and 70% < 0.074 mm. The lowest recovery was obtained with MX 980, which only proves the tendencies from previous experiments conducted in the first and second series of the study. High yield and low copper grades can indicate that the material was overgrinded and that middlings with smaller portions of copper (less than 10%) were floated, as well as tailings particles which were carried out into the concentrate.

3.4.3. Pulps’ pH

The purpose of the third series of experiments was to investigate the influence of pulps’ pH on copper recovery rates, yield and copper grades for all collectors and their mixtures that were the subject of the study. The results of this series of experiments are shown in Figure 5.
From Figure 5, it can be seen that the increase in pulps’ pH had a positive effect of copper recovery rates for all collectors and their mixtures. At pH 8 (Figure 5a), recovery rates ranged around 91–92%, except for MX 980, whose recovery rate was 87.90% again showing the same tendency as in previous experiments. However, the increase in pulps’ pH had a positive impact on recovery of copper even for collector MX 980. Increasing pulps’ pH from 8 to 10 (Figure 5b) led to increasing the recovery rates and yield for all collectors and mixtures, while the copper grades slightly decreased except for SIPX, whose decrease in a copper grade was the highest, around 4.5%. The further increase from pH 10 to pH 12 (Figure 5c) additionally increased recovery rates for all collectors and mixtures. The highest recovery rate was obtained with MX 980, 96.06%, but the other collectors and their mixtures also provided high recovery rates from 94.52% (TC 1000) to 96.02% (SIPX + MX 980).

3.4.4. Flotation Kinetics

In order to determine the optimal flotation time, flotation kinetics experiments were carried out for all collectors and mixtures in the fourth series of testing. Recovery rates and copper grades in concentrate were monitored, and the results of the experiments are presented in diagrams in Figure 6.
As it can be seen from Figure 6, all collectors and mixtures have similar tendencies regarding flotation kinetics. The highest recovery was obtained with TC 1000 (94.58%), while the lowest was with SIBX (88.20%). In the first few minutes of the flotation, most of the process occurs. Recovery rates are over 80% for all collectors after 10 min of flotation, and, in the next 30 min, the increase is approximately 8%.
On the other side, copper grades in concentrates showed the opposite tendency. The copper grade in concentrate obtained with SIBX was the highest (5.77%), and the grade in concentrate with TC 1000 was the lowest (4.30%). The biggest decrease in copper grade after the 10th minute of flotation was in concentrate with SIBX, from 13.67% to 5.77%.
Bearing everything in mind, it can be said that the optimal flotation time is between 20 and 30 min, depending on an applied collector.

3.4.5. Statistical Analysis

The results obtained in experimental research were statistically analysed in order to have a better prospective on how some of the investigated parameters influence flotation indicators, recovery, copper grade and yield. Mean values of recovery, copper grade and yield for each collector and mixture were calculated and then the obtained results were observed and compared with the mean values. The results of the statistical analysis were presented in Figure 7. The influence of the collector dosages, pulps’ pH and grinding fineness on recovery, yield and copper grade in the flotation of smelter slag is given for different collector types: SIPX (Figure 7a), MX 980 (Figure 7b), TC 1000 (Figure 7c), mixture of SIPX and MX 980 (Figure 7d), and mixture of SIPX and TC 1000 (Figure 7e). The dashed line represents the mean value for each flotation indicator.
Based on the analysis of the deviations between each data point for different experimental set up and mean values for recovery, yield and copper grade for different types of collectors, no changes for copper grade in the case of collector’s mixtures can be seen in comparison to a single collector type.
There is a noticeable increase in recovery and yield with collector dosage, pH and grinding fineness growth. The largest deviations can be seen on every graph for the yield indicator for each experimental set up. It is interesting that there is symmetrical distribution of the results for all three indicators with different set up of experimental values for dosage, pH, and grinding fineness except for the TC 1000 collector–middle section (Figure 7c).
In conclusion, it could be addressed that there is no serious deviation with respect to mean values for each indicator, which means that experimental data are quite accurate.

4. Conclusions

Smelter slag as a by-product of pyrometallurgical processing of copper concentrates contains large amounts of copper and other valuable metals that could be recovered. Flotation is one of the processes used for recovery of copper and other metals from copper slag. Collectors play an important role in performance of flotation. Xanthates are most commonly used collectors in sulphide mineral flotation. However, thionocarbamates can be also successfully used for the flotation of copper from smelter slag, alone or in a combination with xanthates. The results of the experimental research conducted with two thionocarbamates (MX 980 and TC 1000) and their mixtures with SIPX showed good copper recovery and satisfactory copper grades in concentrates. Smaller dosages of thionocarbamates (40 g/t) indicated better selectivity, i.e., high copper grades in concentrates with low yield, and by increasing the dosages, copper grades decreased and yield and recovery have increased. The increase of grinding fineness had a positive impact on flotation indicators, recovery rate, copper grade and yield, up to some point; thus, it is necessary to take precaution not to overgrind the material. Pulps’ pH had an influence especially for MX 980, whose recovery rates increased with the increase of pH from 8 to 10 (12). Finally, flotation kinetics with TC 1000 was the fastest, i.e., recovery rate after 20 min of flotation was over 91%, while recoveries obtained with other collectors were a few percentage points lower.

Author Contributions

Conceptualization, Z.Š. and J.S.; methodology, Z.Š. and M.Đ.; software, D.U., N.A. and S.M.; investigation, M.Đ. and N.Ž.; resources, M.Đ. and N.Ž.; data curation, M.Đ. and N.Ž.; writing—original draft preparation, Z.Š., D.U. and J.S.; writing—review and editing, Z.Š., D.U., N.A. and J.S.; supervision, Z.Š. and J.S. All authors have read and agreed to the published version of the manuscript.

Funding

Ministry of Education, Science and Technological Development of the Republic of Serbia: contract numbers 451-03-68/2022-14/200131 and 451-03-68/2022-14/200052.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors would like to acknowledge the Ministry of Education, Science and Technological Development of the Republic of Serbia for the financial support of scientific research at the University of Belgrade, Technical Faculty in Bor and Mining and Metallurgy Institute Bor.

Conflicts of Interest

The authors declare no conflict of interest.

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Metals 12 00832 g001 550
Figure 1. XRD pattern of smelter slag.
Figure 1. XRD pattern of smelter slag.
Metals 12 00832 g001
Metals 12 00832 g002 550
Figure 2. SEM-EDS analysis of the smelter slag sample.
Figure 2. SEM-EDS analysis of the smelter slag sample.
Metals 12 00832 g002
Metals 12 00832 g003a 550Metals 12 00832 g003b 550
Figure 3. The influence of collector type and dosages on smelter slag flotation indicators (Cu grade, yield and recovery): (a) SIPX; (b) MX 980; (c) TC 1000; (d) mixture SIPX and MX 980; (e) mixture SIPX and TC 1000.
Figure 3. The influence of collector type and dosages on smelter slag flotation indicators (Cu grade, yield and recovery): (a) SIPX; (b) MX 980; (c) TC 1000; (d) mixture SIPX and MX 980; (e) mixture SIPX and TC 1000.
Metals 12 00832 g003aMetals 12 00832 g003b
Metals 12 00832 g004 550
Figure 4. The influence of grinding fineness on Cu grade, yield and recovery in the flotation of smelter slag with different flotation collectors: (a) 50% < 0.074 mm; (b) 70% < 0.074 mm; (c) 90% < 0.074 mm.
Figure 4. The influence of grinding fineness on Cu grade, yield and recovery in the flotation of smelter slag with different flotation collectors: (a) 50% < 0.074 mm; (b) 70% < 0.074 mm; (c) 90% < 0.074 mm.
Metals 12 00832 g004
Metals 12 00832 g005a 550Metals 12 00832 g005b 550
Figure 5. The influence of the pulps’ pH on Cu grade, yield and recovery in the flotation of smelter slag with different flotation collectors: (a) pH 8; (b) pH 10; (c) pH 12.
Figure 5. The influence of the pulps’ pH on Cu grade, yield and recovery in the flotation of smelter slag with different flotation collectors: (a) pH 8; (b) pH 10; (c) pH 12.
Metals 12 00832 g005aMetals 12 00832 g005b
Metals 12 00832 g006 550
Figure 6. Flotation kinetics for investigated collectors (SIBX, MX 980 and TC 1000) and their mixtures (SIBX + MX 980 and SIBX + TC 1000): (a) recovery; (b) copper grades in concentrates.
Figure 6. Flotation kinetics for investigated collectors (SIBX, MX 980 and TC 1000) and their mixtures (SIBX + MX 980 and SIBX + TC 1000): (a) recovery; (b) copper grades in concentrates.
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Metals 12 00832 g007a 550Metals 12 00832 g007b 550
Figure 7. Statistical analysis of influence of collector dosage, pulps’ pH and grinding fineness on recovery, yield and copper grade for different collector types: (a) SIPX; (b) MX 980; (c) TC 1000; (d) mixture of SIPX and MX 980; (e) mixture of SIPX and TC 1000.
Figure 7. Statistical analysis of influence of collector dosage, pulps’ pH and grinding fineness on recovery, yield and copper grade for different collector types: (a) SIPX; (b) MX 980; (c) TC 1000; (d) mixture of SIPX and MX 980; (e) mixture of SIPX and TC 1000.
Metals 12 00832 g007aMetals 12 00832 g007b
Table
Table 1. Chemical composition of the smelter slag sample.
Table 1. Chemical composition of the smelter slag sample.
Element/CompoundContent, (%) (g/t)
Cu3.56
Cusulph.2.62
Cuox0.94
Fe40.63
S1.21
SiO228.34
Al2O34.88
Au* 0.58
Ag* 11.30
* in g/t.
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Štirbanović, Z.; Urošević, D.; Đorđević, M.; Sokolović, J.; Aksić, N.; Živadinović, N.; Milutinović, S. Application of Thionocarbamates in Copper Slag Flotation. Metals 2022, 12, 832. https://doi.org/10.3390/met12050832

AMA Style

Štirbanović Z, Urošević D, Đorđević M, Sokolović J, Aksić N, Živadinović N, Milutinović S. Application of Thionocarbamates in Copper Slag Flotation. Metals. 2022; 12(5):832. https://doi.org/10.3390/met12050832

Chicago/Turabian Style

Štirbanović, Zoran, Daniela Urošević, Milica Đorđević, Jovica Sokolović, Nemanja Aksić, Novka Živadinović, and Sandra Milutinović. 2022. "Application of Thionocarbamates in Copper Slag Flotation" Metals 12, no. 5: 832. https://doi.org/10.3390/met12050832

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