Research on the Combined Inhibition of Sodium Sulfide and Sodium Thioglycollate for the Flotation Separation of Chalcopyrite and Molybdenite

Abstract

Molybdenite and chalcopyrite closely coexist and have good natural floatability. During the Cu-Mo separation process, it is necessary to enhance the inhibition of chalcopyrite to reduce its influence on molybdenite. In this paper, a combined inhibitor, sodium thioglycollate (HSCH₂COONa) and sodium sulfide (Na₂S), with a molar ratio of 2:1, was obtained through pure mineral flotation experiments. It could reduce the impact on molybdenite while maintaining a good inhibitory effect on chalcopyrite. In the artificial mixed minerals test, the use of the combined inhibitor (80 mg/L) can achieve good indicators with Mo grade and recovery rate of 54.34% and 88.12%, respectively, and Cu grade of 2.15%. The contact angle test shows that the combined inhibitor can significantly reduce the wettability of the chalcopyrite surface while having a relatively small effect on molybdenite. The infrared spectroscopy and SEM-EDS energy spectrum indicated that the combined inhibitor C = O and S-H groups underwent chemical reactions on the surface of chalcopyrite and squeezed out kerosene on the surface of chalcopyrite. Molecular dynamics simulations indicate that the HS⁻, S²⁻, and HSCH₂COO⁻ components in the combined inhibitor are more likely to act on the surface of chalcopyrite, exerting an enhanced inhibitory effect on chalcopyrite.

1. Introduction

Molybdenum features a high melting point, high strength, high hardness, and excellent mechanical properties. Moreover, it can maintain high strength and hardness at high temperatures, making it an important metal raw material in the metallurgical industry [1]. Molybdenum resources rarely exist in the form of single deposits. They often coexist with copper to form porphyry metal deposits. The mineral composition is mainly chalcopyrite and molybdenite; the gangue minerals include quartz, mica, talc, feldspar, etc. With the continuous mining of primary ores, the characteristics of molybdenum resources being poor, fine, and diverse have become increasingly prominent, and their selectivity has been constantly declining [2,3].

In the Cu-Mo separation process, due to the requirement that the copper content in the quality of molybdenum concentrate products should be as low as possible, it is particularly important to adopt copper suppression and molybdenum flotation in the copper-molybdenum separation flotation process to ensure the quality of molybdenum concentrate and enhance the suppression of copper [4,5]. When separating chalcopyrite and molybdenite through flotation, suppressing the flotation of chalcopyrite to favor molybdenite is one of the most common process approaches in mineral processing [6,7,8]. Inhibitors for chalcopyrite are divided into two categories: inorganic and organic [9,10].

The inorganic inhibitor Na₂S primarily relies on the HS⁻ produced through hydrolysis to suppress chalcopyrite. Specifically, HS⁻ reduces dithiophosphate to xanthate ions, which detach from the mineral surface. Simultaneously, HS⁻ adsorbs onto the surface of chalcopyrite, forming a hydrophilic film and thus inhibiting the mineral [11]. The inhibition mechanism of NaHS is the same as that of Na₂S, and NaHS can function directly without hydrolysis. When air is blown in, molybdenite will adsorb and catalytically oxidize NaHS, resulting in excessive reagent dosage in the actual flotation process [12]. Sodium thiosulfate (Na₂S₂O₃) is a common thiosulfate with strong reducing properties and good reactivity with metal ions. YANG et al. found that S₂O₃²⁻ can be physically adsorbed on the surface of chalcopyrite, and some Cu²⁺ will complex with S₂O₃²⁻ to form various unstable hydrophilic compounds, significantly reducing its surface potential and hydrophobicity [13]. The free type cyanide, sodium cyanide, is a commonly used inhibitor for chalcopyrite [14]. The cyanide ions (CN⁻) produced by the dissolution of sodium cyanide in water can spontaneously adsorb onto the surface of chalcopyrite and react with the Fe and Cu atoms on the surface to form iron/copper-cyanide complexes, thereby changing the surface potential of the mineral, reducing the electrochemical activity of the chalcopyrite surface, and preventing the adsorption and oxidation of chalcanthite on the chalcopyrite surface, thus preventing the chalcopyrite from being collected and floating [15].

The organic inhibitors mainly include thiol compounds, thiourea compounds, carboxylic acid compounds, etc. [16]. The thiol carboxylic acid (HS-R-COOH) takes advantage of the mineral affinity and reducing property of -SH to act on the surface of chalcopyrite, forming a layer of thiol acetate ions that desorb the collectors adsorbed on the surface of chalcopyrite. Meanwhile, the thiol carboxylic acids adsorbed on the mineral surface generate disulfide glycine, whose hydrophilic group -COOH extends into water, making chalcopyrite more hydrophilic [17]. In the study of thiourea compounds, WANG et al. investigated the effect of 2-thiourea on the flotation separation of copper sulfide molybdenum ore, and ultimately obtained molybdenum concentrate with a MoS₂ content of 82.35% and a recovery rate of 83.41% [18]. The carboxylic acid reagents mainly include 3-Rodanin-3-acetic acid (3-Rd), carboxymethyl thio-dimethyl sodium, and bis (carboxymethyl) thio-carbonate disodium, etc. [19,20,21]. They mainly rely on the negatively charged carboxylic acid group (-COO⁻) and the thio-carbonate group (-CSS⁻) to chemically adsorb onto the Cu and Fe sites on the surface of chalcopyrite, generating metal chelate compounds to enhance the hydrophilicity of copper.

In the actual flotation separation of chalcopyrite and molybdenite, the effect achieved by using a single inhibitor alone is limited. When two or more reagents are used in combination, better results will be achieved. The combined inhibitor is generally an inorganic inhibitor plus an organic inhibitor. By taking into account the different properties of the two, the inorganic inhibitor is used to desorb the xanthate collector on the surface of chalcopyrite, and organic inhibitors adsorb on the surface of chalcopyrite to form hydrophilic films. The latest research indicates that the combined sodium metabisulfite and Ca(OH)₂ as flotation inhibitors for chalcopyrite, the high-concentration combined inhibitor would react with xanthate, reducing the adsorption concentration of the collector on the surface of chalcopyrite and promoting the formation of hydrophilic substances (Fe₂(SO₄)₃, FeOOH, and Fe₂O₃) on the surface of chalcopyrite [22]. Research shows that the combined use of disodium trisulfate, DCMT, and Knox reagent generates HS⁻ as a desorbed collector on the mineral surface through hydrolysis, while the polar group -CSS⁻ adsorbs onto the surface of chalcopyrite, and the polar group -COO⁻ at the other end extends into the water, making chalcopyrite hydrophilic [23]. Although a large amount of research has been conducted on the inhibitors for the copper-molybdenum separation process, in practical field applications, due to the cost and usage effect of the reagents, sodium sulfide and sodium thioglycollate are the most commonly used copper inhibitors. However, during use, with the increase in the amount of the inhibitor, there is also an inhibitory effect on the flotation of molybdenite.

Therefore, this paper conducts a single-mineral test to study the floatability rules of molybdenite and chalcopyrite under the conditions of Na₂S and HSCH₂COONa. Through single-mineral and artificial mixed minerals, an optimal combination inhibitor ratio is obtained, which can reduce the impact on molybdenite while maintaining a good inhibitory effect on chalcopyrite. Moreover, the interaction mechanism of the combined reagents on the surfaces of molybdenite and chalcopyrite is analyzed using contact angle, infrared spectroscopy, SEM-EDS energy spectrum, and molecular dynamics simulation.

2. Materials and Methods

2.1. Samples and Reagents

The molybdenite and chalcopyrite used as pure minerals in this study were taken from lumps of a molybdenum mine in Heilongjiang Province. The samples were processed through crushing, impurity removal, manual selection, grinding, and sieving to prepare samples with particle sizes ranging from 0.045 mm to 0.074 mm. The XRD results of the samples are shown in Figure 1. The chemical element analysis is shown in

Table 1. Multi-element analysis of pure minerals.

Minerals	Chemical Formula	Theoretical Content /%	Cu /%	TFe /%	S /%	Mo /%	Purity /%
molybdenite	MoS2	59.94 (Mo cal.)	——	——	42.06	58.28	97.23
chalcopyrite	CuFeS2	34.56 (Cu cal.)	32.32	28.68	32.65	——	93.52

. Based on the theoretical contents of Mo and Cu in molybdenite and chalcopyrite, their purities are 97.23% and 93.52%, respectively, which meet the requirements of pure mineral tests.

The inhibitors were anhydrous sodium sulfide (Na₂S) and sodium thioglycollate (HSCH₂COONa), the collector was kerosene, the foaming agent was MIBC (C₆H₁₄O), the pH adjuster was HCl and NaOH, all of which were chemically pure (Kemiou Scientiffc Co., Ltd., Tianjin, China), and the test water was deionized water.

2.2. Pure Mineral Flotation Test

The pure mineral flotation test was carried out in a hanging cell flotation machine of model XFGC-II (Jilin Jitan Machinery Co., Ltd, Changchun, China), with a main shaft speed of 1600 rpm. For the single-mineral and artificial mixed-ore (molybdenite and chalcopyrite mass ratio 2:1) test, 2 g of pure mineral and 50 mL of deionized water are added each time. The slurry is adjusted for 3 min, and the pH value is adjusted with HCl and NaOH. After the pH value stabilizes, the regulator, collector, and foaming agent are added according to the dosage of the reagent. After each addition of the reagent, the mixture is stirred for 3 min, and the flotation is scraped for 3 min. The foam is scraped out, and the products in the tank are dried and weighed, and the recovery rate is calculated. The recovery rate of the artificially mixed ore is determined by measuring the yield and grade.

2.3. Contact Angle Test

After the samples were treated with the reagent and dried at low temperature, 2 g of the samples were taken each time and pressed into thin slices with a tablet press at 20 Mpa for 1 min to obtain smooth thin slices. Water was suspended on the JC2000A contact angle measuring instrument (Shanghai Zhongchen Digital Technic Apparatus Co., Ltd., Shanghai, China), and photos were taken by a high-speed camera. The contact angle of the minerals was measured three times and the average integer value was recorded. The experimental environment for the operation was 25 °C.

2.4. Sem-Eds Test

The test samples were dried at room temperature for 24 h to remove the moisture in the samples, and gold spraying treatment was carried out. The surface morphology of the minerals in a specific area was observed under the Mode S-3400N scanning electron microscope (Hitachi High-Tech Corporation, Tokyo, Japan), and the elemental composition of the mineral in this area was analyzed in combination with EDS energy spectrum.

2.5. Infrared Spectroscopy Test

Infrared spectroscopy was used to analyze the changes in minerals before and after the action of reagents. Each time, 2 g of mineral samples were taken, ground with agate to less than 5 μm, placed in the flotation cell, and 35 mL of deionized water was added. The samples were stirred, reagents were added, and the slurry was adjusted according to the flotation test conditions. After full action, solid–liquid separation was achieved. The samples were washed three times with deionized water of the same pH value, and the obtained mineral samples were dried at 40 °C. The test was conducted using KBr tablets with a measurement range of 4000 to 400 cm⁻¹.

2.6. Molecular Dynamics Simulation

In this study, the Material Studio 2023 software (version 23.1.0) was used for molecular dynamics simulation to obtain the action energies of different agents on the surfaces of chalcopyrite and chalcocite, and the crystal cells were constructed through the Visualizer module. The main dissociation planes of the inhibitor ions with chalcopyrite (001) and molybdenite (100) were calculated and optimized by using the Dmol3 module LDA-PWC function, and the interaction model between the minerals and the inhibitor system was established by using the amorphous cell module. Molecular dynamics simulation of the model was conducted using the Forcite module. At a temperature of 298 K, the dynamic characteristics of the NVT-integrated system were simulated using the Nose thermostat. The duration of the simulation is 1000 ps, and the time iteration is 1 fs. During the simulation, the universal force field was adopted to obtain the most stable configuration of the interaction between the reagent and the mineral surface, and the interaction energy was calculated as shown in Equation (1).

E_int = E_{mineral- inhibitor} − (E _inhibitor + E_mineral)

(1)

Among them, E_{mineral- inhibitor}, E _inhibitor, and E_mineral, respectively, represent the total energy of mineral surface-agent, agent, and mineral surface after molecular dynamics simulation. The more negative the interaction energy ΔE value is, the stronger the interaction energy between the mineral surface and the reagent is, and the easier it is for the flotation reagent to be adsorbed on this surface.

3. Results and Discussion

3.1. Floatability of Chalcopyrite and Molybdenite

The floatability of chalcopyrite and molybdenite was obtained through the single-mineral floatability test, as shown in Figure 2. According to Figure 2a, molybdenite exhibits good floatability at pH values ranging from 2 to 12, while chalcopyrite shows good floatability at pH values ranging from 6 to 9; the floatability of molybdenite is better than that of chalcopyrite. It can be seen from Figure 2b that with the increase in kerosene dosage, the recovery of chalcopyrite shows an increasing trend, while molybdenite can maintain a relatively high recovery at a dosage of 30 mg/L. The effects of two inhibitors, Na₂S and HSCH₂COONa, on the floatability of chalcopyrite and molybdenite are shown in Figure 2c. The inhibitory effect on chalcopyrite increases with the rise in pH, while the effect on molybdenite is not significant. As shown in Figure 2d, with the increase in the dosage of the two inhibitors, the inhibitory effect of chalcopyrite becomes more significant, and the inhibitory effect of Na₂S is superior to that of HSCH₂COONa. Meanwhile, as the dosage of Na₂S increases, the recovery of molybdenite decreases, while HSCH₂COONa has almost no effect on molybdenite.

Through the above experiments, it is concluded that the dosage of kerosene and pH conditions should be controlled during the copper-molybdenum separation process. By comparing the two inhibitors, Na₂S has a stronger inhibitory effect on chalcopyrite, but excessive use will inhibit molybdenite. However, an increase in the dosage of HSCH₂COONa has a weaker inhibitory effect on molybdenite. Therefore, the combined use of the two inhibitors is considered. To achieve better inhibition of chalcopyrite during the copper-molybdenum separation process without affecting the recovery of molybdenite.

3.2. Effects of Combined Inhibitors on the Floatability of Chalcopyrite and Molybdenite

Based on the inhibitory characteristics of Na₂S and HSCH₂COONa on the floatability of chalcopyrite and molybdenite mentioned above, the law of the combined use of Na₂S and HSCH₂COONa on the floatability of molybdenite and chalcopyrite was explored as shown in Figure 3, and the following findings were obtained.

As shown in Figure 3a, when the molar ratio of HSCH₂COONa to Na₂S is 2:1, an effect of 1 + 1 > 2 can be achieved. That is, the combined use of HSCH₂COONa and a small amount of Na₂S can not only ensure a good molybdenum recovery rate but also have a significant inhibitory effect on chalcopyrite. Therefore, the combined use of HSCH₂COONa and Na₂S with a molar ratio of 2:1 was taken as the research object, which is hereinafter referred to as the combined inhibitor. It can be seen from Figure 3b that the combined inhibitor has a strong inhibitory effect on chalcopyrite at pH 9 to 12. According to Figure 3c, when the dosage of the combined inhibitor is 80 mg, it can not only reduce the inhibition of molybdenite but also maintain a good inhibition effect on chalcopyrite, which is more effective than using it alone. According to the performance of the combined inhibitor in the artificial mixed ore test results of molybdenite and chalcopyrite in Figure 3d, as the dosage of the combination inhibitor increases, the Cu-Mo separation effect becomes significant. When the dosage was 80 mg/L, good indicators could be obtained, with the Mo grade and recovery in the concentrate being 54.34% and 88.12%, respectively, and the Cu grade being 2.15%.

3.3. Contact Angle Measurement

The contact angle is an important parameter for measuring the wettability of a liquid on a solid surface. The size of the contact angle can reflect the surface wettability of molybdenite and chalcopyrite under different reagent conditions, as shown in Figure 4 and Figure 5.

Figure 4a shows that the natural contact angle of molybdenite without chemical treatment is 42°. After being treated with kerosene, the contact angle significantly increases to 73°, as shown in Figure 4b. The contact angle of molybdenite after being treated with kerosene and then with HSCH₂COONa does not change much, as shown in Figure 4c, indicating that the effect of HSCH₂COONa on the surface of molybdenite is weak. Figure 4d shows the contact angle of molybdenite after it was first treated with kerosene and then with Na₂S. It can be found that the contact angle decreases to 53°, indicating that Na₂S has a certain inhibitory effect on molybdenite.

Figure 4e shows the contact angle of molybdenite after being treated with kerosene and then with a combined inhibitor. It can be observed that the change in the contact angle is not significant, indicating that the use of a combined inhibitor can weaken the inhibitory effect of Na₂S on molybdenite.

Figure 5a shows that the natural contact angle of chalcopyrite without chemical treatment is 34°, and after being treated with kerosene, the contact angle increases to 65°, as shown in Figure 5b. The contact angle of chalcopyrite after being treated with kerosene and then with HSCH₂COONa becomes 15°, as shown in Figure 5c, indicating that HSCH₂COONa has a significant effect on chalcopyrite. The contact angle of chalcopyrite after being treated with kerosene and then with Na₂S is 8°, as shown in Figure 5d, indicating that Na₂S has a strong inhibitory effect on chalcopyrite. Figure 5e shows the contact angle of chalcopyrite after being treated with kerosene. It can be observed that the contact angle changes significantly, indicating that the combined inhibitor has a significant inhibitory effect on chalcopyrite.

3.4. Infrared Spectroscopy and Sem-Eds Analysis

Figure 6a shows the infrared spectra of the collector kerosene, inhibitors HSCH₂COONa and Na₂S, respectively. The strong absorption peaks at 2957.6 cm⁻¹, 2928.6 cm⁻¹, and 2855.9 cm⁻¹ in the infrared spectrum of kerosene are the C-H stretching vibrations of -CH₃ and -CH₂ in alkanes. The absorption peaks at 1460.4 cm⁻¹ and 1380.2 cm⁻¹ are the bending vibration peaks of -CH₃. In the infrared spectrum of HSCH₂COONa, the characteristic peak at 1660 cm⁻¹ is the carboxylic acid carbonyl C = O peak, the peak at 1231.6 cm⁻¹ is the C-O-H stretching vibration of the carboxylic acid, the peak at 1400.6 cm⁻¹ is the in-plane bending vibration of C-O-H, and the peak at 920.4 cm⁻¹ is the plane bending. The peak at 2550.2 cm⁻¹ is an S-H stretching vibration. The characteristic peak positions of Na₂S are 3610.3 cm⁻¹, 1658.3 cm⁻¹, 1378 cm⁻¹, and 1121.3 cm⁻¹, respectively.

Figure 6b shows the infrared spectra of molybdenite with kerosene and combined inhibitors, respectively. Among the characteristic peaks of the infrared spectrum of molybdenite under the action of kerosene, 3413.3 cm⁻¹ is the stretching vibration peak of OH, which may be caused by mineral oxidation. The strong absorption peak at 2856.1 cm⁻¹ is the stretching vibration of C-H in kerosene alkanes. The absorption peak at 1384.2 cm⁻¹ is the bending vibration peak of -CH₃. The characteristic peak positions of the infrared spectrum after the action of the combined inhibitor remained basically unchanged, and no new peaks appeared, indicating that the combined inhibitor had no effect on the kerosene acting on the surface of molybdenite, and no characteristic peaks of the combined inhibitor were found either, suggesting that the agent might not have acted on the surface of molybdenite.

Figure 6c shows the infrared spectra of chalcopyrite with kerosene and combined suppression, respectively. Under the action of kerosene, the characteristic peak of the infrared spectrum of chalcopyrite is the strong absorption peak at 2856.5 cm⁻¹, which is the C-H stretching vibration in kerosene alkanes, and the absorption peak at 1385.6 cm⁻¹ is the bending vibration peak of -CH₃. After the action of the combined inhibitor, the bending vibration peaks of -CH₃ at 2856.5 cm⁻¹ and 1385.6 cm⁻¹ of C-H on the surface of chalcopyrite disappeared after the action of kerosene, and the characteristic Na₂S peaks of 3610.5 cm⁻¹, 1668.6 cm⁻¹, and 1121.3 cm⁻¹ appeared. The S-H stretching vibration frequency peak at 2550.6 cm⁻¹, the carboxylic acid carbonyl C = O peak at 1660.9 cm⁻¹, and the in-plane bending vibration peak of C-O-H at 1400.7 cm⁻¹ in HSCH₂COONa indicate that the combined inhibitor acts on the surface of chalcopyrite, reacting with C = O and S-H groups on the surface of chalcopyrite, and squeezes out the kerosene on the surface of the chalcopyrite.

The SEM-EDS analysis of molybdenite and chalcopyrite before and after the action of the reagent is shown in Figure 7. Figure 7a is the pure mineral of molybdenite, and the main elements on its surface are Mo and S. The presence of the O element may be caused by slight oxidation on the surface. Figure 7b shows that after the action of kerosene, the changes in Mo and S elements are not significant, and the C element has increased on the surface, indicating that kerosene is adsorbed on the surface of molybdenite. Figure 7c shows the action of the combined inhibitor (HSCH₂COONa + Na₂S molar ratio 2:1) on the surface of molybdenite. The S and C elements on the surface remain basically unchanged, indicating that the combined inhibitor basically does not act on the surface of molybdenite. Figure 7d shows pure chalcopyrite minerals, whose surface mainly consists of Cu, S, and Fe elements. The presence of the O element may be due to slight surface oxidation caused by sample treatment. Figure 7e shows that after the action of kerosene, the surface of chalcopyrite has more C elements, indicating that kerosene is adsorbed on the surface of chalcopyrite. Figure 7f shows the combined inhibitor acting on the surface of chalcopyrite. The S and O elements on the surface increase significantly. The S and O elements in the combined inhibitor act on the surface of chalcopyrite, while the C element decreases, indicating that the C element in the originally attached kerosene has been stripped off. This also verified the infrared spectroscopy results mentioned earlier, indicating that the combined agent undergoes a chemical reaction on the surface of chalcopyrite, reducing the adhesion of kerosene.

3.5. Molecular Dynamics Simulation Experiment

The inhibitors Na₂S and HSCH₂COONa studied in this paper will hydrolyze in an alkaline pulp environment. Their main components are HS⁻, S²⁻, and HSCH₂COO⁻. The adsorption energy of the main components of the inhibitors on the crystal planes of chalcopyrite (001) and molybdenite (100) was analyzed by molecular dynamics. The interaction energy calculation between the molybdenite and chalcopyrite surfaces and the reagent ions is shown in

Table 2. Calculation of interaction energy between molybdenite (100) and chalcopyrite (001) surfaces and inhibitor components.

Crystal Surface	Components	Emineral/inhibitor	Emineral	E inhibitor	Eint (KJ/mol)
molybdenite (100)	HS−	−4523.47	−3795.55	148.26	−876.18
	S2−	−5376.51	−4316.44	−135.27	−924.80
	HSCH2COO−	−4894.29	−3951.76	−663.46	−279.07
chalcopyrite (001)	HS−	−4709.63	−3976.61	348.23	−1081.25
	S2−	−5047.69	−3956.42	−35.17	−1056.10
	HSCH2COO−	−5561.57	−4023.03	−1196.21	−342.33

. The stable configurations of the main components of the inhibitor acting on the molybdenite (100) surface and the chalcopyrite (001) surface are, respectively, shown in Figure 8 and Figure 9.

The mutual adsorption energy between the surface of molybdenite and chalcopyrite and the ions of the reagent is calculated as shown in Table 2. The main components of the inhibitors Na₂S and HSCH₂COONa are HS⁻, S²⁻, and HSCH₂COO⁻, and their action energy in chalcopyrite is lower than that in molybdenite. The concentrations were −205.07 KJ/mol, −131.30 KJ/mol, and −63.26 KJ/mol, respectively, indicating that the inhibitor components were more easily adsorbed on the surface of chalcopyrite.

The adsorption energies of HS⁻ and S²⁻ produced by the hydrolysis of Na₂S acting on the surface of chalcopyrite are −1081.25 KJ/mol and −1056.10 KJ/mol, respectively, which are lower than those of HSCH₂COO⁻ produced by the hydrolysis of HSCH₂COONa acting on the surface of chalcopyrite. It is indicated that the HS⁻ and S²⁻ components of Na₂S are more likely to adsorb on the surface of chalcopyrite in solution to produce inhibitory effects. This is also the reason why the inhibitory effect of Na₂S on chalcopyrite is better than that of HSCH₂COONa.

Therefore, the combined inhibitor of HSCH₂COONa and Na₂S (molar ratio 2:1), on the one hand, enhances the inhibition of chalcopyrite through a small amount of Na₂S, and on the other hand, the main component of HSCH₂COONa weakens the effect of Na₂S on molybdenite, achieving a better inhibition effect of chalcopyrite in the Cu-Mo separation process.

4. Conclusions

(1)

Through single-mineral flotation tests, it was concluded that the floatability of molybdenite in the kerosene system is superior to that of chalcopyrite. When the dosage of the inhibitor increases, Na₂S will have a certain inhibitory effect on molybdenite, while HSCH₂COONa has a relatively small influence. The two inhibitors have significant inhibitory effects on chalcopyrite, and the inhibitory ability of Na₂S is stronger than that of HSCH₂COONa.

(2)

When the dosage of the combined inhibitor of HSCH₂COONa and Na₂S (molar ratio 2:1) is 80 mg, its effect is better than that of using it alone. It can not only reduce the inhibition of molybdenite but also maintain a good inhibition effect on chalcopyrite. In the artificial mixed ore test, good indicators can be obtained in the molybdenum concentrate with a Mo grade of 54.34%, a recovery rate of 88.12%, and a Cu grade of 2.15%.

(3)

The contact angle test shows that the combined inhibitor can significantly reduce the wettability of the chalcopyrite surface while having a relatively small effect on molybdenite. Infrared spectroscopy and SEM-EDS energy spectrum indicated that the combined inhibitor C = O and S-H groups underwent chemical reactions on the surface of chalcopyrite and squeezed out kerosene on the surface of chalcopyrite. Molecular dynamics simulations indicate that the HS⁻, S²⁻, and HSCH₂COO⁻ components in the combined inhibitor are more likely to act on the surface of chalcopyrite.