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Article

Flotation Separation of Magnesite from Dolomite Using Sodium Silicate Modified with Zinc Sulfate as a Selective Depressant

by
Na Luo
1,2,3,4,*,
Jingyang Shi
1,2,3,4,*,
Baobao Yan
5 and
Xiaoping Wang
1,2,3,4
1
School of Mining and Coal, Inner Mongolia University of Science and Technology, Baotou 014010, China
2
Inner Mongolia Key Laboratory of Mining Engineering, Baotou 014010, China
3
Inner Mongolia Research Center for Coal Safety Mining and Utilization Engineering and Technology, Baotou 014010, China
4
Inner Mongolia Cooperative Innovation Center for Coal Green Mining and Green Utilization, Baotou 014010, China
5
Inner Mongolia Autonomous Region Industrial Technology Innovation Center (Inner Mongolia Autonomous Region Science and Technology Testing and Experimental Center), Hohhot 010010, China
*
Authors to whom correspondence should be addressed.
Minerals 2024, 14(4), 355; https://doi.org/10.3390/min14040355
Submission received: 2 February 2024 / Revised: 19 March 2024 / Accepted: 26 March 2024 / Published: 28 March 2024
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Abstract

:
Flotation separation of magnesite from dolomite in the presence of SSZS (sodium silicate modified with zinc sulfate) as an inhibitor and NaOL (sodium oleate) as a collector has been studied via flotation tests, zeta potential measurements, contact angle measurements, and Fourier transformation infrared spectroscopy analysis (FT-IR). The flotation tests show that NaOL has strong collecting capacity in magnesite and dolomite flotation, so it is difficult to separate two minerals via flotation without inhibitors. SSZS is used as the depressant, which can selectively inhibit dolomite flotation and has little depression effect on magnesite. Zeta potential measurements, contact angle measurements, and FT-IR analysis indicate that SSZS can adsorb strongly onto dolomite’s surface and has a weak adsorption effect on magnesite. The adsorption of SSZS prevents NaOL from acting on the surface of dolomite. On the contrary, because there is little adsorption of SSZS onto magnesite, NaOL can still adsorb onto magnesite’s surface.

Graphical Abstract

1. Introduction

Magnesium is widely used in many fields such as the aerospace, automobile, electronic, war industries as it has the properties of low density, high strength, excellent processing performance, and high impact resistance performance [1,2]. During the past few years, low-grade magnesite was usually left idle or often discarded due to limitations in processing and utilization technologies, resulting in the waste of mineral resources and environmental pollution [3,4]. Magnesite (MgCO3) is the most important magnesium mineral resource and often coexists with calcium gangue minerals such as dolomite and calcite [5,6]. Calcium gangue minerals contained in magnesite can seriously affect the quality of refractory materials. During the melting process, calcium gangue minerals transform into calcium silicate, which may loosen in cooling and cause the refractory materials to collapse [7]. Therefore, it is critical to effectively achieve the separation of magnesite and calcium gangue minerals. After years of research, so far, foam flotation is one of the most effective methods for separating magnesite and calcium gangue minerals.
Dolomite (MgCa(CO3)2) is one of the most common carbonate gangue minerals in magnesite. Due to the similar physical and chemical properties (such as surface wettability and surface charge properties) and crystal structures, it is difficult to separate magnesite from dolomite via flotation. In addition, dissolved components from magnesite and dolomite can also influence flotation separation [8,9,10,11,12].
The common collectors are fatty acids and fatty acid salts which are used in carbonate flotation. Sodium hexametaphosphate, sodium silicate, starch, and carboxymethyl cellulose are common depressants used in carbonate flotation. Fatty acids and fatty acid salts have good collecting performance for most carbonates. And, the above-mentioned depressants not only inhibit gangue minerals but also have a great inhibition on magnesite flotation [13,14,15,16,17]. Although a lot of research has focused on magnesite flotation, the separation of magnesite away from calcium-containing gangue minerals such as dolomite and calcite remains a challenge. Sodium silicate (water glass) remains the most commonly used depressant in carbonate mineral flotation. In order to improve the selectivity of sodium silicate, metal ions such as Al3+, Pb2+, and Fe3+ have been used to modify sodium silicate in the flotation process. For instance, under neutral and alkaline conditions, a mixture of Al3+ and sodium silicate is effective for the flotation separation of scheelite and calcite [18,19,20]. Zn2+ is a common metal ion that has been used to modify sodium dimethyl dithiocarbamate (SDD) in a copper flotation system. The mixture of Zn2+ and SDD obviously inhibited sphalerite but not chalcopyrite, showing selective flotation separation superior to that of SDD alone [21,22]. Because Zn2+, which was used as a modifier, can enhance the depression effect in sulfide mineral flotation, it is significant to study the effect of Zn2+ modification on carbonate mineral flotation.
In the present study, the flotation separation of magnesite from dolomite using sodium silicate modified with zinc sulfate as the inhibitor and sodium oleate as the collector was investigated. The mechanism of the selective inhibition of dolomite via SSZS was studied through zeta potential measurements, contact angle measurements, and FT-IR analysis.

2. Materials and Methods

2.1. Samples and Reagents

The experimental mineral samples with high purity of magnesite and dolomite were from Liaoning Province, China. The samples of magnesite and dolomite were artificially crushed and dry-ground using an agate mortar. Screening of the −150 μm fraction was used for flotation tests and contact angle measurements. The chemical compositions and the XRD results of magnesite and dolomite samples are shown in Table 1 and Figure 1, respectively. Through calculations, the magnesite and dolomite were shown to have high purities of 99.20% and 98.97%, respectively, which meet the testing requirements.
Sodium oleate (NaOL) was used as the collector. The mixture comprised sodium silicate modified with zinc sulfate (SSZS). The zinc sulfate used in this research was zinc sulfate heptahydrate with a molecular formula of ZnSO4·7H2O. The chemical formula of sodium silicate is Na2O·2.8SiO2. The preparation process of SSZS involved preparing a certain concentration of sodium silicate solution (15 g/L) and zinc sulfate solution (15 g/L) separately, pouring a certain amount of sodium silicate solution into a beaker as needed, then using a pipette to take the required amount of zinc sulfate solution and add it to the beaker containing sodium silicate solution. Keep stirring for 3 min to thoroughly mix the solution. We then poured the prepared solution into a 100 mL volumetric flask, added deionized water to the mark, shook it well, and set it aside for later use. The total mass of sodium silicate and zinc sulfate in a 100 mL volumetric flask is 0.6 g, which means the mass concentration of SSZS is 0.6%. Sodium hydroxide (NaOH) and hydrochloric acid (HCl) were used to adjust the pH value. All the reagents were analytical grade in all experiments. The experimental water was deionized water.

2.2. Methods

2.2.1. XRD Tests

To analyze the phase composition of magnesite and dolomite samples, XRD tests were performed using an X-ray diffractometer; the device model was LabX XRD-6000 (Shimadzu, Kyoto, Japan). Magnesite and dolomite were finely ground to below 5 μm. The scanning rate was set at 2°/min within the range between 10° and 90°. The XRD results of magnesite and dolomite are presented in Figure 1 where it can be seen that both magnesite and dolomite samples have high purity and almost no impurity peaks.

2.2.2. Flotation Tests

Flotation tests of single minerals and artificially mixed samples were performed using an XFG-type agitation flotation machine (Shunze mining and metallurgical machinery manufacturing Co., Ltd., Changsha, China) with a spindle speed of 1600 r/min. In each test, pure minerals (2.0 g) or artificially mixed samples (3.0 g) were added into the flotation cell with 40 mL of deionized water. NaOH or HCl was first added to adjust the pH value of the mineral suspensions. The depressant and collector were added in sequence and agitated for 3 min each. Each flotation time was also 3 min. Froth products and tailings were collected, filtered, dried, and weighed to calculate the flotation recovery for single mineral flotation. For artificially mixed sample flotation tests, froth products and tailings were filtered, dried, weighed, and assayed. The contents of MgO and CaO obtained from the assay were used to calculate the grades and recoveries of magnesite and dolomite. Each experiment was conducted three times, and the average value is given as the final result.

2.2.3. Zeta Potential Analysis

Zeta potentials were performed using a zeta potential analyzer; the device model was Nano-ZS90 (Malvern Instruments Ltd., Malvern, UK). Potassium nitrate (KNO3) was used to maintain the ionic strength at 10−3 mol/L. Magnesite and dolomite were finely ground to below 5 μm. Overall, 20 mg of mineral samples were dispersed into 50 mL of aqueous solution. According to the need, flotation reagents were added in order. The suspension was conditioned for 15 min by agitating it magnetically. The zeta potentials of the minerals were collected three times, separately for each condition, and the average value is given as the final result.

2.2.4. Contact Angle Measurements

Contact angle measurements were conducted through a JC2000A contact angle analyzer (Powereach Instruments, Shanghai, China). Overall, 2 g of single minerals were added to 40 mL of deionized water. According to different conditions, NaOH, SSZS, and NaOL were added in sequence. The solution was magnetically stirred for 3 min for each addition of an agent. Then, the solution was filtered, washed in deionized water, and dried. In total, 1 g of dried single mineral particles were pressed into smooth sheets using the pressing machine for contact angle measurements.

2.2.5. FT-IR Spectra Analysis

The infrared spectrum results were obtained through a Nicolet 740 Fourier transform infrared spectrometer (Thermo Nicolet Co., Madison, WI, USA). The spectral range was 400–4000 cm−1. The mineral samples were mixed with spectroscopic-grade potassium bromide (KBr). For FT-IR analysis, the sample preparation process was divided into the following steps: 1. We ground the pure minerals to below 15 μm using an agate mortar. 2. We added pure minerals (2.0 g) into aqueous solution with a volume of 40 mL. 3. We adjusted the pH value of the solution using NaOH; the time needed to condition the pulp was 5 min. 4. The depressant and collector were added in sequence and conditioned for 10 min each, according to the experimental requirements. 5. The suspension was filtrated and rinsed thoroughly with deionized water three times. 6. The obtained samples were dried in a vacuum-drying oven for 24 h at 40 °C.

3. Results and Discussion

3.1. Flotation Studies

Figure 2 shows the influence of the pH value on the flotation behaviors of magnesite and dolomite using NaOL as the collector. It is obvious that the flotation recoveries of both magnesite and dolomite are higher than 85% in the pH range of 7–12. The high recoveries are attributed to the chemisorptions of NaOL onto magnesite and dolomite surfaces [23]. The results suggest that it is difficult to separate magnesite from dolomite without adding any depressants.
NaOL can collect both magnesite and dolomite effectively over the entire pH range tested. So, adding effective depressants is necessary to separate magnesite and dolomite. From Figure 2, it can be seen that, when the pH value is around 10.5, the flotation recovery of magnesite is about 97.4% and the flotation recovery of dolomite is about 89.3%, with the largest difference occurring between the flotation recoveries of two minerals. Therefore, the pH value is fixed at 10.5 in the flotation tests below. Figure 3 shows the effects of sodium silicate and SSZS (the mass ratio of sodium silicate and zinc sulfate is 1:1) on the flotation behaviors of two minerals. As shown in Figure 3, when sodium silicate is added as the depressant, both magnesite and dolomite are greatly depressed. When the amount of sodium silicate increases, the flotation recoveries of magnesite and dolomite decrease from about 90% to 35.09% and 30.76%, respectively. Sodium silicate does not have selective inhibition on the flotation separation of magnesite from dolomite. When using SSZS as depressant, the flotation recovery of magnesite is above 85% throughout the entire usage range of SSZS and the recovery of dolomite reduces greatly with the increase in SSZS concentration. When the concentration of SSZS is 180 mg/L, the flotation recovery of dolomite decreases to 30.42%. The results illustrate that SSZS has a selective inhibitory effect on magnesite and dolomite and the optimum dosage is 180 mg/L. Thus, it is advantageous for achieving flotation separation of magnesite from dolomite.
The flotation behaviors of magnesite and dolomite were studied using a depressant mixture of sodium silicate and zinc sulfate at different mass ratios. The results are shown in Figure 4. A range of flotation results indicate that the optimum mass ratio of sodium silicate to zinc sulfate to reach the best flotation separation performance is 1:1. Magnesite has a relatively good rate of recovery—79.45%. In contrast, the recovery of dolomite is 47.12%. Compared with the results using sodium silicate as the inhibitor in Figure 3, significant differences in the flotation recoveries of the two minerals imply that the possibility of mineral flotation separation is improved by using 1:1 depressant mixture SSZS.
The results of the flotation test of the pure minerals suggest that it is possible to achieve flotation separation of magnesite from dolomite by inhibiting the latter using SSZS. In order to further study whether SSZS is available for floating magnesite away from dolomite or not, the samples of magnesite and dolomite were mixed using mass ratio of 1:1. The pH value of the slurry was set to 10.5. NaOL and SSZS were added as the collector and the inhibitor, respectively, and the experimental results are listed in Table 2. The original grades of magnesite and dolomite were both 50% in the artificially mixed sample. The results indicate that, without the addition of SSZS, the concentrate grades of magnesite and dolomite are not significantly different from those in the original mixed sample. The flotation separation of two minerals cannot be achieved without adding any depressants. By increasing the dosage of SSZS from 0 mg/L to 180 mg/L, the concentrate grade of magnesite increased from 49.85% to 75.21% and the recovery decreases from 97.39% to 87.20%. The results show that the changing trends of dolomite are different. The concentrate grade of dolomite decreases from 50.15% to 24.79% when increasing the usage of SSZS; the rate of recovery decreases from 97.46% to 29.64%. The above-mentioned results indicate SSZS has a selective depressing effect on the flotation separation of magnesite and dolomite in artificially mixed minerals. Therefore, magnesite can be selectively floated away from dolomite when using SSZS as the depressant.
The modification of sodium silicate occurs when the oligomers of sodium silicate are decomposed by activators such as inorganic acids and multivalent metal salts to produce single-molecule silicic acid. The newly formed single-molecule silicic acid, which has high activity, can be selectively adsorbed onto the target mineral surface to form hydrophilic layers. The commonly used acids are hydrochloric acid and sulfuric acid, and the commonly used metal salts are metal salts containing lead ion, copper ion, aluminum ion, and zinc ion [24,25,26,27].
According to the solution chemistry of flotation, sodium silicate has three existence formats in aqueous solution: SiO2(OH)22−at pH > 12.6, SiO(OH)3− at 9.4 < pH < 12.6, and Si(OH)4 at pH < 9.4 [28]. The pH value of the flotation tests in this paper is at around 10.5, so the dominant form of sodium silicate is SiO(OH)3− in flotation solution. With the addition of zinc sulfate, the following chemical reaction formula started to occur [29]:
Minerals 14 00355 i001
Sodium silicate modified with zinc sulfate forms Zn·2SiO(OH)3, which is a hydrophilic colloid, and is selectively adsorbed onto the dolomite surface. This may be the main reason for achieving the flotation separation of two minerals using SSZS.

3.2. Zeta Potential Analysis

The results of the above flotation tests illustrate that, when using SSZS as the inhibitor, the separation of magnesite from dolomite via flotation can be achieved. In order to research the mechanism of SSZS impacting on the flotation behaviors of magnesite and dolomite, zeta potential measurements, contact angle measurements, and FT-IR analysis were conducted.
The zeta potentials of magnesite and dolomite under the pretreatment of SSZS or not in the presence of NaOL are given in Figure 5. The mineral samples treated using SSZS and NaOL were conditioned with 180 mg/L of SSZS before NaOL addition into the aqueous solution. Then, we put 120 mg/L NaOL into the solution and the zeta potentials were measured. It is clear from Figure 5a that the zeta potential of magnesite in the presence of NaOL has a larger negative shift than that of magnesite; this indicates that NaOL can adsorb onto magnesite’s surface. When adding SSZS earlier than NaOL, the zeta potential of magnesite is similar to that of magnesite in the presence of NaOL. The results demonstrate that the addition of SSZS cannot hold back the adsorption of NaOL onto magnesite’s surface. Figure 5b shows that, compared with the potentiodynamic of dolomite, the zeta potential of dolomite treated with NaOL has a significant negative shift. This result explains that NaOL also can adsorb onto dolomite’s surface. When dolomite is treated with SSZS and NaOL, the zeta potentials shift in a positive direction and the value is close to that of dolomite without adding any reagents. This illustrates that the presence of SSZS can prevent the adsorption of NaOL onto the surface of dolomite. The above zeta potential results explain the flotation test results and they are extremely important for flotation experimental research because using NaOL as the collector to selectively separate magnesite from dolomite is always difficult to realize.

3.3. Contact Angle Measurements

The contact angle results of magnesite and dolomite in the presence and absence of NaOL or SSZS are shown in Table 3. The concentrations of NaOL and SSZS were 120 mg/L and 180 mg/L, respectively, and the pH value was adjusted to about 10.5.
Similar to the results recorded in a previous paper [30], the contact angle of magnesite is 34.8° and that of dolomite is 31.5°. Both minerals have weak hydrophobicity in deionized water. The contact angles of magnesite and dolomite increase to 65.7° and 58.2° after conditioning with NaOL, respectively, showing dramatic hydrophobicity. When adding SSZS earlier than NaOL, the contact angle of magnesite is maintained at 67.4°; however, the contact angle of dolomite decreases to 33.5°. It could be concluded that SSZS increases the difference of floatability between magnesite and dolomite when NaOL is used as the collector. The addition of SSZS almost recovers the hydrophilicity of dolomite, but the magnesite still shows high hydrophobicity in the presence of SSZS. The results of the contact angle measurements conform to the flotation behaviors.

3.4. FT-IR Spectra Analysis

FT-IR spectra analysis measurements were used to further investigate the mechanism of various reagents regarding the flotation behaviors of magnesite and dolomite. The IR spectrums of magnesite and dolomite with and without treatments of reagents are shown in Figure 6 and Figure 7, respectively.
Line 1 in Figure 6 presents the FT-IR spectra of raw magnesite. There is a broad band with a peak located at approximately 3440 cm−1, which is mainly due to a small amount of water being adsorbed onto the sample surface [31]. There are three peaks at 1441.01 cm−1, 885.25 cm−1, and 748.39 cm−1 that correspond to the characteristic sharp bands of magnesite [30]. The peak at 1441.01 cm−1 is an asymmetrical stretching vibration. The peak at 885.25 cm−1 corresponds to the out-plane flexural vibration of CO32−, and the peak at 748.39 cm−1 is due to the in-plane bending vibration of CO32− [32,33]. Line 2 is the IR spectrum of magnesite with the treatment of SSZS, and there is no obvious new peak in Line 2. This indicates that SSZS cannot adsorb onto magnesite’s surface. Line 3 in Figure 6 is the infrared spectrum of magnesite after it has interacted with NaOL. The new peaks appear at 2925.32 cm−1 and 2854.27 cm−1, which are the stretching vibrations of the -CH2- and -CH3 groups [34]. The new peak at 1697.13 cm−1 is caused by the adsorption of the carbonyl mode (C=O) of NaOL [35]. The new peaks that appeared at 1546.71 cm−1 and 1459.06 cm−1 indicate that a strong chemisorption of NaOL on the magnesite surface occurred [36]. Line 4 is the IR spectrum of magnesite after being treated with SSZS and NaOL. Similar to Line 3, there are several new peaks at 2926.08 cm−1, 2853.74 cm−1, 1698.89 cm−1, 1546.71 cm−1, and 1459.06 cm−1, which are characteristic adsorption peaks of NaOL. The results above indicate that SSZS cannot adsorb onto magnesite’s surface, so it cannot prevent NaOL from adsorbing onto magnesite’s surface.
The FTIR spectra of dolomite is given as Line 1 in Figure 7. Three characteristic bands of dolomite appear at 1452.47 cm−1, 882.83 cm−1, and 729.25 cm−1 [37]. Line 2 is the FTIR spectrum of dolomite, which interacts with SSZS. Three new peaks are located near 1203.86 cm−1, 1022.87 cm−1, and 962.45 cm−1. The new peak observed near 962.45 cm−1 reflects the absorbance at wavenumber ranges characteristic of the bending vibrations of the Si-O-Ca bond [38]. The above-mentioned results illustrate that SSZS has a chemical adsorption onto dolomite’s surface. The adsorption occurs at the Ca site; the Zn ion of SSZS is replaced by the Ca ion from dolomite’s surface. The presence of a new peak at 1022.87 cm−1 indicates the adsorption of the anionic species SiO(OH)3−. The peak at 1203.86 cm−1 is the characteristic of asymmetric stretching of the siloxane group Si-O-Si that probably belonged to the adsorption of polymeric species present, which is attributed to the high concentration of sodium silicate in flotation solution [39]. These new peaks in Line 2 indicate SSZS can adsorb onto dolomite’s surface via chemical adsorption. The FTIR spectrum of dolomite that interacted with NaOL is given as Line 3. The new feature peaks appear in two regions: 3000–2800 cm−1 and 1800–1400 cm−1. The peaks in the 3000–2800 cm−1 region can be attributed to the stretching vibrations of the -CH2- and -CH3 groups [36]. The peaks at 1708.71 cm−1, 1558.28 cm−1, 1446.64 cm−1, and 1424.56 cm−1 can be attributed to the -COO- stretching frequency. And, of these peaks, the peak near 1708.71 cm−1 is the C=O stretching vibration, the peak at 1558.28 cm−1 can be attributed to the -COO- asymmetric stretching vibration, and the peaks near 1446.64 cm−1 and 1424.56 cm−1 could be due to -COO- symmetric stretching vibration. The new bands, which are mentioned above, illustrate NaOL undergoes chemical adsorption onto dolomite’s surface [34]. Line 4 is the FT-IR spectra of dolomite treated with NaOL with the pre-adsorption of SSZS. Line 4 shows that the characteristic adsorption peaks of NaOL did not exist and those peaks near 1201.49 cm−1, 1022.13 cm−1, and 960 cm−1 are considered to be the characteristic adsorption peaks of SSZS [40]. These results indicate SSZS can adsorb onto dolomite’s surface; so, it can hinder the adsorption of NaOL onto dolomite’s surface.

4. Conclusions

In this work, the flotation separation of magnesite from dolomite cannot be realized without adding any depressants. This is attributed to the good inherent floatability of magnesite and dolomite in alkaline slurry solution. Sodium silicate modified with zinc sulfate is added as an inhibitor in the flotation slurry of magnesite and dolomite. The novel regulation of an agent, i.e., using NaOL as the collector (120 mg/L) and SSZS as the depressant (180 mg/L) with control of the pulp at pH 10.5, was demonstrated to realize the flotation separation efficiency of magnesite from dolomite. All of the flotation results indicate that SSZS has effective inhibitory ability and strong selective inhibition on dolomite. Through analyzing zeta potential measurements, contact angle measurements, and FT-IR analysis tests, it is concluded that SSZS can adsorb onto dolomite’s surface to prevent NaOL from adsorbing onto dolomite. On the contrary, there is no adsorption of SSZS onto magnesite, so NaOL can still adsorb onto the surface of magnesite. This explains why SSZS has good selective inhibitory action on the flotation separation of magnesite and dolomite.

Author Contributions

Investigation, data curation, formal analysis, visualization, writing—original draft, funding acquisition, N.L.; conceptualization, methodology, supervision, writing–review and editing, J.S.; project administration, resources, B.Y.; investigation, methodology, X.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Natural Science Foundation of the Inner Mongolia Autonomous Region (2019BS05021) and Inner Mongolia University of Science and Technology Innovation Fund (2019QDL-B26; 2019QDL-B28).

Data Availability Statement

All data presented are original.

Conflicts of Interest

The authors declare no conflicts of interest.

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Minerals 14 00355 g001
Figure 1. X-ray powder diffraction (XRD) patterns of samples: (a) magnesite; (b) dolomite.
Figure 1. X-ray powder diffraction (XRD) patterns of samples: (a) magnesite; (b) dolomite.
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Minerals 14 00355 g002
Figure 2. Effects of pH value on floatability of magnesite and dolomite (C(NaOL) = 120 mg/L).
Figure 2. Effects of pH value on floatability of magnesite and dolomite (C(NaOL) = 120 mg/L).
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Minerals 14 00355 g003
Figure 3. Floatability of minerals as a function of the inhibitors’ concentration (C(NaOL) = 120 mg/L; pH = 10.5).
Figure 3. Floatability of minerals as a function of the inhibitors’ concentration (C(NaOL) = 120 mg/L; pH = 10.5).
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Figure 4. Floatability of magnesite and dolomite with mixed depressants at various mass ratios (C(NaOL) = 120 mg/L; pH = 10.5; C(SSZS) = 180 mg/L).
Figure 4. Floatability of magnesite and dolomite with mixed depressants at various mass ratios (C(NaOL) = 120 mg/L; pH = 10.5; C(SSZS) = 180 mg/L).
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Minerals 14 00355 g005
Figure 5. The zeta potentials of magnesite (a) and dolomite (b) untreated or treated with different reagents.
Figure 5. The zeta potentials of magnesite (a) and dolomite (b) untreated or treated with different reagents.
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Figure 6. The IR spectrum of magnesite conditioned in different reagents: 1—magnesite; 2—magnesite + SSZS; 3—magnesite + NaOL; 4—magnesite + SSZS + NaOL.
Figure 6. The IR spectrum of magnesite conditioned in different reagents: 1—magnesite; 2—magnesite + SSZS; 3—magnesite + NaOL; 4—magnesite + SSZS + NaOL.
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Figure 7. The IR spectrum of dolomite conditioned in different reagents: 1—dolomite; 2—dolomite + SSZS; 3—dolomite + NaOL; 4—dolomite + SSZS + NaOL.
Figure 7. The IR spectrum of dolomite conditioned in different reagents: 1—dolomite; 2—dolomite + SSZS; 3—dolomite + NaOL; 4—dolomite + SSZS + NaOL.
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Table 1. Chemical composition of magnesite and dolomite (wt%).
Table 1. Chemical composition of magnesite and dolomite (wt%).
SamplesMgOCaOSiO2Al2O3FeO
Magnesite47.240.170.19/0.17
Dolomite21.5230.130.210.10/
Table 2. Results of flotation separation of mixed binary minerals using SSZS as the depressant (c(NaOL)= 120 mg/L; pH = 10.5; mass ratio of sodium silicate and zinc sulfate is 1:1).
Table 2. Results of flotation separation of mixed binary minerals using SSZS as the depressant (c(NaOL)= 120 mg/L; pH = 10.5; mass ratio of sodium silicate and zinc sulfate is 1:1).
SSZS Dosage
(mg/L)		ProductWeight Recovery (%)MagnesiteDolomite
Grade (%)Recovery (%)Grade (%)Recovery (%)
0concentrate97.4549.8597.4350.1597.46
tailing2.5550.192.5749.812.54
raw ore10049.8610050.14100
120concentrate68.1262.1383.6337.8752.23
tailing31.8825.9916.3774.0147.77
raw ore10050.6110049.39100
180concentrate59.1375.2187.9924.7929.64
tailing40.8714.8512.0185.1570.36
raw ore10050.5410049.46100
Table 3. Contact angle measurement results (pH = 10.5; C(NaOL) = 120 mg/L; C(SSZS) = 180 mg/L).
Table 3. Contact angle measurement results (pH = 10.5; C(NaOL) = 120 mg/L; C(SSZS) = 180 mg/L).
Test SystemMagnesiteDolomite
Without reagent34.8°31.5°
With NaOL68.8°60.2°
With SSZS + NaOL67.4°33.5°
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MDPI and ACS Style

Luo, N.; Shi, J.; Yan, B.; Wang, X. Flotation Separation of Magnesite from Dolomite Using Sodium Silicate Modified with Zinc Sulfate as a Selective Depressant. Minerals 2024, 14, 355. https://doi.org/10.3390/min14040355

AMA Style

Luo N, Shi J, Yan B, Wang X. Flotation Separation of Magnesite from Dolomite Using Sodium Silicate Modified with Zinc Sulfate as a Selective Depressant. Minerals. 2024; 14(4):355. https://doi.org/10.3390/min14040355

Chicago/Turabian Style

Luo, Na, Jingyang Shi, Baobao Yan, and Xiaoping Wang. 2024. "Flotation Separation of Magnesite from Dolomite Using Sodium Silicate Modified with Zinc Sulfate as a Selective Depressant" Minerals 14, no. 4: 355. https://doi.org/10.3390/min14040355

APA Style

Luo, N., Shi, J., Yan, B., & Wang, X. (2024). Flotation Separation of Magnesite from Dolomite Using Sodium Silicate Modified with Zinc Sulfate as a Selective Depressant. Minerals, 14(4), 355. https://doi.org/10.3390/min14040355

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