Selective flotation of ilmenite from olivine using the acidified water glass as depressant

International Journal of Mineral Processing 157 (2016) 73–79

Contents lists available at ScienceDirect

International Journal of Mineral Processing journal homepage: www.elsevier.com/locate/ijminpro

Selective flotation of ilmenite from olivine using the acidified water glass as depressant Yaohui Yang a,c, Longhua Xu b,⁎, Jia Tian b, Yachuan Liu c, Yuexin Han a,⁎ a

College of Resources and Civil Engineering, Northeastern University, Shenyang, Liaoning, PR China Key Laboratory of Solid Waste Treatment and Resource Recycle Ministry of Education, Southwest University of Science and Technology, Mianyang, Sichuan, PR China c Key Laboratory of Vanadium-titanium Magnetite Comprehensive Utilization, Ministry of Land and Resources, Institute of Multipurpose Utilization of Mineral Resources, CAGS, Chengdu, Sichuan, PR China b

a r t i c l e

i n f o

Article history: Received 4 February 2016 Received in revised form 28 September 2016 Accepted 3 October 2016 Available online 04 October 2016 Keywords: Ilmenite Olivine Flotation Acidified water glass Depressant

a b s t r a c t The selective flotation of ilmenite from olivine using an acidified water glass (AWG) as a depressant and sodium oleate (NaOL) as a collector has been studied. Through a series of micro-flotation tests, batch flotation tests, adsorption experiments and zeta potential measurements, the selective depression performance and depression mechanism of the AWG were demonstrated. The micro-flotation results indicate that the AWG at a molar ratio 1:3 of oxalic acid to water glass (WG) exhibits the maximum selective depression on olivine. The selective flotation of ilmenite from olivine can be better achieved using an AWG as depressant rather than WG in the artificially mixed minerals flotation experiments. Batch flotation test results indicate that, compared with the depressant WG, the depressant AWG not only increases the recovery and grade of the Ti concentrates by 7.74% and 3.82%, respectively, but also decreases the depressant consumption by two-fifths. Adsorption tests and zeta-potential measurements indicate that the AWG exhibits a stronger adsorption on the surface of olivine than ilmenite. The adsorption of the AWG on the olivine surface prevents the mineral from adsorbing collector NaOL due to electrostatic repulsion. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Titanium (Ti) is honored as “the third metal” subsequent to iron (Fe) and aluminum (Al) due to its unique and superior performance in coating and anti-corrosion, among other applications (Hou et al., 2011). Ti has been used widely in many fields, such as aerospace, the military industry, transportation, environmental protection, and in medical devices (Chen et al., 2013; Samal et al., 2009). The global titanium resources with industrial utilization value are mainly ilmenite, anatase, brookite, perovskite and rutile, among which ilmenite and rutile have been largely used as the main raw materials to produce titanium white, titanium sponge, etc. (Drzymala et al., 1983; Fan and Rowson, 2000). China has an abundance of titanium resources, and N 90% of them are stored in Panzhihua (Zhao et al., 2014; Zhou et al., 2013a,b). The largest deposit of vanadium-titanium magnetite in Panzhihua is the Hongge area (Luan et al., 2014). In recent years, to meet future industry needs, the exploration depth of vanadium-titanium magnetite is increasing. At the same time, it was found that, in the Hongge area, titanaugite and quartz are gradually replaced by olivine counting as ⁎ Corresponding authors. E-mail addresses: [email protected] (L. Xu), [email protected] (Y. Han).

http://dx.doi.org/10.1016/j.minpro.2016.10.001 0301-7516/© 2016 Elsevier B.V. All rights reserved.

one of the main gangue minerals in the onkilonite ore (Bai et al., 2012; Cheng et al., 2014). Olivine (Mg, Fe)2SiO4 is a type of silicate mineral with an island structure. The ilmenite and its main silicate gangue minerals (olivine or titanaugite) have very similar physiochemical properties. Iron, titanium, calcium, magnesium, and other metal ions exist on the surface of minerals, making it difficult to achieve selective flotation using the conventional collector fatty acids, whose adsorption mechanism is through chemisorption of the oleate ion onto the mineral surface (Fan and Rowson, 2000). For this reason, a series of studies have been implemented to improve ilmenite recovery. Previous studies were mainly focus on developing novel collectors or enlarging the floatability difference between ilmenite and main gangues such as titanaugite and quartz to improve ilmenite recovery (Xu et al., 2015; Zhu et al., 2011; Irannajad et al., 2014). In fact, using a proper depressant is also imperative to improve the floatability differences between valuable minerals and gangue minerals, improving the metal recovery (Liu et al., 2015b). Acidified water glass (AWG), except for its excellent dispersion performance used as an effective dispersant, is a type of inorganic depressant commonly used in the flotation of minerals such as calcite, fluorite, and silicates minerals. Zhou et al. found acidized water glass could achieve higher selectivity between fluorite and gangue minerals (carbonate and silicate minerals) in fluorite flotation (Zhou et al., 2013a,b). Bo et

74

Y. Yang et al. / International Journal of Mineral Processing 157 (2016) 73–79

al. observed that the acidified sodium silicate exhibits selective depression for calcite, allowing preferential flotation separation of scheelite from calcite (Bo et al., 2015). In ilmenite flotation, Song and Tsai have used the acidified sodium silicate with sulfuric acid to replace sodium fluorosilicate, and recognized that the AWG formed negatively charged colloidal silica that is selectively adsorbed on the gangue minerals in ilmenite flotation (Song and Tsai, 1989). Meanwhile, single oxalic acid has been used as a depressant to selectively depress titanaugite in an ether amine-ilmenite flotation system (Liu et al., 2015b). However, selective flotation of ilmenite from olivine using an AWG with oxalic acid as depressant has not been studied. In this study, oxalic acid was considered as an acidifier and was used to prepare the acidified water glass. The objective of this study is to demonstrate the selective flotation of ilmenite from olivine using the AWG as a depressant. The depressive performance and the mechanism of gangue depression using AWG will be reported in this study. These results will assist in developing a suitable flotation process for effective separation of ilmenite from olivine. 2. Materials and methods 2.1. Mineral samples

Fig. 1. XRD patterns of the purified samples (a) ilmenite and (b) olivine (IL = ilmenite, OL = olivine).

The high-grade mineral samples of ilmenite and olivine were obtained from the magnetic separation tailings of vanadium-titanium magnetite in Panzhihua. The samples were handpicked, crushed and ground in a laboratory porcelain mill, and −0.074 mm fractions were used in the experiments. The specific surface area of the powdered ilmenite and olivine were determined by a N2 adsorption analysis by a Micromeritics ASAP 2010C instrument and were found to be 1.25 m2/g and 2.17 m2/ g, respectively. Chemical composition analysis (Table 1) and X-ray diffraction (XRD) (Fig. 1) were used to study chemical and mineral compositions. The results showed the as-prepared ilmenite contained 50.90% TiO2, and the purities of ilmenite and olivine are N90%. The mineral used for bath flotation is magnetic separation tailings of vanadium-titanium magnetite ore from Panzhihua. The multi-elemental chemical analysis of the ore was conducted by acid dissolution and Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and the analysis results are shown in Table 2. As shown in Table 2, the minerals contained 17.21% TiO2, 30.52% SiO2, 16.33% FeO, 18.08% MgO and 1.36% Al2O3. The pyrite flotation tailings are used for the titanium roughing flotation and the chemical analysis results of the tailings are shown in Table 3.

acid was used as a pH regulator. All reagents used in batch flotation were of industrial grade. Tap water was used for batch flotation tests. 2.3. Micro-flotation tests The micro-flotation tests were carried out in a 40 mL hitch groove flotation cell. The purified mineral particles (3.0 g) were placed in a plexigas cell, which was then filled with 35 mL of ultrapure water. H2SO4 or NaOH was added to adjust the pH. After adding the desired amount of reagents, the suspension was stirred for 5 min. The flotation was conducted for 5 min. The froth products and tails were weighed separately after filtration and drying, and the recovery was calculated based on the dry weight of the product. In artificially mixed minerals flotation, ilmenite (1.2 g) and olivine (1.8 g) were added to 40 ml of solutions. The flotation grades of the two products were assessed by chemical analysis. The results of each flotation test were measured three times under the same experimental conditions, with the average was reported as the final value. The standard deviation, which is presented as an error bar, was calculated using Origin 9.0 to calculate based on the three measurements.

2.2. Reagents 2.4. Batch flotation tests In the micro-flotation tests, the acidified water glass (AWG) is a mixture of oxalic acid and water glass (WG) at different molar ratios. After mixing the solution was conditioned for 1 h on a magnetic stirrer. The WG, which has a SiO2:Na2O ratio of 2.8, was purchased from the Zhuzhou Flotation Reagents Factory, Hunan, China. Oxalic acid and the anionic collector NaOL were obtained from Sinopharm Chemical Reagent Co., Ltd. Sulfuric acid (H2SO4) and sodium hydroxide (NaOH) were used to adjust the pH of the system. Deionized water (Resistivity = 18.3 MΩ ∗ cm) was used for the micro-flotation tests. During the batch flotation tests, the homemade AWG was used as a new depressant. In a contrasting study, WG was employed as a common depressant. Mixed fatty acids soaps were used as collectors and sulfuric Table 1 Chemical compositions of the purified samples (mass fraction, %). Sample

TiO2

Fe2O3

MgO

Al2O3

SiO2

CaO

MnO

Ilmenite Olivine

50.90 0.02

41.16 10.09

5.06 46.43

0.89 0.91

1.51 41.81

0.31 0.11

0.64 0.12

In batch flotation, 100 g ore were ground to 76.7% passing 74 μm in a closed ball grinding mill (XMQ-240 × 90 mm) by low carbon alloy steel balls as grinding media at a pulp density of 66% by weight. The ore pulp was transferred into the flotation cell while agitating at approximately 1500 rpm and stirred for 3 min. For the pyrite flotation procedure, the desired amounts of reagents were added to the slurry and the slurry was conditioned for 4 min. Terpenic oil (34 g/t) were then added and the froth flotation was continued for 4 min during which a sulfur rougher concentrate was collected. The tailing was then used for the titanium flotation procedure. In titanium roughing flotation, H2O4 (2000 g/t) and AWG (1000 g/t) were firstly added to the pulp with 4 min of condition time and collectors (3000 g/t) were then added at pH approximately 5.5 with 4 min of reacting time. The titanium concentrates and the titanium tailings were collected after four times of cleaning flotation and once scavenging flotation, respectively. The flotation flowsheet of the bench-scale tests and corresponding flotation conditions are described in Fig. 2. The experimental system used the AWG as a depressant (the total dosage of depressant AWG in the locked cycle test was

Y. Yang et al. / International Journal of Mineral Processing 157 (2016) 73–79

75

Table 2 Chemical composition analysis of magnetic separation tailings of vanadium-titanium magnetite ore. Element composition

TFe

FeO

TiO2

SiO2

Al2O3

CaO

MgO

V2O5

S

Others

Wt.%

17.99

16.33

17.21

30.52

1.36

9.96

18.08

0.062

0.32

0.17

supernatant, a dilute fine particle suspension was taken for zeta potential measurement. The zeta-potentials were measured using a Malvern Zetasizer Nano ZS90 (England) equipped with a rectangular electrophoresis cell. The conductivity and pH of the suspension were monitored continuously during the measurement and the environmental temperature was maintained at 25 °C.

Table 3 Chemical composition analysis of the tailings used for the titanium roughing flotation. FeO

SiO2

TiO2

Al2O3 CaO

Element composition

TFe

wt.%

16.37 18.33 16.53 31.47 1.42

MgO

Fe2O3 Others

9.92 18.02 3.05

1.26

approximately 1500 g/t), and the comparative system used the WG as a depressant (the total dosage of WG in the locked cycle test was approximately 2500 g/t). The final product of concentrates and tailings were filtered, dried, weighed and analyzed for TiO2, respectively.

2.6. Adsorption tests The amount of adsorption was monitored using an Elementar liquid TOCII (German, Elementar Co.). The pure mineral samples (2.0 g) were placed in a Plexiglas cell (40 mL), which was filled with 35 mL of deionized water. Reagents were added to the cell in the manner described previously for micro-flotation and conditioned with stirring for 5 min. The conditioned pulp suspension was then added in a 50 mL vial. The vial was added with deionized water to make 50 mL. The adsorption samples were obtained by shaking the vials for 24 h in an air-thermostat

2.5. Zeta-potential measurements A suspension containing 0.1 wt.% mineral particles grounded to − 5 μm in an agate mortar was prepared in a 1 mM KCl solution, and conditioned by magnetic stirring for 5 min. After settling for 10 min, the

Feed Dosage of reagent: g/t

2´ 2´

H2SO4 1000 Butyl xanthate 100 Terpenic oil 34 pyrite Flotation 2´ H2SO4 2000 4´ AWG 1000

Sulfur rough concentrate 4´

Collector 3000 pH 4.5

Titanium Roughing Flotation H2SO4 300 AWG 300

5´ 3 ´

1st Cleaning Flotation H2SO4 200 AWG 100

2.5´

Collector 500 Scavenging Flotation 2´

2nd Cleaning Flotation H2SO4 AWG

100 50

2´

3rd Cleaning Flotation 1.5´ H2SO4 50 AWG 50 4th Cleaning Flotation 1.5´

Titanium concentrate

Titanium tailings Tailing

Fig. 2. The closed circuit flotation flowsheet and corresponding flotation conditions of vanadium-titanium magnetite in Panzhihua for batch flotation tests in the laboratory.

76

Y. Yang et al. / International Journal of Mineral Processing 157 (2016) 73–79

at 25 °C. The amount of collector adsorbed on the ilmenite and olivine particles was calculated as: Γ ¼ ðCo −CÞ  V=m  A

where Co and C are the initial and supernatant concentrations, respectively; V is the solution volume; m is the amount of the particles per sample; A is the mineral specific surface area.

3. Results and discussion 3.1. Single mineral micro-flotation results 3.1.1. Effects of NaOL collector dosage Fig. 3 presents the effect of NaOL concentration on the floatability of ilmenite and olivine at pH 5.0–6.0. As illustrated in Fig. 3, ilmenite recovery is gradually enhanced from 73.57% to 89.79% until NaOL concentration reaches 3 × 10−4 M. When the collector dosage is 6 × 10−4 M, the maximum flotation recovery of ilmenite reaches 93.54%. As for olivine, the flotation recovery increases steadily from 19.35% to 70.31% as the collector concentration is increased from 1.0 × 10− 4 M to 6.0 × 10−4 M. It is evident from the figure that the flotation recovery of both ilmenite and olivine are very high at a high concentrations of NaOL. The high recovery is attributed to the chemisorptions of NaOL on ilmenite and olivine (Irannajad et al., 2014). Fig. 3 also demonstrates that the recovery difference between ilmenite and olivine reached maximum value at a NaOL concentration of 2.0 × 10−4 M, and above this concentration the recovery difference begins to decline. It can be inferred from Fig. 3 that it is very difficult to separate ilmenite from olivine without using a depressant.

Fig. 4. Flotation recovery of olivine as a function of depressants dosage.

3.1.2. Effects of different depressants The effects of different depressants on the flotation recovery of olivine are presented in Fig. 4. It can be seen from Fig. 4 that the recovery of olivine decreases rapidly with the increase of AWG dosage, and the AWG can achieve effective depression of olivine in a low dosage range (b0.5 mM). When the concentration of depressants is below 1.0 mM the floatability of olivine became weaker after adding the AWG compared with the conventional depressants water glass (WG) and oxalic acid (OA).

3.1.3. Effects of AWG Fig. 5 shows the flotation recoveries of ilmenite and olivine as a function of pH using the AWG as a depressant. As seen from Fig. 5, with collector NaOL alone, ilmenite gets good floatability at pH N 4 and olivine possesses certain floatability at pH 5.0 ~ 7.0 and pH N 9.0, which is consistent with the previous results (Liu et al., 2015a). In the presence of the AWG, the recovery of ilmenite is roughly the same as in the absence of the AWG indicating that the depressive effect of the AWG on ilmenite flotation is weak. However, the recovery of olivine is greatly decreased in the presence of the AWG for pH b 9. In particular, for pH 5–6, the floated olivine was reduced from above 39% to below 5%. It can be inferred from the figure that the optimum pH value for the separation of ilmenite from olivine using an AWG depressant is 5–6, and at approximately pH 5–6, the recoveries of ilmenite and olivine are 76.69% and 10.56%, respectively. Thus, this pH range, 5–6, is used in all of the microflotation experiments. The effects of the AWG with different mole ratios of oxalic acid to water glass on the flotation of ilmenite and olivine were conducted and the results are shown in Fig. 6. It can be seen from Fig. 6 that the optimum mole ratio of oxalic acid to water glass is 1:3. The AWG forms hydrophilic colloidal silica that is selectively adsorbed on the gangue minerals. When the mole ratio of oxalic acid to water glass is 1:3, it is

Fig. 3. Effect of NaOL concentration on the floatability of ilmenite and olivine (pH = 5.0– 6.0).

Fig. 5. Flotation recoveries of ilmenite and olivine in the absence and presence of the AWG depressant as a function of pH.

Y. Yang et al. / International Journal of Mineral Processing 157 (2016) 73–79

Fig. 6. Effect of mole ratio of oxalic acid to water glass on ilmenite and olivine flotation.

more likely to form colloidal silica. Therefore, the AWG with a molar ratio of 1:3 is selected for the following flotation study. The effects of the AWG concentration on the floatability of ilmenite and olivine are presented in Fig. 7. It is observed in Fig. 7 that the recovery of olivine decreased rapidly as the AWG dosage increased, while the recovery of ilmenite changed relatively little maintaining at N80% before the AWG dosage reached 1.5 × 10−4 M. The minimum flotation recovery of olivine reached 2.46% when the AWG dosage was 2.5 × 10−4 M. The maximum recovery D-value between ilmenite and olivine reached 72.86% at an AWG concentration of 1.5 × 10−4 M. Thus, an AWG concentration of 1.5 × 10−4 M is used in all microflotation experiments. 3.2. Artificial mixed minerals micro-flotation results The results of the single micro-mineral flotation tests reveal that the AWG offers excellent selective depression of olivine from ilmenite. Flotation tests of mixed mineral samples were then carried out to further investigate its depressive performance. The flotation results of a mixture of minerals in presence of the conventional depressant WG and the new AWG were compared in Fig. 8 and Table 4. As illustrated in Fig. 8, the TiO2 grade of a concentration varies from 30.29% in the presence of the WG to 41.36% in the presence of the AWG, and the TiO2 recovery of the concentration increases from 68.21% to 79.17%. According to the simultaneous improvement in product grade and product recovery by the addition of the AWG in artificial mixed minerals micro-flotation tests, it can be inferred that the flotation of ilmenite from olivine using

77

Fig. 8. The TiO2 grades and recoveries of the concentrates from flotation of artificial mixed minerals in the presence of the WG and the AWG, respectively.

the AWG as a depressant can greatly improve the TiO2 concentration grade and recovery. 3.3. Batch flotation test results Based on the good depression performance towards olivine, the AWG was selected in the bench-scale locked cycle tests for a feed material containing 17.21% TiO2. The detailed flotation flowsheet and corresponding flotation conditions are listed in Fig. 2. The locked cycle test results are presented in Table 5. The results in Table 5 indicate that compared with the WG, the AWG decreases the collector consumption by two-fifths. The recovery and grade of the Ti concentrates increased by 7.74% and 3.82%, respectively. This indicated that the AWG is an effective depressant and shows a great potential for industrial application. 3.4. Adsorption tests results The difference in the adsorption of the collector on the mineral surface affects the flotation separation of mineral. After adding the AWG, the adsorption of the collector NaOL on the ilmenite and the olivine surfaces was studied as a function of the AWG dosage in Fig. 9. As illustrated in Fig. 9, the adsorption of NaOL on the olivine surface decreased steadily from 9.14 × 10− 6 mol/m2 to 4.84 × 10− 6 mol/m2 after the added AWG dosage was 3.0 × 10−4 M. On the surface of ilmenite, the decline curve of the adsorbed NaOL amount was relatively flat. Thus, the AWG can remarkably affect the NaOL adsorption on the surface of olivine but not on the surface of ilmenite. The adsorption of NaOL on ilmenite maintains above 1.7 × 10−5 mol/m2 over the whole range of AWG concentrations. Fig. 9 also demonstrated that the adsorption of collector on the ilmenite surface was significantly more than that of olivine after adding the AWG depressant, and the difference increases as the AWG dosage is elevated. It can be inferred that the selective flotation performance of the AWG might be explained by its affecting the adsorption of the collector on the surface of mineral particles. Table 4 Flotation results of mixtures of minerals using NaOL in the presence of the WG and the AWG, respectively. Depressants

Products

Ratio (w/%)

TiO2 grades (%)

TiO2 recoveries (%)

WG (0.15 mM)

Concentrates Tailing Feed Concentrates Tailing Feed

46.46 53.54 100.00 39.49 60.51 100.00

30.29 12.25 20.63 41.36 7.10 20.63

68.21 31.79 100 79.17 20.83 100

AWG (0.15 mM) Fig. 7. Effects of the AWG concentration on the floatability of ilmenite and olivine.

78

Y. Yang et al. / International Journal of Mineral Processing 157 (2016) 73–79

Table 5 The results of bench-scale locked cycle tests for a vanadium–titanium magnetite in Panzhihua. System

Products

Ratio, w (%)

TiO2 Grades (%)

TiO2 Recoveries (%)

AWG (1500 g/t)

Ti Concentrates Sulfur concentrates Tailings Feed Ti Concentrates Sulfur concentrates Tailings Feed

25.85 4.26 69.89 100 25.06 4.26 70.68 100

47.25 15.96 6.18 17.21 43.43 15.96 8.58 17.21

70.97 3.95 25.08 100 63.23 3.95 32.82 100

WG (2500 g/t)

Fig. 11. Zeta potentials of ilmenite and olivine particles as a function of NaOL concentration.

Fig. 9. Adsorption amount of NaOL on the surface of minerals as a function of the AWG dosage.

3.5. Zeta potential measurements results To determine the mechanism of mineral flotation with NaOL as the collector and the influence of depressant adsorption, the zeta potentials of ilmenite and olivine particles and those treated with either the collector or the depressant were measured as a function of pH. The change in zeta potential value could reflect the potential interaction between a collector or depressant and a mineral (Zhou et al., 2015). From the results given in Fig. 10, it is clear that the isoelectric points (IEP) of

ilmenite and olivine particles were 6.0 and 3.8, respectively. Due to the opposite charge on the surface of ilmenite (positively charged) and olivine (negatively charged) in the pH range 3.6–6, hetero-coagulation will occur easily between ilmenite and olivine particles (Zhou and Wang, 2014). In the presence of the AWG depressant or the NaOL collector, the zeta potentials of ilmenite and olivine particles became more negative, implying that the AWG and NaOL are absorbed onto the ilmenite and the olivine particle surfaces. Nevertheless, the negative change in the zeta potential of ilmenite particles caused by NaOL alone was more obvious than that of the AWG, which was contrary to olivine particles exposed to the same dosage of reagent. It can be inferred that the adsorption performances of the AWG on olivine surface is better than that of NaOL, while on the surface of ilmenite, the situation is totally opposite. To further detect the interaction between NaOL and the AWG, the zeta potentials of ilmenite and olivine particles as a function of NaOL concentration in the presence of AWG were collected and are shown in Fig. 11. As illustrated in Fig. 11, in the presence of the AWG, NaOL strongly decreases the ilmenite zeta potential but not the olivine zeta potential over the whole range of NaOL concentration. These results together with the adsorption test results might be attributed to competitive adsorption between NaOL and the AWG on the surface of mineral particles. The adsorption of the AWG on the surface of mineral particles not only made the gangue mineral surface hydrophilic but also prevented adsorption of NaOL on the surface due to electrostatic

Fig. 10. Zeta potentials of ilmenite (a) and olivine (b) particles as a function of pH values.

Y. Yang et al. / International Journal of Mineral Processing 157 (2016) 73–79

repulsion. Since the AWG showed a stronger adsorption on the olivine surface than on the ilmenite surface, the adsorption of the collector NaOL and the negative change caused by NaOL on the olivine surface were certainly less than that of ilmenite. 4. Conclusion AWG with a 1:3 M ratio of oxalic acid to water glass offers the best depression performance towards olivine, while its effect on ilmenite is weak. Thus, the efficient and selective flotation separation of ilmenite from olivine is achieved by adding the AWG. Batch flotation test results indicate that the AWG can get good flotation indexes and exhibits great potential for industrial application in ilmenite flotation. Adsorption tests reveal that the AWG can remarkably affect NaOL adsorption on the surface of olivine but not that of ilmenite. Zeta potential measurement results show the adsorption of the AWG on the surface of olivine is more obvious than NaOL, which prevents the adsorption of NaOL on the surface due to electrostatic repulsion. Acknowledgements The authors would like to thank the National Natural Science Foundation of China (Grant Nos. 51674207, 51504224 and 51304162), the Special Scientific Research Fund of Land and Resources Public Welfare Profession of China (Grant No. 201411056), and the Key Foundation of Natural Scientific Research of the Education Department of Sichuan Province, China (Grant No. 16ZA0130) for the financial support. References Bai, Z.J., Zhong, H., Li, C., Zhu, W.-G., Xu, G.-W., 2012. Platinum-group elements in the oxide layers of the Hongge mafic–ultramafic intrusion, Emeishan Large Igneous Province, SW China. Ore Geol. Rev. 46, 149–161. Bo, F., Xianping, L., Jinqing, W., Pengcheng, W., 2015. The flotation separation of scheelite from calcite using acidified sodium silicate as depressant. Miner. Eng. 80, 45–49. Chen, D.S., Zhao, L.S., Qi, T., Hu, G.P., Zhao, H.X., Li, J., Wang, L.N., 2013. Desilication from titanium–vanadium slag by alkaline leaching. Trans. Nonferrous Metals Soc. China 23 (10), 3076–3082.

79

Cheng, L., Zeng, L., Ren, Z., Wang, Y., Luo, Z., 2014. Timescale of emplacement of the Panzhihua gabbroic layered intrusion recorded in giant plagioclase at Sichuan Province, SW China. Lithos 204, 203–219. Drzymala, J., Luszczkiewicz, A., Simiczyjew, P., 1983. Flotation study on high-hercynite ilmenite ores. Int. J. Miner. Process. 10 (4), 289–296. Fan, X., Rowson, N., 2000. The effect of Pb(NO3)2 on ilmenite flotation. Miner. Eng. 13 (2), 205–215. Hou, T., Zhang, Z., Ye, X., Encarnacion, J., Reichow, M.K., 2011. Noble gas isotopic systematics of Fe–Ti–V oxide ore-related mafic–ultramafic layered intrusions in the Panxi area, China: The role of recycled oceanic crust in their petrogenesis. Geochim. Cosmochim. Acta 75 (22), 6727–6741. Irannajad, M., Mehdilo, A., Nuri, O.S., 2014. Influence of microwave irradiation on ilmenite flotation behavior in the presence of different gangue minerals. Sep. Purif. Technol. 132, 401–412. Liu, W., Zhang, J., Wang, W., Deng, J., Chen, B., Yan, W., Xiong, S., Huang, Y., Liu, J., 2015a. Flotation behaviors of ilmenite, titanaugite, and forsterite using sodium oleate as the collector. Miner. Eng. 72, 1–9. Liu, X., Huang, G.-y., Li, C.-x., Cheng, R.-j., 2015b. Depressive effect of oxalic acid on titanaugite during ilmenite flotation. Miner. Eng. 79, 62–67. Luan, Y., Song, X.-Y., Chen, L.-M., Zheng, W.-Q., Zhang, X.-Q., Yu, S.-Y., She, Y.-W., Tian, X.L., Ran, Q.-Y., 2014. Key factors controlling the accumulation of the Fe–Ti oxides in the Hongge layered intrusion in the Emeishan large Igneous Province, SW China. Ore Geol. Rev. 57, 518–538. Samal, S., Mohapatra, B., Mukherjee, P., Chatterjee, S., 2009. Integrated XRD, EPMA and XRF study of ilmenite and titania slag used in pigment production. J. Alloys Compd. 474 (1), 484–489. Song, Q., Tsai, S.C., 1989. Flotation of ilmenite using benzyl arsonic acid and acidified sodium silicate. Int. J. Miner. Process. 26, 111–121. Xu, H., Zhong, H., Tang, Q., Wang, S., Zhao, G., Liu, G., 2015. A novel collector 2-ethyl-2hexenoic hydroxamic acid: flotation performance and adsorption mechanism to ilmenite. Appl. Surf. Sci. 353, 882–889. Zhao, W., Chen, J., Chang, X., Guo, S., Srinivasakannan, C., Chen, G., Peng, J., 2014. Effect of microwave irradiation on selective heating behavior and magnetic separation characteristics of Panzhihua ilmenite. Appl. Surf. Sci. 300, 171–177. Zhou, F., Wang, L., 2014. Interaction of reactive oily bubble in flotation of bastnaesite [J]. J. Rare Earths 32 (8), 772–778. Zhou, M.-F., Chen, W.T., Wang, C.Y., Prevec, S.A., Liu, P.P., Howarth, G.H., 2013a. Two stages of immiscible liquid separation in the formation of Panzhihua-type Fe-Ti-V oxide deposits, SW China. Geosci. Front. 4 (5), 481–502. Zhou, W., Moreno, J., Torres, R., Valle, H., Song, S., 2013b. Flotation of fluorite from ores by using acidized water glass as depressant. Miner. Eng. 45, 142–145. Zhou, Y., Zhang, Y., Li, G., Wu, Y., Jiang, T., 2015. A further study on adsorption interaction of humic acid on natural magnetite, hematite and quartz in iron ore pelletizing process: effect of the solution pH value. Powder Technol. 271, 155–166. Zhu, Y.g., Zhang, G.-f., Feng, Q.-m., Yan, D.-c., Wang, W.-q., 2011. Effect of surface dissolution on flotation separation of fine ilmenite from titanaugite. Trans. Nonferrous Metals Soc. China 21, 1149–1154.