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A novel chemical scheme for flotation of rutile from eclogite tailing
Accepted Manuscript A Novel Chemical Scheme for Flotation of Rutile from Eclogite Tailing Bo Xu, Shuang Liu, Hongqiang Li, Yunliang Zhao, Hongchao Li, Shaoxian Song PII: DOI: Reference:
S2211-3797(17)30788-X http://dx.doi.org/10.1016/j.rinp.2017.07.063 RINP 836
To appear in:
Results in Physics
Received Date: Revised Date: Accepted Date:
8 May 2017 26 June 2017 26 July 2017
Please cite this article as: Xu, B., Liu, S., Li, H., Zhao, Y., Li, H., Song, S., A Novel Chemical Scheme for Flotation of Rutile from Eclogite Tailing, Results in Physics (2017), doi: http://dx.doi.org/10.1016/j.rinp.2017.07.063
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A Novel Chemical Scheme for Flotation of Rutile from Eclogite Tailing
Bo Xu 1, Shuang Liu 1, Hongqiang Li 2, Yunliang Zhao 1, 3, Hongchao Li 4, Shaoxian Song 3*
1
School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei, 430070, China
2
School of Resources and Civil Engineering, Wuhan Institute of Technology, Wuhan, Hubei, 430205, China
3
Hubei Key Laboratory of Mineral Resources Processing and Environment, Luoshi Road 122, Wuhan, Hubei, 430070, China 4
Zhengzhou Research Institute for Resource Utilization, Longhai Road 328, Zhengzhou, Henan, 450006, China
* Corresponding author. E-mail: [email protected]
Abstract A novel chemical scheme for the flotation of rutile from eclogite tailings has been developed in this work. It consists of lead ion as the activator, sodium fluorosilicate (SF) as the depressant, and styryl phosphonic acid (SPA) and n-octyl alcohol (OCT) as the collector. By using the proposed scheme to treat a feed ore of 4.5% TiO2, a rougher concentrate of grade 84.47% TiO2 was achieved with the recovery of 61.5%. Also, the scheme made a high flotation rate for rutile. The scheme was applied to closed-circuit flotation (one-stage rougher flotation, two-stage scavenger flotation and two-stage cleaner flotation), produced a concentrate of 92% TiO2 with the recovery of 70%. It is shown that the new chemical scheme would be a potential one for the effective separation of rutile from eclogite ores. Keywords: Rutile; flotation; reagents; eclogite tailings
1. Introduction Rutile, which is considered to be an exiguous and strategic resource for the extraction of titanium dioxide, has emerged as an excellent material for the production of titanium white[1]. One of the most prominent applications of rutile is its modification for high-quality welding electrodes [2,3]. In addition, not only can it serve as a photocatalyst in solar cells, it is also a good material for bone grafting [4]. In China, the annual output of rutile is around 2,000 ton, whereas the annual demand is more than 70,000 ton. Rutile sand is currently the main mineral for the manufacturing of rutile. Primary rutile currently accounts for a large proportion of rutile mineral reserves, while only a small amount of them has been developed due to
its poor quality, fine granularity, and a complicated processing technology. However, eclogite has a strong reputation because of its large-scale reserves, good continuity of ore deposits, and easy to exploitation. In recent years, there has been a mounting awareness regarding the need for this type of primary rutile. The mineral mostly includes garnet and omphacite, as well as small quantities of chlorite, hornblende, rutile, apatite and ilmentite. Rutile is a special phase arising from the high temperature and pressure of metamorphic eclogite ore. Eclogite in Donghai is a large-scale garnet and omphacite deposit. The grade of garnet and omphacite in the ore is around 34% and 31%, respectively, whereas the grade of rutile is only 1.6%. Garnet is recovered preferentially through magnetic separation in commercial production conditions. However, the rutile with 4.5% TiO2 in tailing has not been recovered. As such, method for recovering rutile from the tailing would be a notable achievement. This eclogite ore is mainly composed of omphacite, garnet, and rutile. There is little difference in the densities of rutile and garnet, and thus it is difficult to separate them through gravity concentration. In addition, few discrepancies of the specific susceptibilities existed between rutile and omphacite, so they cannot be separated from each other via magnetic separation. According to the previous investigation, forth flotation is an efficient method to separated rutile from the gangue minerals. However, some difficulties still exist in rutile flotation. One problem is the lack of admirable collectors. Although sodium oleate is widely used in the flotation of rutile, its selectivity is weak [5]. In addition, despite its efficiency, benzyl arsonic acid (BAA) is highly noxious. In recent years,
composite collectors have become dramatically popular in the flotation of rutile. Researchers have systematically compared various types of collectors, and have demonstrated styryl phosphoric acid (SPA) to be the most effective. Under the support of fatty alcohols, the flotation becomes vastly superior to the condition of single SPA [6]. At present, very limited flotation techniques have been used for the recovery of rutile from eclogite, and the separation efficiencies are poor. Reverse flotation, a combined flowsheet including flotation-magnetic separation, and even flotation-gravity concentration-magnetic separation combined processing, are always used in the process of rutile. In flotation tests of Athabasca oil sand tailing, the content of TiO2 in the concentrate enriched to 87-89% by using dry magnetic separation and reverse flotation [7]. A process comprised the flotation of sulfides and carbonates at pH of about 9, followed by the flotation of rutile at pH of around 2, has also been developed [8]. In addition, the recovery of rutile from copper tailing has been carried out using flotation with a single rougher flotation, two-stage scavenger flotation and four-stage cleaner flotation. The final concentrate with TiO2 grade of 68.28% and total recovery of about 6.6% was obtained [9]. Therefore, an efficient and convenient flotation flowsheet is significant for the recovery rutile from tailing, by which a high ratio of enrichment is also encouraged. Another problem in the flotation of eclogite rutile is the use of acid-base regulator. As discussed earlier, the adsorptions of collector on rutile and the zeta potential of solid / solution increased when the pH is below 3 [10]. Therefore, sulfuric acid and hydrochloric acid are regularly used in the flotation of titanium minerals to
adjust the pH. The floatability of ilmenite and perovskite, as demonstrated in various studies, is poor without acid pretreatment. Deterioration will occur in rutile flotation when the pH is above 6[11]. In addition, rutile flotation at different pH levels has been studied. The highest TiO2 content was obtained at pH 4 while the peak recovery was gained at pH 7 [12]. Moreover, petroleum sulfonate served as collector for the recovery of rutile from copper tailings was at a pH of about 2 to 3 [8]. In conclusion, pulp pH notably influenced the flotation rate of rutile in various collectors. Although an appropriate pH can indeed improve the flotation result, large amount of acid needs to be used in the pH adjustment. Pretreatment with hydrochloric acid for ilmenite provide a better recovery but the addition was over 4,000g/ton [11]. For increasing the recovery of rutile, the addition of sulfuric acid is about 3500 g/ton [13]. In terms of the tailing used in this study, the pH of the pulp is around 8 to 9, and 4,000 g/ton of sulfuric acid is needed to add to adjust the pH down to 4. Not only does this increase the operational difficulties, it also result in corrosion of the equipment. The objective of the present study is to develop a novel chemical scheme for the recovery of rutile from the tailing of eclogite. Decent flotation indicators were achieved by a relatively simple flotation flowsheet without acid pretreatment. SPA and n-octyl alcohol (OCT), combined with regulators such as lead ion and sodium fluorosilicate (SF), have performed very well in the recovery of rutile from the tailing. An optimum reagent system was achieved using a four-factor and three-level orthogonal experiment. Furthermore, the vital function of lead ion and SF were demonstrated through single-factor experiments.
2. Experiments 2.1 Materials Table 1 Chemical analysis of the ore sample (wt %) TiO2
SiO2
CaO
Fe2O3
Al2O3
MgO
P2O5
MnO
Loss
4.583
49.893
11.277
11.039
10.546
5.786
2.039
0.102
0.383
800
G
M:mica P:amphibole Q:quartz A:apatite R:rutile O:omphacite G:garnet C:calcite
700
Intensity(counts)
600 M Q O R
500 400 300
M
O G Q R
G
A P
200
A
100
Q AM A
P
A
C
C A
G
C G
R C R Q QO
Q G Q
P Q
G
0 10
20
30
40
50
60
70
80
Two-Theta(deg)
Figure 1 X-ray diffraction results of this tailing The eclogite tailing used in this work was obtained from the Rizhao concentrated garnet mill in China. The results of X-ray fluores-cence is presented in Table 1, indicating the grade of TiO2 was around 4.5%. In Fig.1, X-ray diffraction results are presented, showing that the tailing was composed of omphacite, garnet, mica, apitate, quartz, and rutile. The particle size distribution of this tailing was determined using standard sieves, it was shown that d10, d40, and d70 (diameters at a cumulative undersizing of 10%, 40%, and 70%, respectively) were 74, 300, and 600 μm, respectively.
In this study, lead (II) nitrate, n-octyl alcohol (OCT), and sodium fluorosilicate (SF) were purchased from Sinopharm Chemical Reagent Co., Ltd., China. The SPA was made in Zhuzhou, China. 2.2 Sample preparation The tailing used in the froth flotation was treated through a grinding process in a XMQ--240×90 conical ball mill with a volume of 6.5L, and the running speed was 96 r/ min. Although the garnet is difficult to levigate, some of the gangue minerals (mica and apatite) were easy to grind. And thus a large amount of slime is generated during the grinding. The flotation recovery will be poor when the ore is easily muddied. To solve the problem, a simple de-sliming process in this study via free sedimentation method was adopted. The pulp was first poured into a container whose diameter and volume are 20 cm and 2000 mL, respectively. Then adding water to dilute the pulp to the calibration of 2000 mL of the tank, and stirring well to ensure mix uniformly. After 1minute and 30 seconds standing, a rubber hose was inserted to the calibration of 800 mL to drain away the upper solution. The operation repeated 3 times. The ores used in this study all underwent a uniform de-sliming process, and the loss of TiO2 in the slime was less than 6 %. 2.3. Flotation Tests A rougher flotation experiment was carried out in an RK/FD type of single tank flotation machine with a volume of 1.5 L. In the chemical scheme, lead nitrate was used as an activator, and sodium fluorosilicate (SF) and sodium silicate (SS) were used as the depressor and slurry dispersant, respectively. Styryl phosphonic acid (SPA)
and n-octyl alcohol (OCT) were used as the composite collectors. And terpenic oil was served as frother.
Samples Lead nitrate Sodium fluorosilicate (SF) Sodium silicate (SS) SPA + OCT Terpenic oil
Rough concentrate
Tailing
Figure 2 Flowsheet of the rougher flotation test The flowsheet of the rougher flotation test is illustrated in Fig. 2. First, lead nitrate, sodium fluorosilicate (SF), sodium silicate (SS), and composite collectors were added in turn with an interval of 3 to 5 min. After that the conditioning continued for 1 min with terpenic oil addition. The forth flotation was performed for 90 s. In this study, the content of titanium dioxide was analyzed by ammonium ferric sulfate capacity method. 3. Results and Discussion The rougher flotation results obtained through this novel chemical scheme are presented in Table 2. The rougher concentrate with 84.47% TiO2 was floated with a recovery of 61.49%. The results indicated the scheme for the rutile separation was decent and the concentration ration via the rougher flotation was high. Furthermore, a closed-circuit experiment composed of a single rougher flotation, two-stage cleaner
flotation (including a black cleaner flotation) and two-stage scavenger flotation was performed, and the concentrate with the grade of 92% TiO2 and recovery of 70% was gained. Specifically, an acid pretreatment was usually carried out in Ti-bearing mineral flotation previously. However, an acid-base regulator is not required when using this scheme. Table 2 Results of rougher flotation test Product
Yield (%)
Grade (%)
Recovery (%)
concentrate
4.25
84.47
61.49
tailing
95.75
2.35
38.51
feed
100
5.84
100
Grade of rougher concentrate(%)
80 90 70 87
60 % Grade % Recovery
84
50 40
81
30 78 20 75 10
20
40
60
80
100
Recovery of rougher concentrate(%)
93
120
Flotation time(s)
Figure 3. Relationship between grade and recovery in the rutile flotation kinetics experiment using the proposed novel chemical scheme The results of the flotation kinetics experiment of the rougher flotation from the
proposed chemical scheme are illustrated in Fig 3. As indicated by the data in Fig 3, the chemical scheme can reach to be high-speed flotation. A concentrate with 90% TiO2 was achieved at around 10 s, and it only took 1 min to obtain a concentrate containing 81% TiO2 with a recovery of 64%. It indicated that the novel chemical scheme had an excellent collection capability and selectivity of rutile. Therefore, the capacity of the facilities and technical indicators can be improved with lower costs by using the novel chemical scheme. The optimum reagent dosage of the rougher flotation was achieved through a four-factor and three-level orthogonal experiment. The plans for this orthogonal experiment are described in Table 3. During the mathematical analysis, the mineral separation efficiency (E) was selected as an evaluation criterion for every test, and can be calculated using Hancock formula as follows.
E ( ) /(1 / m )(%)
(1)
βm is the content of TiO2 in a pure mineral, and has a value of 97% in this study. Table 3 Separation efficiency of every test during the orthogonal experiment
A（pb2+）
B(SF)
C(SS)
D(SPA)
Separation efficiency E (%)
1
(1)
(1)
(3)
(2)
31.48
2
(2)
(1)
(1)
(1)
40.52
3
(3)
(1)
(2)
(3)
37.83
4
(1)
(2)
(2)
(1)
29.45
5
(2)
(2)
(3)
(3)
45.56
6
(3)
(2)
(1)
(2)
51.98
Test number
Factors
7
(1)
(3)
(1)
(3)
47.49
8
(2)
(3)
(2)
(2)
42.05
9
(3)
(3)
(3)
(1)
14.64
E1
36.14
36.61
46.66
28.20
E2
42.71
42.33
36.44
41.84
E3
34.82
34.73
30.56
43.63
7.89
7.6
16.1
15.43
R= E max
E min
E 0 37.89
The factors A, B, C, and D represent pb2+, sodium fluorosilicate (SF), sodium silicate (SS), and styryl phosphonic acid (SPA), respectively. According to the mathematical analysis of the orthogonal experiment, the best dosage of combined reagents for rougher flotation is A2B2C1D3. Sodium silicate（SS）showed the most significant effect on the flotation. The separation efficiency (E) continuously dropped with an increasing dosage of SS. Sodium silicate (SS) was used as slurry dispersant; however, a clear inhibitory effect was presented with increasing dosage. Hence, a small amount of SS can not only fully disperse the clay, but also provide a suitable inhibiting effect on the gangue. Styryl phosphonic acid (SPA) is another major factor in the orthogonal experiment. The concentrate grade positively related to the SPA dosage in a suitable range of octanol (OCT) dosage. Some researchers have demonstrated that satisfactory results could be achieved due to the increasing hydrophobicity of the rutile caused by the co-adsorption of SPA and octanol (OCT) on its surface [6]. In the novel chemical scheme, the dosage of styryl phosphonic acid
(SPA) was 500-700 g/ton, and the octanol (OCT) was about 50-80 g/ton. In the rougher flotation, the mass ratio of styryl phosphonic acid and octanol was approximate 6. Suitable activator and inhibitor are crucial to the froth flotation of rutile due to its refractory. Thus, the effects of lead nitrate and sodium fluorosilicate (SF) on the flotation were verified via single-factor tests. It have been proved that lead ion has nice activation on Ti-containing minerals, and the adsorption capacity of Pb (II) ions on titanium nanotubes (TNT) was great[14]. The formation of the complex Ti-O-Pb+ mainly contributed to the improvement of rutile flotation have been convinced previously[15] . As well known, lead ion has an excellent activation on rutile. However, the synergistic effect between pb2+ and a composite collector (SPA and OCT) is scarcely investigated. Figure 4 illustrates the recovery of rougher concentrate as a function of its grade in the presence and absence of lead ion. The recovery vs. grade line with the addition of lead ion was located on the right side of that in the absence of lead ion, indicating that the adding lead ion in the cell could increase the recovery of the rougher concentrate. At the grade of 44% TiO2, the recovery of the scheme with lead ion achieved to 72%, while the scheme in the absence of lead ion reached to 52%. Moreover, the difference was much greater as the concentrate grade increased. Consequently, the addition of lead ion could obviously improve the rutile flotation.
Recovery of rougher concentrate(%)
80
70
60
50
40
30
20
% the scheme in the presence of lead ion % the scheme in the absence of lead ion
10 10
20
30
40
50
60
70
80
90
Grade of rougher concentrate(%)
Figure.4. Relationship between grade and recovery of TiO2 in rougher concentrate in the presence and absence of lead ion Sodium fluorosilicate (SF) is a very important inhibitor on the silicate gangue minerals. No unanimous conclusion on inhibitory mechanism of SF in flotation has been drawn due to the varied opinions. The effects of SF on a diaspore-rutile suspension were investigated, and it was found that the SiF62- absorbed on the diaspore surface, making it hydrophilic[16]. A flotation test showing the rutile response to different additions of SF using the proposed chemical scheme was conducted, the results of which are given in Fig 5. As shown in Fig.5, the rutile grade and recovery of the rougher concentrate both first increased and then reduced with the dosage of SF increased from 500 g/ton to 1500 g/ton. The optimum rutile grade and recovery of the concentrate were achieved when the dosage of SF was 1000 g/ ton, and an addition of more than 1000 g/ton dosage caused deterioration in the rutile flotation.
70
80
60
75 50 70 65
40
60 30 55
Grade Recovery
50
Recovery of rougher concentrate(%)
Grade of rougher concentrate(%)
85
20 600
800
1000
1200
1400
Dosage of sodium fluosilicate(g/ton)
Figure5.
Relationship between the SF dosage and rougher flotation results using proposed novel chemical scheme
4. Conclusions 1. A novel chemical scheme using styryl phosphonic acid (SPA), n-octyl alcohol (OCT), lead ion, sodium fluorosilicate (SF), and sodium silicate (SS) worked well on the flotation of eclogite-type rutile. All reagents were added at natural pH without acid pretreatment. 2. Lead nitrate and sodium fluorosilicate were extremely ideal regulators in the flotation of eclogite rutile. The roles of the appropriate regulators, in conjunction with efficient composite collectors, have pioneered an important avenue for the development of a serviceable chemical scheme in the actual production of eclogite rutile flotation. Acknowledgments
The financial supports for this work from the Ministry of Land and Resources of China (201511063-2), the Natural Science Foundation of Hubei Province of China (2016CFA013) and the Wuhan Science and Technology Bureau (2016070204020156) are gratefully acknowledged References 1. Suda, Y.; Morimoto, T.; Nagao, M. (1987) Adsorption of alcohols on titanium dioxide (rutile) surface. Langmuir, 3 (1) : 99. 2. Balos, S.; Sidjanin, L.; Dramicanin, M.; Labus, D.; Pilic, B.; Jovicic, M. (2016) Modification of cellulose and rutile welding electrode coating by infiltrated TiO2 nanoparticles. Metals and Materials International, 22 (3) : 509. 3. Herranz, M.; Rozas, S.; Pérez, C.; Idoeta, R.; Núñez-Lagos, R.; Legarda, F. (2013) Effective dose in the manufacturing process of rutile covered welding electrodes. Journal of Radiological Protection: Official Journal of the Society for Radiological Protection , 33 (1): 213. 4. Diebold, U. (2003) The surface science of titanium dioxide. Surface science reports, 48 (5): 53. 5. Wang, J.; Cheng, H. W.; Zhao, H. B.; Qin, W. Q.; Qiu, G. Z. (2016) Flotation behavior and mechanism of rutile with nonyl hydroxamic acid. Rare Metals, 35 (5) : 419. 6. Liu, Q.; Peng, Y. (1999) The development of a composite collector for the flotation of rutile. Minerals Engineering , 12 (12) : 1419. 7. Chachula, F.; Liu, Q. (2003) Upgrading a rutile concentrate produced from
athabasca oil sands tailings. Fuel, 82 (8): 929. 8. Llewellyn T O, Sullivan G V. (1982) Froth flotation of rutile: US, US4362615 [P].. 9. Cui, Z. Y. (2011) Beneficability Recovery test of Rutile from a Copper Tailings. Metal Mine. 10. Graham, K.; Madeley, J. D. (1962) Relation between the zea potential of rutile. Journal of Chemical Technology and Biotechnology,12 (11): 485. 11. Bulatovic, S.; Wyslouzil, D. M. (1999) Process development for treatment of complex perovskite, ilmenite and rutile ores. Minerals Engineering , 12 (12) : 1407. 12. Bilgin, O.; Sakcali, Al. (2013) Beneficiation of Rutile Ore by Combined Agglomeration and Flotation Methods. Arab Gulf Journal of Scientific Research, 31(1): 10. 13. Wang, J.; Xiao, W.; A method to improve the recovery of rutile: CN, 105665146 A [P]. 14. Chen, Y.; Lo, S.; Kuo, J. (2010) Pb ( II ) adsorption capacity and behavior of titanate nanotubes made by microwave hydrothermal method. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 361(1-3):126. 15. Li, H.; Mu, S.; Weng, X.; Zhao, Y.; Song, S. (2016) Rutile flotation with Pb2+ ions as activator: Adsorption of Pb2+ at rutile/water interface. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 506 : 431. 16. Song, S.; Lopez-valdivieso, A.; Lu, S.; Ouyang, J. (2002) Selective dispersion in a diaspore – rutile suspension by sodium fluorosilicate. Powder technology, 123(2) : 178.
S2211-3797(17)30788-X http://dx.doi.org/10.1016/j.rinp.2017.07.063 RINP 836
To appear in:
Results in Physics
Received Date: Revised Date: Accepted Date:
8 May 2017 26 June 2017 26 July 2017
Please cite this article as: Xu, B., Liu, S., Li, H., Zhao, Y., Li, H., Song, S., A Novel Chemical Scheme for Flotation of Rutile from Eclogite Tailing, Results in Physics (2017), doi: http://dx.doi.org/10.1016/j.rinp.2017.07.063
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A Novel Chemical Scheme for Flotation of Rutile from Eclogite Tailing
Bo Xu 1, Shuang Liu 1, Hongqiang Li 2, Yunliang Zhao 1, 3, Hongchao Li 4, Shaoxian Song 3*
1
School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei, 430070, China
2
School of Resources and Civil Engineering, Wuhan Institute of Technology, Wuhan, Hubei, 430205, China
3
Hubei Key Laboratory of Mineral Resources Processing and Environment, Luoshi Road 122, Wuhan, Hubei, 430070, China 4
Zhengzhou Research Institute for Resource Utilization, Longhai Road 328, Zhengzhou, Henan, 450006, China
* Corresponding author. E-mail: [email protected]
Abstract A novel chemical scheme for the flotation of rutile from eclogite tailings has been developed in this work. It consists of lead ion as the activator, sodium fluorosilicate (SF) as the depressant, and styryl phosphonic acid (SPA) and n-octyl alcohol (OCT) as the collector. By using the proposed scheme to treat a feed ore of 4.5% TiO2, a rougher concentrate of grade 84.47% TiO2 was achieved with the recovery of 61.5%. Also, the scheme made a high flotation rate for rutile. The scheme was applied to closed-circuit flotation (one-stage rougher flotation, two-stage scavenger flotation and two-stage cleaner flotation), produced a concentrate of 92% TiO2 with the recovery of 70%. It is shown that the new chemical scheme would be a potential one for the effective separation of rutile from eclogite ores. Keywords: Rutile; flotation; reagents; eclogite tailings
1. Introduction Rutile, which is considered to be an exiguous and strategic resource for the extraction of titanium dioxide, has emerged as an excellent material for the production of titanium white[1]. One of the most prominent applications of rutile is its modification for high-quality welding electrodes [2,3]. In addition, not only can it serve as a photocatalyst in solar cells, it is also a good material for bone grafting [4]. In China, the annual output of rutile is around 2,000 ton, whereas the annual demand is more than 70,000 ton. Rutile sand is currently the main mineral for the manufacturing of rutile. Primary rutile currently accounts for a large proportion of rutile mineral reserves, while only a small amount of them has been developed due to
its poor quality, fine granularity, and a complicated processing technology. However, eclogite has a strong reputation because of its large-scale reserves, good continuity of ore deposits, and easy to exploitation. In recent years, there has been a mounting awareness regarding the need for this type of primary rutile. The mineral mostly includes garnet and omphacite, as well as small quantities of chlorite, hornblende, rutile, apatite and ilmentite. Rutile is a special phase arising from the high temperature and pressure of metamorphic eclogite ore. Eclogite in Donghai is a large-scale garnet and omphacite deposit. The grade of garnet and omphacite in the ore is around 34% and 31%, respectively, whereas the grade of rutile is only 1.6%. Garnet is recovered preferentially through magnetic separation in commercial production conditions. However, the rutile with 4.5% TiO2 in tailing has not been recovered. As such, method for recovering rutile from the tailing would be a notable achievement. This eclogite ore is mainly composed of omphacite, garnet, and rutile. There is little difference in the densities of rutile and garnet, and thus it is difficult to separate them through gravity concentration. In addition, few discrepancies of the specific susceptibilities existed between rutile and omphacite, so they cannot be separated from each other via magnetic separation. According to the previous investigation, forth flotation is an efficient method to separated rutile from the gangue minerals. However, some difficulties still exist in rutile flotation. One problem is the lack of admirable collectors. Although sodium oleate is widely used in the flotation of rutile, its selectivity is weak [5]. In addition, despite its efficiency, benzyl arsonic acid (BAA) is highly noxious. In recent years,
composite collectors have become dramatically popular in the flotation of rutile. Researchers have systematically compared various types of collectors, and have demonstrated styryl phosphoric acid (SPA) to be the most effective. Under the support of fatty alcohols, the flotation becomes vastly superior to the condition of single SPA [6]. At present, very limited flotation techniques have been used for the recovery of rutile from eclogite, and the separation efficiencies are poor. Reverse flotation, a combined flowsheet including flotation-magnetic separation, and even flotation-gravity concentration-magnetic separation combined processing, are always used in the process of rutile. In flotation tests of Athabasca oil sand tailing, the content of TiO2 in the concentrate enriched to 87-89% by using dry magnetic separation and reverse flotation [7]. A process comprised the flotation of sulfides and carbonates at pH of about 9, followed by the flotation of rutile at pH of around 2, has also been developed [8]. In addition, the recovery of rutile from copper tailing has been carried out using flotation with a single rougher flotation, two-stage scavenger flotation and four-stage cleaner flotation. The final concentrate with TiO2 grade of 68.28% and total recovery of about 6.6% was obtained [9]. Therefore, an efficient and convenient flotation flowsheet is significant for the recovery rutile from tailing, by which a high ratio of enrichment is also encouraged. Another problem in the flotation of eclogite rutile is the use of acid-base regulator. As discussed earlier, the adsorptions of collector on rutile and the zeta potential of solid / solution increased when the pH is below 3 [10]. Therefore, sulfuric acid and hydrochloric acid are regularly used in the flotation of titanium minerals to
adjust the pH. The floatability of ilmenite and perovskite, as demonstrated in various studies, is poor without acid pretreatment. Deterioration will occur in rutile flotation when the pH is above 6[11]. In addition, rutile flotation at different pH levels has been studied. The highest TiO2 content was obtained at pH 4 while the peak recovery was gained at pH 7 [12]. Moreover, petroleum sulfonate served as collector for the recovery of rutile from copper tailings was at a pH of about 2 to 3 [8]. In conclusion, pulp pH notably influenced the flotation rate of rutile in various collectors. Although an appropriate pH can indeed improve the flotation result, large amount of acid needs to be used in the pH adjustment. Pretreatment with hydrochloric acid for ilmenite provide a better recovery but the addition was over 4,000g/ton [11]. For increasing the recovery of rutile, the addition of sulfuric acid is about 3500 g/ton [13]. In terms of the tailing used in this study, the pH of the pulp is around 8 to 9, and 4,000 g/ton of sulfuric acid is needed to add to adjust the pH down to 4. Not only does this increase the operational difficulties, it also result in corrosion of the equipment. The objective of the present study is to develop a novel chemical scheme for the recovery of rutile from the tailing of eclogite. Decent flotation indicators were achieved by a relatively simple flotation flowsheet without acid pretreatment. SPA and n-octyl alcohol (OCT), combined with regulators such as lead ion and sodium fluorosilicate (SF), have performed very well in the recovery of rutile from the tailing. An optimum reagent system was achieved using a four-factor and three-level orthogonal experiment. Furthermore, the vital function of lead ion and SF were demonstrated through single-factor experiments.
2. Experiments 2.1 Materials Table 1 Chemical analysis of the ore sample (wt %) TiO2
SiO2
CaO
Fe2O3
Al2O3
MgO
P2O5
MnO
Loss
4.583
49.893
11.277
11.039
10.546
5.786
2.039
0.102
0.383
800
G
M:mica P:amphibole Q:quartz A:apatite R:rutile O:omphacite G:garnet C:calcite
700
Intensity(counts)
600 M Q O R
500 400 300
M
O G Q R
G
A P
200
A
100
Q AM A
P
A
C
C A
G
C G
R C R Q QO
Q G Q
P Q
G
0 10
20
30
40
50
60
70
80
Two-Theta(deg)
Figure 1 X-ray diffraction results of this tailing The eclogite tailing used in this work was obtained from the Rizhao concentrated garnet mill in China. The results of X-ray fluores-cence is presented in Table 1, indicating the grade of TiO2 was around 4.5%. In Fig.1, X-ray diffraction results are presented, showing that the tailing was composed of omphacite, garnet, mica, apitate, quartz, and rutile. The particle size distribution of this tailing was determined using standard sieves, it was shown that d10, d40, and d70 (diameters at a cumulative undersizing of 10%, 40%, and 70%, respectively) were 74, 300, and 600 μm, respectively.
In this study, lead (II) nitrate, n-octyl alcohol (OCT), and sodium fluorosilicate (SF) were purchased from Sinopharm Chemical Reagent Co., Ltd., China. The SPA was made in Zhuzhou, China. 2.2 Sample preparation The tailing used in the froth flotation was treated through a grinding process in a XMQ--240×90 conical ball mill with a volume of 6.5L, and the running speed was 96 r/ min. Although the garnet is difficult to levigate, some of the gangue minerals (mica and apatite) were easy to grind. And thus a large amount of slime is generated during the grinding. The flotation recovery will be poor when the ore is easily muddied. To solve the problem, a simple de-sliming process in this study via free sedimentation method was adopted. The pulp was first poured into a container whose diameter and volume are 20 cm and 2000 mL, respectively. Then adding water to dilute the pulp to the calibration of 2000 mL of the tank, and stirring well to ensure mix uniformly. After 1minute and 30 seconds standing, a rubber hose was inserted to the calibration of 800 mL to drain away the upper solution. The operation repeated 3 times. The ores used in this study all underwent a uniform de-sliming process, and the loss of TiO2 in the slime was less than 6 %. 2.3. Flotation Tests A rougher flotation experiment was carried out in an RK/FD type of single tank flotation machine with a volume of 1.5 L. In the chemical scheme, lead nitrate was used as an activator, and sodium fluorosilicate (SF) and sodium silicate (SS) were used as the depressor and slurry dispersant, respectively. Styryl phosphonic acid (SPA)
and n-octyl alcohol (OCT) were used as the composite collectors. And terpenic oil was served as frother.
Samples Lead nitrate Sodium fluorosilicate (SF) Sodium silicate (SS) SPA + OCT Terpenic oil
Rough concentrate
Tailing
Figure 2 Flowsheet of the rougher flotation test The flowsheet of the rougher flotation test is illustrated in Fig. 2. First, lead nitrate, sodium fluorosilicate (SF), sodium silicate (SS), and composite collectors were added in turn with an interval of 3 to 5 min. After that the conditioning continued for 1 min with terpenic oil addition. The forth flotation was performed for 90 s. In this study, the content of titanium dioxide was analyzed by ammonium ferric sulfate capacity method. 3. Results and Discussion The rougher flotation results obtained through this novel chemical scheme are presented in Table 2. The rougher concentrate with 84.47% TiO2 was floated with a recovery of 61.49%. The results indicated the scheme for the rutile separation was decent and the concentration ration via the rougher flotation was high. Furthermore, a closed-circuit experiment composed of a single rougher flotation, two-stage cleaner
flotation (including a black cleaner flotation) and two-stage scavenger flotation was performed, and the concentrate with the grade of 92% TiO2 and recovery of 70% was gained. Specifically, an acid pretreatment was usually carried out in Ti-bearing mineral flotation previously. However, an acid-base regulator is not required when using this scheme. Table 2 Results of rougher flotation test Product
Yield (%)
Grade (%)
Recovery (%)
concentrate
4.25
84.47
61.49
tailing
95.75
2.35
38.51
feed
100
5.84
100
Grade of rougher concentrate(%)
80 90 70 87
60 % Grade % Recovery
84
50 40
81
30 78 20 75 10
20
40
60
80
100
Recovery of rougher concentrate(%)
93
120
Flotation time(s)
Figure 3. Relationship between grade and recovery in the rutile flotation kinetics experiment using the proposed novel chemical scheme The results of the flotation kinetics experiment of the rougher flotation from the
proposed chemical scheme are illustrated in Fig 3. As indicated by the data in Fig 3, the chemical scheme can reach to be high-speed flotation. A concentrate with 90% TiO2 was achieved at around 10 s, and it only took 1 min to obtain a concentrate containing 81% TiO2 with a recovery of 64%. It indicated that the novel chemical scheme had an excellent collection capability and selectivity of rutile. Therefore, the capacity of the facilities and technical indicators can be improved with lower costs by using the novel chemical scheme. The optimum reagent dosage of the rougher flotation was achieved through a four-factor and three-level orthogonal experiment. The plans for this orthogonal experiment are described in Table 3. During the mathematical analysis, the mineral separation efficiency (E) was selected as an evaluation criterion for every test, and can be calculated using Hancock formula as follows.
E ( ) /(1 / m )(%)
(1)
βm is the content of TiO2 in a pure mineral, and has a value of 97% in this study. Table 3 Separation efficiency of every test during the orthogonal experiment
A（pb2+）
B(SF)
C(SS)
D(SPA)
Separation efficiency E (%)
1
(1)
(1)
(3)
(2)
31.48
2
(2)
(1)
(1)
(1)
40.52
3
(3)
(1)
(2)
(3)
37.83
4
(1)
(2)
(2)
(1)
29.45
5
(2)
(2)
(3)
(3)
45.56
6
(3)
(2)
(1)
(2)
51.98
Test number
Factors
7
(1)
(3)
(1)
(3)
47.49
8
(2)
(3)
(2)
(2)
42.05
9
(3)
(3)
(3)
(1)
14.64
E1
36.14
36.61
46.66
28.20
E2
42.71
42.33
36.44
41.84
E3
34.82
34.73
30.56
43.63
7.89
7.6
16.1
15.43
R= E max
E min
E 0 37.89
The factors A, B, C, and D represent pb2+, sodium fluorosilicate (SF), sodium silicate (SS), and styryl phosphonic acid (SPA), respectively. According to the mathematical analysis of the orthogonal experiment, the best dosage of combined reagents for rougher flotation is A2B2C1D3. Sodium silicate（SS）showed the most significant effect on the flotation. The separation efficiency (E) continuously dropped with an increasing dosage of SS. Sodium silicate (SS) was used as slurry dispersant; however, a clear inhibitory effect was presented with increasing dosage. Hence, a small amount of SS can not only fully disperse the clay, but also provide a suitable inhibiting effect on the gangue. Styryl phosphonic acid (SPA) is another major factor in the orthogonal experiment. The concentrate grade positively related to the SPA dosage in a suitable range of octanol (OCT) dosage. Some researchers have demonstrated that satisfactory results could be achieved due to the increasing hydrophobicity of the rutile caused by the co-adsorption of SPA and octanol (OCT) on its surface [6]. In the novel chemical scheme, the dosage of styryl phosphonic acid
(SPA) was 500-700 g/ton, and the octanol (OCT) was about 50-80 g/ton. In the rougher flotation, the mass ratio of styryl phosphonic acid and octanol was approximate 6. Suitable activator and inhibitor are crucial to the froth flotation of rutile due to its refractory. Thus, the effects of lead nitrate and sodium fluorosilicate (SF) on the flotation were verified via single-factor tests. It have been proved that lead ion has nice activation on Ti-containing minerals, and the adsorption capacity of Pb (II) ions on titanium nanotubes (TNT) was great[14]. The formation of the complex Ti-O-Pb+ mainly contributed to the improvement of rutile flotation have been convinced previously[15] . As well known, lead ion has an excellent activation on rutile. However, the synergistic effect between pb2+ and a composite collector (SPA and OCT) is scarcely investigated. Figure 4 illustrates the recovery of rougher concentrate as a function of its grade in the presence and absence of lead ion. The recovery vs. grade line with the addition of lead ion was located on the right side of that in the absence of lead ion, indicating that the adding lead ion in the cell could increase the recovery of the rougher concentrate. At the grade of 44% TiO2, the recovery of the scheme with lead ion achieved to 72%, while the scheme in the absence of lead ion reached to 52%. Moreover, the difference was much greater as the concentrate grade increased. Consequently, the addition of lead ion could obviously improve the rutile flotation.
Recovery of rougher concentrate(%)
80
70
60
50
40
30
20
% the scheme in the presence of lead ion % the scheme in the absence of lead ion
10 10
20
30
40
50
60
70
80
90
Grade of rougher concentrate(%)
Figure.4. Relationship between grade and recovery of TiO2 in rougher concentrate in the presence and absence of lead ion Sodium fluorosilicate (SF) is a very important inhibitor on the silicate gangue minerals. No unanimous conclusion on inhibitory mechanism of SF in flotation has been drawn due to the varied opinions. The effects of SF on a diaspore-rutile suspension were investigated, and it was found that the SiF62- absorbed on the diaspore surface, making it hydrophilic[16]. A flotation test showing the rutile response to different additions of SF using the proposed chemical scheme was conducted, the results of which are given in Fig 5. As shown in Fig.5, the rutile grade and recovery of the rougher concentrate both first increased and then reduced with the dosage of SF increased from 500 g/ton to 1500 g/ton. The optimum rutile grade and recovery of the concentrate were achieved when the dosage of SF was 1000 g/ ton, and an addition of more than 1000 g/ton dosage caused deterioration in the rutile flotation.
70
80
60
75 50 70 65
40
60 30 55
Grade Recovery
50
Recovery of rougher concentrate(%)
Grade of rougher concentrate(%)
85
20 600
800
1000
1200
1400
Dosage of sodium fluosilicate(g/ton)
Figure5.
Relationship between the SF dosage and rougher flotation results using proposed novel chemical scheme
4. Conclusions 1. A novel chemical scheme using styryl phosphonic acid (SPA), n-octyl alcohol (OCT), lead ion, sodium fluorosilicate (SF), and sodium silicate (SS) worked well on the flotation of eclogite-type rutile. All reagents were added at natural pH without acid pretreatment. 2. Lead nitrate and sodium fluorosilicate were extremely ideal regulators in the flotation of eclogite rutile. The roles of the appropriate regulators, in conjunction with efficient composite collectors, have pioneered an important avenue for the development of a serviceable chemical scheme in the actual production of eclogite rutile flotation. Acknowledgments
The financial supports for this work from the Ministry of Land and Resources of China (201511063-2), the Natural Science Foundation of Hubei Province of China (2016CFA013) and the Wuhan Science and Technology Bureau (2016070204020156) are gratefully acknowledged References 1. Suda, Y.; Morimoto, T.; Nagao, M. (1987) Adsorption of alcohols on titanium dioxide (rutile) surface. Langmuir, 3 (1) : 99. 2. Balos, S.; Sidjanin, L.; Dramicanin, M.; Labus, D.; Pilic, B.; Jovicic, M. (2016) Modification of cellulose and rutile welding electrode coating by infiltrated TiO2 nanoparticles. Metals and Materials International, 22 (3) : 509. 3. Herranz, M.; Rozas, S.; Pérez, C.; Idoeta, R.; Núñez-Lagos, R.; Legarda, F. (2013) Effective dose in the manufacturing process of rutile covered welding electrodes. Journal of Radiological Protection: Official Journal of the Society for Radiological Protection , 33 (1): 213. 4. Diebold, U. (2003) The surface science of titanium dioxide. Surface science reports, 48 (5): 53. 5. Wang, J.; Cheng, H. W.; Zhao, H. B.; Qin, W. Q.; Qiu, G. Z. (2016) Flotation behavior and mechanism of rutile with nonyl hydroxamic acid. Rare Metals, 35 (5) : 419. 6. Liu, Q.; Peng, Y. (1999) The development of a composite collector for the flotation of rutile. Minerals Engineering , 12 (12) : 1419. 7. Chachula, F.; Liu, Q. (2003) Upgrading a rutile concentrate produced from
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