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Selective flotation of fluorite from barite using trisodium phosphate as a depressant
Minerals Engineering 134 (2019) 390–393
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Short communication
Selective flotation of fluorite from barite using trisodium phosphate as a depressant ⁎
T
⁎
Cheng Liua,b, , Shaoxian Songa,b, , Hongqiang Lic a
Hubei Key Laboratory of Mineral Resources Processing and Environment, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070, China School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China c School of Xingfa Mining Engineering, Wuhan Institute of Technology, Wuhan, Hubei 430205, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Fluorite Barite Flotation separation Depressant Trisodium phosphate
In this paper, trisodium phosphate (TSP) was utilized for the flotation separation of fluorite from barite. Microflotation results showed that good floatability of both fluorite and barite was obtained at around pH 8.5 using sodium oleate (NaOL) as a collector. TSP showed a selective depression for barite, and flotation separation of fluorite from barite was achieved using TSP as a depressant and NaOL as a collector. Zeta potential measurements indicated that the addition of TSP prior to NaOL did not prevent the adsorption of NaOL on fluorite surface while it prevented NaOL to adsorb on barite surface.
1. Introduction
be ionized as H2PO4−, HPO42− and PO43− in the water solution. These species can interact with metal ions such as iron and barium ions, etc., and then form complex/precipitate (Wang and Hu, 1988). The Ba sites at the barite surface might interact with TSP and change the surface properties of barite, then probably affecting the flotation behavior of barite. However, the application of TSP for the separation of fluorite from barite has not been reported. In this work, TSP was found to be a novel depressant for barite depression in the flotation of fluorite. The work was accomplished by means of various techniques, including micro-flotation tests, zeta potential measurements and solution chemistry calculation.
Fluorite is the primary source of fluorine and is one of the important nonmetal mineral raw materials. Fluorite has been widely used in refrigeration, pesticide, and other industries (Zhu et al., 2018; Gao et al., 2018). Currently, many developed countries regard fluorite as an important strategic reserve supplies (Li and Gao, 2018; Gao et al., 2016). Fluorite commonly coexists with calcite (Gao et al., 2016; Wang et al, 2018), and also usually is associated with barite (Śla¸czka, 1987). In practice, the commonly used method for separation of fluorite from its gangue minerals is flotation (Huang et al., 2018, 2019; Liu et al., 2018, 2019a, 2019b), and the commonly used collectors in fluorite flotation are fatty acids or fatty acid derivatives (Gao et al., 2019; Filippova et al., 2018). However, these collectors also interact with Ba sites at the barite surface. Hence, separation of fluorite from barite is impossible without depressants when fatty acid is used as a collector. To achieve good flotation separation of fluorite from barite, especially in China, a number of depressants were investigated, such as mixed aluminum sulfate, water glass and tannin extract depressant (Yu et al., 2011), and mixed sodium fluorosilicate, dextrin, tannin extract and sodium hexametaphosphate depressant, etc. (Dong, 1996). However, the complex mixed depressants will cause a serious problem for waste water treatment because of various pollutant species. Hence, the separation of fluorite from barite ores is still a challenge. TSP is an anionic inorganic reagent (Chen et al., 2018), which can
2. Materials and methods 2.1. Pure minerals and reagents The pure fluorite and barite samples were obtained from Jinhua, Zhejiang, China. The samples were crushed to −1 mm and ground using an agate mortar. The products were then dry sieved and the products in the −74 to +37 μm size range were collected for microflotation tests. X-ray diffraction analysis demonstrated that the purities of these two samples were very high (Fig. A1 in Supplementary Material). Analytical grade NaOl, which was obtained from Aladdin Industrial Corporation, Shanghai, China, was used as the collector. Analytical
⁎ Corresponding authors at: Hubei Key Laboratory of Mineral Resources Processing and Environment, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070, China. E-mail addresses: [email protected] (C. Liu), [email protected] (S. Song).
https://doi.org/10.1016/j.mineng.2019.02.008 Received 6 November 2018; Received in revised form 16 January 2019; Accepted 3 February 2019 0892-6875/ © 2019 Elsevier Ltd. All rights reserved.
Minerals Engineering 134 (2019) 390–393
C. Liu, et al.
grade TSP (Na3PO4·12H2O), obtained from Sinopharm Chemical Reagent co. LTD, was used as the depressant. NaOH and HCl were utilized as the pH modifiers in the experiments. Distilled water with a minimum resistivity of 18.2 mΩ cm was used for all tests.
Table 1 Flotation results of mixed fluorite and barite.
2.2. Micro-flotation tests Micro-flotation tests were performed in an XFGC-1600 flotation machine. 2 g mineral samples were mixed with 40 mL deionized water in the plexiglass cell for each test. The pH of the pulp was adjusted by NaOH and HCl. Depressants (when required) and collectors were added sequentially into the suspension, and the conditioning time for each reagent was 3 min. The flotation was conducted for 4 min. For single mineral tests, the floated and unfloated products were collected. The dry weights of the two products were measured and used to calculate the recovery. Each test was measured three times, and the average value and the standard deviation was calculated. For mineral mixture, the floated and unfloated products were assayed for CaF2 and used to calculate the recovery.
Reagents
Products
Yield (w/%)
CaF2 grade (%)
CaF2 recovery (%)
TSP: 100 mg/L NaOl: 1.5 × 10−4 mol/L TSP: 125 mg/L NaOl: 1.5 × 10−4 mol/L
Concentrate Tailings Feed Concentrate Tailings Feed
76.92 23.08 100.00 75.57 24.43 100.00
92.89 37.72 80.16 93.93 37.55 80.16
89.14 10.86 100.00 88.56 11.44 100.00
two minerals was around 90%, which is attributed to the interaction of oleate species with Ca or Ba ions on mineral surface (Wang and Hu,1988), indicating that it is difficult to separate fluorite and barite without depressants. Fig. 1 also shows that when the TSP was added prior to NaOl, the flotation recovery of the barite decreased with the increase of pH value until pH 8.0 and then remained constant, with a minimum barite recovery of approximately 5%. Regarding fluorite, the flotation recovery of fluorite changed slightly as compared to the result for using NaOl alone. Therefore, the optimum pH to separate fluorite from barite is deemed to be pH 8–9.5 when using TSP as the depressant and NaOl as the collector. The single mineral flotation results show that it may be possible to separate fluorite from barite with TSP in the presence of NaOl. Therefore, flotation tests of mixed fluorite and barite (the mass ratio is 4:1) were conducted at pH 8.5 using different dosages of TSP and the best results achieved were shown in Table 1. It can be seen from Table 1 that a concentrate with a CaF2 grade of 92.89% and recovery of 89.14% was obtained with 100 mg/L TSP. When the TSP dosage increased to be 125 mg/L, the concentrate grade and recovery of CaF2 changed slightly, suggesting that TSP presents a good performance for separation of fluorite from barite when NaOl is used as collector.
2.3. Zeta potential measurements Zeta potential measurements were performed using Malvern Instrument Nano-ZS90 analyzer. −5 μm samples (40 mg) were mixed with 80 mL 1 × 10−3 mol/L KNO3 background electrolyte solution and the mixed samples were dispersed in the presence of desired reagent scheme at a determined pH. After 10 min of settling, the supernatant was collected for zeta-potential measurements. The zeta-potential of each sample was measured three times. The average was reported as the final value and the standard deviation was calculated. 3. Results and discussion 3.1. Micro-flotation results A series experiments (see Figs. A2 and A3 in Supplementary Material) were performed to obtain the reagent scheme, and the effect of pH on the flotation behavior of fluorite and barite with and without TSP in the presence of NaOl was presented in Fig. 1. It can be seen from Fig. 1 that in the presence of NaOl alone, good floatability of both fluorite and barite is obtained in the entire studied pH range, especially at the routinely performed pH range (i.e., 7–10). The recovery of the
3.2. Zeta potential results Fig. 2 described the zeta potentials of fluorite and barite as a function of pH. The isoelectric point of bare fluorite located at pH 8.0, and the zeta potential of barite was negative at pH 6–11, similar to the previous studies (Jiang et al., 2018; Liu, 2010). Fig. 2 presents that the addition of TSP causes a decrease by 15 mV and 20 mV in zeta potential of fluorite and barite, respectively at pH 8.5, indicating TSP can adsorb onto fluorite and barite surface. After the addition of NaOl, the zeta potential of fluorite decreased by 27 mV compared to that of fluorite treated with TSP alone at pH 8.5, illustrating that pre-treatment of fluorite with TSP did not prevent the adsorption of NaOl on fluorite surface. Regarding barite, conditioning the TSP pre-treated barite with NaOl, the zeta potential of barite changed slightly compared to that of barite with TSP alone at around pH 8.5, indicating that the TSP addition can prevent the adsorption of NaOl on barite surface. The species distribution diagrams of TSP and NaOl as a function of pH are shown in Fig. 3 and help to explain the zeta potential results. Fig. 3 presents that H3PO4 species dominate at pH < 2.4, H2PO4− species dominate at pH 2.4–7.2, HPO42− species dominate at pH 7.2–12, and PO43− species at pH > 12, respectively (Wang and Hu, 1988). In the case of NaOl, oleate ions exist mainly as RCOOH(l) below pH 8.2 whereas oleate ions are predominantly in the form of RCOO− and R(COO)22− above pH 8.2 (Liu et al., 2019c). At approximately pH 8.5, the negatively charged HPO42− species are expected to interact with Ca sites and exist as CaHPO4 complex or/and CaHPO4·H2O precipitation on fluorite surface at pH 8.5. In the case of barite, the HPO42− species can interact with Ba sites and then exist as BaHPO4 or/ and Ba3(PO4)2·H2O precipitation on barite surface (Wang and Hu, 1988), the CaHPO4 complex or/and CaHPO4·H2O precipitation center
Fig. 1. Effect of pH on the flotation behavior of fluorite and barite [TSP:100 mg/L; NaOl: 1.5 × 10−4 mol/L]. 391
Minerals Engineering 134 (2019) 390–393
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Fig. 2. Effect of reagent adding on the zeta potential of fluorite and barite as a function of pH (TSP = 100 mg/L, NaOl = 1.5 × 10−4 mol/L).
Fig. 3. Species distribution diagrams of TSP (a), NaOL (b) as a function of pH.
selective separation of fluorite from barite using NaOL as a collector.
also can interact with NaOl (oleate ions replaced phosphate group and interacted with Ca sites) and achieve good floatability of fluorite. However, the BaHPO4 or/and Ba3(PO4)2·H2O precipitation center probably inhibited the adsorption of NaOl (oleate ions can not replace phosphate group and interact with Ba sites) on barite surface, which might be attributed to the solubility product of Ba3(PO4)2·H2O precipitation (pKsp = 36.6) is far higher than that of barium oleate (pKsp = 15.4) while the solubility product of CaHPO4·H2O precipitation (pKsp = 6.58) is far lower than that of calcium oleate (Wang and Hu, 1988). However, the reason why NaOl does not interact with BaHPO4 or/and Ba3(PO4)2·H2O precipitations needs more investigation.
Acknowledgements The authors acknowledge the support of the National Natural Science Foundation of China (No. 51804238) and Independent Innovation Fund of Wuhan University of Technology, China (No. 193208002). Appendix A. Supplementary material Supplementary data to this article can be found online at https:// doi.org/10.1016/j.mineng.2019.02.008.
4. Conclusion
References
The micro-flotation tests presented that TSP exhibited selective depression for barite in fluorite flotation, which achieves the flotation separation of fluorite from barite at approximately pH 8.5 when using NaOl as a collector. Zeta potential measurements and solution chemistry calculation indicated that the dominate species HPO42− of TSP adsorbed on both fluorite and barite. However, the pre-adsorption of TSP interfered with the adsorption of NaOl on the barite surfaces while did not interfere with the adsorption of NaOl on fluorite surface. These findings indicated that TSP can be used as a potential depressant in the
Śla¸czka, Andrzej St., 1987. Effects of an ultrasonic field on the flotation selectivity of barite from a barite-fluorite-quartz ore. Int. J. Miner. Process. 20, 193–210. Chen, W., Feng, Q.M., Zhang, G.F., Yang, Q., 2018. Investigations on flotation separation of scheelite from calcite by using a novel depressant: Sodium phytate. Miner. Eng. 126, 116–122. Dong, F.Z., 1996. Research on the separation of fluorite and barite. Build. Mater. New Technol. 2 (23–25), 38 (in Chinese). Filippova, I., Filippov, L., Lafhaj, Z., Barres, O., Fornasiero, D., 2018. Effect of calcium minerals reactivity on fatty acids adsorption and flotation. Colloids Surf. A
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Liu, C., Zhang, W.C., Song, S.S., Li, H.Q., 2019a. A novel method to improve carboxymethyl cellulose performance in the flotation of talc. Miner. Eng. 131, 23–27. Liu, C., Song, S., Li, H.Q., Li, Y.B., Ai, G.H., 2019b. Elimination of the adverse effect of calcite slimes on the sulfidization flotation of malachite in the presence of water glass. Colloids Surf. A Physicochem. Eng. Asp. 563, 324–329. Liu, C., Zhu, G.L., Song, S., Li, H.Q., 2019c. Flotation separation of smithsonite from quartz using calcium lignosulphonate as a depressant and sodium oleate as a collector. Miner. Eng. 131, 385–397. Liu, N.Y., 2010. Research on removing sulfur-bearing gangue (barite type) from hematite. Central South University Ph.D Thesis (in Chinese). Wang, J., Zhou, Z.H., Gao, Y.S., Sun, W., Hu, Y.H., Gao, Z.Y., 2018. Reverse flotation separation of fluorite from calcite: A novel reagent scheme. Minerals 8 (313), 1–7. Wang, D.Z., Hu, Y.H., 1988. Solution Chemistry of Flotation. Hunan Science and Technology Press. Yu, F.T., Gao, H.M., Shi, W.T., Cao, W., Ren, Z.J., 2011. Experimental research on comprehensive utilization of fluorite ore for a lead-zinc Mine Tailings in Hunan. Met. Mine 422 (8), 162–165 (in Chinese). Zhu, H.L., Qin, W.Q., Chen, C., Chai, L.Y., Jiao, F., Jia, W.H., 2018. Flotation separation of fluorite from calcite using polyaspartate as depressant. Miner. Eng. 120, 80–86.
Physicochem. Eng. Asp. 545, 157–166. Huang, Z., Cheng, C., Li, L., et al., 2018. Morpholine-based Gemini surfactant: synthesis and its application for reverse froth flotation of carnallite ore in potassium fertilizer production. J. Agric. Food Chem. 66, 13126–13132. Huang, Z., Cheng, C., Li, L., et al., 2019. Flotation of sylvite from potash ore by using the Gemini surfactant as a novel flotation collector. Miner. Eng. 132, 22–26. Jiang, W., Gao, Z.Y., Khoso, S.A., Gao, J.D., Sun, W., Pu, W., Hu, Y.H., 2018. Selective adsorption of benzhydroxamic acid on fluorite rendering selective separation of fluorite/calcite. Appl. Surf. Sci. 435, 752–758. Gao, Z.Y., Gao, Y.S., Zhu, Y.Y., Hu, Y.H., Sun, W., 2016. Selective flotation of calcite from fluorite: a novel reagent scheme. Minerals 6 (114), 1–8. Gao, Z.Y., Xie, L., Cui, X., Hu, Y.H., Sun, W., Zeng, H.B., 2018. Probing anisotropic surface properties and surface forces of fluorite crystals. Langmuir 34 (7), 2511–2521. Gao, Z.Y., Fan, R.Y., Ralston, J., Sun, W., Hu, Y.H., 2019. Surface broken bonds: an efficient way to assess the surface behaviour of fluorite. Miner. Eng. 130, 15–23. Li, C., Gao, Z.Y., 2018. Tune surface physicochemical property of fluorite particles by regulating the exposure degree of crystal surfaces. Miner. Eng. 128, 123–132. Liu, C., Ai, G., Song, S., 2018. The effect of amino trimethylene phosphonic acid on the flotation separation of pentlandite from lizardite. Powder Technol. 336, 527–532.
393
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Short communication
Selective flotation of fluorite from barite using trisodium phosphate as a depressant ⁎
T
⁎
Cheng Liua,b, , Shaoxian Songa,b, , Hongqiang Lic a
Hubei Key Laboratory of Mineral Resources Processing and Environment, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070, China School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China c School of Xingfa Mining Engineering, Wuhan Institute of Technology, Wuhan, Hubei 430205, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Fluorite Barite Flotation separation Depressant Trisodium phosphate
In this paper, trisodium phosphate (TSP) was utilized for the flotation separation of fluorite from barite. Microflotation results showed that good floatability of both fluorite and barite was obtained at around pH 8.5 using sodium oleate (NaOL) as a collector. TSP showed a selective depression for barite, and flotation separation of fluorite from barite was achieved using TSP as a depressant and NaOL as a collector. Zeta potential measurements indicated that the addition of TSP prior to NaOL did not prevent the adsorption of NaOL on fluorite surface while it prevented NaOL to adsorb on barite surface.
1. Introduction
be ionized as H2PO4−, HPO42− and PO43− in the water solution. These species can interact with metal ions such as iron and barium ions, etc., and then form complex/precipitate (Wang and Hu, 1988). The Ba sites at the barite surface might interact with TSP and change the surface properties of barite, then probably affecting the flotation behavior of barite. However, the application of TSP for the separation of fluorite from barite has not been reported. In this work, TSP was found to be a novel depressant for barite depression in the flotation of fluorite. The work was accomplished by means of various techniques, including micro-flotation tests, zeta potential measurements and solution chemistry calculation.
Fluorite is the primary source of fluorine and is one of the important nonmetal mineral raw materials. Fluorite has been widely used in refrigeration, pesticide, and other industries (Zhu et al., 2018; Gao et al., 2018). Currently, many developed countries regard fluorite as an important strategic reserve supplies (Li and Gao, 2018; Gao et al., 2016). Fluorite commonly coexists with calcite (Gao et al., 2016; Wang et al, 2018), and also usually is associated with barite (Śla¸czka, 1987). In practice, the commonly used method for separation of fluorite from its gangue minerals is flotation (Huang et al., 2018, 2019; Liu et al., 2018, 2019a, 2019b), and the commonly used collectors in fluorite flotation are fatty acids or fatty acid derivatives (Gao et al., 2019; Filippova et al., 2018). However, these collectors also interact with Ba sites at the barite surface. Hence, separation of fluorite from barite is impossible without depressants when fatty acid is used as a collector. To achieve good flotation separation of fluorite from barite, especially in China, a number of depressants were investigated, such as mixed aluminum sulfate, water glass and tannin extract depressant (Yu et al., 2011), and mixed sodium fluorosilicate, dextrin, tannin extract and sodium hexametaphosphate depressant, etc. (Dong, 1996). However, the complex mixed depressants will cause a serious problem for waste water treatment because of various pollutant species. Hence, the separation of fluorite from barite ores is still a challenge. TSP is an anionic inorganic reagent (Chen et al., 2018), which can
2. Materials and methods 2.1. Pure minerals and reagents The pure fluorite and barite samples were obtained from Jinhua, Zhejiang, China. The samples were crushed to −1 mm and ground using an agate mortar. The products were then dry sieved and the products in the −74 to +37 μm size range were collected for microflotation tests. X-ray diffraction analysis demonstrated that the purities of these two samples were very high (Fig. A1 in Supplementary Material). Analytical grade NaOl, which was obtained from Aladdin Industrial Corporation, Shanghai, China, was used as the collector. Analytical
⁎ Corresponding authors at: Hubei Key Laboratory of Mineral Resources Processing and Environment, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070, China. E-mail addresses: [email protected] (C. Liu), [email protected] (S. Song).
https://doi.org/10.1016/j.mineng.2019.02.008 Received 6 November 2018; Received in revised form 16 January 2019; Accepted 3 February 2019 0892-6875/ © 2019 Elsevier Ltd. All rights reserved.
Minerals Engineering 134 (2019) 390–393
C. Liu, et al.
grade TSP (Na3PO4·12H2O), obtained from Sinopharm Chemical Reagent co. LTD, was used as the depressant. NaOH and HCl were utilized as the pH modifiers in the experiments. Distilled water with a minimum resistivity of 18.2 mΩ cm was used for all tests.
Table 1 Flotation results of mixed fluorite and barite.
2.2. Micro-flotation tests Micro-flotation tests were performed in an XFGC-1600 flotation machine. 2 g mineral samples were mixed with 40 mL deionized water in the plexiglass cell for each test. The pH of the pulp was adjusted by NaOH and HCl. Depressants (when required) and collectors were added sequentially into the suspension, and the conditioning time for each reagent was 3 min. The flotation was conducted for 4 min. For single mineral tests, the floated and unfloated products were collected. The dry weights of the two products were measured and used to calculate the recovery. Each test was measured three times, and the average value and the standard deviation was calculated. For mineral mixture, the floated and unfloated products were assayed for CaF2 and used to calculate the recovery.
Reagents
Products
Yield (w/%)
CaF2 grade (%)
CaF2 recovery (%)
TSP: 100 mg/L NaOl: 1.5 × 10−4 mol/L TSP: 125 mg/L NaOl: 1.5 × 10−4 mol/L
Concentrate Tailings Feed Concentrate Tailings Feed
76.92 23.08 100.00 75.57 24.43 100.00
92.89 37.72 80.16 93.93 37.55 80.16
89.14 10.86 100.00 88.56 11.44 100.00
two minerals was around 90%, which is attributed to the interaction of oleate species with Ca or Ba ions on mineral surface (Wang and Hu,1988), indicating that it is difficult to separate fluorite and barite without depressants. Fig. 1 also shows that when the TSP was added prior to NaOl, the flotation recovery of the barite decreased with the increase of pH value until pH 8.0 and then remained constant, with a minimum barite recovery of approximately 5%. Regarding fluorite, the flotation recovery of fluorite changed slightly as compared to the result for using NaOl alone. Therefore, the optimum pH to separate fluorite from barite is deemed to be pH 8–9.5 when using TSP as the depressant and NaOl as the collector. The single mineral flotation results show that it may be possible to separate fluorite from barite with TSP in the presence of NaOl. Therefore, flotation tests of mixed fluorite and barite (the mass ratio is 4:1) were conducted at pH 8.5 using different dosages of TSP and the best results achieved were shown in Table 1. It can be seen from Table 1 that a concentrate with a CaF2 grade of 92.89% and recovery of 89.14% was obtained with 100 mg/L TSP. When the TSP dosage increased to be 125 mg/L, the concentrate grade and recovery of CaF2 changed slightly, suggesting that TSP presents a good performance for separation of fluorite from barite when NaOl is used as collector.
2.3. Zeta potential measurements Zeta potential measurements were performed using Malvern Instrument Nano-ZS90 analyzer. −5 μm samples (40 mg) were mixed with 80 mL 1 × 10−3 mol/L KNO3 background electrolyte solution and the mixed samples were dispersed in the presence of desired reagent scheme at a determined pH. After 10 min of settling, the supernatant was collected for zeta-potential measurements. The zeta-potential of each sample was measured three times. The average was reported as the final value and the standard deviation was calculated. 3. Results and discussion 3.1. Micro-flotation results A series experiments (see Figs. A2 and A3 in Supplementary Material) were performed to obtain the reagent scheme, and the effect of pH on the flotation behavior of fluorite and barite with and without TSP in the presence of NaOl was presented in Fig. 1. It can be seen from Fig. 1 that in the presence of NaOl alone, good floatability of both fluorite and barite is obtained in the entire studied pH range, especially at the routinely performed pH range (i.e., 7–10). The recovery of the
3.2. Zeta potential results Fig. 2 described the zeta potentials of fluorite and barite as a function of pH. The isoelectric point of bare fluorite located at pH 8.0, and the zeta potential of barite was negative at pH 6–11, similar to the previous studies (Jiang et al., 2018; Liu, 2010). Fig. 2 presents that the addition of TSP causes a decrease by 15 mV and 20 mV in zeta potential of fluorite and barite, respectively at pH 8.5, indicating TSP can adsorb onto fluorite and barite surface. After the addition of NaOl, the zeta potential of fluorite decreased by 27 mV compared to that of fluorite treated with TSP alone at pH 8.5, illustrating that pre-treatment of fluorite with TSP did not prevent the adsorption of NaOl on fluorite surface. Regarding barite, conditioning the TSP pre-treated barite with NaOl, the zeta potential of barite changed slightly compared to that of barite with TSP alone at around pH 8.5, indicating that the TSP addition can prevent the adsorption of NaOl on barite surface. The species distribution diagrams of TSP and NaOl as a function of pH are shown in Fig. 3 and help to explain the zeta potential results. Fig. 3 presents that H3PO4 species dominate at pH < 2.4, H2PO4− species dominate at pH 2.4–7.2, HPO42− species dominate at pH 7.2–12, and PO43− species at pH > 12, respectively (Wang and Hu, 1988). In the case of NaOl, oleate ions exist mainly as RCOOH(l) below pH 8.2 whereas oleate ions are predominantly in the form of RCOO− and R(COO)22− above pH 8.2 (Liu et al., 2019c). At approximately pH 8.5, the negatively charged HPO42− species are expected to interact with Ca sites and exist as CaHPO4 complex or/and CaHPO4·H2O precipitation on fluorite surface at pH 8.5. In the case of barite, the HPO42− species can interact with Ba sites and then exist as BaHPO4 or/ and Ba3(PO4)2·H2O precipitation on barite surface (Wang and Hu, 1988), the CaHPO4 complex or/and CaHPO4·H2O precipitation center
Fig. 1. Effect of pH on the flotation behavior of fluorite and barite [TSP:100 mg/L; NaOl: 1.5 × 10−4 mol/L]. 391
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Fig. 2. Effect of reagent adding on the zeta potential of fluorite and barite as a function of pH (TSP = 100 mg/L, NaOl = 1.5 × 10−4 mol/L).
Fig. 3. Species distribution diagrams of TSP (a), NaOL (b) as a function of pH.
selective separation of fluorite from barite using NaOL as a collector.
also can interact with NaOl (oleate ions replaced phosphate group and interacted with Ca sites) and achieve good floatability of fluorite. However, the BaHPO4 or/and Ba3(PO4)2·H2O precipitation center probably inhibited the adsorption of NaOl (oleate ions can not replace phosphate group and interact with Ba sites) on barite surface, which might be attributed to the solubility product of Ba3(PO4)2·H2O precipitation (pKsp = 36.6) is far higher than that of barium oleate (pKsp = 15.4) while the solubility product of CaHPO4·H2O precipitation (pKsp = 6.58) is far lower than that of calcium oleate (Wang and Hu, 1988). However, the reason why NaOl does not interact with BaHPO4 or/and Ba3(PO4)2·H2O precipitations needs more investigation.
Acknowledgements The authors acknowledge the support of the National Natural Science Foundation of China (No. 51804238) and Independent Innovation Fund of Wuhan University of Technology, China (No. 193208002). Appendix A. Supplementary material Supplementary data to this article can be found online at https:// doi.org/10.1016/j.mineng.2019.02.008.
4. Conclusion
References
The micro-flotation tests presented that TSP exhibited selective depression for barite in fluorite flotation, which achieves the flotation separation of fluorite from barite at approximately pH 8.5 when using NaOl as a collector. Zeta potential measurements and solution chemistry calculation indicated that the dominate species HPO42− of TSP adsorbed on both fluorite and barite. However, the pre-adsorption of TSP interfered with the adsorption of NaOl on the barite surfaces while did not interfere with the adsorption of NaOl on fluorite surface. These findings indicated that TSP can be used as a potential depressant in the
Śla¸czka, Andrzej St., 1987. Effects of an ultrasonic field on the flotation selectivity of barite from a barite-fluorite-quartz ore. Int. J. Miner. Process. 20, 193–210. Chen, W., Feng, Q.M., Zhang, G.F., Yang, Q., 2018. Investigations on flotation separation of scheelite from calcite by using a novel depressant: Sodium phytate. Miner. Eng. 126, 116–122. Dong, F.Z., 1996. Research on the separation of fluorite and barite. Build. Mater. New Technol. 2 (23–25), 38 (in Chinese). Filippova, I., Filippov, L., Lafhaj, Z., Barres, O., Fornasiero, D., 2018. Effect of calcium minerals reactivity on fatty acids adsorption and flotation. Colloids Surf. A
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