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Article Hydrometallurgical Processing Technology of Titanomagnetite

Victor Ivanovich Sachkov 1 ID , Roman Andreevich Nefedov 1, Vladislav Viktorovich Orlov 1, Rodion Olegovych Medvedev 1,2 and Anna Sergeevna Sachkova 2,* ID

1 Innovative Technology Center, National Research Tomsk State University, Lenin Avenue 36, 634050 Tomsk, ; [email protected] (V.I.S.); [email protected] (R.A.N.); [email protected] (V.V.O.); [email protected] (R.O.M.) 2 School of Nuclear Science and , National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russia * Correspondence: [email protected]

Received: 7 November 2017; Accepted: 21 December 2017; Published: 24 December 2017

Abstract: In this paper, we study the possibility of obtaining and - concentrates with highest contents of iron and titanium, respectively, through hydrometallurgical processing of the titanomagnetite ores of the Chineisk deposit. We varied two key parameters to determine the efficiency of the process: (a) concentration of leaching solution (ammonium fluoride); and (b) acidity of solution. Ammonium fluoride concentration was varied from 0.08 mol/L to 4.2 mol/L with the other fixed parameters. It was shown that optimum ammonium fluoride concentration for leaching the is 0.42 mol/L; at these concentrations iron and titanium contents are about 62.8 wt % and 3.5 wt % in solid phase, respectively. The acidity of solution was changed by adding of hydrofluoric acid with varied concentration (from 0.86 mol/L to 4.07 mol/L) to ammonium fluoride solution with fixed concentration of 0.42 mol/L. The best results (degree of titanium extraction = 63.7%) were obtained when using a solution of hydrofluoric acid with concentration 4.07 mol/L. In this case, the addition of acid makes it possible to increase the Fe/Ti ratio by 3.4 times in comparison with the original ore. Thus, we conclude that acidity and the concentration of ammonium fluoride solution significantly influences the selectivity of the hydrometallurgical process.

Keywords: titanomagnetite ores; hydrometallurgical process; leaching; titanium-vanadium concentrates; iron concentrates; Fe/Ti ratio

1. Introduction Vanadium-containing titanomagnetite ores are among the most promising types of unconventional ores, and an important source of titanium, vanadium and iron [1–3]. The content of these components in the ore is sufficient for industrial extraction, though it can vary widely. About 6.5% of the proven ferrous ore reserves, more than 90% of V2O5 reserves and around 60% of TiO2 reserves are related to these industrial types of ores. In Russia, stocks of V2O5 and TiO2 account for 80% and 18.5%, respectively, in these ores. The world’s total reserves of titanomagnetites amount to tens of billions of tons [1,4–6] and about 50% of iron ore reserves of this type belong to the Russian Federation. More than 40 deposits in Russia have been discovered and estimated to varying degrees. The Chineisk vanadium-containing titanomagnetites field is located in the Northern Transbaikal area of the Baikal-Amur railway zone. It is one of the largest deposits in the world in terms of ore reserves (about 30 billion tons) [1,4]. The use of titanomagnetite ores for metallurgical processing is especially important due to the depletion of rich stocks. Besides, titanomagnetite ore processing can alleviate the shortage of the titanium raw materials.

Minerals 2018, 8, 2; doi:10.3390/min8010002 www.mdpi.com/journal/minerals Minerals 2018, 8, 2 2 of 12

Titanomagnetite ores have been actively used as a for cast iron, and vanadium salt production for centuries [1,2]. However, their processing technologies are continuously developing [1,2] in order to increase the recoveries of titanium and vanadium as well as the complex utilization of these raw materials. Titanomagnetite ore processing is a sophisticated large-scale production, which poses technological challenges and causes a number of ecological problems such as environmental pollution, land usage for tailing storage, the creation of sludge tanks for vanadium milling slimes, etc. [6]. There are two main methods for processing titanomagnetites—pyrometallurgical methods (reduction melting to form metallic iron and titanium sludge) [7–9] and high-temperature hydrometallurgical methods (autoclave leaching at elevated temperatures up to 200 ◦C and pressures up to 25–40 atm.) [10–12]. The disadvantages of the pyrometallurgical method include the large material and energy expenditures for titanomagnetite processing; titanium contained in the raw material is not extracted and is lost with the waste at different stages of the process. Moreover, one of the most important disadvantages of this method is that titanium remains in the processed materials and significantly reduces their quality. This is one of the reasons why the concentration of titanium in raw materials should be less than 4% [4]. Also, the chloride method of material processing based on the treatment of the ore by hydrochloric acid can be used. Disadvantages of this method include high costs for processing one ton of ore and negative impact on the environment. In addition, the usage of the chloride method as a technology for titanomagnetite ore processing is economically impractical due to the low content of titanium in such ores [13–16]. Consequently, the purpose of this research is to develop more cost-effective and efficient ways for complex hydrometallurgical processing of titanomagnetite with the possibility of obtaining iron and titanium-vanadium concentrates. One of the most appealing hydrometallurgical processing technologies is fluoride technology, which is due to the fact that the chemicals used are environmentally safe and relatively cheap [17]. Moreover, ammonium fluoride has good solubility in water; it is more reactive than many other inorganic fluorides. At room temperature, it is a relatively inert crystalline powder, and as a result poses no special environmental danger [18]. The basis of the ore processing by ammonium fluoride is that the oxygenated compounds of transition and non-transition elements in contact with NH4F form fluorometallates or oxofluorometallates favorable for further processing [18,19]. For instance, in [20] the possibility of TiO2 formation from ilmenite concentrate with the use of ammonium fluoride is presented. The processing of ilmenite concentrate in this work was performed with aqueous solutions of fluoride and ammonium bifluoride at 100–108 ◦C and pyro-hydrolysis of fluorine-containing titanium salts at 800–900 ◦C. Thus, the urgent task is to develop an effective, low-cost and environmentally friendly ammonium-fluoride-based hydrometallurgical technology, to obtain iron and titanium-vanadium concentrates from titanomagnetite ores.

2. Materials and Methods In the current work, we used a titanomagnetite ore from the Chineisk deposit (Chita region). This ore is granular with size about 2 mm (the ore was provided by public corporation Zabaikalstalinvest, Novaya Chara, Russia). The leaching of the titanium from the ore was simulated in agitators. It was performed using aqueous solutions of ammonium fluoride in a wide range of concentrations (from 0.08 to 4.2 mol/L). The mass of each ore sample leached was 150 g. The ratio of solid:liquid was 1:3. The interaction between titanomagnetite ore and ammonium fluoride occurred according the following equation:

FeTiO3·Fe3O4 + 12NH4F + 0.25O2 = (NH4)3FeF6 + (NH4)2TiF6 + Fe3O4 + 3.5H2O + 7NH3 (1) Minerals 2018, 8, 2 3 of 12

Another way of titanium extraction involved adding hydrofluoric acid to the ammonium fluoride solutions. The HF concentration in ammonium fluoride solutions varied from 0.86 to 4.07 mol/L, while the concentration of ammonium fluoride solutions was held constant 0.42 mol/L. The mass of each ore sample was 150 g with the solid:liquid ratio of 1:3. The interaction between titanomagnetite ore, ammonium fluoride, and hydrofluoric acid occurred according to the reaction:

FeTiO3·Fe3O4 + 6NH4F + 6HF + 0.25O2 = (NH4)3FeF6 + (NH4)2TiF6 + Fe3O4 + 3.5H2O + NH3 (2)

The experiments were conducted in 1000-mL polyethylene agitators with constant stirring for 20 h at room temperature. Solid and liquid fractions were separated using a Nutsche filter. The resulting solid residue was washed with distilled water and dried at 120 ◦C. The determination of phase composition and structural parameters for the samples was carried out at the Center of Materials Science for Collective Use of Tomsk State University, Tomsk, Russia. The study was conducted using a XRD-6000 diffractometer (Shimadzu, Japan) with CuKα-radiation = 1.54056 Å, and 2θ in the range of 10◦–80◦. The phase composition was analyzed with the use of PDF databases 4+ and the full-profile analysis software PowderCell 2.4 (Germany) [21]. The titanium and iron concentration in the solution, and the elemental composition of the ore were determined by inductively coupled plasma atomic emission spectrometry using an ICAP 6200 DUO spectrometer (Thermo Scientific, Waltham, MA, USA). We then calculated the weight percentage of iron and titanium in the solid phases of the ore and the Fe/Ti ratio (Fe content, wt %, Ti content, wt %, at the solid phase), using the X-ray diffraction data. Thus, the extraction efficiency (ω %) of titanium and iron was calculated as the ratio of the mass of the component in the liquid phase to the mass of this component in the initial ore expressed in percentage terms: m(component in the liquid phase) ω = ·100% (3) n(component in the initial phase)

3. Results and Discussion

3.1. Titanomagnetite Composition After crushing the ore, the granulometric composition was determined. The results are presented in Table1.

Table 1. Granulometric size composition of the crushed titanomagnetite ore from the Chineisk deposit.

Size of Particles, mm Mass Fraction, wt % 3–1 9.06 1–0.5 42.35 0.5–0.25 22.77 0.25–0.125 16.32 <0.125 8.79

As given in Table1, particles with size range from 0.5 to 1 mm dominated in the ore. Figure1 shows the X-ray diffraction (XRD) data on a sample of titanomagnetite ore from the Chineisk deposit in Chita region. According to the XRD analyses, the samples consisted of several phases. Tables2 and3 illustrate the mineralogical composition of titanomagnetite ore from the Chineisk deposit and the elemental composition of the ore, respectively. Minerals 2018, 8, 2 4 of 12 Minerals 2017, 8, 2 4 of 12

Figure 1. X-ray diffraction (XRD) patterns of titanomagnetite ore of the Chineisk deposit: (1)—Fe O , Figure 1. X‐ray diffraction (XRD) patterns of titanomagnetite ore of the Chineisk deposit: (1)—Fe3 4 3O4, (2)—FeTiO3, (3)—MgFe2O4, (4)—Fe3((FeSi)O5)(OH)4, (5)—AlFe monoclinic. (2)—FeTiO3, (3)—MgFe2O4, (4)—Fe3((FeSi)O5)(OH)4, (5)—AlFe monoclinic.

Table 2. Mineralogical composition of titanomagnetite ore from the Chineisk deposit by XRD (%). According to the XRD analyses, the samples consisted of several mineral phases. Tables 2 and 3 illustrate the mineralogical composition of titanomagnetite ore from the Chineisk deposit and the Content Mass Fraction, wt % Lattice Parameters, Å Size of the Coherent Scattering Region, nm elemental composition of the ore, respectively. Fe3O4 40 a = 8.3937 82 a = 5.1370 FeTiO 25 30 Table 2.3 Mineralogical composition of titanomagnetitec = 14.1697 ore from the Chineisk deposit by XRD (%).

MgFeContent2O4 Mass Fraction,8 wt % Latticea =Parameters 8.4064 , Å Size of the Coherent45 Scattering Region, nm Fe3O4 40 а a == 5.4804 8.3937 82 Fe ((FeSi)O )(OH) 15 60 3 5 4 ca = = 14.1467 5.1370 FeTiO3 25 30 ac = = 15.589014.1697 AlFeMgFe monoclinic2O4 128 ba = = 8.18078.4064 4045 ca = = 12.3760 5.4804 Fe3((FeSi)O5)(OH)4 15 60 c = 14.1467 Table 3. The elementala = composition 15.5890 of the ore (ICP). AlFe monoclinic 12 b = 8.1807 40 c = 12.3760 Element Mass Fraction, wt % Element Mass Fraction, wt %

Table 2 reveals thatFe magnetite (Fe 53.03O4) and ilmenite Na (FeTiO3) dominate 0.106 in the ore. The ore also included such impuritiesO as magnesioferrite 24.5 (М Co.gFe2O4), cronstedtite 0.0992 Fe3((FeSi)O5)(OH)4 and Ti 8.82 Cu 0.0992 epidote‐monoclinic (AlFe). The magnetite and magnesioferrite was characterized by cubic crystal Si 5.89 Cr 0.0711 lattice, the ilmenite andAl cronstedtite 4.34had hexagonal crystal S lattice, 0.0471 and the epidote had monoclinic crystal lattice. Ca 1.25 Cl 0.0365 Mg 0.960 Ni 0.0295 V 0.447 Zn 0.0242 Table 3. The elemental composition of the ore (ICP). Mn 0.159 Element Mass Fraction, wt % Element Mass Fraction, wt %

Table2 revealsFe that magnetite (Fe53.03 O4) and ilmeniteNa (FeTiO3) dominate0.106 in the ore. The ore also included such impuritiesO as magnesioferrite24.5 (MgFeCo.2O 4), cronstedtite0.0992 Fe 3((FeSi)O5)(OH)4 and epidote-monoclinicTi (AlFe). The magnetite8.82 and magnesioferriteCu was characterized0.0992 by cubic crystal lattice, the ilmeniteSi and cronstedtite5.89 had hexagonal crystalCr lattice, and0.0711 the epidote had monoclinic crystal lattice. Al 4.34 S 0.0471 As shown in TableCa 3, the iron content1.25 was 53.0 wtCl %, the titanium0.0365 content was 8.82 wt %, and the Fe/Ti ratioMg was 6.01. Thus,0.960 the titanomagnetite Ni ore of the Chineisk0.0295 deposit is a promising raw material and canV be considered0.447 as a huge resourceZn for the production0.0242 of iron and titanium- vanadium concentrates.Mn 0.159

As shown in Table 3, the iron content was 53.0 wt %, the titanium content was 8.82 wt %, and the Fe/Ti ratio was 6.01. Thus, the titanomagnetite оrе of the Chineisk deposit is a promising raw material and can be considered as a huge resource for the production of iron and titanium‐vanadium concentrates.

Minerals 2017, 8, 2 5 of 12 Minerals 2017, 8, 2 5 of 12 Minerals 2018, 8, 2 5 of 12 3.2. Concentration of Ammonium Fluoride and Processing Efficiency 3.2. Concentration of Ammonium Fluoride and Processing Efficiency 3.2.This Concentration section presents of Ammonium the results Fluoride of studying and Processing the possibility Efficiency for titanomagnetite ore processing throughThis the sectionselective presents recovery the of results titanium of studyingby solutions the possibilitythat contain for ammonium titanomagnetite and fluoride ore processing ions. Thethrough interactionThis the section selective of the presents titanomagnetite recovery the results of titanium of with studying ammoniumby solutions the possibility fluoride that contain for in titanomagnetite the ammonium presence of oreand processing fluoride as anions. through the selective recovery of titanium by solutions that contain ammonium and fluoride ions. oxidizingThe interaction agent proceeds of the accordingtitanomagnetite to the reactionwith ammonium 1. In the experiments, fluoride in thewe variedpresence the ofconcentration oxygen as an The interaction of the titanomagnetite with ammonium fluoride in the presence of oxygen as an of oxidizingammonium agent fluoride proceeds from according 0.08 to 4.2 to mol/L, the reaction the temperature 1. In the experiments, was 20–25 we°C, variedthe leaching the concentration duration oxidizing agent proceeds according to the reaction 1. In the experiments, we varied the concentration equaledof ammonium 20 h, and fluoride the solid:liquid from 0.08 ratio to 4.2was mol/L, 1:3. the temperature was 20–25 °C, the leaching duration of ammonium fluoride from 0.08 to 4.2 mol/L, the temperature was 20–25 ◦C, the leaching duration equaledThe results 20 h, andof the the experiments solid:liquid areratio presented was 1:3. in the form of diagrams: titanium content in solid equaled 20 h, and the solid:liquid ratio was 1:3. and liquidThe phases results vs. of concentrationthe experiments of ammoniumare presented fluoride in the (Figureform of 2);diagrams: iron content titanium in solid content and liquid in solid and liquidThe results phases of vs. the concentration experiments are of ammonium presented in fluoride the form (Figure of diagrams: 2); iron titanium content content in solid in and solid liquid phasesand liquidvs. concentration phases vs. concentration of ammonium of ammonium fluoride (Figure fluoride 3); (Figure the iron2); iron and content titanium in solid content and liquidin solid phases vs. concentration of ammonium fluoride (Figure 3); the iron and titanium content in solid phasephases vs. vs.concentration concentration of ofammonium ammonium fluoride fluoride (Figure (Figure3 4).); the iron and titanium content in solid phase phase vs. concentration of ammonium fluoride (Figure 4). vs. concentration of ammonium fluoride (Figure4).

FigureFigure 2. Titanium 2. Titanium content content in in the the solid solid and and liquid liquid phases phases vs. concentration ofof ammoniumammonium fluoride. fluoride. (1)Figure (1)—Mass—Mass 2. fraction Titanium fraction of of Ticontent Ti in in solid solid in phasethe phase solid (wt (wt and%); (2)—Concentrationliquid phases vs. concentration of of Ti Ti in in liquid liquid phaseof phase ammonium (g/L). (g/L). fluoride. (1) —Mass fraction of Ti in solid phase (wt %); (2)—Concentration of Ti in liquid phase (g/L).

FigureFigure 3. 3.IronIron content content inin the the solid solid and and liquid liquid phases phases vs. concentration vs. concentration of ammonium of ammonium fluoride. (1)—Mass fluoride. (1)—MassFigurefraction 3.fraction of Iron Fe in content solidof Fe phase in insolid (wtthe phase %);solid (2)—Concentration (wt and %); liquid (2)—Concentration phases of Fe vs. in liquidconcentration of Fe phase in liquid (g/L). of phaseammonium (g/L). fluoride. (1)—Mass fraction of Fe in solid phase (wt %); (2)—Concentration of Fe in liquid phase (g/L).

Minerals 2017, 8, 2 6 of 12 Minerals 2018, 8, 2 6 of 12 Minerals 2017, 8, 2 6 of 12

Figure 4. Iron and titanium content in solid phase vs. concentration of ammonium fluoride. (1)—Mass fraction of Fe in solid phase (wt %); (2)—Mass fraction of Ti in solid phase (wt %). FigureFigure 4. 4.IronIron and and titanium titanium content content in in solid solid phase phase vs. vs. concentration concentration of of ammonium ammonium fluoride. fluoride. (1)—Mass (1)—Mass fraction of Fe in solid phase (wt %); (2)—Mass fraction of Ti in solid phase (wt %). fractionTable 4 of illustrates Fe in solid content phase (wt of %);the (2)—Mass phases in fraction the solid of Ti residue in solid obtainedphase (wt %).during the processing of titanomagnetite ore by the ammonium fluoride with concentration of 4.2 mol/L. TableTable 44 illustrates illustrates content content of the phases inin thethe solid solid residue residue obtained obtained during during the the processing processing of of titanomagnetite ore by the ammonium fluoride with concentration of 4.2 mol/L. titanomagnetiteTable 4. XRD ore analysis by the ofammonium the solid residue fluoride by with ammonium concentration fluoride ofsolution 4.2 mol/L. with concentration of 4.2Table mol/L. 4. XRD analysis of the solid residue by ammonium fluoride solution with concentration of Table 4. XRD analysis of the solid residue by ammonium fluoride solution with concentration of 4.2 mol/L. 4.2 mol/L. Content Mass Fraction, wt % (NH4)3FeF6 91 ContentContent Mass Fraction,Mass Fraction wt % , wt % Fe3O4 5 (NH(NH4)43)FeF3FeF6 6 91 91 FeFe2OO3 5 4 Fe3O3 4 4 5 Fe2O3 4 The experimental data analysisFe 2Oshowed3 that the extent 4of ore leaching increased with the increase in the ammonium fluoride solution concentration. According to the results of X‐ray TheThe experimental experimental data analysisanalysis showed showed that that the extentthe extent of ore of leaching ore leaching increased increased with the increase with the diffraction and atomic emission spectrometry, the extraction rate of titanium from solid phase to the increasein the ammoniumin the ammonium fluoride solution fluoride concentration. solution concentration. According to According the results ofto X-ray the diffractionresults of andX‐ray solution increased with the increase in ammonium fluoride concentration in the leaching solution. diffractionatomic emission and atomic spectrometry, emission the spectrometry, extraction rate the of extraction titanium from rate solid of titanium phase to from the solution solid phase increased to the The lowest content of titanium in solid phase of 1.9 wt % was achieved in ore products that were solutionwith the increased increase inwith ammonium the increase fluoride in ammonium concentration fluoride in the leaching concentration solution. in The the lowestleaching content solution. of treated with 4.2 mol/L ammonium fluoride solution (Figure 2). Titanium extraction at this Thetitanium lowest incontent solid phase of titanium of 1.9 wt in %solid was phase achieved of 1.9 in orewt products% was achieved that were in treated ore products with 4.2 that mol/L were ammonium fluoride concentration was 78.5% (Figure 5) and this was the maximum achieved. treatedammonium with fluoride4.2 mol/L solution ammonium (Figure2). fluoride Titanium solution extraction (Figure at this ammonium 2). Titanium fluoride extraction concentration at this However, selective titanium extraction was only found with ammonium fluoride concentration up ammoniumwas 78.5% (Figurefluoride5) andconcentration this was the was maximum 78.5% achieved. (Figure However,5) and this selective was the titanium maximum extraction achieved. was to 1 mol/L. However,only found selective with ammonium titanium extraction fluoride concentration was only found up to with 1 mol/L. ammonium fluoride concentration up to 1 mol/L.

FigureFigure 5. 5. TiTi and and Fe Fe extraction extraction vs. concentration of of ammonium ammonium fluoride. fluoride. Figure 5. Ti and Fe extraction vs. concentration of ammonium fluoride.

Minerals 2017, 8, 2 7 of 12 Minerals 2018, 8, 2 7 of 12 The separation of iron and titanium occurred due to the formation of water‐soluble (NH4)2TiF6 and partially soluble in water (NH4)3FeF6. The effective separation of these elements was achieved by varyingThe the separation concentration of iron of andthe reagents titanium occurredin the leaching due to solution. the formation of water-soluble (NH4)2TiF6 and partially soluble in water (NH ) FeF . The effective separation of these elements was achieved by The ion content in the solid phase4 3 increased6 with ammonium fluoride concentration from 0.08 varying the concentration of the reagents in the leaching solution. to 0.42 mol/L (Figures 3–5). With further increase in ammonium fluoride concentration in the leaching The ion content in the solid phase increased with ammonium fluoride concentration from 0.08 to solution, iron dissolved to a greater extent, and its mass fraction in the solid phase decreased affecting 0.42 mol/L (Figures3–5). With further increase in ammonium fluoride concentration in the leaching the quality of ferrous concentrate (Figure 4) and leading to an increased consumption of the solution, iron dissolved to a greater extent, and its mass fraction in the solid phase decreased affecting ammoniumthe quality fluoride. of ferrous This concentrate is due to (Figure the formation4) and leading of (NH to an4)3FeF increased6 ammonium consumption hexafluoroferrate of the ammonium (III) in which iron mass fraction was 25 wt % of the residue. Insoluble magnesium fluoride MgF2 and calcium fluoride. This is due to the formation of (NH4)3FeF6 ammonium hexafluoroferrate (III) in which iron fluoride CaF2 were also produced by reaction of magnesium and calcium with the ammonium mass fraction was 25 wt % of the residue. Insoluble magnesium fluoride MgF2 and calcium fluoride fluoride. These fluorides are used as fluxes in [22]. The water‐soluble complexes CaF2 were also produced by reaction of magnesium and calcium with the ammonium fluoride. 4 3 6 4 2 6 4 3 6 (NHThese) [AlF fluorides], (NH are) SiF used and as fluxes(NH ) inVF steelmaking were formed [22]. from The water-soluble reaction of the complexes leaching (NH solution4)3[AlF with6], aluminum,(NH4)2SiF silicon6 and (NH and4 )vanadium.3VF6 were formed As a result, from aluminum, reaction of the silicon leaching and solution vanadium with were aluminum, extracted silicon to the solution,and vanadium. while calcium As a result, and magnesium aluminum, remained silicon and in vanadium the iron concentrate. were extracted to the solution, while calciumBased and upon magnesium the iron content remained of the in thesolid iron phase concentrate. (iron concentrate) the optimum ammonium fluoride concentrationsBased upon to generate the iron content an iron of concentrate the solid phase are (iron from concentrate) 0.42 to 1 mol/L. the optimum Having ammonium varied ammonium fluoride fluorideconcentrations concentrations to generate in this an range, iron concentratethe iron content are from was increased 0.42 to 1 mol/L. from 53.0 Having to 60.2–62.8 varied ammoniumwt % and the titaniumfluoride content concentrations decreased in this from range, 8.8 theto 3.5–4.6 iron content wt % was in increasedsolid phase from (iron 53.0 concentrate). to 60.2–62.8 wt Titanium % and extractionthe titanium was content47.8–60.3%. decreased from 8.8 to 3.5–4.6 wt % in solid phase (iron concentrate). Titanium extraction was 47.8–60.3%. 3.3. HF Concentration and Processing Efficiency 3.3. HF Concentration and Processing Efficiency The influence of acidity on the production of concentrates was studied. The acidity of the The influence of acidity on the production of concentrates was studied. The acidity of the leaching leaching solution was changed by adding hydrofluoric acid to ammonium fluoride solution. As solution was changed by adding hydrofluoric acid to ammonium fluoride solution. As presented presented in Section 2, the interaction of titanomagnetite ore with ammonium fluoride after in Section2, the interaction of titanomagnetite ore with ammonium fluoride after introducing the introducinghydrofluoric the acid hydrofluoric and in the presenceacid and of in oxygen the presence as an oxidizing of oxygen agent as occurred an oxidizing according agent to reaction occurred according(2). Hydrofluoric to reaction acid (2). concentration Hydrofluoric was acid varied concentration from 0.86 towas 4.07 varied mol/L from with 0.86 the otherto 4.07 parameters mol/L with thefixed other and parameters using optimum fixed and concentration using optimum of ammonium concentration fluoride of ammonium of 0.42 mol/L fluoride (Figures of3 0.42 and 4mol/L); (Figures20–25 ◦C,3 and leaching 4); 20–25 duration—20 °C, leaching h, (solid:liquid duration—20 was 1:3). h, The (solid:liquid results of the was experiments 1:3). The areresults presented of the experimentsin Figures6 are and presented7. in Figures 6 and 7.

FigureFigure 6. 6.IronIron and and titanium titanium content content in in solid solid phase vs. concentration of of hydrofluoric hydrofluoric acid acid for for a fixeda fixed ammoniumammonium fluoride fluoride concentration concentration of of 0.42 0.42 mol/L. mol/L. (1)—Mass (1)—Mass fraction fraction of Fe inin solidsolid phasephase, (wt (wt %); %); (2)—Mass fraction of Ti in solid phase (wt %). (2)—Mass fraction of Ti in solid phase, (wt %).

It Itwas was found found thatthat when when increasing increasing hydrofluoric hydrofluoric acid concentration, acid concentration, the titanium the content titanium decreased content decreasedwhile the while iron content the iron simultaneously content simultaneously increased in increased the solid phase.in the Usingsolid aphase. solution Using of hydrofluoric a solution of hydrofluoricacid with concentration acid with concentration of 4.07 mol/L of and4.07 ammonium mol/L and fluorideammonium with fluoride concentration with concentration of 0.42 mol/L, of 0.42 mol/L, the titanium content in solid phase decreased from 8.82 to 3.2 wt %, and the iron content increased from 53.0 to 65.6 wt %. The extraction of titanium in this case was increased from 47.8 to

Minerals 2018, 8, 2 8 of 12

Mineralsthe titanium 2017, 8, 2 content in solid phase decreased from 8.82 to 3.2 wt %, and the iron content increased8 of 12 from 53.0 to 65.6 wt %. The extraction of titanium in this case was increased from 47.8 to 63.7%. Thus, 63.7%.the intensificationThus, the intensification of the process of the after process the addition after the of hydrofluoric addition of hydrofluoric acid may be due acid to may the factbe due that to − ‐ + + thethe fact increase that the in increase F ions concentrationin F ions concentration as well as the as unchangedwell as the concentrationunchanged concentration of (NH4) ions of in (NH the4) ionssolution in the solution lead to the lead increase to the in increase the yield in of the ammonium yield of ammonium hexafluorotitanate hexafluorotitanate (IV). (IV).

FigureFigure 7. Extraction 7. Extraction Ti Ti and and Fe Fe vs. vs. HF HF concentration concentration for for a fixed fixed ammonium fluoride fluoride concentration concentration of of 0.420.42 mol/L. mol/L.

AsAs can can be be seen seen from from Figure Figure 7,7 ,the the change change in the concentration of of hydrofluoric hydrofluoric acid acid at at a constanta constant concentrationconcentration of ofammonium ammonium fluoride fluoride had had no no significant significant effect effect on thethe extractionextraction of of iron. iron. At At the the same same time,time, the the increase increase of of concentration concentration in in the the hydrofluoric hydrofluoric acid substantially increasedincreased the the extraction extraction of of thethe titanium. titanium. TableTable 5 demonstrates5 demonstrates that that most most of of the the iron iron remained inin thethe oxide form, form, which which positively positively affected affected thethe quality quality of ofthe the iron iron concentrate concentrate and and the the consumption consumption of the leachingleaching reagents. reagents.

Table 5. XRD analysis of the solid residue with 0.42 mol/L concentration of ammonium fluoride Table 5. XRD analysis of the solid residue with 0.42 mol/L concentration of ammonium fluoride solution and hydrofluoric acid with concentration of 4.07 mol/L. solution and hydrofluoric acid with concentration of 4.07 mol/L.

ContentContentMass Mass Fraction Fraction,, wt wt %% FeFe3O34O 4 31 Fe2O3 47 Fe2O3 47 FeTiO3 10 3 Fe3((FeSi)OFeTiO 5)(OH)4 1210 Fe3((FeSi)O5)(OH)4 12 3.4. The Fe/Ti Ratio 3.4. The Fe/Ti Ratio The changes in the ratio of iron to titanium in the solid products were studied. Figures8 and9 presentThe changes the influence in the ofratio the of ammonium iron to titanium fluoride in concentration the solid products and HF were concentration studied. Figures on the 8 Fe/Ti and 9 presentratio, the respectively. influence of the ammonium fluoride concentration and HF concentration on the Fe/Ti ratio, respectively.The data analysis (Figure8) indicates the increase in the Fe/Ti ratio from 6.011 to 17.2 when leaching with ammonium fluoride solution with concentration up to 1 mol/L. The Fe/Ti ratio decreased slightly with the further increase in concentration. Hydrofluoric acid addition (Figure9) enabled the Fe/Ti ratio to increase to 20.5 (i.e., 3.4 times) thus confirming the synergistic effect of acidity and ammonium fluoride on upgrading the iron content of the solid phase. The best results for the hydrometallurgical processing of titanomagnetite ore are presented in Table6.

Minerals 2017, 8, 2 9 of 12

Minerals 2018, 8, 2 9 of 12 Minerals 2017, 8, 2 9 of 12

Figure 8. The Fe/Ti ratio in solid samples vs. concentration of ammonium fluoride.

The data analysis (Figure 8) indicates the increase in the Fe/Ti ratio from 6.011 to 17.2 when leaching with ammonium fluoride solution with concentration up to 1 mol/L. The Fe/Ti ratio decreased slightlyFigureFigure with 8. 8.The The the Fe/Ti Fe/Ti further ratio ratio increase in in solid solid samples samplesin concentration. vs. vs. concentration concentration of of ammonium ammonium fluoride. fluoride.

The data analysis (Figure 8) indicates the increase in the Fe/Ti ratio from 6.011 to 17.2 when leaching with ammonium fluoride solution with concentration up to 1 mol/L. The Fe/Ti ratio decreased slightly with the further increase in concentration.

Figure 9. TheThe Fe/Ti Fe/Ti ratio ratio in in solid solid samples samples vs. vs. HF HF concentration concentration for for a a fixed fixed ammonium fluoride fluoride concentrationconcentration of 0.42 mol/L.

HydrofluoricTable 6. Impact acid of ammonium addition fluoride(Figure and 9) enabled hydrofluoric the acidFe/Ti concentrations ratio to increase on the to composition 20.5 (i.e., 3.4 of the times) thus ferrousconfirmingFigure concentrate 9. The the Fe/Ti synergistic obtained ratio in by solideffect leaching samples of titanomagnetiteacidity vs. HFand concentration ammonium ore from the for fluoride Chineisk a fixed deposit. onammonium upgrading fluoride the iron contentconcentration of the solid of phase. 0.42 mol/L. The best results for the hydrometallurgical processing of titanomagnetite Mass Fraction in Ferrous ore are presented in Table 6. Ti Recovery to Fe/Ti Ratio in Ferrous Leaching Solution Concentrate (Solid Phase), wt % Hydrofluoric acid addition (Figure 9) enabled the Fe/Ti Solution,ratio to %increaseConcentrate to 20.5 (i.e., (Solid 3.4 Phase) times) thus confirming the synergisticFe effect of acidity Ti and ammonium fluoride on upgrading the iron contentCM(NH 4ofF) the = 0.42 solid mol/L phase. The 62.8 best results for the 4.6 hydrometallurgical 47.8 processing of titanomagnetite 13.6 CM(NH4F) = 1 mol/L 60.2 3.5 60.3 17.2 oreC are(NH presentedF) = 0.42 mol/L in Table 6. M 4 65.6 3.2 63.7 20.5 CM(HF) = 4.07 mol/L

Thus, the presented results can be used for processing titanomagnetite ores in technological scale and the heap leaching on this technology is an optimal method of ore processing due to an involvement in the process of significant volumes of the processed ore. Processing schematic diagram is presented in Figure 10.

Minerals 2017, 8, 2 10 of 12

Table 6. Impact of ammonium fluoride and hydrofluoric acid concentrations on the composition of the ferrous concentrate obtained by leaching titanomagnetite ore from the Chineisk deposit.

Mass Fraction in Ferrous Concentrate Ti Recovery to Fe/Ti ratio in Ferrous Leaching Solution (Solid Phase), wt % Solution, % Concentrate (Solid Phase) Fe Ti

CM(NH4F) = 0.42 mol/L 62.8 4.6 47.8 13.6

CM(NH4F) = 1 mol/L 60.2 3.5 60.3 17.2

CM(NH4F) = 0.42 mol/L 65.6 3.2 63.7 20.5 CM(HF) = 4.07 mol/L

Thus, the presented results can be used for processing titanomagnetite ores in technological scale and the heap leaching on this technology is an optimal method of ore processing due to an involvement in the process of significant volumes of the processed ore. Processing schematic diagram is presented in Figure 10. As follows from the diagram (Figure 10), the ore is treated by the leaching solution of the required composition. Precipitation of the titanium concentrate by ammonium hydroxide is the next stage after a partial extraction of the titanium. The usage of ammonium hydroxide allows using the solutions as cycling solutions that, after adjusting the concentration, are returned to the leaching stage. After the extraction of a predetermined amount of titanium from the ore, the heap is an iron concentrate that is suitable for further metallurgical processing. The usage of ammonium hydroxide enables the recycling of the spent solution to the leaching step after the concentration has been adjusted. Varying the concentration of reagents in the leaching solution makes it possible to obtain the iron concentrate‐containing fluorides in an amount that does not interfere with the pyrometallurgical reduction of iron. Also, the fluorides of magnesium and Mineralscalcium2018 formed, 8, 2 during leaching can be used as fluxes. Their use allows better and faster separate10 of 12 and slags, and contributes to the removal of impurities, especially and [22].

Figure 10. Processing schematic diagram for titanomagnetite. Figure 10. Processing schematic diagram for titanomagnetite. 4. Conclusions As follows from the diagram (Figure 10), the ore is treated by the leaching solution of the required composition.The development Precipitation of hydrometallurgical of the titanium concentrate processing by ammoniumtechnology for hydroxide titanomagnetite is the next ores stage such after as afrom partial the extractionChineisk deposit of the titanium. of Chita region The usage has been of ammonium considered. hydroxide It was shown allows that using ore thewhich solutions contains as cyclingFe (53.0%), solutions Ti (8.8%), that, and after with adjusting the Fe/Ti the ratio concentration, of 6.011 is a areprospective returned raw to the material leaching for stage. the production After the extractionof titanium of‐vanadium a predetermined and iron amount concentrates. of titanium from the ore, the heap is an iron concentrate that is suitableThe for possibility further metallurgical for titanomagnetite processing. ore processing through the selective recovery of titanium usingThe solutions usage ofthat ammonium contain ammonium hydroxide and enables fluorine the recyclingions has been of the demonstrated. spent solution We to achieved the leaching the step78.5% after titanium the concentration content in the has beensolution adjusted. by treating Varying the the ore concentration with ammonium of reagents fluoride in the solution leaching of solution makes it possible to obtain the iron concentrate-containing fluorides in an amount that does not interfere with the pyrometallurgical reduction of iron. Also, the fluorides of magnesium and calcium formed during leaching can be used as fluxes. Their use allows better and faster separate metals and slags, and contributes to the removal of impurities, especially sulfur and phosphorus [22].

4. Conclusions The development of hydrometallurgical processing technology for titanomagnetite ores such as from the Chineisk deposit of Chita region has been considered. It was shown that ore which contains Fe (53.0%), Ti (8.8%), and with the Fe/Ti ratio of 6.011 is a prospective raw material for the production of titanium-vanadium and iron concentrates. The possibility for titanomagnetite ore processing through the selective recovery of titanium using solutions that contain ammonium and fluorine ions has been demonstrated. We achieved the 78.5% titanium content in the solution by treating the ore with ammonium fluoride solution of concentration 4.2 mol/L. However, it was shown that optimum ammonium fluoride concentrations for ore processing with iron concentrate formation are from 0.42 to 1 mol/L. At these concentrations, the iron content increased from 53.0 to 62.8 wt % and the titanium content decreased from 8.8 to 3.5 wt % in solid phase. The impact of acidity on the process to obtain concentrates has also been investigated. It was found that increasing HF concentration (from 0.86 mol/L to 4.07 mol/L) leads to an increase in Fe contained in the solid phase. The condition for increasing the iron content in the ore was obtained using a concentration for hydrofluoric acid of 4.07 mol/L in 0.42 mol/L ammonium fluoride solution. The content of titanium in the solid phase was reduced to 3.2 wt %, and the iron content was increased to 65.6 wt %. In addition, the extraction of titanium was 63.7%, which significantly increased the Fe/Ti ratio to 20.5, i.e., 3.4 times higher than for the original ore. Minerals 2018, 8, 2 11 of 12

The results indicate that acidity and ammonium fluoride concentration of the leaching solution are the most important factors for efficiently and selectively processing titanomagnetite ores. This manuscript has shown that these ores can be effectively upgraded by a hydrometallurgical method, which is based on the interaction of titanomagnetite and ammonium fluoride.

Acknowledgments: The results were obtained within the framework of the state task of the Ministry of and Science of the Russian Federation, project No. 10.3031.2017/4.6. Author Contributions: Victor Ivanovich Sachkov and Roman Andreevich Nefedov conceived of the presented idea and designed the experiments; Vladislav Viktorovich Orlov and Rodion Olegovych Medvedev performed experiments and analyzed the data; Anna Sergeevna Sachkova wrote the manuscript. Conflicts of Interest: The authors declare no conflict of interest.

References

1. Deryabin, Y.A. Equilibrium composition of and slag in reductive of binary batch based on Chineisk and Korshunovo concentrates. Transl. 2007, 37, 83–88. [CrossRef] 2. Bhattacharyya, A.; Mitra, M.K.; Mitra, T.; Das, G.C.; Mukherjee, S. Processing of titanium bearing magnetite ore of Soltora (West Bengal) for the liberation of titania by . J. Inst. Eng. Part MM Metall. Mater. Sci. Div. 2003, 84, 23–26. 3. Cheng, X.; Yimin, Z.; Tao, L.; Jing, H. Characterization and pre-concentration of low-grade vanadium- titanium magnetite ore. Minerals 2017, 7, 137. [CrossRef] 4. Deryabin, Y.A.; Smirnov, L.A.; Deryabin, A.A. Perspektivy pererabotki chineiskikh titanomagnetitov. In Prospects for Processing Chineisk Titanomagnetites; Sredne-Ural’skoe Kn. Izd.: Yekaterinburg, Russia, 1999. 5. Zhen, Q.; Zuxing, L.; Zhenhua, H. Metallogenetic Characteristics of Panzhihua-Tipe Vanadium-Bearing Titano-Magnetite Deposits. In Proceedings of the International Symposium on Exploitation and Utilization of Vanadium-Bearing Titanomagnetite, Panzhihua, , 14–16 November 1989; The Metallurgical Press: Beijing, China, 1989; pp. 1–19. 6. Reznichenko, V.A.; Shabalin, V.I. Titanomagnetites: Deposits, Metallurgy, Chemical Technology; Nauka: Moscow, Russia, 1986. (In Russian) 7. Sun, H.; Wang, J.; Dong, X.; Xue, Q. A literature review of titanium slag metallurgical processes. Metalurgia Int. 2012, 17, 49–56. 8. Parfenov, O.G.; Pashkov, G.L. Problemy Sovremennoi Metallurgii Titana (Problems of Modern Metallurgy of Titanium); Sib. Otd. Ross. Akad. Nauk: Novosibirsk, Russia, 2008; p. 279, ISBN 978-5-7692-0987-1. (In Russian) 9. Dmitriev, A.N.; Mukhitdinov, Y.S.; Rakhimov, V.R.; Sitdikov, F.G. Pyrometallurgical technology for processing titanomagnetites from the Tebinbulak deposit. Metallurgist 2005, 49, 41–43. [CrossRef] 10. Zhang, W.; Zhu, Z.; Cheng, C.Y. A literature review of titanium metallurgical processes. Hydrometallurgy 2011, 108, 177–188. [CrossRef] 11. Sedneva, T.A.; Lokshin, E.P.; Gromov, P.B.; Kopkova, E.K.; Shchelokova, E.A. Decomposing the titaniferous magnetite concentrate with hydrochloric acid. Theor. Found. Chem. Eng. 2011, 45, 753–763. [CrossRef] 12. Wang, H.B.; Jiang, K.X.; Shi, Y.F.; Zhang, B.S. New technology for production of synthetic rutile by pressure leaching and preparation of sponge titanium by molten salt electrolysis. Rare. Met. Mater. Eng. 2006, 35, 78. 13. Haverkamp, R.G.; Kruger, D.; Rajashekar, R. The digestion of New Zealand ilmenite by hydrochloric acid. Hydrometallurgy 2016, 163, 198–203. [CrossRef] 14. Wahyuningsih, S.; Pramono, E.; Firdiyono, F.; Sulistiyono, E.; Budi Rahardjo, S.; HIdayattullah, H.; Anatolia, F.A. Decomposition of ilmenite in hydrochloric acid to obtain high grade titanium dioxide. Asian J. Chem. 2013, 25, 6791–6794. 15. Ogasawara, T.; de Araujo, R.V.V. Hydrochloric acid leaching of a pre-reduced Brazilian ilmenite concentrate in an autoclave. Hydrometallurgy 2000, 56, 203–216. [CrossRef] 16. Jain, S.K.; Jena, P.K. Hydrochloric-acid leaching of Gopalpur ilmenite. Indian J. Technol. 1977, 15, 398–402. 17. Andreev, A.A.; Diachenko, A.N. Conditions for the production of pigmentary titanium dioxide of rutile and anatase modifications by ilmenite processing with ammonium fluoride. Theor. Found. Chem. Eng. 2009, 43, 707–712. [CrossRef] Minerals 2018, 8, 2 12 of 12

18. Laptash, N.M.; Maslennikova, I.G. Fluoride processing of titanium-containing minerals. Adv. Mater. Phys. Chem. 2012, 2, 21–24. [CrossRef] 19. Bakeeva, N.G.; Gordienko, P.S.; Parshina, E.V. Mutual influence of ammonium hexafluorotitanate and hexafluorosilicate in ammonium fluoride solutions. Russ. J. Gen. Chem. 2010, 80, 223–226. [CrossRef] 20. Gordienko, P.S.; Didenko, N.A.; Goncharuk, V.K.; Bakeeva, N.G.; Pasnina, E.V. Method of Preparing Titanium Dioxide (in Russian). Russian Patent N 2130428, 20 May 1999. 21. Kraus, W.; Nolze, G. PowderCell 2.0 for Windows. 1998. Available online: http://www.ccp14.ac.uk/ccp/ web-mirrors/powdcell/a_v/v_1/powder/details/powcell.htm (accessed on 10 September 2017). 22. Kokal, H.R.; Ranade, M.G. Metallurgical Uses—Fluxes for Metallurgy. Ind. Miner. Rocks 1994, 15, 661–675.

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