Flotation of Titanium Minerals

Transcription

1 25 Flotation of Titanium Minerals 25.1 INTRODUCTION Titanium is the most abundant metal in the earth crust, and is present in excess of 0.62%. It can be found as dioxy titanium and the salts of titanium acids. Titanium is capable of forming complex anions representing simple titanites. It can also be found in association with niobium, silicates, zircon and other minerals. A total of 70 titanium minerals are known, as mixtures with other minerals and also impurities. Only a few of these minerals are of any economic importance. This chapter discusses flotation properties of major titanium minerals and beneficiation methods used in some operating plants. In recent years, a new technology has been developed for beneficiation of hard rock titanium minerals. This is also discussed in this chapter TITANIUM-BEARING ORES AND MINERALS Out of the 70 known titanium minerals, only a few have any economic value. Table 25.1 shows the major titanium minerals of value. The most important titanium minerals are ilmenite, rutile and perovskie. Loparite is a major mineral for production of niobium and REO Ilmenite Ilmenite has variable titanium content, depending on the iron content and other impurities, and ranges from 45% to 52% TiO 2. It can be found in a variety of ore types, along with rutile, apatite, zircon, columbite, etc Ilmenorutile This mineral contains up to 53% TiO 2 and 32% Nb 2 O 5 along with 14.5% Ta 2 O 5. The composition of ilmenorutile is variable, and often is considered to be a niobium mineral. 175

2 Flotation of Titanium Minerals Table 25.1 Important titanium minerals of economic value Mineral Formula Theoretical Specific gravity Hardness grade % TiO 2 (g/cm 3 ) Ilmenite FeTiO Rutile TiO Ilmenorutile a (Ti,Nb,Fe)O Perovskite CaTiO Sphene CaOTiO 2 SiO Loparite (Na,Ce,Sr,Ca)(Nb,Ti)O Lucoxene TiO 2.TiO 2.SiO Titanomagnetite b b Fe 3 O 4 FeTiO a If Nb content is high, this mineral belongs to a group of niobium minerals. b Or Fe3O 4 TiO Rutile Rutile is the most stable of all the titanium minerals. In a number of cases, rutile may contain impurities such as iron oxides, tin, chromium and vanadium. The rutile grade can range from 95% to 99% TiO Perovskite Perovskite is a calciumtitanium mineral and usually contains impurities of iron, chromium and aluminium. The theoretical grade can vary from 50% to 57% TiO 2. Also, sometimes contains niobium (up to 11%) and tantalum Leucoxene Leucoxene has a composition similar to that of rutile, and is a product of alterations of a number of titanium minerals, most often ilmenite and sphene. It contains higher amounts of titanium, compared to ilmenite, and can range from 61% to 75% TiO CLASSIFICATION OF TITANIUM DEPOSITS Titanium minerals have been recovered from both hard rock and sand deposits. Until 1945, most of the ilmenite and rutile produced commercially came from sand deposits, but nowadays, the production of ilmenite from rock deposits exceeds that of sand deposits. Rutile, however, is exclusively produced from sand deposits, although a new technology exists that recovers rutile from rock deposits.

3 25.4 Flotation Properties of Major Titanium Minerals Rock deposits Anorthositic deposits nearly all of the known commercially important rock deposits of titanium minerals are associated with anorthositic or gabbroic rocks. There are three main types: (a) ilmenitemagnetite (titanoferous magnetite), (b) ilmenitehaematite, and (c) ilmeniterutile. The ilmenitemagnetite deposits usually contain ilmenite and magnetite as granular intergrowths, which can be separated readily to yield ilmenite and magnetite concentrates. The ilmenitehaematite deposits usually contain these minerals in intimate intergrowths, and hemo-ilmenite concentrates can be produced from these ores. Miscellaneous deposits there are a number of deposits around the world (USA, Canada, Brazil, Chile, etc.) with a variety of ore types, some of which have been extensively studied. Such deposits include (a) deposits of ilmenite disseminated in schist, (b) complex deposits of apatiteilmenite (Canada) and (c) deposits of rutile, anastase and brookite in a pegmatic phase of alkaline rocks (USA, Chile). The major occurrence of anatase and ilmenite, found in weathered carbonatite bodies, are found in Brazil. Occurrences of rutile and ilmenite in carbonatitefeldspar rocks are found in Mexico and Chile, and in recent years have been subject to extensive investigations Sand deposits of titanium minerals The most abundant titanium sand deposits are black sands in streams and on beaches of volcanic regions. The principal black minerals are magnetite, titanoferous magnetite and black silicates, chiefly angite and hornblend. It is quite difficult to produce an ilmenite suitable for pigment product from black sand, but other sand deposits that contain rutile, ilmenite and often monazite are found in Australia, USA, India and Africa. These deposits are either alluvial or marine in origin. From a beneficiation point of view, formation of hard rock and sand deposits, and their mineral composition, determines the beneficiation method FLOTATION PROPERTIES OF MAJOR TITANIUM MINERALS Extensive research has been carried out mainly on ilmenite and, to a lesser degree, on flotation of rutile and perovskite. Flotation studies have been performed on titanium minerals from both hard rock and fine-grained sand deposits Flotation properties of ilmenite Extensive research work has been carried out on ilmenite flotation from different ores [13], including hard rock and sand deposits. Because the chemical composition of ilmenite is unstable, flotation processing characteristics of ilmenite varies from one ore type to another. Figure 25.1 shows the flotation of ilmenite from different ore types at different ph levels using 200 g/t of oleic acid.

4 Flotation of Titanium Minerals 100 Ore type TiO 2 recovery (%) Flotation ph Figure 25.1 Effect of ph on ilmenite flotation from different ore types using oleic acid as collector. The data from Figure 25.1 indicate that ilmenite can be recovered at a wide ph range. There is, however, a difference in the floatability of ilmenite from different ore types. Ilmenite can be successfully floated using fatty acid tall oil collectors at alkaline ph or with sodium alkyl sulphate (C 16 H 33 OSO 3 Na) at acidic ph. Figure 25.2 shows the effect of ph on ilmenite flotation from a sand deposit using alkyl sulphate collector. Acid pretreatment of the ore before flotation had a positive effect on ilmenite flotation. Figure 25.3 shows the effect of different acids used in the pretreatment on ilmenite recovery in the rougher concentrate. The best metallurgical results were achieved using sulphuric acid in the pretreatment stage. Another collector examined for flotation of ilmenite was dodecylammonium chloride. Using this collector, ilmenite readily floated at a ph region between 3.5 and 6.5. The type of gangue depressant and modifier used during ilmenite flotation depends on the type of gangue present in the ore. Sodium silicate is commonly used as a gangue depressant. In a recent study [4], it was demonstrated that the effectiveness of silicates as depressants improved significantly with the use of acidified silicate. Figure 25.4 shows the effect of acidified silicate on the ilmenite graderecovery relationship. Acidified silicate gave significantly better concentrate grades, compared to that obtained using silicate alone. It has been found that the use of Pb(NO 3 ) 2 as an ilmenite activator improved ilmenite floatability and selectivity towards gangue minerals. Experimental work was conducted on

5 25.4 Flotation Properties of Major Titanium Minerals Fluorite 80 Recovery (%) Ilmenite 20 Sphene Flotation ph Figure 25.2 Effect of ph on ilmenite flotation from mineral sands using alkyl sulphate as collector. 100 TiO 2 recovery (%) H 2 SO 4 HCl HNO Acid addition (g/t) Figure 25.3 Effect of type and level of acid in the acid pretreatment stage on titanium rougher flotation.

6 Flotation of Titanium Minerals Acidified Na 2 SiO 3 addition 400 g/t TiO 2 recovery (%) g/t 0 g/t TiO 2 concentrate grade (%) Figure 25.4 Effect of acidified silicate additions on the ilmenite graderecovery relationship. Table 25.2 Results of ilmenite activation flotation using Pb(NO 3 ) 2 Product Pb(NO 3 ) 2 (g/t) Weight (%) % TiO 2 Assay % TiO 2 Distribution Concentrate Middling 1 Middling 2 Middling 3 Tailings Feed Concentrate Middling 1 Middling 2 Middling 3 Tailings Feed both beach sand and hard rock ilmenite. Table 25.2 compares batch test results obtained with and without the addition of Pb(NO 3 ) 2. Significant improvement in ilmenite recovery was realized when using small additions of Pb(NO 3 ) 2. The concentrate grade was similar in both experiments.

7 25.4 Flotation Properties of Major Titanium Minerals Flotation properties of rutile Flotation processing characteristics of rutile from hard rock ore and sand deposits are very much dependent on two major factors: (a) mineral composition of the ore and (b) impurities present in the rutile. Although it has been pointed out by some researchers that rutile can be floated using oleic acid, sodium oleate or other fatty acids in neutral ph, this is not the case when the ore contains calcite, feldspars and olivine. Most recently, a study of rutile ore from Chile containing feldspar indicated that rutile cannot be recovered using fatty acid as collector. Table 25.3 shows the effect of different collectors on rutile from an ore that contains calcite, feldspar and silicate as the major gangue minerals. The results indicated that modified sulphosuccinamate and a mixture of phosphate esters and sulphosuccinamate gave good results. However, using fatty acid did not effectively float the rutile. The sulphosuccinamate collector was extremely effective in flotation of rutile, as well as ilmenite and zircon from a fine sand deposit. Laboratory testing conducted on Wimmera heavy mineral sand from Australia indicated that the use of sulphosuccinamate achieved a high titanium recovery in the bulk cleaner concentrate. Table 25.4 shows the results obtained on the Wimmera heavy mineral sand. The sand was scrubbed and deslimed before flotation. Between 90% and 95% TiO 2 was recovered using a 60 g/t addition of succinamate collector. Research has also been conducted in which steryl phosphonic acid (SPA) was examined in place of benzyl arsonic acid (BAA), which was used in an operating plant in China [5]. In this study, several collectors were examined, including sodium laurate, sodium dodecyl sulphate, amino acids, diphosphonic acid (SPA). It was discovered that SPA was the most effective and that aliphatic alcohol (i.e. octanol) was required to maintain the effectiveness of SPA. The use of emulsifier in the mixture was required to provide a suitable emulsion of the composite collector. A composite collector blended with a 1:1 ratio of SPA and octanol was found to be an effective collector for flotation of hard rock rutile ores. Table 25.3 Effect of different collectors on rutile flotation from the Cerro Blanco rutile ore from Chile Collector Addition Feed Rougher concentrate Rougher tailing (g/t) (% TiO 2) %TiO 2 %TiO 2 %TiO 2 %TiO 2 Assay Recovery Assay Recovery Oleic acid Tall oil fatty acid Sodium oleate Succinamate Phosphoric acid mixture

8 Flotation of Titanium Minerals Table 25.4 Effect of succinamate collector on titanium rutile flotation using Wimmera heavy mineral sand from Australia Sand type Product Weight (%) Assays (%) % Distribution TiO 2 ZrO 2 TiO 2 ZrO 2 East pit sand South pit sand Bulk cleaner concentrate Bulk rougher concentrate Bulk rougher tail Head (calc) Bulk cleaner concentrate Bulk rougher concentrate Bulk rougher tail Head (calc) < Flotation properties of perovskite A large deposit of perovskite was found recently in the USA (Powderhorn). Perovskite deposits are also known to be found in Russia (Cola Pennisula). There is little information available on research into flotation of perovskite conducted on ores from some Russian deposits [6]. These ores are relatively complex and contain a variety of gangue minerals including pyroxene, amphibole, olivine, nepheline, biotite and calcite. Flotation of perovskite was achieved with pretreatment of the flotation feed with H 2 SO 4 followed by perovskite flotation with oleaic acid at a ph of The use of sodium silicate as a depressant resulted in an increase in concentrate grade, up to 47% TiO 2. Pilot plant tests on a perovskite ore showed that a perovskite concentrate assaying 48.5% TiO 2 can be readily produced using distilled tall oil as collector. Most recently, development testwork was performed on a large perovskite deposit (Powderhorn) located in the USA. An effective beneficiation process was developed, where a concentrate assaying >50% TiO 2 was achieved in the pilot plant confirmation tests [7]. During this development testwork, a number of different collectors were examined at different ph values. Figure 25.5 shows the effect of the different collectors on perovsikte flotation. The most effective collector was phosphoric acid ester modified with either fatty alcohol sulphate or petroleum sulphonate PRACTICES IN BENEFICIATION OF TITANIUM ORES A large portion of titanium minerals (ilmenite, rutile) are produced from heavy mineral sands using physical preconcentration methods including gravity, magnetic and electrostatic separation. Over the past 30 years, advances have been made using flotation, where ilmenite, rutile and perovskite can be effectively recovered from both heavy mineral sands and hard rock ores using flotation methods.

9 25.5 Practices in Beneficiation of Titanium Ores TiO 2 recovery (%) Phosporic acid ester modified with fatty alcohol sulphate Phosphoric acid ester, unmodified Tall oil fatty acid Sodium oleate Flotation ph Figure 25.5 Effect of different collectors on perovskite flotation at different phs (Powderhorn ore from the USA) Practices in beneficiation of ilmenite ores using flotation Titania A/S, Norway This is one of the oldest operations in the world. The mine and plant are located in the southern part of Norway. This ore can be classified as an ilmenorutile, with ilmenite and magnetite as the valuable minerals. The gangue consists mainly of feldspar, hypersthene and biotite. The secondary minerals present in this ore include pyrite, olivine and pyrrhotite. There are two major ore bodies: the Stogargen (old deposit) and Zellnes deposits. These two deposits are quite different in mineral composition. Numerous studies have been carried out on these two ore types to provide support for the operating plant. Over a period of years, the Titania A/S flowsheet has changed as the ore in the plant changed. The flowsheet that is currently being used is shown in Figure This flowsheet utilizes a two-stage flotation method, where in stage 1, pyrite and apatite are recovered, followed by ilmenite flotation in stage 2. Before sulphide flotation, magnetite was removed using a low-intensity magnetic separation method. The reagent scheme used at the Titania A/S plant is shown in Table The major problem associated with beneficiation of this ore was the fact that the apatite tended to float with the ilmenite concentrate. Two options were examined to control apatite flotation: (a) apatite flotation in the pyrite circuit using small amounts of tall oil, and (b) use of NaF to

10 Flotation of Titanium Minerals Feed Grinding Magnetic Nonmagnetics separation Magnetics to magnetics plant Conditioning Pyrite flotation Conditioning P 2 O 5 flotation Pyrite cleaner P 2 O 5 cleaner Pyrite concentrate P 2 O 5 concentrate Desliming Slimes Conditioning TiO 2 rougher TiO 2 scavenger TiO2 1 st cleaner TiO 2 1 st cleaner scavenger TiO 2 2 nd cleaner TiO 2 3 rd cleaner TiO 2 cleaner concentrate Tailings Figure 25.6 Titania A/S generalized plant flowsheet.

11 25.5 Practices in Beneficiation of Titanium Ores 185 Table 25.5 Titania A/S reagent scheme Reagent Reagent additions (g/t) ph Pyrite-apatite Ilmenite Pyrite Ilmenite Depressants and modifiers Sodium carbonate NaF Nafaril emulsifier Fuel oil Collectors Tall oil (refined) Ethyl xanthate 50 depress the apatite during the ilmenite cleaning operation. Both methods were capable of lowering the apatite content of the ilmenite concentrate, with an appreciable loss of ilmenite. In the early 1980s, Nobel (a reagent manufacturing company) developed selective apatite collectors (Lilaflot series) based on modified fatty acids, which were capable of removing apatite without any loss of ilmenite. The ph in the ilmenite circuit was controlled with the use of sulphuric acid. In 1980, the tall oil used in the pyrite circuit was replaced with Lilaflot 100 (modified fatty acid). The metallurgical results obtained in the plant are variable with respect to ilmenite recovery. The concentrate grade is usually maintained constant at about 44% TiO 2, while ilmenite recovery ranges from 66% to 75% TiO 2. Otanmaki, Finland The Otanmaki ore contains about 35% magnetite, 28% ilmenite, 1% pyrite and 35% silicate minerals. This ore contains an appreciable amount of fine ilmenite, most of which reports to the slime fraction. About 1012% of the total ilmenite in this ore reports to the slime fraction. Initially, this plant was operated using a standard flowsheet involving three-stage desliming followed by pyrite flotation and ilmenite flotation from the pyrite tailing. Research work was carried out [8] to examine possible recovery of ilmenite using an agglomerated flotation method. The major objective of this study was to float the ilmenite without desliming using an agglomeration process. The major variables examined in this study included conditioning time and type of emulsifying agent. The conditioning time and conditioning power were critical in achieving high ilmenite recoveries. Figure 25.7 shows the effect of conditioning time and conditioning power on ilmenite recovery. Good results were achieved using attrition conditioning at reduced time. With the standard long conditioning time, up to 50 min was required to achieve a recovery of 90% TiO 2.

12 Flotation of Titanium Minerals 100 Conditioner 90 Attritioning TiO 2 recovery (%) Standard Conditioning time (min) Figure 25.7 Effect of conditioning time and power on ilmenite recovery using agglomeration flotation. From the various emulsifiers examined, an anionic emulsifier from the sulphonic acid group of polyglycol-ether of fatty alcohol and alkylphenol-polyglycol esters was used. The best results were achieved with the use of alkylphenol-polyglycol ester (Berol EMU27). The Otanamki ilmenite flowsheet without desliming is shown in Figure This flowsheet has replaced the flowsheet that incorporated the desliming stage in late The reagent scheme used in this plant for agglomeration flotation included 800 g/t tall oil, 1500 g/t fuel oil, 800 g/t tall oil emulsion, 60 g/t Etoxol P19 and 50 g/t xanthate. The ph in the rougher flotation was maintained at 4.5 and the cleaners at 3.5 using H 2 SO 4. A concentrate grade of 44% TiO 2 at a recovery of 88% was produced using agglomeration flotation, compared to a concentrate grade of 44% TiO 2 with a recovery of 74% without agglomeration flotation Beneficiation of apatiteilmenite ores (Sept Iles Mine, Canada) In the late 1990s, extensive research work was carried out on a number of complex ilmenite ores resulting in the development of new technology capable of producing good-quality ilmenite concentrate with a respectable recovery. This section describes the treatment process that was developed for apatiteilmenite ores using new technology [9].

13 25.5 Practices in Beneficiation of Titanium Ores 187 Feed Grinding Magnetic separation Non magnetics Magnetics Pyrite flotation Conditioning 1 Conditioning 2 Conditioning 3 TiO 2 rougher TiO 2 scavenger TiO 2 1 st cleaner TiO 2 2 nd cleaner TiO 2 3 rd cleaner TiO 2 4 th cleaner TiO 2 cleaner concentrate Final tail Figure 25.8 Generalized Otanamki plant flowsheet. The Sept Iles ore contains economic quantities of apatite and ilmenite. About 6% of the titanium in this ore is represented by titanomagnetite. The major gangue minerals include feldspar, olivine, dolomite and aluminosilicate. This ore assayed 7.2% TiO 2 and 4.25% P 2 O 5. During research development testing, a fairly large number of collectors were examined, mainly phosphoric acid esters that were modified with different secondary collectors. Figure 25.9 shows the effect of different collectors and phs on ilmenite flotation.

14 Flotation of Titanium Minerals TiO 2 recovery (%) SM14 phosphoric acid ester modified with alkyl sulphate SM15 phosphoric acid ester modified with petroleum sulphonate Mixture of phosphoric acid ester with succinamate Collector R260H R276F R Flotation ph Figure 25.9 Effect of different collectors and phs on ilmenite flotation. Based on data shown in Figure 25.9, ilmenite recovery was a function of both ph and collector modifications. The optimum flotation ph was between 3 and 5. Phosphoric acid esters modified with petroleum sulphonate gave the highest recovery. Tall oils were also tested, but without success, as they were unselective towards olivine. A number of different depressants were also examined, mainly organic and inorganic mixtures, some of which had a pronounced effect on both apatite and ilmenite. The flowsheet used for apatite flotation is shown in Figure The ore was ground to a K 80 of 80 μm, followed by magnetic separation. The non-magnetic fraction was subjected to apatite flotation and upgrading. The ilmenite flowsheet is shown in Figure and was specifically designed to reduce recirculation loads of gangue during cleaning operations. The reagent scheme that was developed for beneficiation of this apatiteilmenite ore is shown in Table The following is a description and function of the individual reagents: Caustic tapioca starch was used for depression of ilmenite and iron oxides during flotation of apatite. Soda ash was used for ph control. Depressant A4 was used for depression of silicates, feldspar and olivine. This mixture consists of acidified silicate and ferrous sulphate (FeSO 4 ) in a 90:10 ratio. This mixture is also highly effective in depressing silicates and olivine. Fatty acid (FA2) was used as an apatite collector in saponified form.

15 25.5 Practices in Beneficiation of Titanium Ores 189 Ore Combined non-magnetics Grinding Magnetic separation Regrinding Magnetics Conditioning 1 Conditioning 2 P 2 O 5 rougher P 2 O 5 scavenger Mgnetic separation Cleaner magnetics Regrinding P 2 O 5 1 st cleaner P 2 O 5 1 st cleaner scavenger P 2 O 5 2 nd Cleaner Desliming Sand P 2 O 5 3 rd cleaner Slime P 2 O 5 4 th cleaner P 2 O 5 cleaner concentrate P 2 O 5 final tail Figure Grinding, magnetic separation and apatite flotation flowsheet. Oxalic acid was used for gangue depression during ilmenite flotation as a primary depressant. Depressant SHQ was used as a tertiary depressant, mainly for magnesium-bearing minerals in the final TiO 2 -cleaning stages. It consisted of a mixture of Calgon glass, sodium silicate and Quebracho in a ratio of 40:40:20. Acidified silica/aq55d mixture was used as primary depressant during ilmenite flotation. This mixture consisted of 70% acidified silicate a 30% AQ55D reagent. NaOH was used in the alkaline conditioning pulp pretreatment stage. HCl was used in the acid pretreatment stage as ph modifier in the ilmenite flotation and cleaning stages. Collector mixture D consisted of SM15/R845/R825 in a ratio of 45:45:10 and was used as the primary ilmenite collector.

16 Flotation of Titanium Minerals Feed NaOH conditioning Desliming Acid conditioning Desliming Slime 1 Slime 2 Conditioning 1 Conditioning 2 Ti rougher Ti scavenger Ti 1 st cleaner Ti 1 st cleaner scavenger Ti 2 nd cleaner Total tail Ti 3 rd cleaner Ti 4 th cleaner Ti 5 th cleaner Acid conditioning Desliming Slime 3 Ti 6 th cleaner Ti scalper Ti cleaner concentrate Figure Ilmenite flotation flowsheet. The metallurgical results obtained in a continuous pilot plant operation are presented in Table Excellent apatite results were achieved. An ilmenite concentrate was produced suitable for pigment production.

17 25.5 Practices in Beneficiation of Titanium Ores 191 Table 25.6 Reagent scheme developed for beneficiation of apatiteilmenite ore from the Sept Iles mine Reagent Additions (g/t) P 2 O 5 circuit TiO 2 circuit Total Depressants and modifiers Caustic starch Na 2 CO 3 A4 HCl Oxalic acid Acidified silicate/aq55d NaOH SHQ Collectors and frothers FA2 (saponified) SM15/CA540/R825 MIBC Table 25.7 Pilot plant results Product Weight (%) Assays (%) % Distribution TiO 2 TiO 2 P 2 O 5 Fe 2 O 3 SiO 2 MgO Overall Circ P 2 O 5 Fe 2 O 3 SiO 2 P 2 O 5 cleaner concentrate TiO 2 cleaner concentrate TiO 2 combined tail Head (calc) Ilmenite production from heavy mineral sands and chromium problems The ilmenite production from heavy mineral sands exclusively utilizes a physical separation method using magnetic separation, gravity concentration and electrostatic separation. Flotation is practiced mainly for beneficiation of fine mineral sands containing rutile, ilmenite and zircon. The ilmenite that is produced in a number of operations in Western Australia, India and the USA is high in chromium, which makes the ilmenite unusable. This section discusses a new process that was developed for chromium removal from ilmenite concentrates.

18 Flotation of Titanium Minerals A sample used for testing was an ilmenite concentrate from Western Australia that assayed 0.4% Cr 2 O 3 and about 58% TiO 2, where the chromium in the concentrate was in the form of chromspinel with small quantities of chromite. Another sample used in the development testwork was ilmenite concentrate that only contained chromite. It was a known fact that flotation properties of both chromite and ilmenite are similar and they float equally well using either tall oil or amine collectors. Development testwork involved the examination of different ilmenite depressants and different chromium collectors. Depressants examined in this study included corn starch, NaF and H 2 SiF 6 at a low ph. Good ilmenite depression was achieved using H 2 SiF 6, while the chromium was not affected. Similar results were achieved using NaF. A number of different chromium collectors were also examined, including R84, which is a sulphonate collector as the primary collector, and amine acetate as the secondary collector was found to be effective for chromium flotation. The most critical parameter for selective chromium flotation was the ph. Selective chromium flotation occurs at a very narrow ph region, Figure shows the effect of ph on chromium flotation. The final flowsheet that was developed for chromium removal is shown in Figure The concentrate was scrubbed with alkaline followed by desliming. The deslimed concentrate was subjected to chromium flotation followed by a single cleaning stage. The reagent scheme that was developed for chromium flotation is shown in Table The ph control was achieved using nitric acid. The presence of nitric acid appeared to improve selectivity. The results obtained with HCl and H 2 SO 4 were not as good as those achieved using HNO 3. Final metallurgical results obtained using selective chromium flotation, from an ilmenite concentrate, are shown in Table An average of 80% Cr 2 O 3 was removed from the ilmenite concentrate. The chromium assays of the ilmenite concentrate were reduced from 0.4% to 0.09% Cr 2 O Cr 2 O 3 recovery to its concentrate (%) Flotation ph Figure Effect of ph on chromium flotation from an ilmenite concentrate.

19 25.5 Practices in Beneficiation of Titanium Ores 193 Ilmenite Concentrate Scrubbing Desliming Slimes Conditioning 1 Conditioning 2 Cr 2 O 3 rougher Conditioning Cr 2 O 3 scavenger Conditioning Cr 2 O 3 cleaner Cr 2 O 3 product TiO 2 product Figure Chromium flotation flowsheet. Table 25.8 Chromium removal reagent scheme Reagent Additions (g/t) ph Scrubbing Cr 2 O 3 Flotation Ro Cl Depressants and NaOH HNO 3 H 2 SiF 6 Corn starch modifiers Collectors R840 Armac C

20 Flotation of Titanium Minerals Table 25.9 Chromium flotation metallurgical results Test no. A B Product Weight (%) Assays (%) Cr 2 O 3 TiO 2 Cr 2 O 3 concentrate Cr 2 O 3 tailing Head (calc) Cr 2 O 3 concentrate Cr 2 O 3 tailing Head (calc) % Distribution Cr 2 O 3 TiO PRACTICES IN RUTILE FLOTATION In the past, most of the rutile was produced from heavy mineral sands using physical concentration, involving gravity, magnetic separation and electrostatic concentration. The physical preconcentration method cannot be applied to a fine heavy mineral sand or hard ore. In some cases, heavy mineral sand contains zircon, tantalum, niobium and other heavy minerals, where in most cases a flotation method is used. Over the past 20 years, a new technology was developed that can produce a high-grade rutile concentrate from hard rock ores. In addition, different methods have been developed by which rutile from bulk gravity concentrates containing zircon and other heavy minerals can be successfully separated. This section discusses methods of beneficiation of rutile from hard rock and fine heavy mineral sands Development and operation of zircon flotation at sierra rutile limited Mining and mineral processing operations at the Sierra Leone (Africa) mine are based on a series of relatively large, highly complex ore bodies characterized by a wide variation in mineral composition and mineral size distributions. Over the years, Sierra Leone Limited has produced rutile concentrate and ilmenite concentrate using gravity, magnetic and electrostatic separation from the +250-mesh fraction. There is a large portion of rutile and zircon contained in the 250-mesh fraction, which cannot be separated by physical concentration and the fine material is stockpiled over the years. In the early 1990s, development testwork was conducted by Hazen Research (USA) to develop a process for treatment of fine rutile/zircon sand using a flotation method [11]. After the development testwork was completed, the separation process was introduced into the Seirra Leone plant. Description of the zircon flotation process The fine 250-mesh product was preconcentrated using gravity (tabling) followed by zircon flotation and magnetic separation to produce rutile and ilmenite concentrate. The process flowsheet with points of reagent additions is presented in Figure Using

21 25.6 Practices in Rutile Flotation min/stage 30 min total 35% solids 100 mesh table concentrate 0.18 kg/t starch ~0.05 kg/t H 2 SO kg/t ARMAC "C" concentrate (quartz) 0.64 kg/t starch ~0.57 kg/t H 2 SO kg/t NaF Conditioning 1 30 sec Conditioning 2 30 sec, 3 stages ph 7.5 SiO 2 rougher Tailing Conditioning 1 30 sec 0.61 kg/t Armac "C" 1 min Tailing Zircon rougher retention Conditioning 30 sec/stage 1 min/stage Zircon rougher 5 stages (continued) Tailing 0.05 kg/t Armac "C" Concentrate 1 min/stage 3 min total Zircon 1 st cleaner Dry and induced roll Magnetics Non- magnetics Zircon concentrate Tailing Ilmenite Rutile Figure Plant flowsheet with reagent additions for production of zircon, rutile and ilmenite from the Sierra Leone fines. this flowsheet, the following concentrates were produced: (a) zircon concentrate that assayed 58% ZrO 2,0.8%TiO 2 at a recovery of 85%; (b) rutile concentrate that assayed 0.8% ZrO 2, 95.2% TiO 2 at a recovery of 40% and (c) ilmenite concentrate assaying 0.65% ZrO 2, 56% TiO 2 at a recovery of 30%. Rutile/ilmenite-zircon bulk flotation and separation Several large deposits of fine mineral sands containing rutile, ilmenite and zircon exist in Australia (Wimmera mine) and in the Soviet Union. The rutile, ilmenite and zircon cannot be preconcentrated. In most cases, flotation was used which involved bulk flotation followed by titaniumzircon separation. Over the years, several effective processes have been developed for bulk flotation followed by titaniumzirconium separation. The type of

22 Flotation of Titanium Minerals method used is dependent on the type and mineralogy of the fine sand. The following section describes three major methods developed for bulk Ta/Zr flotation and separation. Method 1 This method has been successfully used in the Soviet Union. The flowsheet with the type and levels of reagent additions is shown in Figure Sand Scrubbing Desliming Slimes 100 g/t oleic acid 2000 g/t oxidized fuel oil H 2 SO 4 to ph 6.5 Bulk flotation Silica Thickening Effluent 5000 g/t Na 2 SiO 3 Conditioning heating 400 g/t CuSO 4 Conditioning heating, 60 C ZrO 2 flotation Thickening Tabling Tails Rutile concentrate ZrO 2 concentrate Tailings Figure Flowsheet with reagent additions for beneficiation of fine mineral sands (Kola Peninsula, Soviet Union).

23 25.6 Practices in Rutile Flotation 197 The bulk flotation can be accomplished with the addition of small doses of oleic acid plus oxidized emulsion of fuel oil. The fuel oil is treated with 10% solution of NaOH at a temperature of 6080 C for 1 h. The following method was used for rutilezircon separation; the concentrate was thickened, followed by heat conditioning to 60 C. After the heat treatment, the zircon was floated without the addition of collector. The zirconium tailing is the rutile concentrate. The zircon concentrate was thickened, followed by gravity cleaning. In some cases, the heat-treated pulp is washed before zircon flotation. The following metallurgical results were obtained: Rutile product 92.5% TiO 2 at 90% recovery Zircon concentrate 0.2% TiO 2, 63% ZrO 2 at 94% ZrO 2 recovery. Method 2 It involves bulk flotation of rutile, ilmenite and zircon followed by selective flotation of rutile and ilmenite and depression of zircon. Figure shows the flowsheet with type of reagent additions used in selective flotation of titanium from zircon. The collector used was a mixture of oleic acid and kerosene in a ratio of 1:1. The mixture was aerated with oxygen during a period of 2 h before using. The advantage of using the oxidized mixture is that it desorbs easily from the mineral surfaces during separation. The metallurgical results obtained using Method 2 are shown in Table Method 3 It involves bulk titanium/zircon flotation using succinamate collector followed by bulk concentrate pretreatment and selective zircon flotation. This method was developed for beneficiation of the Wimmera heavy mineral sand from Australia [12]. The beneficiation flowsheet with type and level of reagents is shown in Figure The sand preparation method had a significant impact on both collector consumption, as well as quality of the bulk concentrate. It was found that the mixture of Na 2 SiO 3 /tall oil addition to the scrubbing stage before desliming improved the slime decoating from the heavy mineral surface resulting in a significant improvement in concentrate grade. In addition, collector consumption was reduced by 50%. The mixture consisted of 70% Na 2 SiO 3 and 30% tall oil fatty acid. The effect of the levels of silicate tall oil additions and conditioning times are presented in Table In these tests, the mixture of Na 2 SiO 3 /tall oil was added to the scrubber before desliming. Collector used in the bulk circuit was sulphosuccinate. In the rutile circuit, phosphoric acid ester was used. Silica was rejected in a bulk talking. The overall metallurgical results obtained in the continuous operation are shown in Table Rutile flotation from hard rock ore Over the past 10 years, new technology has been developed that allows flotation of rutile from complex hard rock ores. This new technology has been confirmed in continuous pilot plant operation. During the development testwork, ores from Mexico, Chile and Australia were studied. Guadalajara (Mexico) rutile ilmenite ore The Guadalajara titanium-bearing ore comes from a hard rock deposit consisting principally rutile and ilmenite. Over 85% of the rutile and ilmenite are liberated at relatively

24 Flotation of Titanium Minerals Sand Scrubbing Desliming Slimes 400 g/t Na 2 SiF g/t collector H 2 SO 4 to ph 6.2 Conditioning TiO 2 /ZrO 2 flotation 1500 g/t Na 2 SiF 6 H 2 SO 4 to ph 4.5 Conditioning TiO 2 flotation 500 g/t oxalic acid H 2 SO 4 to ph 4.5 Conditioning Rutile flotation Rutile Ilmenite ZrO 2 combined concentrate concentrate concentrate tailings Figure depression. Flowsheet and reagent additions used in selective titanium flotation and zircon coarse grind, while the remaining 15% appears in the form of middlings, as complex intergrowths with non-opaque minerals. The major gangue minerals were plagioclase, feldspar, quartz, calcite and some apatite. The removal of apatite before titanium flotation along with calcite dolomite was required since the apatite tends to float with the titanium. The flowsheet (Figure 25.18) shows the final flowsheet developed for the beneficiation of the Guadalajara ore. This flowsheet consists of two flotation circuits: (a) gangue prefloat circuit, where the apatite and calcite are recovered, and (b) titanium flotation circuit, where

25 25.6 Practices in Rutile Flotation 199 Table Results obtained using sequential rutile, ilmenite, and zircon flotation from bulk concentrate Product Assays (%) % Distribution TiO 2 ZrO 2 TiO 2 ZrO 2 Rutile concentrate Ilmenite concentrate Zircon concentrate Tailings Head (calc) a high-grade rutile and ilmenite concentrate were produced. The rutile concentrate produced was free of apatite and silicate. The reagent scheme developed for beneficiation of the Guadalajara ore is shown in Table During gangue flotation, caustic corn starch was used to depress the titanium. Gangue flotation was accomplished using emulsified tall oil DO2. Over 87% of the apatite was recovered in a gangue concentrate. The gangue tailings were treated with acid followed by titanium flotation using oxalic acid + H 2 SiF 6 as the gangue depressants. A new titanium collector composed of a mixture of fatty acid ester and sulphosuccinamate modified surfactant was used (PL519). This collector provides a high rate of titanium flotation and is selective towards the gangue minerals. Metallurgical results obtained in a continuous operation are shown in Table A high-grade rutile and ilmenite concentrate were produced with respectable recoveries White Mountain titanium (Chile) A large hard rock rutile deposit was discovered in central Chile. This ore is relatively complex with variable head grade of rutile ranging from 2% to 4% TiO 2. The liberation of rutile occurs at about 100 mesh nominal size. The major gangue minerals present in this ore include feldspars, calcite and some silicates. Development work conducted over the past 3 years has identified a treatment process that will produce a high-grade rutile concentrate. The initial flowsheet is similar to that used for the Guadalajara ore. However, using this flowsheet, only a portion of the calcite was recovered and an appreciable amount of the rutile was lost in the gangue concentrate. An alternative, effective treatment process has been developed that produces excellent results. The flowsheet developed for beneficiation of the White Mountain titanium ore consist of two distinct circuits: (a) grinding, sizing and gravity preconcentration of the ore, and (b) rutile flotation from the gravity concentrate. This flowsheet includes gravity preconcentrate and flotation as shown in Figure It should be noted that gravity preconcentration on the sized ground ore improved gravity performance. The flotation flowsheet included a triple open-circuit flotation and

26 Flotation of Titanium Minerals Sand 200 g/t Na 2 SiO 3 / D40LR Scrubbing Desliming Slimes 100 g/t Na 2 SiO 3 / D40LR Scrubbing Desliming Slimes 50 g/t F2875 H 2 SO 4 to ph g/t Bulk rougher flotation Bulk scavenger flotation H 2 SO 4 to ph 3.5 Bulk cleaner flotation 500 g/t NaOH Conditioning Effluent Dewatering Desliming Slimes 600 g/t starch 300 g/t NaF 800 g/t H 2 SiF g/t oxalic acid Conditioning 400 g/t amine H 2 SO 4 to ph 3.0 Conditioning 30 g/t SM15 TiO 2 rougher 20 g/t SM15 TiO 2 scavenger 100 g/t starch H 2SO 4 to ph 3.0 ZrO 2 rougher 100 g/t oxalic acid TiO 2 cleaner ZrO 2 cleaner Magnetic separation ZrO 2 concentrate Magnetics Non-magnetics Ilmenite Rutile Tailings Figure Flowsheet and reagent scheme for beneficiation of the Wimmera heavy mineral sand.

27 Table Effect of level of silicate tall oil mixture and conditioning time on bulk Ti/Zr bulk flotation Test no. Na 2 SiO 3 /D40LR (g/t) Conditioning time (min) Collector (g/t) Bulk rougher concentrate Weight (%) Assays (%) % Distribution TiO 2 ZrO 2 TiO 2 ZrO Practices in Rutile Flotation 201

28 Flotation of Titanium Minerals Table Results obtained on the Wimmera fine mineral sand (WIM150 ore) Product Weight (%) Assays (%) % Distribution TiO 2 ZrO 2 TiO 2 ZrO 2 Zircon concentrate Rutile concentrate Ilmenite concentrate Combined tails Feed (calc) Ground deslimed ore Conditioning 1 Acid conditioning Conditioning 2 Desliming Slimes Gangue rougher Gangue scavenger TiO 2 rougher Gangue cleaner TiO 2 1 st cleaner TiO 2 1 st cleaner scavenger Gangue 1 st cleaner Gangue 2 nd cleaner TiO 2 2 nd cleaner Gangue cleaner concentrate TiO 2 3 rd cleaner TiO 2 4 th cleaner TiO 2 cleaner concentrate High intensity magnetic separation Magnetics Non-magnetics TiO 2 Ilmenite Rutile tailing Figure Flowsheet developed for beneficiation of the Guadalajara (Mexico) hard rock rutile ilmenite ore.

29 25.6 Practices in Rutile Flotation 203 Table Reagent scheme Reagent Additions (g/t) Gangue prefloat Acid treatment Titanium circuit Depressants and modifiers Caustic corn starch 900 Sulphuric acid (H 2 SO 4 ) 2000 Hydrofluorosilicic acid (H 2 SiF 6 ) 450 Oxalic acid 400 Sodium silicate (Na 2 SiO 3 ) acid 600 Collectors and frothers Fatty acid DO2 180 Collector PL MIBC 20 Table Overall results obtained in continuous operation Product Weight (%) Assays (%) % Distribution TiO 2 SiO 2 Fe 2 O 3 P 2 O 5 TiO 2 SiO 2 Fe 2 O 3 P 2 O 5 TiO 2 rutile concentrate (12 AN M) TiO 2 ilmenite concentrate (12 AMAG) TiO 2 combined concentrate Gangue D concentrate TiO 2 combined tails Primary slimes Acid slimes Feed cleaning. This flowsheet was designed to provide a more effective rejection of gangue during rutile cleaning. The reagent scheme developed for the White Mountain titanium ore is shown in Table Gangue depressants H 2 SiF 6, oxalic acid and DAX1 were used. Depressant DAX2 is a mixture of low-molecular-weight acrylic acids designed specifically to depress calcite. A highly selective collector, KBX2, is a mixture of succinamate (Cytec s R845) and phosphoric acid ester (Clariant s SM15) modified with alkyl sulphate. The metallurgical results from the gravity preconcentration continuous pilot plant are shown in Table

30 Flotation of Titanium Minerals Feed Slimes RM O/S 35m 35m BM To flotation 200m +65m C C M M T 65m C M C M T Final gravity tails 100m RM Figure White mountain titanium flowsheet. Over 56% of the feed was rejected in the gravity tailing with about 9% loss of the total titanium in the ore. The overall results, including gravity and flotation, are summarized in Table A premium-grade rutile concentrate assaying 97.3% TiO 2 was produced at an average recovery of 96% TiO 2. This was a premium-grade rutile concentrate.

31 25.6 Practices in Rutile Flotation 205 Table Reagent scheme for the White Mountain titanium rutile ore Reagent Additions (g/t) Depressants and modifiers Hydrofluorosilicic acid (H 2 SiF 6 ) Oxalic acid DAX1 Collectors KBX1 Fuel oil TiO 2 rougher TiO 2 cleaner Table Results from the gravity preconcentration tests Test number Product Weight (%) Assays (%) % Distribution TiO 2 SiO 2 Fe 2 O 3 CaO TiO 2 SiO 2 Fe 2 O 3 CaO T1 Combined 200 m and +200 m table concentrate +middlings Combined 200 m and +200 m table tails Slime Head (calc) T2 Combined 200 m and +200 m table concentrate +middlings Combined 200 m and +200 m table tails Slime Head (calc)

32 Table Overall results obtained in a continuous pilot plant operation Test number Product Weight (%) Assays (%) %Distribution TiO 2 SiO 2 Fe 2 O 3 CaO TiO 2 SiO 2 Fe 2 O 3 CaO F-3 TiO 2 concentrate non-magnetic Combined overall tails + slime Head (calc) F-4 TiO 2 concentrate non-magnetic Combined overall tails + slime Head (calc) Flotation of Titanium Minerals

33 References 207 REFERENCES 1. Polkin, S.I., Concentration of Ores from Sand Deposits and Hard Rock, Izdatelstro Nedra 1987, pp Fan, X., and Rawson, N.A., The Effect of pb(no 3 ) 2 on Ilmenite Flotation, Minerals Engineering, Vol. 13, No. 2, pp , Bulatovic, S., and Wyslouzil, D.M., Process Development for Treatment of Complex Perovskite, Ilmenite and Rutile Ore, Minerals Engineering, Vol. 12, No. 12, pp , Bulatovic, S., Process Development for Beneficiation of Apatite, Ilmenite Ore from Quebec, Canada, Report of Investigation, p. 320, July Liu, Q.I., and Peng, Y., Development of Composite Collector for the Flotation of Rutile, Minerals Engineering, Vol. 12, No. 12, pp , Belash, F.N., and Gamilow, M.A., Perovskite Flotation Using Acid Pretreatment, Bulletin CIN Cvetnie Metaly, No. 21, Bulatovic, S., Pilot Plant test on Perovskite Recovery from Powderhorn USA ore, Report of Investigation, Runolima, U., How Otammaki Floats Ilmenite from Fnland Titaniferous Magnetite, Mining World San Francisco, pp. 4955, Bulatovic, S., Process Development for beneficiation of Complex ApatiteIlmenite Ore from Quebec, Canada, Laboratory and Pilot Plant Studies, Report of Investigation, Bulatovic, S., Chromium Removal from the Ilmenite Concentrate by Flotation from RZM Western Australia, Report of Investigation, Davis, J.P., Wonday, S., and Keilj, A.K., Developoment and Operation fo Zircon Flotation at Sierra Rutile, 10th Industrial Mineral International Congress, San Francisco, pp. 6571, Bulatovic, S., Laboratory and pilot plant development testwork on recovery of titanium and zircon from Wimmera heavy mineral sand, Report of Investigation, p. 330, 1992.