Ilmenite flotation

Extensive research work has been carried out on ilmenite flotation from different ores [1-3], 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. 

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 (Ci6H330S03Na) 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. 

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 grade-recovery relationship. 

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 25.6. This flowsheet utilizes a two-stage flotation method, where in stage 1, pyrite and apatite are recovered, followed by ilmenite flotation in stage 2. 

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. 

Figure 25.9 Effect of different collectors and pHs on ilmenite flotation.

Oxalic acid was used for gangue depression during ilmenite flotation as a primary depressant. 

Acidified silica/AQ55D mixture was used as primary depressant during ilmenite flotation. This mixture consisted of 70% acidified silicate a 30% AQ55D reagent. 

HCl was used in the acid pretreatment stage as pH modifier in the ilmenite flotation and cleaning stages. 

The electrostatic separation method is the exclusive choice in some specific situations, for example in the cases of rutile and ilmenite deposits. These deposits generally contain minerals of similar specific gravities and similar surface properties so that processes such as flotation are unsuitable for concentration. The major application of electrostatic separation is in the processing of beach sands and alluvial deposits containing titanium minerals. Almost all the beach sand plants in the world use electrostatic separation to separate rutile and ilmenite from zircon and monazite. In this context the flowsheet given later (see Figure 2.35 A) may be referred to. Electrostatic separation is also used with regard to a number of other minerals. Some reported commercial separations include those of cassiterite from scheelite, wolframite from quartz, cassiterite from columbite, feldspar from quartz and mica, and diamond from heavy associated minerals. Electrostatic separation is also used in industrial waste recovery. 

A large portion of monazite production comes from mineral sand deposits. In the beneficiation of monazite from mineral sand deposits that contain garnet, ilmenite, shell and silicates, the physical concentration and combination of physical preconcentration-flotation is used. Several reagent schemes using flotation were developed throughout various studies [8-10] and some have been confirmed in continuous pilot plants. 

India has very large deposits of monazite on the coastal shores of Kerala and Chennai. A typical mineral composition of this type of deposit is 60% ilmenite, 1.2% rutile, 5% zircon, 6.4% garnet, 4% silinanite, 16% quartz, 2.5-5% monazite and 1-7% shell. Research work involved different anionic collectors and pH during monazite flotation, along with the level of sodium silicate used as depressant. 

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. 

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 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% Ti02 was recovered using a 60g/t addition of succina-mate collector. 

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, mtile and perovskite can be effectively recovered from both heavy mineral sands and hard rock ores using flotation methods. 

Practices in beneficiation of ilmenite ores using flotation... 

The reagent scheme used at the Titania A/S plant is shown in Table 25.5. 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... 

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. 

Caustic tapioca starch was used for depression of ilmenite and iron oxides during flotation of apatite. 

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. 

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 com starch, NaF and H2SiF6 at a low pH. Good ilmenite depression was achieved using H2SiF6, while the chromium was not affected. Similar results were achieved using NaF. 

Final metallurgical results obtained using selective chromium flotation, from an ilmenite concentrate, are shown in Table 25.9. 

Figure 25.12 Effect of pH on chromium flotation from an ilmenite concentrate.

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 25.14. Using... 

Rutile/ilmenite-zircon bulk flotation and separation... 

Several large deposits of fine mineral sands containing mtile, ilmenite and zircon exist in Australia (Wimmera mine) and in the Soviet Union. The mtile, ilmenite and zircon cannot be preconcentrated. In most cases, flotation was used which involved bulk flotation followed by titanium-zircon separation. Over the years, several effective processes have been developed for bulk flotation followed by titanium-zirconium separation. The type of... 

Method 2- It involves bulk flotation of rutile, ilmenite and zircon followed by selective flotation of mtile and ilmenite and depression of zircon. Figure 25.16 shows the flowsheet with type of reagent additions used in selective flotation of titanium from zircon. 

Results obtained using sequential rutile, ilmenite, and zircon flotation from bulk concentrate... 

Bulatovic, S., Chromium Removal from the Ilmenite Concentrate by Flotation from RZM Western Australia, Report of Investigation, 1993. 

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