HK1159597A - Processes for producing titanium dioxide - Google Patents

Description

Process for producing titanium dioxide

Technical Field

The present invention relates to a process for the preparation of titanium dioxide from ilmenite.

Background

Titanium dioxide is used as a white pigment in paints, plastics, paper and specialty applications. Ilmenite is a naturally occurring ore comprising the chemical formula FeTiO₃Titanium and iron.

Is currently used for preparing TiO₂Two main methods of pigment are: sulfate processes, such as those described in Haddeland, G.E. and Morikawa, S., "Titanium Dioxide Pigment", SRI International Report #117 ", and chloride processes, such as Battle, T.P., Nguygen, D. and Reeves, J.W., The Paul E.Queneau International Symposium on active metallic ofCopper, Nickel and Cobalt, volume I: methods described in Fundamental accessories, Reddy, R.G. and Weizenbach, R.N. editions, The Minerals, Metals and Materials Society, 1993, page 925-943. Dumon et al (Dumon, J.C., Bull. Inst. Geol. Bassin Aquitaine, 1975, 17, 95-100 and Dumon, J.C., and Vigneeaux, M., Phys. chem. Earth 1977, 11, 331-337) describe processes for extracting ilmenite using organic and inorganic acids.

The invention provides a method for preparing TiO₂The novel processes of (a) enable the use of lean ores that are less energy intensive, require less capital investment, and have less environmental impact than current conventional production processes.

Brief Description of Drawings

FIG. 1 is a process flow diagram for producing titanium dioxide according to a process of one embodiment of the present invention.

Summary of The Invention

One aspect of the invention is a method comprising:

a) digesting titaniferous iron ore with aqueous trimethyl ammonium hydrogen oxalate to form leachate and an iron-rich precipitate;

b) separating the leachate from the iron-rich precipitate;

c) hydrolyzing the leachate using trimethylamine to form titanyl hydroxide and an oxalate rich solution;

d) separating the titanyl hydroxide from the oxalate rich solution;

e) washing the titanyl hydroxide with a material selected from the group consisting of water, aqueous trimethylammonium oxalate and aqueous trimethylamine to form a low oxalate titanyl hydroxide; and

f) crystallizing titanium dioxide from the low oxalate titanyl hydroxide.

Another aspect of the invention is a method comprising:

a) digesting the ilmenite ore with aqueous trimethyl ammonium hydrogen oxalate to form a first leachate and an iron-rich precipitate;

b) separating the first leachate from the iron-rich precipitate;

c) optionally, adding a reducing agent to the first leachate to form a second iron-rich precipitate and a second leachate, and separating the second iron-rich precipitate from the second leachate;

d) hydrothermally crystallizing the first or second leachate in an autoclave for 1 hour to 24 hours to form titanium dioxide and a hydrothermally treated solution; and

e) separating the titanium dioxide from the hydrothermally treated solution.

Yet another aspect of the invention is a method comprising:

a) digesting titaniferous iron ore with aqueous trimethyl ammonium hydrogen oxalate to form leachate and an iron-rich precipitate;

b) separating the leachate from the iron-rich precipitate;

c) adding a reducing agent to the leachate to form an iron-rich precipitate and a reduced leachate;

d) separating the second iron-rich precipitate from the reduced leachate;

e) hydrolyzing the reduced leachate with aqueous trimethylamine to form titanyl hydroxide; and

f) the titanyl hydroxide is hydrothermally crystallized to form titanium dioxide and a solution of bis (trimethyl) ammonium oxalate.

Detailed Description

In the process disclosed herein, ilmenite is digested by exposure to aqueous trimethylammonium hydrogen oxalate. Trimethylammonium is defined as the attachment of three methyl groups and one hydrogen to one nitrogen atom. The process comprises digesting ilmenite using trimethyl ammonium hydrogen oxalate. This results in an iron-rich precipitate and a titanium-rich solution that can be separated. Various other processes can produce titanium dioxide. In some embodiments, oxalate in the process stream may be recovered as trimethyl ammonium hydrogen oxalate for additional digestion. A schematic of one embodiment of the present invention is shown in figure 1.

In the first step of the process the ore is digested. The digestion process produces an iron-rich solid and a titanium-rich solution. The titanium-rich solution is hydrolyzed and the resulting solution is crystallized to titanium dioxide. The iron-rich solids can be hydrolyzed to form iron oxide. The aqueous ammonium di (trimethyl) oxalate may be collected from several steps. The aqueous ammonium di (trimethyl) oxalate may be heated to produce aqueous ammonium trimethyl oxalate and aqueous trimethylamine, which may be recycled to a previous process.

As used herein, for the purposes of the embodiments of the present invention, the term "ilmenite ore" refers to ilmenite with a titania content ranging from 35 to 75% by weight. The chemical composition of natural ilmenite can vary widely. It is generally considered to have the formula FeTiO₃Ferrous titanate. The proportion of iron may be higher than the theoretical composition due to the mixing of hematite or magnetite. Excess titanium may be present due to the presence of rutile. The process of the present invention is applicable to ilmenite having a titanium dioxide content at the lower end of the ilmenite range. Preferably 35 to 60% by weight, most preferably 45 to 55% by weight.

The particle size of the ilmenite is preferably in the range of less than 1 to 300 microns for rapid dissolution, with 95% or more of the particles being less than about 100 microns. Smaller sized ore particles (< about 140 mesh) may be used in the process and may provide advantages over known sulfate and chloride processes. These smaller particles are not preferred for use in the earlier sulfate or chloride processes. The concentration of ammonium trimethyl oxalate must be 5 to 10 moles.

The digestion reaction can be carried out in one of three different chemical environments, non-oxidizing, oxidizing or reducing. All digestion reaction environments contain aqueous trimethyl ammonium hydrogen oxalate. The ratio of trimethylammonium to hydrogen in the aqueous trimethylammonium hydrogen oxalate can vary. The digestion reaction may be carried out in aqueous trimethylammonium oxalate having a ratio of trimethylammonium to hydrogen up to and including 1.5 to 1.

For the non-oxidative digestion reaction, ilmenite is contacted with aqueous trimethylammonium hydrogen oxalate under an inert gas atmosphere, such as nitrogen. Other suitable inert gases include helium and argon. The digestion reaction in an inert gas environment can inhibit the oxidation of iron ions in the solution. For the digestion reaction carried out in an inert atmosphere, the molar ratio of ammonium trimethyl oxalate to ilmenite is from 4: 1 to 8: 1 (based on the ratio of hydrogen in ammonium trimethyl oxalate to ilmenite). Ilmenite and aqueous trimethyl ammonium hydrogen oxalate form a mixture. The mixture is maintained under reflux conditions at a temperature of about 100 ℃ to 140 ℃ until a substantial portion of the ore, for example at least about 70%, preferably at least about 90%, and in some embodiments substantially all of the ore, is dissolved. Under these preferred conditions, dissolution of ilmenite in aqueous trimethylammonium hydrogen oxalate proceeds at a rate such that approximately about 70% to 90% of the titanium in the ore dissolves in about 8 hours. Although dissolution may take more than 8 hours, this may not be desirable or may be disadvantageous in terms of cost. Iron (II) in solution with FeC₂O₄·2H₂The form of O precipitates, leaving a titanium-rich solution. In solutions rich in titanium, for the ideal FeTiO₃In other words, the molar ratio of Ti/(Fe + Ti) in the solution (for example in a ratio of 50.1: 100 or higher) is greater than the molar ratio present in the ilmenite used. It is preferred to minimize the amount of iron in the leachate. The precipitation rich in iron means that the molar ratio of Ti/(Fe + Ti) in the solution is smaller than that of the ferrotitanium usedPrecipitation of the molar ratio of Ti/(Fe + Ti) in the ore. The precipitate containing FeC₂O₄·2H₂And O. The solids produced by the digestion step may also comprise unreacted ilmenite and its attendant impurities (e.g., quartz, zircon, rutile, anatase, other ilmenite, monazite, etc.). In addition, other metal oxalate (such as magnesium oxalate and calcium oxalate) which is extremely insoluble can be contained.

In addition to trimethyl ammonium hydrogen oxalate, the non-oxidative digestion reaction may be carried out in the presence of a reducing agent. The reducing agent can be, for example, Fe (0), Zn (0), Ti (III) or Al (0), preferably metallic iron. Treatment with a reducing agent advantageously converts essentially all of the Fe (III) present, which is highly soluble in aqueous trimethylammonium hydrogen oxalate, to Fe (II) as FeC₂O₄·2H₂O) to further increase the Ti/(Ti + Fe) ratio of the solution. The solution may then be diluted to a Ti content of about 1% by weight, as determined by ICP (inductively coupled plasma spectroscopy) or equivalent chemical analysis methods. The metal reducing agent may be added in the form of powder, flakes, wire or other known forms. Other metal oxalates from impurities in titaniferous ores, e.g. MnC₂O₄·2H₂O, may be co-precipitated with ferrous oxalate.

In oxidative digestion reactions, the digestion is carried out in an oxidizing gas (e.g., air). For dissolution in air or other oxidizing gas, the molar ratio of ammonium trimethyl oxalate to ore is from 5: 1 to 10: 1 (based on the ratio of hydrogen in ammonium trimethyl oxalate to ilmenite). In such digestion reactions, the fe (ii) species are oxidized to fe (iii). Ferric ions generated after digestion in air are more soluble in solution than ferrous ions and require additional steps to reduce and separate to form a titanium-rich solution for further processing. Oxidative digestion reactions involve contacting a titaniferous iron ore with aqueous trimethyl ammonium hydrogen oxalate in an oxidizing gas to form an iron and titanium rich solution and solids containing insoluble materials. Air may be added as an overpressure in the autoclave, for example using a sparger. The insoluble components in the ore may include rutile, zircon and/or quartz. After separation of the insoluble material in the presence of air, the resulting solution is exposed to a reducing agent, such as metallic zinc, under an inert gas to reduce ferric ions to ferrous ions and form an iron-rich precipitate.

In a reductive digestion reaction, the digestion reaction is carried out in the presence of a reducing agent such as iron, zinc, magnesium or aluminium metal particles, which is added at the beginning of the reaction. In the reductive digestion reaction, substantially all of the ferrous ions formed form an iron-rich precipitate that can be separated from the titanium-rich solution.

Whether the digestion reaction is carried out in a single step or in multiple steps, and whether the digestion reaction is oxidative, non-oxidative or reductive, the products of the digestion reaction are a titanium-rich solution and an iron-rich precipitate. The titanium-rich solution is separated from the iron-rich precipitate by conventional means such as filtration and centrifugation. Sufficient ammonium trimethyloxalate may be added to obtain a saturated solution at the hydrolysis temperature (between 25 ℃ and 90 ℃ C.; preferably 75 to 90 ℃ C.).

After digestion, two approaches can be taken for processing. The first route is to hydrothermally treat the titanium rich solution in an autoclave at a temperature of 200 ℃ to 374 ℃ and autogenous pressure for 1h to 24 h. This treatment forms the desired titanium dioxide and a residual solution from which the titanium dioxide can be separated by conventional means, such as filtration or centrifugation.

Hydrothermal treatment of the titanium-rich solution may result in the decomposition of the oxalate anion. If oxalate recovery is desired to reduce process costs, alternative routes may be employed. In an alternative approach, the titanium-rich solution may be hydrolyzed with a base, preferably aqueous trimethylamine solution. The base, in the form of a gas or aqueous solution, is added to the titanium-rich solution at a temperature of from about 25 ℃ to about 90 ℃, preferably from 75 ℃ to 90 ℃, in a sufficient amount to precipitate as much of the titanium component as possible while precipitating as little of the iron component as possible from the titanium-rich solution. Generally by pHAnd (5) monitoring. For example, if the hydrolysis is carried out at room temperature (about 25 ℃), the pH is preferably no greater than about 7.5. Higher pH can lead to unpredictable precipitation of iron species, which can require extensive washing and bleaching with acid to remove the precipitate. The hydrolysate is a mixture comprising "titanyl hydroxide" solids with high oxalate content and residual solution rich in oxalate. The chemical formula of "titanyl hydroxide" is not precisely known, in part because the degree of hydration is variable. It is believed that the "titanium oxyhydroxide" (titanic acid) is TiO (OH)₂、TiO(OH)₂·H₂O, or TiO (OH)₂·nH₂O (where n > 1) or mixtures thereof [ see j. barksdale, "Titanium: its Occurence, Chemistry and Technology ", 2 nd edition, Ronald Press; new York (1966). The mixture is allowed to stir for 1 hour or more and then separated, preferably by thermal filtration through a filter medium having a pore size of about 4-5.5 μm. Preferably, a filtration rate of greater than about 12mL/min is employed. The titanyl hydroxide solids are then washed with a solution (comprising water, aqueous trimethylammonium oxalate and/or aqueous trimethylamine) to displace all of the ingested leachate and reduce the concentration of undesirable metals such as Fe. While preferred amounts of processing ingredients are shown, one skilled in the art will recognize that the concentrations may vary and that the method will work with a variety of concentrations of ingredients used in the method.

At this point in the process, there are again two available routes. In the first approach, the titanyl hydroxide solids mixed with residual solution are hydrothermally treated to form a nano-titania and di (trimethyl) ammonium oxalate solution. The hydrothermal treatment is carried out at a temperature of 250 ℃ or less for 1 to 24 hours. The solution of di (trimethyl) ammonium oxalate may be retained for recovery in the form of trimethyl ammonium hydrogen oxalate which will be used in the earlier stages of the process for additional ore digestion. Any of the digestion processes disclosed herein above may be used to prepare TiO therewith₂The above-mentioned methods are used in combination. In a second alternative, high oxalate content titanyl hydroxide solids are reslurried with water to form a slurry containing sufficient aqueous trimethylamine such thatThe pH is raised to about 9. The slurry was then heated and additional aqueous trimethylamine added to maintain the pH at about 9. In this step, any oxalate that remains associated with the titanium species is removed to form titanyl hydroxide having a low oxalate content in the slurry. The slurry is then filtered and the low oxalate content titanyl hydroxide solids are washed with water to remove any residual oxalate.

Titanium dioxide is known to exist in at least three crystalline mineral forms: anatase type, rutile type, and brookite type. The rutile type crystal is a tetragonal crystal system (P42/mnm,) (ii) a The anatase type crystals are tetragonal (I41/amd,the brookite-type crystal is an orthorhombic crystal system (Pcab,). Crystallization of titanium dioxide from low oxalate content titanyl hydroxide solids can be accomplished by one of four crystallization processes: low temperature hydrothermal (150 ℃ to 250 ℃), high temperature hydrothermal (250 ℃ to 374 ℃), normal calcination (700 ℃ to 1100 ℃), or flux calcination. The crystallization process canOptionally including the addition of crystallization aids such as rutile seeds, mineralizers, and rutile crystal directors (e.g., Sn compounds). Higher temperature approaches, including hydrothermal and calcination, can provide the rutile with the appropriate particle size to give the product the opacity required for most applications. Titanium dioxide products in the particle size range of 100 to 600 nanometers are suitable for use as pigments. Titanium dioxide having a particle size of less than 100 nanometers is referred to as nanoscale.

For conventional calcination, the low oxalate content titanyl hydroxide solids are heated at a temperature of about 800 ℃ to 1000 ℃ for at least one hour. The solid may be heated in air or an inert atmosphere. The conversion of low oxalate content titanyl hydroxide solids to the crystalline anatase and rutile forms can be affected by process factors including, for example, temperature, hold time, temperature time profile, amount of impurities, and additives that promote anatase, rutile, or brookite formation or stabilization. The same or other factors can also affect the morphology of the primary and secondary titanium dioxide particles, such as the particle size, shape, aggregation and agglomeration of the titanium dioxide product.

The morphology of rutile produced from titanyl hydroxide solids derived from low oxalate levels can be altered by the use of additives such as fluxes. Sodium chloride is an example of a fluxing agent. The addition of NaCl can alter the shape and size of the primary and secondary rutile particles. This is called "flux calcination". In flux calcination, the titanium precipitate is heated to about 800 ℃ to 1000 ℃ in the presence of at least 1% by weight flux, such as NaCl, and held for at least 1 hour. Examples of other fluxes are KCl and LiCl.

During calcination, the addition of NaCl can produce a product containing larger primary particles of more distinct shape.

In addition to acting as a particle size and shape control agent, NaCl may also function as a structure directing agent (rutile promoter). For example, titanium precipitates from leachate at 800 ℃ in the absence of NaCl, with and without the addition of additional particle morphology modifiers (e.g., K and P), produce sharp, irregularly shaped precipitatesTitanium ore type particles. However, by adding small amounts of NaCl from about 1 to 5% by weight (the percentages being based on TiO obtainable from precipitation)₂Weight of) to produce a clearly discernible rutile particle product at 800 c. Thus, at 800 ℃, sodium chloride can be used as a rutile promoter, a particle morphology control agent, and a particle agglomeration control agent with titanium precipitates derived from oxalate. Other agents such as KCl and LiCl may also be used as rutile promoters, particle morphology control agents, and particle agglomeration control agents with titanium precipitates derived from oxalate at 800 ℃.

With the currently commercialized TiO₂Compared to the calcination temperature (about 1000+ ° c) typically used in the production of (a), Low Temperature Hydrothermal Crystallization (LTHC) involves the conversion of an amorphous "titanyl hydroxide" intermediate to TiO in the presence of water under relatively mild temperature conditions (from 150 ℃ to 250 ℃)₂The transformation of (3). The reaction temperature in the LTHC process is in the range of as low as 150 ℃ up to 250 ℃, the reaction pressure is close to the corresponding water vapor pressure, and the reaction time is less than 24 hours. Changes in conditions within this range, control of the acid concentration in the reaction mixture, and addition of phase-directed mineralizers can all be used to selectively control the resulting TiO₂Particle size, crystal structure and morphology. For example, rutile TiO with pigment particle size (100nm-300nm)₂Can be prepared at 220-250 deg.C with addition of rutile type guiding mineralizer (such as ZnCl)₂、ZnO、MgCl₂Or NaCl). Nano-grade rutile TiO₂Can be made under similar conditions, but at temperatures as low as 150 ℃. At a temperature as low as 150 ℃ and with the addition of a directing mineralizer of anatase type (e.g. KH)₂PO₄、Al₂(SO₄)₃、ZnSO₄And Na₂SO₄) Can be operated under conditions to produce anatase type TiO₂. Brookite type TiO₂Can be prepared at a temperature above 150 deg.C, optionally with the addition of a brookite-type directing mineralizer (e.g., AlCl)₃·6H₂O、α-Al₂O₃And Al (OH)₃)。

When in the temperature range of 250 ℃ to 374 DEG CIn the high-temperature hydrothermal crystallization in the enclosure, TiO is hydrothermally crystallized in the presence of a strong acid and a plurality of metal chloride mineralizers₂Crystallization of the particles. Amorphous hydrous titanium oxide precipitate (sometimes expressed as TiO (OH))₂·nH₂O, n is about 32) is added to water to make a slurry, typically in the range of 33 to 50% by weight. The slurry may be acidified using a strong mineral acid to obtain a pH value typically in the range of 1 to 2. Alternatively, a metal chloride salt can be added in an amount corresponding to the amorphous TiO (OH)₂·nH₂In the range of 0.5 to 20% by weight of O. For example, rutile TiO with pigment particle size (100nm-300nm)₂Can be at 250-374 deg.C and added with rutile type guiding mineralizer (such as ZnCl)₂、ZnO、MgCl₂Or NaCl). The slurry was placed in a gold reaction tube and crimped closed, but not completely sealed, to allow pressure equilibration. The gold tube containing the contents was then placed in an autoclave. The temperature may be in the range of 250 ℃ to 374 ℃ and the pressure is autogenous, typically in the range of 40 to 170 atm. The duration of the high-temperature hydrothermal treatment is generally from 1 to 72 hours.

Iron oxide can be produced from the iron-rich precipitate produced in the above-described process. The iron-rich precipitate is reacted with a base, preferably aqueous trimethylamine, in the presence of oxygen to form iron oxide/hydroxide and a solution of di (trimethyl) ammonium oxalate resulting from the iron-rich precipitate. The iron oxide is then separated from the solution. Iron oxide can be used as a pigment or in the production of metallic iron. Alternatively, the iron (II) -rich precipitate may be oxidised to soluble iron (III) species by treatment in an oxalate solution, followed by hydrolysis of the iron (III) species using aqueous trimethylamine to give an iron oxide/hydroxide precipitate and a solution of bis (trimethyl) ammonium oxalate. Alternatively, the iron-rich precipitate may be calcined or hydrothermally treated to form a plurality of iron oxide states. These routes are described in U.S. Schwertmann and R.M. Cornell, "Iron Oxides in the Laboratory", 2003 2 nd edition, Wiley VCH, Weinheim.

Trimethyl ammonium hydrogen oxalate may be recovered and recycled from the di (trimethyl) ammonium oxalate produced in various steps and embodiments of the process. The recovered trimethyl ammonium hydrogen oxalate may be used in the digestion of further ilmenite. Aqueous bis (trimethyl) ammonium oxalate derives from the processing of iron-rich and titanium-rich solutions. The aqueous ammonium bis (trimethyl) oxalate may be combined or processed separately. The solution of ammonium di (trimethyl) oxalate is heated to remove trimethylamine and water from the aqueous trimethyl ammonium hydrogen oxalate. The ability to recycle the oxalate-containing reagent and aqueous trimethylamine reduces the operating costs of the process.

Examples

Example 1

In a 3L round bottom flask equipped with a mechanical stirrer and condenser, 415.7g H were combined under a nitrogen blanket₂C₂O₄·2H₂O (Aldrich Cat No. 247537) and 1005.4g deionized water. A distillation arm was connected to the top of the condenser. A condenser and receiver were attached to the side arm. The receiver was filled with approximately 19g of deionized water and the pH was frequently checked during the experiment to determine if any trimethylamine escaped from the flask during the reaction. Once the temperature reaches about 50 ℃, the oxalic acid is rapidly dissolved. The mixture was stirred at 60 ℃ overnight. To the mixture was added 388.9g of aqueous trimethylamine (50%, Acros). The contents of the flask were refluxed at which point 195g of ilmenite (Iluka Resources LTD, Capel, Australia) was added. The initial pH was about 3. Samples of leachate were taken at 6, 24, 48 and 120h and analyzed for chemical composition by inductively coupled plasma spectroscopy. The results are given in table 1.

TABLE 1

Time (h) Fe (ppm) Ti (ppm) Fe/Ti (molar ratio)

6 8684 16312 0.456

24 10473 22044 0.407

48 11745 25144 0.400

120 14018 29751 0.404

Example 2

1241.2g of the green leachate solution from example 1 (pH 1.59) were placed in a 2L resin kettle equipped with a stirring motor and condenser. The solution was heated to 83 ℃ under a nitrogen atmosphere. A total of 17.6g of iron powder was added. After reduction (indicated by the formation of a blue precipitate upon mixing with ammonium hydroxide), the solution was allowed to cool and allowed to stir overnight. The final pH was 4.27. The mixture was filtered using a 0.45 μ nylon disposable filter funnel covered with nitrogen. By this method, 1120.2g of a wheat root-Shashi colored solution was collected. ICP analysis showed that the molar Fe/Ti ratio of 0.0448 contained 1670ppm Fe and 32100ppm Ti compared to 0.404 of the starting leachate.

Claims (15)

1. A method, the method comprising:

a) digesting titaniferous iron ore with aqueous trimethyl ammonium hydrogen oxalate to form leachate and an iron-rich precipitate;

b) separating the leachate from the iron-rich precipitate;

c) hydrolyzing the leachate with trimethylamine or aqueous trimethylamine to form titanyl hydroxide and an oxalate rich solution;

d) separating the titanyl hydroxide from the oxalate rich solution;

e) washing the titanyl hydroxide with a material selected from the group consisting of water, trimethylamine, and aqueous trimethylamine to form a low oxalate titanyl hydroxide; and

f) crystallizing titanium dioxide from the low oxalate titanyl hydroxide.

2. The process of claim 1, further comprising adding a reducing agent to said leachate to form a reduced leachate and a second iron precipitate, and separating said second iron precipitate from said reduced leachate.

3. A method, the method comprising:

a) digesting the ilmenite ore with aqueous trimethyl ammonium hydrogen oxalate to form a first leachate and an iron-rich precipitate;

b) separating the first leachate from the iron-rich precipitate;

c) optionally, adding a reducing agent to the first leachate to form a second iron-rich precipitate and a second leachate, and separating the second iron-rich precipitate from the second leachate;

d) hydrothermally crystallizing the first or second leachate in an autoclave for 1 hour to 24 hours to form titanium dioxide and a hydrothermally treated solution; and

e) separating the titanium dioxide from the hydrothermally treated solution.

4. A method, the method comprising:

a) digesting titaniferous iron ore with aqueous trimethyl ammonium hydrogen oxalate to form leachate and an iron-rich precipitate;

b) separating the leachate from the iron-rich precipitate; adding a reducing agent to the leachate to form a second iron-rich precipitate and a reduced leachate;

c) separating the second iron-rich precipitate from the reduced leachate;

d) hydrolyzing the reduced leachate with aqueous trimethylamine to form titanyl hydroxide; and

e) the titanyl hydroxide is hydrothermally crystallized to form titanium dioxide and a solution of bis (trimethyl) ammonium oxalate.

5. The method of claim 1, further comprising:

oxidizing the iron-rich precipitate in an acidic trimethyl ammonium hydrogen oxalate solution to form a trimethyl ammonium iron (III) oxalate solution;

optionally, separating unreacted ore from the trimethylammoniumperature (III) solution;

adding a base to the trimethyl ammonium iron (III) oxalate solution to form an iron-rich hydroxide precipitate and a di (trimethyl) ammonium oxalate solution;

separating the iron-rich hydroxide precipitate from the di (trimethyl) ammonium oxalate solution; and

optionally, calcining the iron-rich hydroxide precipitate.

6. The method of claim 3, further comprising:

oxidizing the iron-rich precipitate in an acidic trimethylammonium oxalate solution to form a trimethylammonium iron (III) oxalate solution;

optionally, separating unreacted ore from the trimethylammoniumperature (III) solution;

adding a base to the trimethyl ammonium iron (III) oxalate solution to form an iron-rich hydroxide precipitate and a di (trimethyl) ammonium oxalate solution;

separating the iron-rich hydroxide precipitate from the di (trimethyl) ammonium oxalate solution; and

optionally, calcining the iron-rich hydroxide precipitate.

7. The method of claim 4, further comprising:

oxidizing the iron-rich precipitate in an acidic trimethylammonium oxalate solution to form a trimethylammonium iron (III) oxalate solution;

optionally, separating unreacted ore from the trimethylammoniumperature (III) solution;

adding a base to the trimethyl ammonium iron (III) oxalate solution to form an iron-rich hydroxide precipitate and a di (trimethyl) ammonium oxalate solution;

separating the iron-rich hydroxide precipitate from the di (trimethyl) ammonium oxalate solution; and

optionally, calcining the iron-rich hydroxide precipitate.

8. The method of claim 1, further comprising:

adding an alkali to the iron-rich precipitate to form an iron-rich hydroxide precipitate and an alkaline solution;

separating the iron-rich hydroxide precipitate from the alkaline solution; and optionally calcining the iron-rich hydroxide precipitate.

9. The method of claim 3, further comprising:

adding an alkali to the iron-rich precipitate to form an iron-rich hydroxide precipitate and an alkaline solution;

separating the iron-rich hydroxide precipitate from the alkaline solution; and

optionally, calcining the iron-rich hydroxide precipitate.

10. The method of claim 4, further comprising:

adding an alkali to the iron-rich precipitate to form an iron-rich hydroxide precipitate and an alkaline solution;

separating the iron-rich hydroxide precipitate from the alkaline solution; and

optionally, calcining the iron-rich hydroxide precipitate.

11. The process of claim 4, further comprising refluxing the solution of bis (trimethyl) ammonium oxalate to obtain an aqueous trimethylamine distillate and an acidic solution of trimethyl ammonium hydrogen oxalate.

12. The method of claim 1, further comprising calcining the iron-rich precipitate.

13. The method of claim 3, further comprising calcining the iron-rich precipitate.

14. The method of claim 4, further comprising calcining the iron-rich precipitate.

15. The process of claim 1, further comprising refluxing the solution of bis (trimethyl) ammonium oxalate to obtain an aqueous trimethylamine distillate and an acidic solution of trimethyl ammonium hydrogen oxalate.