IL171363A

IL171363A - Process for the production of titanium products

Info

Publication number: IL171363A
Application number: IL17136305A
Authority: IL
Inventors: Asher Vitner
Original assignee: Asher Vitner; Joma Int As
Priority date: 2005-10-11
Filing date: 2005-10-11
Publication date: 2011-12-29
Also published as: CN101384512A; ZA200803180B; CN101384512B; ES2363685T3

Description

171,363/2 363 ,7'π I 453570 τνηχ A PROCESS FOR THE PRODUCTION OF TITANIUM PRODUCTS tJV)tt \? o sitt iipan *p rm It is to be noted that only the subject matter embraced in the scope of the claims appended hereto, whether in the manner defined in the claims or in a manner similar thereto and involving the main features as defined in the claims, is intended to be included in the scope of the present invention, while subject matter described and exemplified to provide background and better understanding of the invention, is not intended for inclusions as part of the present invention.

The present invention relates to a method for the production of titanium oxide. More particularly, the present invention relates to a method for the production of titanium oxide from a low-grade-stream solution of titanium.

Titanium dioxide is widely used as a white pigment with a market of about $7 billion per year.

The industrial production of titanium oxide usually includes a chlorination or sulfonation stage, wherein titanium-ores of high-grade are used. In the chlorination process, HC1 is used to extract titanium from ores and titanium chloride is distilled; thus, a highly purified titanium-dioxide is produced. However, the main disadvantage of this process is the high-cost of the titanium-chloride distillation. In the case of the sulfonation process the main disadvantage is that lower titanium oxide grade is obtained.

Titanium oxide being a white pigment is usually produced from high-grade titanium ores. The product has to meet strict standards of content of impurities, particle size and distribution of particle-size. The particle size of the titanium oxide particles ranges from several nanometers to several hundreds of nanometers. The cost of the raw material for the production of these products is high. Low-grade titanium ores or low grade solution streams obtained from industrial processes are still not used for the production of these products.

The process described in the present disclosure suggests producing titanium oxide from low-grade titanium stream using a purification stage in which a titanium double salt is produced.

A double salt is defined as a crystal that consists of two different cations and/or anions, wherein it is characterized by a significant lower solubility compared to the simple salts of its components, double salts can be produced from a larger number of polyvalent cations. Both titanium, Fe(III) and , together.

Based on said property of the double-salt, several precipitation methods were suggested for the formation of metal salts, however, very few of them mentioned titanium as one of the components constituting the double salt.

Patent BR 20012509 authored by SILVA HELIO JOSE in 2003 separates titanium oxide from the other polyvalent cations present in llmenite or other titanium containing ores. In this proposed process, Fe and Al are separated from the titanium salt prior to the precipitation of Fe(lll) in the form of ammonium double salt. The addition of ammonium sulfate to a solution obtained by leaching llmenite with sulfuric acid, induced the precipitation of the binary salts ( H4)Fe(S04)2l 2H20, (NH4)2TiO(S04)2H20, and (NH4)2Fe(S04)26H20 together.

According to the present invention, it was surprisingly found that titanium double salt can be precipitated from a solution containing a high proportion of polyvalent cation and especially Fe(ll) and Fe(lll) at high yield and high selectivity, to produce a product of a high titanium to polyvalent cations ratio. It was also surprisingly found that the produced double salt can be washed with very low losses of titanium, to provide a product of a grade sufficient for the production of nano particles of titanium oxides.

The present disclosure suggests a highly efficient, low-cost purification, in which low-grade titanium streams are consumed for the production of high-grade titanium dioxide.

DISCLOSURE OF THE INVENTION With this stage of the art in mind, there is now provided, according to the present invention, a method for the industrial purification of a titanium feed stream of purity P1 , by the formation of a titanium-double-salt precipitate of purity P2, and a titanium solution with purity P3, wherein P2>P1 >P3, said method comprising the steps of: . , , , , cation selected from the group consisting of ammonium, cations of alkali metals, protons and a combination thereof, and an anion selected from the group consisting of OH, S04, HS04, and a combination thereof, which formed medium is further characterized by the presence of (a) a double-salt precipitate comprising titanium ion, at least one of said cations and at least one of said anions; and (b) a titanium solution; and wherein the concentration of said anion in said titanium solution is higher than 15 wt % and the ratio between the concentrations of said cation and said anion in said titanium solution is higher than 0.4 and lower than 1.6; and; i. separating at least a portion of said precipitate from said second solution.

Co m ^ The term titanium-double-salt as used in the present specification refers to a crystal that consists of an anion and two different cations wherein one of said cations is titanium. The term basic double salt as used in the present specification refers to a crystal that consists of hydroxyl, another anion and two different cations wherein one of said cations is titanium.

The term purity or P will be defined as the weight ratio between the titanium to total polyvalent metals, wherein the purity is presented in several cases in terms of percentage, for example P1 as used in the present specification refers to the purity of Stream 1.

The term titanium oxide used in the present specification especially in Step (c) will be referred to in the present disclosure as Ti02 and Ti(OH)4 in any combination and in any variation of hydration level.

According to one embodiment said low-grade-stream solution of titanium, which was defined as Stream 1 , is formed by leaching titanium ores using an acid solution. According to another embodiment said Stream 1 comprises an acid selected from the group consisting of acid halides, sulfuric acid, nitric acid or any combination thereof.

According to another embodiment of the present invention, said Stream 1 comprises a waste stream from industrial process and in another embodiment said Stream 1 comprises a waste stream from a titanium production process.

The present disclosure suggests a highly efficient process for the purification of low-grade titanium streams.

In one embodiment, the purity of said stream P1 , is in the range of between about 10% and about 90%. Preferably P1 is lower than 60%. In especially preferred embodiments P1 is lower then 50% and in a most preferred embodiment P1 is lower then 45%.

According to one embodiment, said low-grade-stream solution of titanium includes iron and the molar ratio between the iron and the titanium in said low-grade-stream solution is in a range of between about 0.2:1 and 3:1.

According to Step (a) of the first embodiment, said low-grade-stream of titanium is contacted with a reagent to form a titanium double-salt. According to a preferred embodiment of the invention the second cation of said titanium- double-salt is ammonium and according to another embodiment said cation is selected from the group consisting sodium and potassium.

According to another embodiment, the anion of said titanium double-salt is selected from the group consisting OH, SO4 and HSO4, halides and acid halides.

As mentioned above, the titanium double-salt is preferably formed by contacting said low-grade-stream of titanium with a reagent selected from the group consisting of a salt, a base and an acid or a combination thereof, wherein according to one embodiment of the present invention, when said reagent comprises a combination of an acid and a salt, then the weight ratio between said acid and said salt is greater then 0.1 , preferably greater then 0.5, and most preferred, greater then 1. According to another embodiment of the present invention when said reagent comprises a combination of a base and a salt then the molar ratio between said base and salt is greater then 0.1.

Preferably the formed precipitate is selected from the group consisting of titanium double salts and titanium basic double salts. Especially preferred are embodiments wherein said precipitate contains at least 80% of the titanium that was present in said low-grade-stream solution, and most preferably at least 85%.

The suggested purification method is very efficient, thus, according to a preferred embodiment, the ratio between the purity of the precipitate and the purity of the second solution, P2/P3, is greater than 2, in more preferred embodiments greater than 5, and in especially preferred embodiments this ratio is greater than 10.

Preferably the purity of the said precipitate, P2, is greater than 80%. In especially preferred embodiments the purity is greater than 85%. Even more preferred is a purity, P2, greater than 90% and most preferred is a purity, P2, greater than 95%.

According to a preferred embodiment the mixture of said Streams 1 and 2 comprises sulfate ions wherein the molar ratio between HS04* and S04= is greater than 0.1 . According to another preferred embodiment said molar ratio is greater than 0.2, and according to another preferred embodiment, greater than 0.5.

This precipitation stage is conducted at a moderate temperature. According to a preferred embodiment the temperature is in the range of 5-80°C, according to another embodiment the temperature is in the range of 10-50°C and according to a most preferred embodiment, said temperature is in the range of 20-40°C.

After the step of contacting a low-grade-stream of titanium with a reagent to form the precipitate and a second solution and then separating at least a portion of said precipitate, the next step is processing said precipitate to produce titanium oxide.

According to a preferred embodiment the process of processing said precipitate includes a precipitate washing stage with a third solution to form purified precipitate with a titanium purity of P4 and a wash solution with a titanium purity of P5, wherein P4 > P2 > P5.

According to a preferred embodiment said third solution comprises a cation that is selected from the group consisting of ammonium and alkali metals and a combination thereof and an anion selected from the group consisting of OH, SO4l HSO4, halides and acid halides and a combination thereof.

In a further preferred embodiment said third solution comprises NH4HSO4. According to another preferred embodiment it comprises NH4HSO4 and H2SO4. In yet another preferred embodiment the molar ratio of SO4/HSO4 in said solution is defined to be smaller then 2.

According to yet another preferred embodiment the process of processing said precipitate includes dissolving and re-crystallization stages of said precipitate with a solution to form a purified precipitate with a titanium purity of P6 and a second wash solution with a titanium purity of P7, wherein P6 > P2 > P7.

Preferably said solution for dissolving said precipitate comprises a cation that is selected from the group consisting of ammonium and alkali metals and a combination thereof and an anion selected from the group consisting OH, SO4, HSO4, halides and acid halides and a combination thereof. According to another preferred embodiment said solution comprises water.

In especially preferred embodiments of the present invention, processing said precipitate includes a production stage of titanium oxide, comprising the steps of: i. dissolution of a titanium double-salt in aqueous solution; and ii. inducing a change of the conditions to form a titanium oxide precipitation from said solution, wherein said change is selected from the group consisting of dilution, temperature elevation, increasing pH and a combination thereof.

In yet another preferred embodiment said titanium oxide contains at least 70% of the titanium that was present in said low-grade-stream solution, and more preferably at least 85%.

In addition, according to a first preferred embodiment said titanium oxide is in the form of nano-particles wherein the particles-size is in the range of 5-100 nanometers while according to a second preferred embodiment said nano-particles have a particle size in the range of 100-300 nanometers.

According to a preferred embodiment, said second solution that was defined as Stream 3, is modified by crystallization to form products selected from the group consisting of iron metal, iron oxide and products of other polyvalent cations present in said low-grade-stream solution.

According to another preferred embodiment said iron containing product is selected from the group consisting of a double iron salt, iron oxide and iron hydroxide.

According to a preferred embodiment the anion comprising said double iron salt is selected from the group consisting of monovalent anions, divalent anions, halide anions, sulfate and bisulfate anions and a combination thereof.

According to another preferred embodiment the second cation comprising said double-iron-salt is selected from the group consisting of ammonium, sodium and potassium.

According to a preferred embodiment said second solution that was defined as Stream 3, is modified by a crystallization stage to form products of other polyvalent cations present in said low-grade-stream solution selected from the group consisting of neutral double salts of their cation, basic double salts, metal oxides or metal hydroxides of their cation.

According to another preferred embodiment said crystallization stage is induced by the action selected from the group consisting of addition of a monovalent-cation-salt, addition of a monovalent-cati on-base, increasing temperature, dilution and a combination thereof.

In yet another aspect of the present invention, there is now provided, a method for the production of a titanium oxide from a titanium double-salt solution via precipitation of titanium oxide, comprising the steps of: i. dissolution of a titanium double-salt in aqueous solution; and ii. inducing a change of the conditions to precipitate titanium oxide from said solution, wherein said change is selected from the group consisting of dilution, temperature elevation, increasing pH and a combination thereof.

According to a preferred embodiment the ratio between the total titanium amount in said titanium oxide to that in said titanium double-salt is greater than 0.8 and more preferably greater then 0.95.

According to a preferred embodiment said change of said conditions refers to increasing the temperature to be above 80°C. In especially preferred embodiments said temperature elevation refers to increasing the temperature to be in the range of 80°C to 120°C and most preferred is increasing the temperature to be in the range of 120°C to 250°C.

While the invention will now be described in connection with certain preferred embodiments in the following examples and with reference to the accompanying figures so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended Claims. Thus, the following examples which include preferred embodiments will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of formulation procedures as well as of the principles and conceptual aspects of the invention.

In the drawings: Figures 1-3 present flow diagrams of embodiments of the present invention.

Figure 1 presents a flow diagram of one of the preferred processes according to the embodiments of the present invention. In Stagel titanium ores are leached using an acid solution to form a low-grade-source solution of titanium, wherein the acid is selected from the group is consisting of acid halides, sulfuric acid, nitric acid or any combination thereof. For simplification, the acid in the present figure was chosen to be sulfuric acid. Two streams are exiting the leaching stage: a waste stream that contains un-dissolved solids and a stream defined as the low-grade-stream of titanium, which is entering Stage 2 the precipitation stage.

Alternatively to the low-grade- stream of titanium formed by the leaching stage, in another preferred embodiment of the present invention, a waste stream from a titanium production process, or a waste stream from an iron production process are entering Stage 2 to the precipitation^stage. - ?i In Stage2 (the precipitation stage) said low-grade stream of titanium is contacted with a reagent selected from the group consisting of a salt, a base and an acid and a combination thereof, wherein the cation of the salt and the base is selected from the group consisting of ammonium and alkali metals and a combination thereof and the anion of the acid and of the salt is selected from the group consisting of OH, SO4, HSO4, halides and acid halides and a combination thereof to form a titanium double-salt which precipitates and a second solution.

For simplification, Figure 1 demonstrates the addition of a solution containing (NH4)2S04 to Stage2. In a preferred embodiment this stage is conducted in a temperature-range of 5-80°C, and in another preferred embodiment this stage is conducted in a temperature range of 10-50°C and in yet another preferred embodiment, in the range of 20-40°C.

Two steams are exiting the Precipitation stage: the formed titanium double-salt which precipitates and a second solution. The molar ratio between the HSO4" and the HS04= in these two streams together is greater than 0.1. In another preferred embodiment it is greater than 0.2 and in another preferred embodiment it is greater than 0.5.

In the present figure the second cation in said titanium-double-salt is ammonium, while yet in another preferred embodiment it is sodium, potassium or any alkaliflf^ metal.

This stage is very effective, in a preferred embodiment the said titanium-double-salt comprises at least 80% of the titanium that was presented in said low-grade-source solution, more preferably at least 85%.

In addition, this stage is characterized by the formation of a very pure titanium-double-salt wherein its purity (P2) is greater than 80%, preferably greater than 85%, more preferably greater then 90% and in the most preferred embodiment it is greater then 95%, wherein the ratio P2/P3 is greater than 2, more preferably greater than 5 and most preferably greater than 10.

Two streams are exiting the precipitation stage: the formed titanium double-salt which precipitates and a second solution which is entering Stage 5.

At least a portion of the formed titanium double-salt which precipitates in Stage 2 is separating from said second solution and enters Stage 3 for a washing stage. In this stage the double-salt is washed with a third solution to form a purified precipitate of titanium oxide with titanium purity of P4 and a wash solution with a titanium purity of P5, wherein P4 > P2 > P5.

The third solution comprises the same cation and anion used in the precipitation stage (Stage 2). In a preferred embodiment and as noted in the present Figure this solution contains NH4HS04 and H2S04 wherein in a more specific preferred embodiment the SO4/HSO4 molar ratio in said solution is smaller then 2. Figure 1 shows that said third solution is a recycled stream exiting from Stage 4. In addition this figure shows that said wash solution is exiting the washing stage and a portion of it is recycling back to Stage 2 with the addition of NH4OH and another portion of it is recycling back to the leaching stage, Stage 1 , with the addition of H2SO4.

The titanium double-salt precipitate is then entered into the dissolution and re-precipitation stages (Stage 4) to form purified titanium oxide precipitate with a titanium purity of P6 and a second wash solution with a titanium purity P7, wherein P6 > P2 > P7. In a preferred embodiment the solution in this stage comprises the same cation and anion used in Stage 2. According to another embodiment said solution comprises NH4HS04 and H2S04 which is recycled back to Stage 3. According to another embodiment and as described in Figure 1 , said solution is water.

In a preferred embodiment the re-crystallization stage is induced by a stage consisting the group of dilution, heating, increasing pH or a combination thereof. The titanium oxide product exiting the re-crystallization stage contains at least 70% of the titanium that was presented in said low-grade-source solution, more preferably at least 85%. In another preferred embodiment the titanium oxide is in the form of nano-particles and the particles size is in the range of 5-100 nanometer. In another embodiment the particles size is in the range of 100-300 nanometer.

In a preferred embodiment the said second solution exiting Stage 2 is modified to form products selected from the group consisting of iron metal, iron oxide and products of other polyvalent cation presented in the low-grade- source of titanium. For simplification Figure 1 shows that the product exiting Stage 5 is an iron product.

Figure 2 presents a flow diagram of one of the preferred processes according to the embodiments of the present invention. This figure is very similar to Figure 1 , however, instead of a Washing stage of the titanium-double salt (Stage 3) this figure presents Dissolution and Re-Crystallization steps for the final purification of the titanium-double- salt.

Figures 3 presents a flow diagram of one of the preferred processes according to the present invention for a method of the production of a titanium oxide from titanium double-salt solution via precipitation of titanium oxide, comprising the steps of: dissolution of a titanium double-salt in aqueous solution and inducing a change of the conditions to precipitate titanium oxide from said solution, wherein said change is comprising at least one of the following actions dilution, temperature elevating, increasing pH or combination thereof.

Stage 1 presents dissolution of a titanium double-salt in an aqueous solution. For simplification this stream in this figure was noted to be water.

In Stage 2 titanium oxide is precipitated by inducing a change of the conditions to form the titanium oxide crystals. Two streams are exiting this stage, i.e., the wash solution that contains the anion and the second cation of the titanium double-salt and the product stream of the titanium oxide.

Description of Preferred Embodiments Comperative EXAMPLE 1 Various amount of solutions obtained by leaching llmenite with sulfuric acid, various amounts of ammonia and of (NH4)2S04 were added into flasks. The flasks were shaken at 25°C for 20min or 1.5 hours. A precipitate was formed. The composition of the leachate llmenite solution is presented in Table 1 and that of the in Tables 2 and 3.

Table 1 EXAMPLE 2 Various amount of solutions obtained by leaching llmenite with sulfuric acid, Ammonia and (NH4)2S04 were added into flasks. The flasks were shaken at 25°C for 1 .5 hours. A precipitate was formed. The composition of the precipitate and solution is presented in Table 4.

Example 3 Various amount of solutions obtained by leaching llmenite with sulfuric acid, Ammonia and (NH4)2S04 were added into flasks. The flasks were shaken at 25°C for 1 .5 hours. A precipitate was formed. The composition of the precipitate and solution is presented in Table 5.

Table 5 Example 4 Various amount of solutions obtained by leaching llmenite with sulfuric acid, and (NH4)2S04 were added into flasks. The flasks were shaken at 30°C for 20min. A precipitate was formed. The composition of the initial solution is presented in Table 6 and that of the results in table 7 Table 6 Initial conditions Table 7 Results Example 5.1 Various amount of solutions obtained by leaching llmenite with sulfuric acid, Ammonia and (NH4)2S04 were added into flasks. The flasks were shaken at °C for 1.5 hours. A precipitate was formed. The composition of the precipitate and solution is presented in Table 8 Table 8 Example 5.2 The crystal obtained in Vial No 2 and 20%NH4HSO4 solution were added into a vial. The vial was shaken for 20min at 30°C, The composition of the solid is presented in Table 9 Table 9 Example 5.3 2.0gr double salt obtained in Example 5.2 were dissolved in 10gr water. The solution was heated to 169°C. A precipitate was formed.

The concentration of Ti in the remaining solution was about 0.05% It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

171,363/3 17 What is claimed is:

1. A method for the industrial purification of a titanium feed stream of purity PI, by the formation of a titanium-double-salt precipitate of purity P2, and a titanium solution with purity P3, wherein P2>P1>P3, said method comprising the steps of: i. forming, from said feed, a medium comprising water, titanium ion, a cation selected from the group consisting of ammonium, cations of alkali metals, protons and a combination thereof, and an anion selected from the group consisting of OH, S04, HS04, and a combination thereof, which formed medium is further characterized by the presence of (a) a double- salt precipitate comprising titanium ion, at least one of said cations and at least one of said anions; and (b) a titanium solution; and wherein the concentration of said anion in said titanium solution is higher than 15 wt % and the ratio between the concentrations of said cation and said anion in said titanium solution is higher than 0.4 and lower than 1,6; and; ii. separating at least a portion of said precipitate from said solution.

2. A method according to claim 1, further comprising the step of processing said precipitate to produce titanium oxide.

3. A method according to claim 2, wherein said titanium oxide contains at least 70% of the titanium originally present in said feed stream.

4. A method according to claim 2, wherein said titanium oxide comprises nano-particles in mid size range of 5-100 nanometer.

5. A method according to claim 2, wherein said titanium oxide comprises nano-particles in mid size range of 100-300 nanometer.

6. A method according to claim 2, for the production of a titanium oxide from said titanium double-salt, comprising the steps of: a. dissolution of a titanium double-salt in aqueous solution; and b. inducing precipitation of titanium oxide from said solution by an action selected from the group consisting of dilution, temperature elevation, increasing a pH and a combination thereof..

7. A method according to claim 6, wherein said titanium oxide contains at least 80% of the titanium originally present in said double salt.

8. A method according to claim 6, wherein said temperature elevation involves increasing the temperature to above 80°C.

9. A method according to claim 6, wherein said temperature elevation refers to increasing the temperature to be in the range of 120°C. to 250°C.

10. A method according to claim 2, wherein said titanium oxide contains at least 70% of the titanium that was present in said titanium feed stream solution.

11. A method according to claim 1, further comprising the step of processing said precipitate to produce a titanium product other than titanium oxide.

12. A method according to claim 1, further comprising the step of processing said precipitate to produce titanium metal. 18 171,363/2

13. A method according to claim 1, wherein said titanium feed stream is an aqueous waste solution.

14. A method according to claim 1, wherein said titanium feed stream comprises at least 2 wt % iron cations.

15. A method according to claim 1, wherein said titanium feed is formed by leaching titanium ores with an acid solution.

16. A method according to claim 1, wherein PI is in the range of between about 10% and about 90%.

17. A method according to claim 1, wherein PI is lower than 60%.

18. A method according to claim 1, wherein PI is lower than 50%.

19. A method according to claim 1, wherein the titanium feed stream comprises iron with a Fe/Ti molar ratio of at least 0.25 and wherein said ratio in said titanium double salt precipitate is less than 0.02.

20. A method according to claim 1, where PI is less than 70% and P2 is greater than 95%.

21. A method according to claim 1, wherein said titanium feed stream comprises protons and at least one anion selected from the group consisting of sulfate, bisulfate and a combination thereof.

22. A method according to claim 1, wherein said titanium feed stream comprises a byproduct stream from an industrial process.

23. A method according to claim 1, wherein said titanium feed stream comprises iron and wherein the Fe/Ti molar ratio in said feed stream is in a range between about 0.2:1 and about 3:1.

24. A method according to claim 23, wherein the Fe/Ti molar ratio in said double salt precipitate is smaller than that ratio in said feed stream by a factor of at least 5.

25. A method according to claim 1, wherein said cation in said double-salt is ammonium.

26. A method according to claim 1, wherein the cation in said double-salt is selected from the group consisting of sodium and potassium.

27. A method according to claim 1, wherein the anion in said double-salt is selected from the group consisting of OH, SO4, HSO4 and halides.

28. A. method according to claim 1, wherein said precipitate is selected from the group consisting of titanium double salts and titanium basic double salts. 19 171,363/2

29. A method according to claim 1, wherein said precipitate contains at least 80% of the titanium originally present in said feed stream.

30. A method according to claim 1, wherein the ratio P2/P3 is greater than 2.

31. A method according to claim 1, wherein the ratio P2/P3 is greater than 10.

32. A method according to claim 1, wherein the temperature of said formed medium is in the range between 0-80° C.

33. A method according to claim 1, wherein the temperature of said formed medium is in the range between 10-50° C.

34. A method according to claim 1, wherein the temperature of said formed medium is in the range between 20-40° C.

35. A method according to claim 1, further comprising a step of processing said titanium solution to form a product selected from the group consisting of iron metal, an iron oxides, other iron product, products of other polyvalent cations present in said titanium feed solution and their combinations, which processing comprises crystallization.

36. A method according to claim 35, wherein said iron product is selected from the group consisting of a iron double salt, iron oxide and iron hydroxide.

37. A method according to claim 36, wherein the anion of said iron double salt is selected from the group consisting of monovalent anions, divalent anions, halide anions, sulfate and bisulfate anions and a combination thereof.

38. A method according to claim 36, wherein said iron double salt comprises a cation selected from the group consisting of ammonium, sodium and potassium.

39. A method according to claim 35 wherein said compound of polyvalent cation is selected from the group consisting of neutral double salts, basic double salt, oxides, hydroxide and a combination thereof.

40. A method according to claim 1 further comprising the step of washing said separated precipitate to form washed precipitate with a purity of P4 and a wash solution with a purity of P5, wherein P4>P2>P5.

41. A method according to claim 40, wherein said washing is with a solution comprising at least one cation and at least one anion selected from said groups of claim 1, and wherein the concentration of said anion is higher than 15 wt % and the ratio between the concentrations of said cation and said anion in said titanium solution is higher than 0.2 and lower than 1.6.

42. A method according to claim 40, wherein said washing is with a solution comprising protons, ammonium and sulfate ions.

43. A method according to claim 1, further comprising the step of re-crystallizing said 171,363/3 20 precipitate, optionally pre-washed, to form a precipitate with a purity of P6 and a mother liquor with a purity of P7, wherein P6>P2>P7.

44. A method according to claim 43, wherein said re-crystallization uses a solution comprising at least one cation and at least one anion selected from said groups of claim 1.

45. A method according to claim 43, wherein said re-crystallization is induced by an action selected from the group consisting of adding a salt of a monovalent-cation, adding a base of a monovalent-cation, increasing temperature, dilution and a combination thereof.

46. A method according to claim 1, further comprising the steps of: a. dissolution of a titanium double-salt in aqueous solution; and b. inducing a change of the conditions to cause a titanium oxide precipitation from said solution, wherein said change is selected from the group consisting of dilution, temperature elevation, increasing pH and a combination thereof..

47. A method according to claim 1, wherein P2 is greater than 80%.

48. A method according to claim 1, wherein P2 is greater than 85%.

49. A method according to claim 1, wherein P2 is greater than 950%. For the Applicant