Method for producing pseudobrookite powder usable as a brown pigment

Abstract

The invention relates to a method for producing heat-resistant pseudobrookite powder, reducing the amount of waste in the process of producing pseudobrookite from ilmenite, and to pseudobrookite powder obtained by this method.

Description

[0001] METHOD FOR PRODUCING PSEUDOBROOKITE POWDER USABLE AS A BROWN PIGMENT

[0002] Technical Field of the Invention

[0003] The invention relates to a method for producing heat-resistant pseudobrookite brown pigment from ilmenite using a combination of hydrometallurgical and pyrometallurgical processes which eliminate the disposal of acidic waste to the environment.

[0004] State of the Art of the Invention

[0005] Pseudobrookite (Fe2TiOs) powder is a highly durable pigment, valued for its intense yellowish- brown color and its exceptional resistance to high temperatures and harsh chemicals. These properties make it a preferred coloring agent for demanding applications, particularly in the ceramics industry, as well as in plastics, paints, cement, and leather, where it can withstand the rigors of the manufacturing process.

[0006] The traditional method for producing pseudobrookite is to mix TiCh and Fe2O3 in powder form and calcine them between 900 and 1300 °C. The product obtained from calcination can be brought to the desired size by physical processes such as grinding.

[0007] In the older techniques used, the production of pseudobrookite powder takes place by supplying precursors (TiCh and Fe2Ch) or by producing these precursors prior to the production of pseudobrookite. These methods are costly and also increase the expense of pseudobrookite and limit access to pseudobrookite pigment.

[0008] Ilmenite (FeTiCh) is a mineral found in many igneous and metamorphic rocks. It is a compound that already contains the elements iron, titanium and oxygen, which also make up the pseudobrookite compound, and has the potential to significantly reduce the cost of production if used as a raw material in pseudobrookite production.

[0009] Mahmoud et al. [1] describes a production method using ilmenite as raw material. In this method, ilmenite is leached with hydrochloric acid (HC1) and the titanium and iron elements in ilmenite are decomposed as TiOCh and FeCh. FeCh is added to the resulting solution to achieve the 2: 1 Fe-Ti stoichiometry required for the production of pseudobrookite and this solution is neutralized with sodium hydroxide (NaOH). This leads to the precipitation of iron(II), iron(III), and titanium. The precipitated solid is subjected to calcination after filtration, washing, and drying. In this process, NaCl salt is released as a waste as a result of neutralization. TiOCh and FeCh also release Ch, a toxic gas, during calcination.

[0010] Gazquez et al. [2] describes a system for producing titanium oxide (TiO2) using ilmenite as a raw material. In this process, ilmenite is leached with H2SO4 and the resulting liquid contains TiOSO4 and FeSO4. The liquid containing undissolved solids is subjected to clarification and the solid phase is separated from the liquid. The clarified liquid is compared with steam and the titanyl sulfate (TiOSO4) within is converted into titanium dioxide crystals, thus recovering H2SO4. The crystallization reaction of titanyl sulfate with steam is as follows:

[0011] T10S04+ H20 - T102n. H20 + H2S04

[0012] As known in the prior art, hydrochloric acid used in the leaching of ilmenite can easily evaporate even at low temperatures and causes sudden changes in solution concentration. Furthermore, hydrochloric acid has highly corrosive properties, damaging equipment and shortening its lifetime.

[0013] There are cases where sulfuric acid is used to leach ilmenite, however these methods are not used for pseudobrookite production and do not achieve effective sulfuric acid recovery due to the sulfur content in the by-products. Even in methods where the TiCh and Fe2O3 precursors used in the known art are not supplied and these precursors are obtained by processing ilmenite, these methods have many process steps up to the calcination stage. In order to achieve a relatively low cost and waste-free process, it is essential to recover the acid and reduce the mentioned process steps. As a result, all the above-mentioned problems have made it imperative to make an innovation in the relevant field. Summary of the Invention

[0014] The object of the invention is to provide a low-cost method of producing pseudobrookite in which the amount of waste is reduced or completely eliminated and to obtain a pseudobrookite pigment powder with properties suitable for industrial use.

[0015] The invention processes the mineral ilmenite (FeTiCh), which is abundant in various rocks, as a raw material for the production of pseudobrookite. In order for this mineral to be converted into pseudobrookite, iron and titanium must first be separated. The present invention performs the baking process for this separation using sulfuric acid, thereby solving problems such as unstable concentrations and shortened equipment life that arise in processes employing more volatile and more corrosive acids such as hydrochloric acid.

[0016] Moreover, the integration of the renewable use of sulfuric acid into the method leads to a considerable reduction in the amount of waste. This renewable use, unlike other methods, does not involve steps such as neutralization and precipitation prior to calcination, and allows the production of pseudobrookite powder by thermal decomposition of ferrous sulfate and titanyl sulfate cake formed by sulfuric acid baking in a single step. In addition, the sulfur-based gas generated in the thermal composition is converted into sulfuric acid for reuse in the ilmenite baking phase.

[0017] Descriptions of the Figures Describing the Invention

[0018] The figures and the related descriptions used in order to better describe the production method developed with this invention are as follows.

[0019] Fig- 1- Flow diagram image of the designed production method

[0020] Fig. 2. Image of a conversion and acid recovery unit used in a preferred embodiment of the invention

[0021] Fig. 3. XRD analysis result of pseudobrookite produced by the methods of the invention and the image of the round diagram showing its composition Fig. 4. Absorption-wavelength graph of pseudobrookite produced by the preferred methods as a result of ultraviolet-visible spectroscopy analysis

[0022] Fig- 5. SEM images (left) and EDS results (right) of pseudobrookite produced by the preferred methods

[0023] Fig. 6. Image of elemental X-ray maps of pseudobrookite produced by preferred methods

[0024] Fig- 7. Table showing the elemental composition of pseudobrookite obtained by interpretation of elemental X-ray maps

[0025] Definitions of the Elements / Features / Parts of the Invention

[0026] In order to better describe the method developed with this invention, the features and parts in the figures are numbered and the equivalent of each number is given below.

[0027] 10. Tube furnace

[0028] 20. Gas converter

[0029] 21. Catalyst

[0030] 30. SCh-Acid converter

[0031] 31. Oleum

[0032] 32. Liquid inlet

[0033] Detailed Description of the Invention

[0034] The subject matter of the invention relates to a system for recovering sulfuric acid used for baking ilmenite in the production of pseudobrookite powder / pigment and to pseudobrookite obtained by this method.

[0035] The subject matter of the invention relates to a production method comprising thermal decomposition of baked ferrous sulfate and titanyl sulfate cake and the resulting pseudobrookite. This thermal decomposition is a one-stage process. Fig. 1 shows the flow diagram of the designed process. As seen in the diagram, ilmenite (FeTiCh) is first baked with sulfuric acid (H2SO4). This process results in an output containing a large proportion of ferrous sulfate (FeSCfi) and titanyl sulfate (TiOSCfi). The cooking process carried out with the mentioned ratios is more efficient. The output is preferably in cake form. What is meant by the expression cake is the high output of the solid phase and the low output of the liquid phase. Using sulfuric acid in baking and recovering sulfuric acid provides the process with concentration stability, process safety, and relatively long equipment life, unlike some commonly used acids. One of the benefits of this method is the extended equipment lifetime, a factor that leads to lower production costs.

[0036] Preferably the concentration of sulfuric acid used in baking is more than 70%. Preferably, the acid to ore ratio is chosen to be 1.2 / 1. It was observed that productivity increased at the mentioned ratios.

[0037] The output from this baking is sent to a single-stage thermal decomposition unit. Thermal decomposition produces pseudobrookite (Fe2TiOs) powder and sulfur-based gas that will be used for recycling.

[0038] In a preferred embodiment of the invention, the sulfur-based gas comprises at least SO2 and / or SO3.

[0039] Preferably, thermal decomposition is carried out between 700 and 1300 °C. Preferably and most preferably at 1000°C, the process continues at constant temperature after reaching a decomposition temperature within the specified range.

[0040] In the thermal decomposition stage, ferrous sulfate (FeSOi) and titanyl sulfate (TiOSOi) are converted into metal oxide compounds without additional treatment. In a preferred embodiment of the invention, all sulfates are converted to oxides after thermal decomposition at a constant temperature for 1.5 hours. Metal oxide compounds refer to pseudobrookite powder and impurities thereof. This method does not involve precipitation or any separation process steps that are present in the prior art. This leads to a dramatic reduction in the cost of production.

[0041] The sulfur-based gas released from thermal decomposition contains SO2, a harmful compound. Preferably the sulfur-based gas is converted to SO3. This prepares the sulfur-based gas for conversion to sulfuric acid. The removal of SChfrom the sulfur-based gas is important in terms of eliminating harmful gas, as well as preventing undesirable compounds that may arise during the conversion to sulfuric acid and ensuring high efficiency during the acidification phase.

[0042] In a preferred embodiment of the method, oxidation of the sulfur-based gas takes place in the converter (20) containing the catalyst (21). In this embodiment, at least some of the SCh in the sulfur-based gas is converted to SO3. Again, in a preferred embodiment of the method, V2O5 is used as catalyst (21).

[0043] SO3 gas is converted to sulfuric acid (H2SO4) by reaction with water for recovery. Preferably, this reaction can take place by directly absorbing the sulfur-based gas into water. However, this method is disadvantageous in terms of process safety due to the sudden reaction.

[0044] In a preferred embodiment of the invention, SCh-acid conversion takes place in the absorbent- free converter (30). Concentrated H2SO4 liquid input (32) is introduced into the system, preferably by spraying and combines with SO3 gas present in the sulfur-based gas to form oleum (31). Sulfuric acid is recovered by reacting oleum with water.

[0045] The recovered sulfuric acid is fed back into the system, preferably through a recycling pipe and used to bake the ilmenite. This reduces the waste from the sulfuric acid used. In addition to the environmental benefits, this method reduces the cost of production by reducing the supply of sulfuric acid.

[0046] Preferably, the resulting pseudobrookite powder is washed and dried. Subsequently, the grinding process takes place and the product particles are brought to the desired size. The final product is then ready.

[0047] The final product, produced according to the preferred methods, has the preferred particle size, a rich brown-yellow hue and is ready to be used as pigment.

[0048] By analyzing the final product, which has a brown-yellow hue and is ready to be used as a pigment, its advantages and the reasons for its preference in various applications can be more clearly understood.

[0049] The graph shown in Fig. 3 is obtained from the results of X-ray diffractometer (XRD) analysis of pseudobrookite produced by the preferred methods. In the line graph, which is the output of this analysis, the result obtained from the final product (Fe2TiOs) was compared with reference patterns (PDF 96-200-2303 Fe2TiO5, PDF 96-900-4144^TiO2, PDF 96-153- 1066- calcium aluminum silicate compound) and the ratios of the mentioned compounds in the product were determined. The product produced by the preferred methods was found to contain significant amounts of titanium oxide (TiO2). However, this should not be perceived as a disadvantage. In these industries, where it is beneficial to obtain bright and saturated colored pigments, the increased opacity and refractive index with titanium oxide content contribute to the mentioned color properties.

[0050] The results of ultraviolet-visible spectroscopy analysis of samples of pseudobrookite produced by the preferred methods are shown in Fig. 4. This analysis shows high peaks at wavelengths of 420 nm and 460 nm, indicating the presence of specific electronic transitions in the pseudobrookite structure. A broader absorption band between 300 nm and 500 nm is also observed. The presence of this band indicates that the pseudobrookite pigment produced by the preferred methods can absorb wavelengths in the ultraviolet and visible region.

[0051] Samples of pseudobrookite produced by the preferred methods were also examined by scanning electron microscopy (SEM) and the results are shown in Fig. 5. It was found that the particles were approximately 30-40 nm in size and showed a hard and porous surface morphology. This porous structure was formed during gas formation during thermal decomposition.

[0052] The high porosity microstructure provides better dispersion of the pigment into the material in which it is contained.

[0053] Moreover, the porosity structure provides an advantage in the use of the synthesized pseudobrookite powder as a photocatalyst, as it contains a relatively high surface area, thus increasing the area where the reaction can take place.

[0054] Again, porosity is a sought-after property in the anode material used in lithium batteries. Increased porosity facilitates the penetration of electrolyte into the anode. Increased porosity facilitates ion diffusion to the anode. Increased porosity compensates for the volume change in the anode during the charge / discharge cycle, extending the life of the battery. The pseudobrookite produced by the preferred methods was subjected to energy dispersive X- ray spectroscopy (EDS) analysis. Fig. 5, which provides the results of this analysis, shows that very high and prominent peaks corresponding to titanium, iron, and oxygen were detected. Smaller peaks reveal impurities in the pigment produced by the preferred method. These impurities are due to the different minerals and elements found in ilmenite.

[0055] The SEM-EDS analysis of the product obtained by the preferred methods contains different contrasts as seen in Fig. 6 and therefore shows the presence of different phases and regions, in other words, the presence of regions with different compositions and densities.

[0056] The elemental X-ray maps given in Fig. 6 show the regional distribution of elements such as Fe, Ti, Mg, Al, Si, K, Ca, and Mn. The regions where Fe and Ti elements are concentrated indicate the presence of pseudobrookite (Fe2TiOs) phase. Fig. 7 shows a digitized version of the elemental mapping results. The data in Fig. 7 are indicative of the high concentration of elemental iron (26.55%) and titanium (33.84%) (by weight) present in the phase.

[0057] The analysis shows that the obtained pseudobrookite powder contains impurities such as Mg, Al, Si, K, Ca, and Mn. The resulting pseudobrookite powder has a purity of 93%-95%.

[0058] The aforementioned analysis results confirm that the pseudobrookite pigment produced by the preferred method is preferred in ceramics, paint, cement, leather, etc. industries due to the color and optical characteristics thereof. Moreover, the fact that it has the capacity to absorb light in wide band ranges paves the way for the obtained product to be used as a photocatalyst.

[0059] REFERENCES

[0060] 1. Mahmoud, Mohamed H. H., et al. “Physicochemical Properties of Pseudobrookite Fe2TiO5 Synthesized from Ilmenite Ore by Co-Precipitation Route.” Physicochemical Problems of Mineral Processing, May 2018, doi: 10.5277 / ppmpl8131.

[0061] 2. Gazquez, Manuel Jesus, et al. “A Review of the Production Cycle of Titanium Dioxide Pigment.” Materials Sciences and Applications, no. 07, Scientific Research Publishing, Inc., 2014, pp. 441-58. Crossref, doi: 10.4236 / msa.2014.5704.

Claims

1. CLAIMS1. A production method of pseudobrookite powder, characterized in that it comprises the process steps of:• baking ilmenite (FeTiCh) with concentrated sulfuric acid (H2SO4),• obtaining pseudobrookite (Fe2TiOs) powder by thermal decomposition and reusing the sulfur-based gas formed during this process in ilmenite baking by converting it into sulfuric acid.

2. The method according to claim 1, characterized in that the cake obtained as a result of baking is converted into pseudobrookite powder by thermal decomposition in a single step.

3. The method according to claim 2, characterized in that said cake comprises titanyl sulfate (TiOSC ) and ferrous sulfate (FeSC ).

4. The method according to claim 1 or 3, characterized in that said thermal decomposition is carried out at 700 to 1300 °C and the sulfur-based gas resulting from said thermal decomposition is converted.

5. The method according to claim 4, characterized in that the temperature is kept constant during the thermal decomposition process.

6. The method according to any one of the preceding claims, characterized in that a catalyst is used in the conversion of the sulfur-based gas.

7. The method according to claim 6, characterized in that V2O5 is used as catalyst.

8. The method according to any one of the preceding claims, characterized in that the H2SO4 reused in said ilmenite baking process is obtained from the reaction of SO3 or oleum with water.

9. The method according to claim 8, characterized in that said oleum is obtained by reacting sulfur-based gas with concentrated sulfuric acid.

10. The method according to claim 8, characterized in that the sulfur-based gas is absorbed into the water for the reaction of SO3 gas with water.

11. The method according to any one of the preceding claims, characterized in that the Sulphurbased gas contains SO2 and / or SO3.

12. The method according to any one of the preceding claims, characterized in that the pseudobrookite powder obtained is washed and dried.

13. The method according to claim 12, characterized in that said pseudobrookite powder is finely grinded.

14. The pseudobrookite powder obtained by the method according to any one of the preceding claims.

15. The photocatalyst comprising pseudobrookite powder according to claim 14.

16. The anode comprising pseudobrookite powder according to claim 14.

17. The pseudobrookite pigment according to claim 14.