FIELD OF THE INVENTION [0001] The present invention relates to field of preparing titanium dioxide nanomaterials. More particularly, the present invention relates to a process and system for extracting titanium dioxide nanomaterials from natural ilmenite.

BACKGROUND OF THE INVENTION

[0002] Lanka Mineral Sands Limited, fully owned by the Government of Sri Lanka, is the successor to Ceylon Mineral Sands Corporation, established under the Industrial Corporation Act in 1957. The functions of the Lanka Mineral Sands Limited include mining, processing and exporting of heavy mineral beach sands.

[0003] Sri Lanka is endowed with a verity of industrial minerals such as ball clays, kaolin and other clays, calcite, dolomite, feldspar, gemstones, limestones, phosphates rock, mica, silica, graphite and mineral sands. Among them, mineral sands deposits represent a most promising and profitable future resources for the country.

[0004] The main deposits are found at Pulmoddai on the north eastern coast of Sri Lanka. These deposits are of high grade, comprising of over 80% heavy mineral content, with an approximate composition of 70-72% ilmenite, 8- 10% zircon, 8% rutile, 1% sillimanite and 0.3% monazite.

[0005] The annual production of ilmenite, rutile, zircon, monazite and high- titanium ilmenite is approximately 90000, 9000, 5500, 100 and 4000 tonnes respectively. Ilmenite is the dominant mineral present in these deposits and the amount estimated by the Geological Survey and Mines Bureau (GSMB) of Sri Lanka is around 6 - 8 million Metric Tonnes. Ilmenite is chemically a combination of iron oxide and titanium dioxide with the formula FeO.TiOi with silicate impurities.

[0006] Pulmoddai mines of Lanka Mineral Sands Ltd. uses physical methods to separate crude mineral sands into components such as ilmenite, rutile and zircon etc. Such separated mineral sands are exported to foreign countries. China stands out as the top buyer of mineral sands mined in Sri Lanka, since 2008. India and Japan are the second and third ranked buyers, respectively. Sri Lanka annually exports the raw ilmenite mineral sand to the value of US$ 8 million from which the end user extracts US$ 160 million worth of Tίq2· This sum is equivalent to a value-addition of 20 times the price of the raw ilmenite that Sri Lanka currently exports to the end user.

[0007] So far no attempt has been made to produce value-added end products from these sands in Sri Lanka. Compared to the world standards, Sri Lankan mineral sands are highly pure and contain low quantities of chromium and phosphate impurities which are major hazards in Australian and South African mineral sands. Silicate impurities present in Sri Lankan ilmenite can be easily removed.

[0008] The titanium element discovered in 1791 was first made into metal in 1910. The “Ti” metal has earned commercial demand since 1950s after it was named as the “wonder metal of the age”. “Ti” is the 9 ^th most abundant element on the Earth’s crust representing approximately 0.6% of elemental composition.

[0009] According to “Mehdilo, A. & Irannajad, M., 2012, Iron removing from titanium slag for synthetic rutile production, Physicochemical Problems of Mineral Processing, 48(2), 425-439”, the titanium element occurs in nature as a chemical compound mostly in combination with oxygen and iron in about 45 different minerals but most commonly as ilmenite, rutile and titanomagnetite. [0010] Further, the said paper also discloses that commercial plants have been set up in many countries and intensive research programmes are under way to produce highly pure T1O2 and Ti metal, at a lower cost. Since current use is limited by cost, numerous industrial sectors, especially automotive, are eagerly anticipating developments in converting ilmenite to pure Ti02 _.

[0011] Further, another research paper by “Wilson, N. C., Muscat, J., Mkhonto, D., Ngoepe, P. E., & Harrison, N. M., Structure and properties of ilmenite from first principles, Physical Review B-Condensed Matter and Materials Physics, 71(7)” discloses that the most valuable minerals for their titanium content are rutile and ilmenite.

[0012] The paper further suggests that mineral ilmenite (FeO.TiC^) is relatively abundant whereas rutile (T1O2) is in short supply. The price of rutile in the world market is over 10 times that of ilmenite. This is due to low natural abundance and high purity of T1O2 in rutile compared to highly abundant ilmenite containing chemically impure T1O2. As such, conversion of ilmenite to chemically pure titanium dioxide is desirable to meet with global demand of titanium dioxide.

[0013] Another research paper by “El-hazek, N., Lasheen, T. A., El-sheikh, R., & Zaki S.A., 2007, Hydrometallurgical criteria for T1O2 leaching from Rosetta ilmenite by hydrochloric acid, 87, 45-50. ’’discloses that titanium dioxide nanoparticles are very important inorganic chemical material, especially the best- quality white pigment. Titanium dioxide pigments are used to enhance colours and quality from ancient times. They are inexpensive, chemically stable and absorption-active under UV irradiation. It has high whiteness, high refractive index and light scattering ability. These characteristics make T1O2 the predominant component of white pigments in paints, paper, plastics and rubber.

[0014] Due to the unique characteristics of the titanium dioxide, it is also used in environmental purification, gas sensors, and in photovoltaic cells. Further, T1O2 is also used in pharmaceutical and cosmetic industries in large scale. Therefore, the demand for T1O2 is expected to grow within the next 5 to 10 years at a similar ration as that of the world economy.

[0015] Although titanium-containing economic minerals are abundantly available in Sri Lanka, no attempt has been devoted to the production of T1O2 pigment and Ti metal. However, many processes have been developed to up-grade ilmenite and to produce pure titanium dioxide and titanium metal.

[0016] According to another research paper “Jayasekera, S., Marinovich, Y., Avraamides, J., & Bailey, S. L, Pressure leaching of reduced ilmenite : electrochemical aspects, 39, 183-199”, currently, there are two processes, namely, sulphate process and chlorination process that are used throughout the world, for the purification of titaniferous materials to manufacture pigment grade titanium dioxide or even titanium metal. The sulphate process is capable of processing low-grade ilmenite, where inilmenite is digested with strong sulfuric acid yielding a titanium sulphate solution which is then hydrolyzed and precipitated to form T1O2 directly.

[0017] In this regard, a WIPO patent publication number 2004035841A1 discloses a sulfate process for producing titania from a titaniferous material. The process includes leaching the titaniferous material and producing leach liquor, separating titanyl sulfate from leach liquor, hydrolysis of the extracted titanyl sulfate, and thereafter calcining the solid phase produced in the hydrolysis step. The process is characterized by multiple stages leaching of the titaniferous material.

[0018] However, the said patent does not produce titanium dioxide materials of nanoparticles size. Further, the said patent discloses that that leaching is done by sulfuric acid, which is highly acidic in nature.

[0019] Further, another research paper "Liang, B., Li, C., Zhang, C. & Zhang, Y., 2005, Leaching kinetics of Panzhihua ilmenite in sulfuric acid, 76, 173-179” also discloses that the said sulphate process is environmentally hazardous since it produces acidic ferrous sulphate waste. Moreover, the products are relatively inferior.

[0020] A research paper “Jayasekera, S., Marinovich, Y., Avraamides, J., & Bailey, S. L, Pressure leaching of reduced ilmenite : electrochemical aspects, 39, 183-199” discloses that a chloride process requires a higher-grade feedstock than the sulphate process, necessitating the upgrading of the ilmenite in an intermediate thermal production step to remove most of the iron and other impurities.

[0021] The said thermal reduction is required to be done in rotary kilns to produce synthetic rutile or in a furnace to create a titaniferous slag. The thermally reduced product is then processed with chlorine to make a high-purity Tίq2· This leads to higher expense of operating the chloride process.

[0022] A research paper “Abdou, A. A., Manaa, E. A., & Zaki, S. A., Synthetic rutile preparation from Egyptian Ilmenite using hydrochloric acid in the presence of cellulose as reducing agent, 2(1), 443-451.” discloses that to produce Ti metal, titaniferous concentrates are generally processed by chlorination to produce titanium tetrachloride, which is reduced with magnesium to produce Ti metal. The chlorination process yields a higher quality product of titanium dioxide pigments than that of the product obtained from the sulphate process.

[0023] Having said that, both the processes above face the problems of producing large amounts of wastes or toxic by-products and hence requiring serious action to avoid pollution to the environment.

[0024] Furthermore, both the said processes demand elevated temperatures over 1000 °C and such high temperatures are maintained in electrical furnaces. As such, a debilitating factor in the operation of such a factory in middle income countries, such as Sri Lanka, is the high electricity costs, as electricity is a major requirement to extract T1O2 from ilmenite sand by the said processes. [0025] Further, currently used sulphate and chloride processes only produce micrometer size particles and size reduction to nanoscale of 1 nm to 100 nm at least in one dimension by these processes have not been achieved.

[0026] It will be appreciated by those skilled in the art that nanomaterials have the inherent advantage of having significantly large surface area compared to micro- materials. For instance, 1 mg of 1 nm particles has the same surface area as 1 kg of 1 pm particles.

[0027] Further, most of the practical applications of solid state materials rely on their surface area as the exposed atoms/ions are the atoms/ions that are active and the higher the surface area higher is the number of surface atoms that are exposed. As such, in place of 1 kg of 1 pm particles only 1 mg of 1 nm particles is required for practical applications.

[0028] These aspects involve a huge reduction in material usage in a given industrial application since in this extreme case there is a million-fold material saving when 1 pm particles are reduced to 1 nm size. In usual practical applications, size reduction to 1 nm is not mandatory and even if 100 nm particles are used there is 10-fold material saving.

[0029] Reducing the amount of material required for a given industrial process has several advantages such as minimum utilization of limited amount of natural resources, highly reduced waste disposal and long-term utilization of limited natural resources all of which contribute to substantial cost-reduction.

[0030] Therefore, a process and system are required to extract highly value-added titanium dioxide nanomaterials from mundane mineral ilmenite.

[0031] In nutshell, the process and system are required which may overcome above discussed drawbacks and provide easy to operate and a cost-effective method for extracting titanium dioxide nanomaterials. [0032] The process and system should be able to operate at lower temperatures to extract pure titanium dioxide nanomaterials such as nano-rods and nanoparticles from natural ilmenite.

SUMMARY OF THE INVENTION

[0033] In an aspect of the present invention, a process for extracting titanium dioxide nanomaterials from natural ilmenite at moderate conditions is disclosed.

[0034] The process includes pre-treating the said ilmenite to form ilmenite particles having size in the range of 50-200 micrometer.

[0035] In one embodiment of the present invention, the pre-treating of the said ilmenite includes purifying the said ilmenite via a magnetic separator operating with forward angle and side angle in range of 1 -90° by applying voltage in range of 0-50 Volts and current in range of 0-10 Ampere, and milling by a dry ball mill to obtain the said ilmenite particles having size of 50-200 micrometers (mhi).

[0036] In an embodiment of the present invention, the process further includes leaching out iron from the said ilmenite particles by treating the said ilmenite particles with a first acid solution at predetermined hydrothermal conditions in a closed rotary system of an autoclave.

[0037] In an embodiment, the first acid solution is aqueous hydrochloric acid

(HC1) of molar range of 5-10 moldm , the said aqueous HC1 being filled in the autoclave operated at 100-300 °C, the said HC1 being in range of 50-90% volume of the said autoclave.

[0038] Further, the process includes treating the resultant residue particles to obtain an intermediate product.

[0039] In one embodiment of the present invention, the treating of the resultant residue particles includes filtering the said resultant residue particles by cellulose nitrate membrane filter of pore size in the range of 0.1-2 micrometer (qm) to form sedimental intermediate product. [0040] Further, the said sedimental intermediate product is washed with aqueous hydrochloric acid (HC1) followed by the water to obtain hydrolyzed intermediate product, and dried by creating vacuum in a vacuum oven at a temperature condition in the range of 50°C-150°C.

[0041] The process further may include treating the said intermediate product to extract the said titanium dioxide (T1O2) nanomaterials. The said treatment of the said intermediate product includes reacting the said intermediate product with aqueous hydrogen peroxide (H2O2) in alkaline medium at a temperature condition in range of 30°C-100°C for 1-5 hours under a reflux technique to obtain titanium solution.

[0042] In one embodiment of the present invention, the alkaline condition may be maintained by adding aqueous alkali solution comprising sodium hydroxide

(NaOH) solution in the range of 0.1-2 mol dm .

[0043] In this embodiment, the said aqueous sodium hydroxide (NaOH) is being added in range of 50-300 milliliter for lgram of the intermediate product.

[0044] In another embodiment, the alkaline condition may be maintained by adding at least one of KOH, LiOH, RbOH, NH ₄ OH, Ca(OH) ₂ , Ba(OH) ₂ , and Mg(OH) ₂ .

[0045] In one embodiment of the present invention, 20-40% aqueous hydrogen peroxide (H2O2) solution is added in range of 1-50 ml to react with the said intermediate product.

[0046] Subsequently, the process includes centrifuging to obtain a supernatant comprising the leached titanium compounds. The said titanium compounds is mixed with a solution of hexadecyltrimethylammonium bromide in micelle concentration and water-alcohol at a temperature condition in the range of 50°C- 300°C for 1-5 hours. The obtained mixture is processed, thereby extracting the said titanium dioxide (T1O2) nanomaterials with 100 % purity. [0047] In one embodiment of the present invention, the said processing of the obtained mixture includes filtering, washing, and ultra-sonication by acetic acid and distilled water. Further, the resultant mixture is heated at 150°C to obtain amorphous titanium oxide (T1O2) nanomaterials, followed by calcination of the said amorphousTi0 ₂ nanomaterials to obtain the T1O2 nanomaterials of anatase phase and rutile phase.

[0048] In one embodiment of the present invention, the said calcination is carried at a temperature in the range of 300°C-500°C for 2-5 hours to obtain the titanium oxide (T1O2) nanomaterials of anatase phase.

[0049] In another embodiment of the present invention, the said calcination is carried at a temperature in the range of 600°C-800°C for 2-5 hours to obtain the titanium oxide (T1O2) nanomaterials of rutile phase.

[0050] In one embodiment of the present invention, the said nanomaterials are in a form of nanoparticles, nanorods, nanoflowers, nanoplates or like.

[0051] In an aspect of the present invention, the present invention provides an apparatus, which is adapted to provide a closed system for carrying out the said process.

[0052] The apparatus includes a block base. The apparatus further includes an autoclave having a stainless steel container, Teflon reaction vessel liner, a screw- fit Teflon lid, screw-fit stainless steel lid with Allen-key for leak-proof tightening, stainless steel weights and springs.

[0053] The apparatus further includes an electric oven housing the autoclave. Further, the said apparatus includes an autoclave holder for fitting the autoclave to the electric oven.

[0054] In the apparatus, a rotational bar is connected to the electric oven with a plurality of ball bearings. Further, a rotating mechanism is adapted for rotating the said autoclave. The rotating mechanism comprising a combination of belt system, sheave system and gear motor. [0055] In another aspect of the present invention, the present invention also provides a system for extracting nanomaterials from natural ilmenite at moderate conditions.

[0056] The system includes a magnetic separator adapted to purify the said ilmenite. The said system further includes a dry ball mill adapted to mill pure ilmenite to obtain ilmenite particles. The dry ball mill produces particles having size of 50-200 micrometers.

[0057] The system further includes an apparatus comprising an autoclave. The said autoclave is adapted to leach out iron from the said ilmenite particles by treating the said ilmenite particles with a first acid solution at predetermined hydrothermal conditions to obtain resultant residue particles in a closed rotary system of the said autoclave. The obtained resultant residue particles are treated to obtain intermediate product.

[0058] In one embodiment of the present invention, the said apparatus is adapted to treat the said intermediate product to extract the said titanium dioxide (T1O2) nanoparticles.

[0059] This together with the other aspects of the present invention along with the various features of novelty that characterized the present disclosure is pointed out with particularity in claims annexed hereto and forms a part of the present invention. For better understanding of the present disclosure, its operating advantages, and the specified objective attained by its uses, reference should be made to the accompanying descriptive matter in which there are illustrated exemplary embodiments of the present invention.

DESCRIPTION OF THE DRAWINGS

[0060] The advantages and features of the present invention will become better understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which: [0061] Fig. 1-lC illustrate flow charts depicting an exemplary process for extracting nanomaterials from natural ilmenite at moderate conditions, according to various embodiments of the present invention;

[0062] Fig. 2 illustrates a schematic diagram of apparatus for carrying out the process for extracting nanomaterials from natural ilmenite at moderate conditions as described with reference to Fig.l, according to various embodiments of the present invention;

[0063] Fig. 3 illustrates a schematic diagram of autoclave of the present invention, according to various embodiments of the present invention;

[0064] Fig. 4 illustrates a schematic diagram of nanorods formationwithin soft templated micelle structure, according to various embodiments of the present invention;

[0065] Fig. 5 illustrates a graph representing an Energy Dispersive X-Ray (EDX) analysis of samples obtained vide the process, according to various embodiments of the present invention;

[0066] Fig. 6 illustrates a graph representing powder X-ray diffractogrammes of samples obtained vide the process, according to various embodiments of the present invention;

[0067] Fig. 7 illustrates a graph representing a Tauc plot of absorption data of the T1O2 product obtained vide the process, according to various embodiments of the present invention;

[0068] Fig. 8 illustrates scanning electron microscopy (SEM) images of T1O2 samples obtained vide the process, according to various embodiments of the present invention;

[0069] Figs. 9a & 9b illustrate scanning electron microscopy (SEM) images of T1O2 nanomaterials in form of nanowires obtained vide the process, according to various embodiments of the present invention; [0070] Figs. 10a & 10b illustrate scanning electron microscopy (SEM) images of TiOinanomaterials in form of nano-flowers obtained vide the process, according to various embodiments of the present invention;

[0071] Figs. 11a- lid illustrate scanning electron microscopy (SEM) images of TiO nanomaterials in form of nanorods obtained vide the process; and

[0072] Fig. 12 illustrates an exemplary block diagram representing system for extracting nanomaterials from natural ilmenite, according to various embodiments of the present invention.

[0073] Like numerals denote like elements throughout the figures.

DESCRIPTION OF THE INVENTION

[0074] The exemplary embodiments described herein detail for illustrative purposes are subjected to many variations. It should be emphasized, however, that the present invention is not limited to a process and system as disclosed. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

[0075] Specifically, the following terms have the meanings indicated below.

[0076] The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.

[0077] The terms “having”, “comprising”, “including”, and variations thereof signify the presence of a component.

[0078] The present invention relates to a process and system for extracting titanium dioxide nanomaterials from natural ilmenite at moderate conditions. The inventive aspects of the invention along with various chemical reactions and engineering involved, will now be explained with reference to Figs. 1-12 herein. [0079] Fig.l illustrates a process for extracting titanium dioxide nanomaterials from natural ilmenite at moderate conditions according to the present invention. It will be apparent to a person skilled in the art that the term “ilmenite” used herein refers to naturally occurring ore of titanium, a metal needed to make a variety of high-performance alloys.

[0080] The ilmenite used for the purpose of this invention is sourced from Sri Lanka Mineral Sands Ltd. However, it should be clearly understood that the present disclosure may be employable for extracting titanium dioxide nanomaterials from any ilmenite raw material.

[0081] The process, according to various embodiments of the present invention, for extracting titanium dioxide nanomaterials from the natural ilmenite at moderate conditions starts with step (20).

[0082] At step (20), the process involves pre-treating the said ilmenite to form pre-treated ilmenite particles. The said ilmenite particles are sized in range of 50- 200 micrometer.

[0083] In an embodiment of the present invention, the said pre-treating involves purifying the said ilmenite via a magnetic separator, such as magnetic separator (16) shown in Fig. 12.

[0084] In the embodiment, the said separator (16) operates with forward angle and side angle in range of 1-90° by applying voltage in range of 0-50 Volts and current in range of 0-10 Ampere in the said separator (16).

[0085] In an exemplary embodiment of the present invention, the said magnetic separator (16) is operated with forward angle of 19° and side angle 15° side angle by applying voltage 17.7 V and current of 0.3A to obtain pure ilmenite.

[0086] Although the magnetic separator (16) is specially designed to be adapted to carry out the separation as required for the present invention, the basic design elements thereof resemble those in conventional systems. Further, it should be understood that the operating parameters listed are of exemplary nature, and do not connote any limitation on the present invention.

[0087] Further, post the magnetic separation, the said purified ilmenite is milled by a dry ball mill (18) to obtain the said ilmenite particles preferably sized around 50-200 micrometers (pm) used in step (20). The process flows to step (22).

[0088] At step (22), the process involves leaching out iron from the said ilmenite particles by treating the said ilmenite particles with a first acid solution at predetermined hydrothermal conditions in a closed rotary system of the autoclave, such as rotary autoclave (15) shown in Fig.3.

[0089] In this embodiment of the present invention, the said first acid solution is an aqueous hydrochloric acid (HC1) of molar range of 5-10 moledm . The said aqueous HC1 is filled in the autoclave (15) in range of 50-90% volume of the said autoclave (15), and the said autoclave (15) is operated at 100-300 °C, for carrying out the treatment, with operating speed of round 1-60 revolutions per minute (rpm).

[0090] Although the leaching carried out in present invention is explained with respect to first acid being HC1, said explanation should not be construed as a limitation, accordingly, the present invention is equally employable with leaching being carried out by other equivalent inorganic acids, such as hydrogen bromide acid (HBr), nitric acid (HNO ₃ ), boric acid (H ₃ BO ₃ ), sulfuric acid (H ₂ SO ₄ ), carbonic acid (H ₂ CO ₃ ), phosphoric acid (H ₃ PO ₄ ), hydrofluoric acid (HF) and the like.

[0091] The result is leaching out iron in the rotary autoclave (15) by way of chemical reactions as shown in reactions (1) and (2) below.

FeTi<¾ _(S) +4HCl _(aq) Fe ²⁺ _(aq) + TiOC ² _(aq) + 2H ₂ 0 _(aq) (1)

FeTi03 _(s) +4HCl _(aq) FeCF _(aq > + TiOCl2 _(aq) + 2H ₂ 0 _(aq) (2) [0092] Coming back to the process, at step (24), the process (50) further involves treating the resultant residue particles obtained after step (22) to get an intermediate product.

[0093] The said process of treatment will now be explained with reference to Fig.lA.

[0094] The treating of the said residue particles includes first filtering the said resultant residue particles by cellulose nitrate membrane filter of pore size in the range of 0.1-2 micrometer (mhi) (Whatman™ with (0.1-2) pm pore size) to form a sedimental intermediate product as shown in step 24(a) (refer Fig. 1A).

[0095] To elaborate, TiOCU _(aq) and TiOCl2 _(aq) obtained in above reactions (1) and (2), undergo hydrolysis forming Ti0 ₂ .nH ₂ 0 _(s) and H ₂ Ti03 _(S) , respectively, in this step, as shown in reactions (3) and (4) below:

TiOCU ² _(aq) + (l+«) H ₂ 0 ₍₁₎ Ti0 ₂ .nH ₂ 0 _(s) + 2H ⁺ _(aq) + 2C1 _(aq) (3)

TiOCl _2(aq) + H ₂ 0( ₁₎ 2HCl( _aq) + H ₂ Ti0 _3(s) (4)

[0096] At step 24(b), the so obtained sedimental intermediate product, is then washed with an acid, such as aqueous hydrochloric acid (HC1), of strength 0.1-2 molar (M) followed by washing with water to obtain a hydrolyzed intermediate product (refer Fig. 1A).

[0097] In the embodiment of the present invention, at step 24(c), the said hydrolyzed intermediate product obtained at step 24(b), is dried at a temperature in the range of 50°C-150°C. Specifically, the said hydrolyzed intermediate product is dried at temperature of 70°C overnight in a vacuum oven by creating vacuum in the said oven to obtain the intermediate product (refer Fig. 1A).

[0098] At step (26), the process (50) further involves treating the said intermediate product to extract the said titanium dioxide (Ti0 ₂ ) nanomaterials. The process of treating of the intermediate product will now be explained with reference to Fig. IB. [0099] In the embodiment of the present invention, at step 26(a), the treatment of the said intermediate product involves reacting the said intermediate product with peroxide, such as 20-40 % aqueous hydrogen peroxide (H2O2), preferably 30 %

H ₂ O ₂ .

[00100] In the embodiment, the treatment is carried out in an alkaline medium, such as with sodium hydroxide (NaOH), of around 0.1-2 M, at a temperature condition in range of 10°C-100°C for 1-5 hours under a reflux technique to obtain a resulting titanium solution.

[00101] Chemically speaking at this step 26(a), the intermediate product i.e. titanium residues reacts with oxidizing peroxide (H2O2) in alkaline condition maintained with NaOH according to reactions (5) & (6). The process leads to formation of titanium solution containing Na _x Ti(0 ₂ )i(OH). Under these conditions, silica impurities may remain undissolved.

T1O2 .nH ₂ 0 _(S) + H2q2 _(ΐ) +NaOH _(aq) Na _x Ti(0 ₂ )i(OH) _{j +} nH ₂ 0 _(i) (5)

H ₂ Ti0 _3(s) + H ₂ 0 _2(i) +Na0H _(aq) Na _x Ti(0 ₂ )i(0H) _j(aq) -HUO® (6)

[00102] It will be appreciated by those skilled in the art that titanium oxide (T1O2) is an amphoteric oxide. Due to this, the said titanium oxide (T1O2) may react as an acid and base depending on the pH of the solution.

[00103] Since the reaction above is carrying out in the NaOH medium (high basic in nature), T1O2 acts as acid and reacts with NaOH (alkaline) to produce layered titanate of Na2Ti307 and ¾0 as shown below in reaction (7).

3Ti0 ₂ + 2NaOH Na ₂ Ti ₃ 0 ₇ + H ₂ 0 (7)

[00104] Subsequently, at step (26b), the said titanium solution is centrifuged to obtain a supernatant containing titanium compounds (refer Fig. IB).

[00105] In the exemplary embodiment of the present invention, the solution is centrifuged for 20 min at 5000 rpm to obtain supernatant containing the leached titanium compounds (refer Fig. IB). [00106] In the embodiment of the invention, the said supernatant is mixed with the solution of hexadecyltrimethylammonium bromide (HDTMA) surfactant at a concentration above its critical micelle concentration and ethanol.

[00107] The process further includes subjecting the resultant to the hydrothermal treatment in the closed system of the autoclave (15) at a temperature condition in the range of 50°C-300°C for 1-5 hours, at step 26b (refer Fig. IB). This results in formation of a disordered phase of NaiTisCF, which is present in the form of a layered structure.

[00108] These titanium particles are formed within the micelle structure, leading to a flowerlike morphology of rods emerging in all directions starting from one point (refer Fig. 4).

[00109] More specifically, Fig. 4 represents a schematic diagram of the bunches of nanorods formation when a soft template of HDTMA-water is used at the critical micelle concentration of the surfactant HDTMA. T1O ₂ particles arrange in the spaces provided within the spherical micelle structure.

[00110] Further, at step (26c), the process (50) involves processing of the said mixture obtained at step (26b), thereby extracting the said titanium dioxide (T1O ₂ ) nanomaterials with 100 % purity.

[00111] In this embodiment of the present invention, at step 26(i), the said obtained mixture i.e. white powder is filtered by a cellulose nitrate membrane filter (Whatman with (0.1-2) pm pore size) having a pore size in the range of 0.1-2micrometer (pm) (refer Fig. 1C).

[00112] Subsequently, the said filtered white powder is washed by ethanol and distilled water at step 26(ii). Finally, at step 26(iii), the resultant white powder is ultra- sonicated by acetic acid and distilled water for formation of H ₂ Ti ₃ 0 ₇ (s) as shown in reaction (8) (refer Fig. 1C).

Na ₂ Ti ₃ 0 _7(S) + 2H ⁺ _{(aq) *} H ₂ T 1 ₃ O _{7 (s)} +2Na ⁺ _(aq) (8) [00113] After ultra-sonication, further at step 26(iv), the resultant white powder is heated at 150°C to obtain amorphous T1O2 nanomaterials as shown in [reaction (9)] (refer Fig. 1C) _.

[00114] When heat-treated, only the surfactant is being removed by mineralization to carbon dioxide and water and the amorphous phase of titanium dioxide remains initially.

[00115] Specifically, the tubular structures bust into small particles due to dehydration of inter-layered OH groups that destroy the nanotubes structure. Specifically, the decomposition of H2T13O7 nanotubes takes place to obtain T i02nanomaterials .

H ₂ Ti ₃ 0 _7(S) 3Ti0 _2(s) + H ₂ 0 ₍ D (9)

[00116] In the embodiment of the present invention, as the heating temperature increases the amorphous T1O2 begin to crystallize and both anatase and rutile phases of the Ti02are obtained at step 26(v) (refer Fig. 1C).

[00117] In one embodiment of the present invention, the calcination is carried at the temperature in the range of 300°C -500°C for 2-5 hours, preferably at 350 °C for 3 hours to obtain the titanium oxide (T1O2) nanomaterials of anatase phase.

[00118] In another embodiment of the present invention, the calcination is carried at the temperature in the range of 600°C -800°C for 2-5 hours, preferably at 650°C for 3 hours to obtain the titanium oxide (T1O2) nanomaterials of rutile phase.

[00119] In the embodiment of the present invention, the saidTiCLnanomaterials are in form of nanowires, nono-flowers, and nanotubes.

EXPERIMENTAL ANALYSIS

[00120] In an experiment analysis of the present invention, Fig.5 represents Energy Dispersive X-Ray (EDX) analysis of obtained samples. The purity of the as-prepared amorphous titanium dioxide is shown by its energy-dispersive X-ray (EDX) spectrum ofthe SEM image, which gives 33.33% titanium and 66.67% oxygen atomic percentages, thus confirming the 1:2. stoichiometry of the compound.

[00121] Further, it shows the area of the image scanned as a square in pink color (a), the pattern of peaks (b), and a table showing the corresponding data. [00122] This is a clear indication for the formation of 100% pure titanium dioxide from natural ilmenite from the said process. This is the first report of obtaining 100% pure, phase- specific titanium dioxide nanorods from natural ilmenite. The data for the analysis is shown in table 1 below:

Table 1

[00123] Further, Fig. 6 represents powder X-ray diffractogrammes (XRD) of obtained samples. The diffractogramm with blue line represents the titanium dioxide amorphous product.

[00124] Referring to Fig. 6b, the P-XRD pattern is shown which represents the samples calcined at 350°C. The diffraction peaks appearing at 25.58°, 38.15°, 48.42°, and 55.02° correspond to the (101), (004), (200), and (211) diffractions of pure anatase phase of titanium dioxide (Joint Committee on Powder Diffraction Standards (JCPDS) Card No. 21-1272), respectively (refer Fig.6b).

[00125] As shown in Fig. 6c, the P-XRD pattern of the samples calcined at 650°C contains peaks at 27.45°, 36.16°, 41.26°, 54.40°, and 56.70°, respectively. These peaks correspond to diffractions from the (110), (101), (111), (211), and (220) planes of the pure rutile phase of titanium dioxide (JCPDS Card No. 29-1360).

[00126] The crystallinity calculated from the XRD peak areas shows that amorphous, anatase, and rutile phases have, respectively, 24%, 90%, and 98% crystallinity percentages. The crystallite sizes of the anatase and rutile phases, calculated using the Schemer’s equation, are 0.8 and 1.2nm, respectively.

[00127] Fig. 7 illustrates a graph representing Tauc plot of absorption data from the obtained T1O2 products. The plot clearly shows the decrease in indirect band gap to 3.15eV when crystalline the product by calcining at temperature of 1000°C from amorphous phase. Well crystalline product plot shows by T1O2 red line and amorphous product which before calcined product indicates by a-Ti02 black line.

[00128] Fig. 8 illustrates scanning electron microscopy (SEM) images of the obtained T1O2 samples. These images indicate that the as prepared sample has a flowerlike morphology (refer Fig. 8a). Further, the said sample is heat treated at 350°C to develop into a network of nanorods in the anatase phase (refer Fig. 8b).

[00129] Upon heat treatment at 650°C of the said sample, the rutile phase obtained has individual TiC^nanorods (refer Fig. 8c).

[00130] Figs. 9a & 9b illustrate scanning electron microscopy (SEM) images of the obtained T1O2 nanomaterials in form of nanowires.

[00131] Figs. 10a &10b illustrate scanning electron microscopy (SEM) images of the obtained T1O2 nanomaterials in form of nano-flowers.

[00132] Figs. 11a- lid illustrate scanning electron microscopy (SEM) images of the obtained T1O2 nanomaterials in form of nanorods. The diameters of anatase and rutile phase of nanorods are 32 and 67 nm, respectively, and ~350 nm long as calculated from the SEM images. Comparing these data with those obtained for the crystallite size from the XRD indicate that each nano-rod is composed of a large number of crystallites arranged in a rod like structure to form nanorods. [00133] Coming to Fig.12, there is shown a system (1000) for extracting titanium dioxide nanomaterials from natural ilmenite at moderate conditions, which will now be explained with reference to a block diagram.

[00134] The system (1000) includes a magnetic separator (16) adapted to purify the said ilmenite to obtain the pure ilmenite. The said magnetic separator (16) being operated with forward angle and side angle in range of 1-90° by applying voltage in range of 0-50 Volts and current in range of 0-10 Ampere in the said separator (16).

[00135] The system (1000) further includes a dry ball mill (18) adapted to mill pure ilmenite to obtain ilmenite particles or powdered ilmenite. The said ilmenite particles are sized to 50-200 micrometers.

[00136] The system (1000) further includes an apparatus (100). The said apparatus includes an autoclave (15) adapted to leach out iron from the said ilmenite particles powdered ilmenite by treating the said ilmenite particles with a first acid solution at predetermined hydrothermal conditions to obtain resultant residue particles in a closed rotary system of the said autoclave (15).

[00137] It will be appreciated by those skilled in the art that the autoclave (15) is adapted to provide a closed system for extracting the titanium oxide nanomaterials.

[00138] Referring to Figs. 2 & 3, the said autoclave (15) may include stainless a steel container (5), Teflon reaction vessel liner (6), a screw-fit Teflon lid (4), screw-fit stainless steel lid with Allen-key for leak-proof tightening (1), stainless steel weights (3) and springs (2).

[00139] In the said embodiment of the present invention, the said apparatus (100) includes an electric oven (12) housing the autoclave (15). Further, the apparatus (100) includes an autoclave holder (14) for fitting the autoclave (15) to the electric oven (12). Further, a rotational bar (7) connected to the electric oven (12) with a plurality of ball bearings (13) (refer Fig. 2). [00140] Furthermore, a rotating mechanism for rotating the said autoclave (15) may be provided. In an embodiment, the rotating mechanism may include a combination of belt system (9), sheave system (8) and gear motor (10) (refer Fig. 2).

[00141] In one embodiment of the present invention, the system (1000) includes a calcination device (19) adapted for heating the said mixture at 150°C to obtain amorphous titanium oxide (TiCF).

[00142] The said calcination device (19) is further adapted for the calcination of the said amorphous titanium oxide (T1O2) to obtain the titanium oxide (T1O2) nanomaterials of anatase phase and rutile phase.

Industrial Applicability of the present invention

[00143] Nano-crystalline titania (T1O2) has been intensively investigated due to its numerous applications in many fields such as electrode materials for solar cells, photo catalysts, wide band gap materials for gas sensing, pharmaceuticals, paints, and disinfectants. The most important application areas are paints and varnishes as well as paper and plastics, which account for about 80% of the world's titanium dioxide consumption.

[00144] Further, other pigment applications such as printing inks, fibers, rubber, cosmetic products and food account for another 8%. The rest is used in other applications, for instance the production of technical pure titanium, glass and glass ceramics, electrical ceramics, metal patinas, catalysts, electric conductors and chemical intermediates.

[00145] The main use of titanium dioxide (T1O2) is as a white powder pigment because of its brightness and very high refractive index. This means that relatively low levels of the pigment are required to achieve a white opaque coating. One of the major advantages for titanium dioxide is its resistance to discolouration under ultraviolet (UV) light in exposed applications. [00146] Further, the titanium dioxide (T1O2) is used in products such as paints and coatings, including glazes and enamels, plastics, paper, inks, fibers, foods, pharmaceuticals and cosmetics. In particular, high performance grades of T1O2 are finding a growing market in the cosmetics sector and most toothpastes use T1O2.

[00147] In addition, its Ultraviolet (UV) light resistance properties helps prevent the discolouration of plastics in sunlight. Sunscreens also use T1O2 as a blocker because of its high refractive index and the ability to protect the skin from UV light.

[00148] T1O2 is seeing growing demand in photo-catalysts due to its oxidative and hydrolysis properties. As a photo-catalyst, it may improve the efficiency of electrolytically splitting water into hydrogen and oxygen, and it may produce electricity in nanoparticle form. Applications include light-emitting diodes, liquid crystal displays (LCDs), and electrodes for plasma displays.

[00149] Under exposure to UV light, it becomes increasingly hydrophilic and can be used for anti-fogging coatings and self-cleaning windows. It also has disinfecting properties making it suitable for applications such as medical devices, food preparation surfaces, air conditioning filters and sanitary ware surfaces.

[00150] In mildly reducing atmospheres, T1O2 tends to lose oxygen and becomes a semiconductor. The electrical resistivity of the material can be correlated to the oxygen content of the atmosphere and hence it can be used as an oxygen sensor.

[00151] However, the major consuming industries of T1O2 are in the mature sectors in the developed world such as paints and coatings applications, paper and paperboard, and plastics. Therefore the consumption of T1O2 tends to follow general economic trends.

[00152] Global demand growth for T1O2 is estimated to average 2.7%/year in the 10 years to 2025, according to the UK consultant Artikol. Growth will be driven by China which is estimated to grow at 5%/year. A lot of potential is also seen in India in the next 10 years. Advantageous effects of the present invention

[00153] The present invention provides a process for extracting nanomaterials of titanium dioxide with 100 % purity at moderate conditions. The developed novel and low-cost process does not demand high temperatures but operates at much lower temperatures of less than 200 °C to convert ilmenite (such as Sri Lankan ilmenite) to pure titanium dioxide nanomaterials such as nanorods and nanoparticles.

[00154] Further, the present invention provides a closed hydrothermal system for carrying out the process, utilizing is revolving autoclave to maintain the desired pressure and temperature conditions within the closed system.

[00155] Therefore, the process and apparatus are adapted in such a manner that the autoclave of the present invention breaks the crystalline structure of hard inorganic solids at considerably lowers temperatures.

[00156] Furthermore, the autoclave provides a closed system for carrying out the present, which may prevent chemicals from escaping to the environment.

[00157] Therefore, the present invention provides a process which may be environmentally nonhazardous, and universally adaptable for the large-scale synthesis of the phase- specific pure titanium dioxide from natural ilmenite.

[00158] In addition, the process of the present invention provides a refluxing technique to remove impurities such as silica impurities.

[00159] In nutshell, the present invention provides a process and system for extracting titanium dioxide nanomaterials at moderate conditions, which is feasible, sustainable, effective, and efficient as compared to existing processes.

[00160] As such, the present invention provides a process that has many advantages over the conventional processes that are currently used. The process developed operates under much milder conditions than conventional process over a considerably reduced time scale and generates highly value-added nanomaterials rather than micrometer scale materials with specified dimensions of nanomaterials.

[00161] The improved process itself has a significant cost reduction while the materials generated also contribute many advantages as nanomaterials can be produced directly from our process without having to reduce size of micrometer size materials using either mechanical processes such as milling or using chemical processes.

[00162] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.

[00163] Further, the embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the present invention.