CLIAMS:WE CLAIM

1. A process for the maximum recovery of Iron from blue dust where in blue dust treated in 1:3ratio of nitrohydrochloric acid with 1:3 solid liquid ratios to dissolved at 100? with continuous staring for 4 hrs.
2. A process claimed in 1 where in blue dust generated during mining of iron ore at NMDC Ltd mines and blue dust was taken for primary reduction in a rotator furnace at 800? for 6 hrs before dissolution in acid.
3. The process claimed in 1, wherein the digested liquid is diluted in distilled water up 5%.
4. A process claimed in1 wherein the dissolved sample (Ferric chloride) has precipitated at 10.5pH under vigorous stairing with adding of 10% NaOH solution at the rate of 0.01ml/ sec.
5. A process claimed in 4, wherein the precipitated ferric hydroxide was washed with distilled water till sodium and chloride ion free.
6. A process claimed in 5, wherein the precipitated ferric hydroxide was again taken for secondary reduction at 400? in rotary furnace for 4 hrs with hydrogen gas under rotation state.
7. The Process claimed in 6, wherein the metal iron has taken for adsorption of nitrogen gas.
8. The process claimed in 7, where in the metal iron powder has grounded in planetary ball mill for 6 hrs with 400 rpm under inert gas atmosphere.
9. The process claimed in 8, wherein metal iron powder again adsorbed by nitrogen gas.
10. The process claimed in 9, wherein metal iron powder kept in an air sealed glass jar.
,TagSPECI:THE PATENTS ACT-1970
(39 of 1970)

COMPLETE SPECIFICATION
(See Section 10)

A process for Nanostructure Iron Powder from Blue Dust

National Mineral Development Corporation Ltd. Khanij Bhavan, Catell Hill, Masabtank, Hyderabad, A public Enterprises ( Gov. Of India), Hyderabad, Andhara Pradesh, India.

The following specifications particularly describe the nature of the invention and the manner in which it is to be performed.
The present invention relates to a process for the preparation of nanostructure Iron powder from blue dust more particularly it is related to the production of nano size pure iron.

FIELD OF THE INVENTION

During the operation of our (NMDC Ltd) iron ore mine huge fines generated at their site, due to its blue color this fines are called blue dust. After beneficiation of concentrated blue dust, it is coming two type i.e. Grade –I & Grade – III, the average particle size is 45 and 76 respectively, irregular shape with high surface area with 67% Fe and around 3% of silica.
Blue dust is rich in iron but it is not suitable feed for blast furnaces, so for there is an opportunity to develop iron base value added products. Therefore, efforts were made to prepare value-added products. The value addition of nanostructure iron powder will not make only mining more economical but this will make it environment friendly and better utilization of such type of fines.
In the process of invention, the blue dust concentrate was activated at 800? for 6 hrs under hydrogen gas atmosphere. The activated blue dust has been dissolved in Nitro hydrochloric acid at100 - 105?? for 4hrs the solid was separated by filtration after filtration silica solid obtained. The precipitation of ferricchloride was done by 10 % sodium hydroxide solution under vigorous staring condition to avoid nucleation at 10-.5 pH; precipitate was separated by vacuum filter pump. The solid ferric hydroxide was washed with de - mineralized distilled water until free from chloride and sodium ions. Washed ferric hydroxide was dried in air oven at 120 ? and broken up agglomerated hydroxide then solid was taken for reduction under hydrogen gas at 400? for 4hrs after that passivated with nitrogen mixed air. The iron metal grounded in planetary ball mill under argon gas. The solid nano iron powder was confirmed by XRD and SEM.
BACGROUN OF THE INVENTION:
The nano iron oxides have been synthesized by almost all the known wet chemical methods which include precipitation at ambient/elevated temperatures, surfactant mediation, emulsion/micro-emulsion, electro-deposition etc. The precipitation technique is probably the simplest and most efficient chemical pathway to obtain iron oxide particles. Iron oxides (FeOOH, Fe3O4 or Fe2O3) are usually prepared by addition of alkali to iron salt solutions and keeping the suspensions for ageing. The main advantage of the precipitation process is that a large amount of nano particles can be synthesized. However, the control of particle size distribution is limited, because only kinetic factors are controlling the growth of the crystal. In the precipitation process, two stages are involved i.e., a short burst of nucleation occurs when the concentration of the species reaches critical super saturation, and then, there is a slow growth of the nuclei by diffusion of the solutes to the surface of the crystal. To produce mono disperse iron oxide nano particles, these two stages should be separated; i.e., nucleation should be avoided during the period of growth . Size control of mono dispersed particles must normally be performed during the very short nucleation period, because the final particle number is determined by the end of the nucleation and it does not change during particle growth. A wide variety of factors can be adjusted in the synthesis of iron oxide nanoparticles to control size, magnetic characteristics, or surface properties. A number of studies have dealt with the influence of these different factors. The size and shape of the nano particles can be tailored with relative success by adjusting pH, ionic strength, temperature, nature of the salts (per - chlorates, chlorides, sulfates, and nitrates), or the Fe(II/Fe(III) concentration ratio.
DISCLOSURE OF THE INVENTION
The main object of the present invention is to use blue dust as a source of Iron for the preparation of Nano iron powder.
Another object of the present invention is to prepare nano iron powder employing an energy efficient process which obviates the drawbacks as detailed above.
Yet another object of the present invention is to provide a process for preparing pure iron metal powder as a value added product from blue dust generated during mining.
Yet another object of the present invention is to provide a process for preparation of nanostructure iron powder from blue dust.

SUMARY OF THE INVENTION

A known weight of concentrated (Grade 1) blue dust sample was taken in a rotary reduction furnace for primary reduction of sample at 800? under hydrogen gas atmosphere with rotating condition for 6 hrs. Activated blue dust sample was cooled with nitrogen gas and sample was taken up for dissolution in1:3 nitro - hydrochloric acid under staring condition at 100? temperature for 4 hrs, the dissolved leach liquor was filter under vacuum filter to separate silica. The ferric chloride solution was taken up for precipitation with 10% NaOH solution up to 10.5pH under vigorous staring, then ferric hydroxide was dried in air oven at 120 ? to remove moisture from ferric hydroxide. The dried sample was grounded to break agglomerate and taken in to rotary reduction furnace for secondary reduction at 400? under hydrogen gas atmosphere for 4hrs, after reduction sample was passivate with nitrogen gas. The sample was taken out from rotary furnace and grounded in planetary ball mill at 400 rpm for 6 hrs under inert gas atmosphere.

DISCRIPTION OF THE INVENTION

The present invention provides a process for utilization of waste which will generated at the time of mining. The raw material blue dust is itself containing 67% Fe2O3 with high surface area.
The present nano iron oxides have been synthesized by almost all the known wet chemical methods which include precipitation at ambient temperatures. In this precipitation technique probably the simplest and most efficient chemical pathway has been implemented to obtain iron oxide particles. This Iron oxides (FeOOH, Fe3O4 or Fe2O3) was prepared by addition of alkali to iron salt solutions under vigorous staring condition. In this process we can synthesize large amount of nano size particles.

ANALYSIS OF NANO IRON POWDER

The product nano Iron powders were analyzed by X- ray diffraction, Specific area (BET) and SEM.

Example 1
300 gram concentrated (Grade 1) blue dust sample was taken in a rotary reduction furnace for primary reduction of sample at 800? in presence of hydrogen gas atmosphere under rotating condition for 6 hrs. This activated blue dust sample was cooled with nitrogen gas and sample was taken out for dissolution in1:3 nitro hydrochloric acid with 1:3 solid liquid ration i. e. 225 ml Nitric acid and 675ml hydrochloric acid at 100? for 4 hrs. The dissolved leach liquor was filter under vacuum filter to separate silica. The ferric chloride solution was diluted up to 5% and taken for precipitation with 10% NaOH solution up to 10.5pH under vigorous staring condition, then dark red brown ferric hydroxide was taken up for filtration in a vacuum filter, hydroxide precipitate was washed with distilled water till free from sodium and chloride ion. The sample was dried in air oven at 120 ? to remove moisture from ferric hydroxide the sample was weighed. The dried 270 gram sample was manually grounded to break the agglomeration of sample and taken in to rotary reduction furnace for secondary reduction at 400? under hydrogen gas atmosphere for 4hrs, after reduction sample was passivate with nitrogen gas. The sample was taken out from rotary furnace and grounded in planetary ball mill at 400 rpm for 6 hrs under inert gas atmosphere, after cooling sample was taken for analysis.

Example 2
500 gram weight of concentrated (Grade 1) blue dust sample was taken in a rotary reduction furnace for primary reduction of sample at 800? under hydrogen gas atmosphere with rotating condition for 6 hrs. This activated blue dust sample was cooled with nitrogen gas and sample was taken out for dissolution in1:3 nitro hydrochloric acid with 1:3 solid liquid ration i. e. 500 ml Nitric acid and 1500 ml hydrochloric acid at 100? for 4 hrs. The dissolved leach liquor was filter under vacuum filter to separate silica. The ferric chloride solution was diluted up to 5% and taken for precipitation with 10% NaOH solution up to 10.5pH under vigorous staring, then dark red brown ferric hydroxide was taken up for filtration in a vacuum filter, hydroxide filtrate was washed with distilled water till free from sodium and chloride ion.The sample was dried in air oven at 120 ? to remove moisture from ferric hydroxide the sample was weighed. The dried 450 garm sample was grounded to break the agglomerate and taken in to rotary reduction furnace for secondary reduction at 400? under hydrogen gas atmosphere for 4hrs, after reduction sample was passivated with nitrogen gas. The sample was taken out from rotary furnace and grounded in planetary ball mill at 400 rpm for 6 hrs under inert gas atmosphere, after cooling sample was taken for analysis.
X-Ray diffraction pattern showed that product obtained is Iron powder and shown in FIG.1. SEM photo of the nano powder is in fig 2 shows the shape of the particles is spherical. Specific area (BET) and calculated from its data average size of particles are presented in Tab. 1, average particle size calculated from BET data was 82