Title of Invention

"AN IMPROVED PROCESS FOR THE SYNTHESIS OF FERROSOFERRIC OXIDE (FE3 O4)."

Abstract

This invention relates to an improved process for the preparation of ferrosoferric oxide (Fe304). Fe3O4 is obtained at room temperature by the process to the present invention and is of cubic crystalline structure. Ferrosoferric oxide is widely used as the catalyst for ammonia synthesis, preparation of various ferrites as well as for diagnostics & therapeutic use which involves magnetic drug targeting for destruction of tumors and stimulation of immuno function. The prior art processes uses either higher temperature or a combination of two or more than two compounds of iron, divalent metal salts or organic complexes to precipitate corresponding hydroxides/oxides. Where as the improved process given under this invention uses only one simple salt of iron at a time to obtain ferrosoferric oxide at room temperature. Hence, the present method is very simple and straightforward and gives ferrosoferric oxide directly at room temperature.

Full Text

This invention relates to an improved process for the preparation of ferrosoferric oxide (Fe3O4) More particularly Fe3O4 is obtained at room temperature by the process of the present invention and is of cubic crystalline structure. Ferrosoferric oxide is widely used as the catalyst for ammonia synthesis, preparation of various ferrites as well as for diagnostics & thereupatic use which involves magnetic drug targetting for destruction of tumors and stimulation of immuno function. Ferrosoferric oxide is conventionally prepared starting from FeSO4.7H2O and sodium hydroxide. FeSO4.7H2O is dissolved in water. Sodium hydroxide solution and ferrous sulphate solutions are mixed and agitated to provide new surface of the mixture exposed to the atmosphere. At the same time FeS04.7H2O and scrap iron are agitated in enough quantity of water at 60°C which form a green mass. This is added to the above material and air is bubbled through the resulting mass at 60°c. A chemical analysis shows Fe2O3.H2O product showing 86% Fe2O3 and 12% H2O. This is further filtered, washed and dried at 100°C. Filter cake is crushed and hydrogen is passed through the crushed material at 399°C. The amount of water vapour released in large volume drops of substantially giving a black coloured powder of chemical formula Fe304. There are various processes, other than the one mentioned above, given in the literature for the preparation of ferrosoferric oxide starting from α-Fe2O3 α-FeO(OH) with a solution of phosphoric acid ester, drying at 100°C & reducing to Fe3O4 in H2 atmosphere at 380 to 500°C (Ger. Patent 2, 520,643 dt. 18th NOV 1976) or from ß-FeO(OH) containing C1>1% by heating in reducing gas at around 250 to 300°C in a dry hydrogen or at 400°C in hydrogen saturated with H2O (Japan patent 77 10, 897 dt. 27th Jan 1977) or from acicular geothite (a-FeO(OH) to Fe3O4 at 300 to 700°C (JP. Patent 05,335, 126 [93,335,126] (Cl.HO.IF/11), 17th Dec. 1993) or by microemulsion technique by using Fed 2 & FeCls mixture and the ammonia solution (Taehan Kumsok. Hakhoechi, 1993, 31 (11) 1367-73 (Korean)) or from a mixture of ferrous chloride and ferric chloride (Kang Y.S.; Risband S., Rabold, J.F, Strove F., chem. Mater. 1996, 8,2209). The above mentioned processes have the following disadvantages. In these processes either higher temperature or a combination of two or more than two compounds of iron, divalent metal salts or organic complexes are used to precipitate corresponding hydroxides/oxides. Where as the improved process given under this invention uses only one simple salt of iron at a time to obtain ferrosoferric oxide at room temperature. Hence, the present method is very simple and straightforward and gives ferrosoferric oxide directly at room temperature. Accordingly, the present invention provides an improved process for the synthesis of ferrosoferric oxide (Fes04) which comprises,; adding drop wise 50 to 99% hydrazine hydrate to aqueous solution of iron salts such as sulphate, chloride and nitrate at pH 7 to 10 at room temperature till the black precipitate of Fe3O4 is obtained, optionally heating the precipitate upto 80°C, recovering the said Fe3O4 by conventional method. In one of the embodiment of the present invention iron salts such as ferric/ferrous sulphate, chloride and nitrates may be used with a concentration of 0.01 M to 5 M. In another embodiment of the present invention 50 to 99% aqueous hydrazine hydrate may be used . In still another embodiment precipitate of Fe3O4 may be washed with hot water to remove anions, hydrazine hydrate followed by sun drying or vacuum drying to recover ferrosoferric oxide (Fe3O4). In still another embodiment addition of hydrazine hydrate is carried out at pH between 7 to 10. The process of the present invention involves the following steps: Ferric chloride anhydrous is dissolved in distilled or deionised water with a concentration 0.01 M to 5 M. Hydrazine hydrate is diluted to various required percentages varying from 50 to 99%. Hydrazine hydrate solution is added to ferric chloride, solution drop by drop. The mixture is stirred continously with a mechanical stirrer to mix hydrazine hydrate uniformly in the solution. Required amount of hydrazine hydrate is added to get the pH from 7 to 10. Pure jet black precipitate of Fe3O4 is observed in the solution. Solution is filtered and washed with hot water to remove chloride/sulphate ions and excess hydrazine hydrate. Precipitate is dried under vacuum or sun dried. Approximately 92 to 96% yeild was obtained by this method. Jet black powder is obtained which is characterized by XRD, moessbauer spectroscopy, IR and magnetic measurements indicating the formation of ferrosoferric oxide. The above procedure was used to prepare ferrosoferric oxide with ferrous chloride, ferrous sulphate and ferric sulphate solution with above mentioned concentration. XRD studies indicated the total formation of FesO4 with particle sizes of 10 to 20 nm with different concentrations of salt solutions and hydrazine hydrate with different dilutions. The process of this invention is illustrated by the following examples. However, this should not limit the scope of the invention. EXAMPLE : 1 A solution of 0.5 M concentration of FeCl3 solution was prepared by dissolving 21.02g of anhydrous FeCl3 in 260 ml of distilled water. 80% Hydrazine hydrate was prepared by diluting 99% of hydrazine hydrate. Approximately 35 ml of 80% of hydrazine hydrate was added drop by drop to the above FeCl3 solution. The solution was stirred contineously by a mechanical stirrer till 80% hydrazine hydrate is added completely. Black precipitate of Fe3O4 is formed during addition. The said solution was filtered through Whatman filter paper No. 42. The precipitate was washed thoroughly with hot water number of times for the total removal of chloride ions and excess hydrazine hydrate. The precipitate is dried in vacuum dessicator at room temperature. Roughly 96 to 98% product yield is obtained by this method. XRD indicated only the presence of ferrosoferric oxide. Particle size was of the order of 14.5 nm. IR & moessbauer spectra confirmed the formation of Fe3O4 Saturation magnetization determined by oscillation pendulum method gave the value of 78Gausscm3/g at room temperature (~30°c). The value is slightly less compared to the literature value due to the very fine particle size of the ferrosoferric oxide. EXAMPLE: 2 A solution of 2 M concentration of FeCl2 solution was prepared by dissolving 12.9g of FeCl2 in 32.4 ml of distilled water. 80% Hydrazine hydrate was prepared by diluting 99% of hydrazine hydrate. Approximately 8 ml of 80% of hydrazine hydrate added drop by drop to the above FeCl2 solution. The solution was stirred contineously by a mechanical stirrer till 80% hydrazine hydrate is added completely. Black precipitate of Fe3O4 is formed during addition. The said solution was filtered through filter paper. The precipitate was washed thoroughly with hot water number of times for the total removal of chloride ions and excess hydrazine hydrate. The precipitate is sun dried in petri dish. Roughly 85% product yield is obtained by this method. XRD indicated only the presence of ferrosoferric oxide. Particle size was of the order of 10.6 nm. IR & moessbauer spectra confirmed the formation of Fe3O4. Saturation magnetization determined by oscillation pendulum method gave the value of 72Gausscm3/g at room temperature (~30°c). The value is slightly less compared to the literature value due to the very fine particle size of the ferrosoferric oxide. EXAMPLE : 3 A solution of 1.0 M of Fe2(S04)3.6H2O was prepared by dissolving 42.49g of Fe2(SO4)3.6H2O in 85 ml of distilled water. 80% Hydrazine hydrate was prepared by diluting 99% of hydrazine hydrate. Approximately 28 ml of 80% of hydrazine hydrate was added drop by drop to the above solution. The solution was stirred contineously by a mechanical stirrer till 80% hydrazine hydrate is added completely. Black precipitate of Fe3O4 is formed during addition. The said solution was filtered through filter paper. The precipitate was washed thoroughly with hot water number of times for the total removal of sulphate ions and excess hydrazine hydrate. The precipitate is dried in vacuum dessicator at room temperature. XRD indicated only the presence of ferrosoferric oxide. Particle size was of the order of 17nm. IR & moessbauer spectra confirmed the formation of Fe3O4 Saturation magnetization determined by oscillation pendulum method gave the value of 67Gausscm3/g at room temperature (~30°c). The value is slightly less compared to the literature value due to the very fine particle size of the ferrosoferric oxide. Thus the improved process given under this invention has the following advantages. 1. Hydrogen gas and high temperature which is essentially required for reduction is totally eliminated. 2. Synthesis of Fe3O4 is carried out at room temperature making the process economical and environment friendly. 3. Steps required in the other methods are reduced to minimum in the improved process. 4. For the first time hydrazine hydrate has been used for the preparation of Fe3O4 from iron salts. We Claim: 1. An improved process for the synthesis of ferrosoferric oxide (Fe3O4) which comprises,; adding drop wise 50 to 99% hydrazine hydrate to aqueous solution of iron salts such as sulphate, chloride and nitrate at pH 7 to 10 at room temperature till the black precipitate of Fe3O4 is obtained, optionally heating the precipitate upto 80°C, recovering the said FeSO4 by conventional method. 2. An improved process as claimed in claim- 1 wherein iron salts such as ferric/ferrous sulphate, chloride & nitrates are used in the concentration ranging from 0.01 to 5M. 3. An improved process for the synthesis of ferrosoferric oxide (Fe3O4) substantially as herein described with reference to the examples.

Documents:

59-del-1999-abstract.pdf

59-del-1999-claims.pdf

59-del-1999-correspondence-others.pdf

59-del-1999-correspondence-po.pdf

59-del-1999-description (complete).pdf

59-del-1999-form-1.pdf

59-del-1999-form-19.pdf

59-del-1999-form-2.pdf