Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing element or inorganic compound except carbon dioxide
Patent
1989-04-14
1990-07-31
Lilling, Herbert J.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing element or inorganic compound except carbon dioxide
C12P 300
Patent
active
049450492
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for preparing magnetic powder and more particularly to a method for preparing uniform fine particles of magnetic powder utilizing an alkali-producing enzyme.
BACKGROUND OF THE INVENTION
A method which comprises adding a precipitant to a metal salt solution to form precipitates of a metal hydroxide has been used to prepare magnetic powder. However, when the precipitant is externary added to such a solution, the concentration of the precipitant in the solution becomes instantaneously and locally high and the resultant precipitates are likely to cause impurities uptake even if the concentration of the precipitant is low and it is added in small portions with stirring. On the contrary, use of a homogeneous precipitation method makes it possible to provide pure and compact precipitates. This homogeneous precipitation method is a method in which a precipitant is gradually produced in the solution by a chemical reaction such as hydrolysis. According to this method, the concentration of the precipitant is always maintained at an extremely low level since the produced precipitant is immediately consumed. As a result, the incorporation of impurities into the resultant precipitates and the amount of bound water are maintained at a low level because the precipitated particles slowly grow with time and precipitates of small volume is prepared.
Among the homogeneous precipitation methods, the most frequently used is an urea method in which a metal hydroxide or oxide is prepared utilizing a hydrolysis reaction of urea. The urea method is used to prepare a hydroxide or an oxide of iron.
However, it is found that the particle size of powder of such an oxide or the like prepared by the homogeneous precipitation method is large. Accordingly, an object of the present invention is to provide a method which is suitable to prepare magnetic powder consisting of a relatively small particles such as fine particles having an average particle size ranging from about 50 to 500 nm.
DISCLOSURE OF THE INVENTION
The present invention relates to a method for preparing at least one member selected from the group consisting of iron oxides, iron hydroxides and iron oxyhydroxides, which comprises a step of alkalizing a solution containing iron ions using an alkali-producing enzyme and a substrate thereof.
BRIEF EXPLANATION OF THE ACCOMPANYING DRAWINGS
FIGS. 1 and 3 to 7 are X-ray diffraction patterns and FIG. 2 is a photograph illustrating the particle structure of the product obtained in Example 1.
MOST PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION
The present invention will now be explained in detail.
In the method of the present invention, a solution containing iron ions is used. The solution contains either ferric or ferrous ions or both of these. The sources of these ferric and ferrous ions are not restricted to specific ones and specific examples thereof include chlorides, sulfates, nitrates, lactates, oxalates, fumalates, ammonium sulfates and ammonium oxalates of iron (including both ferric and ferrous salts).
In the method of the present invention, the aforementioned solution containing iron ions is alkalized with an alkali-producing enzyme and a substrate thereof.
The term "alkali-producing enzyme(s)" used herein means an enzyme capable of forming an alkali substance through a reaction with the substrate thereof and, for instance, hydrolases and oxidoreductases can be used. Further, the invention encompasses a method in which the solution containing iron ions is alkalized using a bacterial cell capable of producing an alkali-producing enzyme. Examples of hydrolases and substrates thereof which can be used in the invention are listed in Table I and oxidoreductases and substrates thereof are shown in Table II. In addition, bacteria which produce urease serving as an alkali-producing enzyme are exemplified in Table III and examples of other bacteria capable of producing an alkali-producing enzyme are shown in Table IV.
TABLE I ________________________
REFERENCES:
patent: 4385119 (1983-05-01), Blakemore et al.
patent: 4394451 (1983-02-01), Blakemore et al.
Hamaya Toru
Horikoshi Koki
Hamaya Toru
Horikoshi Koki
Lilling Herbert J.
Research Development Corporation
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