CS213670B1 - Method of preparation of the germ for crystallization of the direct coagulated ferrin red - Google Patents

Description

(54) A process for preparing a seed for directly precipitated-ferric red crystallization.

The invention relates to the field of the production of inorganic pigments and to a process for the preparation of pure microcrystalline hemattta, which is used as a seed for the crystallization of directly precipitated ferric red. The process is based on the alkaline precipitation of ferrous sulfate solutions, followed by oxidation of the resulting ferrous precipitate with air at a temperature of 0 to -50 ° C, and thermal recovery of the thus obtained pidoic acid to crystalline hemaaite. SUMMARY OF THE INVENTION The oxidation of the iron (II) precipitate is carried out after a 5 to 60 minute pre-mixing with a constant excess of an alkaline reagent such as ammonium or sodium hydroxide in an amount of 0.05 to 50 calculated on the precipitation reaction.

. 1,213,871 i

The present invention relates to a process for preparing a seed for the crystallization of directly precipitated ferric red by alkaline precipitation of ferrous sulfate solutions, followed by air oxidation of the resulting ferrous precipitate at a temperature of 0 to 50 ° C, and thermal dehydration of the thus obtained lepidocrokite to crystalline hernmett. .

Iron red can be produced by oxidative precipitation of ferrous sulphate solutions with air while adjusting the acidity of the reaction mixture to pH mm from i 3 and 6 with an alkaline reagent, for example ammonia, sodium hydroxide or metal iron. As a rule, these processes;

they lead - at temperatures of 90 to 95 ° C, when the oxidation proceeds sufficiently at a given pH - quickly. In such conditions, the precipitated solid phase contains, in addition to the desired red iron oxide (hemaatta), also yellow iron oxide (goethite), whose content significantly reduces to the watts of the resulting red pigment. To increase the selectivity of the clotting, an addition - the so-called embryo, which is the substance - is used. which particles act as the SMMS eryltalLzačaí center neg ICI ^ · the solid phase as \ nucleate red iron oxide are all less stable pouuívají _oxidhydro-: ferric alkoxides, except go ^^ ^ u thit neboliQC -FeOOH particular amrfi ^: s hydroxide (US pH. 2,620,261) or -FeOOH (NSR Pat. 2,249,274). The process is also carried out in two successive stages, where a primary precipitate formed by wild-crystallization from solution precipitates secondary to a pigment of suitable particle size (U.S. Pat. No. 2,716,595). ) · '

The most suitable embryo is the pure edge (OC-FegOá) with a roll and uniform size:

of particles. Such heroatt can not be prepared by precipitating the re ^ l ^ C ^ l, but it is necessary for this purpose, appropriate transformation reactions pouužt less stable alkyl ^FL Okatých železí.tých compounds.

Lepidecretion (3? -FeOOH) has also been used to prepare high phase purity heroat. However, under the conditions of preparation of reddish-red, lepidekmoкit undergoes simultaneous dehydration to hemmttt and transformation to geethite in 29 ferrous sulphate solutions (29, 1967). In order to obtain satisfactory results, i.e. to obtain pure OC FegOp, an intensive pressure hydrothermal treatment is used in this method of preparation of the embryo (cf. 178 615).

Systematic research has identified several important factors that find a decisive influence on the behavior of lepidoemokite in heated ferrous sulphate solutions, ie the manner in which it is converted to other iron oxides or oxides and oxides. It has been found that the ratio of β-oxide hydroxide, ω-iron oxide oxide and ε-iron oxide in the reaction mixture when heating the γ-FeOOH suspension in the ferrous sulfate solutions depends on the conditions under which the -FeOOH was obtained and how was then thermally or hydrothermally treated. It has also been found that the rate of conversion of -FeOOH toOC -FegOj is dependent on the concentration of Fe - * and SOj ions in the reaction environment. The discovery of this circumstance creates, among other things, the possibility of preparing germs of different sizes - the primary particles and thereby significantly affecting the particle size and hence the resulting red - in the main precipitation filter.

It is an object of the present invention to provide a seed for the erystallization of directly precipitated ferric red aluminum by precipitation of ferrous sulfate solutions, followed by air oxidation of the resulting ferrous precipitate at - 0 to 50 ° C and thermal dehydration of the thus obtained ltpidoemeeite to crystalline hernmatt. The essence of the invention is that

213 670 that the oxidation of the ferrous precipitate is carried out after a 5 to 60 minute premixing in the presence of a constant excess of an alkali reagent, for example ammonia or sodium hydroxide, in an amount of 0.05 to 50%, calculated on the stoichiometry of the precipitation reaction. The amount of hematite in the product increases when a ferrous precipitate is added prior to oxidation. to the reaction mixture of lepidokite in the range of 1 to 50%. for the clot mass. . It is preferred that the oxidation of the precipitate is carried out at a rate of 5 to 35 g Pe / liter / hour. The phase purity of the resulting product can be further influenced to a large extent by thermally treating the obtained product prior to conversion to embryo by heating to 120 to 200 ° C in air or by heating in suspension / water or aqueous solution. sodium sulphate and / or ammonium sulphate or magnesium sulphate having 0.1 to 3 molar / liter sulphate ends at a temperature of from 95 ° C to the boiling point of the system at normal pressure. LdpieokгokCi is then converted to. the seed is a solution of ferrous sulphate having a concentration of preferably 0.05 to 2 moles of sulphate per liter.

i The present invention is based on the recognition that the behavior ldpieokrokiiu, získaného've (two-stage direct exidací precipitate ferrous hydroxide (specifically called. green growth 2+ 3+ 2 ^O, ^ Z ^ i r ^h of ^{UBA Fe} _Q> ⁴ · · ^(° H) ² · ^(S ° ²⁾ 0, ¹ · 5. ^ ³ OH · H η ²⁰⁾ according to equations ·

FeSO 4 + 2 MOH ------- = ► Fe (OH). . . M _o S0,

2 2 ₉

Fe (0O) ₂ + 0 ₂ ------- »4.-FoOOH. The 2 'O 2 O, where M is an alkali metal or ammonium, depends heavily on its preparation conditions when heated in ferrous sulfate solutions.

The ratio of O-Fe? ³ : OC-FeOOO in the product of such conversion is highest when the bleach step is prepared such that the oxidation of the ferrous precipitate is conducted with a constant excess of the reagent ranging from 0.5 to 50% per flow / iomedtii clotting reaction. | The OC-Fe2O: OCFeo2O0 ratio in the product is further increased when iron (III) -oxia / yogoxia precipitate (β-pido) is added to the reaction mixture prior to the oxidation of ferrous iron in an amount of 1-50%. for the clot mass.

The phase purity and particle size of the pidoocyanate can be varied by the rate of oxidation of the precipitate. A too high speed can lead to goedh / t, too little exidation can also provide mmanneite (Fe ^ o). A reaction course was found to be optimal, in which the charge in 1 liter of the reaction mixture oxidized 5 to 35 g of Fe per hour.

The thus prepared compound is converted to pure, micrococcyte in solutions of ferrous sulphate under the aforementioned conditions, if previously thermally or optionally. hyйгotdrmicC / modified. Such treatment may be heating to 120 to 200 ° C for 1 to 6 hours, or heating in aqueous suspension or suspension in ammonium sulfate, sodium, r 'solution.

% of magnesium sulphate having a total sulphate concentration of 0.1-3 moles / liter to a temperature of from 95 DEG C. to the boiling point of the system for 1 to 10 hours.

The rate of conversion of the thus prepared idoocyanate to the nucleus, and hence the seed particle size, can be controlled at a constant temperature by selecting the concentration of the iron sulphate solution in which the conversion is carried out. A suitable concentration range of the solution solution is from 0.05 to 2 moles of FeSO 2 per liter.

213 670

The process according to the invention yields very pure microcrystalline hematite of a preselected uniform particle size, which is suitable for ingestion as a seed for the production of precipitated ferric red. The process according to the invention avoids the use of higher pressures and therefore does not impose great demands on the device. The resulting product guarantees - reproducible production of reds - with a very low content of foreign phases.

The invention is further elucidated by a few examples of embodiments thereof, which are not intended to limit the scope of the invention.

Example 1

In a 2 liter vessel, 1 mol (88.5 g) of lzpidoCrokit was prepared from 1 µL of ferrous sulphate by concen- tration * 1 molar / ltr, by first adding 2.1 with cooling at 10 to 20 ° C mole of ammonia in the form of a 25% aqueous solution (105% stechiomeerre), and after stirring for 30 minutes, the precipitate was oxidized with air at a rate of 5 to 10 g Fe / liter. The orange was then washed, dried and heated in an oven at 120 ° C for 10 hours. Upon conversion in 0.1 molar galsy sulfate solution at 95 [deg.] C., pure hernaat with a specific surface area of 38 m < 2 > after 2 hours of heating.

Example 2

Part 1 of the preparation described in Example 1 was converted to. heimait at 95 µm in 2 M solution. ferrous sulphate and after heating for 10 minutes, a product of composition ? ’

OC 2 -FeO 2 and a specific surface area of 50 µg. Example 3 i

In a 2 liter container. was from 1 liter of ferrous sulphate solution. After the addition of 3 moles of ammonia (150% stzihtoaeZriz), a green precipitate was obtained which was oxidized in the mother liquor with air at a rate of 30-35 g Fe / ltr.hr at a temperature of 20-25 ° C. The orange product obtained was then washed and heated in a neutral solution containing 1.88 * mole of ammonium sulfate and 0.12 mole of magnesium sulfate in 1 liter * to boiling for 10 hours. After converting the product to hematide at 95 ° C and 0.1 molar iron (II) sulphate solution, 78.5 g of haemite having a specific surface area of 52 m * 1g was obtained.

Example - 4

The lipococci prepared as in Example 3 was heated in an oven at 200 ° C for 1 hour. After conversion to a method as in Example 3, a product with a surface specificity of 87 m-1g was obtained.

Claims (5)

OF THE INVENTION A process for preparing a seed for the crystallization of directly precipitated iron by red alkali precipitation of ferrous sulphate solutions, followed by air oxidation of the resulting iron precipitate at a temperature of 0 to -50 ° C and the dehydration of the thus obtained product to crystalline. 5. The method according to claim 1, characterized in that the oxidation of the iron precipitate is carried out after Pre-mixing in the presence of a constant excess of another reagent, such as ammonia or sodium hydroxide, in an amount of 0.05 to 50%, calculated on the amount of the precipitation reaction. 2. Process according to claim 1, characterized in that before the oxidation of the precipitate, a lepidocrokite is added to the reaction mixture in an amount of 1 to 50% by weight of the precipitate. 3. A process according to claim 1, wherein the oxidation of the precipitate is carried out at a rate of 5 to 35 g. 4. The method according to claim 1, 2 or 3, characterized in that the resulting lepidocrokite is thermally treated by heating to 120 to 200 [deg.] C. in air or by heating in suspension in water or an aqueous solution of sodium or ammonium sulphate or sulphate prior to conversion. magnesium with a total sulphate concentration of 0,1 to 3 moles per liter, at a temperature of 95 ° C and at a boiling point of the system at normal pressure. 5. The process of claim 1, wherein the lepidocrokite is converted to a hematite seed in a solution in the range of 0.05 to 2 moles of ferrous sulfate per liter.