HU202899B - Process for producing iron-oxide pigment from red mud - Google Patents

Abstract

Iron-oxide pigments are prepd. from suitable ores, minerals, industrial byproducts and wastes. Starting materials are ground and brought into a previously acid washed, suspension. To this aq. salt soln. of alkaline earth metals, zinc, aluminium and iron are added and the pH is adjusted to 6.5-7.5. Pigment granules are surface treated to render them organophilic, are filtered, washed, and dried.

Description

BACKGROUND OF THE INVENTION The present invention relates to the production of pigment, filler and anticorrosion pigments containing iron oxide for use in the dyeing and plastics industries of the Bayer process.

The process involves adjusting the pH of the aqueous slurry of red mud, followed by ion-exchange surface treatment, filtration and hydrocyclone separation to provide pigments of valuable pigments with a predominantly iron oxide red content and other small amounts of heavy metal oxides up to 25 µm.

It is known that pigments containing iron oxide are used in considerable quantities in the plastics industry and in the manufacture of inks for corrosion protection and decorative purposes, as inorganic pigments with very good color fastness, opacity and heat resistance. Iron oxide pigments for dyeing purposes are synthesized from iron salts, in particular FeSO4, by synthetic means (U.S. Patents 4,129,454; 3,987,156; 4,153,472).

It is also known to produce high stability pigments starting from red mud. No. A158626 The process according to the Hungarian patent application relates to the stabilization of iron oxide red, chromium yellow and chromium green pigments. The stabilizing agent is essentially an aqueous solution containing Al, Ti, Si, Co, Cr, Be, Ga, Zr and Ni salts, or mixtures thereof. The stabilization solution is obtained from red mud formed as a by-product of the Bayer process by acid digestion and fractional dissolution. The red sludge is converted into water-soluble metal salts by acid digestion and separated into 3 fractions. In the first pass, the Al content of the Al slurry is dissolved out from the aqueous sludge with dilute hydrochloric acid,

The solution is later used to stabilize the iron oxide pigment. In the second stage, the slurry deprived of Al content is milled in a ball mill with 30% hydrochloric acid, whereby the iron oxide red content of the red sludge is completely converted to iron chloride. Iron chloride is further utilized as a starting material for conventional iron oxide red pigment production. In the third step, the remaining sludge is deoxidized with oxalic acid and then treated with perchloric acid to dissolve its TiO2, CO3O4, N1O2, Ζ1Ό2, Cr2O3, BeO and Ga2O3. The resulting solution is used to stabilize chromium pigments. The process does not extract dye pigment from red mud, but processes it on water-soluble Fe, Al, Ti, Zr, V, Co, Cr, Ni and Ga salts.

In contrast, the process described in the present application readily and efficiently retrieves the red sludge important iron oxide red pigment important in the dye and plastics industry, and the associated metal oxides with anti-corrosive properties without altering their chemical composition. The pigment thus obtained does not contain soluble sodium compounds or other corrosive ions, and is readily dispersible in paint binders and plastics. According to our investigations, the paint coatings, the waterproofing, the chemical resistance, the corrosion protection and the lifetime of these coatings are about one and a half times higher than those of the conventional preparations containing pigments.

The procedure we have corrected is implemented as follows:

The red mud to be processed in the Bayer process is slurried with water, preferably tap water, and homogenized at a dry matter content of 10-40% by weight. After further dilution, the suspension is adjusted to pH 5-7 with mineral acids (HCl, H2SO4, HNO3), a mixture thereof or milling broths. After settling and optionally diluting with water, this slurry is filtered through a suitable sieve system or screened with a hydrocyclone to separate the wastes and particles above 20-25. Subsequently, to the suspension of residual particles below 20-25 µm, water-soluble salts (chlorides, sulphates) of calcium, magnesium, barium, strontium, or iron, zinc, aluminum or their aqueous solutions are added, followed by addition of ammonia or alkaline hydroxide. 7.5-9) the hydroxides of the above metals are deposited on the surface of the iron oxide particles. The simultaneous addition of water-soluble alkaline phosphates, silicates or carbonates can be used to coat the iron oxide pigment particles with the appropriate phosphates, carbonates or mixtures thereof in the desired proportions instead of hydroxides. The ratio of the above hydroxide, phosphate, silicate or carbonate to iron oxide is 0.253% by weight. Subsequently, the pigment particles are surface-treated with aqueous solutions of ammonium or alkaline salts of C12-C18 monocarboxylic acids or of C5-C16 alcohols of phthalic acid, maleic acid with C5-C16 alcohols, in known manner.

Our process also allows the technology to be carried out in such a way that the red mud to be processed is not separated from the waste material after the acid opening, but is treated together with it and organophilized as described above, and then the air is separated from the iron oxide particles. The tail is at the bottom of the slurry and the organophilized fine particulate iron oxide concentrate is on the surface, which can be applied directly to the washer filter by decanting or decanting.

After surface treatment, the material so treated is filtered through a filter press, jig wash centrifuge, drum filter, etc. washed with water, preferably tap water, and finally rinsed with deionized water and dried at 105-110 ° C. The product thus obtained can be processed in the lacquer and plastics industry in a manner typical of advanced surface-treated pigments.

Examples

Example 1

Bayer obtained the procedure (3.51% TiO2, 0.015% NiO, 0.018% ZrO2, 0.25% Cr2O3, 0.18% Ga2O3 and 0.1 Containing 40% BeO) in red mud containing 70% solids by weight and 0.1-150 µm particle size in a blender with the addition of tap water or filtered running water, with stirring 40% solids-21

Slurry containing HU 202 899 Β is prepared. This homogenized slurry is further used as a starting material.

Weigh into a 10 liter cylindrical vessel: 2500 g of red mud slurry (1000 g of solids), 4000 g of tap water and then add vigorously with 5% sulfuric acid until pH 7 is reached.

The red mud slurry so treated after 1 hour of rest was passed through a 130 mesh screen or hydrocyclone to remove the granular and silicic acid particles above 25 µm.

780 g of a 10% solution of ZnSO4 are then added with vigorous stirring to the slurry so classified. The pH is 6.8.

After the addition of the zinc sulfate solution, stirring was continued for another five minutes, followed by the slow addition of 164 g of 10% ammonia solution and finally 500 g of aqueous 2% ammonium salt of stearic acid (heated to 60 ° C). while stirring. After complete addition, stirring is continued for another five minutes. Finally, the treated red mud is transferred to a filter, rinsed with tap water - finally deionized water - and dried at 105 ° C.

Example 2

To 2500 g of red slurry slurry (1000 g solids content) 4000 g of tap water is added and 5% sulfuric acid is added until pH 7 is reached. Screening on a 130 mesh screen. To the filtered slurry was added 750 g of 2.5% FeCl 2 solution with stirring, followed by 60 g of 10% ammonia solution. pH 7.6. After 10 minutes, a solution of 500 g of 2% myristic acid ammonium salt, heated at 60 ° C, was finally added to the aqueous solution. After stirring for an additional 10 minutes, it is filtered, washed (deionized) and dried at 105 ° C.

Example 3

In each case, the procedure of Example 1 was followed except that 20% Fe2 (SO4) 3 was added in small portions instead of 5% H2SO4 until the pH was 6.5. Screening on a 130 mesh screen. The pH of the filtered slurry was then adjusted to 7.4 with 10% ammonia.

Further, as in Example 1, an aqueous solution of 500 g of 2% palmitic acid sodium salt, preheated to 60 ° C, is added. It is finally washed with deionized water, filtered and dried.

Example 4

All proceed as in Example 2 but using 750 g of a 2.5% solution of FeCb instead of 750 g of a 3% solution of CaCb and replacing the solution of the ammonium salt of myristic acid with the same 2% solution of ammonium lauryl phthalate.

Example 5

All proceed as in Example 2 with the exception that 750 g of 2.5% FeCl 2 is replaced by 500 g of 2.5% MgCl 2 and 500 g of 2% myristic acid. Instead of a solution of its ammonium salt, 600 g of an aqueous solution of potassium salt of 2% ammonium octylhydrogen phthalate are taken.

Example 6

All proceed as in Example 1, except that 500 g of 5% aluminum sulfate solution is used instead of 780 g of 10% ZnSCU solution.

Example 7

Each was run as in Example 2 except that 750 g of 5% BaCb was used in place of 750 g of 2.5% FeCb.

Example 8

All proceed as in Example 2, except that an aqueous solution of 400 g of a 2% solution of the ammonium salt of 2% cetylmaleinate in 500 g of 2% myristic acid is added.

The pigment prepared as described in Example 1, as well as U.S. Pat. In the course of the application it is found that in the case of conventional iron oxide red inks, the material has to be passed through three times in a three-cylinder roller to achieve a particle size of 25 pm. To disperse the surface-treated pigment of the present process in an equal amount, it is sufficient to use only a quick mixer. The water uptake of the primer was tested according to MSZ 9640/12. The water absorption of the conventional pigment coating after 96 hours was 12 wt.% And the coating containing the pigment prepared according to our proposed process was 8.7 wt.%.

Claims (1)

A process for the preparation of iron oxide-based pigments for coloring, filling and corrosion protection of the red mud produced by the Bayer process for use in the paint and plastics industry, characterized in that the homogenized aqueous slurry of red mud with a dry solids content of 10-40% H2SO4, HCl or HNO3. respectively. a mixture of these, optionally roller pickle broth, to pH 5-7, removal of the sludge above 25 mm by filtration or hydrocyclone, and addition of an aqueous solution of the Fe, Zn, Mg, Ba or Al salts to the resulting red slurry, followed by alkali metal hydroxide or ammonia in aqueous solution; Half-esters of C12-C16 alcohols with aqueous solutions of ammonium or its alkaline salts such that EN 202 899 Β the organophilic coating on the pigments should be in the range of 0.1% to 2.5% by weight, finishing with washing of the iron-oxide pigment so treated, filtered and dried at 105-110 ° C or 10-40% by weight. The dry matter-containing red mud slurry is separated from the sludge above 25 μτη by air blowing after fractionation of the particle size below 25 pm, after surface treatment with hydroxide, phosphate and organophilization.