CZ27025U1 - Orange inorganic pigment based on red sludge - Google Patents

Abstract

In the present invention, there is disclosed a process for treating red sludge being a waste after the treatment of bauxite and orange inorganic pigment prepared by this process. The invented process comprises the following steps of: dewatering, preliminary adjustment of grain size distribution parameters and that of pH value, a first calcining at temperature in the range of 600 to 950 degC, bacterial leaching with the Acidothiobacillus ferrooxidans culture, filtration, washing with water, a second calcining at a temperature in the range of 600 to 950 degC, washing with water, drying and grinding. The so prepared pigment is of orange color and can be used in coating compositions and when renovating mural wall paintings and graffiti. In the present invention, there are also described renovation mixtures containing thereof.

Description

The present invention relates to an orange inorganic pigment prepared by treating red sludge from industrial waste resulting from bauxite processing.

BACKGROUND OF THE INVENTION

The processing of bauxite ore produces a by-product called 'red sludge'. Hand in hand with the processing of bauxite is also an effort to use red sludge, which is otherwise a hazardous waste. One of the valuable products that can be obtained from red sludge is also ferric pigments. Due to the fact that the type and composition of bauxite ore varies significantly in nature, the composition of waste red sludge is also very variable and thanks to that the prepared pigments differ in color, saturation and resulting chemical composition, which are also the main characteristics for their subsequent use.

The simplest processing methods for the preparation of pigments include only pH adjustment and drying and grinding, optionally crystallization. For example, JPH 05-139727, CN 101077793. In some cases, the preparation process is subject to obtaining the other valuable products mentioned above, eg FR 2 697 178 and GR 2009/0100008 or also to the generation of waste-free technology such as HU 209 326. the magnetic properties of the product are also used in some processes, eg in GB 2,078,211.

More advanced methods also include calcination, e.g., FR 2,688,796, CN 102584339 and RU 2,346,018, but only one. However, multi-stage calcination is not described in the preparation of red sludge pigments.

In addition to calcination, state-of-the-art processes also use microorganisms. E.g. SK 46698 is used to leach the metabolic products of microorganisms of the Deuteromyces group.

The essence of the technical solution

The essence of the solution is bacterial leaching using bacteria that survive even at extremely low pH, the so-called acidophils and perform double calcination.

The process includes the following steps:

- drainage, pre-treatment of grain parameters and optionally pH,

- calcination,

- bacterial leaching,

- filtration, washing,

- second calcination,

- washing, drying,

- grinding.

For the purpose of this solution, red sludge from Birač Alumina Industry, Zvomik, Bosnia was used as feedstock. It was taken from a cross-section in the waste, effluent run-off in the final settling tank (multiphase waste). It is a repeatedly washed suspension with a density of 1.2 to 1.3 kg / m ³ , dry matter concentration from 250 to 350 g / l.

The input red sludge was subjected to chemical analysis to determine the content of individual elements and loss of annealing. The results of the analysis are summarized in Table 1:

-1 CZ 27025 Ul

Element Content [% by weight] On 8.6 Mg <0.3 AI 5.9 Si 4.2 P 0.135 WITH 0,085 TO 0,079 Ca 1.95 Ti 2.7 Mn 0.138 Fe 35.9 Cr 0,072 Ni 0,078 Zn 0,035 Ce 0,086 Pb 0,022 Loss on ignition 7.9

Table 1: Red sludge composition

The table above shows that this red sludge is rich in iron and thus suitable for the production of ferric pigment. Its color can be increased by calcination in the temperature range of 600 to 950 ° C. Calcination (roasting) leads to oxidation of iron, manganese and sulphide. The color enhancement is further enhanced by the subsequent bacterial leaching process. The samples are calcined (roasted) before and after bacterial leaching.

The bacterial leaching process takes place in air-lift bioreactors. 9K medium without FeSO ₄ is used for culture. As a bacterial culture, a culture of the genus Thiobacillus, preferably Acidithiobacillus ferrooxidans is used.

Examples of technical solutions

Example 1

A sample of red sludge was taken from a cross-section in a waste mash draining in a final settling tank in a natural landfill - open field. The sample suspension was allowed to settle and after the liquid phase was poured, the solid was subsequently dried at 105 ° C for 24 hours.

First, the sample is ground to 100% below 0.063 mm and the pH is adjusted by washing with distilled water followed by 1 mol / l sulfuric acid. Next, the sample is calcined at 650 ° C for 2 hours. Subsequently, the sample is subjected to bacterial leaching in an air-lift bioreactor where 70 l of culture medium at pH 3.0 to 3.6 are used per 5 kg of sample and the composition:

-2GB 27025 U1

Component Amount (NH 4) ₂ SO ₄ 3,00 g KC1 0,10 g K ₂ HPO ₄ 0.50 g MgSO ₄ .7H ₂ O 0.50 g Ca _{(NO3) 2} 0.01 g H ₂ SO ₄ 1 ml 5 mol / l

Table 2: Culture medium composition

The resulting suspension is then stirred and homogenized for one hour. Then, 10 L of pure bacterial culture of Acidithiobacillus ferrooxidans in distilled water is added, where the bacterial concentration is 10 ⁷ per ml of bacterial solution. Mixing and aeration of the suspension is ensured by connecting the air-lift bioreactor to the aeration pump. The leaching time is 4 weeks and the temperature is maintained at 25 ° C and pH at an optimum value of 1.8 to 2.2 at all times. 10N H ₂ SO ₄ is used to adjust the pH. After bacterial leaching, the representative samples were counted for the amount of bacteria by the MPN method. The suspension is filtered and the filter cake is washed with distilled water to pH 5.0. The samples are then dried at 60 ° C and then calcined (roasted) for 2 h at 650 ° C. The calcination product is washed with distilled water and, after removal of the water-soluble substances, dried and ground in a ball mill to a particle size of 50 to 70 µm. A sample of the prepared pigment is further milled on a jet mill to a particle size below 30 µm. In order to achieve an optimum grain size corresponding to the pigments currently available on the market, the sample is subjected to the finest grinding using a Pulverisete 7 planetary mill.

Example 2

A sample of red sludge was taken from a cross-section in a waste, effluent stream in a final settling tank in a natural landfill - open field. The sample suspension was allowed to settle and after the liquid phase was poured, the solid was subsequently dried at 105 ° C for 24 hours.

First, the sample is ground to 100% below 0.063 mm and the pH is adjusted by washing with distilled water followed by 1 mol / l sulfuric acid. Next, the sample is calcined at 750 ° C for 2 hours. Subsequently, the sample is subjected to bacterial leaching in an air-lift bioreactor, where 70 l of culture medium at pH 3.0 to 3.6 and composition as in Table 2 are used per 5 kg of sample.

The resulting suspension is then stirred and homogenized for one hour. Then, 10 L of pure bacterial culture of Acidithiobacillus ferrooxidans in distilled water is added, where the bacterial concentration is 10 ⁷ per ml of bacterial solution. Mixing and aeration of the suspension is ensured by connecting the air-lift bioreactor to the aeration pump. The leaching time is 4 weeks and the temperature is maintained at 25 ° C and pH at an optimum value of 1.8 to 2.2 at all times. 10N H ₂ SO ₄ is used to adjust the pH. After bacterial leaching, the representative samples were counted for the amount of bacteria by the MPN method. The suspension is filtered and the filter cake is washed with distilled water to pH 5.0. The samples are then dried at 60 ° C and then calcined (roasted) for 2 at 750 ° C. The calcination product is washed with distilled water and, after removal of the water-soluble substances, dried and ground in a ball mill to a particle size of 50 to 70 µm. A sample of the prepared pigment is further milled on a jet mill to a particle size below 30 µm. In order to achieve an optimum grain size corresponding to the pigments currently available on the market, the sample is subjected to the finest grinding using a Pulverisete 7 planetary mill.

-3EN 27025 Ul

By the MPN method of the above examples, it is meant the most probable number method that allows to determine the density of the microbial population without determining the actual number of cells or colonies.

The advantage of the technical solution is especially ecological and economical because red sludge is a waste material. In addition, the prepared pigment is stable and outperforms inorganic pigments based on ferric compounds (goethite and magnesia) commercially available in color and yield.

The resulting pigment is a multi-component product. Its exact structure has not yet been established. Only element X-ray fluorescence analysis was performed and also the annealing loss at 1000 ° C was determined. The pigment contains 0.80 to 1.20 wt. % Na, 0.45 to 0.67 wt. % Mg, 2.16 to 3.24 wt. % Al, 1.67 to 2.51 wt. % Si, 0.37 to 0.55 wt. % P, 0.10 to 0.15 wt. % S, 0.06 to 0.10 wt. % K, 1.09 to 1.63 wt. Ca, 4.58 to 6.864 wt. 0.27 to 0.41 wt. % Mn, 40.48 to 60.72 wt. 0.12 to 0.18 wt. Cr, 0.11 to 0.16 wt. % Ni, 0.04 to 0.06 wt. % Zn, 0.11 to 0.16 wt. And 0.03 to 0.04 wt. Pb, at a loss on ignition of 2.14 to 3.22 wt%, more preferably

0.90 to 1.10 wt. % Na, 0.50 to 0.62 wt. % Mg, 2.43 to 2.97 wt. % Al, 1.88 to 2.30 wt. % Si, 0.41 to 0.51 wt. % P, 0.12 to 0.14 wt. % S, 0.07 to 0.09 wt. % K, 1.22 to 1.50 wt. % Ca, 5.15 to 6.29 wt. Ti, 0.31 to 0.37 wt. % Mn, 45.54 to 55.66 wt. 0.13 to 0.16 wt. Cr, 0.12 to 0.15 wt. % Ni, 0.05 to 0.06 wt. % Zn, 0.12 to 0.15 wt. And 0.03 to 0.04 wt. %, At a loss on ignition of 2.41 to 2.95 wt.

The color of the pigment was also measured. The sample was spread in an oil paste where 3 g of white TiO ₂ pigment 0.966 g of linseed oil was used per 0.6 g of the measured sample. Spreading was carried out on a Muller automatic (2 x 50 revolutions). The paste was drawn from the paste and the color parameters of the drawing were measured with an Ultrascan XE spectrophotometer in the 380 to 780 nm wavelength range in the diffusion integrating sphere mode with d / 8 ° geometry and expressed as CIE Lab values. Hitch calibration was used for reproducibility of results, ie binding of measured results to standard pigments produced by Precheza Přerov, as - TP303 (hematite, red) and Y710 (goethite, yellow). The results are summarized in Table 3:

Parameter Value L * (proportion of light and red component) 57.3 and * (proportion of red and green component) 15.1 b * (proportion of yellow and blue components) 15.0 c (color saturation) 21.3 h (total color perception) 44.8

Table 3: Color measurement results

Example 3 - Restoration mixture

The restoration mixture was prepared from the pigment, where the pigment was bonded with a synthetic binder - 1.5% acrylate dispersion and the mixture, where the pigment was bonded with a natural binder - yolk emulsion.

The proportion of pigment in both cases was from 0.5 wt. % to 50.0 wt. and a binder fraction of from 50.0 wt. % to 99.5 wt.

The egg yolk emulsion was prepared from 1 egg yolk, 1 dcl of water, 3 grains of camphor, a teaspoon of polymerized linseed oil and 5 drops of fungicidal composition.

The acrylate dispersion of Example 3 is meant a commercially available acrylate dispersion, e.g. Primal SF016.

-4GB 27025 U1

Industrial applicability

The solution is useful for the preparation of a new orange pigment. The orange pigment according to the solution can be used in the construction industry to paint materials, as part of paints and in the restoration of murals and sgraffito. In powder form, it can be used as a high-quality, thermostable ecological pigment.

Claims (3)

An orange inorganic red sludge pigment comprising from 0.80 to 1.20 wt. % Na, 0.45 to 0.67 wt. % Mg, 2.16 to 3.24 wt. % Al, 1.67 to 2.51 wt. % Si, 0.37 to 0.55 wt. % P, 0.10 to 0.15 wt. % S, 0.06 to 0.10 wt. % K, 1.09 to 1.63 wt. % Ca, 4.58-6.86 wt. 0.27 to 0.41 wt. % Mn, 40.48 to 60.72 wt. 0.12 to 0.18 wt. Cr, 0.11 to 0.16 wt. % Ni, 0.04 to 0.06 wt. % Zn, 0.11 to 0.16 wt. And 0.03 to 0.04 wt. Pb at a loss on ignition of 2.14 to 3.22 wt%, more preferably 0.90 to 1.10 wt. % Na, 0.50 to 0.62 wt. % Mg, 2.43 to 2.97 wt. % Al, 1.88 to 2.30 wt. % Si, 0.41 to 0.51 wt. % P, 0.12 to 0.14 wt. % S, 0.07 to 0.09 wt. % K, 1.22 to 1.50 wt. % Ca, 5.15 to 6.29 wt. Ti, 0.31 to 0.37 wt. % Mn, 45.54 to 55.66 wt. 0.13 to 0.16 wt. Cr, 0.12 to 0.15 wt. % Ni, 0.05 to 0.06 wt. % Zn, 0.12 to 0.15 wt. And 0.03 to 0.04 wt. % Pb at a loss on ignition of 2.41 to 2.95 wt. can be prepared such that a red sludge containing 8.6 wt. % Na, less than 0.3 wt. Mg, 5.9 wt. Al, 4.20 wt. % Si, 0.135 wt. % P, 0.085 wt. % S, 0.079 wt. % K, 1.95 wt. % Ca, 2.70 wt. % Ti, 0.138 wt. % Mn, 35.9 wt. Fe, 0.072 wt. Cr, 0.078 wt. % Ni, 0.035 wt. % Zn, 0.086 wt. And 0.022 wt. Pb, at a loss on ignition of 7.90% by weight, is subjected to the following operations: a) drainage, pre-treatment of grain parameters, more preferably pH, b) calcination at 600 to 950 ° C, more preferably at 650 to 750 ° C, c) bacterial leaching, more preferably a culture of Thiobacillus, most preferably a culture of Acidothiobacillus ferrooxidans, d) filtration, washing with water, e) calcination at 600 to 950 ° C, more preferably at 650 to 750 ° C, (f) water washing, drying; and (g) grinding. A restoration composition comprising 0.5 to 50.0 wt. % pigment according to claim 1 and 50.0 to 99.5 wt. binder 1.5% acrylate dispersion. 3. A restoration composition comprising 0.5 to 50.0 wt. % pigment according to claim 1 and 50.0 to 99.5 wt. binder yolk emulsion.