RU2471836C1 - Method of producing iron oxide pigments - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: to obtain iron oxide pigments, iron oxide sludge, which is a water treatment waste, is dried, calcined and ground. The water treatment wastes used are ferruginous underground water with iron content of not less than 42%. Calcination is carried out by gradually heating the dried iron oxide sludge either to temperature of 600°C in order to obtain a chocolate brown pigment, or to temperature of 800°C in order to obtain a bright red pigment, or to temperature of 1050°C in order to obtain a black pigment. Once the required temperature is reached, the calcination device is turned off.

EFFECT: invention enables to recycle wastes of water treatment plants to obtain iron oxide pigments for coloured concrete, paving slabs, prime coats, enamel and paints.

2 cl, 1 dwg, 3 tbl, 3 ex

Description

The invention relates to the field of inorganic, in particular iron oxide, pigments used for the manufacture of paints that can be used in the building materials industry (for the production of colored concrete, paving slabs, primers, enamels, paints), as well as to the field of disposal of waste water treatment plants - sludge extracted from ferruginous underground waters during their treatment for industrial and household needs of the population.

The prior art methods for producing iron oxide pigments using natural minerals and waste as an initial raw material: aqueous solutions of iron salts of synthesis (Belenky EF, Riskin IV Chemistry and technology of pigments. - L .: Chemistry, 1974), of ocherous rocks from swamp iron ores (see RF patent No. 2143447, IPC6 С09С 1/24, C01G 49/08, publ. 12/27/1999), sludge from borehole hydraulic mining of iron ore (see RF patent No. 2402583, IPC (2006.01) С09С 1/24, publ. 10/27/2010), spent during the pickling of steels of hydrochloric acid solutions (see AS No. 749873, IPC С09С 1/24, publ. 07/23/1980), waste s metallurgical production formed by the thermal decomposition of spent pickling of carbon steels with hydrochloric acid solution (RF Patent №2257397, MPK7 C09 C1 / 24, C01G 049/06, publ. 27.07.2005).

The method of producing iron oxide pigments according to copyright certificate No. 749873 includes thermal decomposition of the initial hydrochloric acid solution at a temperature of combustion of combustible gas in an air stream of 480-750 ° C and washing the pigment with steam condensate. Depending on the temperature in the decomposition zone, pigments of red, red and lilac colors are obtained.

According to the method protected by patent No. 2257397, to obtain a red pigment, metallurgical iron oxide is wet milled at a concentration of 500-900 g / dm ³ in the presence of a neutralizing agent, it is washed from water-soluble salts to form an aqueous suspension of iron oxide with pH = 6- 10. The oxide suspension is then filtered and dried.

The disadvantages of the known methods are:

- the use of complex multi-stage technology, requiring a large number of containers for solutions, dispensers, pipelines;

- a large amount of waste generated without solving the problem of their disposal (for example, waste water containing iron in the form of ions, atoms, molecules is discharged into the sewer);

- the problem of obtaining pigments for obtaining non-ferrous cements without deterioration of their strength, durability and other standardized quality indicators is not solved;

- in the composition of the pigments remain undesirable impurities that were in the feedstock, which, when dyed in building materials, adversely affect their properties.

A known method of producing iron oxide pigment according to the patent of the Russian Federation No. 2117019 (IPC6 C09C 1/24, publ. 08.10.1998), according to which the iron oxide waste, as in the present method, is subjected to calcination, drying, grinding and the resulting high-quality pigments of different colors: brown, black and red. Selected as a prototype, the method of producing iron oxide pigment using spent iron oxide catalyst as a feedstock — waste processes of dehydrogenation of olefin or alkyl aromatic hydrocarbons involves calcining it in water vapor at 600-670 ° C for 1-3 hours, followed by cooling in a steam-air medium or steam-nitrogen mixture, taken in the ratio of 35: 1-1: 35 by weight at a speed of 25-35 ° C per hour to 200-300 ° C, and then in a nitrogen and / or air environment at a speed of 25-35 ° C per hour to 40-80 ° C, washing, drying and grinding the resulting pigment. The disadvantages of the method: multi-stage technology; the use of a large number of auxiliary materials (washing water, vapor-nitrogen mixture); high energy intensity; long working hours of furnaces during pigment calcination; impurities of chromium, zinc, molybdenum in the composition of the spent catalyst, which serves as the raw material in the prototype invention, do not allow the pigment to be considered an environmentally friendly building material.

Using this invention, pigments of high quality with different color characteristics are obtained from iron-containing waste for the production of paints, enamels, plastics, linoleum, paper. Upon receipt of the pigment, a complex and energy-intensive calcination procedure is used: heating the furnace to 600-670 ° C, keeping the pigment raw materials in a heated furnace for 2-3 hours, cooling with a programmed decrease in temperature in the atmosphere of gas mixtures of a certain composition. The method does not solve the problem of obtaining cheap pigment without the use of additional chemicals and disposal of iron oxide sludge, which is a waste of water treatment.

In technical essence and the problem being solved, the closest to the claimed method is the technology for producing cheap brown iron oxide pigment from sediments of electrochemical wastewater treatment of galvanic production according to the RF patent for invention No. 21118972, IPC С09С 1/00, С09С 1/24, publ. 09/20/1998. According to the invention according to the prototype, a sewage sludge of galvanic production with a moisture content of 65-85%, containing, calculated on the dry matter, wt.%: Fe ₂ O ₃ (75.0-97.3); Cr ₂ O ₃ (0.13-13.0), NiO (0.55-9.3); CaO (0.01-2.49); ZnO (0.01-2.0); CdO (0.01-0.2), mixed with reducing agents in an amount of 0.5-10 wt.%, Dried, calcined at a temperature of 500-800 ° C for 30-60 minutes and crushed. Depending on the amount and composition of the galvanic sludge and the reducing agents used at a temperature of 540, 650, 730 ° C, a chocolate brown pigment is obtained, 600, 680, 760 ° C - brown, 640, 690, 650, 700 ° C - dark brown.

By reducing chromium toxicity, the scope of application of cheap iron oxide pigments has been expanded. The advantages include the simplicity of the technology for producing pigment and its low cost. The disadvantage of the prototype is the presence in the feedstock of toxic elements: chromium and cadmium. Their presence does not allow us to consider the resulting pigment environmentally friendly. Also, the disadvantages include the limited color characteristics (only brown shades).

The objective of the invention is to obtain for the construction industry high-quality environmentally friendly iron oxide pigments with different color characteristics, to simplify the technology of their production with the simultaneous disposal of iron oxide sludge, which is a waste of water treatment facilities.

The technical result consists in obtaining chocolate-brown, bright red and black pigments due to the rearrangement of the initial iron oxide sludge in the crystal structure during calcination: when gradually heated, physically and chemically bound water is removed, GoET FeOOH - the main component of highly dispersed iron oxide sludge - goes into different forms iron oxide.

The problem is solved as follows. By analogy with the prototype, according to the claimed method for producing iron oxide pigments, iron oxide sludge, which is a waste of water treatment, is dried, calcined to obtain, for example, chocolate-brown color and, after calcination, is ground.

In contrast to the prototype, pigment is used for waste treatment of ferruginous underground waters with an iron content of at least 42%. The difference is also that calcination is carried out by gradually heating the dried iron oxide sludge, and to a temperature of 600 ° C to obtain a chocolate-brown color of the pigment, or to a temperature of 800 ° C to obtain a bright red color of the pigment, or to a temperature of 1050 ° C for receiving black color of a pigment. After reaching the desired temperature, the calcination device is turned off.

In the particular case, before calcining, the dried iron oxide sludge is further subjected to grinding.

The use of cheap secondary raw materials - iron oxide sludge (JOSH) - water treatment waste gives a number of significant economic and technical advantages over other methods of producing pigments. JOSH are widespread in some northern regions, for example, the West Siberian region, where they are isolated before industrial and drinking water from groundwater, which everywhere have a high iron content. They are waste polluting the environment, their preparation for use does not require complex equipment. The advantage of ZhOSH is its highly dispersed state (minimum particle size 0.02-0.03 mm) and the optimal chemical composition (the basis of the sludge is goeth FeOOH), which greatly facilitates the flow of chemical processes during heat treatment and simplifies all technological operations during its processing.

All parameters in the inventive method are obtained as a result of repeated experiments. For example, iron oxide sludge, in terms of oxides, may contain (%): Na ₂ O (0.2-0.3); K ₂ O (0.3-0.4); CaO (2.8-5.2); MgO (2.0-4.7); Fe ₂ O ₃ (42.0-44.5); Mn (2-3); Al ₂ O ₃ (0.5-1.0); TiO ₂ (0.04); SiO ₂ (2.5-5.5); P ₂ O ₅ (3.0-5.0), as well as trace amounts of other elements, water, carbon compounds. These components form a composition in which a combination of minerals is an optimal raw material that fully meets the requirements of iron oxide pigment production processes. When heated, the mineralogical composition of the sludge changes, a significant restructuring of the crystal structure of the components occurs, which is established by x-ray phase analysis and the method of thermogravimetry. As a result of physical and chemical transformations, the content of iron (III) oxide (in different ratios of alpha, beta and gamma forms) in the obtained pigments is 70, 75 and 77% when the feed is heated to temperatures of 600, 800 and 1050 ° C, respectively . In this case, the pigments have a stable color (respectively, chocolate brown, red, black), inherent in a certain combination of minerals in the structure of the pigment. The color and its shades depend mainly on the temperature to which the raw material was heated, regardless of the method and cooling rate of the pigment samples after calcining them.

The method has novelty, since significant features in the proposed combination in the prior art are not found. Distinctive features from the prototype signs do not explicitly follow from the prior art.

Thus, the method allows to achieve the following results:

- higher energy efficiency;

- simplification of technology (lack of reagents, a small number of stages);

- speed (pigment calcination time is determined by characteristics that affect the heating rate of the furnace);

- obtaining environmentally friendly material;

- receiving, depending on the temperature at which the heating is completed, different shades: chocolate brown, red, black;

- obtaining on the basis of the pigment high-quality colored cements and decorative stones.

The drawing shows a General view of an x-ray of a sample of a pigment calcined to a temperature of 800 ° C.

X-ray diffraction shows that the obtained pigment samples belong to the group of iron oxide pigments. The interpretation of the X-ray diffraction patterns showed that the basis of the red pigment is hematite Fe ₂ O ₃ . Appearance of pigments - powders of bright red, chocolate brown, black. Shades of color depend on the characteristics of the minerals obtained by heating to a certain temperature. The technical essence is illustrated by an example of a specific implementation.

Example 1. The initial wet finely divided JOSH after dehydration (excess moisture is removed by centrifuge, in a vacuum filter, filter press or other method) is dried to constant weight (indoors, on sludge pads using heating or naturally). The dried raw material is ground to a powder state (for example, in a ball mill or in another way) and fed to the calcination furnace, where it is heated to a temperature of 800 ° C for 2 hours. As a result of the physicochemical processes occurring under these conditions and associated with the rearrangement in the crystalline structure, VLB acquires a bright red color. Grinding the feedstock is not necessary before calcining to obtain the appropriate color, but grinding improves the quality of the target product. The resulting pigment can be removed from the furnace immediately after it is turned off or left to cool in the furnace. After cooling to ambient temperature, the pigment is crushed in any known device. The resulting pigment powder is shipped to the consumer.

Examples 2, 3. Processing JOSH was carried out analogously to example 1. Processing parameters and characteristics of the obtained pigments are shown in the table.

Table 1 Processing parameters and characteristics of iron oxide pigments Processing parameters and pigment characteristics Example Number one 2 3 Heating to temperature, ° С 800 600 1050 Duration of calcination, h 2 1.7 2,3 Pigment color Bright red Chocolate brown The black

The duration of heating to the appropriate temperature may be different, depending on the type of heating device used.

To prove the possibility of using the obtained pigments in the production of building materials, special experiments were carried out.

It is generally accepted that the amount of pigments added to concrete is 3-5% (1.5-2 kg per 50 kg of cement) for pigments with good coloring ability (Journal of Concrete Technologies, No. 1, March 30, 2009). Non-ferrous cement samples were made and their properties studied.

In the experiment, two types of cement were used: gray (grade ПЦ500Д0) and white (М250). To obtain samples used a solution with a ratio of cement: sand = 30: 70. The resulting pigment was introduced in an amount of 2, 3, 4 and 8% by weight of cement. To prepare the solution, the starting components were mixed in dry form, then they were shut with water in the amount necessary to obtain a solution of the required density.

From the resulting solution, cubes with a face of 3 cm were molded in silicone molds on a vibrating plate. At the same time, control samples containing no pigment were prepared. For each composition, 6 samples were made. Formed samples solidified in a bath with a hydraulic shutter for 20 hours. Then 4 samples of each composition were removed and steamed in a steaming chamber for 4 hours at 95 ° C. The samples were determined color and strength immediately after steaming, and 2 samples were returned to the bath with a hydraulic shutter, where they were kept for 28 days for comparison with samples hardening under normal conditions. Strength values are determined for compositions with gray and white cement, under various hardening conditions. Tables 2 and 3 show the test results of the samples.

table 2 Test results of samples prepared on the basis of gray cement Experience number The amount of pigment,% Water: dry ratio Compressive strength, MPa Color Steamed 28 days, steaming. 28 days, normal hardening one 0 0.2 25,4 28,2 51.5 Gray 2 2 26,4 26.1 52.8 gray pink (pale) 3 3 0.21 21.9 26.6 44.6 gray pink 5 four 0.21 19.1 31,2 40.9 light red 6 8 0.22 17.6 26.5 33.1 red

Table 3 The test results of samples prepared on the basis of white cement. Experience number The amount of pigment,% Water: dry ratio Compressive strength, MPa Color Steamed 28 days, steaming. 28 days, non-steaming. one 0 0.2 16.9 26.1 24.2 white 2 2 0.2 17.6 31,0 37.3 light pink 3 3 0.21 16.1 21.6 28.9 pink 5 four 0.21 16.6 27.6 24.4 light red

Thus, the possibility of using iron oxide pigments from iron-containing sludges of water treatment in the construction industry is shown. The optimal pigment content in the cement-sand mixture according to the indications of compressive strength and color is 4%.

Claims (2)

1. The method of producing iron oxide pigments, according to which the iron oxide sludge, which is a waste of water treatment, is dried, calcined to obtain, for example, a chocolate brown color and, after calcination, it is crushed, characterized in that the waste water is purified from ferruginous underground waters with an iron content of at least 42% and calcination is carried out by gradually heating the dried iron oxide sludge either to a temperature of 600 ° C to obtain a chocolate-brown color of the pigment, or to a temperature of 800 ° C to obtain a bright a different color of the pigment, or to a temperature of 1050 ° C to obtain a black color of the pigment, and after reaching the desired temperature, the calcination device is turned off. 2. The method of producing iron oxide pigments according to claim 1, characterized in that before calcining the dried iron oxide sludge is further subjected to grinding.

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