Method of producing iron oxide pigments

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

 

The invention relates to the field of inorganic, in particular micaceous iron, pigments, used for the production of paints, which can find application in the industry of construction materials (for colored concrete, paving, primers, enamels, paints), as well as to the field of waste water treatment plant - sludge isolated from glandular groundwater at their cleaning for industrial and domestic needs of the population.

The prior art methods of obtaining micaceous iron pigments using as a source of raw natural minerals and waste water solutions of salts of iron synthesis (Belenky E.F., Riskin IV Chemistry and technology of pigments. - Leningrad: Khimiya, 1974), Buffy rocks from bog iron ore (see RF patent №2143447, MPK SS 1/24, C01G 49/08, publ. 27.12.1999), sludge hydraulic borehole mining of iron ores (see RF patent №2402583, IPC (2006.01) SS 1/24, publ. 27.10.2010)worked at etching steels hydrochloric acid solutions (see A.S. No. 749873, IPC SS 1/24, publ. 23.07.1980), metallurgical wastes formed during thermal decomposition of waste at etching carbon steels hydrochloric acid solutions (patent RF №2257397, MPK7 from 09 C1/24, C01G 049/06, publ. 27.07.2005).

The method of obtaining micaceous iron pigments according to the author's certificate No. 749873 in which incorporates both thermal decomposition of the initial hydrochloric acid solution at a temperature of combustion of a combustible gas in air flow 480-750°C and washing of the pigment steam condensate. Depending on the temperature in the decomposition zone receive the pigments of red, red and purple.

By the way, is protected by patent No. 2257397, to obtain a red pigment metallurgical iron oxide is subjected to wet grinding when its concentration 500-900 g/DM3in the presence of a neutralizing agent, spend it washing from the water-soluble salts with the formation of the aqueous suspension of iron oxide with pH 6-10. Then the oxide slurry is filtered and subjected to drying.

The disadvantages of the known methods are:

- the use of complex multi-stage technologies that require a large number of containers for solutions, dispensers, piping;

- a large number of generated waste without solving the problem of their utilization (e.g., waste water containing iron in the form of ions, atoms, molecules, is discharged into the sewer);

- not solved the problem of obtaining pigments for color cements without compromising their strength, durability and other standard indicators of quality;

in the composition of the pigments remain undesirable impurities present in the feedstock, which, falling upon the colouring of building materials, adversely affect their properties.

A method of obtaining iron oxide pigment according to the patent of Russian Federation №2117019 (MPC SS 1/24, publ. 08.10.1998), according to which W is isooctene waste as to the claimed method, is subjected to calcination, drying, grinding and get in the high-quality pigments of different colors: brown, black and red. Selected as a prototype method for producing iron oxide pigment is used as the feedstock of waste iron oxide catalyst - waste processes dehydrogenation of olefinic or alkylaromatic hydrocarbons include annealing it in an environment of steam at 600-670°C for 1-3 h and then cooled in an environment of steam-air or steam-nitrogen mixture, taken in the ratio of 35:1-1:35 by weight with the speed of 25-35°C per hour up to 200-300°C, and then in a nitrogen atmosphere, and/or air speeds of 25-35°C per hour up to 40-80°C, washing, drying and grinding the obtained pigment. The disadvantages of the method: a multi-stage technologies; the use of a large number of auxiliary materials (water for washing, steam-nitrogen mixture); high energy consumption; long duration of operation of furnaces with annealing pigment; an impurity of chromium, zinc, molybdenum in the composition of the spent catalyst that serves as a raw material in the invention of the prototype is not allowed to read the pigment environmentally friendly building material.

With this invention of iron-bearing wastes receive the pigments of high quality with different color is starting characteristics for the production of paints, enamel, coloring of plastics, linoleum, paper. Upon receipt of the pigment is complicated and power-consuming procedure of annealing: heat oven to 600-670°C, keeping raw material for pigment in a hot oven for 2-3 hours, cooling with programmable temperature decrease in the atmosphere of a gas mixture of a certain composition. The method does not solve the problem of obtaining cheap pigment without the use of additional chemicals and disposal of micaceous iron sludge is waste water treatment.

Technical essence and the tasks closest to the claimed method is a technology of obtaining cheap brown micaceous iron pigment from precipitation electrochemical treatment of wastewater of electroplating on a Russian patent for invention №2118972, IPC SS 1/00, SS 1/24, publ. 20.09.1998. According to the invention of the prototype sewage sludge, electroplating with humidity 65-85%, containing, calculated on the dry matter, wt.%: Fe2O3(75,0-97,3); CR2O3(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 the amount of 0.5 - 10 wt.%, dried, calcined at a temperature of 500-800°C for 30-60 minutes and milled. Depending on the amount and composition of galvanic sludge and used reducing agents at a temperature of 540, 650, 730°With get chocolate to enevy color pigment, 600, 680, 760°C brown, 640, 690, 650, 700°C - dark brown.

By reducing the toxicity of chromium expanded scope cheap micaceous iron pigments. The advantages include the simplicity of technology for pigment and its low cost. The disadvantage of the prototype is the presence in the feedstock toxic elements: chromium and cadmium. Their presence does not allow to consider the resulting pigment environmentally friendly. As well as the disadvantages include limited color characteristics (only brown).

The task of the invention is to obtain for the construction industry with high-quality organic micaceous iron pigments with different color characteristics, to simplify the technology of their production with the simultaneous utilization of micaceous iron sludge is waste water treatment facilities.

The technical result consists in obtaining chocolate brown, bright red and black pigments due to the change in the crystalline structure of the original micaceous iron sludge during annealing: during the gradual heating is removed physically and chemically bound water, goethite FeOOH is a major component of fine micaceous iron sludge is transferred in different forms of iron oxide.

The problem is solved as follows. For similar and with the prototype, by the present method of obtaining micaceous iron pigments micaceous iron sludge is waste water, dried, and calcined to obtain, for example, chocolate-brown and after annealing the milled.

Unlike the prototype to obtain a pigment is used, the waste water treatment glandular groundwater with iron content of at least 42%. The difference is that the annealing is carried out by gradually heating the dried micaceous iron sludge, and to a temperature of 600°C to obtain chocolate brown pigment, or to a temperature of 800°C to obtain a bright red pigment, or to a temperature of 1050°C. to obtain a black pigment. After reaching the desired temperature, the device for the ignition off.

In the particular case before calcination of the dried micaceous iron sludge is additionally subjected to grinding.

Cheap recycled materials - micaceous iron sludge (AS) - waste water treatment provides a number of significant economic and technical advantages over other methods of obtaining pigments. AS widespread in some Northern regions, such as Western-Siberian region, where they emit before industrial and potable use of groundwater, which generally have a high iron content. They are waste, polluting the environment, their preparation does not require complex equipment. The advantage of GAS is highly dispersed state (the minimum particle size of 0.02-0.03 mm) and the optimal chemical composition (based slurry is goethite FeOOH), which greatly facilitates the process of chemical processes, heat treatment and simplifies all manufacturing operations at its processing.

All parameters in the present method obtained in repeated experiments. For example, micaceous iron sludge, in terms of oxides, may contain (%): Na2O (0,2-0,3); K2O (0.3 to 0.4); Cao (2,8-5,2); MgO (2,0-4,7); Fe2O3(42,0-44,5); MP (2-3); Al2O3(0,5-1,0); Tio2(0,04); SiO2(2,5-5,5); P2O5(3,0-5,0), as well as trace amounts of other elements, water, carbon compounds. These components form a composition in which the aggregate of minerals is the best raw material that meets the requirements of the processes of obtaining micaceous iron pigments. When heated changes mineralogical composition of the sludge, a significant rebuilding of the crystal structure of the components that you have installed x-ray phase analysis and the method of thermogravimetry. As a result of physical-chemical transformations of the content of iron oxide (III) (in different proportions, alpha, be the a - and gamma-forms) in the obtained pigment is 70, 75 and 77% when heated feedstock to temperatures of 600, 800 and 1050°C, respectively. While the pigments are stable colors (respectively, chocolate brown, red, black)inherent to a particular combination of minerals in the structure of the pigment. Color and its shades depend mainly on the temperature to which the heated raw material, regardless of the method and the cooling rate of the samples of the pigments after calcination.

The method is new, because the essential features of the proposed combination in the prior art is not detected. Distinctive features of the prototype characteristics not explicitly follow from the prior art.

Thus, the method allows to achieve the following results:

- higher energy efficiency;

- simplification of technology (no reagents, a small number of stages);

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

- getting environmentally friendly material;

- receive, depending on the temperature at which heat ends, different colors: chocolate brown, red, black;

- getting-based pigment of high quality colored cements and decorative stones.

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

Rentgenograficheski shown that the obtained pigment samples belong to the group of micaceous iron pigments. Transcript of the radiographs showed that the basis of the red pigment is hematite Fe2About3. The appearance of pigment powders bright red, chocolate brown, black. The colors depend on the characteristics of the minerals obtained when heated to a certain temperature. Technical essence is illustrated by a specific example.

Example 1. The original wet fine AS after dehydration (the excess moisture is removed in a centrifuge, vacuum filter, filter press or other means) is dried to constant weight (indoors, in the sludge beds using heating or naturally). The dried raw material is crushed to a powder (for example, a ball mill or other means) and fed into the kiln for calcination, where it is heated to a temperature of 800°C for 2 hours. Occurring in these conditions, physico-chemical processes associated with the restructuring in the crystal structure, AS acquires a bright red color. Grinding of raw materials is not a mandatory operation before calcination to obtain the appropriate color, but grinding improves the quality target product the KTA. The resulting pigment can be removed from the furnace immediately after switching it off or leave to cool in the furnace. After cooling to ambient temperature the pigment is ground in any known device. The resulting pigment powder is shipped to the consumer.

Examples 2, 3. Processing GAS was carried out analogously to example 1. Processing parameters and characteristics of the pigments listed in the table.

Table 1
Processing parameters and characteristics of micaceous iron pigments
Processing parameters and characteristics of the pigmentsNumber example
123
Heating up to temperature, °C8006001050
The duration of calcination, h21,72,3
Color pigmentBright redChocolate brownBlack

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

To prove the possibility of the use of these pigments in the manufacture of building materials conducted special experiments.

It is generally accepted that the amount of pigment added to the concrete, is 3-5% (1.5 to 2 kg per 50 kg of cement) for pigments with good coloring power (magazine "concrete Technology", No. 1, 30.03.2009). Were produced samples of colored cement and studied their properties.

In the experiment, was used to cement the two species: grey (brand PTSD) and white (M250). To obtain the sample solution was used with a ratio of cement: sand=30:70. The resulting pigment was injected at 2, 3, 4 and 8% by weight of cement. To prepare the solution of the original components were mixed in dry form, then shut the water quantity necessary to obtain a solution of a desired thickness.

From the solution obtained was molded cubes with edge 3 cm in silicon forms on the vibrating plate. Simultaneously preparing control samples contained no pigment. For each composition was produced in the 6 samples. Molded samples for 20 h was verdeli in the bath with hydraulic gate. Then 4 specimens of each composition were extracted and disappear to who was Ivalice in the steam chamber for 4 hours at 95°C. The samples was determined color and strength immediately after heat treatment, and 2 of the sample was returned to the bath with hydraulic gate, where he stood for 28 days for comparison with samples curing under normal conditions. Defined values of strength for compositions with grey and white cement, under different conditions of curing. In table 2 and 3 presents the results of the test samples.

Table 2
The test results of samples prepared on the basis of grey cement
no experienceThe amount of pigment, %The ratio of water: dry componentsCompressive strength, MPaColor
Steamed28 days, proper.28 days normal curing
100,225,428,251,5grey
22 26,426,152,8gray-pink (pale)
330,21of 21.926,644,6gray-pink
540,2119,131,2of 40.9light red
680,2217,626,533,1red

Table 3
The test results of samples prepared on the basis of white cement.
no experienceThe amount of pigment, %The ratio of water:dry componentsCompressive strength, MPaColor
Steamed28 days, proper.28 days, aproper.
100,216,926,124,2white
220,217,631,037,3light pink
330,2116,121,628,9pink
540,2116,627,624,4light red

Thus, the use of micaceous iron pigments from iron-containing sludge treatment in the construction industry. The optimum content of the pigment in the cement-sand mixture according to the testimony of compressive strength and color is 4%.

1. The method of obtaining micaceous iron pigments according to the mu micaceous iron sludge, is waste water, dried, and calcined to obtain, for example, chocolate-brown and after annealing are crushed, characterized in that use waste water treatment glandular groundwater with iron content of at least 42%, and the annealing is carried out by gradually heating the dried micaceous iron sludge or to a temperature of 600°C to obtain chocolate brown pigment, or to a temperature of 800°C to obtain a bright red pigment, or to a temperature of 1050°C. to obtain a black pigment, while after reaching the desired temperature, the device for the ignition off.

2. The method of obtaining micaceous iron pigments according to claim 1, characterized in that before calcination of the dried micaceous iron sludge is additionally subjected to grinding.



 

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