RU2740752C1 - Method of producing brick-red iron oxide pigment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in production of decorative varieties of concrete, ceramics and paint materials. To obtain iron oxide pigment from steel-smelting slag of converter production method, slag is ground and mixed with 35 % acetic acid solution in reactor equipped with mixer at rate of 100 rpm. Adding sodium hydroxide to the obtained solution to pH 8–9 with increasing temperature to 59 ± 1.5°C, settling for 4 hours. Solution of calcium, sodium, magnesium acetate is removed. Precipitate is washed at least 6–7 times with water in the reactor itself to pH 6. Solution from washing is connected to a solution of acetates. Method then includes adding to sludge 25 % sulphuric acid, turning mixer and increasing temperature to 80 °C is held for 24 hours for passage of reactions. Iron (II) sulphate solution which is stable for 4 hours is removed from the reactor. Obtained residue is washed 5–6 times with water in a reactor and drained in the form of pulp from the reactor. Solution from washing is added to a solution of iron (II) sulphate. Resulting solution is placed for 24 hours into muffle furnace at temperature of 180–200 °C. Then temperature is increased with rate of 10 °C/min to 650 °C is isothermally held for 2–3 hours. Obtained mass is milled in ball mill for 2–3 minutes, washed, dried at 80–100 °C and ground into powdered pigment.

EFFECT: invention makes it possible to carry out waste-free recycling of steel-smelting slag to obtain iron-oxide pigment of brick-red colour with content of α-Fe₂O₃ 93–95 %.

1 cl, 2 tbl, 1 ex

Description

The invention relates to the technology of inorganic pigments and can be used for the production of decorative varieties of concretes and mortars, as well as ceramics, paints and varnishes, etc. The brick-red iron oxide pigment has a spherical shape of ultra-small particles, which determines its yellowish-red deep shade (yellow -red shade) close to brick (corresponds to the shade of Bayferrox 110 pigment).

Known common basic method for producing iron oxide pigment, consisting in the thermal decomposition of chemically pure heptahydrate iron (II) sulfate:

A known method of producing iron oxide pigments according to the Pennimman-Zopf principle using pure materials (Penniman Jr. R.S., US 1327061 A, 1917). However, the disadvantages of this method, in addition to the use of pure materials, are the complexity and duration of the processes.

A known method of producing iron oxide pigment from steelmaking slag, consisting of heat treatment of finely ground slag with coal powder (soft coal) at a temperature of 500-800 ° C (Cui Yuyuan et al. Advanced Materials Research, 2013, 595-598 pp.). The disadvantages of this method are the use of only the magnetic part of the slag as raw material, the difficulty of controlling the process of the transition of the slag into the pigment, the low coloring power of the pigment - 56 g / m ² .

A known method of obtaining pigments from non-ferrous metallurgy slags by mixing powdered slags with calcium carbonate and zinc oxide at a temperature of 1000-1100 ° C (Marian Schwarz et al. Chemical papers, 2012, 248-258 pp.) The disadvantage of this method is the high temperatures of formation of pigments, high and dangerous content of lead in pigments, lack of data on the coloring ability of the latter.

A known method for producing iron oxide pigment based on scrap metal and microsilica as seeds for crystal growth (Leiderman L.P., RU 2036177, 2003). The disadvantages of this method are the complexity of the technology, the use of a large amount of additional iron to feed the synthesis processes, the possibility of implementing the proposed method when using slags as the main raw material is not given.

The closest to the proposed method is a method for producing iron oxide pigment from steelmaking slag using acetic acid to extract calcium and subsequent hydrothermal treatment of ferruginous sediment (Camille Crouzet et al., Frontier in Earth Science, 2017, 15 p.). The disadvantages of this method are: a fairly high consumption of acetic acid (500 g of acid 10 g of slag), the use of an autoclave with a high pressure of 300 bar and a temperature of 300-500 ° C, the use of a complex method for the disposal of a by-product (calcium acetate) into calcite, no assessment coloring properties of the pigment.

The objective of this invention is to develop an effective and waste-free mass method of utilization of steel-making slags of the converter production method, which do not have valuable properties for use in concrete technology and other industries and polluting the surrounding useful land areas with numerous dumps, with the receipt of a conditioned product - iron oxide pigment. Recycling and processing of steel-making slag is an important problem in improving the environmental situation around the world.

The technical task is achieved by the fact that to obtain an iron oxide pigment with a content of α-Fe ₂ O ₃ - 93-95% from the steelmaking slag of the converter production method using acetic acid to extract calcium, according to the proposed method, the slag is ground to a specific surface area of 3000-3200 cm ² / g, mixed with a solution of 35% acetic acid in a reactor equipped with a stirrer at a speed of 100 rpm, in a ratio of 1: 6 for 15 minutes to a temperature of 30-35 ° C at pH = 3, then the addition to the obtained solution of 1.1 parts to the mass of the initial slag of sodium hydroxide to pH = 8-9 with an increase in temperature to T = 59 ± 1.5 ° C, settle for 4 hours with the mixer turned off, remove the solution of calcium, sodium, magnesium acetates, sediment at least 6-7 times washed with water in the reactor itself to pH = 6, the solution from the washing is combined with a solution of acetates, add 5 parts to the sediment to the mass of the initial slag 25% sulfuric acid, turn on the stirrer and raise the temperature to 80 ° C, stand for 24 hours for the reactions to proceed, then turn off the stirrer, the solution of iron (II) sulfate settled for 4 hours is removed from the reactor, the resulting precipitate is washed 5-6 times with water to pH = 5-6 in the reactor and poured out in the form of a slurry from the reactor , the solution from the washing is added to the solution of iron (II) sulfate, then the solution is placed for 24 hours in a muffle furnace at a temperature of 180-200 ° C, and then the temperature is increased at a rate of 10 ° C / min to 650 ° C, isothermal holding is carried out in for 2-3 hours, the resulting mass is ground in a ball mill for 2-3 minutes, washed, dried at 80-100 ° C and ground into a powdery pigment.

The proposed method consists in the fact that the steelmaking slag (Table 1) in the state of delivery (not undergoing magnetic separation), having a chemical composition: CaO - 44.26%, MgO - 7.04%, SiO ₂ - 12.5%, Al ₂ O ₃ - 0.57%, Fe ₂ O ₃ - 34.19%, others - 1.44%, is ground in a ball mill to the maximum possible specific surface area - 3000-3200 cm ² / g. Next, the slag powder is loaded into a reactor with an agitator (rotation speed of 100 rpm), a solution of acetic acid of 35% concentration is added to it in a ratio of 1: 6 by weight (1 part of slag to 6 parts of acid is the optimal amount for the extraction reactions , a deviation to the larger side causes an undesirable overrun of the reagent, to a smaller one - incomplete extraction of calcium and magnesium). Include a stirrer; the mixture is stirred for 15 minutes, the end of the reaction is estimated by the drop in temperature from T = 55 ± 2.5 ° C to 30-35 ° C (completion of the reaction); pH of the solution 3.

Calcium and magnesium (1), partly iron (2) completely pass into the solution:

To adjust the viscosity and facilitate handling and mixing, the mixture is diluted with the required amount of water. Next, NaOH is introduced into the resulting solution in an amount of 1.1 mass parts to the mass part of the original slag (1: 1.1 - an increase in this ratio leads to an overrun of the reagent and an increase in washing cycles, with less - no iron hydroxide precipitate), as a result of which the precipitate from the solution passes all the iron that was previously in solution in the form of Fe (OH) ₂ (3); the reaction takes place at pH = 8-9, the temperature rises to T = 59 ± 1.5 ° C.

The stirrer is turned off, the reacting components settle for 4 hours, then the complex solution of calcium, sodium and magnesium acetates is removed from the reactor using a drain pipe, and the precipitate is washed at least 6-7 times with water (complete washing out of traces of calcium, sodium, magnesium salts; at with smaller numbers of washing cycles, the resulting product will be contaminated with these undesirable elements, with large numbers - an increase in the duration of the operation and water consumption) in the reactor itself until the pH value is 6; the solution from the wash is combined with the acetates solution. Next, sulfuric acid of 25% concentration is introduced into the reactor in an amount of 5 mass parts to 1 mass part of the initial slag (taken with a slight excess due to the varying iron content in the initial material and for the most complete dissolution of iron, an increase in excess of this amount leads to an overrun of the reagent and an increase in the duration of the removal of sulfuric anhydride during the calcination process, a decrease - to incomplete dissolution of iron); The pH of the solution drops to 1. The temperature in the reactor is raised to 80 ° C (the temperature at which the transition of iron to the solution is active), the stirrer is turned on and left for 24 hours to undergo the reaction according to the scheme (4):

The stirrer is turned off and the aqueous solution of iron (II) sulfate settled for 4 hours is removed from the reactor with a drain pipe into an acid and heat-resistant container, and the precipitate is washed 5-6 times with water (complete extraction of the iron sulfate solution, an increase in cycles leads to an increase in operation time and water consumption, a decrease - a certain amount of solution will remain in the sediment and will exclude further use of the sediment) to pH = 5-6 and in the form of a pulp is also removed from the bottom of the reactor with a drain pipe; the solution from the wash is added to the iron (II) sulfate solution. Next, this solution of iron (II) sulfate in containers is placed in an electric muffle furnace equipped with an exhaust hood for the process of evaporation of excess water at 180-200 ° C (at a given temperature and time, excess water is smoothly and completely removed) for 24 hours, and then the temperature is increased stepwise at a rate of 10 ° C / min (until the time of reaching the maximum temperature, bound water and partly sulfuric anhydride are gradually removed) and subjected to dehydration (5) followed by calcination (6) at 650 ° C; the time of isothermal holding is 2-3 hours (for a given period of time and at a given temperature, the material is completely converted into iron oxide, a decrease in time or temperature does not allow complete conversion to iron oxide, an increase - an increase in energy consumption). The following reactions take place:

The resulting mass is ground in a ball mill for 2-3 minutes, washed from water-soluble compounds, dried in an oven at 80-100 ° C and ground in a ball mill to form a powdery pigment. The iron extraction rate is 98-99%. The resulting sulphurous gas at the stage of calcination is fed through a hood to a tank with water, with the subsequent formation of sulfuric acid, again suitable for use in the technological chain.

The by-products formed as a result of pigment synthesis - a complex solution of calcium, sodium and magnesium acetates, as well as a precipitate consisting of silica SiO ₂ - can be successfully used in concrete technology as antifreeze and mineral additives, respectively.

Technical characteristics of a brick-red iron oxide pigment obtained using the proposed method, based on steelmaking slag of the converter production method, are given in table. 2.

Example

The reactor is charged with 60 g of ground steelmaking slag and 360 g of a solution of 35% acetic acid is added, the stirrer is turned on for the duration of the reaction. The viscosity of the mixture is adjusted by the additional introduction of 400 g of water. After 30 minutes sodium hydroxide is added in the amount of 66 g. After 1 hour the stirrer is turned off, the solution is allowed to settle for 4 hours and the solution of calcium, sodium and magnesium acetates is removed. The precipitate is washed several times, then 300 g of a solution of 25% sulfuric acid is added, the stirrer is turned on and the temperature in the reactor is raised to 80 ° C for 24 hours.Then the solution of iron (II) sulfate is defended for 4 hours and removed, the precipitate is washed with water in the reactor itself and also removed; the solution from the washing is combined with a solution of iron (II) sulfate and placed in a muffle furnace for 24 hours at a temperature of 180-200 ° C, and then the temperature is gradually increased to 650 ° C and kept for 2-3 hours; the resulting mass is ground in a ball mill, washed, dried and ground into a powdery pigment. From 60 g of slag is formed in terms of dry matter: 17 g of sediment consisting of SiO ₂ , 149 g of calcium, sodium, magnesium acetates and 25.8 g of iron oxide pigment.

The proposed method makes it possible to efficiently and waste-free utilize steel-making slags of the converter production method, polluting the surrounding useful land areas and to obtain a conditioned product - iron oxide pigment.

Claims (1)

A method of producing an iron oxide pigment with an α-Fe ₂ O ₃ content of 93-95% from a steelmaking slag of a converter production method using acetic acid, characterized in that the slag is ground to a specific surface area of 3000-3200 cm ² / g, mixed with a solution of 35% acetic acid in a reactor equipped with a stirrer at a speed of 100 rpm in a ratio of 1: 6 for 15 minutes to a temperature of 30-35 ° C at pH = 3, then adding to the resulting solution 1.1 parts to the weight of the initial slag of hydroxide sodium to pH = 8-9 with an increase in temperature to T = 59 ± 1.5 ° C, settle for 4 hours with the mixer off, remove the solution of calcium, sodium, magnesium acetates, wash the precipitate at least 6-7 times with water in the reactor to pH = 6, the solution from washing is combined with a solution of acetates, 5 parts are added to the precipitate to the mass of the initial slag of 25% sulfuric acid, the stirrer is turned on and the temperature is raised to 80 ° C, the reaction is held for 24 hours, then the mesh is turned off alka, the solution of iron (II) sulfate settled for 4 hours is removed from the reactor, the resulting precipitate is washed 5-6 times with water to pH = 5-6 in the reactor and poured out in the form of a slurry from the reactor, the solution from the washing is added to the solution of iron sulfate ( II), then the solution is placed for 24 hours in a muffle furnace at a temperature of 180-200 ° C, then the temperature is increased at a rate of 10 ° C / min to 650 ° C, isothermal holding is carried out for 2-3 hours, the resulting mass is ground in a ball mill for 2-3 minutes, washed, dried at 80-100 ° C and ground into powdery pigment.