RU2309898C1 - Method of production of modified red iron oxide pigments - Google Patents

Abstract

FIELD: chemical and paint-and-varnish industries; production of inorganic pigments.

SUBSTANCE: proposed method includes leaching-out of serpentine ore mixture containing magnesium and chromium by sulfuric or hydrochloric acid for obtaining iron-containing solution which is treated with hydrogen peroxide and is neutralized to pH= 7.0-8.0. Suspension thus obtained is filtered and iron hydroxide residue is dissolved with sulfuric or hydrochloric acid, then it is treated with alkaline reagent to pH=2.0-6.0 and is filtered. Then, iron hydroxide residue is washed off water-soluble ions, dried and burnt at temperature of 550-700C.

EFFECT: wide range of tints in processing and decontamination of sulfate and chloride waste obtained at production of periclase and chromite concentrate.

2 cl, 5 tbl, 6 ex

Description

The invention relates to chemical technology for the production of inorganic pigments and can be used in the chemical and paint and varnish industries, as well as in the processing, recycling and disposal of sulfate and chloride wastes obtained in the production of periclase and chromite concentrate.

A known method of producing iron oxide pigment from sludge-jarosite obtained during the purification of zinc solutions from iron. According to this method, jarosite (containing in wt.%: Potassium - 8, iron - 30, sulfur - 13, zinc - 0.15) in an amount of 500 g is mixed with a stoichiometric amount of caustic potassium (157 g) and fired at t = 800 ° C for two hours. Next, the product is washed with water, dried and crushed. The finished product is characterized by a high content of iron oxide (up to 90% Fe ₂ O ₃ ). (USSR author's certificate No. 666758, class C09C 1/24, publ. 1976).

The disadvantages of the method are:

- low pigment properties of the finished product: high dispersibility - 30 microns and hiding power - 90 g / m ² ;

- the method does not allow to obtain modified red iron oxide pigments with a wide range of shades;

- the known method cannot be used to obtain iron oxide pigments in the processing of magnesium-chromium ores, since the main mineral - serpentine, which is part of ore mixtures, does not decompose under the influence of alkalis at t = 800 ° C to produce iron, magnesium, silicon oxides other

In order to improve the pigment properties and expand the color gamut of shades, modifying additives in the form of oxides or hydroxides of aluminum, and (or) zirconium, and (or) titanium, and (or) chromium, and (or) nickel, and ( or) silicon in the ratio: per 100 parts by weight Fe ₂ O ₃ - 0.01-10.0 parts by weight modifying additives (Japan, No. 3055333 B2, IPC С09С 1/24, publ. 2000).

The obtained pigments are distinguished by bright color characteristics and good pigment properties.

However, these methods cannot be used in the process of obtaining iron oxide pigments from sludge - waste production of burnt magnesia from serpentine raw materials, since the required list of additives and their amount is already contained in the feedstock and it is impractical to add them to the sludge and the finished product; you only need to find a way to extract and use them.

The closest technical solution is a method for producing iron oxide pigment from waste products of titanium pigments. In this method, the solution after leaching is treated with alkali to pH = 6.0-7.0. The resulting suspension is filtered, the precipitate is dried, washed from chlorine or sulfate ions, dried again and calcined (calcined) at t = 500-800 ° C. The resulting product is characterized by high pigment properties and is used in the manufacture of paints and enamels (USSR Author's Certificate No. 1255629, IPC С09С 1/24, publ. 1986).

However, the pigment obtained by this method from sludge from the production of magnesium oxide (burnt magnesia) will have a significant drawback - a low content of the main substance - iron (III) oxide and a high content of impurities.

An object of the invention is to obtain a red iron oxide pigment with a maximum content of the main substance Fe ₂ O ₃ (at least 90%) while providing a wide range of shades (from red-light brown to dark red purple, raspberry).

The technical result of the use of the invention is the creation of a method for producing a pigment having a set of operational properties, a wide range of shades, optimal dispersibility, hiding power.

The specified technical result is achieved due to the fact that in the method for producing modified red iron oxide pigments, including neutralizing an acidic iron-containing solution to pH = 7.0-8.0, filtering the resulting suspension, washing the precipitate of iron hydroxide from water-soluble ions, drying and calcining it at at a temperature of 550-700 ° C, an acidic iron-containing solution is obtained after leaching of a serpentine magnesium-chromium ore mixture with sulfuric or hydrochloric acid, it is treated with hydrogen peroxide to oxidize two of ferrous iron to ferric and then served for neutralization, and before washing off the precipitate of iron hydroxide, it is additionally dissolved with the indicated acid, neutralized with an alkaline reagent to pH = 2.0-6.0 and filtered.

In this case, the neutralization is carried out with an alkaline, or soda, or ammonia solution.

The method is as follows:

Into an acidic iron-containing solution obtained after leaching of a serpentine magnesium-chromium-containing ore mixture with mineral acids (sulfuric or hydrochloric), a hydrogen peroxide solution is introduced to oxidize ferrous to ferric. Next, this solution is neutralized with an alkaline, soda or ammonia solution to a pH of 7.0-8.0. The resulting suspension is filtered. Sludge - a sludge containing iron (III) hydroxides, aluminum, chromium, nickel, a colloidal silicon solution and calcium sulfate (the so-called iron hydroxide precipitate), dissolved with acid (sulfuric or hydrochloric) and neutralized with an alkaline reagent (alkaline or soda, or ammonia solution) to pH = 2.0-6.0. The suspension is filtered, the precipitate of iron hydroxide (FeOOH) is repulped (washed from water-soluble ions) and filtered again. The purified iron hydroxide is dried and calcined at t = 550-700 ° C. The obtained iron oxide pigment is crushed, passed through a No. 0063 sieve. The finished product is characterized by high pigment properties and meets the requirements of TU 6-10-602-86.

It should be noted that

- neutralization of the acidic solution after leaching to pH <7.0 and pH> 8.0 is impractical because it leads to the loss of Fe ₂ O ₃ due to the transition of unoxidized ferrous iron to a solution of magnesium sulfate (or chloride) at pH <7.0 , and at pH> 8.0 - to increase the concentration of MgO in iron hydroxide, and therefore, in the finished product;

- neutralization of the solution obtained after dissolution of the precipitate of iron hydroxide at pH <2.0, significantly reduces the yield of the main substance - Fe ₂ O ₃ , and at pH> 6.0 the concentration of impurities AL ³⁺ , Cr ³⁺ Mg ²⁺ in the finished product is higher than permissible;

- firing the precipitate of iron hydroxide at temperatures below 550 ° C leads to pigment with a low content of the basic substance Fe ₂ About ₃ due to the high content of volatile components (the value of the loss index during calcination - SPP) in the finished product;

- firing the precipitate of iron hydroxide at temperatures above 700 ° C contributes to the production of darker pigments due to the transition of part of Fe ₂ O ₃ to Fe ₃ O ₄ .

Examples of the method.

Example 1 (by the method of the prototype). The solution obtained after leaching the serpentine magnesium-chromium ore mixture with sulfuric acid is neutralized with a soda solution (300 g / l Na ₂ CO ₃ , in an amount of 34 g per 100 g of ore) to pH = 7.0. The suspension is filtered, the filtrate - a solution of magnesium sulfate - is sent to obtain burnt magnesia, and the iron hydroxide precipitate is repulped (washed from Na ⁺ , SO ₄ ^2- , CO ₃ ^2- ions), filtered again, dried and calcined at t = 700 ° C . The pigment shade is light orange-red.

Example 2. The solution obtained after leaching the serpentine magnesium-chromium ore mixture with sulfuric acid is neutralized with a soda solution (300 g / l Na ₂ CO ₃ , in an amount of 34 g per 100 g of ore) to pH = 7.0. The suspension is filtered, the filtrate - a solution of magnesium sulfate - is sent to obtain burnt magnesia, and the precipitate of iron hydroxide is dissolved in sulfuric acid (560 g / l H ₂ SO ₄ , flow rate - 21.0 g H ₂ SO ₄ per 100 g of ore). An acidic solution of sulfates is treated with a soda solution (300 g / l Na ₂ CO ₃ , flow rate - 10 g Na ₂ CO ₃ per 100 g of ore) to pH = 2.0. The suspension is filtered, the precipitate of iron hydroxide is washed, again filtered. The mother liquor is sent for recycling, and purified FeOOH for firing at t = 700 ° C. The hue of the pigment is bright red-orange, purple.

Example 3. The solution obtained after leaching of the serpentine magnesium-chromium ore mixture with sulfuric acid is treated in accordance with the method of example 2 until an acidic sulfate solution is obtained, which is treated with a soda solution (300 g / l Na ₂ CO ₃ , flow rate 14 g Na ₂ CO ₃ per 100 g of ore) to pH = 2.8. Further, the processes of filtering and washing the precipitate are carried out according to a scheme similar to example 2. Calcination of FeOOH is carried out at t = 700 ° C. The pigment hue is reddish brown.

Example 4. An acidic solution obtained after leaching of a serpentine magnesium-chromium ore mixture with hydrochloric acid is treated with a solution of hydrogen peroxide and neutralized with a soda solution (300 g / l Na ₂ CO ₃ , consumption 32 g Na ₂ CO ₃ per 100 g of ore) to pH = 7.0. The suspension is filtered, the filtrate - a solution of magnesium chloride - is sent to obtain burnt magnesia, and the sludge (iron hydroxide precipitate) is dissolved in hydrochloric acid (210 g / l HCl, flow rate - 12 g HCl per 100 g of ore). The resulting acidic solution of Fe ³⁺ , AL ³⁺ , Cr ³⁺ , Ca ²⁺ and Ni ²⁺ chlorides is treated with a soda solution (300 g / l Na ₂ CO ₃ , flow rate - 18 g Na ₂ CO ₃ per 100 g of ore) to pH = 2.6. The filtering processes, washing the precipitate of iron hydroxide is carried out according to a scheme similar to example 2. The calcination of the precipitate is carried out at t = 550 ° C. The pigment shade is light red-brown.

Example 5. An acidic solution obtained after leaching of a serpentine magnesium-chromium ore mixture with hydrochloric acid is treated with a solution of hydrogen peroxide and neutralized with a soda solution (300 g / l Na ₂ CO ₃ , consumption 32 g Na ₂ CO ₃ per 100 g ore) to pH = 8.0. The suspension is filtered, the filtrate - a solution of magnesium chloride - is sent to obtain burnt magnesia, and the precipitate of iron hydroxide is dissolved in hydrochloric acid (210 g / l HCl, flow rate - 12 g HCl per 100 g of ore). The acid solution is treated with ammonia water (200 g / l NH ₄ OH, flow rate 18 g NN ₄ OH per 100 g of ore) to pH = 4.0. Next, the processes of filtering and washing the precipitate of iron hydroxide is carried out according to a scheme similar to example 2. It is fired at t = 700 ° C. The hue of the pigment is red-purple, raspberry.

Example 6. The precipitate of iron hydroxide (method for its preparation, see example 4) is dissolved in sulfuric acid (560 g / l H ₂ SO ₄ , flow rate - 21.0 g H ₂ SO ₄ per 100 g of ore). An acidic solution of sulfates is treated with a solution of sodium hydroxide (200 g / l NaON, consumption - 15 g NaON per 100 g of ore) to pH = 6.0. Further, the processes of filtering, washing the precipitate of iron hydroxide and firing are carried out according to a scheme similar to example 4. The pigment hue is red-purple, lighter than in pr. 5.

Iron oxide pigments obtained by the proposed method, according to the main properties correspond to TU 6-10-602-86 per red iron oxide pigment and are characterized by the following properties:

- mass fraction, in%:

the iron content in terms of Fe ₂ About ₃ - not less than 90.0%;

volatile substances - not more than 0.5;

water-soluble substances - not more than 0.2;

- hiding power, g / m ² - 5.0-7.0;

- dispersibility in drying oil, min - 20-30;

- oil absorption, g / 100 g of pigment - 20-30;

- the residue after wet sieving on a sieve with a mesh 0063,% - 0.2-0.3.

Pigment hue depends on

- the type of mineral acid (sulfuric or hydrochloric) used for leaching, the initial ore and dissolution of the hydrated iron residue,

- pH of the neutralization of the acidic solution and obtain hydroxide FeOOH,

- the concentration of modifying additives Al ₂ About ₃ , Cr ₂ About ₃ , SiO ₂ and others,

- firing temperature (calcination).

Tables 1-2 show the chemical and mineralogical compositions of the original ore.

Tables 3-4 show the properties of the initial solution and the obtained pigments.

Table 5 shows the obtained color shades of the pigments.

Table 1. The chemical composition of the ore Name of components SiO ₂ Al ₂ O ₃ MgO Cao Fe ₂ O ₃ total Cr ₂ O ₃ Na ₂ O Ni volatile Content% 37,2 1,52 34.63 0.55 7.80 6.0 0.41 0.23 11.66

Table 2. Mineralogical composition of the source ore The name of the mineral Serpentine Olivine Lame Quartz Chlorite Pyroxene RFP Content% 65.0 8.0 10.0 2.0 6.0 1,0 8.0

Table 3. The content of components in solution Leaching acid The content of components in solution, g / l Fe ₂ O ₃ FeO Cao Cr ₂ O ₃ Na ₂ O Ni H ₂ SO ₄ 13.2 3.30 1.16 1.06 0.87 0.49 Hcl 15.2 0.55 1.21 1.21 0.90 0.51

Table 4. The content of the components in the pigment No. op. p / p Alkaline reagent pH of formation of FeOOH t ° C calcination The pigment content,% Fe ₂ O ₃ Al ₂ O ₃ MgO Cao Ni Cr ₂ O ₃ SiO ₂ volatile one - - 700 58.3 14.26 14.63 4.86 0.16 4.70 1.25 0.48 2 Na ₂ CO ₃ 2.0 700 98.5 0.23 0.19 0.12 0.03 0.21 0.18 0.34 3 Na ₂ CO ₃ 3.1 700 97.3 0.86 0.26 0.15 0.02 0.74 0.29 0.38 four Na ₂ CO ₃ 3.8 550 95.3 1.21 0.95 0.23 0.03 1.49 0.34 0.50 5 NH ₄ OH 4.0 700 95.5 0.19 1.21 0.31 0.02 2.05 0.32 0.41 6 NaOH 6.0 700 92.6 2.04 1.75 0.41 0.03 2.38 0.31 0.49

Table 5. Color shades of pigments depending on the content of the basic substance Fe ₂ O ₃ and the method of their preparation No. op. p / p precipitation pH t ° C calcination The pigment content,% Color shades Fe ₂ O ₃ volatile one - 700 58.3 0.48 Light orange red 2 2.0 700 98.5 0.34 Bright red orange purple 3 3,1 700 97.3 0.38 Red brown four 3.8 550 95.3 0.50 Red light brown 5 4.0 700 95.5 0.41 Red-purple, raspberry 6 6.0 700 92.6 0.49 Red-purple, lighter than in op.5

Claims (2)

1. A method of obtaining modified red iron oxide pigments, including neutralizing an acidic iron-containing solution to a pH of 7.0-8.0, filtering the suspension, washing the precipitate of iron hydroxide from water-soluble ions, drying and calcining it at a temperature of 550-700 ° C, characterized in that an acidic iron-containing solution is obtained after leaching of a serpentine magnesium-chromium-containing ore mixture with sulfuric or hydrochloric acid, it is treated with hydrogen peroxide to oxidize ferrous iron to ferric and then odayut for neutralization, prior to laundering and its iron hydroxide precipitate is dissolved further said acid is neutralized with an alkaline reagent to pH 2.0-6.0 and filtered. 2. The method according to claim 1, characterized in that the neutralization is carried out with an alkaline, or soda, or ammonia solution.