LT5803B - Method of processing iron-containing sludge into pigmented material - Google Patents

Abstract

The present invention relates to the field of industrial ecology. It deals with the process in which sludge, recovered in waste water treatment by hetero-coagulation is converted into red, redbrown pigment material. At first sludge is treated by phosphoric acid and afterwards by water-soluble zinc salt, and partly by zinc sulfate in the molecular ratio of Fe2O3 to ZnO as 1 to 0,1-0,3; the obtained mixture is homogenised, dried and thermally treated at the temperature of 800-850 oC.@

Description

The present invention relates to the field of industrial ecology, and more particularly, to the processing of iron-containing sludge obtained after the heterocoagulative treatment of wastewater from heavy metals into a red-brown pigment.

Wastewater containing heavy metal ions (Zn ²⁺ , Cr ⁶⁺ , Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Ni ²⁺ , etc.) is mainly formed during the production of non-ferrous metals, galvanic coatings on plastic and metal surfaces such as etching of metals, processing of printing plates, etc. The decontaminated waters are discharged to the sewer, but remain galvanic Siam, which is saturated with the heavy metals already mentioned. Heavy metals are classified as hazardous waste according to the EC Waste Framework Directive 75/442 / EEC of 15.07.1975 because they can have a harmful effect on the living organism when released into the surrounding environment.

Therefore, the problem of utilization of sludge containing heavy metal ions remains an important problem worldwide. The countries of the European Community shall be responsible for the management of hazardous waste on 12-12-1991. EC Directive 91/689 / EEC.

Known wastewater treatment technology for heavy metals [Patent No. 4109 B, TPK 6 C02F 1/62 publ. 1997-02-25] using ferro-ferrihydrazole (FFH), which is a suspension of iron II) and (III) oxide hydrates. The treatment of wastewater produces a slurry with a high iron content (more than 60% on a dry basis). This makes it possible to efficiently process the sludge and to obtain inorganic iron-containing pigments [EyąnjioBCKHC JI., EymuioBCKuc K)., EmeHKO JI. C. // XnMimecKoe h He (to) Tera3OBoe MauiHHOCTpoeHHe. N ° 11,2004, c. 36-38].

Natural mineral iron-containing pigments with a sufficiently wide range of colors whose shade is determined by the iron oxide present in the mineral are known. For example, mixed iron oxide (II) and (III) (triple iron tetraoxide) - Fe3O4 - is black and found naturally in the form of mineral magnetite. Iron trioxide (a Fe2C> 3) is a red pigment. It contains pigments such as Persian red (75% FejCb) and Spanish red (85% Fe2C> 3). Depending on the shape and size of the Fe2O3 particles, the color can vary from orange to purple-red. It is found in nature in the form of red mineral hematite (a Fe2³3) [The Merck Index, 14 Edition / publ. Merck & Co.Inc., White House Station, NJ, 2006, Table-63; KopcyHCKHH JI. Φ., KanHHCKaa T. B., ΟτβπηΗ C. H. // HeopraHHuecKne πΗΓΜβΗΤΒΐ: CnpaBOHHHK. Cri6: Χημηχ, 1992, 336 c.].

Known and widely used natural pigment iron scavenger of cherry red color, consisting of Fe ₂ U 3 with minor impurities of clay and quartz. Surike contains 75-95% Fe ₂ U 3, more than other natural pigments. Also known is red natural pigment mummy containing 20-70% Fe ₂ C> 3 [KopcyHCKHii JI. Φ., KajiHHCKaa TB, ΟτεπηΗ CH // HeopramnecKue ΠΗΓΜβΗΤΒΐ: CnpaBOHHHK. C1T6: Χημηη, 1992, 336 c.].

Natural iron-containing pigments are obtained by mechanical grinding of the minerals containing them, or by the enrichment and heat treatment of iron-containing ores.

These pigments are inexpensive but lack color brightness, lack temperature resistance and good technical coloring properties.

Synthetic iron-containing pigments are made from iron salts by precipitation or by heat treatment. These pigments generally do not have the aforementioned disadvantages [KpacHoSan H. Γ., JlaTMineB K). B. // Βκοηομηκβ, τβχΗοποπίΗ h opraHH3aima nporoBOACTBa acejie3oconepacamnx πηγμ6Ητοβ: Οίήορ. ΡίΗφορΜ., ΗΗΗΤ3ΧΗΜ.- M., 1991, c. 45],

From patent RU no. No. 2057154 (TPK 6 C09C 1/24) discloses a brown phosphate-iron oxide pigment, wherein the pigment is solubilized at 90-100 ° C from a solution of ferric nitrate containing phosphoric acid in the presence of Fe ₂ C> 3: P ₂ 0s molar ratio of 1.00: (0.12-0.18) in the presence of urea. It is then filtered, dried and treated at 500-700 ° C. However, washing and filtering the gel-like product from nitrate ions takes time and expensive iron nitrate is used.

Patent RU No. No. 2086591 (TPK 6 C09C 1/24) discloses a method for obtaining a brown pigment using Marten furnace or blast furnace waste in combination with calcium hydrogen hydrogen tetraoxophosphate (CaHPCU) in a ratio of 1: (0.05-0.08), maintaining the mixture at 60-80 ° C. at 1.0 to 2.0 hours, followed by washing the product with water-soluble materials and treating at 150 to 350 ° C. The disadvantage of this method is that the preparation of CaHPO ₄ requires separate apparatus and it also reduces the Fe (III) content of the chromophore.

From patent CN no. 1310207 (TPK 7, C09 1/24, publ .:

http // v3.espacenet.com / searchResults? locale = en_US & AB = red + pigment * + AND + sludge & c .... 23.03.2009 (accessed via http://www.vpb.lt) is known for industrial sludge with over 38 % Fe ₂ O3, processing method by treating Siam with sulfuric acid, then washing with water, filtering the precipitate by oxidation and aging. The precipitate is then washed and filtered again, then heated and milled to give a red pigment, which is used for staining ceramic products and high temperature glazes. This process requires many processing steps, consumes a large amount of industrial water, which again pollutes the environment, and fine dispersion filtration reduces the efficiency of the process.

Patent RU No. 23292204 (TPK 8 C03C 1/04, Publication Bulletin 2008, No. 20) describes a process for preparing a brown pigment from a batch having the following composition: chromium oxide 20-30%, zinc oxide 5-10%, red slag (clay) and bauxite wastes containing by weight: silica 9.5-11.1; titanium dioxide 4.4-5.6; alumina 17-19; iron oxide 39-42.9; calcium oxide 7.6 -9.5; sodium oxide 6.2-6.9; other 7.8-10.5) 25-36; dolomite 35-40. The above components are ground to pass through sieve no. 0063, dosed and mixed. The resulting mass is heated at 850-950 ° C in an oxidizing environment. In this process, a high percentage of the expensive chromium oxide and a small amount of red slurry consumed are present.

According to the method for processing the sludge, the closest method to the present invention is a method for processing the sludge into the brown pigment described in patent no. 3949 (TPK 7 C09C 1/24). The essence of the invention is that the slurry obtained by treating wastewater with FFH and containing at least 60% Fe ₂ O 3 is mixed with 85% phosphoric acid in a molar ratio of Fe ₂ O 3: P2O 5 equal to 1.00: (0.2-0, 3), then the product is dried and heated to 400-700 ° C. The pigment obtained at this temperature has a dark brown color and a red-brown color at 600-700 ° C. Oil absorption - 60-100 g / 100 g linseed oil; coverage - 8-13 g / m ² ; color brightness (p) - 12-13%, color purity (P) - 38-44%, dominant wavelength λ v

597-598 nm. The disadvantages of this process are that the resulting brown pigments have a limited range of shades, high oil absorption and low color brightness and color purity, since the amounts of Ni, Cr and Cu compounds present in this process can form products with a brown color.

The object of the present invention is to process a slurry obtained by treating wastewater using FFH into pigment materials having a wide range of red-brown colors and having high dyeing properties.

The object is achieved by further modifying the resulting slurry with a soluble zinc salt, in part, zinc sulfate. The addition of zinc sulphate to the slurry in a molar ratio of 1: (0.10-0.30) and exposure to temperature creates the possibility of crystalline hematite (a Fe ₂ C> 3) phase and prevents the formation of magmatite, magnetite, ferrite, which have dark brown. Hematite, depending on its dispersion and crystallinity, has a broad spectrum of red-brown hues. Zincite present in slag heat treatment products positively affects the color characteristics of the pigment.

Thus, the following advantages of this method can be noted:

1. Modification of the slurry by soluble zinc salt purposefully yields various red shades of red-brown pigment with higher purity and clarity of color.

2. The present process enhances the ability to use sludges of various chemical compositions containing significant amounts of Ni, Cr, Cu and other heavy metal compounds.

The distinguishing features of the present invention are as follows:

1. Modifier type - use of soluble zinc salt.

2. The weight ratio of slurry to soluble zinc salt, calculated as Fe2O3: ZnO in this case, is 1.0: (0.10-0.30).

3. Heat treatment of sludge in the temperature range 800-850 ° C.

The distinguishing features of the invention are explained in more detail below.

1. Modifier type.

Experimental data show that the thermal treatment of sludge, which contains more zinc compounds than nickel, chromium and copper, results in products mainly containing iron oxides (hematite) and zinc oxide (zincite), which are colored in various shades of red, red-brown. color. It depends on the ratio of crystalline phases, their dispersion and crystallinity. The ratio of crystalline phases in temperature-treated products depends on the composition of the initial sludge and the amount of modifier used. Therefore, zinc sulphate should be considered as a modifier which structurally modifies pigment materials and which acts on the physico-chemical changes that occur during the thermal treatment of the sludge and on the color characteristics of the resulting materials.

The addition of zinc salt to the sludge has a positive effect on the formation of hematite as the main phase, since spinel structures with a static distribution of two and three charge cations in octahedral lattice nodules are not formed in this case. From these data, it can be concluded that the color characteristics of the sludge processing products are directly dependent on their phase composition, which in turn is determined by the chemical composition of the initial sludge, partly by the presence of metal compounds, and in particular zinc.

2. The molar ratio of Fe ^ O ^ ZnO in this.

According to its chemical composition, the sludge obtained by treating wastewater using FFH can be presented as a mixture of iron oxohydrates with heavy metal compounds absorbed on their surface. As established by [By / mJiOBCKuc J.., EmeHKO JI.C. HccjieaoBaHHe npoøecca h προΛγκτοΒ TepMoo6pa6oTKH mjiaMOB, nojiyHeHHBix npn ouncTKe ctohhbk fault c πομοπιμο φερροφερρΗΓΗΑροχοπ »// JKyp. 2004. T. 77. Bbm. 9. C. 1520 5

1524], the phase composition of the sludge heat treatment products depends on the zinc, nickel, copper, chromium compounds it contains. In the presence of Fe 2 O 3: ZnO = 1: (0.1-0.30), the heat treatment products at 800-850 ° C are predominantly hematite (Table 1-8, examples). The resulting products have a red-brown color. Reducing the amount of zinc compounds in this zinc oxide to FezCb: ZnO molar ratio below 10.0 results in spinel structures and products with an impure brown tint (Table 810 examples). Increasing the amount of zinc compounds in the initial process contributes to the crystalline phases of hematite, zincite during the temperature treatment and improves the coloring characteristics of the resulting pigments (Table 4, Examples 11 and 12).

The addition of more than 0.3 moles of zinc compounds converted to zinc oxide per mole of FezCb to the slurry results in increased zinc content, reduced iron (III) content in the heat treatment products, resulting in a slight decrease in the color purity of the iron-containing pigments (Table 11 and 12 examples).

3. Temperature range,

The temperature of the sludge treatment has a major influence on the color of the resulting products. A number of chemical, physico-chemical and phase transformations take place during the heating of the sludge, which influence the composition of the heat treatment products and their coloring characteristics. The heating of the sludge is accompanied by the decomposition of H2O, crystallization of iron oxides, and formation of ferrites. The crystallization of hematite (a Fe2³3), which is red in color, causes an increase in the color purity of the products obtained.

According to experimental data, the slurry, when heated to 700 ° C, has crystalline phases of magemite (γ Fe 2 3 3) or magnetite 3 3 () 4), depending on the nickel, chromium, copper or zinc compounds it contains. The transition of magemite (γ Fe2C> 3) and magnetite ^ 3 () 4) to hematite (a Fe2Ū3) occurs at 800-850 ° C. Therefore, raising the slag treatment temperature to 800-850 ° C facilitates the obtaining of red-tinted products which have a higher brightness and purity of the red. Heating the slurry to 900 ° C and above results in particle sintering and formation of agglomerates, which results in deterioration of the coloring and dyeing performance of the resulting pigments.

In order to determine the use of the resulting products from heat-treated slag as inorganic pigments, tests were carried out on pigment characteristics such as coating and oil absorption. Coatings are known to be quantified as grams of pigment mass required to provide a uniform coating (g / m ² ) per 1 m ^{2 of} surface to be painted. The coverage of inorganic pigments ranges from 10 to 90 g / m ^{2 for} natural iron pigments and 4-7 g / m ^{2 for} synthetic reds [KopcyHCKHH JI. Φ., KajiHHCKaa TB, CTenHH CH // HeopraHunecKite πηγμ6ητβι: CnpaBOHHHK. Cn6: Xhmm, 1992, 336c.]. The coverage of the heat-treated slag pigments was found to vary within a fairly narrow range of 11 to 17 g / m ² (Examples 1-8 in Table) and to the same level of coverage as the prototype.

Oil absorption is one of the main indicators of pigment quality. Oil Susceptibility is the grams of linseed oil needed to coalesce pigment powder to convert 100 g of powder into a non-stick paste (g / 100 g). This ratio is 47-56 g / 100 g for the resulting pigments (Examples 1-8 in Table). This is slightly higher than the red and brown iron-containing natural and synthetic pigments with an oil-bearing capacity of 20-50 g / m ² [KopcyHCKHH JI. Φ., KajiHHCKaa TB, OrenHH CH // HeopraHHHecKue ΠΗΓΜβΗΤΒΐ: CnpaBOHHHK. ΟΠ6 .: Xhmhs, 1992, 336 c.], But not less than the oil resistance of the prototype (Examples 13 and 14 in Table).

The invention is illustrated by the following examples, the results of which are shown in the following table.

Examples.

The initial slurry obtained by treating the effluent using FFH (heterocoagulation) had the following composition, by weight: Fe ₂ ? 3 -7.74; FeO = 0.92; ZnO - 0.28; CuO 0.25; Ni 0.10; CaO = 0.17; Cr ₂ O ₃ - 0.19; P ₂ O ₅ - 0.08; H ₂ O 87.7 (the remaining 2.57% consists of water chemically bonded to coordination metals through OH groups).

The slurry is homogenized in a molar ratio of modifier phosphoric acid Fe ₂ O 3: P ₂ Os to 1: 0.2 as described in the prototype and left to settle. The phosphorus-containing slurry is then supplemented with a modifier, soluble zinc salt, partially, ZnSC> 4 '7 H ₂ O. The amount of zinc sulfate added is calculated to give a ratio of Fe ₂ O 3: ZnO of 1: (0,1-0). , 3). The modified slags are homogenized and left to stand for 5-10 hours and then heated slowly to 800-850 ° C. After production, the products are crushed and their chemical, phase and dispersion composition and coloring properties are determined.

The phase composition of the products obtained was determined on a Bruker AXS (Germany) 08 Advance diffractometer. Spectrophotometer ΟΦ-18 (Russia), equipped with “B” radiation source, was used to determine the color characteristics of pigments.

The coloring properties (pigmentation and oil resistance) of pigments are determined according to standard procedures [KopcyHCKHH JI. Φ., KajiHHCKaa T. B., CTenHH C. H. // HeopraHHuecKHe πΗΓΜβΗΤΒΐ: CnpaBOHHHK. CII6: Χημηη, 1992, 336 c.].

Results of experimental studies

Bandy mo No. Modify rius Fe ₂ O ₃ : Zn 0 molar ratio Treatment temperature, ° C Colors characteristics Coloring technical characteristics Colors visual character- clover Phase composition P ⁺ ,% p, % λ, nm Dengmi a mum, g / m ² Sensitivity for oil, g / 100g 1 ZnSO4-7H2O 1: 0.10 800 37.5 14.3 603 11th 49 red Brown hematite, magnetite 2 ZnSO4-7H2O 1: 0.17 800 40.0 17.0 603 12th 47 red Brown hematite, magnetite 3 ZnSO4-7H2O 1: 0.25 800 40.5 17.6 603 12th 50 red Brown hematite, zincitis 4 ZnSO47H2O 1: 0.30 850 42.0 17.9 603 14th 52 Red hematite, zincitis 5 ZnSO4-7H2O 1: 0.17 900 39.5 16.7 599 17th 50 dark Red hematite, franklinitis 6th ZnSO4-7H2O 1: 0.25 850 41.5 17.5 602 16th 56 Red hematite, magnetite 7th ZnSO4-7H2O 1: 0.10 850 39.5 15.3 603 13th 50 red Brown hematite, magnetite 8th ZnSO4-7H2O 1: 0.10 900 40.5 17.0 602 16th 45 uncleanly red Brown hematite, franklinitis 9th Without modifier 800 30.0 14.0 605 10th 60 uncleanly dark Red hematite, the Magemite 10th Without modifier 900 25.5 10.7 605 18th 56 uncleanly dark Red hematite, the Magemite 11th ZnSO4'7H2O 1: 0.35 800 40.0 17.0 599 15th 50 Red hematite, zincitis 12th ZnSO4-7H2O 1: 0.35 900 38.0 16.5 601 17th 53 Red hematite, franklinitis 13th Prototype * 400 40.0 13.4 600 13th 92 Brown hematite, the Magemite 14th Prototype * 700 44.0 13.0 598 8th 60 red Brown hematite, the Magemite

P ⁺ color purity; p ⁺⁺ color purity; * Fe ₂ O ₃ : ZnO molar ratio 1: 0.2.

Claims (1)

DEFINITION 1. A process for converting iron-containing sludge obtained by wastewater treatment by heterocoagulation into a pigmented material by mixing the sludge with a modifier, followed by drying and heat treatment, characterized in that the modifier additionally uses soluble zinc salt in an amount corresponding to the following Fe ₂ O 3: At a ZnO molar ratio of 1: (0.1-0.3) mixed with phosphorus-containing sludge, the resulting mixture is homogenized, dried, heat-treated at 800-850 ° C to give a red and red-brown pigment.