RU2259347C1 - Method of production of zinc oxalate dihydrate - Google Patents

Abstract

FIELD: updating of process of production of zinc oxalate dihydrate.

SUBSTANCE: product obtained by this method may be used as pigment for production of catalysts of synthesis of inorganic and organic substances, manufacture of ceramic articles and production of oxide and other compounds of zinc. Proposed method includes preparation of reaction solution containing zinc (II) and oxalate, crystallization of target product, separation of sediment from solution and drying the sediment; reaction solution is prepared by mixing the solution of zinc plating process and oxalate-containing reagent; use is made of used solution of zinc plating process and reaction solution containing zinc (II) and oxalate at mole ratio of 1.0: (0.8-3.0) is prepared.

EFFECT: low cost of process at retained purity; possibility of utilization of toxic waste of zinc plating process.

12 cl, 7 ex

Description

The invention relates to the field of chemical technology of organic compounds, in particular to a method for producing zinc oxalate dihydrate, which can be used as a pigment, for the preparation of catalysts, ceramic materials, zinc oxide and other zinc compounds.

A known electrochemical method for producing zinc oxalate, consisting in the anodic dissolution of metallic zinc in an aqueous solution of oxalic acid at a temperature of 60-70 ° C (USSR Author's Certificate No. 1100824, class C 07 C 55/07, C 25 V 3/12, C 07 F 3/06, publ. 2003). The disadvantage of this method is the need for additional costs for the reagent - zinc metal and additional costs for electricity.

A known chemical method for producing crystalline zinc oxalate hydrate, based on the reaction of zinc acetate with oxalic acid (Russian Patent No. 2206508, CL 01 G 9/02, publ. 2003).

A known method of producing zinc oxalate dihydrate, which consists in the preparation of a reaction solution containing zinc salt and oxalate, followed by crystallization of the product (Remy G. Course of inorganic chemistry. T.2. - M .: Mir, 1974, S.442).

A known method of producing zinc oxalate dihydrate by crystallization from an aqueous solution containing zinc chloride and oxalic acid or sodium oxalate (Kuzmina I.P., Nikitenko V.A. Zinc oxide. Production and optical properties. - M .: Nauka, 1984, S. 10).

A known method of producing zinc oxalate dihydrate by crystallization from an aqueous solution containing zinc sulfate and sodium oxalate at room temperature (V.P. Kornienko // Ukrainian Chemical Journal, 1957, V.23, No. 2, S. 159). In this method, the reagents are taken in a molar ratio of zinc sulfate: sodium oxalate equal to 1.0: 1.0.

A known method of producing zinc oxalate dihydrate, comprising preparing a reaction solution containing zinc (II) and oxalic acid, crystallizing the product at room temperature, separating the precipitate from the solution by filtration (Deyrieux R., Berro Ch., Peneloux Ay / Bulletin de la Societe Chimique de France, 1973, No. 1, P.25). To prepare the reaction solution in this method, a zinc salt is used.

Also known is a method of producing zinc oxalate dihydrate, including preparing a reaction solution containing zinc (II) and oxalate, crystallizing the product, separating the precipitate from the solution and drying the precipitate (Vesnovsky B.N. // Journal of Inorganic Chemistry. 1976. V.21. No. 10. S. 2651). In this method, the reaction solution is prepared by mixing aqueous solutions of zinc sulfate and sodium oxalate with concentrations of 1 mol / l each at room temperature.

The disadvantage of the above chemical methods for producing zinc oxalate dihydrate is the need for additional costs for the reagent - zinc salt.

A known method of producing zinc oxalate dihydrate, including the preparation of a reaction solution containing zinc (II) and oxalate, crystallization of the product, separation of the precipitate from the solution (Anorganicum (edited by Colditz L.) T.2. - M .: Mir, 1984, C .590). The reaction solution is prepared by adding a 1 mol / L concentration of an aqueous solution of a reagent — ammonium oxalate — heated to 70 ° C to a 1 mol / L concentration of an aqueous solution of zinc chloride heated to the same temperature. The reaction solution contains zinc (II) and oxalate in a molar ratio of 1.1: 1.0. The precipitate was separated from the solution by filtration on a suction filter under reduced pressure. The method allows to obtain pure zinc oxalate dihydrate of the composition ZnC ₂ O ₄ · 2H ₂ O in high yield. The disadvantage of this method is the need for additional costs for heating the solutions and the reagent is zinc chloride.

Closest to the claimed invention is a method of deposition of zinc ions with the formation of a precipitate of zinc oxalate, comprising preparing a reaction solution containing zinc (II) and ammonium oxalate, crystallization of zinc oxalate, separating the precipitate from the solution (Jackson JL US 3887445, class C 23b 5 / 10, C 23b 5/12, B 01d 9/00, publ. 1975). In the prototype method, a reaction solution is prepared by adding ammonium oxalate monohydrate or a composition of oxalic acid dihydrate and ammonium hydroxide (molar ratio of substances in the composition 1: 2) to a galvanizing solution. The method is based on the following reactions:

The reaction solution contains zinc (II) and oxalate in a molar ratio of about 1.0: 0.53 (corresponding to stoichiometric with respect to the excess amount of zinc (II), which should be precipitated in the form of oxalate). The prototype method has several disadvantages that impede the obtaining of a technical result, which is ensured by the claimed invention. The target product is contaminated with adsorbed fats, oils and products of electrochemical decay of clarifying additives, which interferes with its further use without further purification. The degree of deposition of zinc (P) from the solution is approximately 55%, which does not allow for deep cleaning of the spent zinc solution from zinc ions. The prototype method involves the deposition of zinc ions from zinc solutions containing zinc chloride, ammonium chloride and having a pH from 4.0 to 7.5, but does not allow to obtain zinc oxalate dihydrate by processing spent zinc solutions with a high content of mineral acids or alkalis.

When creating the claimed invention, the task was to reduce the material costs of obtaining zinc oxalate dihydrate, to increase the purity and yield of the target product, to expand the assortment of zinc-containing wastes of galvanic production used to obtain zinc oxalate dihydrate, to increase the degree of release of zinc ions from spent galvanizing solutions.

The problem is solved in that the method of producing zinc oxalate dihydrate includes the preparation of a reaction solution containing zinc (II) and oxalate, crystallization of the target product, separation of the precipitate from the solution and drying of the precipitate, the reaction solution being prepared by mixing a galvanizing solution and an oxalate-containing reagent. New in this method is that a used galvanic galvanizing solution is used and a reaction solution is prepared containing zinc (II) and oxalate in a molar ratio of 1.0: (0.8-3.0). As a spent galvanizing solution, it is desirable to use a solution containing zinc sulfate, sulfuric acid, or a solution containing zinc sulfate, sodium sulfate, aluminum sulfate, or a solution containing zinc sulfate, ammonium chloride, surfactants, boric acid, or a solution containing zinc chloride, ammonium chloride, surfactants, urotropin, ammonium acetate, or a solution containing zinc (II), sodium hydroxide, surfactants. As a reagent, it is preferable to use oxalic acid, sodium oxalate, potassium oxalate or ammonium oxalate or their aqueous solutions with a mass fraction of from 5 to 50%. As a reagent, it is desirable to use production waste containing oxalic acid, sodium oxalate, potassium oxalate or ammonium oxalate. It is advisable to prepare a reaction solution with a pH of from 0.5 to 8.5.

A method of producing zinc oxalate dihydrate is to prepare a reaction solution by mixing the spent galvanizing solution containing zinc (II) and a reagent containing oxalic acid or oxalate in an amount providing a molar ratio of zinc (II): oxalate equal to 1.0: (0.8-3.0), adjusting (if necessary) the pH of the reaction solution, crystallizing zinc oxalate dihydrate, separating the precipitate from the solution, washing (if necessary) the precipitate with a solvent and drying the precipitate.

The method for producing zinc oxalate dihydrate is based on reactions, for example:

In the inventive method for producing zinc oxalate dihydrate as a zinc-containing reagent, it is desirable to use spent solutions of sulfate, ammonia, ammonia-urotropine, alkaline zinc zinc plating of carbon, stainless steel and cast iron containing zinc salt, sulfuric acid, sodium hydroxide, ammonium chloride and ammonium chloride some other substances (GOST 9.305-84 Metallic and non-metallic inorganic coatings. Operations of technological processes for producing coatings. - M .: Iz-in stan Dartov, 1988, P.45-52; OST 107.460092.001-86. Coated metallic and nonmetallic inorganic. Typical technological processes. Book 1.-M .: Iz-in standards, 1986, P.47-51), having the composition , eg:

Zinc Sulfate Heptahydrate 250-400 g / l Sulfuric acid 80-100 g / l

or

Zinc Sulfate Heptahydrate 200-250 g / l Sodium sulfate 50-100 g / l Aluminum sulphate 20-30 g / l Dextrin 8-10 g / l

or

Zinc chloride 15-35 g / l Ammonium chloride 200-300 g / l Boric acid 25-30 g / l Glue glue 1-2 g / l

or

Zinc chloride 55-70 g / l Ammonium chloride 200-220 g / l Dispersant NF 6-8 g / l The drug OS-20 4-5 g / l Urotropin 20-25 g / l Ammonium acetate 80-100 g / l.

To obtain zinc oxalate dihydrate as a zinc-containing reagent, you can also use the spent alkaline galvanizing solution of steel containing zinc (II), sodium hydroxide and surfactants having the composition, for example:

Zinc oxide 10-17 g / l Sodium hydroxide 90-120 g / l Brightening additives NBC-0, NBC-K 8-12 g / l

or

Zinc oxide 10-20 g / l Sodium hydroxide 130-150 g / l Polyethyleneamine 1-3 g / l Thiourea 0.8-1 g / l.

To obtain zinc oxalate dihydrate as a zinc-containing reagent, it is undesirable to use spent galvanic steel galvanizing solutions containing sodium cyanide, since in this case there is a danger of the release of highly toxic hydrogen cyanide into the atmosphere.

To obtain zinc oxalate dihydrate as an oxalate-containing reagent, reagents manufactured by the chemical industry and having a low cost are used: oxalic acid Н ₂ С ₂ O ₄ · 2Н ₂ O GOST 22180-76 or its water-soluble salts: sodium oxalate Na ₂ С ₂ O ₄ GOST 5839-77, potassium oxalate К ₂ С ₂ O ₄ · Н ₂ O GOST 5868-78, ammonium oxalate (NH ₄ ) ₂ C ₂ O ₄ · H ₂ O GOST 5718-78. In addition, some chemical and galvanic waste products containing oxalic acid and water-soluble oxalates can be used.

Thus, the claimed method allows to obtain zinc oxalate dihydrate using affordable and inexpensive reagents and at the same time to utilize galvanic and chemical waste.

To obtain zinc oxalate dihydrate in high yield in the reaction solution, it is desirable to establish a specific molar ratio of zinc (II): oxalate. Of solutions in which 1.0 mol of zinc (II) accounts for less than 0.8 mol of oxalate, zinc oxalate dihydrate is isolated in less than 60% yield, and the product may be contaminated with basic sulfate or basic zinc chloride. Of the solutions in which 1.0 mol of zinc (II) accounts for 1.0 or more moles of oxalate, pure zinc oxalate dihydrate is released with a high yield of zinc (II), however, with a large excess, oxalate is consumed unproductively, since it does not cause an increase the yield of the product, but, on the contrary, reduces the yield of the product due to the formation of soluble zinc (II) oxalate complexes. Based on this, to obtain zinc oxalate dihydrate in high yield, it is desirable to prepare a reaction solution containing zinc (II) and oxalate in a molar ratio of 1.0: (0.8-3.0). The desired molar ratio of zinc (II): oxalate in the reaction solution is established by adding to the spent galvanizing solution calculated by analyzing this solution for zinc (II) the amount of oxalic acid, sodium oxalate, potassium oxalate, ammonium oxalate or their mass aqueous solutions shares from 5 to 50%.

To obtain zinc oxalate dihydrate in high yield, it is desirable to set a certain pH value in the reaction solution. Zinc oxalate dihydrate is poorly soluble in water (Remy G. The course of inorganic chemistry. T.2. - M .: Mir, 1974, P.442), but its solubility increases sharply when the solution is acidified:

In an alkaline medium, zinc oxalate dihydrate is not released from the solution, since zinc (II) is bound to the hydroxocomplex:

or, in the presence of ammonia or ammonium salts in the solution, into the ammonia complex:

Based on this, to obtain zinc oxalate dihydrate in high yield, it is desirable to prepare a reaction solution with a pH from 0.5 to 8.5. The required pH of the reaction solution can be set by adding either bases (sodium hydroxide, potassium hydroxide, ammonia solution) or strong mineral acids (hydrochloric, sulfuric, nitric).

Example 1

To 10 ml of the spent solution of zinc sulphate of steel with a concentration of zinc (II) 80.4 g / l, sulfuric acid 89.7 g / l, with stirring, first add a solution of 1.92 g of ammonium oxalate monohydrate GOST 5712-78 grade 9 ml of water heated to 80 ° C, then a 25% aqueous solution of ammonia GOST 3760-79 grade “chda” is added dropwise until a pH of 3.2 is reached. After 3 days, the precipitate was filtered on a POR 40 glass filter under reduced pressure, washed on the filter with water first, then with acetone. The precipitate is dried in air at room temperature to constant weight. Yield 93.1%.

Found,%: Zn - 34.7; C ₂ O ₄ ^2- - 46.0.

Calculated for ZnC ₂ O ₄ · 2H ₂ O,%: Zn - 34.52, С ₂ O ₄ ^2- - 46.46.

Example 2

A solution of 2.06 is added to 100 ml of the spent solution of ammonia galvanizing steel with a concentration of zinc (II) of 9.7 g / l, ammonium chloride 240 g / l, boric acid 26 g / l, and glue-free glue 1.7 g / l. g oxalic acid dihydrate GOST 22180-76 grade "hch" in 5 ml of water heated to 90 ° C. To the resulting solution was added in portions of 0.5 ml of a 20% aqueous solution of sodium hydroxide until a pH of 3.7 was reached. After 1 day, the precipitate was filtered on a POR 40 glass filter under reduced pressure, washed with water and dried in air at room temperature to constant weight. Yield 96.9%.

Found,%: Zn - 34.6; C ₂ O ₄ ^2- - 46.3.

Example 3

To 100 ml of the spent solution of ammonia-urotropin galvanizing of steel with a concentration of zinc (II) 36.6 g / l, ammonium chloride 205 g / l, urotropin 26 g / l, ammonium acetate 84 g / l, dispersant NF 6.5 g / l, OS-20 preparation 4 g / l first add 100 ml of water, then 72 ml of an 8.0% aqueous solution of oxalic acid GOST 22180-76 grade “chda” are added with stirring and concentrated sulfuric acid GOST is added dropwise with stirring 4204-77 of the grade “chda” until a pH of 1.4 is reached. The solution is left for 3 days for crystallization. The precipitate formed is filtered off on a POR 40 glass filter under reduced pressure, washed first with water, then with acetone and dried in air at room temperature to constant weight. Yield 92.0%.

Found,%: Zn - 34.4; C ₂ O ₄ ^2- - 46.2.

Example 4

A solution of 22.2 oxalic dihydrate is added to 100 ml of the spent solution of galvanizing cast iron with a concentration of zinc (II) of 57.6 g / l, potassium chloride 190 g / l, boric acid 15 g / l, brightening additive Limeda 3 g / l acid GOST 22180-76 of the "chda" brand in 100 ml of water heated to 50 ° С. After 20 hours, the precipitate was filtered on a POR 16 glass filter under reduced pressure, washed with water and dried in air at room temperature to constant weight. Yield 87.7%.

Found,%: Zn - 34.2; C ₂ O ₄ ^2- - 46.1.

Example 5

To 50 ml of the spent solution of galvanizing steel with a concentration of zinc sulfate 112 g / l, sodium sulfate 55 g / l, aluminum sulfate 20 g / l, dextrin 8.5 g / l, with a stir, first add a solution of 7.67 g of potassium oxalate monohydrate GOST 5868-78 of the brand “h” in 100 ml of water, then concentrated nitric acid GOST 4461-77 of the brand “h” is added dropwise with stirring until a pH of 3.2 is reached. After 5 hours, the precipitate formed is filtered off on a POR 40 glass filter under reduced pressure, washed first with a solution of nitric acid with a concentration of 0.01 mol / L, then with water and finally with acetone. The precipitate is dried in air at room temperature to constant weight. Yield 97.3%.

Found,%: Zn - 34.0; C ₂ O ₄ ^2- - 46.0.

Example 6

100 ml of the spent solution of galvanizing steel with a concentration of zinc of 26.4 g / l, potassium chloride 200 g / l, boric acid 12 g / l is mixed with 100 ml of the spent solution of anodic oxidation of aluminum with a concentration of oxalic acid 45 g / l, sulfuric acid 8 g / l, aluminum 3 g / l. To the resulting solution, with the addition of 0.5 ml, 15% aqueous sodium hydroxide solution is added in portions of 0.5 ml until a pH of 2.3 is reached. The solution is left to crystallize for 2 days. The precipitate formed is filtered through a POR 40 glass filter under reduced pressure, washed first with water, then with ethanol and dried in air at room temperature to constant weight. Yield 94.2%.

Found,%: Zn - 34.6; C ₂ O4 ^2- - 46.0.

Example 7

To 50 ml of the spent alkaline galvanizing solution of steel with a concentration of zinc (II) 12.1 g / l, sodium hydroxide 140 g / l, bright-forming additives NBC-0, NBC-K 9 g / l, a solution of 1.28 g of dihydrate is added with stirring GOST 22180-76 oxalic acid grade “h” in 13 ml of water. Concentrated sulfuric acid GOST 4204-77 grade “h” is added dropwise to the resulting solution with stirring until a pH of 2.6 is reached, then 40 ml of water are added. After 1 day, the precipitate is filtered through a blue ribbon paper filter, washed with water until the washings react negatively to sulfate ions. The precipitate is dried in air at room temperature to constant weight. Yield 97.9%.

Found,%: Zn - 35.1; C ₂ O ₄ ^2- - 45.9.

Obtained in examples 1-7, zinc oxalate dihydrate is a colorless crystalline substance, poorly soluble in water, ethanol, acetone, acetic acid, soluble in aqueous solutions of ammonia and strong mineral acids.

As can be seen from the above examples, the claimed method allows to obtain in high yield zinc oxalate dihydrate, the composition of which exactly corresponds to the chemical formula ZnC ₂ O ₄ · 2H ₂ O. The material costs of obtaining zinc oxalate dihydrate are achieved by using zinc as a source (II ) spent galvanizing solutions of various compositions, including zinc sulfate and alkaline galvanizing, and the process at the optimum pH value and molar ratio of reagents. The claimed method allows for the effective cleaning of zinc (II) from spent galvanic galvanizing solutions, to protect the environment from toxic waste from galvanic production.

Claims (12)

1. A method of producing zinc oxalate dihydrate, comprising preparing a reaction solution containing zinc (II) and oxalate, crystallization of the target product, separating the precipitate from the solution and drying the precipitate, the reaction solution being prepared by mixing a galvanic galvanizing solution and a reagent containing oxalate, characterized in that they use the spent galvanizing solution and prepare a reaction solution containing zinc (II) and oxalate in a molar ratio of 1.0: (0.8-3.0). 2. The method according to claim 1, characterized in that the solution containing zinc sulfate, sulfuric acid is used as the spent galvanizing solution. 3. The method according to claim 1, characterized in that the solution containing zinc sulfate, sodium sulfate, aluminum sulfate is used as a waste galvanic galvanizing solution. 4. The method according to claim 1, characterized in that the solution containing zinc sulfate, ammonium chloride or potassium chloride, surfactants, boric acid is used as the spent galvanizing solution. 5. The method according to claim 1, characterized in that as the spent galvanizing solution is used a solution containing zinc chloride, ammonium chloride or potassium chloride, surfactants. 6. The method according to claim 1, characterized in that as the spent galvanizing solution is used a solution containing zinc chloride, ammonium chloride or potassium chloride, surfactants, boric acid. 7. The method according to claim 1, characterized in that as the spent galvanizing solution is used a solution containing zinc chloride, ammonium chloride or potassium chloride, surfactants, urotropine, ammonium acetate. 8. The method according to claim 1, characterized in that the solution containing zinc (II), sodium hydroxide, surfactants is used as the spent galvanizing solution. 9. The method according to claim 1, characterized in that oxalic acid, sodium oxalate, potassium oxalate or ammonium oxalate is used as a reagent. 10. The method according to claim 1, characterized in that the reagent uses aqueous solutions of oxalic acid, sodium oxalate, potassium oxalate or ammonium oxalate with a mass fraction of from 5 to 50%. 11. The method according to claim 1, characterized in that the reagent uses production waste containing oxalic acid, sodium oxalate, potassium oxalate or ammonium oxalate. 12. The method according to claim 1, characterized in that the prepared reaction solution with a pH of from 0.5 to 8.5.