RU2103387C1 - Method of recovering zinc from zinc-containing waste - Google Patents

Abstract

FIELD: waste disposal. SUBSTANCE: zinc-containing materials, in particular, zinc cuttings, without preliminary crushing, are placed into water and to the mixture obtained, phosphoric acid is added under stirring at zinc/phosphorus pentoxide/water ratio (0.94-1):(3.15-3.88):(1.56- 3.02). Zinc is recovered at 20-45 C. EFFECT: facilitated recovery procedure. 3 cl

Description

 The invention relates to a technology for the processing of zinc-containing raw materials, in particular zinc chips - waste production of galvanizing wire.

 The composition of zinc chips in accordance with GOST 1639-78 (grade - 1,2,3).

 There is a method of extracting zinc from spent zinc oxide catalysts for desulfurization (zinc oxide hydrogen sulfide scavengers) by dissolving them in sulfuric acid, filtering, neutralizing the filter to a pH of 2.5 - 3, subsequent precipitation and separation of zinc pyrophosphate from the mother liquor. The method is complicated due to the multi-stage process, the presence of difficult-to-recover production waste in the form of sodium sulfate, and is also characterized by a low degree of zinc extraction.

Closest to the proposed one is a method of extracting zinc from spent zinc oxide-zinc absorbers of hydrogen sulfide by treating it with an aqueous solution of a mixture of phosphoric, nitric and hydrofluoric acids with a ratio of P ₂ O ₅ : NO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$ : SiF $\genfrac{}{}{0ex}{}{\text{2-}}{\text{6}}$ : H ₂ O = 1: (0.85 - 1.87): (0.0168 - 0.0178): (2.099 - 3.071). In this case, the absorber is introduced into the process in an amount of 0.80 - 9.5 of the stoichiometric value of the sum of cations necessary for the formation of monosubstituted acid salts, at a rate of 152 - 178.6 kg ZnO / m ³ . Processing is carried out for 1 to 3 hours, while using a mixture of acids at 20 - 30 ^o C.

The disadvantages of the method are:
insufficiently high degree of zinc extraction;
laboriousness and high cost (use in the complex of H ₃ PO ₄ , HNO ₃ and H ₂ SiF ₆ );
harmful working conditions.

 The objective of the invention is the creation of such a method of extracting zinc from zinc-containing waste products, which increases the degree of extraction of zinc, expanding the raw material base of zinc-containing raw materials, improving working conditions, reducing the complexity of the process and reducing costs by replacing the mixture of mineral acids with phosphoric acid.

This task is achieved by the fact that zinc chips are introduced into water without preliminary grinding and phosphoric acid is introduced into the resulting mixture with constant stirring in the following ratio Zn: P ₂ O ₅ : H ₂ O = (0.94 - 1): (3.15 - 3.88): (1.56 - 3.02) at a speed of 4000 l / h. The temperature of the working mixture is 20 - 45 ^o C. An additional supply of heat for the most complete extraction of zinc is not required.

 The degree of zinc extraction in the marketable product 94.5 - 97%.

 Zinc monophosphate obtained as a result of processing aqueous pulp of zinc chips with phosphoric acid is used in the production of phosphating concentrates, which significantly reduces the complexity of their production, improves working conditions, and reduces the cost of phosphating concentrates.

Example 1. In a reactor with a volume of 10 m ³ serves 2420 l of water, include mixing and pour 750 kg of zinc shavings. Next, 2988 L of phosphoric acid is introduced into the resulting mixture at a rate of 4000 L / h with a ratio of components Zn: P ₂ O ₅ : H ₂ O = 0.94: 3.15: 3.02. The temperature of the working mixture rises to 20 ^o C.

 The degree of zinc extraction is 96.5%.

Example 2. In a reactor with a volume of 10 m ³ serves 1825 l of water, include mixing and fall asleep 780 kg of zinc shavings. Next, 3340 L of phosphoric acid is introduced into the resulting mixture at a rate of 4000 l / h with a ratio of components Zn: P ₂ O ₅ : H ₂ O = 0.97: 3.52: 2.28. The temperature of the working mixture increases to 40 ^o C.

 The degree of zinc extraction into the solution from zinc chips is 97%.

Example 3. In a reactor with a volume of 10 m ³ serves 1250 l of water, include mixing and load 800 kg of zinc shavings. Next, 3670 l of phosphoric acid is introduced into the resulting mixture at a rate of 4000 l / h with a ratio of components Zn: P ₂ O ₅ : H ₂ O = 1: 3.88: 1.56. The temperature of the working mixture increases to 45 ^o C.

 The degree of zinc extraction is 96%.

Example 4 (prototype). Into a reactor with a capacity of 10 m ³ into a mixture of phosphoric, nitric, hydrofluoric acid and water containing 2450 kg of 75.94% H ₃ PO ₄ , 2070 kg of 53.78% HNO ₃ , 121 kg of 21% H ₂ SiF ₆ and 2831 kg of H ₂ O at a ratio of P ₂ O ₅ : NO ₃ : SiF ₆ : H ₂ O = 8: 0.85: 0.0168: 2.099 at 20 ^o C and mechanical stirring add the spent zinc oxide hydrogen sulfide scavenger in an amount 0.80 from the stoichiometric value of the sum of cations to the formation of nitrates, silicofluorides of monosubstituted phosphates at a rate of 152 kg ZnO / h.m ³ . The temperature of the mixture of acids and water after entering the scavenger is 30 ^o C. The duration of the process of decomposition of the scavenger is 1 hour. The degree of zinc extraction into the solution from the scavenger is 90%.

 Implementation of the proposed method will allow to effectively extract zinc from zinc-containing waste products of galvanizing wire - - zinc shavings, abandon expensive raw materials - zinc oxide in the production of phosphate concentrates, reduce energy consumption, material and labor costs in the production of phosphating concentrates, improve working conditions.

Literature
1. Mertzin N., Sims H., Konerding K. On the use of chain components of catalysts for the production of phosphates for special purposes. - Chemie-Technik 1986, T. 38, No. 6, p. 244 - 245.

 2. RF patent N 1712434 (prototype).

Claims (3)

1. A method of extracting zinc from zinc-containing waste, comprising treating the aqueous pulp of zinc-containing waste with a phosphoric acid reagent, characterized in that the waste pulp is treated with phosphoric acid at a rate of introducing it into the pulp of 4000 l / h and the following ratio of components:
Zn P ₂ O ₅ H ₂ O (0.94 1) (3.15 3.88) (1.56 3.02).  2. The method according to p. 1, characterized in that the zinc chips are used as zinc-containing raw materials. 3. The method according to p. 1, characterized in that the extraction of zinc is carried out at a temperature of 20 45 ^o C.