CN1141252C

CN1141252C - Method for directly synthesizing auro-potassium cyanide by controlling level

Info

Publication number: CN1141252C
Application number: CNB001102192A
Authority: CN
Inventors: 张东山
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-03-20
Filing date: 2000-03-20
Publication date: 2004-03-10
Anticipated expiration: 2020-03-20
Also published as: CN1314307A

Abstract

The present invention relates to a method for directly synthesizing gold potassium cyanide by controlling potential. Potassium cyanide and hydrogen peroxide are gradually added into a reaction container at a certain speed. KAu (CN)2 prepared by the method has the advantages of high speed, high efficiency, good quality, little investment and low production cost.

Description

Method for directly synthesizing potassium aurous cyanide

(I) technical field

The invention relates to a method for preparing potassium aurous cyanide, in particular to a method for directly synthesizing the potassium aurous cyanide by adopting potential control.

(II) background of theinvention

The production of potassium aurous cyanide mostly uses ion exchange membrane electrolysis method abroad, and the process flow is as follows: raw material granulation, diaphragm electrolysis, evaporation concentration, cooling crystallization, centrifugal separation and drying. It features high quality of product, suitable for large-scale production, and the key point of electrolysis is the performance of ion exchange membrane. The manufacturing technology of the film is proprietary to manufacturers and is not mastered at home. The high-quality potassium aurous cyanide used in China still needs to be imported at present.

The domestic production of aurous potassium cyanide mostly adopts a chemical method, and the process flow is as follows: dissolving aqua regia, removing nitrate, diluting, precipitating ammonia water, evaporating to remove ammonia, cooling, crystallizing, centrifugally separating and drying. Its disadvantages are long process, high cost, poor product quality and purity of 98-99%.

The reaction formula for directly synthesizing the potassium aurous cyanide by gold, potassium cyanide and hydrogen peroxide is as follows:

the existence of this reaction is well known to those skilled in gold dressing and is used in cyanidation leaching of gold ores. However, so far, it has only been used to obtain KAu (CN)₂Is not applicable to KAu (CN)₂And (5) actual production of the product.

Using gold, KCN, H₂O₂Direct Synthesis of KAu (CN)₂(from the book of "gold production technology" 1980 of Sichuan people Press, page 248) there are mainly two difficulties:

1. unstable hydrogen peroxide, and decomposition in the presence of gold:

H₂O₂the higher the concentration, the larger the surface area of gold and the faster the decomposition rate. For example, gold powder is added to 1% H₂O₂In (1), H can be observed₂O₂Is decomposed violently.

2. Side reactions affecting product quality

When the concentration of potassium cyanide and hydrogen peroxide is high, impurities such as trivalent gold salt and cyanate can be generated by side reaction, and the product quality is influenced. For the reasons mentioned above, this method has not been used for the practical production of potassium aurous cyanide so far.

Disclosure of the invention

The invention aims to provide a method for directly synthesizing aurous potassium cyanide by adopting gold, potassium cyanide and hydrogen peroxide.

Adopts the technical proposal

The direct synthesis process of potassium aurous cyanide includes adding potassium cyanide and hydrogen peroxide solution into reactor at certain speed and controlling the gold potential in the reaction process of-400-800 mv.

The gold potential control can be realized by installing a gold electrode and a saturated calomel electrode in the reaction vessel. The gold electrode is connected with the positive input end of a potentiometer through a lead, and the saturated calomel electrode is connected with the negative input end of the potentiometer through a lead. Production of KAu (CN)₂When in use, gold powder Au and pure water H are added into a reaction vessel₂Heating to 50-80 deg.C, stirring, measuring and displaying the gold potential in the reaction process with potentiometer, adding KCN and H₂O₂By adding KCN and H₂O₂The gold potential is controlled within the range of-400 to-800 mv, and the KCN and H are stopped to be added₂O₂Stirring was continued until the reaction was completed, and KAu (CN) was added to the resulting aqueous solution₂The concentration can be up to more than 30%. Filtering the mother liquor while it is hot, cooling for crystallization, centrifugally dewatering, washing and drying to obtain high-quality KAu (CN) with purity of more than 99.9%₂And (5) finishing.

The gold potential is controlled between-600 mv and-700 mv, which is the best range for practical production.

Gold powder, gold flakes or gold fine particles are used in actual production. H₂O₂KCN uses concentrated solution to increase mother liquor concentration; the reaction is carried out at a higher temperature to increase the reaction rate and the mother liquor concentration.

The above KCN may be partially substituted with HCN.

From The reaction formula for the formation of potassium aurous cyanide shows that potassium aurous cyanide KAu (CN)₂While also generating KOH. If half of the KCN is replaced with HCN, then:

from the above equation, it can be seen that KAu (C) is produced by using 50% KCN and 50% HCNN)₂In this case, the production of KOH can be avoided, i.e., only KAu (CN) is present in the mother liquor produced₂Is ideal KAu (CN)₂And (4) mother liquor.

Compared with the prior art, the invention has the following advantages:

1. can obtain high concentration of KAu (CN)₂The production speed of the mother liquor is high, and the efficiency is high;

2. compared with an electrolytic method, the method does not need to use a special ion exchange membrane, has small equipment investment and low production cost;

3. compared with chemical method, the consumption of reagent is less and the quality of product is high.

(IV) description of the drawings

FIG. 1 is a schematic diagram of a reaction vessel equipped with a gold electrode and a saturated calomel electrode.

(V) detailed description of the preferred embodiments

Example (b):

adding 1000g of gold powder and 2000mL of pure water into a reaction container 1 provided with a stirrer 5; heating to 60 deg.C, stirring, measuring and displaying the gold potential in the reaction process with saturated calomel electrode 2, gold electrode 3, and potentiometer 4, adding 30% H into the reaction container 1₂O₂Adding 40% KCN aqueous solution at a speed of 10-20 mL/min, adding KCN when the gold potential is higher, and H when the gold potential is lower₂O₂Controlling the gold potential between-600 mv and-700 mv, adding KCN with the amount 1.1 times of the theoretical amount in total, and continuing stirring after stopping adding liquid to ensure that the reaction is complete. The resulting mother liquor KAu (CN)₂The medium concentration can reach more than 30 percent. Filtering the mother liquor while it is hot, cooling for crystallization, centrifugally dewatering, washing and drying to obtain the gold methylene cyanide KAu (CN) with purity of more than 99.9%₂。

Claims

1. The method for directly synthesizing the potassium aurous cyanide is characterized by comprising the following steps of: can be straightObtaining a high concentration of KAu (CN)₂Solution: adding gold powder Au and pure water H into a reaction vessel (1)₂Heating to 50-80 ℃ and stirring; in a reaction container (1), potassium cyanide and aqueous hydrogen peroxide are gradually added at a certain speed and continuously stirred, and KCN and H are added in the reaction process₂O₂Controlling gold potential to-400-800 mv, obtaining potassium aurous cyanide mother liquor after reaction, filtering the potassium aurous cyanide mother liquor while the mother liquor is hot, cooling and crystallizing, centrifugally dewatering, washing and drying to obtain KAu (CN)₂And (5) finishing.

2. The method for directly synthesizing aurous potassium cyanide according to claim 1, characterized in that the gold potential is-600 to-700 mv.

3. The process for the direct synthesis of potassium aurous cyanide according to claim 1, characterized in that less than 50% of the KCN used can be replaced by HCN.

4. The method for directly synthesizing aurous potassium cyanide according to claim 1, characterized in that the gold potential is measured by installing a saturated calomel electrode (2) and a gold electrode (3) in a reaction vessel (1), the saturated calomel electrode (2) is connected with the negative input end of a potentiometer (4) through a lead, and the gold electrode (3) is connected with the positive input end of thepotentiometer (4) through a lead.

5. The method for directly synthesizing aurous potassium cyanide according to claim 1, characterized in that 1000g of gold powder and 2000ml of pure water are added into the reaction vessel (1), heated to 60 ℃, stirred, and 30% of H is added into the reaction vessel (1)₂O₂The aqueous solution is added with 40 percent KCN aqueous solution at the speed of 2-40 mL/min, the speed is 10-200 mL/min, and the gold potential of the gold electrode (3) is controlled between-600 mv and-700 mv.