JPS5942059B2 - Method for recovering Zn from Zn-containing materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering high-purity Zn by subjecting industrial waste to Zn-containing wet-wet treatment and simultaneously treating the waste.

In the present invention, "Zn right-hand motion" refers to various types of dust such as blast furnace dust and converter dust generated in steel works, scraps during the production of galvanized steel sheets, zinc oxides such as waste liquid sludge, or electricity generated in steel works, etc. Refers to all collected scattered dust generated from furnaces.

Iron oxide dust and scraps of Zn-plated steel sheets are generated in iron works, steel mills, etc., which process large amounts of ZnO, and it is extremely important to efficiently recover Zn and Fe from the perspective of effective resource utilization. be.

Among the conventional recovery methods, the dry method
The organic matter is mixed with reducing agent powder such as coke in a rotary kiln and heated to about 1200°C to reduce the low boiling point Z
Zn is evaporated and cooled and solidified outside the kiln to produce zinc oxide (Z
However, in this method, other dust particles are also scattered and collected at the same time, resulting in a decrease in purity.
n: Only a value of 30 to 50% can be obtained.

In addition, distillation methods have been used to collect evaporated Zn in a metallic state, but these methods have the drawbacks of consuming a large amount of thermal energy and causing considerable wear and tear on brick equipment and the like.

In addition, there is a wet method in which Zn is extracted using an alkaline aqueous solution, but this method has the drawback of increasing reagent costs.On the other hand, a method using acid causes other heavy metals, especially Fe, to be eluted at the same time. As a result, a large number of reagents are used, and the separation of different metals becomes complicated and time-consuming, making it difficult to apply to industrialization.

The object of the present invention is to solve these difficulties and provide a method for efficiently and inexpensively recovering Zn-containing high-purity Zn components and at the same time efficiently disposing of waste. Then, by adding ammonium thiocyanate aqueous solution to the Z0 anion, only the Zn component is extracted as a rhodan compound into the solution side and recovered as a highly pure Zn compound, and a large amount of Fe component is added while at the same time the Zn component is reduced to a minimum amount. The aim is to recycle the reduced insoluble matter as a source of iron production.

The method of the present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a process chart of an embodiment of the method of the present invention, and FIG. 2 is a graph showing the relationship between Zn (S CN )2 solubility and humidity in an extract obtained by extracting Zn with an ammonium thiocyanate aqueous solution. .

As shown in the process chart in Figure 1, in this example, the ammonia medium generated during cleaning of coke oven gas containing cyanide and sulfur in a steelworks is used as a Zn island-based ammonium thiocyanate aqueous solution. Cyanide waste liquid (commonly known as Rodan waste liquid, whose main component is ammonium thiocyanate (NH4SCN)) is added and mixed, and the mixture is heated at approximately 1°C to 70°C.
After stirring for a period of time, it is filtered, the insoluble residue containing Fe content is reused as a source for iron production, and the P solution is converted into a Zn content extract (Zn (S
CN)2 solution).

The reaction formula is 2NH,SCN+ZnO-+Zn(SCN
)2+2NH3+H20 (1) The amount of Rodan waste liquid used for extraction is required to be at least an equivalent amount that satisfies equation (1).

The extraction temperature may be room temperature, but due to the difference in solubility, heating will naturally result in faster extraction speed and higher extraction concentration.

Table 1 shows the extraction rate and the relationship between the Zn concentration in the extract and the temperature when the Zn component was extracted by adding Rodan waste liquid to the Zn, l-right movement.

As mentioned above, Zni is produced by utilizing Rodan waste liquid, which has no particular use and is ultimately incinerated as a pollution prevention measure.
This is a method that selectively transfers the dextral kinetics of n components to the liquid side in the form of Zn (SCN)2, and hardly any other metals, especially Fe, are eluted, and the Fe ions in the extract are only about a few tens of ppm. This is one of the key points of the method of the present invention.

Next, Z n (S CN
) In the present invention, the following three recovery methods (5), (B), and (Q) can be used to recover high-purity Zn compounds from the two solutions.

(A) Method: As shown in column (5) in the process chart of FIG. 1, first, the extracted Zn(SCN)2 solution is concentrated and primary cooling crystallization is performed.

As an example of cooling crystallization, for example, the solubility of Zn(SCN)2 in the P solution as shown in the graph of FIG. 2 is Zn(SCN)2 per 11 filtrate when the temperature of the filtrate is 70°C.
is 200 gr dissolved (at saturation) and 100 gr dissolved at 30°C.

Therefore, by lowering the temperature of the furnace liquid from 70°C to 30°C, 100 gr of Zn(SCN)2 is precipitated as crystals, and the crystalline Zn(SCN)2 has relatively coarse particles and is difficult to filter. Due to its good properties, solid-liquid separation can be easily achieved.

Next, this solid-liquid separated crystalline Zn(SCN) 2 is redissolved by adding a fresh aqueous ammonium thiocyanate solution, and a second cooling crystallization is performed to obtain highly purified crystalline Zn(SCN), which is purified compared to the first crystallization. )2.

By repeating this purification operation by redissolution and recrystallization, higher purity crystal Z n (S CN, ) 2 can be produced.

Table 2 shows the crystal Zn of the above first and second cooling crystallization.
An example of purity comparison of (S CN )z is shown.

(B) and (Q method, as shown in the process chart in Figure 1, extract Zn (S CN
) 2 solution) is heated and roasted and collected as Zn oxide (ZnO), and this collected crude Zn0 (containing impurities other than ZnO during the roasting dust collection) is converted into a mineral acid. A purification operation is carried out after dissolving the material.

The reaction formula for the above heating and roasting process is 2Zn(SCN)2+1102-+2ZnO+4CO2
+4NO+4S02... (2) The reaction formula for the mineral acid dissolution process is (when sulfuric acid or hydrochloric acid is used as the mineral acid). Purification is performed using a separation method.

The method of collecting crude ZnO by heating and roasting this extract is as follows.
Conventionally, the Rodan waste liquid used for extraction is ultimately incinerated, so there is no change in the amount of thermal energy required for treatment, making it an effective industrial treatment method.

) Method: As shown in column (B) of the process chart in Figure 1, lees, Z n
O is dissolved in mineral acids such as sulfuric acid and hydrochloric acid, and only the Zn component is preferentially extracted by adding an organic solvent, leaving other impurities in the aqueous solution, and the extracted Zn component is back-extracted with dilute acid to achieve high purity. As an example, crude ZnO is dissolved in hydrochloric acid and the pH is adjusted to 1 to 2. Ethylhexyl phosphoric acid is added to kerosene by about 10 to 20%. Add dissolved organic solvent and Z
Only n minutes are preferentially extracted.

The reaction formula is Zn2++2R-H-+R2Zn+2H+
R-alkyl group (CuH2n + 1) This extracted Zn is back-extracted with dilute hydrochloric acid with a pH of 2 or higher to obtain high-purity ZnC.
Collect 12.

The reaction formula is R2・Zn+2HC1→ZnCl2+2R
-H (ZnC12 is heavy, and ZnCl is separated by specific gravity difference.
2) is recovered by neutralization and precipitation as zinc hydroxide (Zn(OH)2).

This zinc hydroxide can also be recovered as ZnO by firing.

0 method: As shown in column 0 of the process chart in Figure 1, after dissolving crude ZnO in mineral acid, that is, adding sulfuric acid to extract and precipitate Pb in the impurity as lead sulfate (PbS04), then By adjusting the pH to 4 to 6, Fe (OH) a precipitates, and at the same time other impurity elements such as As, Sb, and Cd also co-precipitate.

This coprecipitation method requires about 5 to 10 times as much Fe as the impurity, so when the Fe content is low in the solution, ferric salts (FeSO2, FeC12, etc.) are naturally added to adjust the pH to 4 to 6. A purification operation is achieved by adjusting the

In addition, in order to precipitate lead, the solution solution is added to the pond of the above method.
By adjusting H to 2 or less and passing hydrogen sulfide, lead sulfide (PBS) can be precipitated. In this case, copper becomes copper sulfide (Cu2S) and precipitates at the same time.

The solution purified as described above is pure zinc chloride (Zn CI) without any impurities.

) or zinc sulfate (ZnSO4), which is concentrated to form crystals (Znso4-7H20 or ZnCl2-2H
20) or neutralize the solution (pH 7 to 7).
Zn(OH)2) is precipitated and recovered as zinc hydroxide (Zn(OH)2).

Moreover, this zinc hydroxide can be calcined and recovered as ZnO.

Table 3 shows a comparison of the purities of purified (high purity) ZnO recovered by the above methods (4), (B) and (Q).

As explained above, the method of recovering Zn components from the Zn component of the present invention efficiently and inexpensively recovers Zn components with high purity and at the same time treats the waste in a sidecar manner. This fully achieves the intended purpose.

[Brief explanation of drawings]

Claims (1)

[Claims] An ammonium thiocyanate aqueous solution is added to the Zn1 substance to extract the Zn component as a rhodan compound, the extract is concentrated, and solid-liquid separation is performed to form rhodan Zn crystals by cooling crystallization. Zn characterized in that high-purity Rodan Zn is obtained by repeatedly subjecting the separated Rodan Zn to a purification operation in which the separated Rodan Zn is redissolved by adding a fresh ammonium thiocyanate aqueous solution and the Rodan Zn is recrystallized by cooling crystallization.
A method for recovering Zn content. An ammonium thiocyanate aqueous solution is added to the Zn-containing material to extract the Zn component as a rhodan compound, the extract is heated and roasted and collected as crude ZnO, and the collected crude ZnO is treated with mineral acid. The Zn component is characterized by dissolving the Zn component in a liquid, adding an organic solvent to preferentially extract only the Zn component, and back-extracting the Zn component with an inorganic solvent to obtain a highly pure Zn compound. How to recover. 3 Add ammonium thiocyanate aqueous solution to the Zn-containing material to extract the Zn component as a rhodan compound, heat and roast the extract and collect it as crude ZnO, and add the collected crude ZnO to mineral acid. Pb in the impurities dissolved in the solution is precipitated and separated by the addition of sulfuric acid, and other As, S
After purifying the solution by co-precipitating and separating impurity elements such as b and Cd with Fe(OH)3 by adjusting the pH of the solution to 4 to 6, the solution is neutralized or heated and roasted. A method for recovering Zni-containing and dextral Zn components, which is characterized by obtaining a highly purified Zn compound.