JPH0421519A - Production of highly purified arsenic chloride from arsenic sulfide-containing substance - Google Patents

Abstract

PURPOSE:To readily obtain highly purified arsenic chloride in high yield and at a low cost by introducing chlorine gas into a slurry of arsenic sulfide- containing substance by keeping concentration of sulfuric acid at a specific value to convert contained arsenic component to arsenic chloride and recovering by distillation. CONSTITUTION:Chlorine gas is introduced into a slurry of arsenic sulfide- containing substance by keeping concentration of sulfuric acid in the slurry to 40-80wt.%, preferably 50-70wt.%. Then, arsenic component in the arsenic sulfide-containing substance is converted to liquid drop of arsenic chloride and suspended in a solution. Simultaneously, sulfur component is separated out and impurity component such as copper or iron is dissolved in the solution. Next, a mixed solution of resultant reaction product is distilled to distil away, arsenic chloride, then isolated from residual elemental sulfur and acid solution. Thereby, highly purified arsenic chloride of >=4N can be produced from arsenic sulfide-containing substance in a simple process with a small energy consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for producing high-purity arsenic chloride from arsenic sulfide-containing materials.

(b) Prior art The methods conventionally used to effectively purify and recover arsenic components contained in arsenic sulfide-containing materials are as follows:
Most of the arsenic acid is first recovered as arsenic acid, and these methods are broadly divided into dry methods and wet methods.

In the dry method, arsenic sulfide-containing material is oxidized and desulfurized roasted in an airflow roasting furnace to obtain crude arsenite with a grade of 90 to 93%, and this crude arsenite is further sublimated and purified in a reverberatory furnace to a grade of 99.5% or higher. This is a method of converting crude arsenic acid into crude arsenic acid.

However, although this method has a relatively wide range of raw materials,
It is necessary to perform a two-step process called purification.

(2) The oxidative desulfurization efficiency by airflow roasting is about 75 to 85%, and a considerable amount of repeated processing is required.

■) It is necessary to remove sulfur dioxide gas generated by the decomposition and oxidation of materials containing arsenic sulfide.

■) Normally, the equipment can be operated unattended, but in the event of a breakdown or periodic repair, sufficient protection against harmful powders is required.

■) The thermal energy required for drying raw materials, airflow roasting, sublimation refining, etc. is large.

There are many problems that need to be solved.

On the other hand, as a wet method, a method for producing arsenous acid has been proposed and implemented in Japanese Patent Publication No. 60-46048, but this method involves reacting a substance containing arsenic sulfide with a copper sulfate solution to convert it into an arsenous acid solution and copper sulfide. Then, the reaction solution is cooled to crystallize arsenous acid, which is filtered together with sulfide steel to separate it from the mother liquor containing impurities, and the S slag is repulped. In this method, copper sulfide is separated from copper sulfide by 5-filtration, arsenous acid is crystallized by refining and reducing the arsenic acid solution, and the product is obtained by filtration, separation, and drying.

However, even in this method, (a) in the first stage crystallization and 5th filtration separation step,
Approximately 10 to 15 g/i of arsenic remains in the mother liquor, and this is repeated in the arsenic sulfide precipitation step, resulting in an unavoidable drop in efficiency.

(b) The process is extremely complex, spanning more than ten steps.

(C) Since most reactions are carried out at high temperatures (80 to 90°C), a large amount of thermal energy is consumed.

There are many other issues that need to be resolved.

In addition, in order to obtain an arsenic compound of even higher purity, it is necessary to re-purify the arsenous acid obtained above using a recrystallization method, alkali purification method 9 fractional sublimation purification method, arsenic chloride conversion distillation method, etc. .

Furthermore, as a method for recovering metallic arsenic from materials containing arsenic sulfide, Japanese Patent Publication No. 57-52941 has been proposed, but as a wet method, the number of steps is relatively small, but the final product, metallic arsenic, is There are problems such as low quality of about 70% and low recovery rate.

In addition, when producing high-purity arsenic oxide or metal arsenic using arsenous acid as a starting material, the general purification method is to go through arsenic chloride, which involves dissolving arsenous acid in concentrated hydrochloric acid and then adding it to the solution. This method involves adding concentrated sulfuric acid and dehydrating it to produce arsenic chloride. A lot of research has been done on this method, for example, “Carpenter Trial Report Vol. 6
, No. 24 (Showa 30), written by Ei Toriyoshi, "Carpentry Examination Report No. 323" (Showa 39), written by Nakane et al., published in Japanese Patent Application Laid-open No. 100413/1983, etc., but there are still problems to be solved. The current situation is that there are many.

(C) Disclosure of the Invention The present invention has been made by conducting various experiments and studies in order to produce high-purity arsenic chloride in a simple process with low energy consumption and high yield using an arsenic sulfide-containing material as a starting material. As a result, by changing the sulfuric acid concentration in a slurry consisting of arsenic sulfide-containing material and water and blowing chlorine gas into it, it was possible to directly convert most of the arsenic sulfide into droplets of arsenic chloride within a predetermined sulfuric acid concentration range. It was developed based on the knowledge that it could be done.

That is, the present invention introduces chlorine gas into the slurry of the arsenic sulfide-containing material while maintaining the sulfuric acid concentration in the slurry at 40 to 80%, preferably 50 to 70%, and converts the arsenic component in the arsenic sulfide-containing material into arsenic chloride. The sulfur component is suspended as droplets in an acidic solution and the sulfur component is precipitated as elemental sulfur, and copper,
A first step of eluting impurity components such as iron into the solution;
a second step of distilling the reaction product mixture obtained in the first step to separate arsenic chloride from elemental sulfur and an acidic solution; The present invention relates to a manufacturing method.

The first feature of the present invention is that chlorine gas is used to convert the arsenic component in the arsenic sulfide-containing material into arsenic chloride.

As2521 +6C1,,=2AsC statement, +3S[Δ
H= -36,5KCall ol] ・ ・ 11
Life ・ ・ ・ (1) That is, according to the above formula (1), the liquid temperature will automatically rise by introducing chlorine gas,
As a result, the arsenic component in the arsenic sulfide-containing material is easily converted to arsenic chloride without the need for any heating.

The reaction according to the above formula (1) proceeds extremely stoichiometrically,
Almost no chlorine gas escapes from the system until the reaction is almost completed.

Further, it is important to monitor and control the progress of the reaction using redox potential.

The reaction of formula (1) is started by introducing chlorine gas into the arsenic sulfide-containing slurry and raising the temperature accordingly, and then by adjusting the reaction temperature by introducing chlorine gas and cooling with cooling water, The reaction can proceed and be completed without the addition of thermal energy, and by adjusting the reaction temperature to maintain a temperature below the transformation point of sulfur, the elemental sulfur produced can be converted into a crystalline 5-filterable material. It is also possible to obtain a very good one. At this time, most of the sulfides such as copper, iron, and zinc contained as impurities in the arsenic sulfide-containing material are leached out and eluted into the acidic solution.

The second feature of the present invention is to take advantage of the property that the solubility of arsenic chloride decreases in an acidic solution of sulfuric acid, so that a slurry consisting of a substance containing arsenic sulfide and water is added so that the concentration of sulfuric acid in the solution is 40 to 80%. It consists in adding sulfuric acid to.

As a result, the generated arsenic chloride is separated from the acidic solution and becomes suspended in droplets.

The reason for setting the above sulfuric acid concentration to 40 to 80% is that when the sulfuric acid concentration is below 40%, the generation of arsenic chloride droplets is insufficient, whereas when it is above 80%, the effect of generating arsenic chloride droplets is saturated. This is because you end up doing it.

Furthermore, the third feature of the present invention is that only arsenic chloride is separated by distillation from the acidic solution containing arsenic chloride droplets, crystalline element sulfur, and copper, zinc, iron, etc. generated as described above. be.

By utilizing the advanced separation properties of arsenic chloride through distillation, it is possible to almost completely separate not only the crystalline element sulfur but also copper, iron, zinc, etc.

As the above-mentioned distillation method, any of the commonly used methods such as heating distillation, aerated distillation, and vacuum distillation can be used.

However, if we pay attention to the fact that elemental sulfur with good filterability is mixed, in order to maintain favorable S filtration properties until the time of sulfur separation in the subsequent process, the Moto distillation temperature is set at 95°C, which is the transformation point of sulfur. It is necessary to do the following. In this case, aeration distillation or vacuum distillation is preferred.

As described above, according to the present invention, using an arsenic sulfide-containing material as a starting material, the sulfuric acid concentration in the slurry of the arsenic sulfide-containing material is adjusted to 40 to 80%, preferably 50 to 70%, and chlorine gas is added to the slurry. By introducing it into the inside (first step),
The arsenic contained in the arsenic sulfide-containing material is converted into droplets of arsenic chloride, and almost all of the impurities such as copper, iron, and zinc are eluted into an acidic solution as chlorine compounds. By distilling this reaction product mixture (second step), highly pure arsenic chloride can be captured as a distillate in high yield. It can be collected and collected.

Figure 1 shows a manufacturing process diagram of high-purity arsenic chloride according to the present invention (
Example), but the process of the present invention is comprised of only three steps: (1) chlorination reaction, (2) distillation, and (3) 5-filtration separation, and produces a high-purity arsenic chloride product. can be obtained in high yield.

Next, one embodiment of the present invention will be explained with reference to examples.

(D) Example The component composition of the arsenic sulfide-containing material tested in carrying out the method of the present invention is as shown in Table 1.
．． It is 3%.

Table 1 Example 1 600g wet amount of arsenic sulfide-containing material having the composition shown in Table 1
900ml of sulfuric acid solution with a specified concentration! Make a slurry with L and add 1 chlorine gas while stirring in a 2-liter sixth flask.
．． It was introduced at 0 sentences/minute.

By introducing chlorine gas, the slurry temperature increases to 60~60℃.
The progress of the reaction at 70° C. was monitored by a redox potentiometer and the end point was determined.

Subsequently, the slurry after the chlorination reaction was heated to 60 to 70°C without separating the reaction products by S filtration.
Distillation was performed to distill out arsenic chloride. Since the boiling point of arsenic chloride is about 130°C at normal pressure (760 - Hg), the operating pressure must be adjusted to 100 - 100°C in order to distill it at 60 - 70°C.
It was necessary to reduce the pressure to 20 mmHg.

Table 2 shows the results when the sulfuric acid concentration in the slurry was varied.

(Left below) As is clear from Table 2, the sulfuric acid concentration of the slurry is -F
By increasing the amount of arsenic remaining in the acidic solution as pot residue, we were able to dramatically increase the amount of arsenic chloride distilled.

In addition, the grade of elemental sulfur in the residue was 95% in both cases.
% or more.

Example 2 Using a reaction vessel with a capacity of 50, a wet amount of 15K of arsenic sulfide-containing material having the component composition shown in Table 1 in the same manner as in Example 1 was prepared.
In the same manner as in Example 1, chlorine gas was introduced at 25 cycles/min into a slurry in which the sulfuric acid concentration was maintained at 60% using a sulfuric acid solution with a predetermined concentration of 22.5 min to carry out a chlorination reaction, and then distilled. As a result, 3.45 J1 of arsenic chloride was obtained.

Further, 2.9 kg of crystalline elemental sulfur with a sulfur grade of 95.3% and arsenic of 0.6% was obtained.

Table 3 shows the results of analyzing the obtained arsenic chloride by emission spectrometry.

(The following is a blank space) As is clear from Table 3, the arsenic chloride obtained by the method of the present invention has a high purity of 4 N (99.99%) or higher.

As mentioned above, the quality of arsenic chloride obtained by the method of the present invention through extremely simple process treatment is extremely high purity as shown in the above example, and this arsenic chloride is used as a raw material through hydrolysis or reduction. It goes without saying that arsenous acid and metallic arsenic produced by known processing methods are also highly pure products.

Furthermore, the elemental sulfur separated by filtration from the distillation residue according to the present invention has a grade of 95% or more, and can be effectively used as a raw material for producing sulfuric acid, for example.

(e) Effects of the invention As described above, according to the method of the present invention, arsenic chloride of 4N or higher purity can be produced using arsenic sulfide-containing material as a starting material in a simple process with low energy consumption, and with high yield and low It can be manufactured at low cost.

Furthermore, it has the advantage that high-purity arsenous acid and metallic arsenic can be easily produced by known methods based on the high-purity arsenic chloride produced by the method of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing the steps of the method for producing high-purity arsenic chloride from an arsenic sulfide-containing material according to the present invention.

Claims (1)

[Claims] While maintaining the sulfuric acid concentration in the slurry of the arsenic sulfide-containing material at 40 to 80%, preferably 50 to 70%, chlorine gas is introduced into the slurry to convert the arsenic component in the arsenic sulfide-containing material into arsenic chloride droplets in the solution. A first step of suspending the sulfur component in the solution, precipitating the sulfur component as elemental sulfur, and eluting impurities such as copper and iron into the solution; and distilling the reaction product mixture obtained in the first step. A method for producing high-purity arsenic chloride from a substance containing arsenic sulfide, comprising a second step of separating arsenic chloride from elemental sulfur and an acidic solution.