JPH1059722A - Production of high purity diarsenic trioxide from arsenic-containing waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a high purity diarsenic trioxide capable of utilizing as a raw material of mining and manufacturing industry from an arsenic- containing waste by burning the arsenic-containing waste in an oxygen atmosphere at a specific temp. and separating the sublimated diarsenic trioxide from oxides except arsenic, and then solidifying and recovering. SOLUTION: The waste containing arsenic is heated in the oxygen atmosphere in a reaction tube 1 previously controlled to the oxygen atmosphere and burnt at >=400 deg.C to <600 deg.C. The arsenic matter is separated from the oxides except that of arsenic by being sublimated as diarsenic trioxide by this way and the sublimated diarsenic trioxide is cooled by a water cooling condenser 3 to be solidified and is recovered in a collecting part 4. The high purity diarsenic trioxide of >=99.99% containing no metal arsenic is obtained by limiting the temp. range in burning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to arsenic-containing waste, for example, arsenic-containing waste produced during the production of metal arsenic, and arsenic produced when gallium is recovered from gallium arsenide by vacuum pyrolysis. Arsenic-containing waste, which recovers arsenic as high-purity diarsenic trioxide by burning and oxidizing arsenic-based waste such as arsenic-based residual hot water such as arsenic-based residual hot water during gallium arsenide synthesis The present invention relates to a method for producing high-purity diarsenic trioxide from materials.

[0002]

2. Description of the Related Art As a method for treating gallium arsenide scrap, which is waste containing arsenic, gallium arsenide scrap is thermally decomposed in vacuum at 1100 ° C. to 1150 ° C.
A method for purifying the obtained gallium by sublimating and removing arsenic (see Japanese Patent Application Laid-Open No. 57-101625). Gallium arsenide scrap is oxidized and roasted at 600 ° C. to 1100 ° C., and arsenic is sublimated and removed as oxide. Dissolving the obtained gallium oxide in an alkali or acid and subjecting it to electrowinning (see JP-A-64-4433), dissolving gallium arsenide scrap with an acid or alkali in the presence of an oxidizing agent, and adjusting the pH. Gallium as a hydroxide to precipitate out of solution and electrolyze it to obtain metallic gallium (JP-B-56
-38661).

[0003] However, gallium arsenide scrap has been reduced to 110.
Vacuum pyrolysis at 0 ° C to 1150 ° C, sublimation and removal of arsenic, and purification of the resulting gallium are intended to recover valuable gallium, and harmful arsenic is discarded from the beginning. Arsenic is a waste of no value.

[0004] Further, gallium arsenide scrap is reduced to 600 °.
Oxidation and roasting at C to 1100 ° C, sublimation removal of arsenic as an oxide, and dissolution of the obtained gallium oxide in an alkali or an acid for electrowinning are intended for gallium arsenide having an arsenic content of about 50%. In the case of waste containing arsenic as a main component, not only diarsenic trioxide but also arsenic having a high vapor pressure of 78 kPa at 600 ° C. is sublimated at the same time. As a result, unreacted arsenic is mixed as metal arsenic in the recovered product, and high-purity diarsenic trioxide cannot be obtained.

[0005] Gallium arsenide scrap is dissolved with an acid or alkali in the presence of an oxidizing agent, pH is adjusted and gallium is precipitated and separated from a solution as a hydroxide. The arsenic to be separated becomes low-grade sludge because it is adjusted to precipitate ions in the solution.

[0006] As seen in the above example of gallium arsenide scrap, the conventional separation of arsenic from arsenic-containing waste is carried out in order to recover valuable materials of interest, and harmful arsenic is disposed of. Because it was assumed that
The resulting arsenic is now a hazardous waste, and is currently being landfilled after temporary storage and stabilization.

However, in recent years, it has become difficult to landfill arsenic waste from the standpoint of global environmental protection.
The measures are eagerly awaited. Arsenic, which is a harmful substance, can be separated and recovered in a form that can be used effectively, and arsenic waste can be greatly reduced. As a form of arsenic recovery that can be effectively used, high-purity diarsenic trioxide can be mentioned.

[0008] Conventional methods for producing diarsenic trioxide include:
There is a method in which arsenic oxides and sulfides are roasted, and the obtained crude arsenic oxide is further purified in a reverberatory furnace.

[0009]

However, in the method in which arsenic oxides and sulfides are roasted and the obtained crude arsenic oxide is further refined in a reverberatory furnace, the obtained diarsenic trioxide has a purity of 9%.
Since it is about 9.5%, it cannot be used as a raw material for high-purity metal arsenic, and is insufficient as diarsenic trioxide as another raw material for industrial use.

The present invention solves such a problem in the treatment of arsenic-containing waste, and more than 99.99% of arsenic-containing waste can be used as a raw material of high-purity metal arsenic or a raw material for mining and industry. It is an object of the present invention to provide a method of producing high-purity diarsenic trioxide from arsenic-containing waste, which can easily obtain high-purity diarsenic trioxide and reduce arsenic waste.

[0011]

SUMMARY OF THE INVENTION According to the method of the present invention for producing high-purity diarsenic trioxide from arsenic-containing waste, the arsenic-containing waste is preliminarily converted into an oxygen atmosphere and then heated in this oxygen atmosphere. By burning in a temperature range of not less than 600 ° C. or more and subliming arsenic as diarsenic trioxide and separating it from oxides other than arsenic,
The sublimated diarsenic trioxide is coagulated and collected.

The temperature range in which combustion takes place is 400 ° C. or more and 60 ° C.
When the temperature is lower than 0 ° C., 99.9 containing no metal arsenic is contained.
High-purity diarsenic trioxide of 9% or more can be obtained.
Since the recovered diarsenic trioxide has a high purity of 99.99% or more, it can be used as it is as a raw material for producing metal arsenic, and can also be used as another raw material for mining and industry.

[0013]

FIG. 1 is a longitudinal sectional view of a combustion oxidizer used in an embodiment of the method for producing high-purity diarsenic trioxide from arsenic-containing waste according to the present invention.

Here, a heating section 2 having a heating coil 5 is provided around the horizontally arranged reaction tube 1, and a water jacket 6 is provided below a predetermined position of the reaction tube 1. The water-cooled condenser 3 provided with the collector and the collection unit 4 are connected to each other.

An arsenic-containing waste is charged into the reaction tube 1 and the inside thereof is made to be in an oxygen atmosphere, and then heated by energizing the coil 5 to burn in a temperature range of 400 ° C. or more and less than 600 ° C. Then, the arsenic component is sublimated as diarsenic trioxide and separated from oxides other than arsenic. The sublimated diarsenic trioxide is solidified by being cooled by the water-cooled condenser 3 and collected by the collection unit 4.

Arsenic exhibits a vapor pressure of 0.8 kPa to 78 kPa in the temperature range of 400 ° C. to 600 ° C., but arsenic wastes combusted at a temperature of 350 ° C. to 400 ° C. Starting, diarsenic trioxide is produced. Further, once the combustion is started, a self-combustion reaction occurs to continue the combustion. At this time, if the supply of oxygen is insufficient, combustion becomes incomplete, and arsenic that is partially unreacted sublimates and enters the recovered diarsenic trioxide as metal arsenic.

Although diarsenic trioxide is produced at combustion temperatures below 400 ° C., at low combustion temperatures below 400 ° C.,
The reaction tube 1 contains approximately 258 ° C. at which glassy arsenous acid is generated.
Since there are many parts in the temperature range of about 300 ° C. or less, the solidified substance is fixed in the reaction tube 1 and the recovery becomes difficult, and the recovery rate decreases.

At a combustion temperature of 600 ° C. or higher, the sublimation point of arsenic is around 615 ° C., so that arsenic vapor is generated intensely and oxidation is insufficient, and metal arsenic, which is an impurity, is mixed in the recovered diarsenic trioxide. . At this time, if oxygen is supplied so that all of the arsenic becomes diarsenic trioxide at a combustion temperature of 600 ° C. or more, a reaction occurs explosively, and there is a risk of damage to the device.

Therefore, 400 ° C. or more and less than 600 ° C.
Preferably, high-purity diarsenic trioxide can be obtained by burning in an oxygen atmosphere in a temperature range of 450 ° C. or more and 550 ° C. or less.

[0020]

【Example】

[Example 1] Waste 5 as residual hot water from the synthesis of gallium arsenide
000 g was charged into the reaction tube 1 of the combustion oxidizer shown in FIG. 1, and kept at 550 ° C. in an oxygen atmosphere and burned for 5 hours. This waste is mainly composed of arsenic, 500 ppm of iron,
800 ppm silicon, 100 ppm zinc, 800 gallium
It contained impurities of not less than ppm. The analytical values of the waste are shown in Table 1.

[0021]

[Table 1]

The sublimated diarsenic trioxide is supplied to the water-cooled condenser 3
And solidified in the collecting section 4 to collect 6,300 g
g remained in the reaction tube 1. The recovery is 96%. The diarsenic trioxide obtained in the collecting part 4 was a white powder crystal, and the impurities were extremely high purity of about 0.5 ppm for silicon and about 3 ppm for gallium. The analytical values of the products are shown in Table 2.

[0023]

[Table 2]

Example 2 1000 g of arsenic-based waste collected when gallium arsenide scrap was separated into arsenic and gallium by a vacuum pyrolysis method was placed in a reaction tube 1 of a combustion oxidation apparatus shown in FIG. Charge, 450 in oxygen atmosphere
C. and kept burning for 5 hours. This waste is mainly composed of arsenic, 200 to 300 ppm of indium, and 2 parts of boron.
00 to 300 ppm, zinc 100 ppm, gallium 50
It contained impurities of 0 ppm or more. Table 3 shows the analytical values of the waste.

[0025]

[Table 3]

The sublimated diarsenic trioxide is supplied to the water-cooled condenser 3
Solidified in the collecting section 4 and collected in an incineration residue 9
0 g remained in the reaction tube 1. The recovery is 91%. The diarsenic trioxide obtained in the trapping section 4 was a white powder crystal, and the impurities were of a very high purity of about 0.1 ppm for silicon and about 5 ppm for boron. Table 4 shows the analysis values of the products.

[0027]

[Table 4]

Comparative Example 1 Combustion oxidation was carried out in the same manner as in Example 1 using the same raw materials as in Example 1. However, the combustion temperature was 600 ° C.

As a result, the arsenic oxide obtained in the collecting section 4 was not white, but gray. This is 600 °
In C, the vapor pressure of arsenic was as high as 78 kPa, and the amount of arsenic vapor generated was large. Therefore, unreacted arsenic vapors were simultaneously mixed and mixed as metal arsenic in diarsenic trioxide during coagulation. Diarsenic trioxide mixed with metal arsenic cannot be used as a raw material for high-purity metal arsenic at all, and is insufficient as a raw material for mining and industrial use.

[0030]

According to the present invention, high purity diarsenic trioxide of 99.99% or more can be easily obtained from arsenic-containing waste, and the obtained diarsenic trioxide is converted to high-purity metal. It can be used as a raw material for arsenic and other industrial materials.

As described above, the arsenic separated from the waste can be effectively used, so that arsenic waste which has been regarded as hazardous waste can be reduced, thereby contributing to environmental protection.

[Brief description of the drawings]

FIG. 1 is a longitudinal section of a combustion oxidizer used in a method for producing high-purity diarsenic trioxide from arsenic-containing waste.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Heating part 3 Water-cooled condenser 4 Collection part 5 Coil 6 Water jacket

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuhei Konagaya 20th Kamiyoshima Odate, Yoshima-cho, Iwaki-shi, Fukushima Furukawa Machinery & Metal Co., Ltd.

Claims (1)

[Claims] 1. An arsenic-containing waste is preliminarily converted into an oxygen atmosphere and then heated in the oxygen atmosphere.
The arsenic component is sublimated as diarsenic trioxide by being burned in a temperature range of not less than 600 ° C. to arsenic to separate from oxides other than arsenic, and then the sublimated arsenic trioxide is coagulated and recovered. A method for producing high-purity diarsenic trioxide from contained waste.