JPS59164639A - Separation of arsenic - Google Patents

Abstract

PURPOSE:To remove As effectively and simply in the form of iron arsenate from an acidic solution contg. As and heavy metals such as Cu by adding an oxidizing agent and ferrous salt to the solution and oxidizing the ferrous salt while controlling the pH using air or the like. CONSTITUTION:An oxidizing agent such as H2O2 is added to an acidic solution contg. As and heavy metals such as Cu, Cd, Zn, etc. produced after separating Pb from the flue cinder generated in a refining stage of Cu using H2SO4 to transform As<3+> to As<5+> which is more easily precipitated. A ferrous salt contg. <=ca. 10pts.wt. Fe per 1pt.wt. As is then added to the solution and Fe<2+> is transformed to Fe<3+> by oxidizing with air, O2, an oxidizing agent, or a combination thereof while adjusting the pH of the solution to 1.5-3.0, pref. 2.0-2.6 to precipitate As in the form of iron arsenate. By this process, As is effectively separated from an acidic solution contg. heavy metals such as Cu in the form of iron arsenate contg. >=ca. 10% As.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and removing arsenic from an acidic solution containing arsenic.

The smoke generated during the copper smelting process contains copper, the main ingredient of the raw material, as well as arsenic and cadmium.

Contains volatile components such as zinc and lead. Leaching with sulfuric acid is generally performed to recover copper's valuable materials from this smoke ash and separate impurities such as arsenic. By leaching smoke ash with sulfuric acid, lead becomes lead sulfate and is insoluble in sulfuric acid solution, so it is separated as a residue and separated from the lead raw material. On the other hand, copper, arsenic, cadmium, zinc, etc. are leached out by sulfuric acid and enter the solution. The present invention relates to a method for efficiently separating and removing arsenic from this solution.

Nine conventional methods for recovering arsenic from solutions containing arsenic, cadmium, zinc, etc. include hydrogen sulfide.

Steel, which is a valuable material, is first separated and recovered as sulfurized steel or precipitated copper using neutralizing agents such as iron powder and calcium carbonate. Next, a neutralizing agent is further added to the copper-rich liquid to adjust the pH to 4 or more, and if there is little button iron in the liquid, an iron salt is added.

Perform air oxidation while maintaining the pTI of the liquid at 4 or more,
A method of separating and removing arsenic as iron arsenate is often used. However, in these known methods, a copper removal step is required before arsenic separation, which is disadvantageous in that the number of steps is increased. The product is large, and the arsenic grade of the iron arsenate is low, at less than 10 parts, and the subsequent disposal of the large amount of iron arsenate generated is also troublesome. Furthermore, if the liquid contains cadmium.

A pH of 4 or higher has the disadvantage of causing precipitation of cadmium in iron arsenate. In this way, when separating arsenic from a solution containing arsenic and other heavy metals, if [p) T is 4 or more and precipitation is caused, arsenic can be completely separated from the solution, but copper may be present in the solution. If present, it is necessary to separate it in advance, and if cadmium is present in the liquid, there is a drawback that cadmium will precipitate together with arsenic. Furthermore, since the pH at the time of precipitation and separation of arsenic is as high as 4 or more, there is also the drawback that the amount of arsenic precipitates is large. For this reason, engineers in this field
We are researching various techniques for precipitation and separation of arsenic from solutions containing heavy metals such as copper in the acidic region where the ratio is lower than 4. According to Japanese Patent Publication No. 56-6356, one method is to
．． Discloses a treatment method in which ferrous sulfate is added to an acidic sulfuric acid solution containing arsenic and heavy metals, and then heated in a high-pressure container under oxygen pressure or air pressure, in order to precipitate and separate arsenic at 0 to 52. ing. According to this method, arsenic is precipitated and separated at a pH in the range of 2.0 to 3.2, so it is said that arsenic and other heavy metals can be separated well. However, as seen in the example, 1.51 p/ari with industrial oxygen
To process at a high temperature of 130°C in a pressurized container.

The disadvantage is that the equipment is expensive. There is also the operational disadvantage of handling acidic solutions in high-pressure vessels. Furthermore, after arsenic is precipitated, there is still 0.1 arsenic in the solution.
4 to 0.39 f/remaining.

The drawback that the precipitation separation of arsenic is not complete is also shown. In this way, it is said that it is extremely difficult to efficiently precipitate and separate arsenic from other heavy metals in an acidic region with pT (3 or less), but the inventors have solved this drawback and simplified the process. Along with.

We conducted various studies on how to efficiently separate arsenic from acidic solutions containing other heavy metals using iron arsenate with an arsenic content of 10% or more, and succeeded in developing the first process. The method will be explained below.

In acidic solutions containing arsenic and heavy metals such as copper, cadmium, and zinc, arsenic is dissolved in trivalent or pentavalent form. 3
Since valent arsenic is difficult to precipitate and separate, an oxidizing agent is first added to the solution to oxidize trivalent arsenic to pentavalent arsenic. The oxidizing agent used at this time may be potassium permanganate, hydrogen peroxide, chlorine, etc., and it is sufficient that the amount added is twice the chemically required amount of trivalent arsenic. After the oxidation of arsenic is completed, the p of the liquid
Adjust H to 1.5 to 50, add ferrous salt to this,
The pH of the liquid is 1.5 to XO, preferably 2.0 to 2.6.
Ferrous iron is oxidized to ferric iron by oxidizing with air or industrial oxygen or an oxidizing agent such as those exemplified above while maintaining the temperature.

Arsenic is precipitated and separated as iron arsenate. By this method,
Not only is arsenic efficiently separated from other heavy metals such as copper, but the reaction is carried out in an acidic region with p)I of 2.0-2.6, so iron arsenate with an arsenic content of 101 or more can be obtained. It will be done. The temperature of the solution during the above reaction treatment may be at room temperature or below the boiling point at atmospheric pressure.

Examples of the present invention are shown below.

EXAMPLE To 1 liter of a sulfuric acid acidic solution having a pH of 1.7 containing the ingredients listed in Table 1 below, 3.61% potassium permanganate is added and mixed and stirred. Since this oxidation is completed in a short time, the stirring time may be several minutes.

Table 1 Arsenic-containing solution Next, a small amount (x4r) of calcium carbonate was added to the solution to adjust the I)H of the solution to 2.0 to 2.6, and then 25F of ferrous sulfate was added. (Calcium carbonate and ferrous sulfate may be added first), pH of the solution
Air oxidation is carried out while maintaining g1 at 2.0 to 2.6.
Oxidize iron to ferric iron, precipitate and separate arsenic as iron arsenate,
Perform filtration and separation. The components of the filtered iron arsenate and the filtrate are shown in Table 2.

Table 2: When an oxidizing agent is added to the solution of iron arsenate and filtrate in Table 1, arsenic can be oxidized by air oxidation of ferrous salt without oxidizing it to trivalent arsenic (F5) as in the conventional method. When the pH is removed, the pH becomes 1.5.
-50, the precipitation of arsenic is insufficient, and the arsenic content in the filtrate after iron arsenate removal is 1. For example, when the pH is 2.5, 71/1 remains, and the arsenic content is 1. The purpose of removal is not achieved.

On the other hand, in order to completely remove arsenic, the pll of the liquid is increased to 1, for example 4.1, and air oxidation is performed as in the conventional method.The arsenic in the liquid is [L 1 f/1. Although the purpose of arsenic removal was achieved as follows, the copper content in iron arsenate was as high as 5.2%, and the cadmium content was as high as 0.2%, making it difficult to separate copper, cadmium, and arsenic. It's coming.

From the above results, it is clear that the method of the present invention efficiently removes arsenic, copper, and
It can be separated from heavy metals such as cadmium. Further, in this method, the amount of iron used for precipitation is extremely small, less than 10 parts (approximately 2.2 parts in the example) per 1 part of arsenic.

It has the advantage of reducing iron arsenate precipitation, and is extremely simple in terms of equipment, requiring only a container equipped with a simple stirrer.

Bamboo permit applicant Nippon Kohata Co., Ltd. Agent: Patent attorney (7569) Keishi Namiyo 7- 0 shots: Hiroshi Hosaka 3-17-35 Shinzenminami, Toda City Hon Mining Co., Ltd. Central Research Institute 8-

Claims (1)

[Claims] An oxidizing agent is added to an acidic solution containing arsenic and heavy metals such as copper, cadmium, and zinc to oxidize the trivalent arsenic in the solution to pentavalent arsenic, then a ferrous salt is added, and the solution is further oxidized. p of
By oxidizing ferrous iron with a combination of air, oxygen, or an oxidizing agent or more while maintaining I(I) at 1.5 to 50, arsenic can be converted into iron arsenate with a high arsenic grade. , a method for separating arsenic, characterized in that it is separated by precipitation from a solution containing the heavy metal.