JPS6042171B2 - Selective separation method for arsenic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for selectively separating arsenic from substances containing arsenic and other metal components. The present invention relates to a method for selectively separating arsenic by a leaching method using.

Arsenic is contained in various smoke ash and residues from non-ferrous metal smelting along with other metal components.

For example, arsenic in the charge is concentrated in Cottrell smoke generated during the operation of a recycling furnace that processes scrap, etc., and the arsenic content may exceed 10% at high concentrations. In addition to arsenic, it contains copper, iron, zinc, nickel, cadmium, etc. Recently, attempts have been made to separate arsenic from these arsenic-containing substances for the purpose of preventing pollution and recovering arsenous acid as a by-product. Conventional arsenic recovery methods include converting arsenic into arsenic sulfide using a sulfurization method, separating it into individual households, and storing the dehydrated lumps, or oxidizing and leaching the arsenic sulfide and collecting the leachate. A method of performing concentration and high concentration after reduction has been proposed, but it is not satisfactory due to the need for large storage space, the need for complicated and long process operations, and poor selective separation of arsenic.

One of the simplest arsenic recovery methods is the leaching method using an aqueous sulfuric acid solution.

According to this leaching method, it is possible to obtain an arsenic leaching rate of 90% or more, but since zinc and copper that coexist are also leached out at a leaching rate of 90% or more, crystals such as zinc sulfate are formed when arsenic is concentrated. There were problems when recovering arsenic as arsenous acid. Another method for separating arsenic is the solvent extraction method. Solvent extraction uses an organic solvent containing an extractant capable of selectively extracting a particular substance to separate it from an aqueous solution containing the substance. When applying the solvent extraction method to an arsenic-containing substance such as the above-mentioned Cottrell smoke ash, an acid leaching solution of the arsenic-containing substance, for example, an aqueous sulfuric acid solution, is prepared first, and then this leaching solution is transferred to an extraction tank and an organic solvent containing an appropriate extractant is added thereto. Solvent is added. Selective extraction of arsenic is possible by finding a suitable extractant, and various trials are being carried out. One of the problems associated with this solvent extraction method is that when applied to solid arsenic-containing materials such as Cottrell smoke,
As mentioned above, the acid leaching solution must be prepared. In the nonferrous smelting industry, there are many processes for main products, by-products, and waste, and efforts are being made to eliminate even one of them. It would be advantageous if it could be applied directly to the substance, since it would save the preparation of an acid leachate. In the end, if a method can be established that allows arsenic to be leached by direct contact with arsenic-containing substances as in the leaching method described above, and selectively extracts only arsenic as in the solvent extraction method, the arsenic separation method It is extremely useful industrially.

From this point of view, as a result of numerous experiments, the present inventors decided to bring a solvent consisting of an alcohol having 4 to 5 carbon atoms and sulfuric acid into contact with a substance containing arsenic and other metal components. We have thus found that direct selective separation of arsenic is possible.

This method combines the advantages of conventional leaching methods and solvent extraction methods, and is a novel method that can also be called an acid-organic solvent leaching method. In this method, not only the usual considerations for leaching and solvent extraction methods, but also the compatibility between the acid and the organic solvent must be taken into account. It is also necessary that the arsenic transferred into the solvent be recovered according to a back extraction operation in a general solvent extraction method, and that the solvent after back extraction can be reused. As a result of such comprehensive studies, it has been found that the combination of the alcohol and sulfuric acid is optimal. Furthermore, it has been found that back extraction with water is possible. An organic diluent is generally used to improve phase separation during back extraction. Thus, the present invention selectively separates and leaches out arsenic by contacting a substance containing arsenic and other metal components with a solvent containing an alcohol having 4 to 5 carbon atoms and sulfuric acid, and then leaching out arsenic. Provided is a method for selectively separating arsenic, which is characterized by recovering an after-liquid.

Furthermore, the present invention also provides a method for selectively separating arsenic, which also includes back-extracting the post-leaching solution with water. The arsenic-containing substances to be treated in the present invention are smoke ash, residue, precipitates, etc. obtained in various steps of non-ferrous smelting, and one example is Cottrell smoke generated during recycling furnace operation.

Although this varies depending on the operating conditions, it is approximately within the following composition range. Carbon number 4 for the arsenic-containing material placed in the leaching tank
A mixed leachate of alcohols and sulfuric acid of 5 to 5 is added.

In this case, in order to improve layer separation during subsequent back extraction, it is preferable to add an organic diluent such as mineral oil or higher alcohol to the leachate. The concentration of sulfuric acid is approximately 11-2% by volume of the leachate when no diluent is added, but higher concentrations can be used when a diluent is added. If the sulfuric acid concentration is less than 1%, the leaching rate will decrease, while if it exceeds 2% by mass, the phase separation with water during back extraction will be poor. Any alcohol having 4 or 5 carbon atoms can be used. Those having less than 4 carbon atoms are easily soluble in water and have very poor phase separation properties. On the other hand, alcohols having more than 5 carbon atoms do not dissolve in water and have good phase separation properties, but they significantly reduce the leaching ability of the leachate. aliphatic saturated alcohol, aliphatic unsaturated alcohol,
A variety of alcohols can be used, including alicyclic alcohols, as well as monohydric and polyhydric alcohols; representative examples include n-
These include butyl alcohol, isobutyl alcohol, Sec-butyl alcohol, n-amyl alcohol, isoamyl alcohol, Sec-amyl alcohol, and the like. The diluent is usually used in an amount of about 113 to 1 mol based on the amount of alcohol. The arsenic-containing material and leachate placed in the leaching tank are left under agitation for a sufficient period of time to effect the desired leaching. Stirring may be performed by any appropriate means such as a magnetic stirrer, stirring blades, or gas bubbling. Although room temperature is sufficient for the leaching temperature, there is no problem in raising the temperature to about 80°C. The concentration of the slurry of the arsenic-containing substance and the leachate is appropriately determined depending on the equipment capacity, the type and composition of the leachate, the composition of the arsenic-containing substance, the particle size, etc., to the extent that appropriate stirring can be performed. However, if the slurry concentration is too high, If too much, the filterability after leaching will deteriorate, so the upper limit should be about 450y per 1' of leachate. After leaching, the leaching solution and residue are separated by filtration or centrifugation.

More than 80% of arsenic migrates into the solution after leaching, but almost no other component metals migrate. The post-leaching liquid is sent to a back-extraction step and the residue is disposed of appropriately after recovering the residual alcohol. Back extraction can be easily accomplished by adding water to the post-leaching liquor.

Water is added so that the AIO (water/liquid after leaching) ratio is about 1115 to 5, and phase separation occurs when the mixture is left to stand after stirring. The back-extraction operation may be repeated several times if necessary. The leachate phase after back extraction is recycled and the arsenic-enriched aqueous phase is sent to an arsenic recovery process. For example, zinc, which is contained in Cottrell smoke ash about 1 times as much as arsenic, is 114 times more than arsenic when back-extracted.
The amount of copper, iron, etc. decreases from 0 to 11,100, and the amount of copper, iron, etc. is also small. Therefore, a sufficient arsenic concentration can be obtained for the purpose of producing arsenous acid. Regarding increasing the arsenic concentration, approximately 30-50 yI' can be achieved in the leachate by increasing the starting slurry concentration, and by selecting the AIO ratio during back-extraction, an arsenic concentration of more than 50 yIe can be achieved in the aqueous phase without evaporative concentration. can be obtained. Although almost the same effect was obtained when tributyl phosphate was used instead of alcohol in the above leaching operation, the use of alcohol is preferable in terms of cost.

Example 1 Arsenic leaching according to the present invention was carried out using Cottrell smoke ash having the following composition generated during recycling furnace operation: Leachate 21
0ml was prepared at the following concentration: n-butyl alcohol
...140m1 kerosene
...60mt concentrated sulfuric acid (95%)
...10m1 of this leachate 21
The above Cottrell smoke ash is 20y140y for 0mt.
Changes in leaching rate were investigated by adding 160y.

The test was first carried out using Cottrell smoke ash 20y. After stirring for 1 minute with a magnetic stirrer, it was left to stand for 5 minutes, and 5 ml of supernatant liquid was collected for analysis.
0y was added and stirred in the same manner, and after collecting the supernatant, 20y of Cottrell Dust was further added and the same operation was performed. Table 1 shows the leaching rate of each component for each slurry concentration for the leached liquid after filtration. From Table 1, the leaching rate of arsenic is 87
It can be seen that the leaching rate of other components is very low.

Back extraction was performed by adding water to the above leached solution.

The test was conducted using 30ml of the leached solution with arsenic concentration of 25.76 da 1f.
This was carried out by adding 10 ml (AlO: 113), 20 ml (AIO: 2-3) and 30 ml (AIO: 111) of pure water to each of the three 100 ml aliquots, and manually shaking for about 30 seconds. Ivy. The back extract was analyzed for arsenic, zinc, copper and iron concentrations. The results are shown in Table 2. 85% by selecting the A/O ratio appropriately
It can be seen that an arsenic back extraction rate of

Example 2 A test was conducted according to the method of Example 1, except that isoamyl alcohol was used in place of n-butyl alcohol.

The leaching test results are shown in Table 3. Table 4 shows the results of back-extraction performed on the leached solution with an arsenic concentration of 18.26 vIe in the same manner as before.

Claims (1)

[Claims] 1. A substance containing arsenic and other metal components is brought into contact with a solvent containing an alcohol having 4 to 5 carbon atoms and sulfuric acid to selectively separate and extract arsenic, and the leached liquid is collected. A method for selectively separating arsenic, which comprises recovering arsenic. 2. The method according to claim 1, wherein the solvent contains an organic diluent. 3. A substance containing arsenic and other metal components is brought into contact with a solvent containing an alcohol having 4 to 5 carbon atoms and sulfuric acid to selectively separate and leached arsenic, and the leached liquid is back-extracted with water. Characteristic selective separation method for arsenic.