JPS6042169B2 - Arsenic recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering arsenic from arsenic-containing solutions, and particularly relates to a method for recovering arsenic from arsenic-containing solutions such as dilute sulfuric acid produced in the sulfuric acid production process in non-ferrous metal smelting. This invention relates to a method for selectively recovering arsenic using an extraction method.

The solution after electrolysis in nonferrous metal smelting or dilute sulfuric acid from the sulfuric acid manufacturing process contains a considerable amount of arsenic.
Recently, attempts have been made to recover arsenic from these arsenic-containing solutions for the purpose of preventing pollution or recovering arsenic as a by-product.

The conventional arsenic recovery method involves converting arsenic into arsenic sulfide using a sulfurization method, and then separating and recovering it by filtration, and removing water by approximately 7.
A dehydrated cake containing 0% was prepared, and then the resulting cake was further dehydrated and agglomerated, and the resulting cake was stored in a pit. Although this method is simple, it requires a large amount of storage space. Recently, a method has been proposed for recovering arsenic sulfide obtained by the above-mentioned sulfurization method as arsenous acid. In this method, arsenic sulfide produced by the sulfurization method is oxidized and leached out, and the leachate is reduced, then concentrated and concentrated, but the process is long and complicated, and requires troublesome operations. Unlike the conventional methods mentioned above, there is no substitute for recovering arsenic directly from an arsenic-containing solution.

There is a method called solvent extraction method that makes this possible. 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. Therefore, in order to use the solvent extraction method to recover arsenic from arsenic-containing aqueous solutions, it is necessary to develop an extractant that has the ability to selectively and efficiently extract arsenic ions from aqueous solutions. . In this case, the extractant needs to be immiscible with the arsenic-containing aqueous solution, and the extractant must be diluted with a diluent to reduce its viscosity, improve dispersibility, and increase contact efficiency. Since it is commonly used, it is also necessary that it dissolves well in the diluent. In addition, since back-extraction is performed after the extraction operation, it is also necessary to easily perform the back-extraction operation. Under these various considerations, the present inventor conducted many trials on extractants for extracting arsenic from arsenic-containing aqueous solutions by solvent extraction, and as a result, the inventors discovered dialkyldithiophosphate (alkyl group having 8 to 10 carbon atoms).
) was found to be suitable for use as the above-mentioned extractant.

This extractant has extremely high selectivity for arsenic, and by appropriately selecting conditions, it is possible to extract more than 99% of arsenic, and back-extraction operations can be performed relatively easily using an alkaline solution. The dialkyldithiophosphate ester having an alkyl group having 8 to 10 carbon atoms used as an extractant in the present invention has the following structural formula: (wherein R is 8 to 10)
They are alkyl groups having 10 carbon atoms, and may be the same or different.

) Thus, the present invention provides a method for recovering arsenic, which comprises contacting a solution containing arsenic with an organic solvent containing as an extractant a dialkyldithiophosphate having an alkyl group having 8 to 10 carbon atoms. .

Furthermore, the present invention provides a solution containing arsenic with a carbon number of 8 to 1.
Arsenic removal consists of contacting with an organic solvent containing a dialkyldithiophosphate having 0 alkyl groups as an extractant, transferring arsenic into the organic solvent, and then back-extracting the arsenic-containing extraction solvent with an alkaline solution. Provide collection methods.

The solvent extraction operation in the present invention is carried out by bringing an arsenic-containing solution into contact with an organic solvent prepared by dissolving the above extractant in a diluent.

As the diluent, mineral oil, mineral oil+alcohol, toluene, etc. are preferably used. The arsenic-containing solution is preferably an acidic solution. For example, in the case of a sulfuric acid solution, it is preferable to use a sulfuric acid acidic solution with a pH of 4 or less. The contacting operation can be carried out either batchwise or continuously using well-known mixer-settler equipment, extraction towers, centrifugal extractors, and the like. The mixing temperature is 10-80°C, preferably 20-80°C depending on the diluent used.
60'C. The volume ratio of the organic phase (organic solvent) to the aqueous phase (liquid to be treated) during contact (hereinafter referred to as 0/A ratio) is about 1/15 to 5/1, preferably 1/2 to 2/1. can be selected as appropriate depending on the equipment used and operating conditions. The contact time depends on the contact efficiency, but 2 to 30 minutes, and usually about 5 to 1 powder is sufficient, so the organic solvent after arsenic extraction is separated from the liquid to be treated and then subjected to a back extraction operation.
As a back-extracting agent, an alkaline solution such as sodium carbonate or ammonium carbonate is used. As for the back extraction conditions, the temperature is 10 to 80°C, preferably 20 to 60°C, and the 0/A ratio is 1/5 to 10/1, preferably 2/1 to
5/1 and the contact time is 2-3 times, preferably 5 times.
It is said to be a mistake. The organic solvent after back extraction is recycled and reused. Example 1 50 ml of aqueous solution containing 9.98yIe of As(■)
After adjusting the sulfuric acid concentration to 1 to 5 to 10 to 300 and 600yIe, diluted with an organic solvent in which di-2-ethylhexyldithiophosphoric acid as an extractant was diluted to 20% with Despersol (trade name of Shell Chemical) as a diluent. An extraction test was conducted.

The extraction conditions were as follows: temperature 50°C, time 10 minutes,
Stirring blade rotation speed 750r″PmlO/A=50m1/5
The arsenic extraction rate obtained is shown in the table below. As can be seen from the table, the present invention achieves an extremely high arsenic extraction rate of 99% or more. Example 2 An extraction test was conducted under the same conditions as in Example 1 using di3,5,5-trimethylhexylthiophosphate and diisodecyl dithiophosphate as extractants.

The sulfuric acid concentration was 100 qIe. All showed a high extraction rate of 99% or more. Example 3 100ml of an arsenic-containing solution containing 9.98y1e(7)AS(■) and 10yIe of sulfuric acid was extracted in the same manner as in Example 1 to obtain an extraction containing 11.32 daI' of As(■). A post-solvent was obtained.

However, the O/A ratio was 50 mt/100 mt. After this extraction, 50 ml of solvent was back-extracted with 100 ml each of 0.5 molar sodium carbonate solution and 0.5 molar ammonium carbonate solution. The back extraction conditions were a temperature of 50°C and a contact time of 1 extraction. The following back extraction rates were obtained. As explained above, the present invention can easily separate arsenic from an arsenic-containing solution,
It is possible to recover highly pure arsenic compounds from the recovered liquid, and the arsenic can be recovered more effectively and easily than conventional methods, so it has great industrial significance.

Claims (1)

[Scope of Claims] 1. A method for recovering arsenic, which comprises contacting a solution containing arsenic with an organic solvent containing a dialkyldithiophosphate having an alkyl group having 8 to 10 carbon atoms as an extractant. 2. Contacting a solution containing arsenic with an organic solvent containing a dialkyldithiophosphate having an alkyl group having 8 to 10 carbon atoms as an extractant, and back-extracting the arsenic-containing post-extraction solvent with an alkaline solution. How to recover arsenic.