JPS621570B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for concentrating and recovering indium from an aqueous sulfuric acid solution or an aqueous silicofluoric acid solution containing indium and tin by solvent extraction. Indium exists in extremely small amounts in various raw material ores for smelting, such as zinc, lead, copper, and tin, and does not exist as an ore of indium alone. Therefore, recovering indium by processing these smelting intermediate products containing trace amounts of indium requires separation operations from many other metals such as copper, zinc, tin, cadmium, arsenic, etc. Therefore, many processes had to be combined, which could not be said to be very advantageous from an industrial or economic point of view. However, in recent years, solvent extraction technology has developed, and many methods have been published for extracting and concentrating indium from an aqueous solution containing indium. As mentioned above, in the case where indium ions and tin ions coexist, for example, in the reflux solution of tin electrolytic refining, tin electrolysis, lead-tin alloy electrolyte, etc., indium is accumulated and tin ions and tin ions coexist. This invention relates to a method for effectively separating indium and tin and concentrating indium when they coexist. Originally, indium and tin have similar electrochemical properties, and although the tin in the electrolyte is mainly divalent, some of it is oxidized and becomes tetravalent, so their coexistence state is simple. isn't it. Solvent extraction of indium ions and tin ions is possible with an organic solvent containing dialkyl phosphoric acid, and an aqueous solution containing 500 g or less of free sulfuric acid or hydrochloric acid from the above organic solvent containing extracted indium ions and tin ions. A method for back-extracting indium and tin using an aqueous solution containing the above is disclosed in US Pat. However, in these known methods, both indium and tin ions are back-extracted at the same time even if the concentration of each back-extraction solution, O/A ratio, or contact time during back-extraction is varied, and sufficient separation effects are achieved. I couldn't give you anything. In addition, when back-extracting the organic solvent containing dialkyl phosphoric acid from which indium and tin were extracted with sulfuric acid, 500
In mixed contact with an aqueous solution containing more than g/g of free sulfuric acid, a third phase is formed between the extract and the phase separation, and as mentioned above, the separability of indium and tin is also poor. It has been said that an aqueous solution with a sulfuric acid concentration exceeding 500 g/ml cannot be used for back extraction of this solvent. Furthermore, as a method for separating indium and tin, a method has been proposed in which tin ions are first separated by displacement using zinc powder, followed by the above-mentioned solvent extraction, and then back-extracted with hydrochloric acid. On the contrary, zinc is dissolved in the zinc dust replacement process, and the electrolyte itself cannot be reused, so it is necessary to create and adjust a new electrolyte. Furthermore, since the recovered tin sponge contains a large amount of undissolved zinc, an additional process is required to recover the tin. The present inventors solved the above-mentioned drawbacks of the prior art,
In order to provide a method for recovering indium by extracting and recovering indium in a high yield from a sulfuric acid aqueous solution or a silicofluoric acid aqueous solution containing indium and tin, and by which the aqueous solution from which indium has been extracted can be used again for electrolysis, we are conducting studies. As a result of repeated efforts, it was discovered that the object could be achieved by increasing the free sulfuric acid concentration of the sulfuric acid solution for back extraction combined with extraction with an organic solvent containing alkyl phosphoric acid, and the present invention was achieved. That is, the gist of the present invention is to bring a sulfuric acid acidic aqueous solution or a silicofluoric acid aqueous solution containing indium ions and tin ions into contact with an organic solvent solution containing an alkyl phosphoric acid to remove the indium ions and tin ions from the organic solvent solution. Then, the organic solvent solution containing the extracted indium ions and tin ions is brought into contact with a sulfuric acid acid aqueous solution containing free sulfuric acid in the range of 550 g/~1000 g/ to convert the tin ions into crystals of tin sulfate. A method for recovering indium, characterized by including a selective detinning step of back extraction into an acidic aqueous solution of sulfuric acid. As described above, according to the present invention, when back-extracting an organic solvent containing dialkyl phosphoric acid from which indium and tin was extracted with sulfuric acid, it has been said that an aqueous sulfuric acid solution containing 500 g/or more of free sulfuric acid cannot be used. On the other hand, for back extraction of organic solvent containing alkyl phosphate from which indium and tin were extracted, 550g/
By using an aqueous sulfuric acid solution containing free sulfuric acid in the range of ~1000 g/m, only the tin ions in the extraction solvent are selectively precipitated as crystals of tin sulfate in the sulfuric acid back extract, and If solid-liquid separation is performed using a well-known technique such as a technique, and then liquid phase separation is performed, the third phase disappears, phase separation is easily performed, and a solvent phase with a high abundance ratio of In/Sn is obtained. . This solvent phase with an increased abundance ratio of In/Sn can be easily extracted as a concentrated aqueous solution of indium by back-extraction using known hydrochloric acid. In the present invention, the alkyl phosphoric acid used for extraction of indium and tin ions includes di- or mono-alkyl esters of phosphoric acid, phosphorous acid, or hypophosphorous acid, and the alkyl group is about the size of an octyl group, which is added to the aqueous solution phase. It is preferable because the loss is small. Specifically, they include di-2-ethylhexyl phosphoric acid, 2-ethylhexyl phosphoric acid, 2-ethylexylphonic acid, and mixtures thereof. The organic solvent for dissolving these alkyl phosphoric acids may be any stable compound that does not mix with water and can freely dissolve the alkyl phosphoric acids, such as paraffinic kerosene, Schielzol 70, naphthenic dispazole, aromatic solvents, etc. Although it is possible to use Cierzol A, which is based on Cielsol A, kerosene is preferred because it is inexpensive. Next, the free sulfuric acid concentration of the sulfuric acid acidic aqueous solution used for back extraction is in the range of 550 g/ to 1000 g/, preferably in the range of 600 g/ to 850 g/. When the free sulfuric acid concentration is less than 550 g/min, the tin removal rate by back extraction decreases and the amount of tin remaining in the organic phase increases. Furthermore, if the concentration of free sulfuric acid exceeds 1000g/, the amount of indium that is back-extracted with tin increases, which is undesirable, and in some cases, deterioration of the compound used in the organic phase is observed. is the upper limit. The effects of the present invention are as follows. (1) Since the detinning rate in the sulfuric acid back extraction process is high, the tin content in the indium concentrated aqueous solution obtained in the hydrochloric acid back extraction process is low, making it easy to remove tin (cementation with indium) from this solution. It is possible to recover indium in high yield. (2) Conventionally, when recovering indium accumulated in the solution of tin electrolysis, lead electrolysis, lead-tin alloy electrolysis, etc. by solvent extraction, a detining process (replacement separation with zinc powder) is required prior to the solvent extraction. As a result,
It could not be reused as an electrolyte.
However, according to the present invention, a detining process (concentrated sulfuric acid back extraction process) is provided for the organic phase separated after solvent extraction, and the aqueous phase after solvent extraction contains less tin than the raw electrolyte. Since there was no change in the amount of silicofluoric acid radicals except that the content of indium and indium decreased, tin sulfate crystals were dissolved in the aqueous phase after the solvent extraction to return the tin ion concentration to the original electrolyte, and the electrolyte was prepared. It can be reused as (3) The sulfuric acid solution from which the liquid phase has been separated can be repeatedly used as a back extraction solution for detining by simply replenishing the amount of sulfuric acid consumed as tin sulfate. Moreover, indium ions are contained in a certain amount in this sulfuric acid solution. Since it is not further concentrated, there is no effect on the recovery of indium. (4) The higher the concentration of sulfuric acid used, the greater the O/A ratio can be selected, which is very advantageous in actual operation. The separated and recovered tin sulfate is precipitated as crystals and has very high purity as tin sulfate. Therefore, it can be said that the present invention also provides a method for recovering tin sulfate crystals. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 Approximately 7 g/indium ion, approx. 35 tin ion
Solvent 8 (O/
A=4:5), perform the extraction operation at room temperature,
Next, free sulfuric acid 650g/reverse extraction sulfuric acid solution for detining
After obtaining crystals of tin sulfate with 800 ml (O/A = 10:1), phase separation was performed, and 7N hydrochloric acid 1 (O/A = 8:
Table 1 shows the results obtained when performing the series of steps for back-extracting indium in 1).

【table】

[Table] From Table 1, the contents of In and Sn present in the organic solvent solution before and after treatment in the sulfuric acid detinning process and the back extraction rate after treatment are as shown in Table 2. The tin effect is clear.

[Table] Comparative Example As in Example 1, 10% of the sulfuric acid acidic silicofluoric acid tin electrolyte containing indium and tin was mixed with 1% of D2EHPA.
An extraction operation was performed using 8 mol/kerosene solution, and then the organic solvent solution was directly subjected to hydrochloric acid back extraction without sulfuric acid detinning, and the results shown in Table 3 were obtained. As shown in Table 3, hydrochloric acid back extraction is as follows: (a) Two-stage back extraction with 6N hydrochloric acid and 9N hydrochloric acid (b) One-stage back extraction with 8N hydrochloric acid

【table】

[Table] (c) One-stage back extraction using 9N hydrochloric acid was performed under three conditions. Comparing the In and Sn contents of the hydrochloric acid back extraction solution and the ratio to the original liquid in Table 3 with the data in Table 1 according to the method of the present invention, the effect of providing the sulfuric acid detinning step becomes even clearer.

Claims (1)

[Claims] 1. Extracting the indium ions and tin ions into the organic solvent solution by contacting a sulfuric acid acidic aqueous solution or a silicofluoric acid aqueous solution containing indium ions and tin ions with an organic solvent solution containing an alkylphosphoric acid,
Next, 550 g/~1000 g/
A method for recovering indium, the method comprising a selective detinning step of contacting with an aqueous sulfuric acid solution containing free sulfuric acid in the range of 1 to 1, and back-extracting the tin ions as crystals of tin sulfate into the aqueous sulfuric acid solution.