JPS5950025A - Method for separating and recovering gallium from waste water - Google Patents

Abstract

PURPOSE:To recover Ga from waste water contg. Ga in a high yield by adjusting the waste water to a specified pH, adding a soluble Al salt to the waste water to precipitate Ga and Al(OH)3 together, dissolving the precipitate in hydrochloric acid, and carrying out extraction with ethyl ether. CONSTITUTION:Waste water contg. Ga discharged from a stage in the electronic industry or the like is adjusted to 5-9pH. A soluble Al salt is added to the waste water so as to make the concn. of Al>=400mg/l, thereby precipitating Ga and Al(OH)3 together. The precipitate is separated by filtration and dissolved in hydrochloric acid to prepare 5.5-6N hydrochloric acid soln. Ethyl ether is added to the soln. to extract Ga from the soln. The ethyl ether layer contg. the extracted Ga is separated, and the Ga is recovered by removing the exhyl ether by evaporation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and recovering gallium from wastewater, that is, a method for separating and recovering gallium, which is a valuable metal, from factory wastewater from the electronics industry, mining industry, etc., which contains high concentrations of gallium. be.

Recently, demand for gallium as a raw material for semiconductor materials such as GaA1 has been increasing, but since it is a rare element, its production consumes a large amount of energy and is inevitably expensive. Therefore, separating and recovering gallium from industrial wastewater containing high concentrations is useful for energy conservation and effective use of resources, and is also meaningful from the viewpoint of preventing environmental pollution.

Gallium is quantitatively extracted in ethyl ether in the form of HGaCfi from a 5.5-6N hydrochloric acid solution. However, there are various problems in directly applying this method to wastewater to separate and recover gallium, and it has not been put to practical use so far.

When separating and recovering gallium from wastewater, the present invention first adjusts the pH of the wastewater, adds an appropriate amount of soluble aluminum salt, co-precipitates gallium with aluminum hydroxide, and precipitates the gallium with aluminum hydroxide. By applying the ether extraction method, we have achieved a recovery effect that was previously unimaginable.

According to the present invention, the pH of wastewater containing gallium is adjusted to 5 or more and 9 or less, a soluble alkium salt is added to the wastewater to coprecipitate gallium with aluminum hydroxide, and the precipitate is filtered. After separation, dissolve with hydrochloric acid to 5.5~
6. A method for separating and recovering gallium from wastewater is obtained, which is characterized in that it includes a step of preparing an ON hydrochloric acid solution, adding ethyl ether, and extracting gallium with ethyl ether.

The present invention will be explained below. Co-precipitation conditions for aluminum and gallium were investigated using simulated wastewater prepared by dissolving gallium oxide. The types of neutralizing agents used to adjust the pH are limited, but for acidic wastewater, calcium carbonate, calcium hydroxide, caustic soda, etc. can be used. Table 1 shows the results of a study on the amounts added when calcium carbonate and calcium hydroxide were used as neutralizing agents.

Table 1 Table 1 shows the pH when a 1M solution of each neutralizing agent was added to 100 grams of an 11000pp aluminum solution and stirred for 10 minutes to precipitate aluminum, and the Afi concentration of the filtrate after precipitation filtration. According to the results in Table 1, the amount of the neutralizing agent added may be 7.5 or more for a 1M calcium carbonate solution and 5 or more for a 1M calcium hydroxide solution, with a smaller amount of calcium hydroxide being required. However, it was confirmed that the pH must be between 5 and 9 for coprecipitation regardless of the type of neutralizing agent. For alkaline wastewater, it is necessary to adjust the pH to this range with an acid.

Next, FIG. 1 shows the results of a study on the aluminum+=-um concentration required for efficient co-precipitation separation of gallium from wastewater. Figure 1 shows gallium at 50 and zootr
The gallium concentration in the simulated wastewater when gallium is coprecipitated and separated by varying the aluminum concentration added to the simulated wastewater containing q/Il is shown. The amounts of 1M calcium carbonate solution added to each concentration of gallium solution 100- were 7.5- and 10-, respectively. The stirring time after addition of the neutralizing agent was 10 minutes.

The horizontal axis indicates the concentration of added aluminum, which is shown in a semi-logarithmic graph. In the figure, the solid line (O-O) is a plot when the initial concentration of gallium is 50η/ρ and the amount of 1M calcium carbonate solution added is 7.5-.

all(・・・・・・・・・) has an initial concentration of gallium of 20
At 0q/Jl, the amount of 1M calcium carbonate solution added is 10-
This is the plot at the time of .

From Figure 1, gallium co-precipitates with calcium carbonate up to a certain concentration even without adding aluminum, but in order to completely separate it, it is necessary to add aluminum, and when the aluminum concentration exceeds 40011v/1, gallium co-precipitates with calcium carbonate. Almost complete coprecipitation separation is possible.

A detailed comparison of the results for gallium concentration 50/i and 200111F/1 reveals that the lower the gallium concentration, the lower the aluminum concentration.

Based on the above results, the conditions for co-precipitation separation of gallium in wastewater with aluminum were set as follows.

Aluminum concentration = 400■/ρ or more pH during coprecipitation: 5.0 to 9.0 Stirring time: 10 minutes 5- Now that the conditions for co-precipitation separation of gallium were set, we next considered the separation of gallium from the precipitate. .

In Kempo, the precipitate was neutralized and dissolved with hydrochloric acid, the hydrochloric acid concentration of the solution was adjusted to 5.5 to 6 NK, and then gallium was extracted and separated with ethyl ether.Table 22 and Table 3 show examples.

The reason why we limited the hydrochloric acid concentration to t-5, 5 to 6N is because the extraction rate of gallium decreases rapidly below 5.5N.Also, the higher the hydrochloric acid concentration, the higher the extraction efficiency.
According to K, in addition to exceeding Nt, there is no practical advantage.

6- The solution amount in the example shown in Table 2 was 200 mg, and the gallium concentration in the example shown in Table 3 was tooiv/fi. The implementation procedure is as follows. The coprecipitated precipitate was neutralized and dissolved to make 25-, and 12N hydrochloric acid was added to make the total amount 50-. Transfer this solution to a separating funnel and add 50w of ethyl ether.
t1 was added. The mixture was shaken for 10 minutes using a shaker, and after being left for 10 minutes, the ether layer was separated. Ether was removed by evaporation and gallium was recovered as a residue. In Tables 2 and 3, gallium is obtained when the ether evaporation residue is dissolved in pure water to make the total amount 100 mg.

The concentrations of aluminum and calcium and the recovery rate of gallium are shown.

The recovery rate of gallium shown in the table is over 92cm,
Considering losses during the operation, the recovery rate is thought to be close to 100%. As shown in the table, the degree of extraction of aluminum and calcium, which coexisted in large quantities in the precipitation, with ether was very low, and they were almost completely separated from gallium.

In addition, it was confirmed in another experiment that most of the elements expected to coexist in wastewater, except for iron, can be separated from gallium by the ethyl ether extraction method. Iron can also be separated from cigallium by the ethyl ether extraction method by adding a suitable reducing agent such as hydroxylamine hydrochloride or sulfite to convert it into Fe(n).

The present invention has the effect of selectively separating and recovering gallium from wastewater at a very high recovery rate.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the gallium concentration in the solution after precipitation separation when gallium is coprecipitated while changing the aluminum concentration. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] pHt of wastewater containing gallium? Adding a soluble aluminum salt to this wastewater to adjust the concentration to 5 or more and 9 or less to co-precipitate gallium with 7 aluminum 4 hydroxide; and 5) dissolving the precipitate with hydrochloric acid after separating it by filtration. 5-6. ON
1. A method for separating and recovering gallium from wastewater, comprising the steps of converting it into a hydrochloric acid solution, adding ethyl ether, and extracting gallium with ethyl ether.