JPH0236533B2 - MORIBUDENSANENGANJUSUIYOEKIKARAMORIBUDENSANENOKAISHUSURUHOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for recovering molybdate from an aqueous solution containing molybdate. Industrially, molybdenum can be recovered from a molybdate-containing aqueous solution by dissolving molybdenum trioxide obtained by roasting molybdenum concentrate in an alkaline aqueous solution to obtain a molybdate aqueous solution, and then concentrating the molybdate solution under reduced pressure. It can be crystallized as a salt {Na ₂ MoO ₇・2H ₂ O or (NH ₄ ) ₆ Mo ₇ O ₂₄・4H ₂ O} or recovered as molybdic acid (H ₂ MoO ₄ ) by acid decomposition with hydrochloric acid or nitric acid. method is being carried out. However, the crystallization method requires a great deal of energy and time to evaporate and concentrate the solution. Furthermore, the acid precipitation method has the disadvantage that the precipitation of molybdic acid is greatly affected by the electrolyte such as sodium chloride contained in the solution and the amount of acid added. The present inventor added ammonium salt to an aqueous solution containing molybdenum and vanadium to precipitate vanadate, and when solid-liquid separation was performed by filtration, the precipitated salt was washed with water, which caused a large dissolution of the precipitated salt. When washed with ethanol, it was found that the filtrate became cloudy and at the same time a white precipitate was deposited, and it was analyzed that this cloudiness was composed of molybdate. The present inventor focused on the fact that molybdate precipitates when alcohol is added to this molybdate-containing aqueous solution, conducted extensive research, and came up with the present invention. According to the method of the present invention, molybdate can be precipitated and recovered by adding a lower alcohol or acetone that dissolves in an arbitrary ratio with water to a molybdenum-containing aqueous solution. In the present invention, organic solvents used for molybdate precipitation are lower alcohols such as methanol, ethanol, propanol, butanol, and acetone. Further, molybdate-containing aqueous solutions targeted by the present invention include ammonium molybdate and sodium molybdate solutions. When the organic solvent is added to the molybdate-containing aqueous solution while stirring, white powdery crystals are immediately precipitated, and the precipitation of the molybdate is completed in a short time. The molybdate precipitate rate increases as the molybdate concentration and the amount of organic solvent added increase. Furthermore, the relationship between the organic solvent and the precipitation rate of molybdate was in the following order: methanol < ethanol < propanol < butanol < acetone. of solution
Regarding the relationship between pH and molybdate precipitation rate,
In the pH range from 5.5 to 10, the precipitation rate of molybdate decreased as the pH increased, but the difference was 2.
% or less. In the precipitation temperature range of 5°C to 40°C, the precipitation rate of molybdate slightly decreased as the temperature increased, but a room temperature precipitation temperature is sufficient. Note that even in a low-concentration molybdate solution in which molybdate does not precipitate only by adding an organic solvent, molybdate can be precipitated by adding an ammonium salt. The molybdate precipitated from the molybdate-containing aqueous solution by adding an organic solvent in this manner can be separated by a solid-liquid separation method such as filtration or centrifugation, and then dried and recovered as a molybdate. The precipitate from the ammonium molybdate aqueous solution is (NH ₄ ) ₆ Mo ₇ O ₂₄・4H ₂ O, and the precipitate from the sodium molybdate solution is Na ₂ MoO ₄・2H ₂ O.
Fixed by line diffraction. Further, the organic solvent contained in the filtrate can be recovered and reused by a known method. Examples Next, examples of the present invention will be shown. Example 1 An organic solvent was added to a (NH ₄ ) ₂ MoO ₄ solution with a Mo concentration of 110 g/, pH 8 in an amount 5 times the amount of the (NH ₄ ) ₂ MoO ₄ solution, and molybdate was precipitated.
The recovery rates were 96.4% for methanol, 98.2% for ethanol, 98.6% for 2-propanol, 98.7% for 1-butanol, and 99.8% for acetone. Example 2 Recovery rate as Mo when molybdate was precipitated by adding methanol and ethanol 5 times the amount of the Na ₂ MoO ₄ solution to a Na ₂ MoO ₄ solution with a Mo concentration of 100 g/pH 7.6 was 91.0% methanol and 99.1% ethanol. Example 3 Methanol was added to a (NH ₄ ) ₂ MoO ₄ solution with a Mo concentration of 100 g/PH 5.5 to precipitate molybdate, and the methanol addition amount ratio and the recovery rate of molybdate as Mo The relationship is shown in Table 1.

[Table] Example 4 Mo concentration when 10 times the amount of methanol was added to the (NH ₄ ) ₂ MoO ₄ solution adjusted to various Mo concentrations.
Table 2 shows the relationship between Mo recovery rates.

[Table] Example 5 Mo does not precipitate only by adding methanol
When NH ₄ Cl is added to a (NH ₄ ) ₂ MoO ₄ solution with a concentration of 6.5 g/methanol and 10 times the amount of methanol is added,
Table 3 shows the relationship between NH ₄ Cl concentration and Mo recovery rate.

【table】

Claims (1)

[Claims] 1. A method for recovering molybdate from a molybdate-containing aqueous solution, which comprises adding a lower alcohol or acetone to the molybdate-containing aqueous solution to precipitate the molybdate and separating the precipitate.