JPH10118649A - Treatment of molybdate aqueous solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a certain and efficient treatment method capable of separating and recovering molybdenum to reutilize an anticorrosive and to adapt waste water to environmental standard in addition as final treatment of cooling water containing a molybdenum component. SOLUTION: An aq. soln. containing molybdate is adjusted to pH1.0-8.0 and brought into contact with an anion exchange resin to adsorb molybdic acid ions to remove them and an alkali aq. soln. with pH9.0 or more is brought into contact with the anionic exchange resin having molybdic acid ions to dissolve molybdic acid ions to recover them and a waste soln. from which molybdenum is removed is treated with a known method.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates and removes molybdate from an aqueous solution containing molybdate, such as used cooling wastewater, and recycles the molybdate. It is about the method used. 2. Description of the Related Art Open or closed circulating cooling water includes:
Anticorrosives containing molybdate as an active ingredient are frequently used because of their low environmental pollution. This molybdenum component is recovered in the final treatment of used cooling water for effective use of resources. In the conventional method applied to molybdenum recovery, the used cooling water is acidified with hydrochloric acid, nitric acid, or the like, and then recovered as molybdenum acid by hydrolysis. Along with that, it was discharged and discharged. [0003] However, recently,
Molybdenum became a monitored item as a result of a partial review of environmental standards related to water pollution. Although the guideline value is 0.07 mg / l (liter) or less, the conventional wastewater treatment method has a problem that it is difficult to reliably reduce the molybdenum content in the wastewater to the guideline value or less. The present invention provides a method for final treatment of a cooling water containing a molybdenum component, in which molybdenum can be separated and recovered and reused as an anticorrosive agent, and at the same time, a reliable and efficient treatment of wastewater that meets the above environmental standards. The task is to provide a method. [0005] In order to solve the above problems, the present invention has the following configuration. That is, the present invention relates to a method for separating and recovering molybdate from an aqueous solution containing molybdate, wherein the aqueous solution has a pH of 1.0.
After adjusting the pH to 8.0 and contacting it with an anion-exchange resin to adsorb and remove molybdate ions, the aqueous solution of molybdate is brought into contact with an anion-exchange resin adsorbed with molybdate ions by contacting an alkaline aqueous solution having a pH of 9.0 or more. It is characterized in that ions are eluted and recovered, while the waste liquid from which molybdenum has been removed is subjected to wastewater treatment by a known method. In the treatment method of the present invention, the aqueous molybdate solution to be treated preferably has a pH of 1.0 to 8.0, more preferably 3.0 ± 2.0. If the pH exceeds the upper limit, the rate of adsorption and removal of molybdate ions decreases, and if the pH is less than the lower limit, the molybdate salt becomes unstable and the rate of adsorption and removal decreases. The pH of the molybdate aqueous solution is 1.0 to 8.0.
When it does not fall within the range, it is preferable to adjust the pH with an acid such as sulfuric acid or an alkali such as sodium hydroxide before contact with the anion exchange resin. [0007] By bringing an aqueous solution of molybdate having a pH value within the above-mentioned predetermined range into contact with an anion exchange resin, molybdate ions in the solution are adsorbed and removed. The waste liquid from which molybdate ions have been removed is subjected to wastewater treatment by a known method. As the anion exchange resin used in the present invention, a strongly basic anion exchange resin, a weakly basic anion exchange resin, a chelate type anion exchange resin and the like can be used. These anion exchange resins are usually subjected to a processing operation in a state where they are placed in a column 1 as shown in a sectional view of FIG. That is, a corrosion-resistant net 5 is provided at both ends of the column main body 3, and the column main body 3 is made of resin or steel whose inner surface has been subjected to anticorrosion treatment. The liquid can be passed through the pipe 11 provided. The column is usually fixed in a vertical shape, and the processing solution is passed from bottom to top. This method is preferable because the resin particles can be floated and both can be brought into more sufficient contact in the column, but there is no particular limitation on the fixed state of the column and the direction of liquid flow. Also, as a method of contacting both,
There is also a method of putting both into a single vessel, stirring lightly, and then filtering off, and any other method may be used as long as it can be brought into effective contact. It is possible that various anions other than molybdate are also adsorbed on the anion exchange resin to which molybdate has been adsorbed. In order to remove most of these miscellaneous ions, by contacting with a dilute alkali aqueous solution having a pH of less than 9.0, such as a 0.4 W / V% aqueous sodium hydroxide solution, the purity of the molybdate ion recovery operation described later is improved. Can be recovered. Subsequently, in order to recover molybdate ions from the anion exchange resin, an alkaline aqueous solution having a pH of 9.0 or more, such as a 4 W / V% aqueous sodium hydroxide solution, is brought into contact. As a result, molybdate ions separate from the anion exchange resin and dissolve and transfer into the alkaline aqueous solution,
Collected. After the molybdate ions have been recovered, the anion exchange resin can be regenerated to a state in which the molybdate ions can be adsorbed again by bringing the anion exchange resin into contact with an aqueous acid solution such as 3 W / V% sulfuric acid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically based on embodiments. (Example 1) 1 liter of a strongly basic ion exchange resin (trade name: Duolite A-171S, salt type) was put into a resin tower, and circulating cooling water (Mo 11.6 mg / l, p
H8.2) was adjusted to pH 3.0 with sulfuric acid, and then passed through SV4. When the liquid after the passage was measured by an ICP emission spectrometer, molybdenum could not be detected up to 80 liters (Mo <0.01 mg / l). Thereafter, a leak was seen little by little, and at 100 liters, the concentration was about 0.5% before passing through the liquid (Mo 0.05 mg / l). Elution regeneration was carried out by passing through 4 liters of sodium hydroxide (0.4%) to desorb most of the anions other than molybdate, and then passing through 1 liter of sodium hydroxide (4%).
Molybdic acid was eluted and the molybdenum (Mo) concentration was 1.2
g / l of eluate was collected. After washing the resin with water, sulfuric acid (3
%) And washed through 1 liter. When circulating cooling water was passed through the resin after the regeneration step, molybdenum was adsorbed again. The eluate adjusted to pH 8 by adding sulfuric acid could be used again as a circulating water additive. Table 1 shows the results of a similar experiment conducted by changing the pH value of the circulating cooling water. (Example 2) 1 liter of a weakly basic anion exchange resin (WA-30, salt type) was put into a resin tower, and circulating cooling water (Mo 10.1 mg / l, pH 8.5) was added to sulfuric acid at pH 2 using sulfuric acid. After adjusting to 0.5, the solution was passed through SV2. When the liquid after the passage was measured by an ICP emission spectrometer, molybdenum could not be detected up to 50 liters (Mo <0.02).
1 mg / l). After that, a leak was seen little by little,
At the liter, the concentration was about 0.5% before passage (Mo 0.05 mg / l). Elution regeneration is carried out by desorbing most of the anions other than molybdate through 2 liters of sodium hydroxide (0.4%), and then eluting molybdic acid through 1 liter of sodium hydroxide (4%) to obtain molybdenum (Mo). E) An eluate having a concentration of 1.0 g / l was recovered. After washing with water, the resin was washed with 1 liter of sulfuric acid (3%). When circulating cooling water was passed through the resin after the regeneration step, molybdenum was adsorbed again. Table 1 shows the results of a similar experiment conducted by changing the pH value of the circulating cooling water. Example 3 A chelate resin (CR-20,
1 liter of free type is put into a resin tower, and circulating cooling water (Mo)
(11.1 mg / l, pH 8.1) was adjusted to pH 3.5 with sulfuric acid, and the solution was passed through SV4. When the liquid after the passage was measured by an ICP emission spectrometer, molybdenum could not be detected up to 80 liters (Mo <0.01 mg / l).
Thereafter, a leak was seen little by little, and at 90 liters, the concentration was about 0.5% before passing through the liquid (Mo 0. 1).
05 mg / l). Elution regeneration was performed using sodium hydroxide (0.
4%) After desorbing most of the anions other than molybdate through 2 liters, sodium hydroxide (4%) 1
Molybdic acid was eluted through the liter, and an eluate having a molybdenum (Mo) concentration of 0.9 g / l was recovered. After washing with water, the resin was washed with 1 liter of sulfuric acid (3%). When circulating cooling water was passed through the resin after the regeneration step, molybdenum was adsorbed again. The eluate adjusted to pH 8 by adding sulfuric acid could be used again as a circulating water additive. Table 1 shows the results of a similar experiment conducted by changing the pH value of the circulating cooling water. [Table 1] As is apparent from the above results, the present invention is an excellent method as an efficient method for removing and recovering molybdenum and a method that can meet environmental standards for wastewater treatment. is there.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an anion exchange resin column used in the present invention. FIG. 2 is a process diagram of the present invention. (1) Step of adsorbing and removing molybdate ions from an aqueous solution (2) Step of removing miscellaneous ions from an anion exchange resin (3) Step of recovering molybdate ions from an anion exchange resin (4) Using an anion exchange resin Regeneration process [Explanation of symbols] 1 Anion exchange resin column 3 Column body 5 Net 7 Anion exchange resin 9 End 11 Pipe

Claims (1)

Claims 1. An aqueous solution containing a molybdate salt having a pH of 1.
After adjusting to 0 to 8.0 and adsorbing and removing molybdate ions by contacting with an anion exchange resin, an alkali aqueous solution having a pH of 9.0 or more is brought into contact with the anion exchange resin having adsorbed molybdate ions. A method for treating an aqueous solution of molybdate, wherein a molybdate ion is eluted and recovered, and a waste liquid from which molybdenum has been removed is subjected to wastewater treatment by a known method.