JP2015010032A - Separation and recovery of fluoronitric acid and titanium using electrical conductivity meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for improving separability of a metal salt and an acid, and increasing a rate of recovery thereof while realizing stable control in view of the problem that, while conventional separation and recovery of a metal salt and an acid employed a chromatographic separation method by means of an acid retardation method with a prerequisite that, in this method, a fluoride of titanium is eluted first followed by elution of an acid, an application of the acid retardation method has been difficult when a titanium plate is etched with fluoronitric acid because, in this case, not a salt of TiFbut a complex of [TiF]is formed, which is adsorbed by a conventional ion exchange resin.SOLUTION: Provided is a method for recovering an acid and titanium, comprising: recovering an acid by adsorbing a titanium fluoro complex in fluoronitric acid by a strong anion exchange resin; and subsequently flowing water as an eluent whereby, with decrease in acid concentration, the titanium fluoro complex is converted to a fluoro-aquo complex which is eluted from the anion exchange resin. Switching of a valve is performed automatically by measuring an acid concentration by an EC meter.

Description

  The present invention relates to the field of separation and recovery of hydrofluoric acid and titanium by detecting the acid concentration of titanium-containing hydrofluoric acid with an electric conductivity meter (EC meter).

Separation and recovery of metal salt and free acid from metal hydrofluoric acid etching solution, acid recovery methods include diffusion dialysis membrane, electrodialysis, pressure dialysis, and acid retardation method of chromatographic separation with strong anion exchange resin. In recent years, the acid retardation method has become the mainstream.
For the chromatographic separation of acid salt recovery of metal salts and acids currently being carried out, the Rf value (transfer rate) is measured, and the flow time is measured by SV (liquid flow ratio to L / r-L resin volume). Separation method is performed.

Japanese Patent Application No. 2006-528972

Chromatographic separation by the acid retardation method, which is a conventional metal and acid recovery method, measures the Rf value (transfer rate) and separates it by the flow time using SV (liquid flow rate ratio to L / r-L resin). The way was done.
This method is based on the premise that "fluoride of titanium is eluted first, and then acid is eluted later". However, when a titanium plate is etched with hydrofluoric acid, a complex of [TiF ₆ ] ²⁻ is formed instead of a salt of TiF ₄ , and it is difficult to apply the acid retardation method.

After passing the acid solution of the chloro complex of indium through the strong anion exchange resin as described in Japanese Patent Application No. 2006-528972, an electric conductivity meter is provided on the outlet side, and the acid solution is passed while measuring the acid concentration. Pass the developing solution (water) through. When the acid is first recovered and the acid concentration in the resin is lowered by passing water, the chloro complex becomes a chloroaco complex.
Similarly, titanium in hydrofluoric acid is adsorbed on the resin as a titanium fluoro complex which is an anion and does not come out at first. Only acid is mainly discharged. After the acid is recovered, when water is flowed as developing water, the titanium fluorocomplex becomes a fluoroaquo complex and elutes from the strong anion exchange resin as the acid concentration decreases. FIG. 5 shows the mechanism. The valve is automatically switched by an EC meter, and acid separation and titanium separation / recovery are performed by measuring the acid concentration by EC to improve separation ability and recovery rate.

  In the acid recovery and titanium recovery device using the electric conductivity meter developed this time from the acid recovery flow sheet shown in FIG. 1, the waste acid is opened from the T-1 acid tank by opening the MV1 electric valve, and P-1 (AQ pump ) Through pipe (1), remove suspended solids (SS) with a T-6 microfilter, and then measure the acid concentration of the liquid through the T-5AQ resin tower and the EC value while measuring the electrical conductivity (EC). Is sent to the T-3 metal solution tank through the pipe (4) with the MV3 electric valve being opened up to 2-6 S / m.

  When the acid begins to come out and the electrical conductivity (EC) value is 2 to 6 S / m, the MV3 electric valve is closed and the MV4 electric valve is opened, and the recovered acid passes through the pipe (5) to the T-4 recovered acid tank. Sent. Next, when EC15 to 20 S / m, the MV1 electric valve is closed and the MV2 electric valve is opened. Water from the T-2 water tank, which is the developing solution, passes through the T-6 microfilter in the pipe (2) and then passes through the T-5AQ resin tower, where the MV4 electric valve is opened. 4 Liquid is sent to the recovered acid tank. The liquid passed through is recovered acid.

  When the electrical conductivity (EC) drops and reaches EC10-15S / m, the MV2 electric valve is opened, the MV3 electric valve is opened, the MV4 electric valve is closed, and the water as the developing liquid is piped from the T-2 water tank. 2) Via a T-6 microfilter and a T-5AQ resin tower, and sent to a T-3 metal solution tank as a metal solution through a pipe (5).

  As metal recovery proceeds, the electrical conductivity (EC) decreases. When the electrical conductivity (EC) reaches 1 to 5 S / m, the MV1 electric valve is opened, the MV2 electric valve is closed, the MV3 electric valve is opened, and the MV4 electric valve is closed to complete one cycle of the acid recovery process. The same process is performed again. Waste acid is sent from the T-1 acid tank to the T-5AQ resin tower and the recovery process is started. This process is continuously controlled by an electric conductivity meter to separate and recover the metal solution and the acid.

  Until now, separation and recovery of metal salts and acids have been performed by the acid retardation method using a strong anion exchange resin. However, it is difficult to apply this method to the production of chloro complexes or fluoro complexes with hydrochloric acid or hydrofluoric acid. The acid is first recovered, and then the metal that has become chloro aco complex or fluoro aco complex as the acid concentration decreases is eluted. Come on. Using this principle, the metal and recovered acid are switched while detecting the decrease in acid concentration with an EC meter, so the separation and recovery of the metal salt and acid are improved and stable control is realized. And versatility has increased.

Acid recovery flow sheet Electrical conductivity (EC) and free acid chromatograph Titanium and free acid chromatograph Acid recovery rate, metal removal rate Forms of fluorotitanium complex and fluoroacotitanium complex

Using a strong hydrofluoric acid solution of titanium, a strong anion exchange resin was used to recover the titanium fluorocomplex and acid. As a treatment method, a chromatographic column is filled with 75 mL of strong anion exchange resin, 75 mL of hydrofluoric acid (SV = 1 L / R-L) is flown at LV (linear velocity m / Hr) = 5, and then distilled water is used as developing water. 150 mL (SV = 2 L / RL) was passed through.
The flowed liquid was fractionated by 5 mL each, and the electrical conductivity at that time was measured. The fractionated samples were analyzed for hydrofluoric acid radicals, nitrate radicals, free acids, and titanium.

  FIG. 2 is a chromatograph of changes in electrical conductivity (EC) and free acid. FIG. 2 shows that the change in EC and the change in free acid concentration draw the same chromatograph, and the free acid concentration is estimated by EC.

  FIG. 3 shows changes in titanium concentration and free acid concentration. From FIG. 3, both titanium and free acid are chromatographically separated and have peaks. The fact that the fluoro complex of hydrofluoric acid was formed first separated the free acid and separated titanium with a delay, so that titanium and the free acid were separated.

  FIG. 4 shows the removal rate of various metals, the recovery rate of nitric acid, and the recovery rate of hydrofluoric acid when the metal salt solution and the recovered acid are separated by the value of electrical conductivity (EC). As shown in FIG. 4, the nitric acid recovery rate was 71.4%, the hydrofluoric acid recovery rate was 34.0%, and the free acid recovery rate was 87.0%.

Claims (3)

  In the case where a hydrofluoric acid solution containing titanium is passed through a strong anion exchange resin and free acid is recovered, titanium is adsorbed to the resin as a fluoro complex, and water is passed through the resin as a developing solution. And separating from the resin to recover titanium.   2. The separation and recovery method according to claim 1, wherein the flow of the acid solution and the switching of the developing water are performed by electric conductivity (EC).   2. The separation and recovery method according to claim 1, wherein the recovered acid and the metal solution are switched by electrical conductivity (EC).