Method of inhibiting extractant degradation by controlling extractive capacity and preventing direct degradation

Abstract

Provided is a method for inhibiting extractant degradation comprising preparing step, extracting step and scrubbing step, the method including: (a) the preparing step of a DSX solvent by adjusting the extractant concentration of the DSX solvent to a specific range; (b) the extracting step of metal included in the feed solution by adjusting the ratio of the organic (solvent) and an aqueous (solution) as a feed solution; (c) the scrubbing step of adjusting the zinc concentration of the solution using zinc sulfate; and (d) stripping step.

Claims

1. A method for inhibiting extractant degradation, the method including: (a) adjusting the concentration of extractant in a synergistic solvent extraction solvent; (b) mixing a feed solution and the synergistic solvent to extract metal from the feed solution into the synergistic solvent extraction solvent by adjusting the ratio of the synergistic solvent extraction solvent to the feed solution and separating the feed solution from which metal has been extracted and the synergistic solvent extraction solvent including extracted metal; (c) adding zinc sulfate to the feed solution from which metal has been extracted to adjust the concentration of zinc in the feed solution from which metal has been extracted; and (d) stripping extracted metal from the synergistic solvent extraction solvent.

2. The method of claim 1, wherein in step (b), soda ash is added to a sparger to adjust a pH of the feed solution from which metal has been extracted, and wherein in steps (c) and (d), sulfuric acid is added to a standpipe to adjust the sulfuric acid concentration of the feed solution from which metal has been extracted.

3. The method of claim 1, wherein the synergistic solvent extraction solvent includes an oxime-based extractant and a neodecanoic acid-based extractant in addition to kerosene, a diluent, and wherein the concentration of the oxime-based extractant is 0.5 v/v % to 6 v/v %.

4. The method of claim 3, wherein a volume ratio of the oxime-based extractant and the neodecanoic acid-based extractant is 1:0.5 to 4.

5. The method of claim 1, wherein in step (b), a volume ratio of the feed solution and the synergistic solvent extraction solvent is 1:0.5 to 3, and wherein a flow rate of the synergistic solvent extraction solvent is 550 m.sup.3/hr to 1800 m.sup.3/hr, and a flow rate of the feed solution is 550 m.sup.3/hr to 1500 m.sup.3/hr.

6. The method of claim 1, wherein in step (c), the concentration of zinc (Zn) is adjusted to 2 g/L to 20 g/L with zinc sulfate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart of a method for inhibiting the extractant degradation according to an embodiment of the present invention.

(2) FIG. 2 illustrates extractant degradation ratios with the concentrations of soda ash according to an embodiment of the present invention.

(3) FIG. 3 illustrates the corrosion on the electrode plate due to the solution entrainment in the scrubbing step.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(4) Hereinafter, embodiments of the present invention are described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

(5) FIG. 1 is a flow chart of a method for inhibiting the extractant degradation according to an embodiment of the present invention.

(6) Referring to FIG. 1, the method of inhibiting the extractant degradation according to the present invention may be divided into the preparing step, the extracting step and the scrubbing step.

(7) In particular, the method may include (a) the preparing step of a DSX solvent by adjusting the extractant concentration of the DSX solvent to a specific range; (b) the extracting step of metal included in the feed solution by adjusting the ratio of the organic (solvent) and an aqueous (solution) as a feed solution; (c) the scrubbing step of adjusting the zinc concentration of the solution using zinc sulfate; and (d) stripping step.

(8) In this regard, in step (a), soda ash may be added to a sparger to adjust the pH, and in steps (c) and (d), sulfuric acid may be added to a standpipe to adjust the sulfuric acid concentration.

(9) In step (a), the DSX solvent includes a kerosene-based compound which is a diluent, and the extractant includes an oxime-based extractant and a neodecanoic acid-based extractant.

(10) Further, the concentration of the oxime-based extractant is adjusted to 0.5 v/v % to 6 v/v %. A volume ratio of the oxime-based extractant and the neodecanoic acid-based extractant is 1:0.5 to 4.

(11) In step (b), when the feed solution containing the valuable metal is fed to the DSX organic (solvent), the DSX organic (solvent) and the feed solution are mixed to extract the valuable metal of the feed solution into the DSX solvent. As the feed of the DSX solvent is increased, the proportion of the mol total metal to be extracted to mol oxime of the DSX solvent can be kept low.

(12) Accordingly, in step (b), the volume ratio of the DSX aqueous (solution) and the organic (solvent) may be 1:0.5 to 3. The flow rate of DSX organic (solvent) may be 550 m.sup.3/hr to 1800 m.sup.3/hr, and the flow rate of the feed solution may be 550 m.sup.3/hr to 1500 m.sup.3/hr.

(13) In step (b), the extraction reaction of the valuable metal is performed according to the following reaction formula, and thus cobalt and zinc can be recovered.
CoSO.sub.4(aq)+R-H.sub.2(Org).fwdarw.R—Co(org)+H.sub.2SO.sub.4  [Reaction formula 1]
ZnSO.sub.4(aq)+R-H.sub.2(Org).fwdarw.R—Zn(org)+H.sub.2SO.sub.4  [Reaction formula 2]
MnSO.sub.4(aq)+R-H.sub.2(Org).fwdarw.R—Mn(org)+H.sub.2SO.sub.4  [Reaction formula 3]

(14) The solvent in which the metal is extracted by the above reaction is stored in a loaded organic tank.

(15) In the conventional scrubbing step, the zinc concentration is adjusted using the concentrated solution after stripping the extracted metal. When the concentration of manganese (Mn) or chlorine (Cl) in the scrubbing solution is high in the scrubbing step, a part of the scrubbing solution is bled off into the feed tank of the DSX process. When the concentrated solution is used, cobalt is also concentrated at a high concentration. Thus, when a portion thereof is bled off into the feed tank, it can overload the extractant capacity in the extracting step.

(16) For example, when the high concentration cobalt and zinc are fed to the scrubbing step, and a portion of the scrubbing solution is bled off into the feed tank for the impurity control, the amount of metal in the extractant is high due to the high metal content in the extracting step, thereby increasing the ratio of mol total metal to mol oxime to accelerate the extractant degradation.

(17) Therefore, in step (c), the zinc sulfate is diluted, and thus the zinc feed solution may be added. In order to control and add the zinc scrub feed solution to the scrubbing step, the zinc sulfate is diluted to have the concentration of zinc (Zn) to 2 g/L to 20 g/L, preferably 3 g/L to 15 g/L, and more preferably 4 g/L to 10 g/L.

(18) Further, step (d) is performed to prevent degradation of the extractant due to direct contact between the additive and the solvent when adding sulfuric acid and soda ash in the DSX process.

(19) The sulfuric acid may be added to adjust the concentration of sulfuric acid in the stripping and scrubbing steps. In order to prevent direct contact with the solvent during the addition of sulfuric acid, the sulfuric acid may be added into a standpipe and diluted with the solution, and then the mixture is contacted with the solvent rather than a conventional manner in which the sulfuric acid is directly added to the first agitator. This can prevent the sulfuric acid from directly contacting the solvent to inhibit the carbonization of the solvent.

(20) The soda ash can be added to control the pH in the extracting step. During the addition of soda ash, the soda ash may be added using a sparger rather than a conventional manner in which the soda ash is directly added in the first agitator in the extracting step. This can prevent the soda ash from directly contacting the solvent to inhibit the carbonization of the solvent and the local increase of the pH.

(21) FIG. 2 illustrates extractant degradation ratios with the concentrations of soda ash according to an embodiment of the present invention. It can be known that as the concentration of soda ash is low, the degradation of the extractant is slowly performed.

(22) As a result, the present invention can extend the lifetime of the extractant used in the DSX process by the above-described method for inhibiting the degradation of the extractant.