JP3993370B2 - Method for recovering Cr (V1) from anion exchange resin tower - Google Patents

Description

【００２６】
【発明の効果】
本発明を実施することにより、需要家で使用済みの陰イオン交換樹脂塔からＣｒ（VI）を高濃度でかつ不純物の少ない状態で回収することが可能になる。
【図面の簡単な説明】
【図１】本発明に係るＣｒ（VI）の高濃度回収法の説明図。
【符号の説明】
１〜３…第1〜第３の再生液タンク
1a，1b，2a，2b，3a，3b，4a，4b，5a〜5d，6a〜6d，7a〜7d，8a〜8d，9a，10a，11a，12a，13a，16a．．．バルブ
４…Ｃｒ（VI）濃厚液タンク、
５〜８…陰イオン交換樹脂塔、
９…苛性ソーダ溶液、
１０…エアー、
１１…水、
１２…回収液タンク、
１３，１４…ポンプ
１５．．．硫酸溶液
１６．．．排水
１７．．．再生スタンド[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for efficiently recovering Cr (VI) at a high concentration from an ion exchange resin adsorbed and saturated by adsorbing Cr (VI), SO ₄ ²⁻ , Cl ⁻ ions, and the like.
[0002]
[Prior art]
A method of removing only harmful Cr (VI) with an ion exchange column filled with an anion exchange resin as a treatment method using a portable ion exchange column containing hexavalent chromium-containing flush water generated in a chromate or chrome plating plant, Alternatively, there is a method in which all cations and anions (including anions other than Cr (VI)) are adsorbed and removed with a cation exchange resin and an anion exchange resin, and treated water is reused as pure water in the system.
[0003]
In both methods, it was necessary to carry out the regeneration work by transporting the ion-exchange tower adsorbed and saturated by the customer to the central regeneration station using a dedicated vehicle. As a regeneration method in the concentrated regeneration field, a method is generally adopted in which ion exchange columns filled with ion exchange resin adsorbed and saturated by a customer are arranged in parallel on a regeneration stand, and countercurrent multistage regeneration is performed. In addition, instead of a regenerated ion exchange tower, the consumer will be used continuously.
[0004]
It is the most desirable method from the viewpoint of environmental protection to effectively use the recovered Cr (VI) liquid as a raw material for producing chromium trioxide or chromium compound. However, in the case of the conventional countercurrent multistage regeneration method, as described above, the adsorption-saturated anion exchange resin used by the consumer adsorbs SO ₄ ²⁻ , Cl ^{2 −} ions, etc. in addition to Cr (VI). ing. For this reason, since these ions are also mixed into the recovered Cr (VI) solution, there is a problem that further purification treatment needs to be performed.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and the problem is that the impurities in the recovered Cr (VI) liquid can be easily reduced and can be used as a raw material for producing chromium salts. I will provide a.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the present invention provides an anion exchange resin tower in which at least Cr (VI), SO ₄ ²⁻ , and Cl ^{2 −} ions are adsorbed in a saturated manner, with a Cr ( VI ) concentration of 10 g / L to 100 g / L. After adjusting the Cr (VI) concentrate of pH 6.5 to 7.0, the solution was passed through to extrude SO ₄ ²⁻ and Cl ^{2 −} ions, and after this step, a countercurrent multistage regeneration method was performed. A step of recovering only Cr (VI) at a high concentration, wherein the extruding step is a part of a Cr (VI) high concentration liquid recovered by a countercurrent multistage regeneration method as a Cr (VI) concentrated liquid This is a method for recovering Cr (VI) that is passed through.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In the method of the present invention, before carrying out countercurrent multistage regeneration, a concentrated solution of Cr (VI) with a small amount of impurities is passed through an anion exchange resin tower adsorbed and saturated by a consumer, and adsorbed SO ₄ ²⁻ , Cl ^- after performing the extrusion such as ions, subsequently, it performs the counter-current multi-stage regeneration. The Cr (VI) concentrate to be used does not require the purchase of new chromic anhydride or the like by reusing the Cr (VI) liquid obtained by once performing countercurrent multistage regeneration. Further, countercurrent multistage regeneration leads to improvement of concentration efficiency and shortening of working time by performing simultaneous regeneration by arranging a plurality of ion exchange columns.
[0010]
It is not necessary to pass the same amount of the Cr (VI) concentrate to be passed through all the used anion exchange resin towers, and it is necessary to monitor them individually because the flow rate is different. The reason is that the degree of adsorption of Cr (VI) on the anion exchange resin varies depending on the type of liquid that is passed through by the customer, the liquid passing conditions, and the like. Since Cr (VI) ions are colored ions, when adsorbed, the color of the ion exchange resin becomes yellow or orange. Therefore, in the case of an ion exchange column saturated with a large amount of Cr (VI) ions adsorbed, When the amount of Cr (VI) to be liquid is small, conversely, when a small amount of Cr (VI) ions are adsorbed, a large amount of liquid is required. Therefore, it is desirable that at least two viewing windows are provided on the side surface of the ion exchange tower at the upper side and the lower side so that the colored state of the resin can be easily visually confirmed. It is also possible to automatically detect the necessary flow rate and stop the flow based on the detection signal.
[0011]
The higher the Cr (VI) concentration, the more effective is the extrusion of impurity anions such as SO ₄ ²⁻ and Cl ^{2 −} ions. The Cr (VI) concentration is preferably as high as possible at 10 g / L or more, but if too high, the ion exchange resin deteriorates. Further, since the ion exchange resin is an organic substance, the upper limit is preferably 100 g / L or less from the viewpoint of safety.
[0012]
Moreover, it is necessary to adjust the pH of the concentrated Cr (VI) solution to be adsorbed for adsorbing Cr (VI) to the acidic side. However, when the recovered liquid obtained is used as a raw material for chromic acids, it is preferably about 6.5 to 7.0 in order to reduce the Cl ⁻ and SO ₄ ²⁻ concentration in the recovered liquid as much as possible. As the acid for adjusting the pH, sulfuric acid or hydrochloric acid is desirable. In addition, when the Cr (VI) concentration of the concentrated Cr (VI) liquid is low, a method of concentrating it with a concentrator is also possible.
[0013]
In addition, when the suspended liquid is contained in the liquid Cr (VI) concentrated liquid, it is necessary to remove in advance with a filter such as a filter press.
[0014]
【Example】
The high concentration recovery method of Cr (VI) of the present invention will be described based on the embodiment shown in FIG. FIG. 1 shows the case of the countercurrent three-stage method, and the anion exchange resin tower is filled with a weakly basic anion exchange resin.
[0015]
(Extrusion process)
First, after bringing the anion exchange resin tower 5 adsorbed and saturated by a customer into a concentrated regeneration field, and performing water washing to remove impurities adhering to the resin (not shown in FIG. 1), It is arranged and connected to the reproduction stand 17. Similarly, the ion exchange towers 6 to 8 that have been used by other customers are arranged and connected to the regeneration stand 17 at predetermined positions.
[0016]
The Cr (VI) concentrated liquid tank 4 contains Cr (VI) concentrated liquid adjusted to pH 6.5 with the sulfuric acid solution 15, and this liquid is supplied to the valves 5 a, 5 b, 6 a, via the valve 4 a and the pump 14. 6b, 7a, 7b, 8a, 8b are simultaneously passed through four anion exchange resin towers 5-8 installed at predetermined positions, and the treated water is supplied with valves 5c, 5d, 6c, 6d, 7c, 7d. , 8c, 8d, and further flows into the waste water 16 through the valve 16a (hereinafter referred to as a chromium re-adsorption process. In addition, unless otherwise specified, the valve 5a for connecting the upper and lower parts of the ion exchange tower unless otherwise specified. -5d, 7a-7d, and 8a-8d are always open, and the others are open only when described.)
The standard for the end of the flow is to close the valves at the entrance of each ion exchange tower when the same color as the Cr (VI) concentrate is visually recognized in the treated water of each ion exchange tower, and all the liquid flow is completed. The time when The chromium re-adsorption process is thus completed, and the process proceeds to the next countercurrent multistage regeneration process.
[0017]
Here, if a large amount of Cr (VI) liquid is adsorbed on the anion exchange tower installed to perform the chromium re-adsorption step, the amount of liquid flowing from the Cr (VI) concentrated tank 4 can be reduced. (VI) The amount of liquid in the thick tank 4 does not decrease so much. On the contrary, if Cr (VI) is hardly adsorbed on the resin of the installed anion exchange tower, it is necessary to pass a large amount of liquid from the Cr (VI) rich tank 4 in the chromium re-adsorption step.
[0018]
(Countercurrent multistage regeneration process)
A fixed amount of the liquid in the first regenerative liquid tank 1 is installed at a predetermined position via a valve 1a, a pump 13, and a valve 13a via valves 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b. After simultaneously passing through the anion exchange resin towers 5 to 8 of the tower, the treated water passes through valves 5c, 5d, 6c, 6d, 7c, 7d, 8c and 8d, and further passes through valve 4b to form a Cr (VI) concentrate tank 4. Put in. In this case, the Cr (VI) concentrated liquid tank 4 is filled and replenished with the amount of liquid reduced in the chromium resorption process, so that Cr (VI) is added to the anion exchange tower installed to perform the chromium resorption process. The amount of liquid replenishment from the first regenerating liquid tank 1 differs depending on whether a large amount of liquid is adsorbed or only a small amount is adsorbed. Then, the remaining liquid in the first regeneration liquid tank 1 is installed at a predetermined position via the valve 1a, the pump 13, and the valve 13a via the valves 5a, 5b, 6a, 6b, 7a, 7b, 8a, and 8b. After simultaneously passing through the four anion exchange resin towers 5 to 8, the treated water passes through valves 5c, 5d, 6c, 6d, 7c, 7d, 8c, and 8d, and further enters the recovery liquid tank 12 through the valve 12a ( This will be used as a raw material for chromium salts). And the 1st reproduction | regeneration liquid tank 1 becomes substantially empty.
[0019]
Subsequently, the liquid in the second regenerated liquid tank 2 is exchanged through four valves through the valves 2a, 13 and 13a, through the valves 5a, 5b, 6a, 6b, 7a, 7b, 8a and 8b. After passing through the resin towers 5 to 8, the treated water passes through the valves 5 c, 5 d, 6 c, 6 d, 7 c, 7 d, 8 c, and 8 d and enters the empty first regenerated liquid tank 1 through the valve 1 b. At this time, the second regenerated liquid tank 2 is substantially emptied.
[0020]
Similarly, the liquid in the third regenerating liquid tank 3 passes through the valves 3a, the pump 13, and the valve 13a, and then passes through the valves 5a, 5b, 6a, 6b, 7a, 7b, 8a, and 8b, and the four towers of anions. After passing through the exchange resin towers 5 to 8, the treated water passes through the valves 5c, 5d, 6c, 6d, 7c, 7d, 8c, and 8d and enters the empty second regenerated liquid tank 2 through the valve 2b. . Again, the third regenerant tank 3 is substantially emptied.
[0021]
Then, the valve 10a of the air 10 is opened, and the residual liquid containing Cr (VI) in the four anion exchange resin towers 5 to 8 is passed through the valves 5a, 5b, 6a, 6b, 7a, 7b, 8a and 8b. Passes through the valves 5c, 5d, 6c, 6d, 7c, 7d, 8c and 8d and enters the empty third regenerated liquid tank 3 via the valve 3b.
[0022]
Further, the valve 11a of the water 11 is opened and adheres to the surface of the anion exchange resin in the four anion exchange resin towers 5 to 8 via the valves 5a, 5b, 6a, 6b, 7a, 7b, 8a and 8b. The Cr (VI) liquid thus obtained passes through the valves 5c, 5d, 6c, 6d, 7c, 7d, 8c, and 8d and enters the third regenerated liquid tank 3 via the valve 3b. Thereafter, a predetermined amount of caustic soda solution 9 is added to the third regenerating solution tank 3 through a valve 9a to adjust the concentration. The counter-current multistage regeneration process is completed by the work so far, and thereafter, for example, water washing is performed at the position, or valves 5b, 5c, 6b, 6c, 7b, 7c, 8b, and 8c at the upper and lower portions of the ion exchange tower are performed. Remove and remove the water in another place.
[0023]
As already described, whether the liquid in the first regeneration tank 1 is put into the Cr (VI) concentrated liquid tank 4 or recovered in the recovered liquid tank 12 or how the amount of liquid is adjusted, It depends on Cr (VI) adsorbed on the resin of the anion exchange tower and becomes case by case. In addition, the switching is performed by detecting how much of the Cr (VI) concentrate in the Cr (VI) concentrate tank 4 is used (how much liquid has passed through the ion exchange tower) by the detection means, Store this amount of liquid in the first regeneration tank 1 into the Cr (VI) concentrated liquid tank 4 by this amount, and then switch on and off the valve etc. to automatically resemble the recovered liquid tank 12. You may do it.
[0024]
For reference, an example of the composition and concentration of the recovered liquid tank 12 obtained by the method of the present invention is shown in Table 1 below together with the conventional method.
[0025]
[Table 1]

[0026]
【The invention's effect】
By carrying out the present invention, it is possible to recover Cr (VI) in a high concentration and low impurity state from an anion exchange resin tower that has been used by consumers.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a high concentration recovery method of Cr (VI) according to the present invention.
[Explanation of symbols]
1-3 ... 1st-3rd regeneration liquid tank
1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a-5d, 6a-6d, 7a-7d, 8a-8d, 9a, 10a, 11a, 12a, 13a, 16a. . . Valve 4 ... Cr (VI) concentrate tank,
5-8 ... anion exchange resin tower,
9 ... caustic soda solution,
10 ... Air,
11 ... water,
12 ... recovered liquid tank,
13, 14 ... pump 15. . . Sulfuric acid solution 16. . . Drainage 17. . . Playback stand

Claims (2)

At least Cr (VI), SO ₄ ²⁻ , and Cl ^{2 −} ions are saturated and adsorbed, and a Cr (VI) concentrated liquid having a Cr ( VI ) concentration of 10 g / L to 100 g / L is adjusted to pH 6.5. After adjusting to 7.0, the step of extruding SO ₄ ²⁻ and Cl ^{2 −} ions through the solution and the step of recovering only Cr (VI) at a high concentration by performing a countercurrent multistage regeneration method after this step The extrusion step is a method for recovering Cr (VI) in which a portion of the Cr (VI) high-concentration liquid recovered by the countercurrent multistage regeneration method as a Cr (VI) concentrated liquid is passed. The method for recovering Cr (VI) according to claim 1 , wherein the regeneration is performed by arranging a plurality of ion exchange columns in parallel and simultaneously regenerating them.

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