Rare earth wastewater treatment method

Abstract

The invention relates to the technical field of rare earth wastewater treatment, in particular to a rare earth wastewater treatment method which specifically comprises the following steps: (1) reacting rare earth feed liquid with an oxalic acid precipitator to generate oxalic acid rare earth precipitate and hydrochloric acid, and carrying out solid-liquid separation to obtain diluted hydrochloric acid; (2) treating the diluted hydrochloric acid with an alkaline extractant to remove iron / zinc / copper / nickel impurities in the hydrochloric acid so as to obtain pure diluted hydrochloric acid; and (3) in a corresponding rare earth extraction tank, diluted hydrochloric acid reacts with the loaded organic phase in a reverse extraction section, metal ions enter a water phase after exchange to obtain rare earth feed liquid, and the organic phase is combined with acid radical ions to realize regeneration.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth wastewater treatment, in particular to a rare earth wastewater treatment method. Background Art

[0002] Rare earths are an indispensable strategic resource for countries around the world to transform traditional industries, develop high-tech and cutting-edge national defense technologies. Rare earths are widely used in luminescent materials, magnetic materials, metallurgy, ceramics, electricity, communications, petrochemical fields and various functional materials.

[0003] Rare earth smelting wastewater is one of the main pollutants of rare earths, and a large amount of rare earth wastewater causes serious damage to the environment. Rare earth smelting wastewater mainly includes rare earth extraction wastewater and rare earth precipitation wastewater, of which rare earth precipitation wastewater accounts for more than 60%. Oxalic acid is one of the main precipitants for preparing high-purity rare earths. Rare earth liquid reacts with oxalic acid to produce oxalate rare earth precipitate and hydrochloric acid. Since oxalate rare earth precipitate is slightly soluble in hydrochloric acid, it is often necessary to add about 20%-100% excess oxalic acid to increase the rare earth yield, but at the same time, a large amount of acid-containing wastewater is also produced. Since the acid-containing wastewater contains excessive oxalic acid and other metal impurity ions, it cannot be used directly in the rare earth generation system. At present, it is mainly treated by lime neutralization method, which leads to the waste of excessive oxalate ions, hydrochloric acid and lime, and also produces a large amount of calcium oxalate neutralization slag, which brings a great burden to the environment.

[0004] Therefore, finding a rare earth wastewater treatment method that can reduce the amount of oxalic acid and hydrochloric acid used and reduce the discharge of acidic wastewater is an issue that needs to be urgently addressed. Summary of the invention

[0005] In order to solve the above technical problems existing in the prior art, the present invention provides a rare earth wastewater treatment method, which is specifically achieved through the following technical solutions.

[0006] A method for treating rare earth wastewater comprises the following steps:

[0007] (1) reacting a rare earth feed liquid with an oxalic acid precipitant to generate an oxalic acid rare earth precipitate and hydrochloric acid, and obtaining dilute hydrochloric acid after solid-liquid separation;

[0008] (2) treating the dilute hydrochloric acid with an alkaline extractant to remove iron / zinc / copper / nickel impurities in the hydrochloric acid to obtain pure dilute hydrochloric acid;

[0009] (3) In the corresponding rare earth extraction tank, dilute hydrochloric acid reacts with the loaded organic phase in the stripping section, and after the exchange, the metal ions enter the water phase to obtain the rare earth feed solution, and the organic phase combines with the acid radical ions to achieve regeneration.

[0010] Furthermore, the rare earth in step (1) and the rare earth in step (3) are the same element, so as to avoid cross contamination of high-purity rare earth elements.

[0011] Furthermore, in step (1), the rare earth liquid is excessive, and the obtained dilute hydrochloric acid contains excessive rare earth elements. While reducing the consumption of oxalic acid, the rare earth elements can be recycled to achieve a high yield.

[0012] Furthermore, the oxalic acid used in step (1) is solid. Adding oxalic acid in a solid state can reduce the precipitation volume, thereby increasing the oxalic acid concentration and utilization efficiency.

[0013] Furthermore, the alkaline extractant in step 2) does not react with rare earth ions.

[0014] Furthermore, the alkaline extractant in step (2) is N235 and its diluent.

[0015] Furthermore, the diluent is isooctyl alcohol and kerosene.

[0016] While avoiding the enrichment of harmful metal ions that affect the quality of rare earth products, the yield of rare earth elements is not reduced.

[0017] Furthermore, in the corresponding rare earth extraction tank, after the dilute hydrochloric acid reacts with the loaded organic phase in the stripping section, the process also includes hydrochloric acid stripping and pure water washing, so as to avoid incomplete stripping of rare earth ions.

[0018] Furthermore, the rare earth is from the lanthanide series.

[0019] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0020] (1) The method of the present invention avoids cross contamination of high-purity rare earth elements.

[0021] (2) The method of the present invention reduces the consumption of oxalic acid and can achieve a high yield of rare earth elements through recycling.

[0022] (3) The method of the present invention adds oxalic acid in a solid state, which can reduce the precipitation volume and improve the oxalic acid concentration and utilization efficiency.

[0023] (4) The method of the present invention avoids the influence of harmful metal ion enrichment on the quality of rare earth products while not reducing the yield of rare earth elements.

[0024] (5) The method of the present invention can avoid incomplete stripping of rare earth ions.

[0025] (6) The method of the present invention is a rare earth wastewater treatment method that can reduce the amount of oxalic acid and hydrochloric acid used and reduce the discharge of acidic wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the existing method.

[0027] Figure 2 It is a flow chart of the new method of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0029] 1-1.6 mol / L rare earth chloride feed liquid and oxalic acid or oxalic acid solution are reacted in a reactor at a molar ratio of 1:1.35-1.45, and after vacuum filtration, rare earth oxalate precipitate and 2-4 mol / L rare earth ion-containing dilute hydrochloric acid are obtained; the dilute hydrochloric acid is treated in an N235-isooctanol-kerosene (volume ratio 20:20:60) extraction tank to remove iron / zinc / copper / nickel impurities (phase ratio 2-4:1) to obtain 2-4 mol / L pure rare earth ion-containing dilute hydrochloric acid; in the same rare earth extraction tank, the rare earth ion-containing dilute hydrochloric acid is exchanged with the loaded organic phase in the stripping section to obtain the corresponding rare earth chloride solution in the aqueous phase, and the loaded organic phase is regenerated by combining with hydrogen; subsequently, the organic phase is further stripped with pure hydrochloric acid and washed with pure water to obtain a blank organic phase without rare earth.

[0030] The specific reaction conditions of each embodiment are as follows:

[0031] Example 1 Ho / Er separation and extraction tank

[0032]

[0033] Example 2 LCPN separation and extraction tank

[0034]

[0035] Example 3 Pure Eu Separation and Extraction Tank

[0036]

[0037] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A method for treating rare earth wastewater, characterized in that: The following steps are involved: (1) reacting a rare earth feed liquid with an oxalic acid precipitant to generate an oxalic acid rare earth precipitate and hydrochloric acid, and obtaining dilute hydrochloric acid after solid-liquid separation; (2) treating the dilute hydrochloric acid with an alkaline extractant to remove iron / zinc / copper / nickel impurities in the hydrochloric acid to obtain pure dilute hydrochloric acid; (3) In the corresponding rare earth extraction tank, dilute hydrochloric acid reacts with the loaded organic phase in the stripping section. After the exchange, the metal ions enter the water phase to obtain the rare earth feed solution, and the organic phase combines with the acid radical ions to achieve regeneration.

2. The method for treating rare earth wastewater according to claim 1, characterized in that: The rare earth in step (1) and the rare earth in step (3) are the same element.

3. The method for treating rare earth wastewater according to claim 1, characterized in that: In the step (1), the rare earth liquid is excessive, and the obtained dilute hydrochloric acid contains excessive rare earth elements.

4. The method for treating rare earth wastewater according to claim 1, characterized in that: The oxalic acid used in the step (1) is solid.

5. The method for treating rare earth wastewater according to claim 1, characterized in that: The alkaline extractant in step (2) does not react with rare earth ions.

6. The method for treating rare earth wastewater according to claim 1, characterized in that: The alkaline extractant in the step (2) is N235 and its diluent.

7. The method for treating rare earth wastewater according to claim 6, characterized in that: The diluents are isooctyl alcohol and kerosene.

8. The method for treating rare earth wastewater according to claim 1, characterized in that: In the corresponding rare earth extraction tank, after the dilute hydrochloric acid reacts with the loaded organic phase in the stripping section, it also includes hydrochloric acid stripping and pure water washing.

9. The method for treating rare earth wastewater according to claim 1, characterized in that: The rare earth is a lanthanide.

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