System and method for enriching and recovering rare earth elements from acid mine drainage

Abstract

The application provides a system and method for enriching and recovering rare earth elements in acid mine wastewater, and belongs to the technical field of rare earth element recovery. The system for enriching and recovering rare earth elements in acid mine wastewater comprises an adjusting pool, a sludge washer, a neutralizer, a buffer pool, a first reactor, a second reactor, a filter, a first dewatering pool, a second dewatering pool, an acid pickling soaking pool and a sludge dewatering pool. The system is used for recovering rare earth elements, the pH value of the acid mine wastewater is increased by adding an alkaline substance, the reagent cost for recovering the rare earth elements is significantly reduced, the dewatered sludge is pickled, the rare earth elements adhered to the dewatered sludge are transferred to the leaching solution through the pickling, the leaching solution is returned to the buffer pool again, the loss of the rare earth elements is further reduced, and the recovery rate of the rare earth elements is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth element recovery, and particularly relates to a system for enriching and recovering rare earth elements in acid mine drainage and a method thereof. BACKGROUND

[0002] Rare earth is a strategic resource with important role, with the wide application of rare earth in aerospace, national defense, new energy, information technology, transportation, medical treatment and other high-tech fields, the demand for rare earth is continuously increasing. However, as a non-renewable scarce resource, based on the change of global resource reserves, supply pattern and the worry of market supply, people seek unconventional alternative products. Acid mine drainage is one of the important reasons for causing mine environmental pollution, acid mine drainage (AMD) contains a large amount of heavy metals such as Fe, Al, Mn and other pollutants, and also contains a large amount of dissolved rare earth elements (REEs).

[0003] In recent years, a large amount of research work has been carried out on the extraction and recovery of REEs in AMD, which has confirmed the feasibility of recovering rare earth resources from AMD. The commonly used methods for recovering REEs from AMD include precipitation method, solvent extraction method, ion exchange method and membrane filtration method. However, most of the methods for recovering REEs from acid mine drainage have the characteristics of complex process, low efficiency, high energy consumption and even secondary pollution. Therefore, it is of great significance to study a system and method for enriching and recovering rare earth elements in acid mine drainage. SUMMARY

[0004] The present application relates to the technical field of rare earth element recovery, and particularly relates to a system for enriching and recovering rare earth elements in acid mine drainage and a method thereof.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a system and method for enriching and recovering rare earth elements in acid mine drainage, the system for enriching and recovering rare earth elements in acid mine drainage comprises a regulating tank, a sludge washer, a neutralizer, a buffer tank, a first reactor, a second reactor, a filter, a first dewatering tank, a second dewatering tank, an acid pickling soaking tank and a sludge dewatering tank.

[0007] The present application also provides a method for enriching and recovering rare earth elements in acid mine drainage by using the above-mentioned system, which comprises the following steps:

[0008] (1) The acid mine drainage sequentially enters the regulating tank and the sludge washer to obtain sludge washer effluent and washing sludge;

[0009] (2) the sludge scrubber effluent and the alkaline substance are reacted in a neutralizer to obtain backflow sludge and neutralizer effluent;

[0010] The washed sludge is dewatered in a dewatering pool to obtain filtrate and dewatered sludge;

[0011] The backflow sludge and the filtrate in step (2) are returned to the conditioning pool in step (1) to mix with the acid mine wastewater, and the mixture is introduced into the sludge scrubber to perform a neutralization reaction to obtain sludge scrubber effluent and washed sludge;

[0012] (3) the neutralizer effluent is introduced into a first reactor through a buffer pool, and a sodium hydroxide solution is added to perform a reaction to obtain first reactor effluent and first reactor sludge;

[0013] (4) the first reactor effluent and the sodium hydroxide solution are reacted in a second reactor, and the reaction product is filtered in a filter to obtain crude rare earth and filter water.

[0014] Preferably, in step (2), the alkaline substance comprises one or more of sodium carbonate, sodium hydroxide, CaCO3-rich limestone and MgCa(CO3)2-rich dolomite.

[0015] Preferably, in step (2), the pH value of the neutralizer effluent is 3.5-4.2.

[0016] Preferably, in step (3), the concentration of the sodium hydroxide solution is 4-6 mol / L; and the pH value of the first reactor effluent is 4.4-5.0.

[0017] Preferably, in step (3), the first reactor sludge is dewatered in a dewatering pool two to obtain filtrate and dewatered sludge, and the filtrate is returned to the buffer pool.

[0018] Preferably, the dewatered sludge in the dewatering pool two, the dewatered sludge in the dewatering pool one and the acid solution are washed in an acid pickling immersion pool to obtain leaching solution and washed sludge.

[0019] Preferably, the leaching solution is introduced into the buffer pool; and the washed sludge is introduced into a sludge dewatering pool.

[0020] Preferably, the pH value of the leaching solution is 4.5-5.1.

[0021] Preferably, in step (4), the concentration of the sodium hydroxide solution is 4-6 mol / L; and the pH value of the filter water is 9-10.

[0022] The present application has the following beneficial effects:

[0023] (1) the present application adds alkaline substances to neutralize the acid mine wastewater, improves the pH value of the acid mine wastewater, the alkaline substances include sodium carbonate, sodium hydroxide, limestone rich in CaCO3 and dolomite rich in MgCa(CO3)2, the cost of the alkaline substances is low, and the cost of the reagent for recovering rare earth elements can be significantly reduced.

[0024] (2) the present application carries out pickling on the dewatered sludge in the first dewatering pool and the dewatered sludge in the second dewatering pool, the rare earth elements attached to the dewatered sludge are transferred to the leaching solution through pickling, the leaching solution returns to the buffer pool, and the leaching solution and the neutralizer effluent enter the first reactor, so that the loss of rare earth elements is reduced, and the recovery rate of rare earth elements is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The present application provides a system for enriching and recovering rare earth elements in acid mine wastewater and a process flow diagram thereof, Figure 1 The raw water in the present application is acid mine wastewater. DETAILED DESCRIPTION

[0026] The present application provides a system for enriching and recovering rare earth elements in acid mine wastewater and a method thereof, the system for enriching and recovering rare earth elements in acid mine wastewater comprises a conditioning pool, a sludge washer, a neutralizer, a buffer pool, a first reactor, a second reactor, a filter, a first dewatering pool, a second dewatering pool, an acid pickling soaking pool and a sludge dewatering pool.

[0027] The present application also provides a method for enriching and recovering rare earth elements in acid mine wastewater by using the above-mentioned system, comprising the following steps:

[0028] (1) the acid mine wastewater sequentially enters the conditioning pool and the sludge washer to obtain sludge washer effluent and washing sludge;

[0029] (2) the sludge washer effluent and the alkaline substance are reacted in the neutralizer to obtain backflow sludge and neutralizer effluent;

[0030] The washing sludge is dewatered in the first dewatering pool to obtain filtrate and dewatered sludge;

[0031] The backflow sludge and the filtrate in step (2) return to the conditioning pool in step (1) and mix with the acid mine wastewater, and the mixture enters the sludge washer for neutralization reaction to obtain sludge washer effluent and washing sludge;

[0032] (3) the neutralizer effluent passes through the buffer pool and enters the first reactor, sodium hydroxide solution is added for reaction to obtain first reactor effluent and first reactor sludge;

[0033] (4) The first reactor effluent and sodium hydroxide solution are reacted in the second reactor, and the reaction product is filtered in a filter to obtain crude rare earth and filter water.

[0034] In the present application, in step (2), the basic substance comprises one or more of sodium carbonate, sodium hydroxide, CaCO3-rich limestone and MgCa(CO3)2-rich dolomite, preferably one or more of sodium carbonate, CaCO3-rich limestone and MgCa(CO3)2-rich dolomite, and further preferably CaCO3-rich limestone and / or MgCa(CO3)2-rich dolomite.

[0035] In the present application, in step (2), the pH value of the neutralizer effluent is 3.5-4.2, preferably 3.6-4.1, and further preferably 3.7-4.0.

[0036] In the present application, the reflux sludge is formed after the sludge washer effluent in the neutralizer and the basic substance are reacted, and the reflux sludge contains unreacted basic substance. The reflux sludge discharged from the neutralizer and the acid mine wastewater enter the conditioning tank and then the sludge washer, and the acid in the acid mine wastewater is used to neutralize the basic substance in the reflux sludge, so as to reduce the consumption of the acid solution in the acid leaching tank.

[0037] In the present application, the purpose of adding the basic substance in the neutralizer is to remove Fe 3+ from the sludge washer effluent. The reflux sludge generated by the neutralizer contains a large amount of Fe(OH)3, unreacted CaCO3, CaSO4 crystals formed by supersaturation and part of rare earth carried by coprecipitation.

[0038] In the present application, in step (2), the filtrate is formed after the reflux sludge generated by the sludge washer and the acid mine wastewater are subjected to neutralization reaction, and the washing sludge contains a high water content. The washing sludge is discharged into the dewatering tank to be concentrated and dewatered by gravity to form the filtrate and dewatered sludge.

[0039] In the present application, in step (3), the concentration of the sodium hydroxide solution is 4-6 mol / L, and preferably 5 mol / L; and the pH value of the first reactor effluent is 4.4-5.0, and preferably 4.5-4.9.

[0040] In the present application, in step (3), the sludge in the first reactor is dewatered in the second dewatering tank to obtain the filtrate and dewatered sludge, and the filtrate is returned to the buffer tank.

[0041] In the present application, the dewatered sludge in the second dewatering tank, the dewatered sludge in the first dewatering tank and the acid solution are washed in the acid leaching tank to obtain the leaching solution and the washed sludge.

[0042] In the present application, the leaching solution enters a buffer pool; the washed sludge enters a sludge dewatering pool.

[0043] In the present application, the pH value of the leaching solution is 4.5-5.1.

[0044] In the present application, the number of times of washing by adding acid solution is 2-7, preferably 3-6, and further preferably 4-5.

[0045] In the present application, the washed sludge preferably enters a sludge dewatering pool for drying and dewatering, and the obtained filtrate preferably enters a return adjustment pool to be mixed with acid mine wastewater.

[0046] In the present application, in the step (4), the concentration of the sodium hydroxide solution is 4-6 mol / L, preferably 5 mol / L; and the pH value of the filtered water is 9-10, preferably 9.2-9.8, and further preferably 9.3-9.7.

[0047] In the present application, the effluent from the sludge washer and the alkaline substance are reacted in a neutralizer, the mixture enters the sludge washer for neutralization reaction, the sodium hydroxide solution is added to the first reactor for reaction, and the sodium hydroxide is added to the second reactor for reaction. The present application does not limit the reaction time and the reaction temperature for all the above reactions, as long as the pH values of the effluent from the neutralizer, the effluent from the first reactor and the effluent from the second reactor are controlled. In the present application, the above reactions are all carried out at room temperature, preferably at 20-30°C, and further preferably at 22-28°C.

[0048] The technical solutions provided by the present application will be described in detail below in combination with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0049] Example 1

[0050] The pH value of the acid mine wastewater is 2.34, the concentration of REEs is 31.7 mg / L, and the concentration of Fe is 923 mg / L.

[0051] Method for enriching and recovering rare earth elements in acid mine wastewater:

[0052] Firstly, the acid mine drainage enters the adjusting tank and the sludge washer in sequence to obtain the sludge washer effluent and the washing sludge. The sludge washer effluent enters the neutralizer, and the limestone rich in CaCO3 is added to react at 25°C to obtain the reflux sludge and the neutralizer effluent (pH value is 3.68). The washing sludge is dewatered in the dewatering tank 1 to obtain the filtrate and the dewatering sludge. The reflux sludge and the filtrate return to the adjusting tank to mix with the acid mine drainage, and then enter the sludge washer to carry out the neutralization reaction at 25°C. The neutralizer effluent enters the buffer tank and then enters the first reactor, and the 5 mol / L sodium hydroxide solution is added to react at 25°C to obtain the first reactor effluent (pH value is 4.5) and the first reactor sludge. The first reactor sludge is dewatered in the dewatering tank 2 to obtain the filtrate and the dewatering sludge, and the filtrate returns to the buffer tank. The first reactor effluent enters the second reactor, and the 5 mol / L sodium hydroxide solution is added to react at 25°C. The reaction product enters the filter to obtain the crude rare earth and the filter water (pH value is 9.3). The dewatering sludge produced by the dewatering tank 1 and the dewatering tank 2 enters the pickling soaking tank, and the hydrochloric acid solution is added to react with the dewatering sludge to obtain the leaching solution (pH value is 4.74) and the washed sludge. The leaching solution returns to the buffer tank to mix with the neutralizer effluent, and then enters the first reactor. The washed sludge is dried and dewatered, and then the limestone rich in CaCO3 is added to the dried and dewatered sludge for external transportation.

[0053] The pH values, the rare earth contents and the Fe contents of the adjusting tank effluent, the neutralizer effluent, the first reactor effluent, the second reactor effluent, the filter water and the leaching solution in Example 1 are shown in Table 1.

[0054] Example 2

[0055] The pH value of the acid mine drainage is 2.30, the concentration of REEs is 31.37 mg / L, and the concentration of Fe is 795 mg / L.

[0056] The method for enriching and recovering the rare earth elements in the acid mine drainage comprises the following steps:

[0057] First, the acidic mining wastewater sequentially enters the equalization tank and sludge scrubber, yielding effluent and washed sludge from the sludge scrubber. The effluent then enters the neutralizer, where limestone rich in MgCa(CO3)2 is added and reacted at 25°C, producing return sludge and neutralizer effluent (pH 3.8). The washed sludge is dewatered in dewatering tank 1, yielding filtrate and dewatered sludge. The return sludge and filtrate are returned to the equalization tank and mixed with the acidic mining wastewater, then re-enter the sludge scrubber for neutralization at 25°C. The neutralizer effluent then enters the primary reactor via a buffer tank, where a 5 mol / L sodium hydroxide solution is added and reacted at 25°C, yielding primary reactor effluent (pH 3.8). The wastewater consists of a pH value of 4.49 and sludge from the primary reactor. The primary reactor sludge is dewatered in dewatering tank two, yielding filtrate and dewatered sludge. The filtrate is returned to the buffer tank. The dewatered sludge from dewatering tanks one and two enters an acid washing and soaking tank, where hydrochloric acid solution is added to react with the dewatered sludge, yielding leachate (pH 4.53) and washed sludge. The leachate is returned to the buffer tank and mixed with the effluent from the neutralizer before entering the primary reactor. The effluent from the primary reactor enters the secondary reactor, where 5 mol / L sodium hydroxide solution is added, and the reaction is carried out at 25°C. The reaction products are filtered to obtain coarse rare earth elements and filtered water (pH 9.15). The washed sludge from the acid washing and soaking tank is dried and dewatered. Finally, limestone rich in MgCa(CO3)2 is added to the dried and dewatered sludge for transport.

[0058] The pH value, rare earth content, and Fe content of the effluent from the equalization tank, neutralizer, primary reactor, secondary reactor, filtered water, and leachate in Example 2 are shown in Table 1.

[0059] Example 3

[0060] The acidic mine wastewater had a pH of 2.31, a REE concentration of 30.16 mg / L, and a Fe concentration of 817 mg / L.

[0061] Methods for enriching and recovering rare earth elements from acidic mining wastewater:

[0062] First, the acidic mining wastewater sequentially enters the equalization tank and sludge scrubber, yielding effluent and washed sludge from the sludge scrubber. The effluent then enters the neutralizer, where dolomite rich in MgCa(CO3)2 is added and reacted at 25°C, resulting in reflux sludge and neutralizer effluent (pH 3.98). The washed sludge is dewatered in the dewatering tank, yielding filtrate and dewatered sludge. The reflux sludge and filtrate are returned to the equalization tank and mixed with the acidic mining wastewater, then re-enter the sludge scrubber for neutralization at 25°C. The neutralizer effluent then enters the primary reactor via a buffer tank, where a 5 mol / L sodium hydroxide solution is added and reacted at 25°C, yielding primary reactor effluent (pH 3.98). The process involves two stages: dewatering tank (pH 4.51) and dewatering sludge from the primary reactor. The primary reactor sludge is dewatered in dewatering tank two, yielding filtrate and dewatered sludge. The filtrate is returned to the buffer tank. The dewatered sludge from both dewatering tanks enters an acid washing and soaking tank, where hydrochloric acid solution is added to react with the sludge, producing leachate (pH 4.58) and washed sludge. The leachate is returned to the buffer tank and mixed with the neutralizer effluent before entering the primary reactor. The effluent from the primary reactor enters a secondary reactor, where 5 mol / L sodium hydroxide solution is added, and the reaction is carried out at 25°C. The reaction products are filtered to obtain coarse rare earth elements and filtered water (pH 9.03). The washed sludge from the acid washing and soaking tank is dried and dewatered. Finally, dolomite rich in MgCa(CO3)2 is added to the dried and dewatered sludge for transport.

[0063] The pH value, rare earth content, and Fe content of the effluent from the equalization tank, neutralizer, primary reactor, secondary reactor, filtered water, and leachate in Example 3 are shown in Table 1.

[0064] Example 4

[0065] The acidic mine wastewater has a pH of 2.27, a REE concentration of 30.02 mg / L, and a Fe concentration of 806 mg / L.

[0066] Methods for enriching and recovering rare earth elements from acidic mining wastewater:

[0067] First, the acidic mining wastewater sequentially enters the equalization tank and sludge scrubber, yielding sludge scrubber effluent and washed sludge. The sludge scrubber effluent then enters the neutralizer, where limestone rich in CaCO3 is added and reacted at 25°C, producing return sludge and neutralizer effluent (pH 4.14). The washed sludge is dewatered in dewatering tank 1, yielding filtrate and dewatered sludge. The return sludge and filtrate are returned to the equalization tank and mixed with the acidic mining wastewater, then re-enter the sludge scrubber for neutralization at 25°C. The neutralizer effluent then enters the primary reactor via a buffer tank, where a 5 mol / L sodium hydroxide solution is added and reacted at 25°C, yielding primary reactor effluent (pH 4.14). 4.95) and the sludge from the primary reactor. The sludge from the primary reactor is dewatered in dewatering tank two, yielding filtrate and dewatered sludge. The filtrate is returned to the buffer tank. The dewatered sludge from dewatering tanks one and two enters the acid washing and soaking tank, where hydrochloric acid solution is added to react with the dewatered sludge, yielding leachate (pH 5.02) and washed sludge. The leachate is returned to the buffer tank and mixed with the effluent from the neutralizer before entering the primary reactor. The effluent from the primary reactor enters the secondary reactor, where 5 mol / L sodium hydroxide solution is added, and the reaction is carried out at 25°C. The reaction products are filtered to obtain coarse rare earth elements and filtered water (pH 9.59). The washed sludge from the acid washing and soaking tank is dried and dewatered. Finally, limestone rich in CaCO3 is added to the dried and dewatered sludge for transport.

[0068] The pH value, rare earth content, and Fe content of the effluent from the equalization tank, neutralizer, primary reactor, secondary reactor, filtered water, and leachate in Example 4 are shown in Table 1.

[0069] Table 1 shows the pH value, rare earth content, and Fe content at each stage in Examples 1-4.

[0070]

[0071] As can be seen from Table 1, the system and method for enriching and recovering rare earth elements in acidic mine wastewater provided by the present invention can remove iron from acidic mine wastewater and enrich rare earth elements in coarse rare earth. The content of rare earth elements in the filtered water is much lower than that in acidic mine wastewater.

[0072] As can be seen from the above embodiments, the present invention provides a system and method for enriching and recovering rare earth elements from acidic mining wastewater. The system for enriching and recovering rare earth elements from acidic mining wastewater includes an equalization tank, a sludge scrubber, a neutralizer, a buffer tank, a primary reactor, a secondary reactor, a filter, a first dewatering tank, a second dewatering tank, an acid washing and soaking tank, and a sludge dewatering tank. By using the above system to recover rare earth elements, the pH value of the acidic mining wastewater is increased by adding alkaline substances, which can significantly reduce the reagent cost for rare earth element recovery. Acid washing of the dewatered sludge transfers the rare earth elements attached to the dewatered sludge to the leachate, which is then returned to the buffer tank, further reducing the loss of rare earth elements in the crude rare earth and improving the recovery rate of rare earth elements.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for enriching and recovering rare earth elements from acidic mine wastewater, characterized in that, The system for enriching and recovering rare earth elements in acid mine drainage water comprises a regulating tank, a sludge washer, a neutralizer, a buffer tank, a first reactor, a second reactor, a filter, a first dewatering tank, a second dewatering tank, an acid leaching tank, and a sludge dewatering tank. The method for enriching and recovering rare earth elements in acid mine drainage water comprises the following steps: (1) The acid mine drainage water sequentially enters the regulating tank and the sludge washer to obtain sludge washer effluent and washed sludge; (2) The sludge washer effluent and an alkaline substance are reacted in the neutralizer to obtain backflow sludge and neutralizer effluent; The washed sludge is dewatered in the first dewatering tank to obtain filtrate and dewatered sludge; The backflow sludge and the filtrate in step (2) are returned to the regulating tank in step (1) and mixed with the acid mine drainage water, and the mixture enters the sludge washer to perform a neutralization reaction to obtain sludge washer effluent and washed sludge; (3) The neutralizer effluent passes through the buffer tank and enters the first reactor, and sodium hydroxide solution is added to perform a reaction to obtain first reactor effluent and first reactor sludge; (4) The first reactor effluent and sodium hydroxide solution are reacted in the second reactor, and the reaction product is filtered in the filter to obtain crude rare earth and filtered water; In step (3), the first reactor sludge is dewatered in the second dewatering tank to obtain filtrate and dewatered sludge, and the filtrate is returned to the buffer tank; The dewatered sludge of the second dewatering tank, the dewatered sludge of the first dewatering tank, and an acid solution are washed in the acid leaching tank to obtain a leaching solution and washed sludge.

2. The method of claim 1, wherein, In step (2), the alkaline substance comprises one or more of sodium carbonate, sodium hydroxide, limestone rich in CaCO3, and dolomite rich in MgCa(CO3)2.

3. The method according to claim 1 or 2, characterized in that, In step (2), the pH value of the neutralizer effluent is 3.5-4.

2.

4. The method of claim 3, wherein, In step (3), the concentration of the sodium hydroxide solution is 4-6 mol / L, and the pH value of the first reactor effluent is 4.4-5.

0.

5. The method of claim 1, wherein, The leaching solution enters the buffer tank, and the washed sludge enters the sludge dewatering tank.

6. The method of claim 5, wherein, The pH value of the leaching solution is 4.5-5.

1.

7. The method according to claim 1 or 2 or 4, characterized in that, In step (4), the concentration of the sodium hydroxide solution is 4-6 mol / L, and the pH value of the filtered water is 9-10.

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