Treatment method of rare earth ore concentrate chemical separation wastewater

Abstract

The invention discloses a rare earth concentrate chemical separation wastewater treatment method, which comprises: 1) adding an alkaline agent I and a precipitate I into rare earth concentrate chemical separation wastewater, and carrying out a reaction to obtain lead slag and a lead-removed supernatant; (2) adding a calcium agent, an alkaline agent II and a flocculating agent into the lead-removed supernatant to react, so as to obtain fluorine residues and fluorine-removed supernatant; (3) electrolyzing the fluorine-removed supernate to obtain iron slag and iron-removed supernate; 4) adding phosphate and a precipitant II into the iron-removed supernate for reaction to obtain phosphate precipitate of rare earth elements and rare earth-removed supernate; 5) carrying out evaporation concentration on the rare earth-removed supernatant to obtain an evaporation concentrated solution; and cooling the evaporated concentrated solution, and carrying out solid-liquid separation to obtain a CaCl2. 2H2O crystal and a mother solution. The lead element, the fluorine element, the iron element, the rare earth element and the calcium element in the rare earth ore concentrate chemical separation wastewater can be directionally separated and recycled step by step, and cross interference among the elements is avoided.

Description

Technical Field

[0001] The invention relates to a method for treating rare earth concentrate beneficiation wastewater. Background Art

[0002] During atmospheric-pressure concentrated alkaline decomposition of the Bayan Obo mixed rare earth concentrate, chemical beneficiation and decalcification are typically used to remove impurities such as calcium and iron, thereby minimizing rare earth losses. This process uses hydrochloric acid and sodium sulfate to pretreat the rare earth concentrate at a low boiling temperature for 4-6 hours, generating a significant amount of chemical beneficiation wastewater. This wastewater is primarily composed of calcium chloride, but also contains impurities such as rare earths, iron, lead, fluorine, and phosphorus, resulting in high-salt and high-calcium content. In this technical field, the wastewater is typically neutralized and partially recovered before being discharged.

[0003] The main treatment methods for chemical separation wastewater include chemical treatment and ion exchange. While ion exchange effectively separates calcium ions, the resin regeneration process requires the use of regeneration agents, which can lead to secondary pollution. Therefore, chemical treatment is more commonly used for treating chemical separation wastewater than ion exchange. Chemical treatment involves the stepwise addition of chemical agents to the wastewater, converting impurity ions into insoluble salts that are then precipitated or flocculated for removal.

[0004] CN105668888A discloses a method for the comprehensive recovery of low-grade rare earth concentrate and wastewater resources. The method comprises: (1) mixing low-grade mixed rare earth concentrate, hydrochloric acid solution and enhanced impurity remover in proportion, stirring and dissolving under heating conditions of 90-100°C, and after the dissolution is completed, filtering to obtain a concentrate and wastewater with a REO mass percentage of 62%≤≤70% and a Ca mass percentage of 0.5%≤2.5%. (2) adding an excess of sulfuric acid solution to the wastewater to remove calcium ions, and the molar concentration of hydrogen ions in the mixed solution after the addition of sulfuric acid is ≥2.5 mol / L to produce a calcium sulfate dihydrate byproduct, and the mass volume concentration of CaO in the wastewater after calcium removal is ≤5 g / L. (3) The decalcified chemical separation wastewater is reused in step (1) to circulate and treat a new batch of low-grade mixed rare earth concentrate, and the number of cycles is limited to the mass percentage of CaO in the last decalcified concentrate ≤ 2.5%. According to the actual low-grade mixed rare earth concentrate, the number of cycles is ≤ 6 times. (4) After the circular chemical separation wastewater is decalcified, the relative concentrations of phosphorus, iron and rare earth are adjusted with iron salts so that the ratio of the sum of the molar concentrations of rare earth and iron to the molar concentration of phosphorus is 1.0-1.5:1.0; ammonia water or liquid ammonia is used to adjust the pH value to 1.0-1.5, and RE, P and Fe are preferentially co-precipitated. The co-precipitate is combined with the chemical separation concentrate for mineral decomposition, and the three valuable resources of RE, P and Fe are comprehensively recovered; after removing RE, P and Fe, the solution is further adjusted to a pH value of 3.5-4.5 with ammonia water or liquid ammonia, so that the remaining F and Ca in the solution are co-precipitated to form a crude fluorite product; the neutralized wastewater is evaporated and concentrated to form ammonium chloride crystals and distilled water. This method offers significant advantages in terms of comprehensive resource recovery and reduced acid and alkali consumption, but it fails to consider the recovery of heavy metal lead, causing lead ions to migrate throughout the wastewater treatment process, posing a risk of heavy metal contamination. Furthermore, this method converts calcium into calcium sulfate dihydrate and calcium fluoride, which have low economic value.

[0005] CN111018184A discloses a process for treating rare earth wastewater. This method involves acidifying the rare earth wastewater, adding an ammonia nitrogen remover and sodium hypochlorite for catalytic oxidation, then adding calcium oxide to control the pH to approximately 9. The reaction time is 90 to 120 minutes. This method effectively removes COD, ammonia nitrogen, and heavy metal ions from the wastewater generated during the rare earth extraction process, achieving a high ammonia nitrogen reduction rate. However, the ammonia nitrogen remover used in this method is composed of aluminum sulfate, polyvinyl alcohol (PVA1), ferrous sulfate, chlorinated powder, sodium sulfate, polyepoxysuccinic acid, long-flame coal activated carbon, and deionized water. This complex composition leads to high cost and is prone to introducing new impurities. Furthermore, this method fails to achieve resourceful utilization of calcium.

[0006] CN119430258A discloses a method for recovering calcium fluoride and rare earths from chemical separation wastewater from rare earth smelting. The method comprises: (1) adding alkaline water to the chemical separation wastewater under stirring until the pH reaches 1.5-4.5, maintaining stirring and aging for 30-60 minutes, performing solid-liquid separation, and the resulting liquid is the defluorinated rare earth supernatant. The resulting solid filter cake is washed and dried to obtain a calcium fluoride byproduct. (2) adding an extractant to the defluorinated rare earth supernatant under stirring, removing the organic phase after liquid separation, and obtaining a saturated organic phase. (3) adding hydrochloric acid to the saturated organic phase, back-extracting and stirring, separating the aqueous phase and the organic phase, continuing to add water to the organic phase for washing, continuing to separate the aqueous phase and the organic phase, de-enriching the organic phase, mixing the aqueous phase, and detecting the acidity of the mixed aqueous phase to be 0.5-1.0 mol / L to obtain a rare earth chloride feed liquid. (4) Adding carbonate to the rare earth chloride solution under stirring, adjusting the pH to 2.5-3, and performing solid-liquid separation to obtain solid iron slag and purified rare earth chloride solution. This method treats the chemical separation wastewater by preferentially removing fluorine and extracting rare earths, achieving the recovery of rare earths and calcium fluoride. However, the lead, phosphorus, and iron in the chemical separation wastewater are enriched in the calcium fluoride, and the effective separation of the elements is not achieved, which limits the secondary utilization of the elements. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide a method for treating rare earth concentrate beneficiation wastewater, which can separate and recover lead, fluorine, iron, rare earth elements and calcium elements in rare earth concentrate beneficiation wastewater step by step, avoiding cross interference between elements.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] The method for treating rare earth concentrate beneficiation wastewater provided by the present invention comprises the following steps:

[0010] 1) adding an alkaline agent I to rare earth concentrate beneficiation wastewater and stirring until the pH value of the rare earth concentrate beneficiation wastewater reaches 1.5 to 4; then, adding a precipitant I to the rare earth concentrate beneficiation wastewater for precipitation reaction to obtain a reaction product I; separating the reaction product I into a solid-liquid state to obtain a lead slag and a lead-removed supernatant; wherein the alkaline agent I is selected from at least one of calcium oxide, calcium hydroxide, and lime milk; the precipitant I is selected from at least one of an alkali metal sulfide and ammonium sulfide; and the molar ratio of the precipitant I to the lead ions in the rare earth concentrate beneficiation wastewater is 1 to 3:1;

[0011] 2) adding a calcium agent to the lead removal supernatant, adjusting the pH value of the lead removal supernatant to 4-6.5 with an alkaline agent II, then adding a flocculant to a concentration of 0.2-2 mg / L, and reacting at 25-95° C. with stirring to obtain a reaction product II; separating the reaction product II from a solid and a liquid to obtain a fluorine slag and a defluorinated supernatant; wherein the calcium agent is selected from at least one of calcium salts, calcium oxide, and calcium hydroxide; the molar ratio of the calcium agent to the fluoride ions in the rare earth concentrate beneficiation wastewater is 0.2-0.5:1; the alkaline agent II is selected from at least one of calcium oxide, calcium hydroxide, and lime milk; and the flocculant is selected from at least one of PAM and PAC;

[0012] 3) The defluorinated supernatant was heated at 10-30 mA / cm 2 Electrolysis is performed at a current density of , and the mixture is allowed to stand to obtain a reaction product III; solid-liquid separation of the reaction product III is performed to obtain iron slag and an iron-removing supernatant;

[0013] 4) adding phosphate to the iron removal supernatant, then adding precipitant II until the pH value of the iron removal supernatant reaches 4-5, and reacting at 40-80° C. to obtain a reaction product IV; separating the reaction product IV into a solid-liquid state to obtain a phosphate precipitate of rare earth elements and a rare earth removal supernatant; wherein the phosphate is selected from at least one of ammonium phosphate and alkali metal phosphate; the molar ratio of the phosphate radical of the phosphate to the rare earth elements in the rare earth concentrate chemical separation wastewater is 1-2:1; and the precipitant II is selected from at least one of ammonia water and alkali metal hydroxide;

[0014] 5) evaporating and concentrating the rare earth-removing supernatant until the mass concentration of calcium chloride is 40-60 wt %, to obtain an evaporation concentrate;

[0015] The evaporated concentrated liquid is cooled at 10-50°C and solid-liquid separated to obtain CaCl2·2H2O crystals and mother liquor.

[0016] According to the treatment method of the present invention, preferably, in step 1), the mass concentration of calcium hydroxide in the lime milk is 10-30 wt%; and the alkali metal sulfide salt is sodium sulfide.

[0017] According to the treatment method of the present invention, preferably, in step 1), the precipitation reaction time is 20 to 60 minutes.

[0018] According to the treatment method of the present invention, preferably, in step 1), stirring is performed during the precipitation reaction.

[0019] According to the treatment method of the present invention, preferably, in step 2), the calcium salt is selected from at least one of calcium chloride and calcium sulfate; and the mass concentration of calcium hydroxide in the lime milk is 10 to 30 wt%.

[0020] According to the treatment method of the present invention, preferably, in step 2), the reaction time is 0.5 to 5 hours.

[0021] According to the treatment method of the present invention, preferably, in step 3), the electrolysis time is 20 to 60 minutes.

[0022] According to the treatment method of the present invention, preferably, in step 3), the standing time is 5 to 40 minutes.

[0023] According to the treatment method of the present invention, preferably, in step 4), the reaction time is 1 to 5 hours.

[0024] According to the treatment method of the present invention, preferably, in step 5), the evaporation concentration is a triple-effect evaporation concentration; and the mother liquor is returned to step 2) for use as a calcium agent.

[0025] The present invention can separate and recover lead, fluorine, iron, rare earth elements and calcium in the wastewater of rare earth concentrate by step-by-step direction, thus avoiding cross-interference between elements. The present invention uses a sulfur-containing precipitant to precipitate lead under low pH conditions, thus avoiding co-precipitation of iron and rare earth elements. The present invention uses electrolytic precipitation of iron, using Fe 2+ Replaces external iron salts and reduces the introduction of impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a process flow chart. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0028] The "REO" mentioned in the present invention refers to rare earth oxides.

[0029] <Treatment Method for Rare Earth Concentrate Wastewater>

[0030] The method for treating rare earth concentrate beneficiation wastewater of the present invention comprises a pre-neutralization and lead removal step, a neutralization and fluorine removal step, an electric flocculation and iron removal step, a phosphate method for extracting rare earths, and a calcium chloride concentration and crystallization step, which is described in detail below.

[0031] Pre-neutralization and lead removal steps

[0032] An alkaline agent I is added to rare earth concentrate beneficiation wastewater and stirred until the pH value of the rare earth concentrate beneficiation wastewater reaches 1.5 to 4; then, a precipitant I is added to the rare earth concentrate beneficiation wastewater to carry out a precipitation reaction to obtain a reaction product I; and the reaction product I is separated into a solid and liquid to obtain a lead slag and a lead-removed supernatant.

[0033] The present invention is applicable to chemical separation wastewater of all types of rare earth concentrates, preferably chemical separation wastewater of Bayan Obo rare earth concentrate, and more preferably rare earth concentrate chemical separation wastewater having the following main component concentrations:

[0034] Acidity 0.2~2mol / L, REO 0.1~4g / L, Ca 25~90g / L, Pb 0.5~8g / L, Fe 1~8g / L, P5~16g / L, F 1~8g / L and Cl 20~120g / L.

[0035] The acidity of the rare earth concentrate beneficiation wastewater of the present invention may be 0.2 to 2 mol / L, preferably 0.3 to 1.8 mol / L, and more preferably 0.5 to 1.5 mol / L. The concentration of RE may be 0.1 to 4 g / L, preferably 0.2 to 3 g / L, and more preferably 0.3 to 2 g / L. The concentration of Ca may be 25 to 90 g / L, preferably 28 to 85 g / L, and more preferably 30 to 80 g / L. The concentration of Pb may be 0.5 to 8 g / L, preferably 1 to 7 g / L, and more preferably 2 to 6 g / L. The concentration of Fe may be 1 to 8 g / L, preferably 2 to 7 g / L, and more preferably 3 to 5 g / L. The concentration of P may be 5 to 16 g / L, preferably 7 to 15 g / L, and more preferably 9 to 14 g / L. The concentration of F may be 1 to 8 g / L, preferably 1.5 to 7 g / L, and more preferably 2 to 6 g / L. The concentration of Cl may be 20 to 120 g / L, preferably 22 to 115 g / L, and more preferably 24 to 110 g / L.

[0036] According to one embodiment of the present invention, the alkaline agent I can be selected from at least one of calcium oxide, calcium hydroxide, and lime milk, preferably at least one of calcium oxide and lime milk, more preferably calcium oxide or lime milk. The mass concentration of calcium hydroxide in the lime milk can be 10-30wt%, preferably 13-28wt%, and more preferably 15-26wt%.

[0037] According to one embodiment of the present invention, the precipitant I can be selected from at least one of an alkali metal sulfide salt and ammonium sulfide, preferably at least one of an alkali metal sulfide salt, more preferably sodium sulfide. In the present invention, the precipitant I can be a salt containing crystal water or an anhydrous salt, as long as it can precipitate lead ions, and is not particularly limited here.

[0038] According to one embodiment of the present invention, the molar ratio of the precipitant I to the lead ions in the rare earth concentrate beneficiation wastewater can be 1 to 3:1, preferably 1.1 to 2.8:1, and more preferably 1.2 to 2.5:1.

[0039] According to one embodiment of the present invention, after adding the alkaline agent I, the pH value of the rare earth concentrate beneficiation wastewater can be 1.5-4, preferably 1.8-3.5, and more preferably 2-3.

[0040] Reasonable alkaline agent I and precipitant I and their dosage can ensure the effective precipitation and separation of lead under low pH conditions while avoiding co-precipitation of iron and rare earth elements.

[0041] According to one embodiment of the present invention, the precipitation reaction time may be 20 to 60 minutes, preferably 25 to 55 minutes, and more preferably 28 to 45 minutes.

[0042] According to a preferred embodiment of the present invention, after the pH value of the rare earth concentrate beneficiation wastewater reaches 1.5 to 4, stirring can be continued for a certain period of time before adding the precipitant I. The stirring time can be 10 to 60 minutes, preferably 15 to 50 minutes, and more preferably 20 to 45 minutes.

[0043] In the present invention, stirring may be continued during the precipitation reaction.

[0044] In the present invention, the stirring rotation speed may be 200 to 400 rpm, preferably 220 to 380 rpm, and more preferably 250 to 350 rpm.

[0045] Reasonable reaction conditions can ensure the effective precipitation and separation of lead at a lower pH value, while avoiding the co-precipitation of iron and rare earth elements.

[0046] In the present invention, the main component of the lead slag is lead concentrate (lead sulfide).

[0047] The solid-liquid separation involved in the present invention can be achieved by any filtration method or filtration equipment known in the art, which will not be described in detail here. For example, it can be press filtration or centrifugal separation. The rotation speed of the centrifugal separation can be 2000 to 5000 rpm, preferably 2500 to 4500 rpm, and more preferably 2700 to 4000 rpm.

[0048] The water involved in the present invention can be any type of water known in the art for leaching and separation of rare earth elements, which will not be described in detail here.

[0049] Neutralization and fluoride removal step

[0050] A calcium agent is added to the lead removal supernatant, and the pH value of the lead removal supernatant is adjusted to 4 to 6.5 with an alkaline agent II. Subsequently, a flocculant is added to a concentration of 0.2 to 2 mg / L, and the reaction is carried out at 25 to 95° C. under stirring conditions to obtain a reaction product II; the reaction product II is separated into a solid and a liquid to obtain a fluorine slag and a fluorine removal supernatant.

[0051] According to one embodiment of the present invention, the calcium agent can be selected from at least one of calcium salt, calcium oxide, and calcium hydroxide, preferably calcium salt or calcium oxide, more preferably calcium salt. The calcium salt can be selected from at least one of calcium chloride and calcium sulfate, preferably calcium chloride or calcium sulfate, more preferably calcium chloride.

[0052] According to one embodiment of the present invention, the molar ratio of the calcium agent to the fluoride ions in the rare earth concentrate beneficiation wastewater can be 0.2-0.5:1, preferably 0.25-0.45:1, and more preferably 0.3-0.4:1.

[0053] According to one embodiment of the present invention, the alkaline agent II can be selected from at least one of calcium oxide, calcium hydroxide, and lime milk, preferably at least one of calcium hydroxide and lime milk, more preferably calcium hydroxide or lime milk. The mass concentration of calcium hydroxide in the lime milk can be 10-30wt%, preferably 13-28wt%, and more preferably 15-26wt%.

[0054] According to one embodiment of the present invention, the pH value of the lead removal supernatant can be adjusted to 4 to 6.5, preferably 4.2 to 6.3, and more preferably 4 to 6.

[0055] According to one embodiment of the invention, the flocculant can be selected from at least one of PAM (polyacrylamide) and PAC (polyaluminum chloride), preferably PAM or PAC, and more preferably PAM. The flocculant can be added to a concentration of 0.2 to 2 mg / L, preferably 0.5 to 1.8 mg / L, and more preferably 0.8 to 1.5 mg / L.

[0056] Reasonable calcium agent, alkaline agent II and flocculant and their dosage can ensure the effective precipitation and separation of fluorine element, and at the same time help to avoid the co-precipitation of other elements.

[0057] According to one embodiment of the present invention, the reaction temperature may be 25 to 95° C., preferably 45 to 90° C., more preferably 60 to 80° C. The reaction time may be 0.5 to 5 h, preferably 0.8 to 4 h, more preferably 1 to 3 h.

[0058] In the present invention, the stirring rotation speed may be 200 to 400 rpm, preferably 220 to 380 rpm, and more preferably 250 to 350 rpm.

[0059] Reasonable reaction conditions can ensure the effective precipitation and separation of fluorine, while helping to avoid the co-precipitation of other elements.

[0060] In the present invention, the main component of the fluorine slag is calcium fluoride.

[0061] Electrocoagulation iron removal steps

[0062] The defluorinated supernatant was heated at 10-30 mA / cm 2 Electrolysis is carried out at a current density of , and the reaction product III is allowed to stand to obtain reaction product III; the reaction product III is separated into solid and liquid to obtain iron slag and iron-removing supernatant.

[0063] According to one embodiment of the present invention, the current density of electrolysis can be 10-30 mA / cm 2 , preferably 12 to 28 mA / cm 2 , more preferably 15 to 25 mA / cm 2 The electrolysis time may be 20 to 60 minutes, preferably 25 to 55 minutes, and more preferably 30 to 50 minutes.

[0064] According to one embodiment of the present invention, the standing time may be 5 to 40 minutes, preferably 8 to 37 minutes, and more preferably 10 to 35 minutes.

[0065] The electrolysis of the present invention can be carried out in an electrocoagulation reactor, and the electrocoagulation reactor can use any type of electrocoagulation reactor known in the art, which will not be described in detail here. According to a preferred embodiment of the present invention, the anode of the electrocoagulation reactor is iron and the cathode is graphite.

[0066] In the present invention, the reaction product III is Fe(OH)3 flocs, and the main component of the iron slag is Fe(OH)3. The iron slag can generate Fe2O3 after calcination.

[0067] Limiting the electrolysis conditions to the above range can ensure the effective precipitation and separation of iron elements, while helping to prevent other elements and impurities from entering the precipitation.

[0068] Phosphate method for extracting rare earths

[0069] Phosphate is added to the iron removal supernatant, and then a precipitant II is added until the pH value of the iron removal supernatant reaches 3-5, and the reaction is carried out at 40-80° C. to obtain a reaction product IV; the reaction product IV is separated into a solid and a liquid to obtain a phosphate precipitate of rare earth elements and a rare earth removal supernatant.

[0070] According to one embodiment of the present invention, the phosphate may be selected from at least one of ammonium phosphate and alkali metal phosphate, preferably at least one of ammonium phosphate and sodium phosphate, more preferably ammonium phosphate or sodium phosphate.

[0071] According to one embodiment of the present invention, the molar ratio of the phosphate radical of the phosphate to the rare earth element in the rare earth concentrate beneficiation wastewater may be 1-2:1, preferably 1-1.5:1, and more preferably 1-1.3:1.

[0072] According to one embodiment of the present invention, the precipitant II can be selected from at least one of ammonia water and alkali metal hydroxides, preferably at least one of ammonia water and sodium hydroxide, more preferably ammonia water or sodium hydroxide.

[0073] According to one embodiment of the present invention, after adding the precipitant II, the pH value of the iron removal supernatant may be 3 to 5, preferably 3.2 to 4.8, and more preferably 3.5 to 4.5.

[0074] Reasonable phosphate and precipitant II and their dosage can ensure effective precipitation and separation of rare earth elements, improve the purity of rare earth element phosphate, and help avoid co-precipitation of other elements.

[0075] According to one embodiment of the present invention, the reaction temperature may be 40-80° C., preferably 45-75° C., more preferably 50-70° C. The reaction time may be 1-5 h, preferably 1.5-4.5 h, more preferably 1.5-4 h.

[0076] According to a preferred embodiment of the present invention, stirring may be performed during the reaction process, and the stirring speed may be 200 to 400 rpm, preferably 220 to 380 rpm, and more preferably 250 to 350 rpm.

[0077] Reasonable reaction conditions can ensure the effective precipitation and separation of rare earth elements, improve the purity of rare earth element phosphates, and help avoid co-precipitation of other elements.

[0078] In the present invention, the phosphate of the rare earth element can be used in the alkaline decomposition process of decomposing the rare earth concentrate by the normal pressure alkaline method, so as to realize the recovery of the rare earth element.

[0079] Calcium chloride concentration and crystallization steps

[0080] The rare earth-removed supernatant is evaporated and concentrated to a mass concentration of calcium chloride of 40-60 wt % to obtain an evaporation concentrate; the evaporation concentrate is cooled at 10-50 DEG C and solid-liquid separated to obtain CaCl2·2H2O crystals and a mother liquor.

[0081] According to one embodiment of the present invention, evaporation concentration can be triple-effect evaporation concentration. Triple-effect evaporation concentration can be implemented in any type of triple-effect evaporator known in the art, which will not be described in detail here.

[0082] In the present invention, after evaporation and concentration, the mass concentration of calcium chloride can be 40 to 60 wt %, preferably 42 to 58 wt %, and more preferably 45 to 55 wt %.

[0083] According to one embodiment of the present invention, the cooling temperature may be 10-50° C., preferably 15-40° C., more preferably 18-30° C. The cooling time may be 0.2-5 h, preferably 0.3-4 h, more preferably 0.5-3 h.

[0084] Reasonable concentration, evaporation and cooling conditions are beneficial to improving the recovery rate of calcium chloride and the purity of the obtained CaCl2·2H2O crystals.

[0085] According to one embodiment of the present invention, the mother liquor can be returned to the neutralization and defluorination step to be used as a calcium agent, thereby achieving recycling.

[0086] In the present invention, the condensed water generated during the evaporation and concentration process can be used to prepare the acid solution in the rare earth concentrate beneficiation and calcium removal process, thereby realizing wastewater utilization and reducing energy consumption.

[0087] <Test method>

[0088] Determination of REO content: Inductively coupled plasma spectrometry was used.

[0089] Calculation of REO moles: Calculate using equation (1):

[0090] REO molar concentration = REO mass concentration / M(1)

[0091] Wherein, REO mass concentration is the content of REO, and the unit is g / L; M is the molar mass of the mixed rare earth oxide, specifically 169 g / mol.

[0092] Determination of P content: Inductively coupled plasma spectrometry was used.

[0093] Determination of F content: fluoride ion selective electrode method was used.

[0094] Determination of Ca content: Inductively coupled plasma spectrometry was used.

[0095] <Ingredients>

[0096] Unless otherwise specified, the raw materials in the following examples are all commercially available products.

[0097] The electrocoagulation reactor is a PREDEST-20 electrocoagulation reactor produced by Yasa Environmental Technology (Shanghai) Co., Ltd.

[0098] The triple-effect evaporator is a 100L triple-effect forced circulation wastewater crystallization evaporator produced by Liangshan Tairui Chemical Equipment Trading Co., Ltd.

[0099] Example 1

[0100] The concentrations of the main components in the rare earth concentrate beneficiation wastewater used in this embodiment are as follows:

[0101] Acidity 0.68mol / L, REO 0.325g / L, Ca 57.23g / L, Pb 2.54g / L, Fe3.87g / L, P 9.34g / L, F 2.01g / L, Cl 94.70g / L.

[0102] The steps for treating rare earth concentrate beneficiation wastewater are as follows:

[0103] (1) Pre-neutralization and lead removal: add lime milk with a mass concentration of 20 wt% of Ca(OH)2 to 1000 mL of rare earth concentrate beneficiation wastewater while stirring at a speed of 250 rpm, stir until the pH value of the rare earth concentrate beneficiation wastewater reaches 2, and continue stirring for 30 minutes. Then, add 3.55 g of Na2S·9H2O (the molar ratio of Na2S to lead ions in the rare earth concentrate beneficiation wastewater is 1.2:1) to the rare earth concentrate beneficiation wastewater for precipitation reaction for 30 minutes to obtain reaction product I. The reaction product I is separated by filtration to obtain lead slag and lead removal supernatant. In the lead removal supernatant, Pb 2+ The concentration is 0.08 mg / L.

[0104] (2) Neutralization and fluorine removal: 4.67 g of calcium chloride was added to the lead removal supernatant (the molar ratio of calcium chloride to fluoride ions in the rare earth concentrate beneficiation wastewater was 0.38:1), the pH value of the lead removal supernatant was adjusted to 6 with calcium hydroxide, PAM was added to a concentration of 1.0 mg / L, and then the mixture was stirred at 70°C and 250 rpm for 1 hour to obtain reaction product II. The reaction product II was centrifuged at a speed of 3000 rpm to obtain fluorine slag and defluorine supernatant. The main component of the fluorine slag is CaF2, and the purity of CaF2 is 90 wt%. In the defluorine supernatant, F - The concentration is 5 mg / L.

[0105] (3) Electrocoagulation for iron removal: Add the defluorinated supernatant into the electrocoagulation reactor at 15 mA / cm 2 Electrolysis was performed at a current density of 100 nm for 30 minutes, followed by 10 minutes of rest to obtain reaction product III. Reaction product III was centrifuged at 3000 rpm to obtain iron slag and an iron-removed supernatant. The iron slag was calcined to produce Fe2O3 with a purity of 95 wt%.

[0106] (4) Extraction of rare earths by phosphate method: 0.34 g of ammonium phosphate was added to the iron removal supernatant (PO4 3-The molar ratio of the rare earth elements in the rare earth concentrate beneficiation wastewater was 1.2:1. NH3·H2O was then added until the pH of the iron-removed supernatant reached 4.2. The mixture was then stirred at 50°C and 250 rpm for 2 hours to obtain reaction product IV. Reaction product IV was centrifuged at 3000 rpm to obtain a phosphate precipitate of the earth elements (REPO4 precipitate) and a rare earth-removed supernatant.

[0107] (5) Calcium chloride concentration and crystallization: The rare earth removal supernatant was placed in a triple-effect evaporator and concentrated by triple-effect evaporation until the CaCl2 mass concentration in the rare earth removal supernatant was 45 wt%, thereby obtaining an evaporation concentrate. The evaporation concentrate was cooled at 25°C for 3 h to precipitate crystals, which were then centrifuged at 3000 rpm to obtain CaCl2·2H2O crystals and mother liquor. The condensed water generated during the triple-effect evaporation concentration process was used to prepare the acid solution for the calcium removal process of rare earth concentrate beneficiation, and the condensed water reuse rate was 92%.

[0108] Example 2

[0109] The concentrations of the main components in the rare earth concentrate beneficiation wastewater used in this embodiment are as follows:

[0110] Acidity 1.28mol / L, REO 1.25g / L, Ca 30.44g / L, Pb 1.13g / L, Fe4.29g / L, P 13.57g / L, F 3.4g / L, Cl 24.27g / L.

[0111] The steps for treating rare earth concentrate beneficiation wastewater are as follows:

[0112] (1) Pre-neutralization and lead removal: add lime milk with a mass concentration of 20 wt% of Ca(OH)2 to 1000 mL of rare earth concentrate beneficiation wastewater while stirring at a speed of 250 rpm, stir until the pH value of the rare earth concentrate beneficiation wastewater reaches 2, and continue stirring for 30 minutes. Then, add 1.58 g of Na2S·9H2O (the molar ratio of Na2S to lead ions in the rare earth concentrate beneficiation wastewater is 1.25:1) to the rare earth concentrate beneficiation wastewater for precipitation reaction for 30 minutes to obtain reaction product I. The reaction product I is separated by filter press to obtain lead slag and lead removal supernatant. In the lead removal supernatant, Pb 2+ The concentration is 0.046 mg / L.

[0113] (2) Neutralization and fluorine removal: 6.94 g of calcium chloride was added to the lead removal supernatant (the molar ratio of calcium chloride to fluoride ions in the rare earth concentrate beneficiation wastewater was 0.35:1), the pH value of the lead removal supernatant was adjusted to 4.5 with calcium hydroxide, PAM was added to a concentration of 1.1 mg / L, and then the mixture was stirred at 70°C and 250 rpm for 1 hour to obtain reaction product II. The reaction product II was centrifuged at a speed of 3000 rpm to obtain fluorine slag and defluorine supernatant. The main component of the fluorine slag is CaF2, and the purity of CaF2 is 91 wt%. In the defluorine supernatant, F - The concentration is 7.2 mg / L.

[0114] (3) Electrocoagulation for iron removal: Add the defluorinated supernatant into the electrocoagulation reactor at 15 mA / cm 2 Electrolysis was performed at a current density of 100 nm for 40 minutes, followed by 30 minutes of rest to obtain reaction product III. Reaction product III was centrifuged at 3000 rpm to obtain iron slag and an iron-removed supernatant. The iron slag was calcined to produce Fe2O3 with a purity of 95.7 wt%.

[0115] (4) Extraction of rare earths by phosphate method: 1.21 g of ammonium phosphate was added to the iron removal supernatant (PO4 3- The reaction mixture was stirred at 50°C and 250 rpm for 2 hours to obtain a reaction product IV. The reaction product IV was centrifuged at 3000 rpm to obtain a rare earth element phosphate precipitate (REPO4 precipitate) and a rare earth-removing supernatant.

[0116] (5) Calcium chloride concentration and crystallization: The rare earth removal supernatant was placed in a triple-effect evaporator and concentrated by triple-effect evaporation until the CaCl2 mass concentration in the rare earth removal supernatant was 50 wt%, thereby obtaining an evaporation concentrate. The evaporation concentrate was cooled at 25°C for 30 min to precipitate crystals, which were then centrifuged at 3000 rpm to obtain CaCl2·2H2O crystals and mother liquor. The condensed water generated during the triple-effect evaporation concentration process was used to prepare the acid solution for the calcium removal process of rare earth concentrate beneficiation, and the condensed water reuse rate was 94%.

[0117] Example 3

[0118] The concentrations of the main components in the rare earth concentrate beneficiation wastewater used in this embodiment are as follows:

[0119] Acidity 1.5mol / L, REO 4g / L, Ca 80g / L, Pb 5g / L, Fe 5g / L, P 14g / L, F 5g / L, Cl100g / L.

[0120] The steps for treating rare earth concentrate beneficiation wastewater are as follows:

[0121] (1) Pre-neutralization and lead removal: add lime milk with a mass concentration of 20 wt% of Ca(OH)2 to 1000 mL of rare earth concentrate beneficiation wastewater while stirring at a speed of 300 rpm, stir until the pH value of the rare earth concentrate beneficiation wastewater reaches 2.5, and continue stirring for 30 minutes. Then, add 12.5 g of Na2S·9H2O (the molar ratio of Na2S to lead ions in the rare earth concentrate beneficiation wastewater is 2.17:1) to the rare earth concentrate beneficiation wastewater for precipitation reaction for 40 minutes to obtain reaction product I. The reaction product I is separated by filter press to obtain lead slag and lead removal supernatant. In the lead removal supernatant, Pb 2+ The concentration is 0.05 mg / L.

[0122] (2) Neutralization and fluorine removal: The mother liquor obtained by concentrated crystallization of calcium chloride and calcium chloride solid (calcium chloride content is 10.22g) are mixed and added to the lead removal supernatant (the molar ratio of calcium chloride to fluoride ions in rare earth concentrate beneficiation wastewater is 0.35:1), the pH value of the lead removal supernatant is adjusted to 6.2 with calcium hydroxide, PAM is added to a concentration of 1.2mg / L, and then reacted at 75°C and a speed of 250rpm for 1h to obtain reaction product II. Reaction product II is centrifuged at a speed of 3000rpm to obtain fluorine slag and defluorine supernatant. The main component of the fluorine slag is CaF2, and the purity of CaF2 is 92.3wt%. In the defluorine supernatant, F - The concentration is 8.0 mg / L.

[0123] (3) Electrocoagulation for iron removal: Add the defluorination supernatant into the electrocoagulation reactor at 25 mA / cm 2 Electrolysis was performed at a current density of 100 nm for 540 minutes, followed by 10 minutes of rest to obtain reaction product III. Reaction product III was centrifuged at 3000 rpm to obtain iron slag and an iron-removed supernatant. The iron slag was calcined to produce Fe2O3 with a purity of 95 wt%.

[0124] (4) Phosphate method for extracting rare earths: Add 4.0 g of ammonium phosphate to the iron removal supernatant (PO4 3-The reaction mixture was stirred at 60°C and 250 rpm for 2 hours to obtain a reaction product IV. The reaction product IV was centrifuged at 3000 rpm to obtain a rare earth element phosphate precipitate (REPO4 precipitate) and a rare earth-removing supernatant.

[0125] (5) Calcium Chloride Concentration and Crystallization: The rare earth removal supernatant was placed in a triple-effect evaporator and concentrated by triple-effect evaporation until the CaCl2 mass concentration in the rare earth removal supernatant was 50 wt%, thereby obtaining an evaporation concentrate. The evaporation concentrate was cooled at 20°C for 2 h to precipitate crystals, which were then centrifuged at 3000 rpm to obtain CaCl2·2H2O crystals and mother liquor. The condensed water generated during the triple-effect evaporation and concentration process was used to prepare the acid solution for the calcium removal process of rare earth concentrate beneficiation, and the condensed water reuse rate was 92%.

[0126] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for treating rare earth concentrate beneficiation wastewater, characterized in that: The following steps are involved: 1) adding an alkaline agent I to rare earth concentrate beneficiation wastewater and stirring until the pH value of the rare earth concentrate beneficiation wastewater reaches 1.5 to 4; then, adding a precipitant I to the rare earth concentrate beneficiation wastewater for precipitation reaction to obtain a reaction product I; separating the reaction product I into a solid-liquid state to obtain a lead slag and a lead-removed supernatant; wherein the alkaline agent I is selected from at least one of calcium oxide, calcium hydroxide, and lime milk; the precipitant I is selected from at least one of an alkali metal sulfide and ammonium sulfide; and the molar ratio of the precipitant I to the lead ions in the rare earth concentrate beneficiation wastewater is 1 to 3:1; 2) adding a calcium agent to the lead removal supernatant, adjusting the pH value of the lead removal supernatant to 4-6.5 with an alkaline agent II, then adding a flocculant to a concentration of 0.2-2 mg / L, and reacting at 25-95° C. with stirring to obtain a reaction product II; separating the reaction product II from a solid and a liquid to obtain a fluorine slag and a defluorinated supernatant; wherein the calcium agent is selected from at least one of calcium salts, calcium oxide, and calcium hydroxide; the molar ratio of the calcium agent to the fluoride ions in the rare earth concentrate beneficiation wastewater is 0.2-0.5:1; the alkaline agent II is selected from at least one of calcium oxide, calcium hydroxide, and lime milk; and the flocculant is selected from at least one of PAM and PAC; 3) The defluorinated supernatant was heated at 10-30 mA / cm 2 Electrolysis is performed at a current density of , and the mixture is allowed to stand to obtain a reaction product III; solid-liquid separation of the reaction product III is performed to obtain iron slag and an iron-removing supernatant; 4) adding phosphate to the iron removal supernatant, then adding precipitant II until the pH value of the iron removal supernatant reaches 3-5, reacting at 40-80° C. to obtain a reaction product IV; separating the reaction product IV into a solid-liquid state to obtain a phosphate precipitate of rare earth elements and a rare earth removal supernatant; wherein the phosphate is selected from at least one of ammonium phosphate and alkali metal phosphate; the molar ratio of the phosphate radical of the phosphate to the rare earth elements in the rare earth concentrate chemical separation wastewater is 1-2:1; and the precipitant II is selected from at least one of ammonia water and alkali metal hydroxide; 5) evaporating and concentrating the rare earth-removing supernatant until the mass concentration of calcium chloride is 40-60 wt %, to obtain an evaporation concentrate; The evaporated concentrated liquid is cooled at 10-50°C and solid-liquid separated to obtain CaCl2·2H2O crystals and mother liquor.

2. The processing method according to claim 1, characterized in that In step 1), the mass concentration of calcium hydroxide in the lime milk is 10-30 wt%; and the alkali metal sulfide salt is sodium sulfide.

3. The processing method according to claim 1, characterized in that In step 1), the precipitation reaction time is 20 to 60 minutes.

4. The processing method according to claim 1, characterized in that In step 1), stirring is performed during the precipitation reaction.

5. The processing method according to claim 1, characterized in that In step 2), the calcium salt is selected from at least one of calcium chloride and calcium sulfate; and the mass concentration of calcium hydroxide in the lime milk is 10 to 30 wt%.

6. The processing method according to claim 1, characterized in that In step 2), the reaction time is 0.5 to 5 hours.

7. The processing method according to claim 1, characterized in that In step 3), the electrolysis time is 20 to 60 minutes.

8. The processing method according to claim 1, characterized in that In step 3), the standing time is 5 to 40 minutes.

9. The processing method according to claim 1, characterized in that: In step 4), the reaction time is 1 to 5 hours.

10. The processing method according to claim 1, characterized in that: In step 5), the evaporation concentration is a triple-effect evaporation concentration; the mother liquor is returned to step 2) and used as a calcium agent.

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