Treatment technology of wastewater generated by alkaline separation of rare earth ores

Abstract

The present invention belongs to the field of rare earth wastewater treatment technology, and specifically relates to a treatment process for wastewater generated by alkaline separation of rare earth ores. The treatment process for wastewater generated by alkaline separation of rare earth ores according to the present invention comprises the following steps: the first-level defluorination is to collect acidic wastewater and alkaline wastewater respectively into the 1# regulating tank through the supernatant pump, and acid-base neutralization reaction is carried out to control the reaction pH to be 8.0-9.0; ferrous chloride, cerium lanthanum chloride, calcium chloride, and polyacrylamide are used for adjustment treatment; the second-level defluorination is to use alkaline wastewater to adjust the pH of the 2# coagulation tank A pool to 8.0-9.0, and calcium chloride, cerium lanthanum chloride, and polyacrylamide are added for treatment, and cerium lanthanum chloride, alkaline solution, and polyacrylamide are added for treatment of tertiary defluorination, and the pH is controlled to be 6.0-6.5. The treatment process for wastewater generated by alkaline separation of rare earth ores provided by the present invention has good defluorination and dephosphorization effects, and reduces the cost of rare earth chloride separation and sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth wastewater treatment, and in particular relates to a treatment process for wastewater generated by separating rare earth ores using an alkali method. Background Art

[0002] In the process of mineral resource development and utilization, the mining and processing of rare earth ores is a crucial link. However, the mining and smelting process of rare earth ores is also accompanied by the generation of a large amount of wastewater, which contains complex chemical components and poses a severe challenge to the environment.

[0003] There are many kinds of pollutants in rare earth mine wastewater, including but not limited to heavy metal ions (such as F, P, Ca, Mg, Al, etc.), acid and alkali substances, and harmful substances such as ammonia nitrogen. Among them, excessive discharge of elements such as fluorine (F) and phosphorus (P) may lead to eutrophication of water bodies and destroy the balance of aquatic ecosystems; metal ions such as calcium (Ca), magnesium (Mg) and aluminum (Al) will also affect water quality and cause poisoning to aquatic organisms when they accumulate to a certain concentration; and the presence of ammonia nitrogen not only consumes dissolved oxygen in water, causing water quality deterioration, but may also be converted into more toxic nitrites, further threatening water safety.

[0004] In addition, rare earth mine wastewater often exhibits different acid-base properties, including both acidic and alkaline wastewater. This difference in acid-base properties makes wastewater treatment more difficult, and more sophisticated treatment technologies are needed to ensure that wastewater meets environmental protection standards before discharge. Acidic wastewater may contain high concentrations of inorganic acids such as phosphoric acid and hydrochloric acid, while alkaline wastewater may be rich in alkaline substances such as sodium hydroxide. If these acid-base substances are discharged directly without proper treatment, they will cause serious acid-base pollution to the surrounding soil and water.

[0005] At present, although the treatment technology for rare earth mine wastewater has made some progress, there are still problems such as low treatment efficiency, high operating costs, and high risk of secondary pollution. Therefore, developing a new technology for the treatment of rare earth mine wastewater that is efficient, economical, and environmentally friendly to effectively remove various pollutants in wastewater is not only of great significance for protecting the ecological environment and ensuring water resource security, but is also the key to promoting the sustainable development of the rare earth industry.

[0006] Patent CN108298714A discloses a method for defluoridating wastewater in the smelting and separation of fluorocarbon cerium rare earth ore. The wastewater containing high concentration of calcium salt in the chlorination system in the smelting and separation of fluorocarbon cerium rare earth ore is used as a defluoridating agent to defluorinate the high-fluoride wastewater. The wastewater containing high concentration of calcium salt in the chlorination system is reused to avoid the discharge of the two wastewaters separately. The best result after wastewater treatment is 3.96ppm fluorine and 4100ppm residual calcium. This method uses calcium salt to defluorinate, and the amount of fluorine removed is very limited. After calcium chloride is used for defluoridation, the Ksp constant of calcium fluoride determines that the fluoride ion concentration in the water can only be reduced to 10~20mg / L. In order to reduce the fluoride in the water to a lower level, excessive addition of calcium chloride solution is required, which ultimately leads to a large amount of residual Ca in the water system. 2+ When the pH value and other conditions in the water change, precipitation forms and blocks the pipes. In addition, in heat exchangers, evaporators and other equipment, due to the poor thermal conductivity of scale, the heat transfer efficiency is reduced, the energy consumption of the equipment is increased, the production efficiency is reduced, and it also interferes with coagulation and precipitation, affecting the activity of microorganisms. Therefore, in the field of rare earths, the wastewater treated by this method is difficult to meet the requirements of the discharge standards and has great limitations. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies in the prior art and provide a treatment process for wastewater generated by separation of rare earth ores by alkaline method, which has good fluorine and phosphorus removal effects and reduces the cost of rare earth chloride separation and wastewater treatment.

[0008] The process for treating wastewater generated by the alkaline separation of rare earth ores of the present invention comprises the following steps:

[0009] (1) Primary defluorination:

[0010] a1. The collected acidic wastewater and alkaline wastewater enter the 1# regulating tank through the supernatant pump respectively for acid-base neutralization reaction to control the reaction pH to 8.0~9.0;

[0011] b1. Add ferrous chloride to 1# coagulation tank A, add lanthanum cerium chloride solution to 1# coagulation tank B, add calcium chloride to 1# coagulation tank C, stir and mix, the wastewater flows between 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles, add polyacrylamide (PAM) to the front end of 1# coagulation tank D, the mixed liquid slurry flows into 1# radial flow sedimentation tank by gravity, and the water is taken from the outlet of 1# coagulation tank D to measure F, P, Ca, and pH;

[0012] c1. Separate mud and water in the 1# radial flow sedimentation tank, and the supernatant with NTU (turbidity) < 60 will overflow directly into the recovery pool;

[0013] (2) Secondary defluorination:

[0014] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0015] b2. Use the alkaline wastewater in a1 to adjust the pH of 2# coagulation tank A to 8.0~9.0, add calcium chloride and lanthanum cerium chloride to 2# coagulation tank B, add polyacrylamide to 2# coagulation tank C, stir and mix, and circulate the wastewater between 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles to reduce the fluoride to 15~20ppm, and the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water is taken from the outlet of 2# coagulation tank C to measure F and pH;

[0016] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 0~100, and the supernatant enters the 3# regulating tank;

[0017] (3) Three-stage defluorination:

[0018] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and lanthanum cerium chloride solution is added, and then sent to the defluorination tank B and defluorination tank C for further reaction, and the pH of the material in the defluorination tank C is adjusted to 6.0~6.5, and the fluorine content is reduced to <1.5ppm, and then sent to the defluorination tank D and polyacrylamide is added, and then enters the inclined plate sedimentation tank through the defluorination tank E, and the water from the defluorination tank D is measured for F and pH;

[0019] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, the mud is pumped into the external drainage plate frame, the filtrate after filtration enters the external discharge tank, and then discharged to the sewage treatment plant, the mud residue enters the pulping tank and is pumped into the 2# coagulation tank A in the secondary defluorination.

[0020] In step a1, the pH is adjusted by hydrochloric acid, and the mass concentration of hydrochloric acid is 20% to 36%.

[0021] The amount of ferrous chloride added in step b1 is 0.5% to 2.5% of the total mass of the wastewater, the amount of lanthanum cerium chloride added is 0.5% to 1.5% of the total mass of the wastewater, the amount of calcium chloride added is 0.5% to 3.5% of the total mass of the wastewater, and the amount of polyacrylamide added is 0.2% to 1.0% of the total mass of the wastewater. The concentration of the calcium chloride solution is preferably 25% to 33%. The ferrous chloride is added in a ferrous chloride solution with a mass concentration of 8% to 13%.

[0022] In step b2, the amount of lanthanum cerium chloride added is 0.5% to 1.0% of the total mass of the wastewater, the amount of calcium chloride added is 2.5% to 4.0% of the total mass of the wastewater, and the amount of polyacrylamide added is 0.5% to 1.5% of the total mass of the wastewater.

[0023] In step a3, the amount of lanthanum cerium chloride added is 0.17% to 1.0% of the total mass of the wastewater, and the amount of polyacrylamide added is 0.1% to 0.5% of the total mass of the wastewater.

[0024] In step a3, the pH of the solution is adjusted to 6.0-6.5, and the solution is an alkaline solution, preferably a sodium hydroxide solution or a potassium hydroxide solution.

[0025] The calcium chloride is added in the form of a calcium chloride solution having a mass concentration of 25% to 33%.

[0026] The lanthanum cerium chloride is added in the form of a lanthanum cerium chloride solution with a mass concentration of 20% to 27%.

[0027] Step c1NTU (turbidity) ≥60, the supernatant overflows into the 2# regulating tank, the water in the 2# regulating tank enters the recycled water plate frame for plate and frame filtration, the filtrate enters the recycled water tank, the filter cake is slurried in the slurry tank and then transported to the 2# coagulation tank A pool by a pump.

[0028] In step c2, NTU (turbidity)>100, the supernatant overflow is closed, and the sludge is pumped from the bottom into the sludge temporary storage tank, and then enters the sludge plate and frame filter press.

[0029] The alkaline wastewater described in the present invention is the rare earth hydroxide formed after the solid sodium hydroxide used in the workshop rare earth mine is converted to alkali under high temperature conditions. Due to excessive alkali, recycled water is needed to wash the materials. The first three highly alkaline water production workshops are recycled and reused, and the post-washing alkaline water is discharged to the alkaline water collection pool of the water treatment workshop. The pollutants are F, P, ammonia nitrogen, etc. The acidic wastewater is the concentrate that enters the chemical separation tank after pulping, and hydrochloric acid is added for chemical separation. The chemical separation supernatant with higher acidity is collected in the workshop for subsequent use, and the recycled water is continued to be used for chemical separation. The washing water is discharged to the acid water collection pool of the water treatment workshop. The pollutants are F, P, Ca, Mg, Al, ammonia nitrogen, etc.

[0030] The water treatment process of the present invention is mainly divided into three-stage defluorination. The main pollutants F in acidic wastewater are 100-1000ppm, P is 100-4000ppm, and the main pollutants F in alkaline wastewater are 500-4000ppm, P is 500-2000ppm. The first-stage defluorination is to mix acidic wastewater and alkaline wastewater and treat them to control the index F (fluorine) <200ppm, P (phosphorus) <200ppm, and pH is 7.0-8.0. About 2 / 3 (volume) of the water is used as recycled water and returned to the workshop for recycling; the second-stage defluorination is the remaining about 1 / 3 (volume) of muddy sewage after the first-stage defluorination, which is treated and adjusted, and the index controls F <20ppm, P <1ppm; the third-stage defluorination is the water after the second-stage defluorination treatment is the raw water for deep defluorination, and the total drainage outlet F <1.5ppm.

[0031] The treatment process for wastewater generated by the alkaline separation of rare earth ores described in the present invention has high fluorine and phosphorus removal effects, and the principle is as follows:

[0032] (1) Principle of fluorine removal:

[0033] 1) Ion precipitation: Fluoride ions combine with rare earth element ions (lanthanum ions La³⁺ and cerium ions Ce³⁺) in lanthanum cerium chloride to form insoluble rare earth fluoride precipitates. The chemical reaction equation can be expressed as:

[0034] F⁻+La³⁺→LaF 3 ↓, F⁻ + Ce³⁺ → CeF 3 ↓.

[0035] 2) Adsorption and complexation: The active sites on the surface of lanthanum cerium chloride can undergo physical and chemical adsorption with fluoride ions. On the one hand, through electrostatic attraction, the positively charged surface of lanthanum cerium chloride and the negatively charged fluoride ions attract each other; on the other hand, certain groups on the surface of lanthanum cerium chloride may react chemically with fluoride ions to form chemical bonds, which enhances the stability of adsorption and further improves the defluorination effect. In addition to simple precipitation reactions, there is also complexation. Although LaF 3 and CeF 3 It mainly exists in the form of precipitation, but there are a small amount of complex ions in the solution, such as [LaF 6 ] 3- , [CeF 6 ] 3- Wait, this is because La 3+ and Ce 3+ With an empty electron orbital, F - They have lone pairs of electrons and form complexes between them.

[0036] (2) Phosphorus removal principle:

[0037] 1) Ion precipitation: The lanthanum (La³⁺) and cerium (Ce³⁺) ions in lanthanum cerium chloride react with phosphate ions (PO 4 3- ) to form insoluble phosphate precipitate. The reaction equation can be expressed as:

[0038] La³⁺+PO 4 3- =LaPO 4 ↓, Ce³⁺+PO 4 3- =CePO 4 ↓,

[0039] The resulting phosphate precipitate has a very low solubility, allowing phosphorus to be removed from the water.

[0040] 2) Adsorption and complexation: The active sites on the surface of cerium lanthanum chloride can react with PO 4 3- Ions undergo physical adsorption and chemical adsorption. Chemical adsorption: On the one hand, through electrostatic attraction, the positively charged surface of lanthanum cerium chloride and the negatively charged PO4 3- Ions attract each other; on the other hand, the metal ions (La³⁺, Ce³⁺, etc.) in lanthanum cerium chloride form coordination compounds with water molecules or other ligands. In the process of phosphorus removal, phosphate ions can exchange with the ligands in these coordination compounds, and the phosphate ions replace the original ligands and combine with the metal ions to form more stable phosphorus-containing coordination compounds, thereby fixing the phosphorus and achieving the purpose of phosphorus removal. Physical adsorption: Lanthanum cerium chloride will form substances or colloidal particles with a large specific surface area, and these particles have strong adsorption capacity. The lanthanum cerium chloride of the present invention is used for primary fluorine and phosphorus removal, as well as secondary fluorine removal and tertiary fluorine removal. The raw material is the output after the extraction and separation of mixed rare earth chloride. Lanthanum cerium chloride cannot be sold at a break-even price after deep processing. It is free of cost to use in sewage treatment, and it consumes materials that cannot be stored, which reduces the cost of rare earth chloride separation in disguised form.

[0041] The present invention uses lanthanum cerium chloride under the same conditions of F and P indicators, which reduces the calcium ion concentration in the recycled water, and the calcium ion concentration can be reduced from about 75ppm to about 30ppm. The present invention reduces the calcium ion concentration in the recycled water, and the calcium index in the recycled water has a greater impact on the alkali unit consumption in the rare earth ore separation process. At the same time, calcium ions form calcium hydroxide precipitation under alkaline conditions, mix into rare earth hydroxide, and finally enter the rare earth chloride mixture, which increases the difficulty of decalcification of the rare earth chloride mixture. At the same time, in the extraction process, the presence of calcium ions will cause the extraction system to be disordered and form a large amount of insolubles. Once the calcium ion content is high, a large amount of sodium hydroxide treatment is required, and the process of the present invention saves the treatment of sodium hydroxide. It is preliminarily estimated that the cost saving of sodium hydroxide is about 4.5 million / year. At the same time, the present invention uses lanthanum cerium chloride to replace part of calcium chloride and ferrous chloride, which reduces the consumption of calcium chloride, reduces the mud production, and saves about 1.5 million yuan / year. In addition, the calcium ion concentration of the recycled water is too high, which will also cause the problems of scaling of production equipment, increasing energy consumption, and pipeline blockage.

[0042] The pH of the secondary defluoridation water of the present invention is 7.0-8.0. After adding a large amount of calcium chloride, it becomes acidic. The traditional process needs to add a large amount of sodium hydroxide to adjust the pH. However, the present invention introduces alkaline water into the 2# coagulation tank A pool, and adjusts the flow of alkaline water and calcium chloride at any time to make the pH of the water outlet 7.0-7.5 and F 15-20ppm, saving 30% of sodium hydroxide solution, and the cost is about 2.53 million yuan / year.

[0043] In order to reduce production costs, the hydrochloric acid, calcium chloride, ferrous chloride and other raw materials used in the traditional process are all by-products. The COD (COD requirement index in the raw and auxiliary materials currently used is <2500ppm) and ammonia nitrogen pollutant index in the by-products are high, and the fluctuation is large and unstable, resulting in high COD in the drainage. The pollutant indexes in the lanthanum cerium chloride extracted and separated by the present invention are lower than those of the by-products, and the indexes are stable, which is conducive to the control of the indexes in the workshop. From the perspective of chemical reaction principles, the lanthanum cerium chloride defluorination and dephosphorization of the present invention has a smaller precipitation equilibrium constant (Ksp) when forming a precipitate, higher efficiency and better selectivity. Because the lanthanum cerium ion has an empty orbital, it can form a coordination bond with the fluoride ion or phosphate, and has a certain complex adsorption effect on the pollutants, reducing the amount of mud produced.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) In the process for treating wastewater generated by the alkaline separation of rare earth ores of the present invention, lanthanum cerium chloride is used as the raw material for primary fluorine and phosphorus removal, which not only consumes the mixed rare earth chloride separation product that cannot be stored, thereby reducing the separation cost of rare earth chloride, but also significantly reduces the alkali consumption and the formation of insoluble matter in the extraction process by reducing the calcium ion concentration in the recycled water. In addition, the use of lanthanum cerium chloride also reduces the risk of equipment scaling and pipeline blockage, thereby reducing energy consumption.

[0046] (2) The present invention provides a treatment process for wastewater generated by the alkali separation of rare earth ores. In the secondary defluorination process, the flow rates of alkaline water and calcium chloride are adjusted to achieve stable control of the pH value at the water outlet, thereby saving the cost of liquid alkali and reducing the cost of sewage treatment.

[0047] (3) The treatment process of wastewater generated by the alkaline separation of rare earth ores of the present invention uses lanthanum cerium chloride as the treatment raw material. Compared with traditional by-products such as hydrochloric acid, calcium chloride, and ferrous chloride, its pollutant index is lower and more stable, which is conducive to the control of the index in the workshop. At the same time, lanthanum cerium chloride has higher efficiency and better selectivity in removing fluorine and phosphorus, and the Ksp is smaller when the precipitate is formed. The lone pair of electrons of lanthanum cerium has a complex adsorption effect on pollutants, which reduces the amount of sludge produced. This not only improves the treatment effect, but also reduces the burden and cost of subsequent treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention is a schematic flow chart of a process for treating wastewater generated by the alkaline separation of rare earth ores.

[0049] Figure 2 This is a schematic diagram of the distribution of 1# regulating tank, 1# coagulation tank A, 1# coagulation tank B, 1# coagulation tank C, and 1# coagulation tank D in the primary defluorination system.

[0050] Figure 3This is a schematic diagram of the distribution of 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the secondary fluoride removal.

[0051] Figure 4 This is a schematic diagram of the distribution of defluorination tank A, defluorination tank B, defluorination tank C, defluorination tank D, and defluorination tank E in the three-stage defluorination. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with specific embodiments.

[0053] The raw materials and additives used in the following examples and comparative examples are all commercially available products. The distribution diagram of each pool and tank in the primary defluorination, secondary defluorination and tertiary defluorination is as follows: Figures 2~4 The ppm unit used in the present invention can be equivalently converted to mg / L in the industry.

[0054] like Figure 1 As shown, the process for treating wastewater generated by the alkaline separation of rare earth ores according to the present invention comprises the following steps:

[0055] (1) Primary defluorination:

[0056] a1. The collected acidic wastewater and alkaline wastewater are respectively pumped into the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction. When the acidic wastewater is insufficient, hydrochloric acid with a mass concentration of 20%~36% is used to control the reaction pH to 8.0~9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for pressure filtration; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for pressure filtration. The filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank.

[0057] b1. Add 0.5%~2.5% of the total mass of the wastewater to 1# coagulation tank A with a concentration of 8%-13% ferrous chloride solution, add 0.5%~1.5% of the total mass of the wastewater to 1# coagulation tank B with a concentration of 20%~27% lanthanum cerium chloride solution, add 0.5%~3.5% of the total mass of the wastewater to 1# coagulation tank C with a concentration of 25%~33%, stir and mix, the wastewater flows between 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles, add 0.2%~1.0% PAM of the total mass of the wastewater to the front end of 1# coagulation tank D, the mixed liquid slurry flows into 1# radial flow sedimentation tank by gravity, and water is taken from the outlet of 1# coagulation tank D to measure F, P, Ca, and pH;

[0058] c1. Carry out mud and water separation in the 1# radial flow sedimentation tank. If NTU (turbidity) is less than 60 and is qualified, the supernatant will overflow directly into the recovery pool; if NTU (turbidity) is ≥60, the supernatant will overflow into the 2# regulating tank. The water in the 2# regulating tank will enter the recovery water plate frame for plate and frame filter pressing. The filtrate will enter the recovery pool. The filter cake will be slurried in the slurry tank and then transported to the 2# coagulation tank A pool by pump.

[0059] (2) Secondary defluorination:

[0060] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0061] b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add 2.5%~4.0% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 25%~33% calcium chloride solution and 0.5%~1.0% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 20%~27%, add 0.5%~1.5% PAM of the total mass of the wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, reduce the fluoride to 15~20ppm, the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water is taken from the outlet of the 2# coagulation tank C to measure F and pH;

[0062] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 0~100, and the supernatant enters the 3# regulating tank; when the NTU (turbidity) is greater than 100, the supernatant overflow is closed and the sludge is pumped from the bottom into the sludge temporary storage tank, and then enters the sludge plate and frame filter press, which separates the mud and water. The filtrate after filtration enters the 3# regulating tank and the sludge is transported out.

[0063] (3) Three-stage defluorination:

[0064] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 20%~27% lanthanum cerium chloride solution is added, which is 0.17%~1.0% of the total mass of the wastewater. It is then sent to the defluorination tank B and defluorination tank C for further reaction, and an alkaline solution with a mass concentration of 20%~50% is used to adjust the pH of the material in the defluorination tank C to 6.0~6.5, reducing the fluorine content to <1.5ppm. It is then sent to the defluorination tank D and 0.1%~0.5% PAM of the total mass of the wastewater is added. It enters the inclined plate sedimentation tank through the defluorination tank E, and the water from the defluorination tank D is measured for F and pH.

[0065] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0066] The mass concentration of the lanthanum cerium chloride solution used in the present invention is 20% to 27%, the rest is water and ≤1% of inevitable rare earth impurities, and the COD of the lanthanum cerium chloride solution is less than 300ppm, and the ammonia nitrogen is less than 300ppm. The pH value is not recorded in detail as long as it is adjusted to a limited range.

[0067] Example 1

[0068] The process for treating wastewater generated by the alkaline separation of rare earth ores comprises the following steps:

[0069] (1) Primary defluorination:

[0070] a1. Collected acidic wastewater (F is 650ppm, P is 3950ppm) flow rate 26m 3 / h, alkaline wastewater (F is 2345ppm, P is 1647ppm) flow rate 150m 3 / h, and enter the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction, and then use hydrochloric acid with a mass concentration of 36% to adjust the pH to 8.0-9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame pump for filter pressing; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame pump for filter pressing. The filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank;

[0071] b1. Add 10.2% ferrous chloride with a mass concentration of 2.2% of the total mass of the wastewater to the 1# coagulation tank A, add 23.2% lanthanum cerium chloride solution with a mass concentration of 1.1% of the total mass of the wastewater to the 1# coagulation tank B, add 32% calcium chloride solution with a mass concentration of 1.2% of the total mass of the wastewater to the 1# coagulation tank C, stir and mix, the wastewater flows between the 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles, add 0.2% PAM of the total mass of the wastewater to the front end of the 1# coagulation tank D, the mixed liquid slurry flows into the 1# radial flow sedimentation tank by gravity, and the water at the outlet of the 1# coagulation tank D is measured for F, P, Ca, and pH;

[0072] c1. Separate mud and water in the 1# radial flow sedimentation tank, NTU (turbidity) is 35, which is qualified, and the supernatant directly overflows into the recovery tank.

[0073] (2) Secondary defluorination:

[0074] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0075] b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add 32% calcium chloride solution with a mass concentration of 3.7% of the total mass of the wastewater and 23.2% lanthanum cerium chloride solution with a mass concentration of 0.6% of the total mass of the wastewater to the 2# coagulation tank B, add 0.8% PAM of the total mass of the wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water at the outlet of the 2# coagulation tank C is taken to measure F and pH;

[0076] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 65. The supernatant enters the 3# regulating tank, and the bottom mud is pumped into the sludge temporary storage tank, and then enters the sludge plate and frame filter press. The plate and frame filter press is used to separate the mud and water. The filtrate after filtration enters the 3# regulating tank, and the sludge is transported out.

[0077] (3) Three-stage defluorination:

[0078] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 23.2% lanthanum cerium chloride solution of 0.52% of the total mass of the wastewater is added, and then it is sent to the defluorination tank B and defluorination tank C for further reaction, and a 30% mass concentration of liquid alkali is used to adjust the pH of the material in the defluorination tank C to 6.0~6.5, and then it is sent to the defluorination tank D and 0.1% PAM of the total mass of the wastewater is added, and then it enters the inclined plate sedimentation tank through the defluorination tank E, and the water in the defluorination tank D is taken to measure F and pH;

[0079] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0080] Example 2

[0081] The process for treating wastewater generated by the alkaline separation of rare earth ores comprises the following steps:

[0082] (1) Primary defluorination:

[0083] a1. Collected acidic wastewater (F is 510ppm, P is 283ppm) flow rate 25m 3 / h, alkaline wastewater (F is 3221ppm, P is 1312ppm) flow rate 170m 3 / h, and enter the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction, and then use hydrochloric acid with a mass concentration of 30% to adjust the pH to 8.0-9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame pump for filter pressing; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame pump for filter pressing; the filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank;

[0084] b1. Add 1.8% of the total mass of the wastewater to 1# coagulation tank A, with a concentration of 11.5% ferrous chloride, 0.9% of the total mass of the wastewater to 1# coagulation tank B, with a concentration of 22.5% lanthanum cerium chloride solution, and 1.3% of the total mass of the wastewater to 1# coagulation tank C. Stir and mix. The wastewater flows between 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles. Add 0.3% PAM of the total mass of the wastewater to the front end of 1# coagulation tank D. The mixed liquid slurry flows into the 1# radial flow sedimentation tank by gravity. Take the water at the outlet of 1# coagulation tank D to measure F, P, Ca, and pH.

[0085] c1. Separate mud and water in the 1# radial flow sedimentation tank, NTU (turbidity) is 24, which is qualified, and the supernatant directly overflows into the recovery tank.

[0086] (2) Secondary defluorination:

[0087] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0088] b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add 2.7% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 32.5% calcium chloride solution and 1.0% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 22.5%, add 0.5% PAM of the total mass of the wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water at the outlet of the 2# coagulation tank C is taken to measure the F and pH;

[0089] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 110, which is unqualified. The supernatant overflow is closed, and the sludge is pumped from the bottom into the sludge temporary storage tank, and then enters the sludge plate and frame filter press. The plate and frame filter press is used to separate the mud and water. The filtrate after filtration enters the 3# regulating tank and the sludge is transported out.

[0090] (3) Three-stage defluorination:

[0091] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 22.5% lanthanum cerium chloride solution of 0.76% of the total mass of the wastewater is added, and then it is sent to the defluorination tank B and defluorination tank C for further reaction, and a 40% mass concentration of liquid alkali is used to adjust the pH of the material in the defluorination tank C to 6.0~6.5, and the fluorine content is reduced to <1.5ppm, and then it is sent to the defluorination tank D and 0.1% PAM of the total mass of the wastewater is added, and then it enters the inclined plate sedimentation tank through the defluorination tank E, and the water in the defluorination tank D is taken to measure F and pH;

[0092] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0093] Example 3

[0094] The process for treating wastewater generated by the alkaline separation of rare earth ores comprises the following steps:

[0095] (1) Primary defluorination:

[0096] a1. Collected acidic wastewater (F is 322ppm, P is 3452ppm) flow rate 42m 3 / h, alkaline wastewater (F is 1827ppm, P is 1262ppm) flow rate 186m 3 / h respectively enter the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction, and then use hydrochloric acid with a mass concentration of 20% to adjust the pH to 8.0-9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for filter pressing; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for filter pressing. The filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank;

[0097] b1. Add 9.5% ferrous chloride solution with a mass concentration of 1.3% of the total mass of the wastewater to the 1# coagulation tank A, add 26.1% lanthanum cerium chloride solution with a mass concentration of 0.6% of the total mass of the wastewater to the 1# coagulation tank B, add 26.8% calcium chloride solution with a mass concentration of 1.0% of the total mass of the wastewater to the 1# coagulation tank C, stir and mix, the wastewater flows between the 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles, add 0.2% PAM of the total mass of the wastewater to the front end of the 1# coagulation tank D, the mixed liquid slurry flows into the 1# radial flow sedimentation tank by gravity, and the water at the outlet of the 1# coagulation tank D is measured for F, P, Ca, and pH;

[0098] c1. Mud and water separation was carried out in the 1# radial flow sedimentation tank. The NTU (turbidity) was 72, which was unqualified. The supernatant overflowed into the 2# regulating tank. The water in the 2# regulating tank entered the recycled water plate frame for plate and frame filter pressing. The filtrate entered the recycled water tank. The filter cake was slurried in the slurry tank and then transported to the 2# coagulation tank A pool by a pump.

[0099] (2) Secondary defluorination:

[0100] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0101] b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add 3.9% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 26.8% calcium chloride solution and 0.5% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 26.1% lanthanum cerium chloride solution, add 0.7% of the total mass of the wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water at the outlet of the 2# coagulation tank C is measured for F and pH;

[0102] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 105. The supernatant overflow is closed, and the sludge is pumped from the bottom into the sludge temporary storage tank, and then enters the sludge plate and frame filter press. The plate and frame filter press is used to separate the mud and water. The filtrate after filtration enters the 3# regulating tank and the sludge is transported out.

[0103] (3) Three-stage defluorination:

[0104] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 26.1% lanthanum cerium chloride solution of 0.32% of the total mass of the wastewater is added, and then it is sent to the defluorination tank B and defluorination tank C for further reaction, and a 50% mass concentration of liquid alkali is used to adjust the pH of the material in the defluorination tank C to 6.0~6.5, and then it is sent to the defluorination tank D and 0.5% PAM of the total mass of the wastewater is added, and then it enters the inclined plate sedimentation tank through the defluorination tank E, and the water in the defluorination tank D is taken to measure F and pH;

[0105] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0106] Example 4

[0107] The process for treating wastewater generated by the alkaline separation of rare earth ores comprises the following steps:

[0108] (1) Primary defluorination:

[0109] a1. Collected acidic wastewater (F is 178ppm, P is 952ppm) flow rate 10m 3 / h, alkaline wastewater (F is 941ppm, P is 828ppm) flow rate 120m 3 / h respectively enter the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction, and then use hydrochloric acid with a mass concentration of 36% to adjust the pH to 8.0-9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame pump for filter pressing; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame pump for filter pressing. The filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank;

[0110] b1. Add 0.86% of the total mass of ferrous chloride (10.8%) to the 1# coagulation tank A, add 0.5% of the total mass of lanthanum cerium chloride solution (22.8%) to the 1# coagulation tank B, add 0.94% of the total mass of 31.7% calcium chloride solution (31.7%) to the 1# coagulation tank C, stir and mix, the wastewater flows between the 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles, add 0.2% PAM of the total mass of the wastewater to the front end of the 1# coagulation tank D, the mixed liquid slurry flows into the 1# radial flow sedimentation tank by gravity, and the water at the outlet of the 1# coagulation tank D is measured for F, P, Ca, and pH;

[0111] c1. Separate mud and water in the 1# radial flow sedimentation tank, NTU (turbidity) is 45, which is qualified, and the supernatant directly overflows into the recovery pool.

[0112] (2) Secondary defluorination:

[0113] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0114] b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add 3.6% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 31.7% calcium chloride solution and 1.0% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 22.8%, add 1.5% PAM of the total mass of the wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water at the outlet of the 2# coagulation tank C is taken to measure F and pH;

[0115] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 68, and the supernatant enters the 3# regulating tank; the bottom mud is pumped into the sludge temporary storage tank, and then enters the sludge plate and frame filter press, which separates the mud and water. The filtrate after filtration enters the 3# regulating tank, and the sludge is transported out.

[0116] (3) Three-stage defluorination:

[0117] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 22.8% lanthanum cerium chloride solution of 0.95% of the total mass of the wastewater is added, and then it is sent to the defluorination tank B and defluorination tank C for further reaction, and a 20% mass concentration sodium hydroxide solution is used to adjust the pH of the material in the defluorination tank C to 6.0~6.5, and the fluorine content is reduced to <1.5ppm, and then it is sent to the defluorination tank D and 0.3% PAM of the total mass of the wastewater is added, and then it enters the inclined plate sedimentation tank through the defluorination tank E, and the water in the defluorination tank D is taken to measure F and pH;

[0118] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0119] Comparative Example 1

[0120] A process for treating wastewater generated by separating rare earth ores comprises the following steps:

[0121] (1) Primary defluorination:

[0122] a1. Collected acidic wastewater (F is 439ppm, P is 365ppm) flow rate 25m 3 / h, alkaline wastewater (F is 2808ppm, P is 1319ppm) flow rate 180m 3 / h respectively enter the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction, and then use hydrochloric acid with a mass concentration of 30% for adjustment to control the pH value at 8.0-9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for filter pressing; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for filter pressing; the filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank;

[0123] b1. Add 1.46% of the total mass of the wastewater to 1# coagulation tank A with a concentration of 11.5% ferrous chloride, and add 3.2% of the total mass of the wastewater to 1# coagulation tank C with a concentration of 31.8%. Stir and mix. The wastewater flows between 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles. Add 0.3% PAM of the total mass of the wastewater to the front end of 1# coagulation tank D. The mixed liquid slurry flows into 1# radial flow sedimentation tank by gravity. Take the water at the outlet of 1# coagulation tank D to measure F, P, Ca, and pH.

[0124] c1. Separate mud and water in the 1# radial flow sedimentation tank, NTU (turbidity) is 30, which is qualified, and the supernatant directly overflows into the recovery pool.

[0125] (2) Secondary defluorination:

[0126] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0127] b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add 3.1% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 31.8% calcium chloride solution and 0.8% of the total mass of the wastewater to the 2# coagulation tank B with a mass concentration of 24.0% lanthanum cerium chloride solution, add 0.5% of the total mass of the wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, the mixed liquid slurry flows by gravity into the 2# radial flow sedimentation tank, and the water at the outlet of the 2# coagulation tank C is taken to measure the F and pH;

[0128] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 135. The supernatant overflow is closed and the sludge is pumped into the sludge temporary storage tank from the bottom, and then enters the sludge plate and frame filter press. The plate and frame filter press is used to separate the mud and water. The filtrate after filtration enters the 3# regulating tank and the sludge is transported out.

[0129] (3) Three-stage defluorination:

[0130] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 24.0% lanthanum cerium chloride solution with a mass concentration of 0.38% of the total mass of the wastewater is added. It is then sent to the defluorination tank B and defluorination tank C for further reaction, and a 30% mass concentration alkaline solution is used to adjust the pH of the material in the defluorination tank C to 6.0~6.5. It is then sent to the defluorination tank D and 0.2% PAM with the total mass of the wastewater is added. It enters the inclined plate sedimentation tank through the defluorination tank E, and the water in the defluorination tank D is taken to measure F and pH;

[0131] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0132] Comparative Example 2

[0133] A process for treating wastewater generated by separating rare earth ores by an alkaline method comprises the following steps:

[0134] (1) Primary defluorination:

[0135] a1. Collected acidic wastewater (F is 356ppm, P is 423ppm) flow rate 25m 3 / h, alkaline wastewater (F is 3104ppm, P is 1279ppm) flow rate 175m 3 / h respectively enter the No. 1 regulating tank through the supernatant pump for acid-base neutralization reaction, and then use hydrochloric acid with a mass concentration of 30% for adjustment to control the pH value at 8.0-9.0; the precipitate in the acidic wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for filter pressing; the precipitate in the alkaline wastewater collection tank is scraped by the scraper and then enters the plate-frame through the plate-frame pump for filter pressing; the filter cake is received by the hopper and transported to the workshop for recycling, and the filtrate enters the No. 1 regulating tank;

[0136] b1. Add 1.52% of the total mass of the wastewater to 1# coagulation tank A with a concentration of 11.5%, and add 3.4% of the total mass of the wastewater to 1# coagulation tank C with a concentration of 31.8%. Stir and mix. The wastewater flows between 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles. Add 0.3% of the total mass of the wastewater to the front end of 1# coagulation tank D with PAM. The mixed liquid slurry flows into 1# radial flow sedimentation tank by gravity. Take the water at the outlet of 1# coagulation tank D to measure F, P, Ca, and pH.

[0137] c1. Mud and water separation was carried out in the 1# radial flow sedimentation tank, NTU (turbidity) was 32, which was qualified, and the supernatant directly overflowed into the recovery pool.

[0138] (2) Secondary defluorination:

[0139] a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank;

[0140] b2. Add 31.8% calcium chloride solution of 3.7% of the total mass of wastewater to the 2# coagulation tank B, adjust the pH of the 2# coagulation tank B to 7.0-7.5 with 30% liquid caustic soda, add 0.5% PAM of the total mass of wastewater to the 2# coagulation tank C, stir and mix, the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity, and the water at the outlet of the 2# coagulation tank C is taken to measure F and pH;

[0141] c2. The NTU (turbidity) at the outlet of the 2# radial flow sedimentation tank is 118. The supernatant overflow is closed and the sludge is pumped into the sludge temporary storage tank from the bottom, and then enters the sludge plate and frame filter press. The plate and frame filter press is used to separate the mud and water. The filtrate after filtration enters the 3# regulating tank and the sludge is transported out.

[0142] (3) Three-stage defluorination:

[0143] a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and a 10.2% polyaluminum solution of 0.69% of the total mass of the wastewater is added, and then it is sent to the defluorination tank B and defluorination tank C for further reaction, and a 30% alkaline solution is used to adjust the pH of the material in the defluorination tank C to 7.0, and then it is sent to the defluorination tank D and 0.2% PAM of the total mass of the wastewater is added, and then it enters the inclined plate sedimentation tank through the defluorination tank E, and the water in the defluorination tank D is taken to measure F and pH;

[0144] b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external discharge tank, and the mud is pumped into the external drainage plate frame. The filtrate after filtration enters the external discharge tank and then discharged to the sewage treatment plant. The mud residue enters the pulping tank and is then pumped to the 2# coagulation tank A in the secondary defluorination.

[0145] The sewage treatment indicators of the primary defluorination, secondary defluorination and tertiary defluorination in the above embodiments and comparative examples were tested for F by a water quality F ion meter, tested for P by an inductively coupled plasma mass spectrometer (ICP-MS), tested for pH by a pH meter, and tested for calcium Ca by an atomic absorption spectrometer. The test results are shown in Table 1.

[0146] Table 1 Test results

[0147]

[0148] It can be seen from the above table that when the comparative example 1 adopts the wastewater index to be treated with the same difference as that of the embodiment 2, in the primary defluorination process, no lanthanum cerium chloride solution is added, ferrous chloride is used for dephosphorization first, and then calcium chloride is used for defluorination and dephosphorization, the addition amount of ferrous chloride and calcium chloride is significantly increased, and the Ca index detection at the water outlet reaches 78ppm. The increase in calcium ion concentration leads to an increase in the unit consumption of production alkali when the water is reused for production, and at the same time causes part of the calcium ions to enter the rare earth feed liquid, increasing the difficulty of decalcifying the rare earth feed liquid in the later stage, and causing the reuse water pipeline to be blocked, and scaling on the surface of the heating coil reduces the heat utilization efficiency. In addition, the cost of water treatment agents also increases simultaneously.

[0149] In the case where the wastewater index to be treated in Comparative Example 2 is less different from that in Example 2, in the primary, secondary and tertiary defluorination processes, lanthanum chloride cerium solution is not used, ferrous chloride and calcium chloride are added to the primary, calcium chloride is only added to the secondary, and polyaluminum is added to the tertiary. During the treatment process, when the primary and secondary indicators reach the same, the usage of ferrous chloride and calcium chloride is greatly increased, and the calcium at the primary outlet reaches 83ppm. The increase in calcium ion concentration causes the water to be reused in production, and the production alkali unit consumption increases, and at the same time, some calcium ions enter the rare earth feed liquid, increasing the difficulty of decalcification of the rare earth feed liquid in the later period, and at the same time, the recycled water pipeline is blocked, and the scaling on the surface of the heating coil reduces the heat use efficiency. In addition, the cost of the water treatment agent also increases synchronously. The calcium at the secondary outlet reaches 2347ppm. In order to achieve the same treatment result, calcium chloride is added to increase, and some calcium ions cannot be effectively utilized and discharged with the wastewater. Polyaluminum was added during the tertiary defluorination process. After treatment, the F content was 1.8ppm and the P content was 0.4ppm. According to the existing technology, polyaluminum can remove P from wastewater, but it is difficult to reduce P to below 1ppm. The production data can verify this conclusion: when the polyaluminum P concentration is low, it is difficult for polyaluminum to further reduce P. In addition, the F ion concentration of the water after the tertiary defluorination slowly increases during the static state in the external discharge pool, and some F ions are released back into the water body.

[0150] In the production process, lanthanum cerium chloride replaces part of ferrous chloride and calcium chloride as a defluorination and dephosphorization agent, which reduces the amount of agent used to a certain extent and further reduces sludge residue; at the same time, because lanthanum cerium chloride is a by-product of the company, it can save a lot of wastewater treatment costs. Other defluorination and dephosphorization agents can also be used in primary defluorination and dephosphorization, secondary defluorination, and tertiary defluorination. However, in order to achieve the same treatment index, it is necessary to increase the amount of agent input and produce a lot of sludge. Especially when deeply treating F in wastewater, it is difficult to reach an index below 1.0ppm, and the water quality after treatment will also have problems such as increased F ion concentration.

Claims

1. A process for treating wastewater generated by alkaline separation of rare earth ores, characterized in that: The following steps are involved: (1) Primary defluorination: a1. The collected acidic wastewater and alkaline wastewater enter the 1# regulating tank through the supernatant pump respectively for acid-base neutralization reaction, and the reaction pH is controlled to be 8.0~9.0; the main pollutants F in the acidic wastewater are 100~1000ppm, P is 100~4000ppm, and the main pollutants F in the alkaline wastewater are 500~4000ppm, P is 500~2000ppm; b1. Add ferrous chloride to the 1# coagulation tank A, add lanthanum cerium chloride to the 1# coagulation tank B, add calcium chloride to the 1# coagulation tank C, stir and mix, the wastewater flows between the 1# coagulation tank A, 1# coagulation tank B, and 1# coagulation tank C in the form of baffles, add polyacrylamide to the front end of the 1# coagulation tank D, and the mixed liquid slurry flows into the 1# radial flow sedimentation tank by gravity; c1. Separate mud and water in the 1# radial flow sedimentation tank, and the supernatant with NTU < 60 will overflow directly into the recovery tank; After the first-stage defluorination, the index control F < 200ppm, P < 200ppm; (2) Secondary defluorination: a2. The sludge in the 1# radial flow sedimentation tank enters the 2# coagulation tank A tank; b2. Use the alkaline wastewater in a1 to adjust the pH of the 2# coagulation tank A to 8.0~9.0, add calcium chloride and lanthanum cerium chloride to the 2# coagulation tank B, add polyacrylamide to the 2# coagulation tank C, stir and mix, and the wastewater flows between the 2# coagulation tank A, 2# coagulation tank B, and 2# coagulation tank C in the form of baffles, and the mixed liquid slurry flows into the 2# radial flow sedimentation tank by gravity; c2. NTU 0~100 at the outlet of 2# radial flow sedimentation tank, and the supernatant enters 3# regulating tank; After the second-stage defluorination, the index control F < 20ppm, P < 1ppm; (3) Three-stage defluorination: a3. The wastewater from the 3# regulating tank is sent to the defluorination tank A, and lanthanum cerium chloride is added, and then sent to the defluorination tank B and defluorination tank C for further reaction, and the pH of the material in the defluorination tank C is adjusted to 6.0~6.5, and then sent to the defluorination tank D and polyacrylamide is added, and then enters the inclined plate sedimentation tank through the defluorination tank E; b3. The supernatant of the inclined plate sedimentation tank overflows directly to the external drainage tank, the mud is pumped into the external drainage plate frame, the filtrate after filtration enters the external drainage tank, and then discharged to the sewage treatment plant, the mud residue enters the pulping tank and then pumped to the 2# coagulation tank A in the secondary defluorination; After the third-stage defluorination, the index is controlled to be F<1.5ppm.

2. The process for treating wastewater generated by alkaline separation of rare earth ores according to claim 1, characterized in that: In step a1, the pH is adjusted by hydrochloric acid, and the mass concentration of hydrochloric acid is 20% to 36%.

3. The process for treating wastewater generated by alkaline separation of rare earth ores according to claim 1, characterized in that: In step b1, the amount of ferrous chloride added is 0.5%~2.5% of the total mass of the wastewater, the amount of lanthanum cerium chloride added is 0.5%~1.5% of the total mass of the wastewater, the amount of calcium chloride added is 0.5%~3.5% of the total mass of the wastewater, and the amount of polyacrylamide added is 0.2%~1.0% of the total mass of the wastewater.

4. The process for treating wastewater generated by separation of rare earth ores by alkaline method according to claim 1, characterized in that: In step b2, the amount of lanthanum cerium chloride added is 0.5% to 1.0% of the total mass of the wastewater, the amount of calcium chloride added is 2.5% to 4.0% of the total mass of the wastewater, and the amount of polyacrylamide added is 0.5% to 1.5% of the total mass of the wastewater.

5. The process for treating wastewater generated by alkaline separation of rare earth ores according to claim 1, characterized in that: In step a3, the amount of lanthanum cerium chloride added is 0.17% to 1.0% of the total mass of the wastewater, and the amount of polyacrylamide added is 0.1% to 0.5% of the total mass of the wastewater.

6. The process for treating wastewater generated by alkaline separation of rare earth ores according to claim 1, characterized in that: Step a3: The solution having a pH of 6.0-6.5 is an alkaline solution.

7. The process for treating wastewater generated by separation of rare earth ores by alkaline method according to claim 1, characterized in that: The calcium chloride is added in the form of a calcium chloride solution having a mass concentration of 25% to 33%, and the ferrous chloride is added in the form of a ferrous chloride solution having a mass concentration of 8% to 13%.

8. The process for treating wastewater generated by alkaline separation of rare earth ores according to claim 1, characterized in that: The lanthanum cerium chloride is added in the form of a lanthanum cerium chloride solution with a mass concentration of 20% to 27%.

9. The process for treating wastewater generated by separation of rare earth ores by alkaline method according to claim 1, characterized in that: Step c1NTU≥60, the supernatant overflows into the 2# regulating tank, the water in the 2# regulating tank enters the recycled water plate frame for plate and frame filtration, the filtrate enters the recycled water tank, the filter cake is slurried in the slurry tank and then transported to the 2# coagulation tank A pool by a pump.

10. The process for treating wastewater generated by separation of rare earth ores by alkaline method according to claim 1, characterized in that: In step c2, NTU>100, the supernatant overflow is closed, and the sludge is pumped from the bottom into the sludge temporary storage tank, and then enters the sludge plate and frame filter press.

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