Preparation method of rare earth composite fluorine removal agent, rare earth composite fluorine removal agent and application of rare earth composite fluorine removal agent

Abstract

The invention discloses a preparation method of a rare earth composite fluorine removal agent, the rare earth composite fluorine removal agent and application. The preparation method of the rare earth composite fluorine removal agent comprises the following steps that S1, a heavy metal capturing agent is added into rare earth slag raffinate for metal impurity adsorption treatment, the heavy metal capturing agent is removed after adsorption treatment, and intermediate treatment liquid is obtained; s2, preheating the intermediate treatment liquid to obtain a preheated material; s3, evaporating and concentrating the preheated material to obtain a concentrated solution; and S4, cooling and crystallizing to obtain the rare earth composite fluorine removal agent. According to the process for preparing the rare earth composite fluorine removal agent for water treatment through resourceful treatment on the rare earth raffinate and the fluorine removal agent product prepared by the process, the efficient fluorine removal agent is prepared from cheap and easily available raw materials.

Description

Technical Field

[0001] The invention relates to the technical field of industrial fluorine-containing wastewater treatment, and in particular to a preparation method of a rare earth composite defluorinating agent, the rare earth composite defluorinating agent and application thereof. Background Art

[0002] In recent years, the discharge volume of industrial fluoride-containing wastewater is large and the fluoride content is high, which seriously threatens the living environment and human health, and therefore has received close attention from the society. Fluoride pollution has received more and more attention from people, and how to deal with fluoride in wastewater has always been an important topic in the field of environmental protection at home and abroad. In recent years, a lot of work has been done at home and abroad in the treatment of fluoride-containing wastewater, and great progress has been made in the theoretical knowledge, methods and technologies of fluoride removal. At present, the composition of fluoride-containing industrial wastewater treated at home and abroad is complex and diverse, and there are many treatment methods, such as precipitation and adsorption, as well as ion exchange resin method, reverse osmosis method, electrocoagulation method, electrodialysis method, etc.

[0003] In the actual defluorination process of the factory, the defluorination efficiency and economy are comprehensively considered according to different environments and defluorination requirements, so as to determine the treatment method and process of fluorine-containing wastewater, which has both good defluorination effect and good economy, so as to achieve the purpose of treating fluorine-containing wastewater and resource utilization.

[0004] Therefore, how to use cheap and readily available raw materials to produce efficient defluorination agents has become a technical challenge. Summary of the invention

[0005] In view of the limitations of the above-mentioned prior art, the present invention provides a preparation method of a rare earth composite defluorinating agent, a rare earth composite defluorinating agent and an application thereof. The present invention uses a process for preparing a rare earth composite defluorinating agent for water treatment by resource treatment of rare earth raffinate and a defluorinating agent product prepared thereby, thereby realizing the use of cheap and readily available raw materials to produce an efficient defluorinating agent.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention is to provide a method for preparing a rare earth composite defluorinating agent, comprising the following steps:

[0008] S1: adding a heavy metal capture agent to the rare earth slag raffinate to perform metal impurity adsorption treatment, and removing the heavy metal capture agent after the adsorption treatment to obtain an intermediate treatment liquid;

[0009] S2: preheating the intermediate treatment liquid to obtain a preheated material;

[0010] S3: evaporating and concentrating the preheated material to obtain a concentrated solution;

[0011] S4: Cooling and crystallization to obtain a rare earth composite defluorinating agent.

[0012] As a preferred implementation, step S1:

[0013] The rare earth slag raffinate contains at least Al, Ti, Fe, Pb, Cr, As, Cd or Hg elements; preferably, the rare earth slag raffinate contains aluminum, calculated as aluminum oxide, and the mass content of aluminum oxide is 4% to 6%;

[0014] More preferably,

[0015] The preparation steps of the rare earth slag raffinate are: dissolving the rare earth slag with acid once to obtain a primary acid solution, and performing organic extraction on the primary acid solution to obtain the rare earth slag raffinate.

[0016] More preferably,

[0017] The acid solution added in the first acid dissolution is a sulfuric acid solution; more preferably, the mass concentration of the sulfuric acid solution is 50%;

[0018] The organic solvent added in the organic extraction is an amine extractant; preferably, the organic solvent is at least one of N1923, N263 or N235; the extraction ratio is 1:1 to 3:1, and the extraction operation temperature is 30°C to 50°C.

[0019] As a preferred implementation, step S1:

[0020] Add a heavy metal capture agent to the rare earth slag raffinate and place it at 20-50° C. for adsorption for 50-80 minutes; filter and remove the heavy metal capture agent to obtain the intermediate treatment liquid;

[0021] Preferably, after static adsorption, an auxiliary agent solution is added and microbubbles are introduced for 20-30 minutes, and then the heavy metal capture agent is removed by filtration to obtain the intermediate treatment solution;

[0022] More preferably,

[0023] The mass ratio of the rare earth slag raffinate to the heavy metal capture agent is 1 ton of rare earth slag raffinate: 1-3 g of heavy metal capture agent; and / or,

[0024] The auxiliary agent is selected from polyacrylamine hydrochloride; and / or,

[0025] The concentration of the auxiliary agent solution is 0.2-1wt%; and / or,

[0026] The particle size of the microbubbles is 300-600 nm; and / or,

[0027] The mass ratio of the auxiliary agent to the heavy metal capture agent is 1:5-10; and / or,

[0028] The ventilation volume of the microbubbles is 5L / (m2 ·h)~10L / (m 2 h).

[0029] The present invention unexpectedly discovered that under the action of microbubbles, after adding an auxiliary agent, it can synergize with the heavy metal capture agent to improve the absorption effect of heavy metal ions, which is helpful to improve the performance of the prepared heavy rare earth composite defluorination agent.

[0030] As a preferred implementation, step S1:

[0031] The heavy metal scavenger is graphene oxide grafted with modified phosphorus-containing groups; preferably,

[0032] The preparation method of the heavy metal capture agent comprises the following steps:

[0033] (1) Raw material mixing: dispersing graphite oxide in a phosphorous acid solution to obtain a graphite oxide dispersion;

[0034] (2) Ultrasonic exfoliation: ultrasonically treating the graphite oxide dispersion to obtain a graphene oxide suspension;

[0035] (3) adding a catalyst: adding a catalyst to the graphene oxide suspension, dispersing the mixture by ultrasonication again, and vacuum drying to obtain a mixture of graphene oxide and phosphorus trichloride;

[0036] (4) Preparation of heavy metal scavenger: Under a protective atmosphere, a mixture of the graphene oxide and phosphorus trichloride is subjected to high temperature heat treatment to obtain the heavy metal scavenger.

[0037] The heavy metal scavenger of the present invention has specific functional groups through grafting modification, has high selectivity for heavy metal ions, and can remove heavy metal ion pollutants in a targeted manner. The preparation process of the heavy metal scavenger of the present invention is as follows: the carboxyl group on the surface of graphene oxide can react with phosphorous acid under the catalytic action of phosphorus trichloride, the double bond of the carboxyl group is opened, and the phosphorus-containing group is grafted thereon. The phosphorus-containing group of the modified graphene oxide fixes the heavy metal ions, and filtering the solid scavenger can achieve the effect of removing heavy metals.

[0038] As a preferred embodiment, step (1),

[0039] The mass volume ratio of graphite oxide to phosphorous acid solution is 1-5 mg:1; and / or,

[0040] The mass concentration of the phosphorous acid solution is 10% to 50%; and / or,

[0041] Step (2),

[0042] The ultrasonic treatment time is 10 min to 60 min; and / or,

[0043] The power of ultrasonic treatment is 100w~1000w.

[0044] As a preferred embodiment, step (3),

[0045] The catalyst is phosphorus trichloride; and / or,

[0046] The mass ratio of the catalyst to the graphite oxide is 1 to 5:1; and / or,

[0047] The time for the second ultrasonic dispersion is 10 min to 60 min; and / or,

[0048] The power of the second ultrasonic treatment is 100w to 1000w; and / or,

[0049] The vacuum drying temperature is 50-80°C; and / or,

[0050] Step (4),

[0051] The temperature of the high temperature heat treatment is 700°C to 900°C; and / or,

[0052] The high temperature heat treatment time is 30 to 60 minutes; and / or,

[0053] The protective atmosphere is nitrogen.

[0054] As a preferred implementation, step S2:

[0055] The intermediate treatment liquid is preheated in sequence by a tail gas preheater, a second-effect condensate preheater, and a first-effect condensate preheater to obtain a preheated material, wherein the temperature of the preheated material is 40 to 60° C.;

[0056] Preferably,

[0057] The exhaust gas temperature in the exhaust gas preheater is 40 to 60°C; and / or,

[0058] The temperature of the heat exchange medium in the second-effect condensate preheater is 90-100°C; and / or,

[0059] The temperature of the heat exchange medium in the first-effect condensate preheater is 130-140°C.

[0060] The present invention fully utilizes the heat of high-temperature condensed water through the above-mentioned heat exchange method, which is beneficial to resource conservation.

[0061] As a preferred embodiment, step S3: evaporating and concentrating the preheated material through a double-effect evaporator and a single-effect evaporator to obtain a concentrated solution; preferably,

[0062] The temperature of the second-effect evaporator is 90-100°C; and / or,

[0063] The pressure of the second-effect evaporator is 0.1-0.3MPa; and / or,

[0064] The evaporation time of the second-effect evaporator is 0.1 to 1 hour; and / or,

[0065] The temperature of the single-effect evaporator is 100-110°C; and / or,

[0066] The pressure of the single-effect evaporator is 0.2-0.5 MPa; and / or,

[0067] The single-effect evaporator has a single-effect evaporation time of 0.1 to 1 hour; and / or,

[0068] In the present invention, both the double-effect evaporator and the single-effect evaporator adopt graphite evaporator for evaporation and concentration; the graphite evaporator adopts steam heating. Generally, it is more appropriate to select a round block hole type graphite evaporator. The round block hole type graphite evaporator is composed of a graphite air cavity, graphite upper and lower heads, a graphite heat exchange block, a carbon steel shell, and a pressure spring. The graphite heat exchange block is drilled with horizontal holes and vertical holes, which are not connected. The vertical holes carry corrosive materials and the horizontal holes carry steam. The two graphite heat exchange blocks are sealed with a polytetrafluoroethylene seal. Compared with the prior art using graphite materials, it solves the problems of pipeline corrosion and easy blockage in the actual production process.

[0069] In addition, the present invention finds that setting up a two-stage evaporation process is helpful to improve the performance of the prepared heavy rare earth composite defluorinating agent.

[0070] S4: cooling and crystallizing through a flake forming machine to obtain a rare earth composite defluorination agent;

[0071] Preferably,

[0072] The cooling crystallization temperature is 70-80°C; and / or the rotation speed of the flaker is 10-20r / min.

[0073] The above crystallization step adopts a large drum structure, and the silo adopts a polytetrafluoroethylene lining, which is more corrosion-resistant and has a longer service life than traditional carbon steel materials.

[0074] The second aspect of the present invention is to provide a rare earth composite defluorinator prepared by the preparation method of the rare earth composite defluorinator described in the first aspect of the present invention, wherein the components of the rare earth composite defluorinator include hydrated aluminum sulfate, aluminum chloride and rare earth oxides; wherein the aluminum content, calculated as alumina, is 8% to 20% by mass of alumina; the mass content of rare earth elements is 0.1% to 5%; preferably, the mass content of alumina is 10% to 16%; further preferably, the mass content of alumina is 12.5% ​​to 16%; further preferably, the mass content of alumina is 14% to 16%.

[0075] In the rare earth composite defluorinating agent, the mass content of rare earth elements is 0.6% to 2%; preferably, the mass content of rare earth elements is 0.9% to 2%; more preferably, the mass content of rare earth elements is 1.6% to 2%.

[0076] The rare earth composite defluoridation agent of the present invention not only has a high concentration of aluminum sulfate for defluoridation, but also has an appropriate amount of rare earth elements. Rare earth oxides form colloids in water and adsorb fluoride ions. In addition, rare earth and fluorine form insoluble compounds, such as LaF 3 , thereby removing fluorine from the water; therefore, the rare earth element of the present invention also improves the defluorination effect to a certain extent.

[0077] The third aspect of the present invention is to provide the use of the rare earth composite defluorinating agent described in the second aspect of the present invention in defluorination.

[0078] Compared with the prior art, the present invention has at least the following advantages:

[0079] (1) The present invention provides a process for preparing a rare earth composite defluorinating agent for water treatment by resource treatment of rare earth raffinate, and the defluorinating agent product prepared thereby. The process of the present invention is a continuous process with a high degree of automation, which is conducive to operation; the process of the present invention includes a mature evaporation and concentration process, and the equipment operates stably and reliably; the heater used in the process of the present invention is not easy to scale or clog, and the heater can be made of graphite, which saves costs; the process of the present invention requires less auxiliary equipment, the device is compact, the floor space is small, the temperature difference loss is small, and it is highly efficient and energy-saving.

[0080] (2) The defluorination agent prepared by the process of the present invention has a lower dosage and produces less mud. Compared with conventional commercial defluorination agents and PAC, the dosage is reduced by 10% to 20%, and the mud volume is reduced by 15% to 25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 The present invention is a process flow chart of the method for preparing the rare earth composite defluorinating agent. DETAILED DESCRIPTION

[0082] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0083] Preparation Example 1

[0084] The heavy metal scavenger of the present invention is graphene oxide grafted with modified phosphorus-containing groups; the preparation method thereof comprises the following steps:

[0085] (1) Mixing raw materials: dispersing graphite oxide in a phosphorous acid solution, wherein the mass volume ratio of graphite oxide to phosphorous acid solution is 100 mg:50 ml; and the mass concentration of the phosphorous acid solution is 10%; thereby obtaining a graphite oxide dispersion;

[0086] (2) Ultrasonic exfoliation: ultrasonically treating the graphene oxide dispersion for 10 min at a power of 100 W to obtain a graphene oxide suspension;

[0087] (3) adding a catalyst: adding phosphorus trichloride as a catalyst to the graphene oxide suspension, wherein the mass ratio of phosphorus trichloride to graphite oxide is 1:1; performing ultrasonic dispersion again, wherein the time for the ultrasonic dispersion again is 10 min; the power is 100 W; and vacuum drying is performed at a temperature of 50° C.; thereby obtaining a mixture of graphene oxide and phosphorus trichloride;

[0088] (4) Preparation of heavy metal scavenger: The mixture of the graphene oxide and phosphorus trichloride was subjected to high temperature heat treatment under nitrogen, the temperature of the high temperature heat treatment was 700° C., and the time was 30 min; the heavy metal scavenger was obtained.

[0089] Preparation Example 2

[0090] The heavy metal scavenger of the present invention is graphene oxide grafted with modified phosphorus-containing groups; the preparation method thereof comprises the following steps:

[0091] (1) Mixing raw materials: dispersing graphite oxide in a phosphorous acid solution, wherein the mass volume ratio of graphite oxide to phosphorous acid solution is 100 mg:50 ml; and the mass concentration of the phosphorous acid solution is 30%; and obtaining a graphite oxide dispersion;

[0092] (2) Ultrasonic exfoliation: ultrasonically treating the graphene oxide dispersion for 30 min at a power of 500 W to obtain a graphene oxide suspension;

[0093] (3) adding a catalyst: adding a catalyst phosphorus trichloride to the graphene oxide suspension, wherein the mass ratio of phosphorus trichloride to graphite oxide is 3:1; performing ultrasonic dispersion again, wherein the time for the ultrasonic dispersion again is 30 min; the power is 500 W; and vacuum drying is performed at a temperature of 60° C. to obtain a mixture of graphene oxide and phosphorus trichloride;

[0094] (4) Preparation of heavy metal scavenger: The mixture of the graphene oxide and phosphorus trichloride was subjected to high temperature heat treatment under nitrogen, the temperature of the high temperature heat treatment was 800° C., and the time was 40 min; thereby obtaining the heavy metal scavenger.

[0095] Preparation Example 3

[0096] The heavy metal scavenger of the present invention is graphene oxide grafted with modified phosphorus-containing groups; the preparation method thereof comprises the following steps:

[0097] (1) Mixing raw materials: dispersing graphite oxide in a phosphorous acid solution, wherein the mass volume ratio of graphite oxide to phosphorous acid solution is 100 mg:50 ml; and the mass concentration of phosphorous acid solution is 50%; and obtaining a graphite oxide dispersion;

[0098] (2) Ultrasonic exfoliation: ultrasonically treating the graphene oxide dispersion for 60 min at a power of 1000 W to obtain a graphene oxide suspension;

[0099] (3) adding a catalyst: adding phosphorus trichloride as a catalyst to the graphene oxide suspension, wherein the mass ratio of phosphorus trichloride to graphite oxide is 5:1; performing ultrasonic dispersion again, wherein the time for the ultrasonic dispersion again is 60 min; the power is 1000 W; and vacuum drying is performed at a temperature of 80° C. to obtain a mixture of graphene oxide and phosphorus trichloride;

[0100] (4) Preparation of heavy metal scavenger: The mixture of the graphene oxide and phosphorus trichloride was subjected to high temperature heat treatment under nitrogen, the temperature of the high temperature heat treatment was 900° C., and the time was 60 min; the heavy metal scavenger was obtained.

[0101] Example 1

[0102] The heavy metal scavenger prepared in Preparation Example 1 is used to prepare a rare earth composite defluorinating agent. The preparation method of the rare earth composite defluorinating agent is as follows: Figure 1 As shown, the following steps are included:

[0103] S1: Acid dissolution of rare earth slag is performed once, wherein the acid solution added for the acid dissolution is a sulfuric acid solution with a mass concentration of 50%; the acid dissolution temperature is 25°C, and the acid dissolution time is 60 min; a primary acid solution is obtained, and organic extraction is performed on the primary acid solution, wherein the organic solvent added for the organic extraction is N1923; the extraction phase ratio is 1:1, and the extraction operation temperature is 30°C; the rare earth slag raffinate is obtained, and the rare earth slag raffinate includes at least heavy metal elements such as Al, Ti, Fe, Pb, Cr, As, Cd and Hg; the heavy metal content of the rare earth slag raffinate is as shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] Add a heavy metal capture agent to the rare earth slag raffinate and place it at 20°C for 70 minutes for metal impurity adsorption treatment, the mass ratio of the rare earth slag raffinate to the heavy metal capture agent is 1 ton of rare earth slag raffinate: 1 g of heavy metal capture agent; remove the heavy metal capture agent after the adsorption treatment to obtain an intermediate treatment liquid;

[0108] S2: The intermediate treatment liquid is preheated in turn through a tail gas preheater, a second effect condensate preheater, and a first effect condensate preheater to obtain a preheated material; wherein, the tail gas temperature in the tail gas preheater is 40°C; the temperature of the heat exchange medium (water) in the second effect condensate preheater is 90°C; the temperature of the heat exchange medium (water) in the first effect condensate preheater is 130°C; the temperature of the preheated material is 41°C; after the above preheating, the heat of the high-temperature condensate water can be fully utilized, and resources can be utilized.

[0109] S3: Evaporating and concentrating the preheated material through a two-effect evaporator and a single-effect evaporator (both the two-effect evaporator and the single-effect evaporator are existing graphite evaporators) to obtain a concentrated solution; performing evaporation and concentration;

[0110] Among them, the temperature of the second-effect evaporator is 90℃; the pressure of the second-effect evaporator is 0.1MPa; the evaporation time of the second-effect evaporator is 0.1h; the temperature of the single-effect evaporator is 100℃; the pressure of the single-effect evaporator is 0.2MPa; the single-effect evaporation time of the single-effect evaporator is 0.1h;

[0111] S4: Cooling and crystallizing by a flake machine; the temperature of cooling and crystallizing is 75°C; the speed of the flake machine is 13r / min, and a rare earth composite defluorinating agent is obtained. The above crystallization step uses a large-scale drum-type flake machine, and the silo is lined with polytetrafluoroethylene material, which is more corrosion-resistant and has a longer service life than traditional carbon steel materials.

[0112] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0113] Example 2

[0114] It adopts a method basically the same as that of Example 1, the only difference being that it uses the heavy metal capture agent prepared in Preparation Example 2.

[0115] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0116] Example 3

[0117] It adopts a method basically the same as that of Example 1, the only difference being that it uses the heavy metal capture agent prepared in Preparation Example 3.

[0118] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0119] Example 4

[0120] The method is basically the same as that of Example 1, except that, step S1: adding a heavy metal capture agent to the rare earth slag raffinate and standing for adsorption at 20°C for 50 minutes to perform metal impurity adsorption treatment, adding a solution of auxiliary agent polyacrylamine hydrochloride (concentration of 0.7wt%) and passing microbubbles for 20 minutes, wherein the mass ratio of the auxiliary agent to the heavy metal capture agent is 1:8; the microbubbles are prepared by passing air and water through an existing microbubble device, and the particle size of the microbubbles is 300-600nm; the ventilation volume of the microbubbles is 7L / (m 2 h); finally filtering to remove the heavy metal capture agent to obtain the intermediate treatment liquid.

[0121] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0122] Example 5

[0123] The method is basically the same as that of Example 1, except that, step S1: adding a heavy metal capture agent to the rare earth slag raffinate and standing for adsorption at 20°C for 55 minutes to perform metal impurity adsorption treatment, adding a solution of polyacrylamine hydrochloride (concentration of 0.4wt%) as an auxiliary agent and passing microbubbles for treatment for 25 minutes, wherein the mass ratio of the auxiliary agent to the heavy metal capture agent is 1:6; the microbubbles are prepared by passing air and water through an existing microbubble device, and the particle size of the microbubbles is 300-600nm; the ventilation volume of the microbubbles is 5L / (m 2 h); finally filtering to remove the heavy metal capture agent to obtain the intermediate treatment liquid.

[0124] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0125] Example 6

[0126] The heavy metal scavenger prepared in Preparation Example 3 is used to prepare a rare earth composite defluorinating agent. The preparation method of the rare earth composite defluorinating agent comprises the following steps:

[0127] S1: The same rare earth slag extract as in Example 1 is used; a heavy metal capture agent is added to the rare earth slag extract and the solution is allowed to stand at 35°C for 65 minutes for metal impurity adsorption treatment; the mass ratio of the rare earth slag extract to the heavy metal capture agent is 1 ton of rare earth slag extract: 3g of heavy metal capture agent; then a solution of auxiliary agent polyacrylamine hydrochloride (concentration of 0.6wt%) is added and microbubbles are passed through for 20 minutes, wherein the mass ratio of the auxiliary agent to the heavy metal capture agent is 1:7; the microbubbles are prepared by passing air and water through an existing microbubble device, and the particle size of the microbubbles is 300-600nm; the ventilation volume of the microbubbles is 6L / (m 2 h); finally filtering to remove the heavy metal capture agent to obtain the intermediate treatment liquid.

[0128] Add heavy metal capture agent to the rare earth slag raffinate and place it at 20°C for 50-80 minutes for metal impurity adsorption to obtain an intermediate treatment liquid;

[0129] S2: The intermediate treatment liquid is preheated in turn through a tail gas preheater, a second effect condensate preheater, and a first effect condensate preheater to obtain a preheated material; wherein, the tail gas temperature in the tail gas preheater is 45°C; the temperature of the heat exchange medium in the second effect condensate preheater is 95°C; the temperature of the heat exchange medium in the first effect condensate preheater is 135°C; the temperature of the preheated material is 45°C; after the above preheating, the heat of the high-temperature condensate water can be fully utilized, and resources can be utilized.

[0130] S3: Evaporating and concentrating the preheated material through a two-effect evaporator and a single-effect evaporator (both the two-effect evaporator and the single-effect evaporator are existing graphite evaporators) to obtain a concentrated solution; performing evaporation and concentration;

[0131] Among them, the temperature of the second-effect evaporator is 95℃; the pressure of the second-effect evaporator is 0.2MPa; the evaporation time of the second-effect evaporator is 1h; the temperature of the single-effect evaporator is 110℃; the pressure of the single-effect evaporator is 0.3MPa; the single-effect evaporation time of the single-effect evaporator is 1h;

[0132] S4: Cooling and crystallizing through a flake machine; the temperature of cooling and crystallizing is 80℃; the speed of the flake machine is 15r / min, and a rare earth composite defluoridation agent is obtained. The above crystallization step uses a large-scale drum-type flake machine, and the silo is made of PTFE material, which is more corrosion-resistant and has a longer service life than traditional carbon steel materials.

[0133] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0134] Comparative Example 1

[0135] The method is basically the same as that of Example 1, except that no heavy metal capture agent is added.

[0136] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0137] Comparative Example 2

[0138] The method is basically the same as that of Example 1, except that the evaporation and concentration conditions of the first-effect evaporator are adjusted to be the same as those of the second-effect evaporator.

[0139] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0140] Comparative Example 3

[0141] The method is basically the same as that of Example 1, except that the evaporation and concentration conditions of the second-effect evaporator are adjusted to be the same as those of the first-effect evaporator.

[0142] The rare earth composite defluoridating agent prepared by the above method mainly comprises hydrated aluminum sulfate, aluminum chloride and rare earth oxides, wherein the aluminum content, calculated as aluminum oxide, is shown in Table 2.

[0143] Comparative Example 4

[0144] The method is basically the same as that of Example 4, except that only microbubbles are introduced without adding an auxiliary agent.

[0145] The rare earth composite defluoridating agent prepared by the above method mainly includes aluminum sulfate hydrate, aluminum chloride hydrate and rare earth oxides, and the specific contents are shown in Table 2.

[0146] Comparative Example 5

[0147] The method is basically the same as that of Example 4, except that no microbubbles are introduced and only an auxiliary agent is added.

[0148] The rare earth composite defluoridating agent prepared by the above method mainly includes aluminum sulfate hydrate, aluminum chloride hydrate and rare earth oxides, and the specific contents are shown in Table 2.

[0149] The main components of the defluorination agents prepared in the above examples and comparative examples are shown in Table 2.

[0150] Table 2

[0151]

[0152]

[0153] Test method: The defluorination rate of the defluoridation agents of the embodiments and comparative examples was tested for fluoride-containing water of different concentrations. The test method was based on HJ 488-2009 "Determination of fluoride in water - Fluorine reagent spectrophotometry".

[0154] Application Examples 1-6

[0155] Since the pH of fluoride-containing wastewater is 6, there is no need to adjust the pH. - The concentration was about 20 mg / L. 1 mL of the rare earth defluoridation agent of Examples 1-6 was added respectively, stirred for 5 min, allowed to stand for 5 min, and the supernatant F was detected. - Concentration. Wet sludge is obtained after filtration and weighed after drying.

[0156] Application Comparative Examples 1-5

[0157] Since the pH of fluoride-containing wastewater is 6, there is no need to adjust the pH. - 1 mL of the rare earth defluoridation agent of Comparative Examples 1-5 was added to the mixture (concentration of about 20 mg / L), stirred for 5 min, allowed to stand for 5 min, and the supernatant F was detected. - Concentration. Wet sludge is obtained after filtration and weighed after drying.

[0158] Application Comparative Example 6

[0159] Since the pH of fluoride-containing wastewater is 6, there is no need to adjust the pH. - Add 1 mL of 10% PAC (polyaluminium chloride solution) of conventional defluoridation agent to the solution (concentration of about 20 mg / L), stir for 5 minutes, add 1 ml of 0.1% PAM (polyacrylamide), stir for 3 minutes, let stand for 5 minutes, and detect the supernatant F - Concentration. Wet sludge is obtained after filtration and weighed after drying.

[0160] The defluorination effects of the defluorination agents prepared in the above examples and comparative examples are shown in Table 3.

[0161] Table 3

[0162]

[0163]

[0164] The results show that the present invention is suitable for the treatment of low-concentration fluoride-containing wastewater (F-≤20mg / L). - Concentration ≤ 0.5mg / L, good defluorination effect. Compared with conventional defluorination agents, the rare earth composite defluorination agent produced by this process can not only save the amount of PAC, but also reduce the amount of sludge.

[0165] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth composite defluorinating agent, characterized in that: The following steps are involved: S1: adding a heavy metal capture agent to the rare earth slag raffinate to perform metal impurity adsorption treatment, and removing the heavy metal capture agent after the adsorption treatment to obtain an intermediate treatment liquid; S2: preheating the intermediate treatment liquid to obtain a preheated material; S3: evaporating and concentrating the preheated material to obtain a concentrated solution; S4: Cooling and crystallization to obtain a rare earth composite defluorinating agent.

2. The method for preparing the rare earth composite defluorinating agent according to claim 1, characterized in that: Step S1, The rare earth slag raffinate contains at least Al, Ti, Fe, Pb, Cr, As, Cd or Hg elements; preferably, the rare earth slag raffinate contains aluminum, calculated as aluminum oxide, and the mass content of aluminum oxide is 4% to 6%; More preferably, The preparation steps of the rare earth slag raffinate are: dissolving the rare earth slag with acid once to obtain a primary acid solution, and performing organic extraction on the primary acid solution to obtain the rare earth slag raffinate.

3. The method for preparing the rare earth composite defluorinating agent according to claim 1, characterized in that: Step S1, Add a heavy metal capture agent to the rare earth slag raffinate and place it at 20-50° C. for adsorption for 50-80 minutes; filter and remove the heavy metal capture agent to obtain the intermediate treatment liquid; Preferably, after static adsorption, an auxiliary agent solution is added and microbubbles are introduced for 20-30 minutes, and then the heavy metal capture agent is removed by filtration to obtain the intermediate treatment solution; More preferably, The mass ratio of the rare earth slag raffinate to the heavy metal capture agent is 1 ton of rare earth slag raffinate: 1-3 g of heavy metal capture agent; and / or, The auxiliary agent is selected from polyacrylamine hydrochloride; and / or, The concentration of the auxiliary agent solution is 0.2-1wt%; and / or, The particle size of the microbubbles is 300-600 nm; and / or, The mass ratio of the auxiliary agent to the heavy metal capture agent is 1:5-10; and / or, The ventilation volume of the microbubbles is 5L / (m 2 ·h)~10L / (m 2 h).

4. The method for preparing the rare earth composite defluorinating agent according to claim 1, characterized in that: Step S1, The heavy metal scavenger is graphene oxide grafted with modified phosphorus-containing groups; preferably, The preparation method of the heavy metal capture agent comprises the following steps: (1) Raw material mixing: dispersing graphite oxide in a phosphorous acid solution to obtain a graphite oxide dispersion; (2) Ultrasonic exfoliation: ultrasonically treating the graphite oxide dispersion to obtain a graphene oxide suspension; (3) adding a catalyst: adding a catalyst to the graphene oxide suspension, dispersing the mixture by ultrasonication again, and vacuum drying to obtain a mixture of graphene oxide and phosphorus trichloride; (4) Preparation of heavy metal scavenger: Under a protective atmosphere, a mixture of the graphene oxide and phosphorus trichloride is subjected to high temperature heat treatment to obtain the heavy metal scavenger.

5. The method for preparing the rare earth composite defluorinating agent according to claim 4, characterized in that: Step (1), The mass volume ratio of graphite oxide to phosphorous acid solution is 1-5 mg:1; and / or, The mass concentration of the phosphorous acid solution is 10% to 50%; and / or, Step (2), The ultrasonic treatment time is 10 min to 60 min; and / or, The power of ultrasonic treatment is 100w~1000w.

6. The method for preparing the rare earth composite defluorinating agent according to claim 4, characterized in that: Step (3), The catalyst is phosphorus trichloride; and / or, The mass ratio of the catalyst to the graphite oxide is 1 to 5:1; and / or, The time for the second ultrasonic dispersion is 10 min to 60 min; and / or, The power of the second ultrasonic treatment is 100w to 1000w; and / or, The vacuum drying temperature is 50-80°C; and / or, Step (4), The temperature of the high temperature heat treatment is 700°C to 900°C; and / or, The high temperature heat treatment time is 30 to 60 minutes; and / or, The protective atmosphere is nitrogen.

7. The method for preparing the rare earth composite defluorinating agent according to claim 1, characterized in that: Step S2: The intermediate treatment liquid is preheated in sequence by a tail gas preheater, a second-effect condensate preheater, and a first-effect condensate preheater to obtain a preheated material, wherein the temperature of the preheated material is 40 to 60° C.; Preferably, The exhaust gas temperature in the exhaust gas preheater is 40 to 60°C; and / or, The temperature of the heat exchange medium in the second-effect condensate preheater is 90-100°C; and / or, The temperature of the heat exchange medium in the first-effect condensate preheater is 130-140°C.

8. The method for preparing the rare earth composite defluorinating agent according to claim 1, characterized in that: Step S3: evaporating and concentrating the preheated material through a second-effect evaporator and a single-effect evaporator to obtain a concentrated solution; Preferably, The temperature of the second-effect evaporator is 90-100°C; and / or, The pressure of the second-effect evaporator is 0.1-0.3MPa; and / or, The evaporation time of the second-effect evaporator is 0.1 to 1 hour; and / or, The temperature of the single-effect evaporator is 100-110°C; and / or, The pressure of the single-effect evaporator is 0.2-0.5 MPa; and / or, The single-effect evaporator has a single-effect evaporation time of 0.1 to 1 hour; and / or, S4: cooling and crystallizing through a flake forming machine to obtain a rare earth composite defluorination agent; Preferably, The cooling crystallization temperature is 70-80°C; and / or the rotation speed of the flaker is 10-20r / min.

9. The rare earth composite defluorinating agent prepared according to the method for preparing the rare earth composite defluorinating agent according to any one of claims 1 to 8, characterized in that: The components of the rare earth composite defluorinating agent include hydrated aluminum sulfate, aluminum chloride and rare earth oxides; wherein the aluminum content, calculated as aluminum oxide, is 8% to 20% by mass; the mass content of rare earth elements is 0.1% to 5%; preferably, the mass content of aluminum oxide is 10% to 16%; further preferably, the mass content of aluminum oxide is 12.5% ​​to 16%; further preferably, the mass content of aluminum oxide is 14% to 16%.

10. Use of the rare earth composite defluorinating agent according to claim 9 in defluorination.

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