A rare earth element modified aluminum-iron based defluorination agent and preparation method thereof

Abstract

The present invention discloses a rare earth element modified aluminum iron-based defluorinating agent and a preparation method thereof. The defluorinating agent in the present invention is composed of an aluminum iron base material and a rare earth composite modified material, and the mass ratio of the aluminum iron base material to the rare earth composite modified material is 100: (1-5); the aluminum iron base material is composed of activated alumina, aluminum salt and iron salt, and the mass ratio of the activated alumina, aluminum salt and iron salt is (3-5): (10-18): (5-8); the rare earth composite modified material is a rare earth element chloride. The aluminum iron-based defluorinating agent in the present invention has a simple production process, and the obtained rare earth element chloride can be directly used without separation and purification, so that the production cost is greatly reduced, and the rare earth element modified aluminum iron-based defluorinating agent prepared in the present invention can be used for the deep treatment of fluorine-containing wastewater, and the defluorination effect is remarkable, especially for fluorine-containing wastewater with a fluoride ion concentration of less than 8mg / L. After deep treatment, its defluorination rate can reach up to 90.79%.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine-containing wastewater treatment, and in particular to a rare earth element modified aluminum-iron based defluorinating agent and a preparation method thereof. Background Art

[0002] With the continuous development of new energy and new material chemical industries, the production of more new materials is increasingly dependent on fluorine. For example, in order to etch the front and edge of silicon wafers in the photovoltaic industry (TOPCon), in order to remove the BSG (borosilicate glass) on the front and edge, one of the main raw materials used is hydrofluoric acid and hydrochloric acid. At the same time, the photovoltaic industry is also one of the enterprises that discharge a large amount of wastewater, which will inevitably lead to more and more fluorine-containing wastewater discharge, and the generation of these fluorine-containing wastewater will seriously harm the surrounding ecological environment and human health.

[0003] How to effectively treat fluoride-containing wastewater, reduce water pollution and ecological damage caused by the discharge of fluoride-containing wastewater, and reduce adverse effects on animals, plants and humans is extremely important. At present, the main method for treating high-concentration fluoride-containing wastewater is calcium precipitation, that is, adding a certain amount of calcium hydroxide, calcium oxide, etc. to the fluoride-containing wastewater first, and then adding a certain amount of calcium chloride at the end to produce calcium fluoride precipitation. However, due to the Ksp of calcium fluoride = 2.7*10 -11 This determines that the calcium precipitation method can effectively reduce the concentration of fluoride ions to 8 mg / L, but it does not meet the requirements of Class III of the "Surface Water Environmental Quality Standard" (GB3838-2002), that is, the fluoride ion concentration is less than 1.0 mg / L, and the fluoride-containing wastewater needs further deep treatment. For example, Chinese invention patent CN 113772762A provides an aluminum-based composite defluoridation agent and a preparation method thereof. After modification with rare earth elements (lanthanum oxide, cerium oxide), the defluoridation effect reaches more than 76.25%. However, the existing rare earth element composite dechlorination agent has a poor defluoridation effect and a high production cost, and is not suitable for application in the treatment of large-scale industrial fluoride-containing wastewater. Summary of the invention

[0004] The purpose of the present invention is to solve the problems in the prior art that rare earth element composite dechlorinators have poor defluorination effect and high production cost, and to provide a rare earth element modified aluminum-iron based defluorinator and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a rare earth element modified aluminum-iron based defluorinating agent, composed of an aluminum-iron base material and a rare earth composite modified material, the mass ratio of the aluminum-iron base material to the rare earth composite modified material is 100:(1-5); the aluminum-iron base material is composed of activated alumina, aluminum salt and iron salt, the mass ratio of the activated alumina, aluminum salt and iron salt is (3-5):(10-18):(5-8); the rare earth composite modified material is a rare earth element chloride.

[0006] Preferably, the rare earth element chloride is one or more of lanthanum chloride, neodymium chloride, cerium chloride and praseodymium chloride.

[0007] Preferably, the activated alumina refers to γ-Al2O3, with a mesh size of 325 meshes, a particle size of about 0.045 mm, and a comparative area of ​​≥280 m 2 / g, pore volume>0.4mL / g.

[0008] Preferably, the aluminum salt is one of polyaluminum chloride, polyaluminum sulfate, aluminum chloride and aluminum sulfate.

[0009] Preferably, the iron salt is one of polyferric chloride, polyferric sulfate, ferric chloride and ferric sulfate.

[0010] The present invention also provides a method for preparing the rare earth element modified aluminum-iron based defluorination agent, comprising the following steps:

[0011] S1. Mix the rare earth concentrate with carbon, and heat them in a vertical electric furnace at 700-800°C for 4-6 hours, while introducing chlorine gas, and collect the low-boiling-point rare earth chlorides in a condenser for later use;

[0012] S2. Add 68.5%-89.9% water to the reactor, heat it to 50-70°C, and control the mass fraction of the aluminum-iron base material to be 10%-30%. Add the aluminum-iron base material to the reactor under stirring conditions of 600-800rpm. After all the aluminum-iron base materials are dissolved, add sulfuric acid to adjust the pH to between 2-3, then add 0.1%-1.5% of rare earth element chloride by mass fraction, keep it at 60°C for 1h, stop heating, and age it at room temperature for 24h to obtain the rare earth element modified aluminum-iron based defluorinating agent.

[0013] Preferably, the mixing ratio of the rare earth concentrate to carbon is (4-6):1.

[0014] The beneficial effects of the present invention are:

[0015] (1) The production process of the aluminum-iron based defluorinating agent in the present invention is simple, and the raw materials can be prepared by simple mixing, aging, pH adjustment and the like. At the same time, the rare earth concentrate is decomposed by the chlorination method, and the obtained rare earth element chloride can be directly used without separation and purification, which greatly reduces the production cost and is conducive to large-scale industrial application.

[0016] (ii) The rare earth element modified aluminum-iron based defluorinating agent prepared in the present invention can be used for deep treatment of fluorine-containing wastewater, and has a significant defluorination effect, especially for fluorine-containing wastewater with a fluoride ion concentration below 8 mg / L, after deep treatment, the defluorination rate can reach up to 90.79%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the production process flow chart of rare earth element modified aluminum-iron based defluoridating agent. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0019] Example 1 Preparation of rare earth element chlorides

[0020] The rare earth concentrate is mixed with carbon in a mass ratio of 80% and 20%, and heated in a vertical electric furnace at 700-800°C for 6 hours. Chlorine gas is introduced at the same time. The rare earth chloride with a low boiling point is collected in a condenser for later use due to the different boiling points between the rare earth chloride and the non-rare earth chloride.

[0021] Example 2 Preparation of rare earth element modified aluminum iron based defluorination agent A1

[0022] Weigh 30 g of activated alumina, 180 g of polyaluminum sulfate, and 80 g of polyferric sulfate in a mass ratio of 3:18:8, and mix them evenly to obtain aluminum-iron base material A.

[0023] Add 710g of water to a 1000mL beaker, raise the temperature to 60°C, add the above-mentioned aluminum-iron base material A to the beaker at a rotation speed of 600rpm, and after it is completely dissolved, add sulfuric acid to adjust the pH to between 2-3, add 2.9g of the rare earth element chloride prepared in Example 1, keep warm at 60°C for 1h, stop heating, and age at room temperature for 24h to obtain rare earth element modified aluminum-iron based defluorinating agent A1.

[0024] Example 3 Preparation of rare earth element modified aluminum iron based defluorination agent A2

[0025] Weigh 30 g of activated alumina, 180 g of polyaluminum sulfate, and 80 g of polyferric sulfate in a mass ratio of 3:18:8, and mix them evenly to obtain aluminum-iron base material A.

[0026] Add 710g of water to a 1000mL beaker, raise the temperature to 60°C, add the above-mentioned aluminum-iron base material A to the beaker at a rotation speed of 600rpm, and after it is completely dissolved, add sulfuric acid to adjust the pH to between 2-3, add 5.8g of rare earth element chloride prepared in Example 1, keep warm at 60°C for 1h, stop heating, and age at room temperature for 24h to obtain rare earth element modified aluminum-iron based defluorinating agent A2.

[0027] Example 4 Preparation of rare earth element modified aluminum iron based defluorination agent B1

[0028] Weigh 50g of activated alumina, 120g of polyaluminum sulfate and 60g of polyferric sulfate respectively according to the mass ratio of 5:12:6, and mix them evenly to obtain aluminum-iron base material B.

[0029] Add 770g of water to a 1000mL beaker, raise the temperature to 60°C, add the above-mentioned aluminum-iron base material B to the beaker at a rotation speed of 800rpm, and after it is completely dissolved, add sulfuric acid to adjust the pH between 2-3, add 2.9g of rare earth element chloride prepared in Example 1, keep warm at 60°C for 1h, stop heating, and age at room temperature for 24h to obtain rare earth element modified aluminum-iron based defluorinating agent B1.

[0030] Example 5 Preparation of rare earth element modified aluminum iron based defluorination agent B2

[0031] Weigh 50g of activated alumina, 120g of polyaluminum sulfate and 60g of polyferric sulfate respectively according to the mass ratio of 5:12:6, and mix them evenly to obtain aluminum-iron base material B.

[0032] Add 770g of water to a 1000mL beaker, raise the temperature to 60°C, add the above-mentioned aluminum-iron base material B to the beaker at a rotation speed of 800rpm, and after it is completely dissolved, add sulfuric acid to adjust the pH between 2-3, add 5.8g of rare earth element chloride prepared in Example 1, keep warm at 60°C for 1h, stop heating, and age at room temperature for 24h to obtain rare earth element modified aluminum-iron based defluorinating agent B2.

[0033] The production process of Examples 1-5 is shown in the attached Figure 1 shown.

[0034] Verification of the defluorination effect of the rare earth element modified aluminum-iron based defluorination agent prepared by the present invention

[0035] The commercially available aluminum-iron based defluorinating agent was used as a control, the main components of which were polyaluminum chloride, ferric sulfate, etc. The rare earth element modified aluminum-iron based defluorinating agents A1, A2, B1, and B2 prepared in Examples 2-5 were used as experimental groups to verify the defluorination effect. The specific experimental steps were as follows:

[0036] Step 1: Preliminary determination of F in raw water - The concentration is 7.6 mg / L;

[0037] Step 2: Add 1000mL of raw water sample to each of the five 1000mL beakers 1#-5# and place them on a stirrer. 1#-5# are A1, A2, B1, B2 and the control group.

[0038] Step 3: Control the rotation speed to 200 r / min at room temperature, add defluorinators A1, A2, B1, B2 and 0.7 g of commercially available aluminum-iron-based defluorinator into the raw water according to the groups, and stir for 5 minutes.

[0039] Step 4: Add sodium hydroxide solution to adjust the pH to 6.0-7.0.

[0040] Step 5: Add 3 mg of cationic PAM, control the rotation speed to 60 r / min, stir for 0.5 min, and let stand for 20 min.

[0041] Step 6: Take the supernatant and test F - concentration.

[0042] The test results are shown in Table 1.

[0043] Table 1 Defluorination effect data of rare earth element modified aluminum iron based defluorination agent

[0044]

[0045]

[0046] The data in Table 1 show that the rare earth element modified aluminum-iron based defluorinating agents A1, A2, B1 and B2 prepared in the present invention have significantly higher defluorination effects on fluorine-containing wastewater than commercially available aluminum-iron based defluorinating agents.

[0047] The specification and drawings of the present invention are considered to be illustrative rather than restrictive. On the basis of the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features according to the disclosed technical content without creative labor, all of which are within the protection scope of the present invention.

Claims

1. A rare earth element modified aluminum iron based defluorination agent, It is characterized in that It is composed of an aluminum-iron base material and a rare earth composite modified material, wherein the mass ratio of the aluminum-iron base material to the rare earth composite modified material is 100:(1-5); the aluminum-iron base material is composed of activated alumina, aluminum salt and iron salt, wherein the mass ratio of the activated alumina, aluminum salt and iron salt is (3-5):(10-18):(5-8); the rare earth composite modified material is a rare earth element chloride; The activated alumina refers to γ-Al 2 O 3 , mesh number is 325 mesh, particle size is about 0.045mm, comparison area ≥280m 2 / g, pore volume>0.4mL / g; The preparation method of the rare earth element modified aluminum-iron based defluorination agent comprises the following steps: S1. Mix the rare earth concentrate with carbon, and heat them in a vertical electric furnace at 700-800°C for 4-6 hours, while introducing chlorine gas, and collect the low-boiling-point rare earth chloride in a condenser for later use; S2. Add 68.5%-89.9% water into the reactor, raise the temperature to 50-70°C, control the mass fraction of the aluminum-iron base material to 10%-30%, add the aluminum-iron base material into the reactor under stirring at 600-800rpm, and after all the materials are dissolved, add sulfuric acid to adjust the pH value to 2-3, then add 0.1%-1.5% of rare earth chloride by mass fraction, keep warm at 60°C for 1h, stop heating, and age at room temperature for 24h to obtain rare earth element modified aluminum-iron based defluorinating agent.

2. A rare earth element modified aluminum-iron based defluorination agent according to claim 1, It is characterized in that The rare earth element chloride is one or more of lanthanum chloride, neodymium chloride, cerium chloride and praseodymium chloride.

3. A rare earth element modified aluminum-iron based defluorination agent according to claim 1, It is characterized in that The aluminum salt is one of polyaluminum chloride, polyaluminum sulfate, aluminum chloride and aluminum sulfate.

4. A rare earth element modified aluminum-iron based defluorination agent according to claim 1, It is characterized in that The iron salt is one of polyferric chloride, polyferric sulfate, ferric chloride and ferric sulfate.

5. A rare earth element modified aluminum-iron based defluorination agent according to claim 1, It is characterized in that The mixing ratio of the rare earth concentrate and carbon is (4-6):1.

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