Methods and applications of decomposing rare earth minerals from PVC waste

Abstract

This invention discloses a method and its application for decomposing rare earth ores using PVC waste. The method comprises the following steps: 1) mixing crushed PVC waste with rare earth ores to obtain a mixed ore; wherein the mass ratio of PVC in the PVC waste to TREO in the rare earth ores is 1-10:1; 2) roasting the mixed ore obtained in step 1) at 300-550℃ to obtain roasted ore; 3) acid leaching the roasted ore obtained in step 2) to obtain rare earth chlorides. This invention uses PVC waste as a raw material to decompose rare earth ores, not only realizing the reuse of PVC waste but also enabling rapid decomposition of rare earth minerals at relatively low temperatures. The decomposition process requires no transformation process and can directly generate rare earth chlorides.

Description

Technical Field

[0001] This invention relates to a method and application for decomposing rare earth minerals using PVC waste. Background Technology

[0002] PVC, or polyvinyl chloride, is a widely used synthetic material. Due to its versatility, it is widely used in modern industry and daily life. Examples include building materials such as pipes and window frames in the construction industry; insulation layers for wires and cables in the electrical and electronics industry; infusion bags, catheters, and surgical instruments in the medical industry; and various packaging materials in the packaging industry. Because of its wide range of applications, PVC generates a large amount of PVC waste globally each year. Currently, the main methods for recycling and disposing of PVC waste are landfilling, incineration, and recycling. Landfilling or incineration of PVC waste presents several problems and can easily cause secondary pollution. Effective methods for treating PVC waste include dechlorination and catalytic pyrolysis; however, these methods are too costly and difficult to implement.

[0003] Chlorination roasting decomposition process is one of the main methods for extracting rare earth elements from rare earth ores, and it can effectively extract and separate rare earth elements.

[0004] CN1237539A discloses a method for recovering rare earth carbonates from bastnaesite by roasting with ammonium chloride. The method involves grinding the bastnaesite ore finely, then mixing it evenly with NH4Cl and CaCl2, and roasting it for 0.5–3 hours to convert the rare earth elements in the mineral into RECl3. The roasted ore is then leached in hot water with stirring, filtered, and washed to obtain a rare earth leachate. Ammonium bicarbonate is used to precipitate the rare earth elements, with the amount of ammonium bicarbonate being W. NH4HCO3 :W RE The ratio of rare earth carbonate to HCl is 1.5–3:1. Stir for 10–40 minutes, then let stand for 10–36 hours to allow crystallization. This yields easily filterable crystalline rare earth carbonate precipitate, which is then filtered and dried to obtain the rare earth carbonate product with a rare earth content of 55.2%. This method requires the participation of multiple chlorides in the conversion, making the steps relatively cumbersome. Furthermore, the absorption of NH3 and HCl generated by this method is difficult to solve, and it also places high demands on the corrosion resistance of the equipment materials.

[0005] CN1373232A discloses a carbon chlorination method for extracting and separating cerium and non-cerium rare earth elements from rare earth minerals. This method consists of four technical operations, achieving the chemical metallurgical objective of both extracting and separating rare earth elements. These four operations are: 1. Low-temperature carbon chlorination with the addition of a defluorinating agent, selectively chlorinating and effectively separating non-rare earth elements such as fluorine, phosphorus, and iron from the minerals; 2. Separating radioactive elements from rare earth minerals using two different methods: high-temperature chlorination-chemical vapor transport and water dissolution, followed by separation of alkaline earth metal elements from the minerals using oxygen-enriched humid air oxidation and water dissolution; 3. Separating cerium and non-cerium rare earth elements using dilute acid leaching; 4. Separating each non-cerium rare earth element using chemical vapor transport. This method uses high-temperature chlorination, posing a risk of chlorine gas leakage, which is highly harmful to human health. High-temperature chlorination places high demands on equipment, and maintaining the high-temperature conditions requires a large amount of energy, resulting in high energy consumption. This method requires complex separation procedures. The product obtained after high-temperature chlorination decomposition of rare earth ore is a mixture of various rare earth chlorides and other impurity chlorides. These chlorides have similar properties, making separation and purification difficult.

[0006] CN114480888A discloses a method for improving the rare earth recovery rate of bastnaesite. The method includes the following steps: (1) roasting a raw material comprising 100 parts by weight of bastnaesite, 25-40 parts by weight of magnesium chloride, and 10-30 parts by weight of carbon powder in a microwave field with a microwave power of 200-800W and a roasting decomposition temperature of 600-800℃ for 30-70 minutes to obtain roasted ore; (2) leaching the roasted ore with 0.1-0.8 mol / L hydrochloric acid at 100-250℃ to obtain an acid leachate and a rare earth chloride solution. This method requires the addition of magnesium chloride and carbon powder, resulting in high costs.

[0007] CN117587271A discloses a method for extracting rare earth elements from mixed rare earth concentrates via chlorination and for their comprehensive utilization. This method uses rare earth concentrates as raw materials, chlorine as a chlorinating agent, carbon monoxide as a reducing agent, alumina as a fluoride and phosphorus fixative, and oxygen as a heat regulator. It utilizes high-temperature flue gas containing carbon monoxide, generated by "oxygen-enriched and oxygen-deficient" combustion in a gas-fired boiler, as both a heat source and a carbon source for the rare earth carbothermic chlorination reaction. This method requires two steps to decompose the rare earth minerals. The first step involves reacting alumina with excess carbon monoxide and excess chlorine at a temperature range of 600–1000°C to obtain a mixed gas composed of aluminum chloride, carbon monoxide, chlorine, and carbon dioxide. The second step is the chlorination reaction of the rare earth minerals. The chlorides obtained by this method have complex compositions, are difficult to separate, and result in a low rare earth recovery rate. Summary of the Invention

[0008] In view of this, one object of the present invention is to provide a method for decomposing rare earth ores using PVC waste, which can effectively decompose rare earth ores at a lower temperature while utilizing PVC waste. Another object of the present invention is to provide an application of PVC in decomposing rare earth ores to reduce roasting temperature and obtain rare earth chlorides.

[0009] The present invention achieves the above objectives using the following technical solutions.

[0010] On the one hand, the method for decomposing rare earth minerals using PVC waste provided by the present invention includes the following steps:

[0011] 1) The crushed PVC waste is mixed with rare earth ore to obtain mixed ore; wherein the molar ratio of PVC in the PVC waste to TREO in the rare earth ore is 1 to 10:1;

[0012] 2) The mixed ore obtained in step 1) is roasted and decomposed at 300-550℃ to obtain roasted ore;

[0013] 3) The roasted ore obtained in step 2) is acid-leached to obtain rare earth chlorides.

[0014] According to the method of the present invention, preferably, the rare earth ore is selected from at least one of fluorocarbon cerium ore, fluorocarbon calcium cerium ore, fluoride cerium ore, and mixed rare earth ore.

[0015] According to the method of the present invention, preferably, in step 1), the crushed PVC waste is mixed with rare earth ore and ground to obtain mixed ore; the particle size of the mixed ore is -100 to -500 mesh.

[0016] According to the method of the present invention, preferably, in step 2), the calcination temperature is 320-520°C.

[0017] According to the method of the present invention, preferably, in step 2), the roasting time is 0.5 to 5 hours.

[0018] According to the method of the present invention, preferably, in step 2), the heating rate of the roasting is 0.5 to 30 °C / min.

[0019] According to the method of the present invention, preferably, in step 3), the acid leaching temperature is 20-95°C.

[0020] According to the method of the present invention, preferably, in step 3), the acid leaching time is 0.2 to 5 hours.

[0021] According to the method of the present invention, preferably, in step 3), hydrochloric acid is used for acid leaching; the liquid-to-solid ratio during acid leaching is 1 to 10:1.

[0022] On the other hand, the present invention also provides the application of PVC in the decomposition of rare earth ores to reduce the roasting temperature and obtain rare earth chlorides.

[0023] This invention uses PVC waste as a raw material to decompose rare earth minerals. This not only achieves the reuse of PVC waste but also enables rapid decomposition of rare earth minerals at relatively low temperatures. The decomposition process requires no transformation and directly generates rare earth chlorides. The process is simple, environmentally friendly, and has low production costs, making it suitable for large-scale production and showing promising prospects for large-scale industrial applications. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] The term "TREO" in this invention refers to the total amount of rare earth oxides.

[0026] <Methods for decomposing rare earth minerals using PVC waste>

[0027] The method for decomposing rare earth ore from PVC waste according to the present invention includes a mixing step, a roasting step, and an acid leaching step. These are described in detail below.

[0028] Mixing steps

[0029] The crushed PVC waste is mixed with rare earth ore to obtain a mixed ore. Preferably, the crushed PVC waste is mixed with rare earth ore and then ground to obtain the mixed ore.

[0030] According to one embodiment of the present invention, the rare earth ore may be selected from at least one of bastnaesite, bastnaesite, cerium fluoride ore, and mixed rare earth ore, preferably at least one of bastnaesite, bastnaesite, and cerium fluoride ore, and more preferably at least one of bastnaesite and bastnaesite. The mixed rare earth ore is preferably Bayan Obo mixed rare earth ore.

[0031] According to one embodiment of the present invention, the TREO in the rare earth ore can be 3.5 to 75 wt%, preferably 10 to 70 wt%, and more preferably 30 to 70 wt%.

[0032] According to one embodiment of the present invention, the PVC content in the PVC waste can be 30-98 wt%, preferably 30-95 wt%, and more preferably 40-95 wt%.

[0033] In this invention, PVC waste can be any type of PVC-containing waste known in the art, and is not particularly limited herein. For example, but not limited to, PVC waste can be: pure PVC product waste (PVC pipes, sheets, etc., with a PVC content of about 90 wt% or more), PVC-containing composite material waste (electrical cable sheaths, composite wall panels, etc., with a PVC content of about 30-70 wt%), mixed waste of PVC and other plastics (PVC content of about 40-50%), and PVC product processing scraps (PVC content of about 80-95 wt%).

[0034] In this invention, the crushing of PVC waste can be achieved by any crushing method or equipment known in the art, and no particular limitation is made herein. For example, but not limited to, a mechanical crusher or an air jet mill can be used.

[0035] According to one embodiment of the present invention, the particle size of the crushed PVC waste mixed with rare earth ore and ground can be -100 to -500 mesh, preferably -100 to -400 mesh, and more preferably -200 to -400 mesh. A suitable particle size is beneficial for the PVC to participate in the decomposition of rare earth oxides in the rare earth ore during the roasting process, and is also more conducive to the leaching of rare earth elements.

[0036] In this invention, grinding can be performed using grinding methods or equipment known in the art, and is not particularly limited thereto. For example, but not limited to, vertical mills, disc mills, or ball mills can be used.

[0037] According to one embodiment of the present invention, the mass ratio of PVC in PVC waste to TREO in rare earth ore can be 1 to 10:1, preferably 2 to 8:1, and more preferably 3 to 6:1.

[0038] A reasonable reactant ratio is beneficial for PVC to participate in the decomposition of rare earth oxides in rare earth ores during the roasting process, and is more conducive to the leaching of rare earth elements.

[0039] roasting steps

[0040] The mixed ore obtained in step 1) is roasted and decomposed at 300-550℃ to obtain roasted ore.

[0041] According to one embodiment of the present invention, the heating rate of the roasting can be 0.5 to 30 °C / min, preferably 1 to 30 °C / min, and more preferably 1 to 20 °C / min.

[0042] According to one embodiment of the present invention, the calcination temperature can be 300-550°C, preferably 320-520°C, and more preferably 350-500°C.

[0043] According to one embodiment of the present invention, the roasting time can be 0.5 to 5 hours, preferably 1 to 4 hours, and more preferably 1 to 3 hours.

[0044] Reasonable roasting conditions are conducive to the decomposition of rare earth oxides in rare earth ores by PVC during the roasting process, and are also more conducive to the leaching of rare earth elements.

[0045] During the roasting and heating process, PVC begins to decompose around 300℃, producing HCl gas. At lower temperatures, it begins to decompose rare earth ore. As the temperature continues to rise, chemical bonds break, and the resulting carbon-containing reducing agent (C or CO) prevents the oxidation of trivalent cerium during the rare earth ore decomposition process. Therefore, no conversion is needed, and acid leaching can be performed directly to obtain rare earth chlorides, shortening the production process. The selective chlorination of this invention separates non-rare earth elements in rare earth concentrate and other impurities in PVC waste from rare earth elements, effectively improving the extraction efficiency of rare earth elements.

[0046] Acid leaching steps

[0047] The roasted ore is acid-leached to obtain rare earth chlorides.

[0048] According to one embodiment of the present invention, the acid leaching temperature can be 20-95°C, preferably 25-92°C, and more preferably 30-90°C.

[0049] According to one embodiment of the present invention, the acid leaching time can be 0.2 to 5 hours, preferably 0.5 to 4 hours, and more preferably 0.5 to 3 hours.

[0050] According to one embodiment of the present invention, hydrochloric acid is preferably used for acid leaching. The concentration of the hydrochloric acid used can be any concentration and is not particularly limited herein. For example, it can be 1 to 10 mol / L, preferably 1 to 8 mol / L, and more preferably 2 to 7 mol / L.

[0051] According to one embodiment of the present invention, the liquid-to-solid ratio during acid leaching can be 1 to 10:1, preferably 2 to 8:1, and more preferably 2 to 6:1.

[0052] Limiting the acid leaching conditions to the above range is beneficial for the conversion of rare earth elements in roasted ore into rare earth chlorides, thereby improving leaching efficiency.

[0053] In the method of this invention, the mineral decomposition rate is above 95%.

[0054] <Application>

[0055] This invention also provides an application of PVC in the decomposition of rare earth ores to reduce roasting temperature and obtain rare earth chlorides. This invention allows the decomposition of rare earth ores using PVC waste, thus reusing the PVC waste and reducing the roasting temperature from the existing 650–1200°C to below 550°C. During the concentrate decomposition process, the oxidation of trivalent cerium can be prevented, and the obtained trivalent rare earths can be directly acid-leached to obtain rare earth chlorides without conversion, shortening the process. Specific steps and parameters are as described above and will not be repeated here.

[0056] <Testing Method>

[0057] The mineral decomposition rate is calculated using the following formula:

[0058]

[0059] Where μ is the mineral decomposition rate (%);

[0060] C represents the concentration (g / L) of rare earth chlorides in the solution after acid leaching, expressed as TREO.

[0061] V is the volume (L) of the rare earth chloride solution;

[0062] ω represents the content of rare earth compounds in bastnaesite, expressed as TREO (wt%).

[0063] m represents the mass (g) of bastnaesite.

[0064] The TREO content was determined in accordance with GB / T 18114.1-2010; rare earth elements were determined using a Thermo Fisher Scientific iCAP 6300 inductively coupled plasma mass spectrometer, and the TREO content was calculated based on the conversion relationship between elements and oxides.

[0065] <Ingredient Description>

[0066] Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0067] Among them, the PVC waste consists of scrapped PVC pipes, which come from the Baotou Rare Earth Research Institute.

[0068] The fluorocarbon cerium ore was mined in Mianning, Sichuan.

[0069] Example 1

[0070] 200g of PVC waste (PVC content 83wt%) was crushed and mixed evenly with 100g of fluorocarbon cerium ore (TREO content 55.3wt%). Then, the mixture was ground until the particle size of the mixture was -400 mesh to obtain the mixed ore.

[0071] The mixed ore is placed in a roasting furnace and heated to 500°C at a rate of 1°C / min. It is then roasted and decomposed at 500°C for 1 hour to obtain roasted ore.

[0072] Acid leaching was performed on the roasted ore by adding 6 mol / L hydrochloric acid (liquid-to-solid ratio of 2:1, i.e., the mass ratio of hydrochloric acid to roasted ore was 2:1) and leaching was carried out at 90℃ for 0.5 h to obtain rare earth chlorides.

[0073] Tests showed that the mineral decomposition rate of bastnaesite was 95%.

[0074] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for decomposing rare earth minerals using PVC waste, comprising the following steps: 1) The crushed PVC waste is mixed with rare earth ore to obtain mixed ore; wherein, the mass ratio of PVC in the PVC waste to TREO in the rare earth ore is 1 to 10:1; the rare earth ore is selected from at least one of bastnaesite, bastnaesite, cerium fluoride ore, and mixed rare earth ore. 2) The mixed ore obtained in step 1) is roasted and decomposed at 350-500℃ for 0.5-5 hours to obtain roasted ore; 3) The roasted ore obtained in step 2) is subjected to hydrochloric acid leaching at 20-95℃ for 0.2-5 hours to obtain rare earth chlorides; wherein the liquid-solid ratio during acid leaching is 1-10:

1.

2. The method according to claim 1, characterized in that, The rare earth mineral is selected from at least one of bastnaesite and bastnaesite.

3. The method according to claim 1, characterized in that, In step 1), the crushed PVC waste is mixed with rare earth ore and ground to obtain mixed ore; the particle size of the mixed ore is -100 to -500 mesh.

4. The method according to claim 1, characterized in that, In step 2), the heating rate of the roasting is 0.5 to 30 °C / min.

5. An application of PVC in the decomposition of rare earth ores to lower the roasting temperature and obtain rare earth chlorides while simultaneously increasing the mineral decomposition rate, characterized in that... Includes the following steps: 1) The crushed PVC waste is mixed with rare earth ore to obtain mixed ore; wherein, the mass ratio of PVC in the PVC waste to TREO in the rare earth ore is 1 to 10:1; the rare earth ore is selected from at least one of bastnaesite, bastnaesite, cerium fluoride ore, and mixed rare earth ore. 2) The mixed ore obtained in step 1) is roasted and decomposed at 350-500℃ for 0.5-5 hours to obtain roasted ore; 3) The roasted ore obtained in step 2) is subjected to hydrochloric acid leaching at 20-95℃ for 0.2-5 hours to obtain rare earth chlorides; wherein the liquid-solid ratio during acid leaching is 1-10:1.

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