A method for mechanically and chemically strengthening deconstruction and recycling of rare earth in waste polishing powder and high-quality regeneration of La2O3 / CeO2 catalyst for catalytic degradation of VOCs

Abstract

The present application relates to a kind of mechanical chemical strengthening deconstruction recycling waste polishing powder rare earth and high quality regeneration catalyst for catalytic degradation VOCs method of La2O3 / CeO2.Catalyst.First, the physicochemical properties of rare earth components in waste polishing powder are changed by mechanical chemical strengthening deconstruction, then rare earth ion-containing leaching solution is obtained by dilute acid leaching, then the leaching solution is removed by means such as complex salt precipitation to obtain high-purity rare earth nitrate solution, finally, La2O3 / CeO2-based catalyst is prepared by template method and used for thermal catalytic degradation VOCs.The recovery rate of rare earth in waste polishing powder is more than 98%, and the thermal catalytic degradation efficiency of La2O3 / CeO2 catalyst regenerated for typical VOCs (styrene) can reach more than 99%;The method has excellent rare earth recovery efficiency, and high-activity La2O3 / CeO2 catalyst is regenerated, which provides an effective way for efficient recovery and high-quality recycling of rare earth in waste polishing powder.

Description

Technical Field

[0001] The present invention relates to the technical field of valuable metal recovery and high-quality utilization in solid waste, and in particular to a method for recovering rare earths from waste polishing powder by mechanochemically enhanced deconstruction and high-quality regeneration of La2O3 / CeO2 catalyst for catalytic degradation of VOCs. Background Art

[0002] As an important strategic metal resource, rare earth elements (REEs) play a vital role in clean energy, environmental protection, and military applications, driven by continuous advancements in science, technology, and industry. With the increasing demand for rare earths, particularly in optoelectronics, magnetic materials, and catalysts, the sustainable utilization of these resources has become increasingly prominent. However, the mining of raw rare earth ore is not only costly but also places significant strain on the ecological environment. Therefore, the recovery and efficient reuse of REEs from solid waste resources has become a crucial issue that needs to be addressed. Waste polishing powder, a byproduct of industries such as electronics, optics, and machining, has become a key source of rare earth recovery from solid waste. Waste polishing powder is rich in REEs, particularly lanthanides such as lanthanum and cerium. Therefore, the recovery and reuse of REEs from waste polishing powder not only reduces the waste of rare earth resources and generates significant economic benefits, but also replaces primary mineral resources to a certain extent, alleviating the environmental burden of raw ore mining. Furthermore, volatile organic compounds (VOCs) are major precursors of atmospheric pollutants, making VOC emission control particularly urgent to improve air quality. Rare earth-based catalysts demonstrate significant advantages in catalytic degradation of VOCs and their selectivity. Against this backdrop, the recovery of rare earths from waste polishing powder and their upgrading into rare earth-based catalysts for VOC degradation not only offers new insights into the sustainable utilization of rare earth resources but also provides a more efficient solution for VOC pollution control.

[0003] Chinese Patent 104371555A discloses a method for recycling and regenerating waste polishing powder. This method involves mixing the waste polishing powder with nitric acid, adding hydrogen peroxide to the bottom of the solution, and heating to dissolve it. Ammonia is then used to adjust the pH and precipitate the mixture, yielding rare earth oxides. Chinese Patent CN111471865A discloses a method for recycling waste rare earth polishing powder. This method utilizes strong acid multi-stage countercurrent leaching followed by extraction and stripping to yield a high-purity rare earth chloride solution. These methods are not only complex and require high chemical reagent consumption, but also require a specialized multi-stage countercurrent leaching unit, resulting in high water and energy consumption and recovery costs.

[0004] In summary, in view of the problems and defects in the existing technical processes for the recovery and reuse of rare earth elements in waste polishing powder, it is of great strategic significance to design and develop a method for the recovery and reuse of rare earth elements in waste polishing powder with high rare earth element recovery efficiency, low environmental pollution and good reuse effect. SUMMARY

[0005] In order to overcome the deficiencies of the existing recycling technology of rare earth in waste polishing powder, the purpose of the present application is to provide a method for recycling rare earth in waste polishing powder by mechanical-chemical strengthening deconstruction and regenerating La2O3 / CeO2 catalyst for catalytic degradation of VOCs. The method first pretreats the waste polishing powder by mechanical-chemical strengthening deconstruction, changes the chemical properties of the structure stability of the rare earth components in the waste polishing powder, and makes it change from difficult leaching type to easy leaching type; then combines the mechanical-chemical strengthening deconstruction product with acid leaching extraction technology and double salt precipitation technology to realize efficient separation and purification of rare earth elements; finally, the La2O3 / CeO2 catalyst is regenerated by the sacrifice template method and used for efficient catalytic degradation of VOCs. Thus, a process with mild reaction conditions, high economic benefits and strong universality is provided to achieve efficient recovery and upgrading of rare earth in waste polishing powder and realize its resource utilization.

[0006] A method for recycling rare earth in waste polishing powder by mechanical-chemical strengthening deconstruction and regenerating La2O3 / CeO2 catalyst for catalytic degradation of VOCs, comprising the following steps:

[0007] (1) Mechanical-chemical strengthening deconstruction of waste polishing powder: mix waste polishing powder, NaOH and deionized water, and use a high-energy ball mill to perform mechanical-chemical reaction on the mixture. After the mechanical-chemical reaction is completed, rinse with deionized water, and filter to obtain waste polishing powder deconstruction residue and filtrate 1. The reaction conditions for the mechanical-chemical strengthening deconstruction of the waste polishing powder are as follows: the mass ratio of waste polishing powder to NaOH is 5:1-1:1 g / g, the mass ratio of waste polishing powder to deionized water is 5:1-1:1 g / g, the ball-to-material ratio is 1:5-1:25 g / g, the rotation speed of the ball mill is 200-800 rpm, and the ball milling time is 1-6 hours.

[0008] (2) Acid leaching extraction of rare earth elements: mix the waste polishing powder deconstruction residue obtained in step (1) with a hydrochloric acid solution, and perform acid leaching reaction under heating and stirring conditions. After the reaction is completed, perform solid-liquid separation, and filter to obtain leaching residue and rare earth-containing leaching solution. The acid leaching reaction conditions are as follows: the molar concentration of the hydrochloric acid solution is 2-8 mol / L, the solid-liquid ratio of the deconstruction residue after drying to the hydrochloric acid solution is 1:10-1:20 kg / L, the leaching temperature is 60-90℃, the leaching time is 1-6 hours, and the stirring rate is 200-600 rpm.

[0009] (3) Precipitation, separation and purification of complex salts of rare earth elements: the rare earth-containing leachate obtained in step (2) is mixed with Na2SO4, and a rare earth complex salt precipitation reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and filtration is performed to obtain CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate and filtrate 2; then the CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate is reacted with NaOH solution, and after the reaction is completed, solid-liquid separation is carried out to obtain filtrate 3 and rare earth hydroxide, which are then reacted with dilute nitric acid solution to convert into a La(NO3)3 / Ce(NO3)4 mixed solution, and dried under low temperature conditions to obtain a La(NO3)3 / Ce(NO3)4 solid product. The reaction conditions for the double salt precipitation, separation and purification are as follows: the mass ratio of sodium sulfate to rare earth leachate is 100-200 g / L, the reaction temperature is 60-100°C, the reaction time is 10-90 minutes, the molar concentration of the dilute nitric acid solution is 0.1-1.0 mol / L, the mass concentration of the NaOH solution is 30%-50%, and the drying temperature of the La(NO3)3 / Ce(NO3)4 mixed solution is 60-100°C.

[0010] (4) Preparation of La2O3 / CeO2 catalyst by template method: A small amount of ethanol is added to the La(NO3)3 / Ce(NO3)4 solid product obtained in step (3) to dissolve it. The La(NO3)3 / Ce(NO3)4 solid product, ethanol solution and mesoporous SiO2 template are uniformly mixed and dried. The mixture is then calcined in a box furnace to form a La2O3 / CeO2 catalyst-supported SiO2 composite material. The La2O3 / CeO2 catalyst-supported SiO2 composite material reacts with a NaOH solution to remove the SiO2 template. The final product is separated by centrifugation and dried to obtain a La2O3 / CeO2 catalyst. The reaction conditions for preparing the La2O3 / CeO2 catalyst by the template method are as follows: the mass ratio of the La(NO3)3 / Ce(NO3)4 solid product to the mesoporous SiO2 template is 1:1~4:1 g / g, the drying temperature of the mixture is 30°C~80°C, the calcination temperature is 600~900°C, and the insulation time is 1~4 hours; when removing the template, the molar concentration of the NaOH solution is 1~10 mol / L, the reaction temperature is 60~90°C, the reaction time is 24~72 hours, the centrifuge speed is 6000~10000 rpm, the centrifugation time is 5~10 minutes, and the drying temperature of the final product La2O3 / CeO2 catalyst is 30~80°C.

[0011] Compared to existing rare earth recovery processes from waste polishing powder, the present invention utilizes mechanochemical enhanced decomposition technology to quickly and easily alter the physicochemical properties of the rare earth components in the waste polishing powder. This reduces the activation energy of the rare earth leaching reaction and enhances its leaching activity, significantly increasing the leaching rate of the rare earth elements. Furthermore, a sacrificial template method is used to regenerate and prepare a highly active La2O3 / CeO2 catalyst for catalytic degradation of VOCs. This invention provides a process with mild reaction conditions, high rare earth recovery efficiency, and high VOC degradation efficiency of the regenerated catalyst, achieving efficient recovery and high-quality recycling of rare earths from waste polishing powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A flow chart showing a method for mechanochemically enhanced deconstruction and recovery of rare earths from waste polishing powder and high-quality regeneration of La2O3 / CeO2 catalyst for catalytic degradation of VOCs. DETAILED DESCRIPTION

[0013] Example 1

[0014] Follow the steps below to process:

[0015] (1) Mechanochemical enhanced deconstruction of waste polishing powder: waste polishing powder, NaOH and deionized water are mixed, and the mixture is subjected to a mechanochemical reaction using a high-energy ball mill. After the mechanochemical reaction is completed, the mixture is rinsed with deionized water and filtered to obtain waste polishing powder deconstruction residue and filtrate 1. The reaction conditions for the mechanochemical enhanced deconstruction of waste polishing powder are as follows: the mass ratio of waste polishing powder to NaOH is 1:1 g / g, the mass ratio of waste polishing powder to deionized water is 2:1 g / g, the ball-to-material ratio is 1:15 g / g, the ball mill speed is 500 rpm, and the ball milling time is 2 hours.

[0016] (2) Acid leaching extraction of rare earth elements: The waste polishing powder decomposition residue obtained in step (1) is mixed with a hydrochloric acid solution, and an acid leaching reaction is carried out under heating and stirring conditions. After the reaction, solid-liquid separation is carried out and leaching residue and rare earth-containing leachate are obtained by filtration. The acid leaching reaction conditions are: the molar concentration of the hydrochloric acid solution is 4 mol / L, the solid-liquid ratio of the dried decomposition residue to the hydrochloric acid solution is 1:15 kg / L, the leaching temperature is 80°C, the leaching time is 3 hours, and the stirring rate is 600 rpm.

[0017] (3) Precipitation, separation and purification of complex salts of rare earth elements: the rare earth-containing leachate obtained in step (2) is mixed with Na2SO4, and a rare earth complex salt precipitation reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and filtration is performed to obtain CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate and filtrate 2; then the CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate is reacted with NaOH solution, and after the reaction is completed, solid-liquid separation is carried out to obtain filtrate 3 and rare earth hydroxide, which are then reacted with dilute nitric acid solution to convert into a La(NO3)3 / Ce(NO3)4 mixed solution, and finally dried under low temperature conditions to obtain a La(NO3)3 / Ce(NO3)4 solid product. The reaction conditions for the double salt precipitation, separation and purification are as follows: the mass ratio of sodium sulfate to rare earth leachate is 200 g / L, the reaction temperature is 95°C, the reaction time is 30 minutes, the molar concentration of the dilute nitric acid solution is 1.0 mol / L, the mass concentration of the NaOH solution is 50%, and the drying temperature of the La(NO3)3 / Ce(NO3)4 mixed solution is 80°C.

[0018] (4) Preparation of La2O3 / CeO2 catalyst by template method: A small amount of ethanol is added to the La(NO3)3 / Ce(NO3)4 solid product obtained in step (3) to dissolve it. The La(NO3)3 / Ce(NO3)4 solid product, ethanol solution and mesoporous SiO2 template are uniformly mixed and dried. The mixture is then calcined in a box furnace to form a La2O3 / CeO2 catalyst-supported SiO2 composite material. The La2O3 / CeO2 catalyst-supported SiO2 composite material reacts with a NaOH solution to remove the SiO2 template. The final product is separated by centrifugation and dried to obtain a La2O3 / CeO2 catalyst. The reaction conditions for preparing La2O3 / CeO2 catalyst by the template method are as follows: the mass ratio of La(NO3)3 / Ce(NO3)4 solid product to mesoporous SiO2 template is 3:1 g / g, the drying temperature of the mixture is 60°C, the calcination temperature is 900°C, and the insulation time is 2 hours; when removing the template, the molar concentration of the NaOH solution is 2 mol / L, the reaction temperature is 80°C, the reaction time is 72 hours, the centrifuge speed is 6000 rpm, the centrifugation time is 10 minutes, and the drying temperature of the final product La2O3 / CeO2 catalyst is 60°C.

[0019] ICP test results show that the recovery rate of rare earth lanthanum and cerium in the waste polishing powder is approximately 99.2%. The regenerated La2O3 / CeO2 catalyst was used for the thermal catalytic degradation of styrene. Degradation test results show that the resulting La2O3 / CeO2 catalyst has a catalytic efficiency of 99.3% for the treatment of styrene.

[0020] Example 2

[0021] Follow the steps below to process:

[0022] (1) Mechanochemical enhanced deconstruction of waste polishing powder: waste polishing powder, NaOH and deionized water are mixed, and the mixture is subjected to a mechanochemical reaction using a high-energy ball mill. After the mechanochemical reaction is completed, the mixture is rinsed with deionized water and filtered to obtain waste polishing powder deconstruction residue and filtrate 1. The reaction conditions for the mechanochemical enhanced deconstruction of waste polishing powder are as follows: the mass ratio of waste polishing powder to NaOH is 1:1 g / g, the mass ratio of waste polishing powder to deionized water is 2:1 g / g, the ball-to-material ratio is 1:15 g / g, the ball mill speed is 500 rpm, and the ball milling time is 2 hours.

[0023] (2) Acid leaching extraction of rare earth elements: The waste polishing powder decomposition residue obtained in step (1) is mixed with a hydrochloric acid solution, and an acid leaching reaction is carried out under heating and stirring conditions. After the reaction, solid-liquid separation is carried out, and leaching residue and rare earth-containing leachate are obtained by filtration. The acid leaching reaction conditions are: the molar concentration of the hydrochloric acid solution is 4 mol / L, the solid-liquid ratio of the dried decomposition residue to the hydrochloric acid solution is 1:15 kg / L, the leaching temperature is 60°C, the leaching time is 2 hours, and the stirring rate is 600 rpm.

[0024] (3) Precipitation, separation and purification of complex salts of rare earth elements: the rare earth-containing leachate obtained in step (2) is mixed with Na2SO4, and a rare earth complex salt precipitation reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and filtration is performed to obtain CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate and filtrate 2; then the CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate is reacted with NaOH solution, and after the reaction is completed, solid-liquid separation is carried out to obtain filtrate 3 and rare earth hydroxide, which are then reacted with dilute nitric acid solution to convert into a La(NO3)3 / Ce(NO3)4 mixed solution, and finally dried under low temperature conditions to obtain a La(NO3)3 / Ce(NO3)4 solid product. The reaction conditions for the double salt precipitation, separation and purification are as follows: the mass ratio of sodium sulfate to rare earth leachate is 200 g / L, the reaction temperature is 80°C, the reaction time is 20 minutes, the molar concentration of the dilute nitric acid solution is 1.0 mol / L, the mass concentration of the NaOH solution is 50%, and the drying temperature of the La(NO3)3 / Ce(NO3)4 mixed solution is 80°C.

[0025] (4) Preparation of La2O3 / CeO2 catalyst by template method: A small amount of ethanol is added to the La(NO3)3 / Ce(NO3)4 solid product obtained in step (3) to dissolve it. The La(NO3)3 / Ce(NO3)4 solid product, ethanol solution and mesoporous SiO2 template are uniformly mixed and dried. The mixture is then calcined in a box furnace to form a La2O3 / CeO2 catalyst-supported SiO2 composite material. The La2O3 / CeO2 catalyst-supported SiO2 composite material reacts with a NaOH solution to remove the SiO2 template. The final product is separated by centrifugation and dried to obtain a La2O3 / CeO2 catalyst. The reaction conditions for preparing La2O3 / CeO2 catalyst by the template method are as follows: the mass ratio of La(NO3)3 / Ce(NO3)4 solid product to mesoporous SiO2 template is 2:1 g / g, the drying temperature of the mixture is 60°C, the calcination temperature is 900°C, and the insulation time is 2 hours; when removing the template, the molar concentration of the NaOH solution is 2 mol / L, the reaction temperature is 80°C, the reaction time is 72 hours, the centrifuge speed is 6000 rpm, the centrifugation time is 10 minutes, and the drying temperature of the final product La2O3 / CeO2 catalyst is 60°C.

[0026] ICP test results show that the recovery rate of rare earth lanthanum and cerium in the waste polishing powder is approximately 98.5%. The regenerated La2O3 / CeO2 catalyst was used for the thermal catalytic degradation of styrene. Degradation test results show that the resulting La2O3 / CeO2 catalyst has a catalytic efficiency of 99.1% for the treatment of styrene.

[0027] Example 3

[0028] Follow the steps below to process:

[0029] (1) Mechanochemical enhanced deconstruction of waste polishing powder: waste polishing powder, NaOH and deionized water are mixed, and the mixture is subjected to a mechanochemical reaction using a high-energy ball mill. After the mechanochemical reaction is completed, the mixture is rinsed with deionized water and filtered to obtain waste polishing powder deconstruction residue and filtrate 1. The reaction conditions for the mechanochemical enhanced deconstruction of waste polishing powder are as follows: the mass ratio of waste polishing powder to NaOH is 1:1 g / g, the mass ratio of waste polishing powder to deionized water is 2:1 g / g, the ball-to-material ratio is 1:15 g / g, the ball mill speed is 500 rpm, and the ball milling time is 2 hours.

[0030] (2) Acid leaching extraction of rare earth elements: The waste polishing powder decomposition residue obtained in step (1) is mixed with a hydrochloric acid solution, and an acid leaching reaction is carried out under heating and stirring conditions. After the reaction, solid-liquid separation is carried out and leaching residue and rare earth-containing leachate are obtained by filtration. The acid leaching reaction conditions are: the molar concentration of the hydrochloric acid solution is 4 mol / L, the solid-liquid ratio of the dried decomposition residue to the hydrochloric acid solution is 1:15 kg / L, the leaching temperature is 70°C, the leaching time is 2.5 hours, and the stirring rate is 600 rpm.

[0031] (3) Precipitation, separation and purification of complex salts of rare earth elements: the rare earth-containing leachate obtained in step (2) is mixed with Na2SO4, and a rare earth complex salt precipitation reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and filtration is performed to obtain CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate and filtrate 2; then the CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate is reacted with NaOH solution, and after the reaction is completed, solid-liquid separation is carried out to obtain filtrate 3 and rare earth hydroxide, which are then reacted with dilute nitric acid solution to convert into a La(NO3)3 / Ce(NO3)4 mixed solution, and finally dried under low temperature conditions to obtain a La(NO3)3 / Ce(NO3)4 solid product. The reaction conditions for the double salt precipitation, separation and purification are as follows: the mass ratio of sodium sulfate to rare earth leachate is 200 g / L, the reaction temperature is 95°C, the reaction time is 30 minutes, the molar concentration of the dilute nitric acid solution is 1.0 mol / L, the mass concentration of the NaOH solution is 50%, and the drying temperature of the La(NO3)3 / Ce(NO3)4 mixed solution is 80°C.

[0032] (4) Preparation of La2O3 / CeO2 catalyst by template method: A small amount of ethanol is added to the La(NO3)3 / Ce(NO3)4 solid product obtained in step (3) to dissolve it. The La(NO3)3 / Ce(NO3)4 solid product, ethanol solution and mesoporous SiO2 template are uniformly mixed and dried. The mixture is then calcined in a box furnace to form a La2O3 / CeO2 catalyst-supported SiO2 composite material. The La2O3 / CeO2 catalyst-supported SiO2 composite material reacts with a NaOH solution to remove the SiO2 template. The final product is separated by centrifugation and dried to obtain a La2O3 / CeO2 catalyst. The reaction conditions for preparing La2O3 / CeO2 catalyst by the template method are as follows: the mass ratio of La(NO3)3 / Ce(NO3)4 solid product to mesoporous SiO2 template is 1:1 g / g, the drying temperature of the mixture is 80°C, the calcination temperature is 600°C, and the insulation time is 2 hours; when removing the template, the molar concentration of the NaOH solution is 2 mol / L, the reaction temperature is 80°C, the reaction time is 72 hours, the centrifuge speed is 6000 rpm, the centrifugation time is 10 minutes, and the drying temperature of the final product La2O3 / CeO2 catalyst is 60°C.

[0033] ICP test results show that the recovery rate of rare earth lanthanum and cerium in the waste polishing powder is approximately 98.7%. The regenerated La2O3 / CeO2 catalyst was used for the thermal catalytic degradation of styrene. Degradation test results show that the resulting La2O3 / CeO2 catalyst has a catalytic efficiency of 99.8% for the treatment of styrene.

[0034] Example 4

[0035] Follow the steps below to process:

[0036] (1) Mechanochemical enhanced deconstruction of waste polishing powder: waste polishing powder, NaOH and deionized water are mixed, and the mixture is subjected to a mechanochemical reaction using a high-energy ball mill. After the mechanochemical reaction is completed, the mixture is rinsed with deionized water and filtered to obtain waste polishing powder deconstruction residue and filtrate 1. The reaction conditions for the mechanochemical enhanced deconstruction of waste polishing powder are as follows: the mass ratio of waste polishing powder to NaOH is 1:1 g / g, the mass ratio of waste polishing powder to deionized water is 2:1 g / g, the ball-to-material ratio is 1:15 g / g, the ball mill speed is 500 rpm, and the ball milling time is 2 hours.

[0037] (2) Acid leaching extraction of rare earth elements: The waste polishing powder decomposition residue obtained in step (1) is mixed with a hydrochloric acid solution, and an acid leaching reaction is carried out under heating and stirring conditions. After the reaction, solid-liquid separation is carried out and leaching residue and rare earth-containing leachate are obtained by filtration. The acid leaching reaction conditions are: the molar concentration of the hydrochloric acid solution is 4 mol / L, the solid-liquid ratio of the dried decomposition residue to the hydrochloric acid solution is 1:15 kg / L, the leaching temperature is 90°C, the leaching time is 3 hours, and the stirring rate is 600 rpm.

[0038] (3) Precipitation, separation and purification of complex salts of rare earth elements: the rare earth-containing leachate obtained in step (2) is mixed with Na2SO4, and a rare earth complex salt precipitation reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and filtration is performed to obtain CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate and filtrate 2; then the CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate is reacted with NaOH solution, and after the reaction is completed, solid-liquid separation is carried out to obtain filtrate 3 and rare earth hydroxide, which are then reacted with dilute nitric acid solution to convert into a La(NO3)3 / Ce(NO3)4 mixed solution, and finally dried under low temperature conditions to obtain a La(NO3)3 / Ce(NO3)4 solid product. The reaction conditions for the double salt precipitation, separation and purification are as follows: the mass ratio of sodium sulfate to rare earth leachate is 200 g / L, the reaction temperature is 100°C, the reaction time is 60 minutes, the molar concentration of the dilute nitric acid solution is 1.0 mol / L, the mass concentration of the NaOH solution is 50%, and the drying temperature of the La(NO3)3 / Ce(NO3)4 mixed solution is 80°C.

[0039] (4) Template method for preparing La2O3 / CeO2 catalyst: a small amount of ethanol was added to the La(NO3)3 / Ce(NO3)4 solid product obtained in step (3) to dissolve it, and the La(NO3)3 / Ce(NO3)4 solid product, ethanol solution and mesoporous SiO2 template were uniformly mixed and dried, followed by calcination in a box furnace to form a La2O3 / CeO2 catalyst loaded SiO2 composite material. The La2O3 / CeO2 catalyst loaded SiO2 composite material was reacted with NaOH solution to remove the SiO2 template, and the final product was separated by centrifugation, and then dried to obtain the La2O3 / CeO2 catalyst. The reaction conditions for preparing the La2O3 / CeO2 catalyst by the template method are as follows: the mass ratio of the La(NO3)3 / Ce(NO3)4 solid product to the mesoporous SiO2 template is 2:1 g / g, the drying temperature of the mixture is 60°C, the calcination temperature is 900°C, and the holding time is 2 hours; when removing the template, the molar concentration of the NaOH solution is 2 mol / L, the reaction temperature is 90°C, the reaction time is 72 hours, the centrifuge speed is 6000 rpm, the centrifugation time is 10 minutes, and the drying temperature of the final product La2O3 / CeO2 catalyst is 60°C.

[0040] The ICP test results show that the recovery rate of rare earth lanthanum and cerium in the waste polishing powder is about 99.5%. The regenerated La2O3 / CeO2 catalyst is used for the thermal catalytic degradation of styrene, and the degradation test results show that the catalytic treatment efficiency of the obtained La2O3 / CeO2 catalyst for styrene can reach 99.5%.

Claims

1. A method for mechanochemically enhanced deconstruction and recovery of rare earths from waste polishing powder and high-quality regeneration of La2O3 / CeO2 catalyst for catalytic degradation of VOCs, characterized in that: The specific steps are as follows: (1) Mechanochemical enhanced decomposition of waste polishing powder: waste polishing powder, NaOH and deionized water are mixed, and the mixture is subjected to a mechanochemical reaction using a high-energy ball mill; after the mechanochemical reaction, the mixture is rinsed with deionized water and filtered to obtain waste polishing powder decomposition residue and filtrate 1; the reaction conditions for the mechanochemical enhanced decomposition of waste polishing powder are: the mass ratio of waste polishing powder to NaOH is 5:1 to 1:1 g / g, and the mass ratio of waste polishing powder to deionized water is 5:1 to 1:1 g / g; (2) Acid leaching extraction of rare earth elements: the waste polishing powder decomposition residue obtained in step (1) is mixed with a hydrochloric acid solution, and an acid leaching reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and leaching residue and rare earth-containing leachate are obtained by filtration; the acid leaching reaction conditions are: the molar concentration of the hydrochloric acid solution is 2 to 8 mol / L, the solid-liquid ratio of the dried decomposition residue to the hydrochloric acid solution is 1:10 to 1:20 kg / L, the leaching temperature is 60 to 90°C, the leaching time is 1 to 6 hours, and the stirring rate is 200 to 600 rpm; (3) Precipitation, separation and purification of complex salts of rare earth elements: the rare earth-containing leachate obtained in step (2) is mixed with Na2SO4, and a rare earth complex salt precipitation reaction is carried out under heating and stirring conditions. After the reaction is completed, solid-liquid separation is carried out, and filtration is performed to obtain CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate and filtrate 2; the CeNa(SO4)2 / LaNa(SO4)2 complex salt precipitate is then reacted with NaOH solution. After the reaction is completed, solid-liquid separation is performed to obtain filtrate 3 and rare earth hydroxide, which are then mixed with dilute nitrate to obtain filtrate 3. The acid solution is converted into a La(NO3)3 / Ce(NO3)4 mixed solution by reaction, and then dried to obtain a La(NO3)3 / Ce(NO3)4 solid product; the reaction conditions for the double salt precipitation separation and purification are: a mass ratio of sodium sulfate to rare earth leachate is 100-200 g / L, a double salt precipitation reaction temperature is 60-100°C, a double salt precipitation reaction time is 10-90 minutes, a molar concentration of the dilute nitric acid solution is 0.1-1.0 mol / L, and a mass concentration of the NaOH solution is 30%-50%; (4) Preparation of La2O3 / CeO2 catalyst by template method: adding ethanol to the La(NO3)3 / Ce(NO3)4 solid product obtained in step (3) to dissolve it, uniformly mixing the La(NO3)3 / Ce(NO3)4 solid product, ethanol solution and mesoporous SiO2 template, drying it, and then calcining it in a box furnace to form a La2O3 / CeO2 catalyst-loaded SiO2 composite material; reacting the obtained La2O3 / CeO2 catalyst-loaded SiO2 composite material with NaOH solution to remove the SiO2 template, and centrifuging to separate the final product, and finally After drying, a La2O3 / CeO2 catalyst is obtained; the reaction conditions for preparing the La2O3 / CeO2 catalyst by the template method are: the mass ratio of the La(NO3)3 / Ce(NO3)4 solid product to the mesoporous SiO2 template is 1:1-4:1, the calcination temperature is 600-900°C, and the insulation time is 1-4 hours; when removing the template, the molar concentration of the NaOH solution is 1-10 mol / L, the reaction temperature is 60-90°C, the reaction time is 24-72 hours, the centrifuge speed is 6000-10000 rpm, and the centrifugation time is 5-10 minutes.

2. The method according to claim 1, characterized in that In step (1), the ball-to-material ratio is 1:5 to 1:25 g / g, the ball mill speed is 200 to 800 rpm, and the ball milling time is 1 to 6 hours.

3. The method according to claim 1, characterized in that The drying temperature of the La(NO3)3 / Ce(NO3)4 mixed solution in step (3) is 60-100°C.

4. The method according to claim 1, wherein The drying temperature of the mixture in step (4) is 30-80°C.

5. The method according to claim 1, characterized in that The drying temperature of the final product La2O3 / CeO2 catalyst in step (4) is 30-80°C.

Images