Preparation method, product and application of heterogeneous persulfate activator FeLaO-bentonite

Abstract

The invention relates to a heterogeneous persulfate activator FeLaO-bentonite preparation method, a product and application, the heterogeneous persulfate activator FeLaO-bentonite is doped with rare earth metal La and is immobilized on carbon modified bentonite, the number of Fe active sites can be increased, and the structural stability of the activator can be enhanced through the synergistic effect of the rare earth metal La and the carbon modified bentonite; based on modification of a carbon material, the adsorption capacity of bentonite is improved, and the material is stable in framework structure and can be repeatedly used after being activated at high temperature. According to the method, the specific surface area is effectively increased, agglomeration of active components can be effectively avoided, a persulfate activator is stimulated to form more active oxygen species, removal of pollutants is accelerated, especially, the oxidation efficiency of hypophosphite is remarkable, the removal amount of total phosphorus is effectively promoted to reach 100%, and the method has the advantages of being efficient and controllable and has wide application prospects. And the sludge has a recycling value.

Description

Technical Field

[0001] The invention relates to a preparation method, product and application of a heterogeneous persulfate activator FeLaO@bentonite. The invention utilizes the synergistic effect between metals and immobilization treatment to further improve the activation efficiency of active species, accelerate the removal of total phosphorus in water, and is used in the field of sewage treatment. Background Art

[0002] Phosphorus is the main cause of eutrophication of water bodies. If the total phosphorus content in water bodies exceeds 0.2 mg / L, it will cause excessive reproduction of algae, causing aquatic organisms to suffocate and die due to lack of oxygen, seriously destroying the balance of the original water body. In addition, after the death of aquatic organisms, they will decompose and produce toxic and harmful gases, such as hydrogen sulfide, which will cause the water quality to deteriorate further. Comprehensive treatment of phosphorus-containing wastewater is crucial to the balance of the ecosystem and human health.

[0003] At present, the more common key technologies for phosphorus removal are mainly to use the chemical precipitation reaction of phosphorus to convert soluble phosphorus in sewage into insoluble phosphate precipitates, or to use biological phosphorus removal to absorb phosphorus into sludge, but this method has poor stability and is difficult to meet the primary emission standards. However, for electroplating wastewater, most of the phosphorus exists in a complexed form, and conventional chemical precipitation phosphorus removal cannot achieve the purpose of removal. Some studies have pointed out that the complexed phosphorus can be first oxidized and broken to form orthophosphate, and then a precipitant can be added to form an insoluble substance to achieve solid-liquid separation and achieve the goal of total phosphorus removal.

[0004] Advanced oxidation technology is a deep oxidation technology that can oxidize large molecular refractory organic matter into low-toxic or non-toxic small molecules by generating hydroxyl radicals with strong oxidizing properties. Free radicals can be generated in various ways, such as electricity, light, ultrasound, catalysts, etc. In recent years, with the deepening of research, persulfate advanced oxidation technology has attracted widespread attention from scientific researchers. Compared with hydroxyl radicals, sulfate radicals have higher redox potential, longer half-life and wider pH application range, and are called alternative technologies for hydroxyl radical advanced oxidation technology. This free radical can be generated by activating permonosulfate (PMS, redox potential of 2.01 V) and peroxydisulfate (PS, redox potential of 1.82 V), and its strong oxidizing property can be used to effectively oxidize and decompose organic pollutants. In the past few decades, people have explored a variety of methods for activating PS, among which energy activation (such as light, heat, ultrasound, electrochemistry and related combinations) is the most traditional, but the poor activation efficiency limits its practical promotion and application. At present, chemical activation of PS using catalysts is a more economical, faster and more effective strategy than other methods because of its simple process, eco-friendly, low energy consumption and recyclability. For the selection of catalysts, its stability and catalytic activity are the most important considerations. Among the many catalysts, Fe-based catalysts are favored because of their wide sources, low cost and simple process. However, when traditional Fe-based materials are directly used for PS activation, they will cause secondary water pollution and a decrease in catalytic activity due to metal dissolution. Therefore, the patent application enhances the synergistic effect between metal interfaces by doping with rare earth La, reduces the dissolution rate of metals, and improves the activation efficiency of persulfate activators. At the same time, in order to realize the recycling of the activator, it is fixed on bentonite, which can not only quickly separate the solid and liquid, but also increase the contact surface between the pollutants and the active components, further improving the oxidation efficiency of total phosphorus. Summary of the invention

[0005] The activation efficiency of Fe-based persulfate activators is poor, and the metal Fe species in the activator are dissolved during recycling, causing a significant decrease in activation efficiency, and secondary pollution of water quality is also caused. To this end, the present invention adopts the synergistic effect between metals to promote the improvement of stability, the introduction of rare earth metal La can also increase the formation of active sites, and promote the recycling of powder materials under the fixation of modified bentonite, which has great guiding significance for practical applications. The purpose of the present invention is to provide a preparation method of a heterogeneous persulfate activator FeLaO@bentonite.

[0006] Another object of the present invention is to provide a heterogeneous persulfate activator FeLaO@bentonite product prepared by the above method.

[0007] Another object of the present invention is to provide an application of the above product.

[0008] The purpose of the present invention is achieved by the following scheme: a heterogeneous persulfate activator FeLaO@bentonite, which utilizes the doping of rare earth metal La to cooperate with Fe species to promote the formation of active sites, and is immobilized on carbon-modified bentonite to not only effectively increase the specific surface area, but also effectively avoid the agglomeration of active components, which is conducive to stimulating the activation of persulfate to form more active oxygen species and accelerate the removal of pollutants, comprising the following steps: A method for preparing a heterogeneous persulfate activator FeLaO@bentonite, characterized in that rare earth metal La is doped to cooperate with Fe species to promote the formation of active sites, and the active sites are immobilized on carbon-modified bentonite, comprising the following steps: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder to bentonite, grind and mix, and then calcine in a muffle furnace at 90-150 °C for 1-3 h to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:(0.1-1), and NaOH was added to adjust the pH to 7-11 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution of (3) in a water bath at 60-90 °C, stir well and react for 0.5-2 h; (5) After the reaction is completed, the product is filtered, washed, dried, and calcined in a tubular furnace at 300-500 °C for 2-6 h to obtain FeLaO@bentonite persulfate activator.

[0009] In step (2), the mass ratio of bentonite to C3N4 is 100:(2-10), and the calcination temperature and time are 90-150°C and 1-3 h.

[0010] In steps (2) and (5), the calcination atmosphere is one of N2 or air.

[0011] The invention provides a heterogeneous persulfate activator FeLaO@bentonite obtained according to the method.

[0012] The invention also provides an application of a heterogeneous persulfate activator FeLaO@bentonite in removing total phosphorus in sewage.

[0013] The activation degradation performance test of FeLaO@bentonite activator was carried out in a beaker. 100 mg of activator was added to 100 mL of 100 mg / L hypophosphite wastewater, and 5 mM potassium persulfate was added. The reaction was stirred for 15 minutes, and the supernatant was taken by centrifugation. A certain amount of CaO was added, and the mixture was stirred thoroughly. The pH was adjusted to about 8, and the supernatant was taken by centrifugation. The oxidation efficiency of the activator on hypophosphite was determined, and the removal rate of total phosphorus was calculated.

[0014] The doping of the rare earth metal La in the present invention not only helps to increase the number of Fe active sites, but also the synergistic effect between the two can enhance the structural stability of the activator. Furthermore, based on the modification of the carbon material, the adsorption capacity of bentonite is increased, the skeleton structure of the material is stable, and it can be reused many times after high-temperature activation. Compared with the prior art, the activator disclosed in the present invention can quickly stimulate the decomposition of persulfate to produce strong oxidizing active oxygen species, has a significant oxidation efficiency for hypophosphorous, effectively promotes the removal of total phosphorus to 100%, and has the characteristics of high efficiency and controllability.

[0015] The present invention has the following advantages: (1) The present invention proposes a preparation method and application of a heterogeneous persulfate activator FeLaO@bentonite, which uses modified porous bentonite as a substrate and uses a one-pot method to synthesize a loaded FeLaO@bentonite material. The synergistic effect between the two metals accelerates the formation of active sites and enhances the stability of the activator structure, avoiding metal dissolution. Under the action of the carrier, the contact area between the pollutant and the activator and the persulfate can be increased, which is beneficial to promote the activation of persulfate to produce active oxygen species and shorten the activation reaction time.

[0016] (2) The heterogeneous persulfate activator FeLaO@bentonite proposed in the present invention utilizes the layered structure of C3N4 to modify bentonite, which not only effectively increases the specific surface area of ​​bentonite, but also the carbon-based material can effectively coat the FeLaO active species and enhance its structural stability.

[0017] (3) The FeLaO@bentonite activator proposed in the present invention not only has a wide range of raw material sources and is harmless to the environment, but also has a large specific surface area and a stable structure, and is a persulfate activation material with excellent performance. DETAILED DESCRIPTION

[0018] The present invention is further described by way of examples.

[0019] In the following examples, the calcination atmosphere is not specified, that is, the calcination atmosphere is air.

[0020] Example 1 A heterogeneous persulfate activator FeLaO@bentonite is prepared by using rare earth metal La doping to cooperate with Fe species to promote the formation of active sites and immobilizing it on carbon-modified bentonite according to the following steps: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder with a mass ratio of 100:5 to bentonite, grind and mix, and then place in a muffle furnace for roasting at 90°C for 1 hour to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:1, and NaOH was added to adjust the pH to 8 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution of (3) in a 60°C water bath and stir thoroughly for 2 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in a N2 atmosphere at 500°C for 2 h to obtain FeLaO@bentonite persulfate activator.

[0021] The removal rate of total phosphorus by the prepared persulfate activator is 90%.

[0022] Example 2 A heterogeneous persulfate activator FeLaO@bentonite is prepared in the following steps similar to those in Example 1: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder in a mass ratio of 100:10 to bentonite, grind and mix, place in a muffle furnace, and calcine at 110°C for 2 hours to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:0.5, and NaOH was added to adjust the pH to 9 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution of (3) in a water bath and stir thoroughly at 80°C for 2 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in a N2 atmosphere at 500°C for 2 h to obtain FeLaO@bentonite persulfate activator.

[0023] The removal rate of total phosphorus by the prepared persulfate activator is 100%.

[0024] Example 3 A heterogeneous persulfate activator FeLaO@bentonite is prepared in the following steps similar to those in Example 1: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder in a mass ratio of 100:10 to bentonite, grind and mix, place in a muffle furnace, and calcine at 110°C for 2 hours to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:1, and NaOH was added to adjust the pH to 9 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution in (3) under a water bath and stir thoroughly at 80°C for 2 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in an air atmosphere at 400°C for 4 h to obtain FeLaO@bentonite persulfate activator.

[0025] The removal rate of total phosphorus by the prepared persulfate activator is 97%.

[0026] Example 4 A heterogeneous persulfate activator FeLaO@bentonite is prepared in the following steps similar to those in Example 1: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder with a mass ratio of 100:2 to bentonite, grind and mix, and then place in a muffle furnace for roasting at 100°C for 2h to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:0.5, and NaOH was added to adjust the pH to 9 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution in (3) at 60°C in a water bath and stir thoroughly for 0.5 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in an air atmosphere at 350°C for 4 h to obtain FeLaO@bentonite persulfate activator.

[0027] The removal rate of total phosphorus by the prepared persulfate activator was 87%.

Claims

1. A method for preparing a heterogeneous persulfate activator FeLaO@bentonite, characterized in that: The method utilizes the doping of rare earth metal La to cooperate with Fe species to promote the formation of active sites and immobilize them on carbon-modified bentonite, including the following steps: (1) Place the bentonite sieved with 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) adding C3N4 powder to bentonite, wherein the mass ratio of the bentonite to C3N4 is 100:(2-10), grinding and mixing, placing in a muffle furnace, and roasting at 90-150°C for 1-3 h to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:(0.1-1), and NaOH was added to adjust the pH to 7-11 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution of (3) in a water bath at 60-90 °C, stir well and react for 0.5-2 h; (5) After the reaction is completed, the product is filtered, washed, dried, and calcined in a tubular furnace at 300-500 °C for 2-6 h to obtain FeLaO@bentonite persulfate activator.

2. The method for preparing a heterogeneous persulfate activator FeLaO@bentonite according to claim 1, characterized in that: The calcining atmosphere is one of N2 or air.

3. The method for preparing a heterogeneous persulfate activator FeLaO@bentonite according to claim 1 or 2, characterized in that: Prepare as follows: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder with a mass ratio of 100:5 to bentonite, grind and mix, and then place in a muffle furnace for roasting at 90°C for 1 hour to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:1, and NaOH was added to adjust the pH to 8 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution of (3) in a 60°C water bath and stir thoroughly for 2 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in a N2 atmosphere at 500°C for 2 h to obtain FeLaO@bentonite persulfate activator.

4. The method for preparing a heterogeneous persulfate activator FeLaO@bentonite according to claim 1 or 2, characterized in that: Prepare as follows: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder in a mass ratio of 100:10 to bentonite, grind and mix, place in a muffle furnace, and calcine at 110°C for 2 hours to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:0.5, and NaOH was added to adjust the pH to 9 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution of (3) in a water bath and stir thoroughly at 80°C for 2 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in a N2 atmosphere at 500°C for 2 h to obtain FeLaO@bentonite persulfate activator.

5. The method for preparing a heterogeneous persulfate activator FeLaO@bentonite according to claim 1 or 2, characterized in that: Prepare as follows: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder in a mass ratio of 100:10 to bentonite, grind and mix, place in a muffle furnace, and calcine at 110°C for 2 hours to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:1, and NaOH was added to adjust the pH to 9 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution in (3) under a water bath and stir thoroughly at 80°C for 2 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in an air atmosphere at 400°C for 4 h to obtain FeLaO@bentonite persulfate activator.

6. The method for preparing a heterogeneous persulfate activator FeLaO@bentonite according to claim 1 or 2, characterized in that: Prepare as follows: (1) Place bentonite of about 100 mesh in a muffle furnace and roast for 2 hours. After cooling, sieve it for later use; (2) Add C3N4 powder with a mass ratio of 100:2 to bentonite, grind and mix, and then place in a muffle furnace for calcination at 100°C for 2h to obtain carbon-modified bentonite; (3) Under magnetic stirring, Fe(NO3)3·9H2O and La(NO3)3·6H2O were dissolved in deionized water at a Fe / La molar ratio of 1:0.5, and NaOH was added to adjust the pH to 9 to obtain a mixed solution; (4) Add the carbon-modified bentonite to the mixed solution in (3) at 60°C in a water bath and stir thoroughly for 0.5 h; (5) After the reaction is completed, the product is filtered and washed, and then dried and placed in a tubular furnace for calcination in an air atmosphere at 350°C for 4 h to obtain FeLaO@bentonite persulfate activator.

7. A heterogeneous persulfate activator FeLaO@bentonite, characterized in that Prepared according to any one of claims 1 to 6.

8. Use of the heterogeneous persulfate activator FeLaO@bentonite according to claim 7 in removing total phosphorus from sewage.