阅读说明：本技术 一种碘化银-氧化银-卤氧化铋-铁酸钴磁性可见光催化剂制备方法 (Preparation method of silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst ) 是由 张安超 周普阳 张新民 张立享 张丹 李海霞 陈国艳 孙志君 于 2020-06-10 设计创作，主要内容包括：本发明提供一种碘化银-氧化银-卤氧化铋-铁酸钴磁性可见光催化剂制备方法,包括：制备铁酸钴磁性微颗粒；制备卤氧化铋-铁酸钴微颗粒；根据卤氧化铋-铁酸钴微颗粒,制备磁性可见光催化剂碘化银-氧化银-卤氧化铋-铁酸钴；其中,卤氧化铋中的卤元素为氯元素、溴元素或碘元素。本发明所述碘化银-氧化银-卤氧化铋-铁酸钴磁性可见光催化剂制备方法比较简单、成本低廉,而且本发明所述制备方法制备的碘化银-氧化银-卤氧化铋-铁酸钴磁性可见光催化剂具有环境友好、成本低廉、光催化氧化活性高等特点,可广泛应用于大气污染防治领域。(The invention provides a preparation method of a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst, which comprises the following steps: preparing cobalt ferrite magnetic microparticles; preparing bismuth oxyhalide-cobalt ferrite microparticles; preparing a magnetic visible light catalyst silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite according to the bismuth oxyhalide-cobalt ferrite micro-particles; wherein the halogen element in the bismuth oxyhalide is chlorine element, bromine element or iodine element. The preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-induced photocatalyst is simple and low in cost, and the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-induced photocatalyst prepared by the preparation method has the characteristics of environmental friendliness, low cost, high photocatalytic oxidation activity and the like, and can be widely applied to the field of air pollution prevention and control.)

1. A preparation method of a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst is characterized by comprising the following steps:

step 1, preparing cobalt ferrite CoFe₂O₄Microparticles;

step 2, preparing cobalt ferrite CoFe according to the step 1₂O₄Preparation of bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Microparticles; wherein, X is chlorine element, bromine element or iodine element;

step 3, preparing bismuth oxyhalide-cobalt ferrite BiOX-CoFe according to the step 2₂O₄Preparing magnetic silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag from microparticles₂O-BiOX-CoFe₂O₄。

2. The method for preparing the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst according to claim 1, wherein the step 1 specifically comprises the following steps:

step 11, a mol of cobalt nitrate hexahydrate Co (NO)₃)₂·6H₂O and 2a moles of iron nitrate nonahydrate Fe (NO)₃)₃·9H₂Dissolving O in deionized water and uniformly stirring to obtain a first solution containing cobalt nitrate and ferric nitrate; wherein a is a real number;

step 12, dissolving 8a mol of sodium hydroxide into deionized water to obtain a sodium hydroxide solution;

step 13, slowly adding the sodium hydroxide solution prepared in the step 12 into the first solution under the action of a mechanical electric stirrer, and continuously stirring for 2 hours to obtain a second solution containing suspended particles; wherein the pH value of the second solution is maintained at 12-14;

step 14, placing the second solution in a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 12 hours at the heating temperature of 180 ℃ to obtain a third solution containing precipitates;

step 15, naturally cooling and filtering the third solution in sequence, washing the filtered first solid substance with water for 3-5 times, and then placing the first solid substance in an oven at 80 ℃ for vacuum drying for 24 hours to obtain a first dried product;

step 16, grinding and screening the first dried product in sequence to obtain cobalt ferrite CoFe₂O₄Microparticles.

3. The method for preparing the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst according to claim 1 or 2, wherein the step 2 specifically comprises the following steps:

step 21, dissolving b moles of bismuth nitrate pentahydrate into an aqueous solution containing glacial acetic acid, and uniformly stirring to obtain a bismuth nitrate solution under an acidic condition; wherein b is a real number;

22, mixing 0.05 b-0.75 b mol of cobalt ferrite CoFe₂O₄Adding the magnetic microparticles into a bismuth nitrate solution under an acidic condition, and continuously stirring for 30 minutes under the action of a mechanical stirrer to obtain a fourth solution;

23, dropwise adding the KX solution of the potassium halide with the mole of b into the fourth solution under the action of a mechanical electric stirrer, continuously stirring for 2 hours, standing for 12 hours, and filtering to obtain a second solid substance;

step 24, washing the second solid substance for 3-5 times by using a mixed solution of deionized water and ethanol, and then placing the washed second solid substance into a drying oven at the temperature of 60-70 ℃ for vacuum drying for 24-48 hours to obtain a second dried product;

step 25, sequentially grinding and screening the second dried product to obtain bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Microparticles.

4. The method for preparing the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst according to claim 3, wherein the bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄In microparticles, cobalt ferrite CoFe₂O₄The mass ratio of the bismuth oxyhalide to the bismuth oxyhalide BiOX is 0.05-0.5; wherein the mass unit is gram, and the mass ratio is not excessiveLines of the drawings.

5. The method for preparing the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst according to claim 3, wherein the step 3 specifically comprises the following steps:

step 31, mixing c mol of silver nitrate AgNO₃And 1.6 to 22c mol of bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Dispersing the microparticles in deionized water, and continuously stirring for 30 minutes under the action of a mechanical electric stirrer to obtain a fifth solution; wherein c is a real number;

step 32, dissolving c mol of sodium hydroxide into deionized water to obtain a sodium hydroxide solution;

step 33, under the action of a mechanical electric stirrer, slowly adding the sodium hydroxide solution prepared in the step 32 into the fifth solution, continuously stirring for 1 hour, then adding potassium iodide with the molar weight of 0.083-0.34 c, continuously stirring for 2 hours, and filtering to obtain a third solid substance; wherein the pH value of the fifth solution added with the sodium hydroxide is 12-14;

step 34, washing the third solid substance for 3-5 times by using a mixed solution of deionized water and ethanol, and then placing the washed third solid substance into a drying oven at the temperature of 60-70 ℃ for vacuum drying for 24-48 hours to obtain a third dried product;

step 35, grinding and screening the third dry product in sequence to obtain the magnetic visible light catalyst silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag₂O-BiOX-CoFe₂O₄。

6. The method for preparing the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light catalyst according to claim 5, wherein the magnetic visible-light catalyst silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag₂O-BiOX-CoFe₂O₄Medium, cobalt ferrite CoFe₂O₄The mass ratio of the bismuth oxyhalide to the bismuth oxyhalide BiOX is 0.05-0.5; silver oxide Ag₂The mass ratio of O to bismuth oxyhalide BiOX is 0.02-0.2; silver iodide AgI and silver oxide Ag₂Mass of OThe ratio is 0.1 to 1.0.

7. The method for preparing the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst as claimed in claim 2, wherein in step 13, the suspended particles comprise cobalt hydroxide and iron hydroxide; in step 14, the precipitate is cobalt ferrite.

Technical Field

The invention relates to a pollution prevention technology, in particular to a preparation method of a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst.

Background

Currently, mercury pollution has attracted a wide range of attention worldwide for its highly harmful nature. In actual production life, coal-fired power plants are the main source of artificial mercury emission. In China, about 38% of mercury pollution is related to coal burning. The mercury in the coal-fired flue gas is mainly elemental mercury Hg⁰Hg of bivalent mercury²⁺And particulate mercury Hg^pThree forms exist; wherein, the elementary mercury Hg⁰Low melting point, easy volatilization and difficult water solubility, and divalent mercury Hg²⁺And particulate mercury Hg^pIn contrast, elemental mercury Hg⁰More difficult to remove from the flue gas.

There are four main methods for mercury removal: the first is an adsorption method which adsorbs mercury using activated carbon or the like; but the adsorption capacity is limited, so the material cannot be used for a long time and is expensive; furthermore, the activated carbon injection technique also affects the value of fly ash recycling. The second is catalytic oxidation, i.e. metal oxides with HCl or O₂Combining elemental mercury Hg⁰Catalytic oxidation to divalent mercury Hg²⁺And the catalyst is removed by absorption liquid, and because the method needs to additionally add a demercuration device, the operation cost of a coal-fired power plant is increased, and the placement of the used catalyst is also a problem to be solved. The third method is a method using conventional pollutant removal equipment, and the method can remove bivalent mercury Hg by using a wet desulphurization and dust removal device²⁺And particulate mercury Hg^pHowever, this method is on Hg⁰The removal effect is very little. The fourth method is a method using a photocatalyst, which can excite and generate photo-generated electron-hole pairs e under the irradiation of visible light or ultraviolet light^--h⁺The photo-generated electron-hole pair can react with oxygen or water adsorbed on the surface of the photocatalyst to generate superoxide radicalSeed of Japanese apricot^·O₂ ^-Or hydroxy^·OH to remove elemental mercury Hg⁰(ii) a But the activity of the photo-generated electron hole pair is lower, the preparation cost of the photocatalyst is higher, and the recovery is difficult.

Therefore, in the prior art, the flue gas demercuration method has the problems of poor demercuration effect, high cost, complex operation and maintenance and the like.

Disclosure of Invention

In view of the above, the main object of the present invention is to provide a method for preparing a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible light catalyst, which has the advantages of good mercury removal effect, low cost and simple operation and maintenance.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst comprises the following steps:

step 1, preparing cobalt ferrite CoFe₂O₄Microparticles.

Step 2, preparing cobalt ferrite CoFe according to the step 1₂O₄Preparation of bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Microparticles; wherein, X is chlorine element, bromine element or iodine element.

Step 3, preparing bismuth oxyhalide-cobalt ferrite BiOX-CoFe according to the step 2₂O₄Preparing magnetic silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag from microparticles₂O-BiOX-CoFe₂O₄。

In summary, the preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst provides a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst for removing elemental mercury in flue gas by a wet method, the photocatalytic oxidation demercuration efficiency of the catalyst to elemental mercury is up to more than 90% under the irradiation of visible light, and the magnetic visible-light-driven photocatalyst has strong magnetic recovery capacity and can be used for multiple times. The preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-induced photocatalyst is simple and low in cost, and the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-induced photocatalyst prepared by the preparation method has the characteristics of environmental friendliness, low cost, high photocatalytic oxidation activity and the like.

Drawings

Fig. 1 is a general flow diagram of a preparation method of a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst according to the present invention.

Fig. 2 is a schematic structural diagram of an experimental bench required for evaluating the demercuration performance of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst.

Fig. 3 is a diagram of the demercuration efficiency obtained by using each magnetic visible light catalyst for demercuration in example three of the present invention.

Fig. 4 is a schematic diagram of a hysteresis loop measurement result in the preparation method of the silver iodide-silver oxide-bismuth oxyiodide-cobalt ferrite magnetic visible-light-driven photocatalyst of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Fig. 1 is a general flow diagram of a preparation method of a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst according to the present invention. As shown in fig. 1, the preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible light catalyst comprises the following steps:

step 1, preparing cobalt ferrite CoFe₂O₄Microparticles.

Step 2, preparing cobalt ferrite CoFe according to the step 1₂O₄Preparation of bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Microparticles; wherein, X is chlorine element, bromine element or iodine element.

Step 3, preparing bismuth oxyhalide-cobalt ferrite BiOX-CoFe according to the step 2₂O₄Preparing magnetic silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag from microparticles₂O-BiOX-CoFe₂O₄。

In a word, the preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst provides a silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst for removing elemental mercury in flue gas by a wet method, the photocatalytic oxidation demercuration efficiency of the catalyst to the elemental mercury is up to more than 90% under the irradiation of visible light, and the magnetic visible-light-driven photocatalyst has strong magnetic recovery capacity and can be used for multiple times. The preparation method of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-induced photocatalyst is simple and low in cost, and the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-induced photocatalyst prepared by the preparation method has the characteristics of environmental friendliness, low cost, high photocatalytic oxidation activity and the like.

In the present invention, the step 1 specifically includes the following steps:

step 11, a mol of cobalt nitrate hexahydrate Co (NO)₃)₂·6H₂O and 2a moles of iron nitrate nonahydrate Fe (NO)₃)₃·9H₂Dissolving O in deionized water and uniformly stirring to obtain a first solution containing cobalt nitrate and ferric nitrate; wherein a is a real number.

And step 12, dissolving 8a mol of sodium hydroxide into deionized water to obtain a sodium hydroxide solution.

Step 13, slowly adding the sodium hydroxide solution prepared in the step 12 into the first solution under the action of a mechanical electric stirrer, and continuously stirring for 2 hours to obtain a second solution containing suspended particles; wherein the pH value of the second solution is maintained at 12-14.

In the invention, the suspended particles comprise cobalt hydroxide and iron hydroxide which are generated by corresponding cobalt ions, iron ions and hydroxide radicals.

And step 14, placing the second solution into a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 12 hours at the heating temperature of 180 ℃ to obtain a third solution containing precipitates.

In the invention, the precipitate is cobalt hydroxide and cobalt ferrite obtained by oxidizing ferric hydroxide.

And step 15, naturally cooling and filtering the third solution in sequence, washing the first solid matter obtained by filtering for 3-5 times by using a mixture of absolute ethyl alcohol and water, and placing the washed precipitate in an oven at 80 ℃ for vacuum drying for 24 hours to obtain a first dried product.

Step 16, grinding and screening the first dried product in sequence to obtain the magnetic visible-light-driven catalyst cobalt ferrite CoFe₂O₄Microparticles.

In the present invention, the step 2 specifically includes the following steps:

step 21, dissolving b moles of bismuth nitrate pentahydrate into an aqueous solution containing glacial acetic acid, and uniformly stirring to obtain a bismuth nitrate solution under an acidic condition; wherein b is a real number.

22, mixing 0.05 b-0.75 b mol of cobalt ferrite CoFe₂O₄And adding the magnetic microparticles into the bismuth nitrate solution under the acidic condition, and continuously stirring for 30 minutes under the action of a mechanical stirrer to obtain a fourth solution.

And 23, dropwise adding the potassium halide KX solution with the b mol into the fourth solution under the action of a mechanical electric stirrer, continuously stirring for 2 hours, standing for 12 hours, and filtering to obtain a second solid substance.

And 24, washing the second solid substance for 3-5 times by using a mixed solution of deionized water and ethanol, and then placing the washed second solid substance into an oven at the temperature of 60-70 ℃ for vacuum drying for 24-48 hours to obtain a second dried product.

Step 25, sequentially grinding and screening the second dried product to obtain bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Microparticles.

In the present invention, bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄In microparticles, cobalt ferrite CoFe₂O₄The mass ratio of the bismuth oxyhalide to the bismuth oxyhalide BiOX is 0.05-0.5; wherein, the unit of mass is gram, and the mass ratio is dimensionless.

In the present invention, the step 3 specifically includes the following steps:

step 31, mixing c mol of silver nitrate AgNO₃And 1.6 to 22c mol of bismuth oxyhalide-cobalt ferrite BiOX-CoFe₂O₄Dispersing the microparticles in deionized water, and continuously stirring for 30 minutes under the action of a mechanical electric stirrer to obtain a fifth solution; wherein c is a real number.

Step 32, dissolving c mol of sodium hydroxide into deionized water to obtain a sodium hydroxide solution;

step 33, under the action of a mechanical electric stirrer, slowly adding the sodium hydroxide solution prepared in the step 32 into the fifth solution, continuously stirring for 1 hour, then adding potassium iodide with the molar weight of 0.083-0.34 c, continuously stirring for 2 hours, and filtering to obtain a third solid substance; wherein the pH value of the fifth solution added with the sodium hydroxide is 12-14.

Step 34, washing the third solid substance for 3-5 times by using a mixed solution of deionized water and ethanol, and then placing the washed third solid substance into a drying oven at the temperature of 60-70 ℃ for vacuum drying for 24-48 hours to obtain a third dried product;

step 35, grinding and screening the third dry product in sequence to obtain the magnetic visible light catalyst silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag₂O-BiOX-CoFe₂O₄。

The magnetic visible-light-driven photocatalyst silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite AgI-Ag₂O-BiOX-CoFe₂O₄Medium, cobalt ferrite CoFe₂O₄The mass ratio of the bismuth oxyhalide to the bismuth oxyhalide BiOX is 0.05-0.5; silver oxide Ag₂The mass ratio of O to bismuth oxyhalide BiOX is 0.02-0.2; silver iodide AgI and silver oxide Ag₂The mass ratio of O is 0.01 to 0.1.

In the invention, the amounts of the deionized water, the ethanol and the glacial acetic acid can be determined according to actual requirements.

Fig. 2 is a schematic structural diagram of an experimental bench required for evaluating the demercuration performance of the silver iodide-silver oxide-bismuth oxyhalide-cobalt ferrite magnetic visible-light-driven photocatalyst. As shown in fig. 2, the experimental bench used in the following examples of the present invention includes: a steel cylinder 1 for original flue gas source, a thermostatic water bath 3 equipped with elementary mercury permeation tube for adding mercury to original flue gas source part from the steel cylinder 1, for adding original flue gasThe device comprises a mixer 4 for mixing gas and mercury-containing flue gas, a flowmeter 2 for controlling the gas flow of the original flue gas correspondingly output to a thermostatic water bath 3 and the mixer 4 from a steel cylinder 1, a magnetic stirring water bath photocatalytic reactor 5 for allowing the flue gas to be treated output by the mixer 4 to enter reaction liquid containing a catalyst under the control of the flowmeter 2, uniformly stirring the reaction liquid and keeping the reaction liquid at a constant temperature, wherein the temperature in the magnetic stirring water bath photocatalytic reactor 5 is constant under the combined action of a thermocouple 7 and a circulating cooling water device 8; under the irradiation of visible light emitted by a visible light source 6, the flue gas to be treated and the reaction liquid are subjected to demercuration reaction in a magnetic stirring water bath photocatalytic reactor 5. The demercuration flue gas output by the magnetic stirring water bath photocatalytic reactor 5 enters a container 9 filled with 20% of sodium hydroxide solution in mass fraction, and the sodium hydroxide solution can absorb acid gas mixed in the demercuration flue gas; moreover, the sodium hydroxide absorption container 9 is provided with a bypass, SO that the detection of nitric oxide NO and sulfur dioxide SO is convenient₂Mass concentration of (d); removing water vapor carried in the demercuration flue gas by the low-temperature cooling tank 10; then, dividing the obtained relatively dry and clean demercuration flue gas into three paths through a four-way valve 11, wherein the first path is tested by an elemental mercury tester 12 and then is conveyed to an activated carbon adsorption bed 15, and meanwhile, the elemental mercury tester 12 uploads a test result to an upper computer 13 for recording and analyzing mercury concentration; the second path is directly sent to an activated carbon adsorption bed 15; the third path enters an activated carbon adsorption bed 15 after being subjected to component analysis by a flue gas analyzer 14; the activated carbon adsorption bed 15 further adsorbs mercury in the relatively dry and clean demercuration flue gas, and then discharges the demercuration flue gas to the atmospheric environment. Here, the elemental mercury tester 12 employs a German VM-3000 on-line mercury tester. The laboratory bench shown in fig. 2 is prior art and will not be described herein.

In this embodiment, the original flue gas is composed of N₂、O₂、CO₂、SO₂And NO; wherein N is₂、O₂And CO₂Being a basic smoke constituent, O₂And CO₂In a volume content of 6% and 12%, respectively, N₂Is the balance gas. The total flow of the original flue gas is 1.5 liters/min Hg⁰Is thick in massThe degree is 50 micrograms/meter³. The inside diameter of a reaction vessel in the magnetic stirring water bath photocatalytic reactor 5 is 10 cm, a visible light source of a fluorescent lamp with power of 11 watts is arranged in the reaction vessel, and the visible light source is arranged in a quartz glass sleeve pipe which is convenient for water cooling. The photocatalytic oxidation reaction liquid in the reaction container is formed by mixing a certain mass of visible light catalyst and 1 liter of deionized water. In addition, the bottom of the reactor is also provided with a gas distribution pipe so that the whole reaction vessel is uniformly filled with the original flue gas.

Hg before and after the on-line detection experiment by adopting a German VM-3000 mercury determinator⁰The mass concentration of the steam is adopted to obtain the mercury removal efficiency of the catalyst in real time, and the calculation formula of the mercury removal efficiency η is that η is equal to (1-C)_out/C_in) × 100, wherein C is_outAnd C_inRespectively is the Hg at the 5 outlet of the magnetic stirring water-bath photocatalytic reactor before and after adding the photocatalyst⁰Mass concentration of steam.