CN113559901A

CN113559901A - A kind of preparation method of silicon and rare earth modified Fe3C catalyst

Info

Publication number: CN113559901A
Application number: CN202110901368.5A
Authority: CN
Inventors: 郭瑞; 张圣琦; 刘宣文; 苏娜
Original assignee: Northeastern University Qinhuangdao
Current assignee: Northeastern University Qinhuangdao
Priority date: 2021-08-06
Filing date: 2021-08-06
Publication date: 2021-10-29

Abstract

The invention relates to a preparation method of a silicon and rare earth modified Fe ₃ C catalyst, belonging to the technical field of refractory wastewater treatment, in particular to a preparation method of a Si and Ce modified Fe ₃ C catalyst. The invention provides a preparation method of Si and Ce modified Fe ₃ C catalyst. The present invention includes the following steps: Step 1) Dissolving the carbon source compound, the iron source compound and the rare earth nitrate in methanol respectively, then pouring the methanol solution of the iron source compound and the rare earth nitrate into the methanol solution of the carbon source compound, and stirring continuously to form The purple solution is heated to evaporate the solvent, and dried in an oven overnight to obtain a black-purple viscous foamy substance, which is the rare earth, iron-carbon source compound precursor; step 2) The dried rare earth, iron-carbon source compound precursor and The silicon powder is mixed and ground to make the two evenly mixed, which is the precursor of silicon, rare earth, iron-carbon source compound.

Description

Silicon and rare earth modified Fe3Preparation method of C catalyst

Technical Field

The invention belongs to the technical field of treatment of refractory wastewater, and particularly relates to Si and Ce modified Fe₃And C, a preparation method of the catalyst.

Background

The high-concentration degradation-resistant organic wastewater relates to a wide range of industries, such as printing and dyeing, pharmacy, chemical industry and the like, and the quality of the generated wastewater has the following characteristics: (1) COD_CrHigh concentration of BOD₅The concentration is low. Such as average effluent COD of main section of pharmaceutical wastewater_Cr5000-60000 mg/L and BOD₅Is only 750-10800 mg/L. COD of printing and dyeing wastewater_CrUp to 2000-5000 mg/L, and BOD₅Is only 800-1500 mg/L. (2) Many substances are toxic or difficult to degrade. (3) The pH change is large. The pH difference of waste water generated by different industries is large. The pH value of the printing and dyeing wastewater is generally 9-12; the pH value of the petrochemical wastewater is lower and is generally 3-5. (4) The nitrogen and phosphorus content of partial wastewater is high. (5) The salt content is high. (6) The water quality and the water quantity have large fluctuation. The discharge of high-concentration refractory organic wastewater is often related to the off-season vigorous season of the industry, the water quantity of each section during production is related, the process control difficulty is high, the impact load of a structure is large, and the ideal effect is difficult to achieve.

Conventional treatment processes may be classified into physical treatment techniques, chemical treatment techniques, and biochemical treatment techniques according to the treatment mechanism. Conventional physical treatment techniques include four broad categories of adsorption, membrane separation techniques, thermal evaporation techniques, and combination processes formed by both techniques. The biochemical technology comprises common activated sludge technology, anaerobic method, aerobic method, A/O technology, A2/O technology, biological aerated filter and the like. The most widely used chemical treatment techniques are the advanced oxidation techniques: such as fenton oxidation, catalytic oxidation, wet oxidation, ozone oxidation, supercritical oxidation, and the like. The advanced oxidation method takes hydroxyl free radicals with strong oxidation activity as marks, and directly mineralizes refractory substances in the sewage through the action modes of electricity, sound, light irradiation, catalysts and the like, or degrades macromolecular substances into micromolecular refractory substances by utilizing the strong oxidation of the free radicals, so that the biodegradability of the sewage is improved. The oxidation method with strong oxidation capacity can also be used for advanced treatment of organic wastewater difficult to degrade, has strong oxidation capacity, high degradation efficiency and no secondary pollution, and becomes a research hotspot at present in the industrialized application of the method. The oxidation method is adopted to effectively treat the wastewater, so that a catalyst with good use effect is needed.

Disclosure of Invention

Aiming at the problems, the invention provides Si and Ce modified Fe₃And C, a preparation method of the catalyst.

In order to achieve the purpose, the invention adopts the following technical scheme, and the invention comprises the following steps:

step 1) respectively dissolving a carbon source compound, an iron source compound and rare earth nitrate in methanol, pouring the methanol solution of the iron source compound and the rare earth nitrate into the methanol solution of the carbon source compound, continuously stirring to form a purple solution, heating to evaporate the solvent, and drying in an oven overnight to obtain a black purple viscous foam material which is a precursor of the rare earth and the iron-carbon source compound;

step 2) mixing and grinding the dried rare earth and iron-carbon source compound precursors and silicon powder to uniformly mix the dried rare earth and iron-carbon source compound precursors and the silicon powder to obtain silicon, rare earth and iron-carbon source compound precursors;

step 3) calcining the precursor of the silicon, rare earth and iron-carbon source compound at high temperature in a flowing nitrogen atmosphere to obtain Si and rare earth modified Fe with porous structures₃And C, a catalyst.

As a preferable scheme, the rare earth nitrate is cerium nitrate or lanthanum nitrate.

As another preferred scheme, the Si and Ce modified Fe of the invention₃The content of silicon in the catalyst C is 10-20 wt%, and the content of cerium is 10-20 wt%.

As another preferred scheme, the carbon source compound is 2-methylimidazole, dicyandiamide or melamine.

As another preferable scheme, the iron source compound of the invention adopts ferric trichloride, ferric nitrate, ferric sulfide or ferric ammonium citrate.

As another preferred scheme, in the step 1), 2-methylimidazole, ferric trichloride and cerous nitrate are respectively dissolved in methanol, then the methanol solution of ferric trichloride and cerous nitrate is poured into the methanol solution of 2-methylimidazole, the mass ratio of cerous nitrate to ferric trichloride to 2-methylimidazole is 1:1:1-2:2:5, the mixture is continuously stirred to form a purple solution, the purple solution is heated to 75-85 ℃ to evaporate the solvent, and the purple thick foam material is dried in an oven at 90 ℃ overnight to obtain the black purple thick foam material, namely the cerium and iron-2-methylimidazole precursor.

As another preferred scheme, in the step 3) of the invention, the precursor of silicon, cerium and iron-2-methylimidazole is calcined at a high temperature of 1600-1800 ℃ for 1-3 hours in a flowing nitrogen atmosphere to obtain Si and Ce modified Fe₃C, a catalyst; the heating rate is 3-5 deg.C/min.

Secondly, the mass ratio of the cerous nitrate, the ferric trichloride and the 2-methylimidazole in the step 1) is 2:2: 5.

In addition, the calcining temperature in the step 3) is 1800 ℃, the calcining time is 2 hours, and the heating rate is 5 ℃/min.

The invention has the beneficial effects.

In the preparation process of the catalyst, iron ions and cerium ions in a methanol solution are subjected to electrostatic self-assembly and gradually gather around 2-methylimidazole, cross-linking is carried out in the methanol evaporation process to form a viscous cerium precursor, an iron-2-methylimidazole precursor, crystal water in the precursor is gradually lost in the high-temperature calcination process of the precursor in an inert gas atmosphere, 2-methylimidazole molecules are carbonized and wrapped around cerium and iron, and then an iron oxide core in the middle is slowly converted into iron carbide under the reduction action and the carburization action of outer-layer carbon at high temperature, so that the catalyst has good catalyst activity; the porous silicon coated on the outer layer forms a porous structure, which is beneficial to improving the specific surface area of the catalyst and can avoid the migration, aggregation and growth of active particles in the oxidation process of the catalyst.

Besides the function of protecting ion leakage, the porous silicon layer on the outer layer of the catalyst also modifies the surface of the active site of the catalyst, and shortens the effective action distance of hydroxyl radicals; the formed pore channel structure can effectively adjust the distribution of active sites and degradation products; the doped cerium element improves the circulation stability of the surface of the catalyst and improves the rapid and efficient oxidation of the refractory organic matters.

The catalyst obtained by the invention is Si and rare earth modified Fe₃The C porous structure has better catalyst stability, and the catalyst has higher oxidation rate due to stronger electronic effect near the surface active site, thereby having good industrial application prospect.

The method comprises the following steps of 1) carrying out electrostatic self-assembly to prepare an intermediate product, drying to obtain a porous organic polymer containing silicon, ferric trichloride and cerium nitrate, and carrying out high-temperature pyrolysis in an inert gas atmosphere by taking the porous organic polymer containing silicon, ferric trichloride and cerium nitrate as a precursor.

Drawings

The invention is further described with reference to the following figures and detailed description. The scope of the invention is not limited to the following expressions.

FIG. 1 shows Si and Ce modified Fe₃SEM image of catalyst C.

FIG. 2 shows Si and La-modified Fe₃SEM image of catalyst C.

FIG. 3 shows Si and Ce modified Fe obtained in example 3₃And C, a catalytic efficiency diagram of the catalyst on rhodamine B.

FIG. 4 shows Si and La-modified Fe obtained in example 4₃And C, a catalytic efficiency diagram of the catalyst on rhodamine B.

FIG. 5 is a schematic diagram of the structure of the Fenton-like reaction device for wastewater treatment according to the present invention.

FIG. 6 is a schematic view showing the construction of an electrocatalytic device for industrial wastewater treatment according to the present invention.

FIG. 7 is a schematic view showing the construction of an apparatus for treating wastewater using a photocatalytic reaction according to the present invention.

In fig. 5, 1 is an overflow alarm (if the overflow alarm gives an alarm, the waste water input pump at the previous stage is controlled to stop working), 2 is an overflow port, 3 is a water outlet safety valve, 4 is a water outlet (the water outlet is connected with the water inlet of the electro-catalytic device at the next stage), 5 is a safety valve (the safety valve 5 is an inspection valve, the equipment stops working, and is opened when water is discharged), 6 is a water inlet, 7 is a flow meter, 8 is a pump, 9 is a reaction chamber, and 10 is an outer circulation pipe.

In fig. 6, 21 is a water inlet, 22 is a water outlet, 23 is an anode plate, 24 is a cathode plate, 25 is a reaction tank, and 26 is an anode plate drainage port. The anode plate 23 can be welded with an anode plate power connector, and the cathode plate 24 can be welded with a cathode plate power connector.

In fig. 7, 31 is an overflow alarm, 32 is an overflow port, 33 is a water outlet safety valve, 34 is a water outlet, 35 is a safety valve, 36 is a water inlet, 37 is a flow meter, 38 is a water pump, 39 is a reaction vessel, 40 is an external circulation pipe, and 41 is a light emitting diode setting position.

FIG. 8 is a scanning electron microscope image of the cerium-doped modified SiC filler catalytic powder prepared in example 1.

FIG. 9 shows a degradation curve of modified SiC filler catalyzed powder with cerium doped rhodamine B prepared in example 2.

FIG. 10 shows a degradation curve of the SiC filler catalytic powder for degrading rhodamine B, which is prepared in example 3.

Fig. 8 shows the morphology, which is seen to be a nanosheet layer, which is beneficial to the occurrence of catalytic reaction and the improvement of catalytic efficiency. Fig. 9 and fig. 10 are degradation graphs of rhodamine B in a degradation dye, and the degradation performance of Ce not added is better than that of Ce added in the present embodiment, and we can see that the catalyst prepared in the present embodiment can have a good catalytic effect.

FIG. 11 is a schematic view showing the internal structure of an embodiment of the apparatus for treating wastewater according to the present invention using photocatalytic reaction.

Detailed Description

The invention takes 2-methylimidazole as a carbon source, ferric trichloride as an iron source, cerium nitrate as a cerium source and porous silicon powder as a silicon source, and Si and Ce modified Fe is formed by pyrolysis and carbonization at high temperature₃C, a porous structure; the content of silicon is 10-20 wt%, and the content of cerium is 10-20 wt%.

Si and rare earth modified Fe₃Preparation of C catalystThe preparation method is a preparation method of the iron-based wear-resistant porous catalyst, and the iron base can be replaced by Al, transition metal or rare earth ions. The Ce of the present invention can be replaced by other rare earth metals, such as: lanthanum, praseodymium, neodymium and europium. The Si of the present invention may be replaced by other minor main group elements, such as N. Fe of the invention₃C may be replaced by other transition elements, such as Co, Ni, Cu.

Example 1 (Si, Ce modified Fe₃C catalyst)

Adding 0.5g of 2-methylimidazole and 0.2g of cerium nitrate into 100mL of methanol for dissolving to obtain a solution A, adding 0.2g of ferric trichloride into 100mL of methanol to obtain a solution B, respectively stirring until the solutions are completely dissolved, slowly pouring the solution B into the solution A to form a yellow solution, heating to 75 ℃ to evaporate the solvent, and drying in an oven at 90 ℃ overnight to obtain a black-orange yellow viscous foam material, namely an iron-2-methylimidazole precursor; mixing and grinding the dried iron-2-methylimidazole precursor and silicon powder to uniformly mix the dried iron-2-methylimidazole precursor and the silicon powder to obtain silicon and an iron-2-methylimidazole precursor; calcining the precursor of silicon and iron-2-methylimidazole at 1600 ℃ for 1 hour under the flowing nitrogen atmosphere to obtain Si modified Fe₃C, a catalyst; the heating rate is 3-5 deg.C/min. Fig. 1 is an SEM image of the resulting Si, Ce modified Fe3C catalyst. As can be seen from FIG. 1, the prepared catalyst is in a nanosheet structure, and Ce is uniformly dispersed in the nanosheet layer.

Example 2 (Si, La modified Fe₃C catalyst)

Dissolving 0.5g of 2-methylimidazole in 100mL of methanol solution to obtain a solution A, respectively adding 0.2g of ferric chloride and 0.2g of lanthanum nitrate into 100mL of methanol to obtain solutions B, respectively stirring until the solutions B are completely dissolved, slowly pouring the solution B into the solution A to form a purple solution, heating to 75-85 ℃, evaporating the solvent, and drying in an oven at 90 ℃ overnight to obtain a black-purple viscous foam material, namely a cerium precursor, iron-2-methylimidazole precursor; then mixing the cerium, iron-2-methylimidazole precursor and silicon powder, and calcining at 1800 ℃ for 1 hour under a flowing nitrogen atmosphere to obtain the prepared catalyst; the heating rate used was 3 ℃/min. FIG. 2 shows Si and La-modified Fe₃SEM image of catalyst C.

Example 3

Dissolving 0.5g of 2-methylimidazole in 100mL of methanol solution to obtain a solution A, respectively adding 0.2g of ferric trichloride and 0.2g of cerium nitrate into 100mL of methanol to obtain a solution B, respectively stirring until the solutions B are completely dissolved, slowly pouring the solution B into the solution A to form a purple solution, heating to 85 ℃, evaporating the solvent, and drying in an oven at 90 ℃ overnight to obtain a black-purple viscous foam material, namely a cerium, iron-2-methylimidazole precursor; mixing and grinding the dried cerium, iron-2-methylimidazole precursor and silicon powder to uniformly mix the cerium, iron-2-methylimidazole precursor and the silicon powder to obtain silicon, cerium and iron-2-methylimidazole precursor; calcining the precursor of silicon, cerium and ferrum-2-methylimidazole at the high temperature of 1500 ℃ for 3 hours in the flowing nitrogen atmosphere to obtain Si and Ce modified Fe₃C, a catalyst; the heating rate is 3-5 deg.C/min. The degradation curve of the prepared catalyst powder to rhodamine B is shown in figure 3.

Example 4 (Si, La modified Fe3C catalyst)

Dissolving 0.5g of 2-methylimidazole in 100mL of methanol solution to obtain a solution A, respectively adding 0.2g of ferric chloride and 0.2g of lanthanum nitrate into 100mL of methanol to obtain a solution B, respectively stirring until the solutions B are completely dissolved, slowly pouring the solution B into the solution A to form a purple solution, heating to 85 ℃, evaporating the solvent, and drying in an oven at 90 ℃ overnight to obtain a black-purple viscous foam material, namely a cerium, iron-2-methylimidazole precursor; then mixing the cerium, iron-2-methylimidazole precursor and silicon powder, and calcining at 1800 ℃ for 1 hour under a flowing nitrogen atmosphere to obtain the prepared catalyst; the heating rate used was 3 ℃/min. FIG. 4 is a degradation curve of the powder of the Si and La modified Fe3C catalyst for rhodamine B. As can be seen from FIG. 4, the degradation efficiency can reach more than 95% by using La as the catalyst for modification.

The silicon and rare earth modified Fe3C catalyst can be used as a Fenton catalyst to be applied to a similar Fenton reaction device for wastewater treatment.

As shown in the figure, the Fenton-like reaction device for wastewater treatment comprises a reaction cavity 9, wherein the lower part of the reaction cavity is connected with a transverse water inlet 6, the upper circulating port of the upper part of the reaction cavity 9 is connected with the upper end of an external circulating pipe 10, the lower circulating port of the lower end of the reaction cavity 9 is connected with the lower end of the external circulating pipe 10, the external circulating pipe 10 is connected with a pump 8, the upper part of the reaction cavity 9 is connected with a transverse water outlet 4, and the upper end of the reaction cavity 9 is provided with a transverse overflow port 2.

The reaction cavity of the Fenton-like reaction device for wastewater treatment is connected with an external circulation pipe and a pump, and the reciprocating circulation of wastewater in the reaction cavity can be realized through the pump, so that industrial wastewater is catalyzed for multiple times, and the expected degradation efficiency is achieved.

H can be added into the water inlet 6₂O₂。

The water inlet 6 is provided with a flowmeter 7 and a water inlet safety valve, and the water outlet 4 is provided with a water outlet safety valve 3. The flow rate of the industrial wastewater can be controlled by the water outlet safety valve 3 according to the flow meter 7.

The external circulation pipe 10 comprises an upper horizontal pipe, a vertical pipe and a lower horizontal pipe, the inner end of the upper horizontal pipe is connected with the reaction cavity 9, the outer end of the upper horizontal pipe is connected with the upper end of the vertical pipe, the lower end of the vertical pipe is connected with the outer end of the lower horizontal pipe, the inner end of the lower horizontal pipe is connected with a circulation lower port, and the pump 8 is connected to the vertical pipe.

An overflow alarm 1 (a floating ball electronic contact alarm can be adopted) is arranged at the overflow port 2. When the industrial wastewater in the reaction cavity 9 is excessive, an alarm can be given in time.

And filter screens are arranged at the water inlet 6, the water outlet 4, the circulating upper opening and the circulating lower opening.

The filter screen adopts 200 mesh filter screens. The adoption of a 200-mesh filter screen can effectively prevent the outflow of the Fenton-like catalyst.

The reaction chamber 9 comprises a cylinder, the lower end of the cylinder is of an arc structure (namely a funnel-shaped structure) with a convex middle part, and the water inlet 6 is arranged in the middle of the arc structure.

The upper end of the reaction cavity is provided with a cover plate; the entry of impurities is avoided.

The lower circulating port is connected with the lower end of the external circulating pipe 10 through a three-way pipe, the lower circulating port is connected with the vertical upper port of the three-way pipe, the transverse port in the middle of the three-way pipe is connected with the lower end of the external circulating pipe 10, and a safety valve 5 is arranged at the vertical lower port of the three-way pipe (the COD in the wastewater can be measured by manual sampling in the process of treating the wastewater at each stage, and if the COD in the wastewater does not reach the standard, the COD in the wastewater does not enter a lower-stage catalytic device, namely the safety valve is not opened).

The water outlet 4 and the overflow port 2 form an included angle of 90 degrees, the external circulation pipe and the overflow port 2 are arranged on the opposite sides, the water inlet 6 and the water outlet 4 are arranged on the opposite sides, and the upper circulation port is lower than the water outlet 4.

When the reactor is used, industrial wastewater flows into the Fenton-like reaction device, the inflow amount is controlled at any time through the flowmeter, and the industrial wastewater can fully react with the Fenton-like catalyst (the Fenton-like catalyst is arranged in the reaction cavity 9) through external circulation of the external circulation pipe for multiple times until the industrial wastewater reaches the discharge standard.

The Fenton-like reaction device for wastewater treatment can be matched with a device for treating wastewater by utilizing photocatalytic reaction and an electro-catalytic device for industrial wastewater treatment. The output end (i.e., the water outlet 4) of the Fenton-like reaction device for wastewater treatment of the present invention is connected to the input end (i.e., the water inlet 21) of the electro-catalytic device for industrial wastewater treatment, and the output end (i.e., the water outlet 22) of the electro-catalytic device for industrial wastewater treatment is connected to the input end (i.e., the water inlet 36) of the device for wastewater treatment using photocatalytic reaction.

The electro-catalytic device for industrial wastewater treatment comprises a reaction tank, wherein an anode reaction unit and a cathode reaction unit are arranged in the reaction tank, and a water inlet and a water outlet are formed in the reaction tank.

Treating the wastewater with an electrocatalysis device for industrial wastewater treatment, coating a cathode plate and an anode plate with a catalyst (the catalyst can be treated on the cathode plate and the anode plate by a hydrothermal method or an electroplating method), participating in the reaction under the electrocatalysis condition, and utilizing residual H in a fenton reaction device₂O₂Decomposing organic substances. Effectively solves the defects of easy deposition of impurities and organic carbon deposition on the surface of the anode electrode caused by incomplete wastewater treatment, improves the water treatment effect, particularly enhances the treatment effect on high-concentration organic wastewater, and has low power consumption and low cost.

The anode reaction unit is formed by connecting a plurality of anode plates in parallel, and the cathode reaction unit is formed by connecting a plurality of cathode plates in parallel.

The water inlet and the water outlet are arranged on opposite sides, the water inlet is arranged at the lower end of the reaction tank, and the water outlet is arranged at the upper end of the reaction tank.

The negative plates and the positive plates are alternately arranged to divide the reaction tank into a plurality of independent areas, and drainage ports are formed in the negative plates and the positive plates. The design of the alternate spacing of the plurality of electrode plates of the electrolytic cell (reaction cell) leads to the reduction of the surface spacing between the cathode and the anode, thereby increasing the surface current density of the electrolytic cell and further improving the decomposition efficiency of the wastewater.

The metal plate (the pole plate in the reaction tank) adopted by the invention can adopt high-entropy alloy after rapid laser etching, the components of the high-entropy alloy are quaternary Co, Cr, Fe and Mn, the components of the alloy are alloy components with equal molar ratio, the laser power is 5-20W, the spot diameter is 10-50um, the scanning speed is 100-500 mm/s. The novel multifunctional metal plate is made of laser-etched high-entropy alloy, and compared with the traditional metal plate, the high-entropy alloy plate prepared by the method has the advantages of self-cleaning, corrosion resistance, wear resistance, good electrochemical performance and the like, and is used for industrial wastewater degradation. For the metal plate, some new experiments were proposed to see where the supplementation was more appropriate.

The water inlet and the water outlet are arranged on two sides of the reaction tank in the length direction, the water inlet and the water outlet are transverse ports, the side orientations of the water inlet and the water outlet are consistent with the length direction of the reaction tank, the negative plate and the positive plate are arranged in parallel along the length direction of the reaction tank, and the length direction of the reaction tank is perpendicular to the plane where the polar plates are located.

The external power supply of the cathode plate and the anode plate can adopt 0-30V direct current.

The number of the cathode plates and the number of the anode plates are four. The number of plates can be adjusted according to the concentration of reactants and the product.

The cathode plate is an aluminum plate loaded with a catalyst (a Fenton catalyst can be adopted).

The anode plate is a copper plate loaded with a catalyst (a Fenton catalyst can be adopted).

The upper left corner of the anode plate 23 is provided with a drainage port 26, and the lower right corner of the cathode plate 24 is provided with a drainage port; the drainage port and the water outlet pipe on the anode plate are arranged on the same side; the drainage port on the negative plate and the water inlet pipe are arranged on the same side. The design of the long symmetrical drainage openings of the cathode plate and the anode plate can ensure the continuous fluidity of the wastewater and increase the retention time of the wastewater, thereby improving the decomposition effect of the wastewater.

The water inlet is provided with a water inlet valve, and the water outlet is provided with a discharge valve.

And overflow ports 28 are arranged at the upper ends of the two sides of the reaction tank in the width direction.

The reaction tank is internally provided with vertical slots 27 corresponding to the polar plates, and the bottom of the reaction tank is provided with horizontal slots connected with the vertical slots for inserting the bottom ends of the polar plates. The slots are arranged, so that the polar plates can be conveniently disassembled and assembled, the polar plates are selected according to the type and the content of the waste water, for example, when the waste water amount is small, 2 groups of polar plates can be selected, and when the waste water COD content is high and the components are complex, different types of polar plates (for example, the Co, Cr, Fe and Mn quaternary high-entropy alloy polar plates, also can adopt Co, Cr, Fe, Mn and Al quinary high-entropy alloy polar plates, and are all equal-molar-ratio high-entropy alloy polar plates) can be changed.

The device for treating wastewater by utilizing photocatalytic reaction comprises a reaction vessel 39, wherein the lower part of the reaction vessel 39 is connected with a transverse water inlet 36, the upper circulating port of the upper part of the reaction vessel 39 is connected with the upper end of an external circulating pipe 40, the lower circulating port of the lower end of the reaction vessel 39 is connected with the lower end of the external circulating pipe 40, the external circulating pipe 40 is connected with a pump 38, the upper part of the reaction vessel 39 is connected with a transverse water outlet 34, and the upper end of the reaction vessel 39 is provided with a transverse overflow port 32; the inner wall of the reaction vessel is provided with a luminous part.

The light emitting component adopts a light emitting diode which is arranged on a magnetic base, the magnetic base is connected with the inner wall of the reaction vessel 39 in a magnetic adsorption way, and the light emitting diode irradiates the inside of the reaction vessel. The light-emitting diodes with different numbers and wavelengths can be arranged according to different components of the wastewater (wires can be arranged on the outer wall for power supply). The magnetic base is connected, so that the light-emitting diode is convenient to disassemble and assemble.

The light emitting component comprises a wide spectrum light source and an acute line light source which are arranged in a staggered mode from top to bottom. A broad spectrum light source is used to excite the photocatalyst 44 and a sharp line light source corresponds to the absorption spectrum of the organic components in the wastewater.

The wide spectrum light source 43 and the sharp line light source 42 are in a shape of a horizontal rod or a ring, the end part of the wide spectrum light source is connected with the inner wall of the reaction container 39, and the end part of the sharp line light source is connected with a bracket in the middle of the inner part of the reaction container 39; the photocatalyst is attached to the outside of the broad spectrum light source 43. A metal mesh 45 may be provided outside the broad spectrum light source 43, and the catalyst may be attached to the metal mesh by a coprecipitation method, an electroplating method, or an electrodeposition method. And the metal net is arranged, so that the catalyst is convenient to replace.

The metal net is arranged on the lamp tube and can be fixed on the lamp tube by a clamp and can be detached.

The external circulating pipe and the pump 38 are connected to the reaction vessel 39, so that the industrial wastewater can be catalyzed for multiple times to achieve the expected degradation efficiency.

The light emitting diode adopts a blue light diode. Light sources with wavelengths less than 460nm may be used.

The catalyst is placed in the reaction vessel and the wastewater enters and mixes with the catalyst.

The water inlet 36 is provided with a flowmeter 37, and the water outlet 34 is provided with a water outlet safety valve 33. The flow rate of the industrial wastewater can be controlled by the water outlet safety valve 33 according to the flow meter 37.

The external circulation pipe 40 comprises an upper horizontal pipe, a vertical pipe and a lower horizontal pipe, the inner end of the upper horizontal pipe is connected with the reaction vessel 39, the outer end of the upper horizontal pipe is connected with the upper end of the vertical pipe, the lower end of the vertical pipe is connected with the outer end of the lower horizontal pipe, the inner end of the lower horizontal pipe is connected with a circulation lower port, and the pump 38 is connected with the vertical pipe.

An overflow alarm 31 is arranged at the overflow port 32. When the industrial wastewater in the reaction container 39 is excessive, an alarm can be given in time.

And filter screens are arranged at the water inlet 36, the water outlet 34, the circulating upper port, the circulating lower port and the overflow port 32.

The water outlet 34 and the overflow port 32 are arranged at an angle of 90 degrees, the external circulation pipe and the overflow port 32 are arranged at the opposite sides, the water inlet 36 and the water outlet 34 are arranged at the opposite sides, and the upper circulation port is lower than the water outlet 34.

The filter screen adopts 200 mesh filter screens, effectively prevents the outflow of catalyst.

The reaction vessel 39 comprises a cylinder, and the lower end of the cylinder is of an arc structure with a downward convex middle part, namely a funnel shape.

The inner diameter of the external circulation pipe, the aperture of the circulation upper opening and the aperture of the circulation lower opening are equal and larger than the apertures of the water inlet and the water outlet; the contact frequency of the waste water and the catalyst is improved.

The plurality of light emitting diodes are uniformly distributed at the lower part of the reaction container 39 along the circumferential direction of the reaction container 39. The blue light source is illuminated at each corner, and the light source is uniform and sufficient.

The circulating upper opening is higher than the internal illumination type photodiode.

The lower circulating port is connected with the lower end of the external circulating pipe 40 through a three-way pipe, the lower circulating port is connected with the vertical upper port of the three-way pipe, the horizontal port in the middle of the three-way pipe is connected with the lower end of the external circulating pipe 40, and a safety valve 35 is arranged at the vertical lower port of the three-way pipe (in the process of treating wastewater at each stage, COD in the wastewater has a definite value, and if the COD in the wastewater does not reach the standard, the COD in the wastewater does not enter a lower device, namely the safety valve is not opened).

When the device is used, organic wastewater flows into the photocatalysis device, the inflow amount is controlled at any time through the flowmeter, and the organic wastewater can fully react with the photocatalyst through external circulation of the external circulation pipe for multiple times and the addition of a sufficient and uniform light source until the emission standard is reached.

The device for treating wastewater by utilizing photocatalytic reaction degrades organic matters in wastewater. Organic wastewater flows into a photocatalysis device, a photocatalyst is added, and under the irradiation of blue light, the organic wastewater is circulated for multiple times through external circulation until reaching the discharge standard, so that the degradation rate of organic matters can be accelerated in the whole process, and the energy utilization rate is greatly improved.

The device for treating waste water by utilizing the photocatalytic reaction is characterized in that an external circulating pipe is added on the outer wall of a reaction vessel, and a water suction pump is added on the external circulating pipe, so that the organic waste water can be circulated for multiple times, the reaction time is prolonged, the waste water is treated more thoroughly, and the energy utilization rate is improved.

Utilize the device of photocatalysis reaction processing waste water to set up the bottom in the reaction vessel into leaking hopper-shaped, the extrinsic cycle of being convenient for makes whole waste water all can carry out the extrinsic cycle, makes the reaction more abundant, conveniently gets rid of the surplus water in reaction chamber simultaneously.

The device for treating wastewater by utilizing photocatalytic reaction attaches the piece of internal-illuminated photodiode to the inner wall of the reaction cavity, so that the light source is sufficient, the illumination of each place is uniform, and the reaction efficiency is improved.

The flowmeter is arranged at the water inlet, so that the flowing amount of water can be known at any time, and the device is very convenient.

The overflow gap is provided with the overflow-proof alarm, when the water in the reaction container is too much and flows out of the overflow groove, the alarm is generated, and the safety is improved.

200-mesh membranes are arranged at the water outlet, the water inlet, the external circulation pipe opening and the overflow tank to prevent the photocatalyst in the reaction vessel from flowing out.

The photocatalyst can adopt rare earth modified SiC filler, and the preparation method of the rare earth modified SiC filler comprises the following steps:

step 1) respectively dissolving a biomass carbon source and a cerium source in an alcohol solution, continuously stirring and heating under a microwave condition to evaporate the solvent, ensuring high dispersion of cerium ions, and drying in an oven overnight to obtain a viscous foam material, namely a cerium-biomass carbon source precursor;

step 2) mixing and grinding the dried cerium-biomass carbon source precursor and silicon powder to uniformly mix the dried cerium-biomass carbon source precursor and the silicon powder to obtain silicon, cerium and biomass carbon source precursors;

and 3) calcining the silicon, cerium and biomass carbon source precursor at high temperature in a flowing nitrogen atmosphere to obtain the cerium modified SiC catalyst.

And 4) calcining the powder obtained after cooling in an oxygen environment to remove carbon, soaking in a NaOH solution, and washing with clear water to improve hydrophilicity.

Said step 1) is carried out by continuous stirring under microwave conditions and heating to 70-85 ℃ to evaporate the solvent, ensuring a high dispersion of cerium ions, and drying in an oven at 90 ℃ overnight.

Calcining the precursor of silicon, cerium and chitosan at 1600 ℃ for 1-3 hours in a flowing nitrogen atmosphere to obtain a cerium modified SiC catalyst; the heating rate is 3-15 deg.C/min.

Calcining the powder obtained after cooling in the step 4) for 1 hour at 300 ℃ in an oxygen environment to remove carbon, soaking the powder in a 1M NaOH solution for 1 hour, and washing the powder with clean water for 2 times to improve the hydrophilicity.

The silicon powder is porous silicon powder.

The content of cerium in the cerium modified SiC catalyst is 5-20 wt%.

And 3) calcining at high temperature for 1 hour at the heating rate of 3 ℃/min or 5 ℃/min.

The step 1) is carried out by continuously stirring under microwave conditions and heating to 70 ℃ to evaporate the solvent.

The biomass carbon source in the step 1) is chitosan or melamine or corn stigma or walnut diaphragma juglandis.

The cerium source in the step 1) is cerium nitrate or cerium chloride or cerium acetate.

The mass ratio of the cerium nitrate to the silicon powder to the chitosan is 2:2: 5.

In the preparation process of the rare earth modified SiC filler, cerium ions in an alcohol solution are gradually gathered around a biomass carbon source solution in an electrostatic self-assembly manner, cross-linking is carried out in the alcohol evaporation process to form a viscous cerium-biomass carbon source precursor, in the high-temperature calcination process of the precursor in an inert gas atmosphere, crystal water in the precursor is gradually lost, biomass molecules of the biomass carbon source are carbonized and wrapped around cerium, and wrapped porous silicon forms a porous structure, so that the specific surface area of a catalyst is improved, and the migration, aggregation and growth of active particles in the catalyst oxidation process can be avoided.

The porous silicon layer on the outer layer of the rare earth modified SiC filler catalyst has the function of protecting ion leakage, and also modifies the surface of the active site of the catalyst, thereby shortening the effective action distance of hydroxyl radicals; the formed pore channel structure can effectively adjust the distribution of active sites and degradation products; the doped cerium element improves the circulation stability of the surface of the catalyst and improves the rapid and efficient oxidation of the refractory organic matters.

As shown in the figure, the preparation method of the rare earth modified SiC filler comprises the following steps:

The silicon powder is porous silicon powder.

The content of cerium in the cerium modified SiC catalyst is 5-20 wt%.

The rare earth modified SiC filler can be used as a high-efficiency strong oxidation catalyst (can be used as a photocatalyst in a device for treating wastewater by using a photocatalytic reaction) and can be applied to treatment of high-concentration degradation-resistant industrial wastewater. The method can be used in the field of treatment of refractory wastewater, and is mainly applied to treatment of wastewater containing rhodamine B dye.

The rare earth modified SiC filler catalyst is obtained by taking biomasses such as chitosan and the like as a carbon source, taking raw materials with good solubility such as cerium nitrate and the like as a cerium source and silicon powder as a silicon source, carrying out electrostatic self-assembly to prepare an intermediate product, drying the intermediate product to obtain a porous organic polymer containing silicon and cerium nitrate, and carrying out high-temperature pyrolysis on the porous organic polymer containing silicon and cerium nitrate as a precursor in an inert gas atmosphere. The preparation method is simple, low in cost and easy for industrial production. The prepared catalyst has a porous structure and a large specific surface area, so that the oxidation efficiency of the wastewater difficult to degrade is remarkably improved, and the wastewater successfully reaches the discharge standard.

Example 1

Dissolving 0.5g of chitosan in 100mL of methanol solution to obtain solution A, adding 0.2g of cerium nitrate into 100mL of methanol to obtain solution B, respectively stirring until the solutions are completely dissolved, slowly pouring the solution B into the solution A to form yellow solution, continuously stirring under the microwave condition, heating to 70 ℃ to evaporate the solvent, ensuring high dispersion of cerium ions, and drying in an oven at 90 ℃ overnight to obtain a cerium-chitosan precursor;

mixing and grinding the dried cerium-chitosan precursor and silicon powder to uniformly mix the dried cerium-chitosan precursor and the silicon powder to obtain silicon, cerium and chitosan precursors; calcining the precursor of silicon, cerium and chitosan at 1600 ℃ for 1 hour under the flowing nitrogen atmosphere to obtain a cerium modified SiC catalyst; the heating rate used was 3 ℃/min. Calcining the obtained powder at 300 ℃ in an oxygen environment for 1 hour to remove carbon, soaking the powder in a 1M NaOH solution for 1 hour, and washing the powder with clean water for 2 times to improve the hydrophilicity. The morphology of the prepared powder is shown in figure 8. As can be seen from the figure, a platelet-shaped catalyst was prepared, the thickness of the platelet being only 50 nm.

Example 2

Dissolving 0.5g of chitosan in 100mL of methanol solution to obtain solution A, adding 0.2g of cerium acetate in 100mL of methanol to obtain solution B, respectively stirring until the solution B is completely dissolved, slowly pouring the solution B into the solution A to form yellow solution, continuously stirring under the microwave condition, heating to 70 ℃ to evaporate the solvent, ensuring high dispersion of cerium ions, and drying in an oven at 90 ℃ overnight to obtain a cerium-chitosan precursor;

mixing and grinding the dried cerium-chitosan precursor and silicon powder to uniformly mix the dried cerium-chitosan precursor and the silicon powder to obtain silicon, cerium and chitosan precursors; calcining the precursor of silicon, cerium and chitosan at 1600 ℃ for 1 hour under the flowing nitrogen atmosphere to obtain a cerium modified SiC catalyst; the heating rate adopted is 5 ℃/min. Calcining the obtained powder at 300 ℃ in an oxygen environment for 1 hour to remove carbon, soaking the powder in a 1M NaOH solution for 1 hour, and washing the powder with clean water for 2 times to improve the hydrophilicity. The degradation curve of the prepared catalyst powder to rhodamine B is shown in figure 9.

Example 3 (without addition of cerium)

Dissolving 0.5g of chitosan in 100mL of methanol solution to obtain solution A, continuously stirring under the microwave condition, heating to 70 ℃, evaporating the solvent, and drying in an oven at 90 ℃ overnight to obtain a chitosan precursor;

mixing and grinding the dried chitosan precursor and the silicon powder to uniformly mix the dried chitosan precursor and the silicon powder to obtain a silicon-chitosan precursor; calcining the dried silicon-chitosan precursor for 1 hour at 1600 ℃ under the flowing nitrogen atmosphere to obtain a catalyst; the heating rate adopted is 5 ℃/min. Calcining the obtained powder at 300 ℃ in an oxygen environment for 1 hour to remove carbon, soaking the powder in a 1M NaOH solution for 1 hour, and washing the powder with clean water for 2 times to improve the hydrophilicity. The degradation curve of the prepared catalyst powder to rhodamine B is shown in figure 10, and the embodiment without Ce has poor degradation effect on dye.

It should be understood that the detailed description of the present invention is only for illustrating the present invention and is not limited by the technical solutions described in the embodiments of the present invention, and those skilled in the art should understand that the present invention can be modified or substituted equally to achieve the same technical effects; as long as the use requirements are met, the method is within the protection scope of the invention.

Claims

1. a preparation method of silicon, rare earth modified Fe ₃ C catalyst, is characterized in that comprising the following steps:

Step 1) Dissolve the carbon source compound, iron source compound and rare earth nitrate in methanol respectively, then pour the methanol solution of the iron source compound and the rare earth nitrate into the methanol solution of the carbon source compound, continue stirring to form a purple solution and heat the solvent Evaporate and dry in an oven overnight to obtain a black-purple viscous foamy substance, which is a rare earth, iron-carbon source compound precursor;

Step 2) Mixing and grinding the dried rare earth, iron-carbon source compound precursor and silicon powder, so that the two are evenly mixed, that is, the silicon, rare earth, iron-carbon source compound precursor;

Step 3) Si, rare earth, and iron-carbon source compound precursors are calcined at high temperature in a flowing nitrogen atmosphere to obtain a Si, rare earth modified Fe ₃ C catalyst with a porous structure.

2 . The method for preparing a silicon and rare earth modified Fe ₃ C catalyst according to claim 1 , wherein the rare earth nitrate adopts cerium nitrate or lanthanum nitrate. 3 .

3. the preparation method of a kind of silicon, rare earth modified Fe ₃ C catalyst according to claim 1, it is characterized in that in Si, Ce modified Fe ₃ C catalyst the content of silicon is 10-20wt%, and the content of cerium is 10% -20wt%.

4 . The method for preparing a silicon and rare earth modified Fe ₃ C catalyst according to claim 1 , wherein the carbon source compound is 2-methylimidazole, dicyandiamide or melamine. 5 .

5 . The method for preparing a silicon and rare earth modified Fe ₃ C catalyst according to claim 1 , wherein the iron source compound adopts ferric chloride, ferric nitrate, ferric sulfide or ferric ammonium citrate. 6 .

6. the preparation method of a kind of silicon, rare earth modified Fe ₃ C catalyst according to claim 1 is characterized in that described step 1) 2-methylimidazole, ferric chloride and cerium nitrate are respectively dissolved in methanol , and then pour the methanol solution of ferric chloride and cerium nitrate into the methanol solution of 2-methylimidazole, the mass ratio of cerium nitrate, ferric chloride and 2-methylimidazole is 1:1:1-2 respectively :2:5, continue stirring to form a purple solution and heat it to 75-85 °C to evaporate the solvent, and dry it in an oven at 90 °C overnight to obtain a black-purple viscous foamy substance, which is the precursor of cerium, iron-2-methylimidazole body.

7. the preparation method of a kind of silicon, rare earth modified Fe ₃ C catalyst according to claim 1, is characterized in that described step 3) silicon, cerium, iron-2-methylimidazole precursor is in flowing nitrogen atmosphere Si and Ce modified Fe ₃ C catalysts are obtained by calcining at a high temperature of 1600-1800° C. for 1-3 hours; the heating rate used is 3° C./min-5° C./min.

8. the preparation method of a kind of silicon, rare earth modified Fe ₃ C catalyst according to claim 1, is characterized in that the mass ratio of described step 1) cerium nitrate, ferric chloride and 2-methylimidazole is 2: 2:5.

9. the preparation method of a kind of silicon, rare earth modified Fe ₃ C catalyst according to claim 1, is characterized in that described step 3) calcination temperature is 1800 ℃, calcination time is 2 hours, and heating rate is 5 ℃/min .