CN114939424A - Bimetallic charcoal catalyst, preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of advanced oxidation of wastewater, and in particular relates to a bimetallic biochar catalyst and a preparation method and application thereof. The bimetallic biochar catalyst of the invention is obtained from biochar loaded with nano-zero _- valent iron and MoS2 nanosheets, and the surface has a large number of metal active sites Fe(0), Fe(II), Mo(IV), Mo(V) ), which can increase the specific surface area and the number of mesopores of biochar materials, so the adsorption and catalytic performance are improved, which can be used to activate PMS to generate various reactive oxygen species (SO ₄ ^·‑ , ·OH, ¹ O ₂ , O ₂ ^{·‑ )} ) oxidation of organic refractory pollutants in wastewater; when applied to PMS advanced oxidation technology, Mo(IV) in the catalyst can reduce the Fe(III) generated in the system to Fe(II), which has an activating effect on persulfate. ), the activation efficiency of the catalyst to the persulfate is improved, and the efficient degradation of the organic pollutants in the organic waste water by the persulfate is realized; at the same time, the catalyst preparation method is simple, low in cost, and can be mass-produced in an industrialized manner.

Description

A kind of bimetallic biochar catalyst and preparation method and application

technical field

The invention belongs to the technical field of advanced oxidation of wastewater, and in particular relates to a bimetallic biochar catalyst and a preparation method and application thereof.

Background technique

With the development of industry, the problem of environmental pollution caused by organic wastewater is becoming more and more serious. Organic wastewater contains complex and refractory organic pollutants. Novel advanced oxidation technologies (SRAOPs) using sulfate radicals as the main active species are more and more widely used in the field of organic wastewater treatment due to their simplicity, short reaction time, and high degree of mineralization of organic pollutants.

Nano zero-valent iron (nZVI) is a zero-valent iron particle with a particle size of 1-100nm, which can slowly release Fe ²⁺ , and Fe ²⁺ can activate persulfate (such as peroxymonosulfate, PMS, peroxodisulfate ⁾ . PDS) produces sulfate radicals, so nano-zero valent iron has broad application prospects in PMS advanced oxidation technology. However, the highly active nano-zero-valent iron particles are easily oxidized in an aerobic environment and easily agglomerated in the liquid phase, which greatly limits the application of nano-zero-valent iron. Biochar (BC) has great potential in environmental governance due to its high stability, wide source of raw materials, simple preparation method, large specific surface area, and large adsorption capacity. There is also some degree of activation. Combining nano-zero-valent iron with biochar as a composite material can significantly improve the dispersibility of nano-zero-valent iron and the activation effect on persulfate.

Chinese dissertation (Xue Song. Research on the removal of organic pollutants by biochar-loaded nano-zero-valent iron [D]. Suzhou, Jiangsu: Suzhou Institute of Science and Technology, 2015) discloses a biochar-loaded nano-zero-valent iron, and its preparation method The method is as follows: adding biochar to the hydroalcoholic mixed solution of ferrous sulfate, stirring evenly, adding KBH ₄ solution dropwise at a uniform speed under nitrogen protection to carry out aging reaction, and separating, washing and drying to obtain the product after the reaction is completed. The biochar-loaded nano-zero-valent iron prepared by the method has good dispersibility, and is used in combination with sodium persulfate. When the carbon-iron mass ratio is optimal (5:1), the removal rate of trichloroethylene is as high as 99.4%.

However, for the above type of biochar/nano-zero valent iron catalytic system, in the process of activating persulfate, Fe ²⁺ is continuously oxidized to Fe ³⁺ , while Fe ³⁺ cannot activate persulfate, In addition, Fe ²⁺ in the solution will react with sulfate radicals, so the Fe ²⁺ concentration in the early stage of the activation reaction decreases rapidly and the reaction rate in the latter stage is extremely low, which is not conducive to the complete activation of the activation reaction and cannot promote persulfate. Complete removal of organic contaminants.

SUMMARY OF THE INVENTION

Aiming at the problem that the Fe ²⁺ released by the biochar/nano-zero-valent iron catalytic system in the process of activating persulfate is too fast to cause poor activation effect in the prior art, the present invention provides a bimetallic biochar catalyst and The preparation method and application can effectively improve the catalyst activation efficiency of persulfate, and can realize the complete removal of organic pollutants.

In order to achieve the above object, the present invention adopts the following technical solutions:

The present invention provides a method for preparing a bimetallic biochar catalyst, which is characterized by comprising the following steps:

(1) fully mixing the biomass powder and the aqueous solution of iron salt, then heating and evaporating to dryness to obtain a solid mixture; the above-mentioned solid mixture is calcined under an inert atmosphere to obtain an nZVI-BC catalyst;

(2) preparing a mixed aqueous solution of molybdate and sulfur-containing reducing agent, adding the nZVI-BC catalyst to the above mixed aqueous solution to obtain a precursor solution;

(3) subjecting the above precursor solution to a hydrothermal reaction under certain conditions, and separating, washing and drying the product after the reaction to obtain an nZVI/MoS ₂ -BC catalyst.

The above-mentioned method for preparing nZVI-BC catalyst belongs to a one-step pyrolysis method. The one-step pyrolysis method is to complete the preparation of biochar and the reduction of zero-valent iron in one step. Biochar (BC) is generated by lower pyrolysis, and at the same time, the iron salt is reduced to zero valent iron by the obtained biochar, that is, the biochar-loaded nano-zero valent iron is prepared.

The one-step pyrolysis method for the preparation of nZVI-BC catalysts is simpler and requires no additional reducing agent. During the calcination process, the defect structure of the biochar is increased, and the increased specific surface area is more conducive to the growth of MoS ₂ on the surface of the nZVI-BC catalyst during the hydrothermal process in step (3).

Preferably, the biomass powder in step (1) is obtained by crushing the biomass and then drying it through a 100-mesh sieve; further preferably, the biomass is plant straw, and the drying temperature is 80- 110℃, the time is 6-24h.

Preferably, the iron salt described in step (1) is any one of ferric nitrate, ferric sulfate, and ferric chloride.

Preferably, the mass ratio of the iron salt to the biomass powder in step (1) is 1:(1.7-3.4).

Preferably, the substance concentration of the iron salt in the aqueous solution of the iron salt in the step (1) is 0.05-0.1 mol/L.

Preferably, the heating temperature in step (1) is 75-95° C., and the time is 6-12 h.

Preferably, the inert atmosphere in step (1) is nitrogen, argon or helium.

Preferably, the calcination method in step (1) is to increase the temperature from room temperature to 700-900°C at a heating rate of 5-10°C/min, and the calcination time is 1-2h.

Preferably, in the step (2), the molybdate is selected from any one of (NH ₄ ) ₆ Mo ₇ O ₂₄ , K ₆ Mo ₇ O ₂₄ and Na ₆ Mo ₇ O ₂₄ .

Preferably, the sulfur-containing reducing agent in the step (2) is at least one of thiourea, cysteine, and thioacetamide.

Preferably, the mass ratio of the molybdate, the sulfur-containing reducing agent and the nZVI-BC is (1-2):(3-6):1.

Preferably, in the step (2), the substance concentration of molybdate is 0.01-0.1 mol/L, and the substance concentration of thiourea is 0.5-5 mol/L.

Preferably, the temperature of the hydrothermal reaction in the step (3) is 160-220° C., and the time is 6-12 h.

Preferably, in the step (3), the separation method is to aggregate the product by an external magnetic field; the washing method is to wash with ethanol and ultrapure water three times respectively; and the drying method is vacuum drying.

The invention also provides the bimetallic biochar catalyst nZVI/MoS ₂ -BC prepared by the above method, which is characterized in that MoS ₂ completely covers the surface of the BC, and the nZVI/MoS ₂ -BC catalyst has 378.8 and 406.6 cm ^-1 The peak of MoS ₂ , the D band and the G band of the carbon material disappear completely; preferably, the specific surface area of the nZVI/MoS ₂ -BC catalyst is 25-30 m ² /g, and the average pore size is 3.5-4 nm; The mass ratio of nano-zero valent iron, MoS ₂ and biochar was (0.5～1.5):(3.0～4.0):(4.5～6.5).

Preferably, the catalyst surface contains metal active sites Fe(0), Fe(II), Mo(IV) and Mo(V).

The bimetallic biochar catalyst has recyclability and regeneration.

The present invention also provides the application of the above-mentioned bimetallic biochar catalyst, which is characterized in that it is used for purifying organic waste water.

In the present invention, organic wastewater refers to wastewater containing refractory organic pollutants, including dye wastewater, pharmaceutical wastewater, pesticide wastewater, and the like.

The present invention also provides a method for purifying organic waste water, which is characterized by comprising the following steps: adding nZVI/MoS ₂ -BC catalyst and persulfate to the organic waste water respectively, or adding nZVI/MoS ₂ -BC catalyst and persulfuric acid to the organic waste water. After the salt is mixed, it is added to the organic waste water at the same time, and the reaction is stirred at a temperature of 15-35° C. After the reaction for 10-60 min, the nZVI/MoS ₂ -BC catalyst is filtered to obtain purified water.

Preferably, when the content of refractory organic pollutants in the organic wastewater is 1-20 mg/L, the dosage of nZVI/MoS ₂ -BC catalyst is 0.05-0.5 g/L, and the dosage of persulfate is 0-20 mg/L. 1mM.

Further preferably, when the content of rhodamine B in the organic wastewater is 10 mg/L, the amount of the nZVI/MoS ₂ -BC catalyst is ≥0.10 g/L. At this time, the removal rate of Rhodamine B by nZVI/MoS ₂ -BC catalyst can reach 100%.

Preferably, the pH of the organic wastewater is less than or equal to 11. Further preferably, the pH of the organic wastewater is 3-9.

Preferably, the organic wastewater contains chloride ions with a concentration of 0-20 mM. Chloride ions can promote the oxidation process of Rhodamine B.

The present invention also provides a composition comprising the above-mentioned bimetallic biochar catalyst, characterized in that it comprises an nZVI/MoS ₂ -BC catalyst and a persulfate, and the mass ratio of the nZVI/MoS ₂ -BC catalyst to the persulfate is 1: (0.7-4).

The present invention also provides a method for using the above composition, which is characterized by comprising the following steps: adding the nZVI/MoS ₂ -BC catalyst and persulfate in the composition to the organic waste water in a certain order, or combining the The material is directly added to the organic waste water, and the reaction is stirred at a temperature of 15-35 °C.

Preferably, the order of adding the nZVI/MoS ₂ -BC catalyst and the persulfate is as follows: first, the nZVI/MoS ₂ -BC catalyst is dispersed in the organic wastewater, and then the persulfate is added.

Preferably, the mass-volume ratio of the composition to the organic wastewater is (0.2-0.5): 1 g/L.

One or more technical solutions provided by the present invention have at least the following technical effects:

(1) The present invention uses biomass powder as precursor, prepares nZVI-BC by calcination method, and then synthesizes nZVI/MoS _2- BC catalyst, the nZVI/MoS ₂ -BC catalyst can activate PMS to generate various reactive oxygen species (SO ₄ ^·- , ·OH, ¹ O ₂ , O ₂ ^·- ) to oxidize pollutants in wastewater;

(2) The surface of the biochar in the bimetallic biochar catalyst of the present invention is loaded with nano zero-valent iron and MoS ₂ nanosheets. When applied to the PMS advanced oxidation technology, the Mo(IV) in the catalyst can generate The Fe(III) of the catalyst is reduced to Fe(II), which has an activating effect on persulfate, so that the activation efficiency of the catalyst on persulfate is improved, and the efficient degradation of organic pollutants in organic wastewater by persulfate is achieved;

(3) The surface of the bimetallic biochar catalyst of the present invention has a large number of metal active sites Fe(0), Fe(II), Mo(IV), Mo(V), and can improve the specific surface area and intermediary properties of the biochar material. the number of pores, so the adsorption and catalytic performance are improved;

(4) the bimetallic biochar catalyst of the present invention has better removal ability to pollutants in organic wastewater with different pH ranges;

(5) The bimetallic biochar catalyst of the present invention has an excellent removal effect on Rhodamine B, the highest removal rate reaches 100%, and the catalyst has good circulation and regeneration performance; 8.4% improvement after four times.

(6) The preparation method of the catalyst of the present invention is simple, easy to operate, and low in cost, and can be suitable for industrial mass production.

Description of drawings

Fig. 1 is the difference among comparative example 1 (labeled as (a)), comparative example 2 (labeled as (b)), comparative example 3 (labeled as (c)), and embodiment 1 (labeled as (d)) of the present invention Scanning Electron Microscopy (SEM) of the catalyst.

Fig. 2 is the X-ray diffraction pattern of different catalysts in Example 1 of the present invention and Comparative Examples 1-3.

3 is the Raman spectrum of different catalysts in Example 1 of the present invention and Comparative Examples 1-3.

4 is the BET specific surface test of different biochar catalysts in Example 1 and Comparative Examples 1-3 of the present invention.

Fig. 5 is a pore size distribution diagram of different biochar catalysts in Example 1 and Comparative Examples 1-3 of the present invention.

6 is a high-resolution transmission electron microscope (HRTEM) image of the nZVI/MoS ₂ -BC catalyst in Example 1 of the present invention.

Figure 7 shows the oxidation of water by PMS activated by catalysts (nZVI/MoS ₂ -BC, BC, nZVI-BC, MoS ₂ -BC, blank, nZVI-BC+MoS ₂ -BC) in Example 1 of the present invention and Comparative Examples 1 to 5 Rendering of Rhodamine B.

FIG. 8 is a diagram showing the effect of activating PMS to oxidize Rhodamine B in water by nZVI/MoS ₂ -BC catalyst in Examples 1 to 4 and Comparative Example 4 of the present invention.

9 is a graph showing the effect of the nZVI/MoS ₂ -BC catalyst in Example 1, Examples 5-7, and Comparative Example 6 of the present invention activating PMS to oxidize Rhodamine B in water under different PMS dosages.

FIG. 10 is a graph showing the effect of activating PMS to oxidize Rhodamine B in water by nZVI/MoS ₂ -BC catalysts in Examples 8 to 12 of the present invention at different pH.

FIG. 11 is a diagram showing the effect of activating PMS to oxidize Rhodamine B in water by nZVI/MoS ₂ -BC catalyst in Example 1 and Examples 13-16 of the present invention under different chloride ion concentrations.

Figure 12 is a diagram showing the effect of activating PMS to oxidize Rhodamine B in water after the nZVI/MoS ₂ -BC catalyst in Example 17 of the present invention has undergone four cycles and regeneration treatments.

Detailed ways

In the following, a bimetallic biochar catalyst and its preparation method and application will be further described by way of specific embodiments in conjunction with the accompanying drawings. The raw materials and reagents used in the present invention can be obtained commercially.

In the present invention, rhodamine B dye wastewater is selected as a typical refractory organic waste water for simulation experiments in the following examples. Rhodamine B is not a limitation on refractory organics, as long as the pollutants within the scope of refractory organics are all within the scope of the present invention. within the scope of protection.

The PMS used in the present invention is potassium hydrogen persulfate composite salt, and the potassium hydrogen persulfate composite salt component includes 2KHSO ₅ ·KHSO ₄ ·K ₂ SO ₄ , 42%-46% KHSO ₅ and 54%-58% (KHSO ₄ +K ₂ SO ₄ ). The average molar mass of potassium hydrogen persulfate complex salt is 614.76g/mol.

Example 1

A preparation method and application of an nZVI/MoS ₂ -BC catalyst, comprising the following steps:

(1) Select a certain amount of plant straw, wash and air dry; use a crusher to crush the straw into granules, pass the crushed straw through a 100-mesh sieve, collect the sieved straw and dry it in an oven at 105°C for 6 Hour;

Add Fe(NO ₃ ) ₃ ·9H ₂ O to 100 mL of ultrapure water to obtain a 0.06 mol/L ferric nitrate solution, and ultrasonicate for 10 min to make it into a uniform ferric nitrate solution;

Add 5.0 g of straw powder to the above-mentioned ferric nitrate solution, stir magnetically for 1 h to make it fully mixed;

The above mixture was placed in a magnetic stirring water bath, heated and evaporated at 90°C for 6 hours to dryness; the dried biomass was crushed;

(2) Put the crushed biomass into a quartz boat, place it in a tube furnace, heat up to 800°C at a rate of 5°C/min, and perform calcination at 800°C for 2 hours in a nitrogen atmosphere to obtain an nZVI-BC catalyst;

(3) Dissolve (NH ₄ ) ₆ Mo ₇ O ₂₄ and thiourea in 160 mL of ultrapure water, and sonicate for 30 min to obtain a uniform mixed solution. The concentration of (NH ₄ ) ₆ Mo ₇ O ₂₄ in the mixed solution is 10 mmol/ L, the concentration of thiourea is 0.5mol/L; 1.0g nZVI-BC is added to the above mixed solution, and magnetically stirred for 1h to fully mix to obtain the precursor solution;

(4) Transfer the precursor solution to a stainless steel reaction kettle containing a polytetrafluoroethylene liner (200 mL), and perform a hydrothermal reaction in an oven at a temperature of 200° C. and a time of 10 h. After the reaction, the magnetic materials were separated and aggregated by an external magnetic field, washed alternately with ethanol and ultrapure water for three times, and vacuum-dried to obtain the nZVI/MoS ₂ -BC catalyst.

The mass ratio of nano-zero valent iron, MoS ₂ and biochar in the nZVI/MoS ₂ -BC catalyst obtained in this example is 1:4:5.

The above catalyst is used to activate the rhodamine B in the oxidative dye wastewater with potassium hydrogen persulfate composite salt, and the dye wastewater is a rhodamine B solution prepared by using ultrapure water, the pH is 6, and does not contain chloride ions. Removing rhodamine B by using the above catalyst includes the following steps: adding nZVI/MoS ₂ -BC catalyst to rhodamine B dye wastewater, dispersing the agglomerated particles in water at 25° C. by ultrasonic for 5 min, and then adding potassium hydrogen peroxymonosulfate composite salt, The reaction system was mechanically stirred for 60min advanced oxidation reaction. During the advanced oxidation reaction, 5 mL samples were taken at regular intervals (reaction time 0, 10, 20, 30, 40, 50, 60 min), and filtered with a 0.45 μm nylon membrane, and the clear liquid obtained by the filtration was taken. The absorbance was measured at a wavelength of 554 nm by an ultraviolet-visible spectrophotometer to determine the advanced oxidation removal rate of rhodamine B, thereby obtaining the catalytic effect of the system on rhodamine B. Wherein, the initial concentration of rhodamine B is 10 mg/L; the dosage of catalyst is 0.10 g/L; the dosage of potassium hydrogen persulfate complex salt is 0.325 mM; and the volume of waste water is 100 mL.

Comparative Example 1

A BC catalyst, the preparation steps of which are as follows: a certain amount of plant straw is selected, washed and air-dried; the straw is crushed into granules by a crusher, the crushed straw is passed through a 100-mesh sieve, and the sieved straw is collected and dried in an oven ; Put the dried straw into a quartz boat, place it in a tube furnace, and calcine it in a nitrogen atmosphere at a temperature of 800 °C, a time of 2 h, and a heating rate of 5 °C/min to obtain a BC catalyst.

Use the above-mentioned BC catalyst to activate the potassium hydrogen persulfate composite salt, and oxidize the rhodamine B in the dye wastewater, except that the nZVI/MoS ₂ -BC catalyst is replaced by a BC catalyst, other operation steps are the same as those in Example 1.

Comparative Example 2

An nZVI-BC catalyst, the preparation steps of which are the same as those of step (1) and step (2) in Example 1.

Use the above-mentioned nZVI-BC catalyst to activate the potassium hydrogen persulfate composite salt, and oxidize the rhodamine B in the dye wastewater, except that the nZVI/MoS ₂ -BC catalyst is replaced by the nZVI-BC catalyst, other operation steps are the same as the embodiment 1.

Comparative Example 3

A MoS ₂ -BC catalyst, the preparation steps of which are as follows:

(1) Select a certain amount of plant straw to wash and air dry; use a crusher to crush the straw into granules, pass the crushed straw through a 100-mesh sieve, collect the sieved straw and dry it in an oven at 105°C 6h; put the dried biomass powder into a quartz boat, place it in a tube furnace, calcine in a nitrogen atmosphere, increase the temperature from room temperature to 800°C at a rate of 5°C/min, and keep it for 2h to obtain a BC catalyst ;

(2) Dissolve (NH ₄ ) ₆ Mo ₇ O ₂₄ and thiourea in 160 mL of ultrapure water, and ultrasonicate for 30 min to obtain a uniform mixed solution. The concentration of (NH ₄ ) ₆ Mo ₇ O ₂₄ in the mixed solution is 10 mmol/ L, the concentration of thiourea is 0.5mol/L; 1.0g BC is added to the above mixed solution, and magnetically stirred for 1h to make it fully mixed to obtain the precursor solution;

(3) The precursor solution was transferred to a stainless steel reaction kettle containing a polytetrafluoroethylene lining (200 mL), and the hydrothermal reaction was carried out in an oven at a temperature of 200° C. and a time of 10 h. After the reaction, the product was centrifuged at 8000 r/min for 5 min, washed alternately with ethanol and ultrapure water for three times, and vacuum dried to obtain a MoS ₂ -BC catalyst.

The above-mentioned MoS ₂ -BC catalyst was used to activate PMS and oxidize rhodamine B in the dye wastewater, except that the nZVI/MoS ₂ -BC catalyst was replaced by a MoS ₂ -BC catalyst, other operation steps were the same as those in Example 1.

Comparative Example 4

Blank control: do not add any catalyst to the dye wastewater, directly use potassium hydrogen persulfate composite salt to oxidize rhodamine B in the dye wastewater, except that no catalyst is used, other operation steps are the same as those in Example 1.

Comparative Example 5

After mixing the nZVI-BC catalyst and the MoS ₂ -BC catalyst, the potassium hydrogen persulfate composite salt was activated to oxidize rhodamine B in the dye wastewater, and the dosage ratio of nZVI, BC, and MoS ₂ in the mixed catalyst of this comparative example , which is consistent with the dosage ratio of each component of the nZVI/MoS ₂ -BC catalyst in Example 1.

The morphologies of the catalysts in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were respectively observed with a scanning electron microscope, and the results are shown in Figure 1 .

X-ray diffraction analysis was carried out on the four catalysts of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3. The results are shown in Figure 2. From Figure 2, it can be concluded that the nZVI/MoS ₂ -BC catalyst has MoS2 nanosheets The (002), (100), (110) crystal planes and the (110) crystal plane of the nano-zero-valent iron fully demonstrate that MoS2 nanosheets and nano-zero-valent iron were successfully loaded onto the surface of biochar.

Raman spectroscopy was performed on the four catalysts of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The results are shown in Figure 3. The nZVI/MoS ₂ -BC catalyst has MoS ₂ at 378.8 and 406.6 cm ^-1 . Peak, the D and G bands of the carbon material disappear completely, indicating that _MoS2 completely covers the BC surface, which is consistent with the conclusion of the SEM observation.

The specific surface areas of the four catalysts of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were tested, and the results were shown in Figure 4. The pore size distributions of the above four catalysts were tested, and the results were shown in Figure 5. It can be seen from Figure 4 and Figure 5 that the ZVI/MoS ₂ -BC catalyst has higher specific surface area and larger pore capacity than BC, MoS ₂ -BC.

The catalyst of Example 1 was analyzed by transmission electron microscopy, as shown in Figure 6. In Figures (a) and (b), the lattice fringes with a spacing of 0.63 nm correspond to the (002) crystal plane of MoS ₂ nanosheets, and 10 The layer lattice fringes of 2.7 nm and 2.5 nm correspond to the (100) and (102) crystal planes of MoS ₂ nanosheets, respectively; in Figure (b), the interlayer spacing of 3.4 nm is the graphitic carbon part of the biochar. The black dots in (c) and (d) are the nano-zero valent iron particles dispersed on the biochar and molybdenum disulfide nanosheets.

Example 1. The removal effect of Rhodamine B in Comparative Examples 1-4 is shown in Figure 7: the nZVI/MoS ₂ -BC catalyst has the best removal effect, completely removing Rhodamine B in water within 60 min, and the removal rate is 100%. The removal rates of Rhodamine B in five groups of systems, nZVI-BC, MoS ₂ -BC, BC, blank (only potassium peroxymonosulfate complex salt was added), and nZVI-BC/MoS ₂ -BC were 64.1%, 41.6% and 30.8%, respectively. , 14.6%, 88.9%. This shows that the nano-zero-valent iron and molybdenum disulfide bimetallic supported biochar has the best catalytic performance.

Example 2

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the amount of the nZVI/MoS ₂ -BC catalyst is 0.05g/L.

Example 3

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the amount of the nZVI/MoS ₂ -BC catalyst is 0.20 g/L.

Example 4

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the amount of the nZVI/MoS ₂ -BC catalyst is 0.30 g/L.

The removal effects of Rhodamine B in Examples 1-4 and Comparative Example 4 are compared, and the results are shown in Figure 8. As the dosage of catalyst increases, the catalytic effect is better. When the dosage of catalyst is 0.30g/L, Rhodamine B can be completely removed within 10min. Although increasing the amount of catalyst can shorten the catalytic oxidation reaction time, considering the production cost of the catalyst, when the initial concentration of rhodamine B in the organic wastewater is 10 mg/L, the optimal amount of the catalyst is 0.10 g/L.

Example 5

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the amount of the potassium hydrogen peroxymonosulfate composite salt is 0.163 mM.

Example 6

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the amount of the potassium hydrogen peroxymonosulfate composite salt is 0.488 mM.

Example 7

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the amount of the potassium hydrogen peroxymonosulfate composite salt is 0.651 mM.

Comparative Example 6

The application of a kind of nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the consumption of the potassium hydrogen peroxymonosulfate composite salt is 0.

The rhodamine B removal effects of Example 1, Example 5-7, and Comparative Example 6 were compared, and the results were shown in Figure 9. When the potassium hydrogen peroxymonosulfate complex salt was not added, that is, when the dosage was 0 mM, it represented The adsorption and removal rate of rhodamine B by nZVI/MoS ₂ -BC at 60 min can reach 41.7%. This is consistent with the results of BET characterization of the bimetal-modified biochar with increased specific surface area and pore capacity. Organics adsorbed on the catalyst surface are more easily attacked by reactive free radicals. When the dosage of potassium peroxymonosulfate complex salt increased from 0.163mM to 0.325mM, the degradation rate of 0.163mM before 40min was significantly higher than that of 0.325mM. The reason may be that more potassium peroxymonosulfate complex salt molecules were activated to produce too much The active free radicals will contact with each other to cause free radical quenching, which further slows down the degradation of Rhodamine B. After 40min, the removal rate of rhodamine B in the system with the dosage of 0.325mM gradually became higher, and after 60min, the removal rate of 0.325mM rhodamine B was completely removed, while the removal rate of 0.163mM was 98.4%, indicating that in the 0.163mM reaction system The amount of potassium hydrogen peroxymonosulfate complex salt was almost consumed, and Rhodamine B could not be completely removed. From 0.325 mM to 0.651 mM, the time required for complete removal of Rhodamine B was shortened to within 40 min with the gradual increase in the amount of potassium hydrogen peroxymonosulfate complex salt. However, from the point of view of kinetic constant k, 0.651mM (0.1346min ^-1 ) compared with 0.488mM (k=0.1525min ^-1 ), the reaction rate slows down when the dosage increases, which further indicates that too much peroxymonosulfuric acid The dosage of hydrogen-potassium complex salt will cause the "internal friction" of the generated active free radicals, resulting in that the effective utilization of active free radicals cannot be maximized.

Example 8

The application of an nZVI/MoS ₂ -BC catalyst is different from Example 1 in that the pH of the Rhodamine B wastewater is adjusted by dropwise addition of 0.1MH ₂ SO ₄ or 0.1M NaOH, and the pH is 3.

Example 9

An application of nZVI/MoS ₂ -BC catalyst, the difference from Example 8 is that the pH is 5.

Example 10

An application of nZVI/MoS ₂ -BC catalyst, the difference from Example 8 is that the pH is 7.

Example 11

An application of nZVI/MoS ₂ -BC catalyst, the difference from Example 8 is that the pH is 9.

Example 12

An application of nZVI/MoS ₂ -BC catalyst, the difference from Example 8 is that the pH is 11.

The removal effects of Rhodamine B in Examples 8-12 were compared. The results are shown in Figure 10. When the pH was 3, the catalytic performance of nZVI/MoS ₂ -BC catalyst was the best, and the removal rate of Rhodamine B within 40min was 100%. . With the gradual increase of pH, the catalytic performance gradually decreased. When pH=11, the removal rate was 66.6%. It shows that the nZVI/MoS ₂ -BC catalyst is more favorable for activating potassium hydrogen persulfate complex salt to generate active radicals under acidic conditions. Although the catalytic reaction rate decreased under alkaline conditions, the removal rate of the pH=11 alkaline environment was still higher than that of the reaction system (14.6%) with only potassium hydrogen peroxymonosulfate complex salt added, which further indicated that nZVI/MoS ₂ -BC Catalytic oxidation reactions combined with potassium peroxymonosulfate complex salts accommodate a wider pH range.

Example 13

The application of an nZVI/MoS ₂ -BC catalyst differs from Example 1 in that by adding NaCl, the chloride ion concentration in Rhodamine B wastewater is 1 mM.

Example 14

The application of an nZVI/MoS ₂ -BC catalyst differs from Example 1 in that by adding NaCl, the chloride ion concentration in Rhodamine B wastewater is 5 mM.

Example 15

The application of an nZVI/MoS ₂ -BC catalyst differs from Example 1 in that by adding NaCl, the chloride ion concentration in Rhodamine B wastewater is 10 mM.

Example 16

The application of an nZVI/MoS ₂ -BC catalyst differs from Example 1 in that by adding NaCl, the chloride ion concentration in Rhodamine B wastewater is 20 mM.

The removal effects of Rhodamine B in Example 1 and Examples 13-16 were compared. The results are shown in Figure 11. As the chloride ion concentration increases, the better the degradation effect of Rhodamine B The oxidation process of B has a promoting effect. When the dosage of catalyst was 20mM, Rhodamine B could be completely removed within 20min. It shows that increasing the chloride ion concentration can shorten the time of catalytic oxidation reaction. The invention provides a new technical support for the degradation of organic matter containing high chloride salt wastewater in industrial production, and has high degradation efficiency, short time consumption, and good commercial application prospect.

Example 17

An application of an nZVI/MoS ₂ -BC catalyst, the nZVI/MoS ₂ -BC catalyst activates potassium hydrogen persulfate composite salt after multiple cycles and regeneration treatments, and then oxidizes Rhodamine B in water, the specific steps The steps are: adding nZVI/MoS ₂ -BC to Rhodamine B dye wastewater, ultrasonicating for 5 min to disperse the agglomerated particles in water, then adding potassium hydrogen persulfate complex salt, mechanically stirring the reaction system, and performing advanced oxidation reaction for 60 min. During the advanced oxidation reaction, 5 mL samples were taken at regular intervals (reaction time 0, 10, 20, 30, 40, 50, 60 min), and filtered with a 0.45 μm nylon membrane, and the clear liquid obtained by the filtration was taken. The absorbance was measured at a wavelength of 554 nm by UV-visible spectrophotometer to determine the advanced oxidation removal rate of rhodamine B, thereby obtaining the catalytic effect of nZVI/MoS ₂ -BC on rhodamine B. The catalyst in the water was collected by an external magnetic field, put into an oven at 60°C for drying, and after drying, the above-mentioned advanced oxidation experimental steps were repeated for 5 times. After the fourth time, the recovered catalyst was calcined and regenerated at 300°C, and the fifth cycle experiment was carried out. The above experimental results are shown in Figure 12. Among them, rhodamine B, 10 mg/L; catalyst, 0.10 g/L; potassium hydrogen persulfate complex salt, 0.325 mM; waste water volume, 100 mL.

As shown in Fig. 12, after 4 cycles of nZVI/MoS ₂ -BC catalyst, the removal rate of Rhodamine B decreased from 100% to 49.4%, which was due to the decrease of the catalytic performance due to the reduction of active sites, and the degradation of the adsorption part on the surface of the catalyst. The relationship between the intermediate product and Rhodamine B in water will also cause the reduction of catalytic performance. After the catalyst regenerated at 300℃, the removal rate of Rhodamine B was improved in the fifth cycle experiment, which indicated that the nZVI/MoS ₂ -BC catalyst could recover some of the catalytic active sites after high temperature calcination, so the catalyst had regeneration performance.

Claims (10)

1. a preparation method of bimetallic biochar catalyst, is characterized in that, comprises the following steps: (1) fully mixing the biomass powder and the aqueous solution of iron salt, then heating and evaporating to dryness to obtain a solid mixture; the above-mentioned solid mixture is calcined under an inert atmosphere to obtain an nZVI-BC catalyst; (2) preparing a mixed aqueous solution of molybdate and sulfur-containing reducing agent, adding the nZVI-BC catalyst to the above mixed aqueous solution to obtain a precursor solution; (3) subjecting the above precursor solution to a hydrothermal reaction under certain conditions, and separating, washing and drying the product after the reaction to obtain an nZVI/MoS ₂ -BC catalyst. 2. preparation method according to claim 1, is characterized in that, in described step (1), the mass ratio of iron salt and biomass powder is 1:(1.7-3.4); Preferably, in the step (1), the biomass powder is obtained by crushing the biomass and then drying it through a 100-mesh sieve; further preferably, the biomass is plant straw, and the drying temperature is 80- 110℃, the time is 6-24h; Preferably, in the step (1), the iron salt is any one of ferric nitrate, ferric sulfate, and ferric chloride; Preferably, the heating temperature in the step (1) is 75-95°C, the time is 6-12h, and the calcination method is to raise the temperature from room temperature to 700-900°C at a heating rate of 5-10°C/min , the calcination time is 1-2h. 3. preparation method according to claim 1, is characterized in that, in described step (2), molybdate is selected from (NH ₄ ) ₆ Mo ₇ O ₂₄ , K ₆ Mo ₇ O ₂₄ , Na ₆ Mo ₇ O any of ₂₄ ; Preferably, in the step (2), the sulfur-containing reducing agent is at least one of thiourea, cysteine, and thioacetamide; Preferably, in the step (2), the mass ratio of molybdate, sulfur-containing reducing agent and nZVI-BC catalyst is (1-2):(3-6):1; Preferably, in the step (2), the substance concentration of molybdate is 0.01-0.1 mol/L, and the substance concentration of thiourea is 0.5-5 mol/L. 4. The preparation method according to claim 1, wherein the temperature of the hydrothermal reaction in the step (3) is 160-220°C, and the time is 6-12h; preferably, in the step (3) The separation method is to aggregate the product by an external magnetic field, the washing method is to alternately wash three times with ethanol and ultrapure water respectively, and the drying method is vacuum drying. 5. The bimetallic biochar catalyst prepared by the method according to any one of claims 1-4, wherein MoS ₂ completely covers the surface of BC, and the nZVI/MoS ₂ -BC catalyst is at 378.8 and 406.6 cm ^-1 There is a peak of MoS ₂ , and the D and G bands of the carbon material disappear completely; preferably, the specific surface area of the catalyst is 25-30 m ² /g, and the average pore size is 3.5-4 nm; The mass ratio of valent iron, MoS ₂ and biochar is (0.5～1.5):(3.0～4.0):(4.5～6.5); preferably, the catalyst surface contains metal active sites Fe(0), Fe(II) ), Mo(IV), Mo(V). 6. The application of the catalyst according to claim 5, characterized in that, it is used for purifying organic waste water. 7. a method for purifying organic waste water, is characterized in that, comprises the following steps: nZVI/MoS ₂ -BC catalyst and persulfate are respectively added in organic waste water, or nZVI/MoS ₂ -BC catalyst and persulfate are coordinated Then, it is added into the organic waste water at the same time, and the reaction is stirred at a temperature of 15-35° C. After the reaction for 10-60 min, the nZVI/MoS ₂ -BC catalyst is filtered to obtain purified water. 8. The method according to claim 7, wherein the organic waste water contains refractory organic pollutants, and when the content of the refractory organic pollutants is 1-20 mg/L, nZVI/MoS ₂ -BC The dosage of catalyst is 0.05-0.5g/L, and the dosage of persulfate is 0-1mM; preferably, the pH of the organic wastewater is ≤11, more preferably 3-9; The waste water contains chloride ions; further preferably, the concentration of the chloride ions is 0-20 mM. 9. The composition comprising the catalyst of claim 5, wherein the composition comprises an nZVI/MoS ₂ -BC catalyst and a persulfate, and the mass ratio of the nZVI/MoS ₂ -BC catalyst and the persulfate is is 1: (0.7-4). 10. The method for use of the composition according to claim 9, characterized in that it comprises the steps of: adding the nZVI/MoS ₂ -BC catalyst and persulfate in the composition to the organic waste water in a certain order, or The composition is directly added to the organic waste water, and the reaction is stirred at a temperature of 15-35°C; Preferably, the mass volume ratio of the composition to the organic wastewater is (0.2-0.5): 1 g/L; Preferably, the order of adding the nZVI/MoS ₂ -BC catalyst and the persulfate is as follows: first, the nZVI/MoS ₂ -BC catalyst is dispersed in the organic wastewater, and then the persulfate is added.

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