Method for Degrading Acid Orange 7 by Using a Magnetic Biochar-Supported Catalyst for Papermaking Sludge

Abstract

The invention discloses a method for degrading acid orange 7 by using a magnetic biochar-supported catalyst of papermaking sludge, which includes: adding the magnetic biochar-supported catalyst of papermaking sludge into acid orange 7 sewage, adding persulfate to initiate the reaction after adsorption equilibrium, and recovering the magnetic biochar-supported catalyst of papermaking sludge by using a magnet after the reaction ends; the preparation method of the magnetic biochar-supported catalyst of papermaking sludge includes: directly adding the powder obtained by drying papermaking sludge into a Co(NO3)2 solution, continuously stirring and mixing for 1 to 25 hours, separating the solid and liquid, taking the solid for drying and pyrolyzing in an argon atmosphere, then washing and drying again to obtain the magnetic biochar-supported catalyst of papermaking sludge; the magnetic biochar-supported catalyst of papermaking sludge has the following phases: Fe2O3, Co3O4, CaCO3 and Fe3O4.

Description

Technical Field

[0001] The present invention relates to the technical field of resource treatment of papermaking sludge, and particularly relates to a method for degrading Acid Orange 7 (AO7) by using a magnetic biochar-supported catalyst for papermaking sludge. Background Art

[0002] Azo dyes are the most widely used synthetic dyes in the dyeing process. Approximately 10%-15% of azo dyes are discharged into the water environment without treatment during the production process, destroying the ecological balance and affecting human health. Therefore, azo dye-containing wastewater must be effectively treated before discharge. Among various water treatment technologies, the sulfate radical-based advanced oxidation process (SRAOPs) is an ideal process for treating refractory dye wastewater. Its principle is mainly to generate strongly oxidizing reactive oxygen species (ROSs), such as sulfate radicals (SO 4 · - ), hydroxyl radicals (HO·), singlet oxygen ( 1 O 2 ), etc., to rapidly oxidize and decompose organic pollutants to achieve the purpose of water purification. Currently, one of the research difficulties of this technology is to develop heterogeneous catalytic materials with low cost, high activity, and easy recovery.

[0003] On the other hand, with the rapid development of the papermaking industry, a large amount of papermaking sludge is discharged during production. According to statistics, about 6.5 m 3 of papermaking sludge will be generated for every 1 ton of finished paper produced. Papermaking sludge has a complex composition (the main components are cellulose, lignin, ferrous sulfate, etc.), and it is difficult to be resourcefully utilized. Currently, it is mainly disposed of by landfill, composting, and ocean dumping. The disposal cost is high, and it will cause environmental pollution and resource waste to a certain extent. Therefore, how to effectively dispose of papermaking sludge has become a major problem restricting the sustainable development of the papermaking industry.

[0004] The patent specification with publication number CN115041166A discloses a heterogeneous persulfate catalyst, its preparation method and application, belonging to the technical field of harmless and resource treatment of papermaking sludge. The preparation method of the heterogeneous persulfate catalyst includes the following steps: (1) adding ferrous salt and persulfate to the sludge for sludge conditioning and then dehydrating to obtain dehydrated sludge; (2) pyrolyzing the dehydrated sludge to obtain a heterogeneous persulfate catalyst. This patented technology method uses papermaking sludge as the main raw material to prepare a heterogeneous persulfate catalyst, realizing the resource utilization of papermaking sludge solid waste.

[0005] The patent specification with publication number CN119034820A discloses a preparation method of a catalyst of iron and cobalt oxides supported on sludge-derived carbon and its application in electro-Fenton degradation of organic pollutants. The specific preparation process is as follows: First, the papermaking sludge is dried and then soaked in excessive hydrofluoric acid to remove impurities therein. Then, the residual hydrofluoric acid is removed by centrifugation and suction filtration. Subsequently, it is put back into the oven for drying and ground into powder. Then, it is added to the Co(NO 3 ) 2 ·6H 2 O solution and the Fe(NO 3 ) 3 ·9H 2 O solution for soaking. Then, it is stirred and mixed evenly in a magnetic stirrer and dried under vacuum. Finally, it is ground into powder and calcined in a tube furnace to obtain the product, the catalyst of iron and cobalt oxides supported on sludge-derived carbon. This catalyst of iron and cobalt oxides supported on sludge-derived carbon can efficiently generate H 2 O 2 and activate persulfate simultaneously, and thus can be used in the electro-Fenton reaction system for degrading organic pollutants. The catalyst prepared by this patented technology is a carbon-supported CoO nanoparticle and Fe 2 O 3 polyhedron structure. In addition, in the above patented technology, the dried papermaking sludge is first soaked and treated with hydrofluoric acid, which will dissolve the elements in the papermaking sludge that originally have the potential to be active ingredients. Summary of the Invention

[0006] The present invention provides a method for degrading Acid Orange 7 with a catalyst supported on magnetic biochar of papermaking sludge. Using papermaking sludge as a cheap raw material and taking advantage of its characteristics of being rich in iron and carbon elements, a new type of magnetic biochar SRAOPs catalytic material with high catalytic activity is developed and used to activate peroxymonosulfate (PMS) to degrade the typical azo dye Acid Orange 7.

[0007] The specific technical solution is as follows:

[0008] A method for degrading Acid Orange 7 with a catalyst supported on magnetic biochar of papermaking sludge, comprising: adding the catalyst supported on magnetic biochar of papermaking sludge to the Acid Orange 7 sewage, adding peroxymonosulfate to start the reaction after adsorption equilibrium, and recovering the catalyst supported on magnetic biochar of papermaking sludge by using a magnet after the reaction ends;

[0009] The preparation method of the catalyst supported on magnetic biochar of papermaking sludge includes: passing the papermaking sludge through a 100-300 mesh sieve and then drying it, directly adding the obtained dried powder to the Co(NO 3 ) 2 solution, continuously stirring and mixing for 1-25 hours, then separating the solid and liquid (such as by centrifugation, etc.), taking the solid for drying and pyrolyzing in an argon atmosphere, and then washing and drying again to obtain the catalyst supported on magnetic biochar of papermaking sludge;

[0010] The papermaking sludge magnetic biochar-supported catalyst has the following phases: Fe 2 O 3 , Co 3 O 4 , CaCO 3 and Fe 3 O 4 .

[0011] In the preparation method of the papermaking sludge magnetic biochar-supported catalyst of the present invention, unlike the operation of pickling papermaking sludge with hydrofluoric acid as described in the patent specification with publication number CN119034820A, the components such as calcium carbonate, ferrous sulfate, and ferric oxide in the original papermaking sludge are retained. On this basis, different from the impregnation method described in the patent specification with publication number CN119034820A, the preparation method of the papermaking sludge magnetic biochar-supported catalyst of the present invention is to directly add the powder obtained by drying the papermaking sludge into the Co(NO 3 ) 2 solution, soak for a period of time and then take out. This process relies on ion exchange and the adsorption of papermaking sludge to capture Co 2+ , load Co 2+ into the papermaking sludge, and then carry out pyrolysis in an argon atmosphere, wash away impurities and dry to obtain the papermaking sludge magnetic biochar-supported catalyst. Thus, in the finally obtained papermaking sludge magnetic biochar-supported catalyst, there are characteristics of coexistence of phases such as Fe 2 O 3 , Co 3 O 4 , CaCO 3 and Fe 3 O 4 , which is beneficial to the progress of SRAOPs. In short, the papermaking sludge magnetic biochar-supported catalyst of the present invention can efficiently activate peroxymonosulfate to generate singlet oxygen reactive oxygen species, and thus can efficiently degrade acid orange 7.

[0012] In some embodiments, in the method for degrading acid orange 7 using the papermaking sludge magnetic biochar-supported catalyst, the papermaking sludge needs to be dried after passing through a 100-300 mesh sieve, such as 200 mesh.

[0013] In some embodiments, in the method for degrading acid orange 7 using the papermaking sludge magnetic biochar-supported catalyst, the mass ratio of the added papermaking sludge magnetic biochar-supported catalyst to the mass of acid orange 7 in the acid orange 7 sewage can be 1-25:10.

[0014] In some embodiments, in the method for degrading Acid Orange 7 with the papermaking sludge magnetic biochar-supported catalyst, the content of Acid Orange 7 in the Acid Orange 7 wastewater can be 1 to 200 mg / L.

[0015] In some embodiments, in the method for degrading Acid Orange 7 with the papermaking sludge magnetic biochar-supported catalyst, the mass ratio of the added mass of persulfate to the added mass of the papermaking sludge magnetic biochar-supported catalyst can be 1 to 2:1, such as 1.5:1, etc.

[0016] In some embodiments, in the method for degrading Acid Orange 7 with the papermaking sludge magnetic biochar-supported catalyst, the reaction temperature can be 10 to 30 °C, such as 25 °C, etc.

[0017] In some embodiments, in the method for degrading Acid Orange 7 with the papermaking sludge magnetic biochar-supported catalyst, the pH of the reaction system can be 4 to 12, such as 4.24, 7.16, 10.19, 11.86, etc.

[0018] In some embodiments, in the method for degrading Acid Orange 7 with the papermaking sludge magnetic biochar-supported catalyst, stirring can be accompanied during the reaction. Further, the stirring speed can be 200 to 300 rpm, such as 250 rpm, etc.

[0019] In some preferred examples, in the method for preparing the papermaking sludge magnetic biochar-supported catalyst, the mass of the powder obtained by drying the papermaking sludge and the number of moles of Co(NO 3 ) 2 in the solution of Co(NO 3 ) 2 have a ratio of 1 g:10 to 20 mmol, such as 1 g:15 mmol, etc.

[0020] In some preferred examples, in the method for preparing the papermaking sludge magnetic biochar-supported catalyst, the concentration of Co(NO 3 ) 2 in the solution of Co(NO 3 ) 2 is 0.1 to 0.5 mol / L.

[0021] In some preferred examples, in the method for preparing the papermaking sludge magnetic biochar-supported catalyst, the pyrolysis temperature is 540 to 560 °C, such as 550 °C, etc., and the pyrolysis time is 2 to 3 h.

[0022] The magnetic biochar-supported catalyst of papermaking sludge in the present invention constructs a magnetic biochar + PMS system as a novel magnetic biochar material, promotes the generation of singlet reactive oxygen species in the magnetic biochar + PMS system, and can completely degrade Acid Orange 7. The pH application range of the magnetic biochar-supported catalyst + PMS system of papermaking sludge in the present invention is wide (applicable to pH = 4.2 - 11.9). When the catalyst dosage is 0.2 g / L and the PMS concentration is 0.3 g / L, the system can remove more than 97% of 100 mg / L AO7 within 60 min.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The present invention uses papermaking sludge as a carrier, and through the strategy of "treating waste with waste", provides a new idea for the development of wastewater / solid waste co-treatment technology.

[0025] 2. The present invention uses papermaking sludge as a raw material, which not only solves the problem of sludge disposal, but also has environmental friendliness. At the same time, the biochar itself is also easy to degrade and will not cause long-term negative impacts on the environment.

[0026] 3. The present invention prepares a magnetic biochar metal oxide catalyst by a thermal modification method, constructs a magnetic biochar + PMS system, promotes the generation of singlet reactive oxygen species in the magnetic biochar + PMS system, and explores the optimal performance of the magnetic biochar + PMS system for degrading Acid Orange 7, providing a new and effective way for the degradation of Acid Orange 7.

[0027] 4. The catalyst prepared in the present invention has phases such as Fe 2 O 3 , Co 3 O 4 , CaCO 3 , Fe 3 O 4 etc., and can be magnetically recovered. The catalyst has a rich mesoporous structure (average mesoporous pore diameter is 5 - 6 nm) and a large specific surface area (more than 43 m 2 / g), and has good catalytic activity and stability, which promotes the degradation of Acid Orange 7.

[0028] 5. The magnetic biochar metal oxide catalyst of papermaking sludge prepared in the present invention has higher cost-effectiveness. The preparation process of the magnetic biochar metal oxide catalyst of papermaking sludge is relatively simple, and it can be processed using existing pyrolysis equipment. Its raw materials are widely sourced and the price is relatively low. Therefore, the preparation and application of the sludge biochar catalyst not only helps to solve the problem of papermaking sludge disposal, but also can reduce the cost of pollution control. Description of the Drawings

[0029] Figure 1 Figure for comparing catalytic activities, where (a) is the figure for comparing the catalytic activities of dry papermaking sludge powder raw material, raw sludge biochar, and Co-containing biochar (i.e., Co / PSB catalyst), and (b) is the figure for comparing the catalytic activities of Co-containing biochar (i.e., Co / PSB catalyst), Cu-containing biochar (i.e., Cu / PSB catalyst), and Al-containing biochar (i.e., Al / PSB catalyst).

[0030] Figure 2 X-ray diffraction (XRD) patterns of dry papermaking sludge powder raw material, raw sludge biochar, Co-loaded papermaking sludge, Co / PSB catalyst, Cu / PSB catalyst, and Al / PSB catalyst.

[0031] Figure 3 High-resolution X-ray photoelectron spectroscopy (XPS) sub-spectrum figures of the catalyst, where (a) is the XPS sub-spectrum figure of Fe on the surface of Co / PSB catalyst before and after reaction, and (b) is the XPS sub-spectrum figure of Co on the surface of Co / PSB catalyst before and after reaction.

[0032] Figure 4 Hysteresis loop figures of raw sludge biochar and Co / PSB catalyst.

[0033] Figure 5 Figure of the effect of pH on the activation of PMS by Co / PSB catalyst for AO7 degradation.

[0034] Figure 6 Figure of the experimental results of coexisting ion interference for Co / PSB catalyst. Specific embodiments

[0035] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0036] Typical steps for the preparation of Co / PSB catalyst loaded with magnetic biochar from papermaking sludge are as follows: Pass the papermaking sludge through a 200-mesh sieve and dry it. Weigh 1 g of dry papermaking sludge powder and add it to 30 mL of 0.5 mol / L Co(NO 3 ) 2 solution. After impregnation for 1 h, stir magnetically for 24 h. After complete mixing, centrifuge the solid and dry it in an oven at 105°C to obtain Co-loaded papermaking sludge. Grind the Co-loaded papermaking sludge through a 50-mesh sieve, and then pyrolyze it in an argon atmosphere at 550°C for 2 h and cool it to room temperature. Wash the product with ultrapure water until the conductivity remains unchanged, and dry it in an oven at 60°C to constant weight. The obtained sample is Co / PSB.

[0037] For comparison, the preparation methods of the Al and Cu modified biochar catalysts Al / PSB and Cu / PSB are the same as above, except that the Co(NO 3 ) 2 solution is replaced with the Al(NO 3 ) 3 solution and the Cu(NO 3 ) 2 solution, respectively.

[0038] In addition, the present invention also uses dry papermaking sludge powder raw materials and raw sludge biochar as a comparison. The preparation process of the raw sludge biochar refers to the preparation scheme of the above-mentioned catalyst Co / PSB, except that the Co(NO 3 ) 2 solution is replaced with pure water, and the rest are the same.

[0039] The typical operation process of the degradation experiment is as follows: Add 20 mg of the catalyst or dry papermaking sludge powder or raw sludge biochar to 99 mL of 100 mg / L AO7 solution, ultrasonicate for 1 min, and let it stand for 30 min until adsorption equilibrium is reached. Then add 1 mL of 30 g / L PMS solution to initiate the reaction. The reaction process is carried out in a thermostatic shaker at a temperature of 25°C and a rotation speed of 250 r / min. After the reaction starts, take 1 mL of water sample at different time points, immediately quench the residual active substances with 0.5 mL of methanol, and then filter it through a 0.22 μm filter membrane and place it in a 2 mL chromatographic vial for testing. After the experiment, use a magnet to recover the magnetic catalyst in the reaction solution.

[0040] See Figure 1 in (a). Compared with the dry papermaking sludge powder raw material and the raw sludge biochar, the cobalt-containing biochar (Co / PSB) has a faster catalytic degradation rate of AO7; from the comparison results of the activities of the papermaking sludge biochars modified with different metals, that is Figure 1 in (b), it can be seen that the cobalt-containing biochar has a higher efficiency and more complete effect in activating PMS to degrade AO7, indicating that compared with Al and Cu, doping Co ions can make the papermaking sludge biochar have better PMS activation performance.

[0041] From the XRD results, that is Figure 2 , it can be seen that the dry papermaking sludge powder raw material shows diffraction peaks at 29.6°, 40.1°, 43.7°, 47.04°, and 50.73°, which belong to the typical calcite (CaCO 3 ) crystal structure, while the diffraction peaks at 35.6° and 23.8° are respectively attributed to Fe 2 O 3and ferrous sulfate containing crystal water. The above results indicate that the dried papermaking sludge powder raw material contains calcium carbonate and iron compounds in different forms. The diffraction peak positions of the raw sludge biochar are basically the same as those of the dried papermaking sludge powder raw material, and the signal intensities are all enhanced to varying degrees. For the papermaking sludge loaded with Co, the diffraction peak positions are basically the same as those of the dried papermaking sludge powder. The difference is that the signal intensities are all weakened to varying degrees, which may be caused by the surface loading of Co. For the final sample Co / PSB catalyst, obvious diffraction peaks of Co 3 O 4 appear at 45.1°, 59.4°, and 65.4°, indicating that the loaded Co salt is converted into Co 3 O 4 after pyrolysis; in addition, a diffraction peak of Fe 3 O 4 appears at 62.8°. The appearance of the Co 3 O 4 diffraction peak confirms the successful loading of the Co element, which can play an active role as an active site in the process of activating PMS. In addition, Fe 2 O 3 and Fe 3 O 4 can also participate in the catalytic reaction as active sites.

[0042] From Figure 3 (a), the characteristic peaks of four Fe elements, namely Fe 3+ 2p 1 / 2, Fe 2+ 2p 1 / 2, Fe 3+ 2p 3 / 2, and Fe 2+ 2p 3 / 2, can be observed. From Figure 3 (b), the characteristic peaks of four Co elements, namely Co 3+ 2p 1 / 2, Co 2+ 2p 1 / 2, Co 3+ 2p 3 / 2, and Co 2+ 2p 3 / 2, can be observed, indicating the existence of metallic iron and metallic cobalt in different valence states. By comparing the Fe 2p XPS spectra and Co 2p XPS spectra before and after the reaction in the typical operation process of the above degradation experiment respectively, it can be seen that after Co / PSB activates PMS to degrade AO7, the contents of Fe 2+ , Co 2+ decrease, and the corresponding contents of Fe 3+ , Co 3+ slightly increase, indicating that Fe 2+ , Co 2+ jointly participate in the process of activating PMS to degrade AO7. The synergistic effect of Fe and Co improves the catalytic activity of Co / PSB and promotes 1 O 2Generation of reactive oxygen species.

[0043] Figure 4 The magnetism of the raw sludge biochar and the Co / PSB catalyst was demonstrated. The magnetic saturation intensity of the raw sludge biochar was approximately 10 emu·g -1 and that of the Co / PSB catalyst was approximately 40 emu·g -1 ; the Co / PSB catalyst had stronger magnetism compared to the raw sludge biochar. The difference in saturation magnetization intensity might be due to the different forms of iron element, further indicating the formation of Fe 3 O 4 .

[0044] Figure 5 The effect of pH on the degradation of AO7 was demonstrated. Based on the typical operation process of the above degradation experiment, the pH of the reaction system was adjusted by acids and bases. The results showed that within the range of pH = 4.24 - 10.19, the degradation rate of AO7 could reach over 95% at 60 min, and the degradation rate also exceeded 90% at pH = 11.86, indicating that this system had a wide pH application range.

[0045] To investigate the stability of the Co / PSB catalyst, based on the typical operation process of the above degradation experiment, the present invention conducted a coexisting ion interference experiment. The experiment selected Cl - , NO 3 - , H 2 PO 4 - three common anions in water bodies to investigate the anti-ion interference of Co / PSB. The results were as Figure 6 shown. The concentration of anions had a relatively small effect on the degradation of AO7 in the system, while the type of anions had a relatively greater effect on the degradation of AO7 in the system. When the concentrations of Cl - , NO 3 - , H 2 PO 4 - were all 1.0 M, the removal rates of AO7 in the system could still reach 91.64%, 88.43%, and 98.17% respectively. The above results indicated that Co / PSB had strong anti-ion interference and excellent comprehensive stability.

[0046] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge, characterized in that: include: The paper sludge magnetic biochar-loaded catalyst is added to acid orange 7 sewage, and after adsorption equilibrium, peroxymonosulfate is added to start the reaction, and after the reaction is completed, the paper sludge magnetic biochar-loaded catalyst is recovered using a magnet; The preparation method of the papermaking sludge magnetic biochar-loaded catalyst comprises: drying the papermaking sludge after passing it through a 100-300 mesh screen, directly adding the dried powder into a Co(NO3)2 solution, wherein the ratio of the mass of the dried powder to the molar number of Co(NO3)2 in the Co(NO3)2 solution is 1 g:10-20 mmol, and after continuous stirring and mixing for 1-25 hours, solid-liquid separation, drying the solid, and pyrolyzing it in an argon atmosphere at a pyrolysis temperature of 540-560°C, and then washing and drying again to obtain the papermaking sludge magnetic biochar-loaded catalyst; The papermaking sludge magnetic biochar-loaded catalyst has the following phases: Fe2O3, Co3O4, CaCO3 and Fe3O4.

2. The method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge according to claim 1, characterized in that: In the method for degrading Acid Orange 7 using a papermaking sludge magnetic biochar-loaded catalyst, the ratio of the added mass of the papermaking sludge magnetic biochar-loaded catalyst to the mass of Acid Orange 7 in the Acid Orange 7 wastewater is 1-25:

10.

3. The method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge according to claim 1, characterized in that: In the method for degrading Acid Orange 7 using a papermaking sludge magnetic biochar-loaded catalyst, the content of Acid Orange 7 in the Acid Orange 7 wastewater is 1-200 mg / L.

4. The method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge according to claim 1, characterized in that: In the method for degrading Acid Orange 7 using a papermaking sludge magnetic biochar-loaded catalyst, the ratio of the added mass of permonosulfate to the added mass of the papermaking sludge magnetic biochar-loaded catalyst is 1-2:

1.

5. The method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge according to claim 1, characterized in that: In the method for degrading Acid Orange 7 using papermaking sludge magnetic biochar-loaded catalyst, the reaction temperature is 10-30°C.

6. The method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge according to claim 1, characterized in that: In the method for degrading Acid Orange 7 using a papermaking sludge magnetic biochar-loaded catalyst, the pH of the reaction system is 4-12.

7. The method for degrading Acid Orange 7 using magnetic biochar-loaded catalyst from papermaking sludge according to claim 1, characterized in that: In the method for degrading Acid Orange 7 using a papermaking sludge magnetic biochar-loaded catalyst, the reaction is accompanied by stirring at a stirring speed of 200-300 rpm.

8. The method for degrading Acid Orange 7 using magnetic biochar-supported catalyst from papermaking sludge according to claim 1, characterized in that: In the method for preparing the papermaking sludge magnetic biochar-loaded catalyst, the concentration of Co(NO3)2 in the Co(NO3)2 solution is 0.1-0.5 mol / L.

9. The method for degrading Acid Orange 7 using magnetic biochar-supported catalyst from papermaking sludge according to claim 1, characterized in that: In the method for preparing the papermaking sludge magnetic biochar-loaded catalyst, the pyrolysis time is 2 to 3 hours.

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