Preparation method and application of papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material

Abstract

The invention discloses a preparation method and application of a papermaking sludge-based C-C / Si-O-Al interpenetrating network porous spherical composite material. The papermaking sludge is dried and ball-milled to a uniform powder, the papermaking sludge powder is carbonized under a nitrogen atmosphere to obtain porous sludge carbon, the porous sludge carbon, water glass and water are uniformly mixed, the mixture is dropwise added into hot silicone oil to form uniformly distributed papermaking sludge spheres, and the mixture is activated, reduced and dried to prepare an active papermaking sludge C-C / Si-O-Al interpenetrating network porous spherical composite material. The papermaking sludge-based C-C / Si-O-Al interpenetrating network porous spherical composite material obtained by the invention has excellent photocatalytic activity and stability for the organic pollutant tetracycline hydrochloride as a catalyst.

Description

Technical Field

[0001] The present invention relates to resource utilization of papermaking sludge and a preparation method and application of a CC / Si-O-Al interpenetrating network porous spherical composite material, and specifically relates to the preparation of a papermaking sludge carbon-based composite material containing mineral components such as silicon, aluminum, and iron, and the application of the composite material for photocatalytic degradation of tetracycline. The present invention belongs to water pollution treatment technology and the technical field of tetracycline photocatalytic degradation. Background Art

[0002] Tetracycline (TC) is a broad-spectrum antibiotic. Its abuse in medicine, animal husbandry, agriculture and other fields has led to an increase in its detectable concentration in wastewater. If this continues, humans will develop resistance to antibiotics. Traditional sewage treatment methods such as physical, biological and chemical methods are difficult to completely remove antibiotics from water bodies. Therefore, there is an urgent need to find cleaner and lower-consumption methods to effectively reduce tetracycline in the environment. As one of the advanced oxidation methods, photocatalytic technology is favored by various industries for its mild conditions, high efficiency and no secondary pollution when treating organic pollutants. At present, the catalysts commonly used in the field of photocatalysis are mostly synthetic semiconductor materials, whose synthesis steps are cumbersome and their economic value is not high. To solve this problem that seriously hinders the application of photocatalysis, there are many literatures that develop photocatalyst materials with rich component solid waste as precursors.

[0003] Papermaking sludge, the largest source of solid waste, contains significant amounts of inorganic (CaCO₃, polyaluminium ferric sulfate, SiO₂) and organic (cellulose, hemicellulose, and lignin) components. Similar to other solid wastes, the active species contained in papermaking sludge are difficult to directly utilize. However, it has been reported that solid waste containing elements such as Al, Si, and O can be structurally restructured to form a stable three-dimensional network.

[0004] Most solid wastes (slag, fly ash, red mud, coal gangue, etc.) contain photoactive elements, but most of them exist in a bonded, polymerized or chelated state. These forms are not conducive to electron transfer and cannot be directly used in the field of photocatalysis. Therefore, many scholars have tried to increase the possibility of photocatalytic degradation of pollutants by solid waste by loading active species. These methods have shown a certain effect in wastewater treatment, but their preparation process is complicated, their stability in water bodies is poor, and the leached metal ions may cause pollution to water bodies, which does not achieve the true meaning of "waste treatment with waste". To this end, it is necessary to find a suitable solid waste that can fully utilize its photoactive elements through simple treatment. Summary of the Invention

[0005] The present invention provides a papermaking sludge biochar-based composite material. The composite material is obtained by pyrolyzing and modifying papermaking sludge under a nitrogen atmosphere, contains a large amount of mineral components such as silicon, aluminum, iron, and calcium, and has photocatalytic activity without the need for external iron, nitrogen, or sulfur sources. The biochar obtained in the present invention is used to prepare CC / Si-O-Al interpenetrating network microspheres, thereby improving their stability in water bodies. The prepared papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material is used in photocatalytic technology as a catalyst for degrading organic matter (tetracycline) in sewage. The catalyst can be recycled in situ for multiple times while still maintaining high stability, and has great application potential.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material comprises the following steps:

[0008] (1) Drying the papermaking sludge and grinding it into a uniform powder using a ball mill;

[0009] (2) carbonizing the papermaking sludge powder obtained in step (1) under a nitrogen atmosphere to obtain porous sludge carbon;

[0010] (3) The porous sludge carbon, water glass and water obtained in step (2) are uniformly mixed, and the mixture is added dropwise to silicone oil and stirred to form uniformly distributed papermaking sludge spheres. After the addition is completed, the mixture is filtered and washed with ethanol, and then activated, reduced and dried to prepare an active papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material.

[0011] The heating rate of carbonization in step (2) is 1-20°C / min, the target temperature is 300-1000°C, and the holding time is 1-10h.

[0012] In step (3), the porous sludge charcoal, water glass and water are mixed in a mass ratio of 1:1:1 to 1:10:1.

[0013] In step (3), the temperature of the silicone oil is 40-100°C, the viscosity is 500-2000cs, and the stirring rate is 100-1200r / min; during activation, the papermaking sludge spheres and KOH are mixed in a mass ratio of 0.1-1:1, and then the mixture is heated to 200-900°C at a heating rate of 2-20°C / min under a nitrogen atmosphere, and calcined for 1-5h. The product is washed and dried to obtain activated papermaking sludge spheres; reduction is performed by dispersing the activated papermaking sludge spheres in ultrapure water, adding NaBH4 solution dropwise, the NaBH4 solution concentration is 8-12g / L, the NaBH4 in the NaBH4 solution is 0.1-1.1 times the mass of the activated papermaking sludge spheres, stirring and reacting for 1-30 hours after mixing, and the stirring rate is 20-500r / min; the drying environment is vacuum drying.

[0014] The present invention also provides a papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material prepared by the method, which is used as a catalyst to photodegrade tetracycline in wastewater. In the degradation test, 5 to 50 mg of the papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material is dispersed in an aqueous solution containing a reaction substrate (5 to 100 mg / L tetracycline hydrochloride TC solution), with a pH value of 3 to 11. The photocatalytic reaction is carried out in a quartz reactor, the light source is a xenon lamp, and before irradiation, the suspension is magnetically stirred in the dark to establish adsorption-desorption equilibrium. Equal amounts of the suspension are intermittently withdrawn from the reactor, and solid impurities are removed using an organic syringe filter. The residual TC concentration is measured and analyzed using a high-performance liquid chromatograph (HPLC, Waters 2695 series), and the characteristic absorption peak is at 266 nm.

[0015] Compared with the prior art, the present invention has the following advantages and effects:

[0016] The present invention proposes a simple and clean method for preparing papermaking sludge-based CC / Si-O-Al interpenetrating network microspheres, and concludes that the intrinsic defects caused by metals and the reduced electron transfer resistance are the essential reasons why low-cost carbon-defect-based papermaking sludge microspheres can remove difficult-to-degrade substances in complex water bodies. At the same time, this structure can provide a transmission channel for electrons generated by photoexcitation, thereby achieving effective separation of photogenerated carriers. During the gelation process, some photoactive elements such as Fe also participate in the formation of the skeleton structure, which is not conducive to electron generation. The present invention increases the defect sites on the sludge surface and fully exposes Fe species through alkaline activation, thereby improving its photoactivity.

[0017] The present invention creatively proposes a method for preparing a new solid waste-based catalyst. For the first time, the active metals inherent in papermaking sludge carbon are used to prepare defective spherical photocatalysts. The defective papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material prepared by suspension polymerization, chemical etching and reduction has a high specific surface area and a uniform mesoporous structure, a rough surface, a wide absorption range, and a narrow band gap. It can effectively inhibit the recombination of photogenerated electrons and holes, and has excellent optical properties such as high photocurrent and small impedance. At the same time, it has high photocatalytic activity and can effectively degrade organic pollutants.

[0018] The present invention provides a method for preparing a papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material and its application as a catalyst for the photocatalytic degradation of tetracycline, which can effectively remove organic pollutants and has the advantages of simple process, convenient operation, low cost, easy recycling and reuse, stable performance, etc., can achieve rapid degradation of organic pollutants, and has good application prospects in the actual treatment of wastewater containing organic pollutants (such as tetracycline).

[0019] The present invention realizes "waste treatment with waste", has simple process operation, is practical, and is green and environmentally friendly. It also achieves wastewater treatment and efficient degradation of tetracycline at the same time. Using papermaking sludge carbon as a precursor for synthesizing CC / Si-O-Al interpenetrating network microspheres can not only solve the instability of carbon-based materials in water bodies, but also expand the reaction diffusion space, providing a place for photocatalytic degradation reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a SEM image of the psBC prepared in Example 1 of the present invention;

[0021] Figure 2 This is the SEM image of CC / Si-O-Al-1 prepared in Example 1 of the present invention;

[0022] Figure 3 This is the SEM image of CC / Si-O-Al-2 prepared in Example 2 of the present invention;

[0023] Figure 4 This is the SEM image of CC / Si-O-Al-3 obtained in Example 3 of the present invention;

[0024] Figure 5 This is the XRD pattern of CC / Si-O-Al-3 obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, implementation scheme, and application prospects of the present invention clearer, the present invention is further described below with reference to specific examples. The simulated wastewater used in the examples was prepared by dissolving tetracycline hydrochloride (98%) in water, and its pH value was adjusted using dilute hydrochloric acid and sodium hydroxide. The water glass used in the examples was purchased from Guangzhou Suixin Chemical Co., Ltd., wherein the Na2O content was 26% and the SiO2 content was 8.2%.

[0026] Example 1

[0027] A method for preparing a papermaking sludge CC / Si-O-Al interpenetrating network porous spherical composite material specifically comprises the following steps:

[0028] (1) Papermaking sludge is dried and ground before use to obtain a powder with uniform particle size (180-250 μm);

[0029] (2) carbonizing the papermaking sludge powder obtained in step (1) in a tubular furnace under a nitrogen atmosphere, heating the temperature to 500° C. at a heating rate of 2° C. / min, and maintaining the temperature for 2 h to obtain porous sludge carbon (psBC);

[0030] (3) The porous sludge carbon obtained in step (2), water glass, and water are mixed in a mass ratio of 1:1:1, and the mixture is added dropwise to hot silicone oil and stirred to form uniformly distributed papermaking sludge spheres in the silicone oil, wherein the silicone oil temperature is 70°C, the viscosity is 600 cs, and the stirring rate is 700 r / min. After the addition is completed, the mixture is filtered and washed with ethanol. The obtained papermaking sludge spheres are recorded as CC / Si-O-Al;

[0031] After activation, the papermaking sludge spheres and KOH were mixed in a mass ratio of 1:1, and then heated to 300°C at a heating rate of 2°C / min under a nitrogen atmosphere, calcined for 1 hour, and washed and dried to obtain activated porous papermaking sludge microspheres;

[0032] 10 g of activated paper sludge spheres were dispersed in 50 mL of ultrapure water, and NaBH4 solution was added dropwise. The concentration of NaBH4 solution was 12 g / L, and the NaBH4 in the NaBH4 solution was 1.1 times the mass of the activated paper sludge spheres. After mixing, the mixture was stirred for 20 hours at a stirring rate of 500 r / min. The mixture was then filtered, washed with water, and vacuum-dried to obtain an activated paper sludge CC / Si-O-Al interpenetrating network porous spherical composite material, recorded as CC / Si-O-Al-1.

[0033] Example 2

[0034] A method for preparing a papermaking sludge CC / Si-O-Al interpenetrating network porous spherical composite material specifically comprises the following steps:

[0035] (1) Papermaking sludge is dried and ground before use to obtain a powder with uniform particle size (180-250 μm);

[0036] (2) carbonizing the papermaking sludge powder in step (1) in a tubular furnace under a nitrogen atmosphere, heating the temperature to 600°C at a heating rate of 5°C / min, and keeping the temperature for 1.5 hours to obtain porous sludge carbon (psBC);

[0037] (3) The porous sludge carbon obtained in step (2), water glass, and water are mixed in a mass ratio of 1:2:1, and the mixture is added dropwise to hot silicone oil and stirred to form uniformly distributed papermaking sludge spheres, wherein the silicone oil temperature is 70°C, the viscosity is 1200 cs, and the stirring rate is 800 r / min. After the addition is completed, the mixture is filtered and washed with ethanol. The obtained papermaking sludge spheres are recorded as CC / Si-O-Al;

[0038] After activation, the papermaking sludge spheres and KOH were mixed in a mass ratio of 0.5:1, and then heated to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere for 3 hours. After washing and drying, porous papermaking sludge microspheres were obtained;

[0039] 10 g of activated paper sludge spheres were dispersed in 50 mL of ultrapure water, and NaBH4 solution was added dropwise. The concentration of NaBH4 solution was 10 g / L, and the NaBH4 in the NaBH4 solution was 1 times the mass of the activated paper sludge spheres. After mixing, the mixture was stirred for 30 hours at a stirring rate of 300 r / min. The mixture was then filtered, washed with water, and vacuum-dried to obtain an activated paper sludge CC / Si-O-Al interpenetrating network porous spherical composite material CC / Si-O-Al-2.

[0040] Example 3

[0041] A method for preparing a papermaking sludge CC / Si-O-Al interpenetrating network porous spherical composite material specifically comprises the following steps:

[0042] (1) Papermaking sludge is dried and ground before use to obtain a powder with uniform particle size (180-250 μm);

[0043] (2) carbonizing the papermaking sludge powder obtained in step (1) in a tubular furnace under a nitrogen atmosphere, heating the temperature to 800°C at a heating rate of 10°C / min, and keeping the temperature for 1 hour to obtain porous sludge carbon (psBC);

[0044] (3) The porous sludge carbon obtained in step (2), water glass, and water are mixed in a mass ratio of 1:3:1, and the mixture is added dropwise to hot silicone oil and stirred to form uniformly distributed papermaking sludge spheres, wherein the silicone oil temperature is 80°C, the viscosity is 1400 cs, and the stirring rate is 1000 r / min. After the dropwise addition is completed, the mixture is filtered and washed with ethanol. The obtained papermaking sludge spheres are recorded as CC / Si-O-Al;

[0045] After activation, the papermaking sludge spheres and KOH were mixed in a mass ratio of 0.3:1, and then heated to 700°C at a heating rate of 10°C / min under a nitrogen atmosphere, calcined for 2 hours, and dried and washed to obtain activated porous papermaking sludge microspheres;

[0046] 10 g of activated paper sludge spheres were dispersed in 50 mL of ultrapure water, and NaBH4 solution was added dropwise. The concentration of NaBH4 solution was 8 g / L, and the NaBH4 in the NaBH4 solution was 0.1 times the mass of the activated paper sludge spheres. After mixing, the mixture was stirred for 1 hour at a stirring rate of 20 r / min. The mixture was then filtered, washed with water, and vacuum-dried to obtain an activated paper sludge CC / Si-O-Al interpenetrating network porous spherical composite material CC / Si-O-Al-3.

[0047] Figure 1 The synthetic precursor psBC of CC / Si-O-Al-1 is shown to be a multilayered block with uniformly distributed nanoparticles. The mineral components of papermaking sludge undergo a morphological transformation under a high-temperature, oxygen-limited atmosphere. Further EDS analysis results show that the Fe and S elements correspond completely, indicating that these nanoparticles are Fe-S species. In addition, the uniform distribution of inherent components such as Ca, Al, and Si will contribute to the formation of the polymer microstructure. These Fe species can serve as active centers for photocatalysis to promote the reaction. Under the action of alkaline activators, the Ca, Al, and Si components undergo dissolution and polymerization to form CC / Si-O-Al spheres with a relatively dense structure. The functional groups and intrinsic carbon defects contained on the surface of biochar can accelerate the electron transfer rate, change the electronic structure, reduce the band gap value of the catalyst, and accelerate the generation of free radicals.

[0048] Figure 2 、 Figure 3 and Figure 4The SEM images are CC / Si-O-Al-1, CC / Si-O-Al-2, and CC / Si-O-Al-3, respectively. As the proportion of the activator increases, the surface of the obtained papermaking sludge microspheres gradually becomes rougher, the internal pores gradually increase, and the pore volume becomes larger. After the papermaking sludge microspheres are treated with KOH, the pore volume and pore diameter both increase, which may be due to the generation of carbon defects caused by alkali. There are relatively neatly arranged pores inside the papermaking sludge. These characteristics can provide diffusion and reaction sites for the catalysis of tetracycline molecules on the catalyst surface, increase the internal diffusion rate of the papermaking sludge microspheres and reduce the reaction barrier. The present invention successfully constructs a porous carbon skeleton material with a high reaction space.

[0049] Figure 5 This is the XRD pattern of CC / Si-O-Al-3 obtained in Example 4 of the present invention. Compared with CC / Si-O-Al, it can be found that after activation and reduction of CC / Si-O-Al, the crystalline structure of the material does not change much, indicating that its structure is relatively stable, which is conducive to the catalyst continuing to play an efficient role in water.

[0050] 20 mg of the composite material prepared in Examples 1-3 was dispersed in an aqueous solution containing the reaction substrate (i.e., a 10 mg / L TC solution) and subjected to a photocatalytic reaction. The photocatalytic reaction was carried out in a 100 mL quartz reactor. The reaction temperature was maintained at 25° C. using a circulating water glass jacket. The light source was a 500 W xenon lamp. Simultaneously with the irradiation, a blank control group with the same conditions (10 mg catalysts, 10 mg / L TC solution) was magnetically stirred in the dark for 120 min. An equal amount of the suspension was intermittently withdrawn from the reactor and solid impurities were removed using a 0.2 μm organic syringe filter. The TC sample was monitored using a high performance liquid chromatograph (HPLC, Waters 2695 series) equipped with a Waters 2487 UV detector and a Shim-pack GWS C18 The results were as follows: a 5 μm chromatographic column (250 mm × 4.6 mm) was used, the mobile phase was a binary mixture consisting of 0.01 mol / L oxalic acid aqueous solution and methanol aqueous solution (60:40 v / v), the flow rate was 1 mL / min, and the detection wavelength of tetracycline hydrochloride was 264 nm. The specific results are shown in Table 1. It can be seen from the table that the products of Examples 1-3 have a good degradation effect on tetracycline hydrochloride, and the degradation rate of Example 2 is the highest, reaching 87.8%. Compared with the unactivated paper sludge microspheres CC / Si-O-Al prepared in Example 3, activation and reduction improve the degradation ability of tetracycline. It can be seen that in addition to the abundant metal sites on the surface of the paper sludge microspheres, the activation and reduction processes increase the body defects and pore defects on the surface, providing sufficient reaction sites for the degradation of the reactants.

[0051] Table 1

[0052] project Degradation rate of tetracycline (%) CC / Si-O-Al of Example 3 45.3％ Example 1 62％ Example 2 87.8％ Example 3 84.8％

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material, characterized in that: The specific steps include: (1) Papermaking sludge is dried and ball-milled to a uniform powder; (2) carbonizing the papermaking sludge powder obtained in step (1) under a nitrogen atmosphere to obtain porous sludge carbon; (3) The porous sludge carbon, water glass and water obtained in step (2) are uniformly mixed, and the mixture is added dropwise to silicone oil and stirred to form uniformly distributed papermaking sludge spheres. After the addition is completed, the mixture is filtered and washed with ethanol, and then activated with KOH, reduced and dried to prepare a papermaking sludge-based CC / Si-O-Al interpenetrating network porous spherical composite material.

2. The preparation method according to claim 1, characterized in that The heating rate of carbonization in step (2) is 1~20℃ / min, the target temperature is 300~1000℃, and the holding time is 1~10h.

3. The preparation method according to claim 1, characterized in that: In step (3), the porous sludge charcoal, water glass and water are mixed in a mass ratio of 1:1:1 to 1:10:

1.

4. The preparation method according to claim 1, characterized in that In step (3), the temperature of the silicone oil is 40-100°C, the viscosity is 500-2000 cs, and the stirring rate is 100-1200 r / min.

5. The preparation method according to claim 1, characterized in that: During the activation step (3), the papermaking sludge spheres and KOH are mixed in a mass ratio of 0.1 to 1:1, and then the mixture is heated to 200 to 900° C. at a heating rate of 2 to 20° C. / min under a nitrogen atmosphere, and calcined for 1 to 5 hours. The product is washed and dried to obtain activated papermaking sludge spheres.

6. The preparation method according to claim 5, characterized in that: In step (3), the reduction step comprises dispersing the activated papermaking sludge spheres in ultrapure water, adding a NaBH4 solution dropwise, wherein the concentration of the NaBH4 solution is 8 to 12 g / L, and the NaBH4 in the NaBH4 solution is 0.1 to 1.1 times the mass of the activated papermaking sludge spheres, mixing, and stirring for 1 to 30 hours at a stirring rate of 20 to 500 r / min.

7. The papermaking sludge CC / Si-O-Al interpenetrating network porous spherical composite material prepared by the method of claim 1 is used as a catalyst to photodegrade tetracycline in wastewater.

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