A ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst and preparation method thereof

Abstract

A ZnO / Ni(iso‑PeO)8 / nanocellulose composite photocatalyst and its preparation method, which relates to an inorganic-organic biomass composite photocatalytic material and its preparation method. The present invention aims to solve the technical problems of the existing zinc oxide-based photocatalyst with a narrow spectral response range, high carrier recombination rate, and the phthalocyanine-based photocatalyst being prone to aggregation, small specific surface area, and low catalytic efficiency. The composite photocatalyst of the present invention is a composite semiconductor material ZnO / Ni(iso‑PeO)8 loaded on nanocellulose. Preparation method: First, prepare ZnO powder; then prepare ZnO / Ni(iso‑PeO)8 powder in an alternating magnetic field, then dissolve it in chloroform, and then add cellulose and ultrasonically oscillate and freeze-dry to obtain the composite photocatalyst. After irradiating with a UV lamp for 60 minutes, the degradation rate of the composite photocatalyst for methylene blue solution reaches 98.5%, and it can be used in the field of photocatalysis.

Description

Technical Field

[0001] The invention relates to an inorganic-organic biomass composite photocatalytic material and a preparation method thereof. Background Art

[0002] There are many types of photocatalysts, such as inorganic photocatalysts and organic photocatalysts. Most organic materials have the advantages of low cost, high light absorption coefficient and large specific surface area, such as phthalocyanine, but the low catalytic efficiency and wide band gap of organic photocatalysts limit the application of organic materials in photocatalysis. Most inorganic materials have high efficiency, narrow band gap and good optical properties, such as zinc oxide, but the low toughness and poor dispersibility of inorganic materials limit their application in photocatalysis. Summary of the invention

[0003] The present invention aims to solve the technical problems of the existing zinc oxide (ZnO) photocatalyst having a narrow spectral response range, a high carrier recombination rate, and the photocatalyst being easy to aggregate, having a small specific surface area, and having a low catalytic efficiency, and to provide a ZnO / Ni(iso-PeO) 8 / Nanocellulose composite photocatalyst and preparation method thereof.

[0004] ZnO / Ni(iso-PeO) of the present invention 8 / Nanocellulose composite photocatalyst is a composite semiconductor material ZnO / Ni(iso-PeO) loaded on nanocellulose (CNF) 8 , among which the composite semiconductor material ZnO / Ni(iso-PeO) 8 The molar ratio of Zn to Ni is (4.3-4.8):1; the mass of nanocellulose (CNF) accounts for ZnO / Ni(iso-PeO) 8 / 3% to 5% of the mass of nanocellulose composite photocatalyst.

[0005] The above ZnO / Ni(iso-PeO) 8 The preparation method of nanocellulose composite photocatalyst is carried out according to the following steps:

[0006] 1. Add zinc acetate to deionized water, stir it magnetically to dissolve it, then add sodium hydroxide, and then add cetyltrimethylammonium bromide (CTAB) and continue stirring until it dissolves to obtain a uniformly mixed transparent solution; then add the transparent solution to a hydrothermal kettle, place the hydrothermal kettle in a furnace at a temperature of 110 to 120° C. to react for 4 to 6 hours, and the product obtained by the reaction is centrifugally cleaned and dried to obtain ZnO powder;

[0007] 2. Add 1.5×10 -3 ~1.7×10 -3mol 3,6-dihydroxyphthalonitrile, 0.33-0.37 g anhydrous nickel chloride, 15-20 mL isoamyl alcohol and 0.15-0.20 mL 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), weigh ZnO powder, 3,6-dihydroxyphthalonitrile, anhydrous nickel chloride, isoamyl alcohol and DBU; first add 3,6-dihydroxyphthalonitrile and anhydrous nickel chloride to the reactor, then add isoamyl alcohol, add DBU after dissolving, and finally add ZnO powder, mix well, place the reactor in an alternating magnetic field, heat to boiling reflux for 7-8 hours under nitrogen protection, and after the reaction is completed, remove most of the isoamyl alcohol by rotary evaporation, then add methanol for filtration, wash, and separate by chromatography to obtain blue-green ZnO / Ni(iso-PeO) 8 pink;

[0008] 3. ZnO / Ni(iso-PeO) precipitated in step 2 8 The powder was dissolved in chloroform, and then nanocellulose (CNF) was added and ultrasonically shaken for 30 to 40 minutes to obtain a mixed solution; the mixed solution was freeze-dried to obtain ZnO / Ni(iso-PeO) 8 / nanocellulose composite photocatalyst.

[0009] Furthermore, the molar ratio of zinc acetate, hexadecyltrimethylammonium bromide and sodium hydroxide in step 1 is 1:1:(2-3).

[0010] Furthermore, the reactor described in step three is placed in an alternating magnetic field by tightly winding the solenoid on the reactor in a single layer, the solenoid length L = 15 cm, the diameter D = 5.6 cm, the number of coil turns N = 70, the solenoid wire diameter is 2 mm, and an alternating voltage signal of 50 to 1000 Hz is applied to both ends of the solenoid to obtain an alternating magnetic field.

[0011] Furthermore, in step 3, ZnO / Ni(iso-PeO) 8 The mass ratio of powder to nanocellulose (CNF) is 1: (0.03-0.05).

[0012] Furthermore, the freeze-drying temperature in step three is -45 to -20°C.

[0013] ZnO / Ni(iso-PeO) of the present invention 8 / Nanocellulose composite photocatalyst is an inorganic-organic hybrid material composed of inorganic and organic components. It not only retains the original properties of inorganic and organic components, but also has the synergistic effect between the components at the interface, improving the carrier transmission capacity and light absorption capacity, thereby improving its photocatalytic effect. At the same time, whether the photocatalyst can be excited by light to produce electron-hole pairs is also related to its bandgap width. The narrower the bandgap width, the wider the light absorption range, and the easier it is to be excited by light.

[0014] ZnO / Ni(iso-PeO) of the present invention 8 / Nanocellulose composite photocatalyst uses unsaturated zinc ions coordinated on the surface of ZnO as a "template", 3,6-dihydroxyphthalonitrile as a "molecular fragment", isoamyl alcohol as a reaction solvent, and DBU liquid phase catalysis method to in situ synthesize hydrophobic nickel octaisopentylphthalocyanine (Ni(iso-PeO)) on the hydrophilic ZnO surface. 8 ), and simultaneously loaded it on cellulose fibers. Testing the ZnO / Ni(iso-PeO) 8 / Nanocellulose composite photocatalyst was found to have the advantage of a narrow band gap, which is more conducive to light absorption. The photocatalyst of the present invention was used to degrade a methylene blue solution. Under ultraviolet light irradiation for 60 minutes, the degradation rate of the methylene blue solution could reach 98.5%, and it had the advantages of good stability and high reproducibility. The obtained composite photocatalyst was tested and found to have the advantage of a narrow band gap, which is more conducive to light absorption and has a higher photocatalytic effect.

[0015] ZnO / Ni(iso-PeO) of the present invention 8 The nanocellulose composite photocatalyst uses biomass as raw material, has a wide source, abundant reserves, low pollution, is renewable, and has a low preparation cost. The composite photocatalyst of the present invention can be used in the field of photocatalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a schematic diagram of the structure of the reaction device in Example 1; in the figure, 1 is a reaction shell, 1-1 is a feed port, 1-2 is a discharge port, 2 is a jacket, 2-1 is a medium inlet, 2-2 is a medium outlet, 3 is a motor, 4 is a stirring paddle, and 5 is a solenoid;

[0017] Figure 2 is the XRD spectrum of the ZnO powder prepared in step 1 of Example 1;

[0018] Figure 3 is a scanning electron microscope photograph of ZnO prepared in step 1 of Example 1;

[0019] Figure 4 It is the ZnO / Ni(iso-PeO) prepared in step 1 of Example 1 8Scanning electron microscope photos of

[0020] Figure 5 It is the ZnO / Ni(iso-PeO) prepared in step 3 of Example 1 8 / SEM photos of CNF: left is low magnification, right is high magnification;

[0021] Figure 6 is the degradation curve of methylene blue by the photocatalytic material in Example 1;

[0022] Figure 7 The photocatalytic ZnO and ZnO / NiPc (iso-PeO) in Example 1 8 / CNF energy gap determination curve diagram;

[0023] Figure 8 The photocatalytic ZnO and ZnO / NiPc (iso-PeO) in Example 1 8 Schematic diagram of the energy level of photogenerated electron transfer in / CNF. DETAILED DESCRIPTION

[0024] The beneficial effects of the present invention are verified by the following examples:

[0025] Example 1: ZnO / Ni(iso-PeO) of this example 8 The preparation method of nanocellulose composite photocatalyst is carried out according to the following steps:

[0026] 1. According to the molar ratio of zinc acetate, hexadecyltrimethylammonium bromide and sodium hydroxide being 1:1:2.5, zinc acetate is added to deionized water, magnetic stirring is used to dissolve it, and then sodium hydroxide is added, and then hexadecyltrimethylammonium bromide (CTAB) is added and stirred continuously until it is dissolved to obtain a uniformly mixed transparent solution; the transparent solution is then added to a hydrothermal kettle, and the hydrothermal kettle is placed in a furnace at a temperature of 115°C to react for 5 hours. The product obtained by the reaction is centrifugally cleaned and dried to obtain ZnO powder;

[0027] 2. Build a reaction device. The structural diagram of the reaction device is as follows Figure 1 As shown, a jacket 2 is arranged outside the reaction shell 1, a stirring paddle 4 driven by a motor 3 is arranged inside the reaction shell 1, a feeding port 1-1 is arranged at the top of the reaction shell 1, and a discharging port 1-2 is arranged at the bottom; a medium inlet 2-1 and a medium outlet 2-2 are arranged at the jacket 2, and a heating medium or a cooling medium is input into the jacket 2 to control the temperature of the material in the reaction shell 1; a solenoid 5 is tightly wound in a single layer on the outer surface of the jacket 2, the height of the jacket 2 is 11.8 cm, and the diameter is 7.7 cm; the solenoid length L=15 cm, the solenoid diameter D=5.6 cm, the number of turns of the coil formed by the solenoid N=70, and the wire diameter of the solenoid wire is 2 mm;

[0028] Weigh 1g ZnO powder, 0.5×10 -3 mol of 3,6-dihydroxyphthalonitrile, 0.365g of anhydrous nickel chloride, 5mL of isoamyl alcohol and 0.05mL of DBU; first add 3,6-dihydroxyphthalonitrile and anhydrous nickel chloride to the reaction device, then add isoamyl alcohol, add DBU after dissolving, and finally add ZnO powder. After mixing evenly, apply an alternating voltage signal of 250Hz to both ends of the solenoid to generate an alternating magnetic field, and heat to boiling reflux for 7 hours under nitrogen protection. After the reaction is completed, rotary evaporation is performed to remove most of the isoamyl alcohol, and then 15mL of methanol is added for filtration, washing, and separation by chromatography column to obtain blue-green ZnO / Ni(iso-PeO) 8 Powder; The composite semiconductor material ZnO / Ni(iso-PeO) prepared in this step 8 The molar ratio of Zn to Ni is 4.3:1;

[0029] 3. 1.3 g of the blue-green ZnO / Ni(iso-PeO) precipitated in step 2 8 The powder was dissolved in 20 mL of chloroform to make ZnO / Ni(iso-PeO) 8 The mass concentration of the powder was 65 mg / mL, and then 0.04 g of nanocellulose (CNF) was added and ultrasonically shaken for 30 minutes to obtain a mixed solution; the mixed solution was freeze-dried at -40 °C to obtain ZnO / Ni(iso-PeO) 8 / nanocellulose composite photocatalyst, denoted as ZnO / Ni(iso-PeO) 8 / CNF. Through testing, it is known that in this step, the mass of nanocellulose accounts for ZnO / Ni(iso-PeO) 8 / 3% of the mass of nanocellulose composite photocatalyst.

[0030] The XRD spectrum of the ZnO powder obtained in step 1 of this embodiment is as follows: Figure 2 As shown, from Figure 2 It can be seen that the position of the main diffraction peak of the ZnO powder is consistent with that of the standard hexagonal wurtzite ZnO (JCPD36-1451), the peak is narrow and sharp, and there is no impurity peak, indicating that the main crystal phase of ZnO is wurtzite ZnO with high purity and good crystallinity.

[0031] The scanning electron microscope photograph of the ZnO powder obtained in step 1 of this embodiment is as follows Figure 3 ,from Figure 3 It can be seen that the particle size of ZnO powder is about 500 nm and the particles are agglomerated.

[0032] The ZnO / Ni(iso-PeO) obtained in step 1 of this embodiment 8The scanning electron microscope photo of the powder is as follows Figure 4 ,from Figure 4 It can be seen that the powder has granular and coarse rod shapes, and the particle size is about 1 μm.

[0033] The ZnO / Ni(iso-PeO) obtained in step 3 8 SEM photos of CNF Figure 5 As shown, from Figure 5 It can be seen that ZnO / Ni(iso-PeO) 8 / CNF is a composite semiconductor material ZnO / Ni(iso-PeO) loaded on nanocellulose (CNF) 8 , ZnO / Ni(iso-PeO) 8 The particle size in / CNF is about 0.5-1μm, the particles are relatively uniform, and the crystal structure is a three-dimensional micro-nano structure with a stronger sense of space, which is conducive to exposing more active sites and facilitating photocatalytic degradation.

[0034] Comparative Example 1: Preparation of Ni(iso-PeO) in this comparative example 8 Powder, the specific steps are as follows:

[0035] The reaction apparatus has the same structure as that of Example 1; 0.5×10 -3 mol of 3,6-dihydroxyphthalonitrile, 0.0314g of anhydrous nickel chloride, 5mL of isoamyl alcohol and 0.05mL of DBU; first add 3,6-dihydroxyphthalonitrile and anhydrous nickel chloride to the reaction device, then add isoamyl alcohol, add DBU after dissolving, mix evenly, apply 250Hz alternating voltage signal to both ends of the solenoid to generate an alternating magnetic field, and heat to boiling reflux for 7 hours under nitrogen protection. After the reaction is completed, most of the isoamyl alcohol is removed by rotary evaporation, and then 15mL of methanol is added for filtration, washing, and separation by chromatography column to obtain Ni(iso-PeO) 8 pink.

[0036] The ZnO powder prepared in step 1 of Example 1 and the Ni(iso-PeO) prepared in comparative example 1 were used. 8 Powder and ZnO / Ni(iso-PeO) prepared in step 3 of Example 1 8 / CNF were used as photocatalytic materials to test the photocatalytic performance of methylene blue. The test method is as follows: weigh 0.125g of methylene blue, dissolve it in deionized water to make a 25mg / L methylene blue aqueous solution, measure 100mL of the 25mg / L methylene blue solution, add 80mg of ZnO powder, 80mg of Ni(iso-PeO) 8 powder and 80mg ZnO / Ni(iso-PeO) 8 / CNF, using ultraviolet light source, a comparative experiment of photocatalytic degradation of methylene blue was carried out. Before the photocatalytic reaction, an adsorption equilibrium experiment was conducted for 1 hour without light to examine the physical adsorption performance of the catalyst on methylene blue. 4 mL of the solution was taken and filtered to record the initial absorbance of the photocatalytic reaction (C 0 ). After 1 hour of dark adsorption, the UV lamp was turned on to start illumination. Samples were taken at regular intervals. The photocatalytic reaction time was 120 minutes. The concentration change curve obtained with time is shown in Figure 6 As shown, from Figure 6 It can be seen that ZnO / Ni(iso-PeO) 8 / CNF has a better degradation effect on methylene blue than ZnO or Ni(iso-PeO) alone 8 As a photocatalyst, ZnO / Ni(iso-PeO) has good degradation effect. 8 Under the condition of ultraviolet light irradiation for 60 minutes, the degradation rate of methylene blue solution can reach 98.5%, which shows that through the composite, the micro-nano 3D structure can expose more active sites and effectively improve its photocatalytic degradation performance of methylene blue.

[0037] Figure 7 The photocatalytic ZnO and ZnO / Ni(iso-PeO) in Example 1 8 / CNF energy gap determination curve, which is based on UV-visible diffuse reflectance data and uses the Tauc equation αhν=A(hν-Eg) n , we get (αhν) 2 For the hν curve, A is a constant, h is Planck's constant, ν is the frequency of light, Eg is the band gap, and n = 1 / 2 for direct semiconductors. Figure 7 According to the nearly straight line relationship in the formula, draw a tangent line along the curve, and the intersection with the x-axis is the Eg value. Figure 7 It can be seen that ZnO and ZnO / Ni(iso-PeO) 8 The Eg values ​​of ZnO and ZnO / Ni(iso-PeO) were 3.37 and 3.22 eV respectively. The band gap narrowed after sensitization, indicating that the absorption wavelength has red-shifted toward the visible light direction, improving the problem of limited absorption spectrum of ZnO and thus improving the photocatalytic performance. 8 Schematic diagram of the energy level of photogenerated electron transfer in / CNF Figure 8 As shown. Figure 8 It can be seen that ZnO / Ni(iso-PeO) 8 / The energy band width of CNF becomes narrower, which is beneficial to improving the photocatalytic performance of the material.

[0038] The invention aims to solve the problems of narrow spectral response range of zinc oxide as photocatalyst and easy aggregation of phthalocyanine as photocatalyst. 8 / Cellulose is a sheet of nano-ZnO surface coordinated with unsaturated zinc ions as a "template", 3,6-dihydroxyphthalonitrile as a "molecular fragment", isopentanol as a reaction solvent, and DBU liquid phase catalysis is used to in situ synthesize hydrophobic nickel octaisopentylphthalocyanine (Ni(iso-PeO)) on the hydrophilic nano-ZnO surface. 8 ), and simultaneously loaded it on cellulose fibers to obtain a photosensitizer for the degradation of methylene blue with a photocatalytic efficiency of 98.5%.

Claims

1. A ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst, characterized in that: The composite photocatalyst is a composite semiconductor material ZnO / Ni(iso-PeO)8 loaded on nanocellulose, wherein the molar ratio of Zn to Ni in the composite semiconductor material ZnO / Ni(iso-PeO)8 is (4.3-4.8):1; the mass of nanocellulose accounts for 3%-5% of the mass of the ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst; the specific preparation method of the composite photocatalyst is as follows: first, zinc acetate is added to deionized water, magnetic stirring is used to dissolve it, then sodium hydroxide is added, and then hexadecyltrimethylammonium bromide is added and stirred continuously until dissolved to obtain a uniformly mixed transparent solution; then the transparent solution is added to a hydrothermal kettle, and the hydrothermal kettle is placed in a furnace at a temperature of 110-120°C for reaction for 4-6 hours, and the product obtained by the reaction is centrifugally cleaned and dried to obtain ZnO powder; second, 1.5×10 -3 ~1.7×10 -3 mol of 3,6-dihydroxyphthalonitrile, 0.05-0.15 g of anhydrous nickel chloride, 15-20 mL of isoamyl alcohol and 0.15-0.20 mL of 1,8-diazabicyclo[5,4,0]undec-7-ene, weigh ZnO powder, 3,6-dihydroxyphthalonitrile, anhydrous nickel chloride, isoamyl alcohol and 1,8-diazabicyclo[5,4,0]undec-7-ene; first add 3,6-dihydroxyphthalonitrile and anhydrous nickel chloride to the reactor, then add isoamyl alcohol, add 1,8-diazabicyclo[5,4,0]undec-7-ene after dissolving, and finally add After the ZnO powder is evenly mixed, the reactor is placed in an alternating magnetic field and heated to boiling reflux for 7 to 8 hours under nitrogen protection. After the reaction is completed, most of the isoamyl alcohol is removed by rotary evaporation, and then methanol is added for filtration and washing, and separation is performed by chromatography column to obtain ZnO / Ni(iso-PeO)8 powder; third, the precipitated ZnO / Ni(iso-PeO)8 powder of step 2 is dissolved in chloroform, and then nanocellulose is added, and ultrasonic vibration is performed for 30 to 40 minutes to obtain a mixed solution; the mixed solution is freeze-dried to obtain a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst.

2. A method for preparing a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst according to claim 1, characterized in that: The method proceeds as follows:

1. Add zinc acetate to deionized water, stir it magnetically to dissolve it, then add sodium hydroxide, and then add hexadecyltrimethylammonium bromide and continue stirring until it dissolves to obtain a uniformly mixed transparent solution; then add the transparent solution to a hydrothermal kettle, place the hydrothermal kettle in a furnace at a temperature of 110-120°C to react for 4-6 hours, and the product obtained by the reaction is centrifugally cleaned and dried to obtain ZnO powder; 2. Add 1.5×10 -3 ~1.7×10 -3 mol 3,6-dihydroxyphthalonitrile, 0.05-0.15 g anhydrous nickel chloride, 15-20 mL isopentanol and 0.15-0.20 mL 1,8-diazabicyclo[5,4,0]undec-7-ene, weigh ZnO powder, 3,6-dihydroxyphthalonitrile, anhydrous nickel chloride, isopentanol and 1,8-diazabicyclo[5,4,0]undec-7-ene; first, 3,6-dihydroxyphthalonitrile and anhydrous nickel chloride were mixed. Add nickel chloride water into the reactor, then add isoamyl alcohol, add 1,8-diazabicyclo[5,4,0]undec-7-ene after dissolving, and finally add ZnO powder. After mixing evenly, place the reactor in an alternating magnetic field, heat to boiling reflux for 7-8 hours under nitrogen protection, and after the reaction is completed, remove most of the isoamyl alcohol by rotary evaporation, add methanol for suction filtration, wash, and separate by chromatography column to obtain ZnO / Ni(iso-PeO)8 powder.

3. Dissolve the precipitated ZnO / Ni(iso-PeO)8 powder in chloroform, add nanocellulose, and ultrasonically vibrate for 30-40 minutes to obtain a mixed solution; freeze-dry the mixed solution to obtain a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst.

3. The method for preparing a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst according to claim 2, characterized in that: The molar ratio of zinc acetate, hexadecyltrimethylammonium bromide and sodium hydroxide described in step 1 is 1:1:(2-3).

4. The method for preparing a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst according to claim 2 or 3, characterized in that: The reactor described in step three is placed in an alternating magnetic field by tightly winding a solenoid around the reactor in a single layer. The length of the solenoid is L=15 cm, the diameter is D=5.6 cm, the number of turns of the coil is N=70, the diameter of the solenoid wire is 2 mm, and an alternating voltage signal of 50~1000 Hz is applied to both ends of the solenoid to obtain an alternating magnetic field.

5. The method for preparing a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst according to claim 2 or 3, characterized in that: In step three, the mass ratio of ZnO / Ni(iso-PeO)8 powder to nanocellulose is 1:(0.03~0.05).

6. The method for preparing a ZnO / Ni(iso-PeO)8 / nanocellulose composite photocatalyst according to claim 2 or 3, characterized in that: The freeze drying temperature in step 3 is -45 to -20°C.

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