Method for strengthening degradation and conversion of lignocellulose through photo-Fenton treatment

Abstract

The invention discloses a method for strengthening degradation and conversion of lignocellulose through photo-Fenton treatment, which comprises the following steps: (1) mixing crushed straws with a hydrogen peroxide solution, activated carbon doped nickel ferrite nanoparticles and deionized water to obtain a mixed solution; (2) carrying out white light irradiation on the mixed solution while carrying out oscillation treatment, and then carrying out solid-liquid separation to obtain supernate and residues; and (3) performing enzymolysis saccharification on the residues. The straw is pretreated by adopting a photocatalysis and Fenton reaction synergistic mode, so that the effects of degrading and removing lignin, well retaining cellulose and efficiently performing enzymolysis saccharification are achieved.

Description

Technical Field

[0001] This invention belongs to the field of lignocellulose raw material pretreatment technology, specifically relating to a method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment. Background Technology

[0002] Lignocellulosic biomass is the most abundant renewable resource on Earth. It can be used to produce a variety of high-value products and energy. It is considered a good alternative fuel or energy source and plays an important supporting role in the development of zero carbon emissions and a circular economy.

[0003] Lignocellulose biomass is a natural organic material with a complex structure mainly composed of cross-linked cellulose, hemicellulose, and lignin. It typically requires pretreatment to promote the depolymerization of lignin and cellulose and enhance the enzymatic accessibility of cellulose and hemicellulose. To date, numerous pretreatment methods for lignocellulose have been reported, and in recent years there has been a growing trend towards low energy consumption, low cost, high efficiency, and mild conditions. Among these, photocatalytic treatment is the most prominent.

[0004] As an advanced oxidation process, photocatalysis stimulates the generation of reactive oxygen species (ROS). These ROS attack the lignin structure, activating OH bonds to form alkoxy groups, which weaken adjacent C-C bonds, causing aromatic ring cleavage and promoting the decomposition of lignocellulose biomass. However, due to the robust crystalline structure of lignocellulose, photocatalysis faces a common mass transfer limitation problem in the conversion of lignocellulose biomass, making it difficult for ROS to reach the lignocellulose macromolecules, resulting in low degradation efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment. By employing a synergistic approach of photocatalysis and Fenton reaction, straw is pretreated, achieving the effects of lignin degradation and removal, good retention of cellulose, and efficient enzymatic hydrolysis and saccharification. This is a novel green method for achieving efficient pretreatment of lignocellulose.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a method for photo-Fenton treatment to enhance the degradation and conversion of lignocellulose, the method comprising the following steps:

[0008] (1) The crushed straw was mixed with hydrogen peroxide solution, activated carbon doped with nickel ferrite nanoparticles and deionized water to obtain a mixture;

[0009] (2) Irradiate the mixture with white light while stirring, and then perform solid-liquid separation to obtain supernatant and residue;

[0010] (3) The residue is enzymatically hydrolyzed and saccharified.

[0011] In step (1), the particle size of the straw is 20-40 mesh.

[0012] In step (1), the mass concentration of hydrogen peroxide in the mixture is 1.0~3.5%; the concentration of activated carbon-doped nickel ferrite nanoparticles is 2~6 g / L; and the concentration of straw is 0.1 g / mL. Preferably, the mass concentration of hydrogen peroxide is 2.5%; and the concentration of activated carbon-doped nickel ferrite nanoparticles is 4 g / L.

[0013] In step (2), the light intensity of the white light is 3000~7000 W / m²; the irradiation time is 24~72 h. Preferably, the light intensity of the white light is 5000 W / m²; the irradiation time is 36 h.

[0014] In step (3), the enzymatic hydrolysis and saccharification method is as follows: disperse the residue in citrate buffer, add Cellic® CTec3 HS cellulase, and stir at 45~55℃ for 65~75h.

[0015] Furthermore, the concentration of the citrate buffer is 0.05 M and the pH is 4.8; the mass concentration of the residue in the citrate buffer is 5%.

[0016] The Cellic® CTec3 HS cellulase addition amount is 10 FPU / g residue.

[0017] This invention provides a method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment. It employs a synergistic approach of photocatalysis and Fenton reaction to pretreat straw, achieving lignin degradation and removal, good cellulose retention, and efficient enzymatic hydrolysis and saccharification. The cellulose retention rate in the straw is above 80%, the lignin degradation and removal rate is above 20%, the total phenol content is below 15 mg / L, and the enzymatic hydrolysis rate is above 60%. Under the preferred treatment conditions of this invention, the cellulose retention rate in the straw is above 90%, the lignin degradation and removal rate is above 30%, the total phenol content is below 8 mg / L, and the enzymatic hydrolysis rate is above 85%. This is a novel green method for achieving efficient pretreatment of lignocellulose.

[0018] Compared with the prior art, the present invention has the following advantages and effects:

[0019] 1. This invention employs photo-Fenton treatment of lignocellulose. Its photo-Fenton reaction system has a strong visible light absorption capacity, which excites the generation of photogenerated electrons, accelerates the transition of photogenerated electrons, generates high photocurrent density, superoxide radicals and hydroxyl radicals, effectively causing the separation of lignocellulose components, thereby degrading and removing lignin, retaining cellulose well and efficiently enzymatically hydrolyzing and saccharifying it.

[0020] 2. The photo-Fenton system constructed in this invention achieves higher cellulose retention, lignin removal, and enzymatic hydrolysis rates than those obtained under visible light catalysis and pretreatment with only hydrogen peroxide and AC-NiFe2O4 nanoparticles. It can synergistically exert photocatalytic and Fenton reaction effects, thereby effectively promoting the degradation and enzymatic transformation of lignocellulose. Attached Figure Description

[0021] Figure 1 The effects of different light-Fenton treatment conditions on cellulose retention, lignin removal, and total phenol content in the supernatant in Example 1 are shown, where (a) represents the effect of light intensity of 3000 W / m². 2 (a) Effect of different reaction times with nanoparticle addition amount of 4 g / L and hydrogen peroxide concentration of 1%; (b) Effect of different reaction times with light intensity of 3000 W / m 2 (c) Effect of different concentrations of nanoparticles at a hydrogen peroxide concentration of 1% and a reaction time of 36 h; (d) Effect of different light intensities at a nanoparticle concentration of 4 g / L, a hydrogen peroxide concentration of 1%, and a reaction time of 36 h; (e) Effect of different concentrations of nanoparticles at a light intensity of 5000 W / m². 2 The effect of adding different concentrations of hydrogen peroxide was investigated when the amount of nanoparticles added was 4 g / L and the reaction time was 36 h.

[0022] Figure 2 The effect of different light Fenton treatment conditions on enzyme hydrolysis rate in Example 2 is shown, where (a) is the light intensity of 3000 W / m 2 (a) Effect of different reaction times with nanoparticle addition amount of 4 g / L and hydrogen peroxide concentration of 1%; (b) Effect of different reaction times with light intensity of 3000 W / m 2 (c) Effect of different concentrations of nanoparticles at a hydrogen peroxide concentration of 1% and a reaction time of 36 h; (d) Effect of different light intensities at a nanoparticle concentration of 4 g / L, a hydrogen peroxide concentration of 1%, and a reaction time of 36 h; (e) Effect of different concentrations of nanoparticles at a light intensity of 5000 W / m². 2 The effect of adding different concentrations of hydrogen peroxide was investigated when the amount of nanoparticles added was 4 g / L and the reaction time was 36 h.

[0023] Figure 3 The images show the cyclic voltammetry curve (a), linear scan curve (b), band gap diagram (c), and changes in hydrogen peroxide content, superoxide anion content, and hydroxyl radical content (d) under the photo-Fenton treatment conditions in Example 3.

[0024] Figure 4The composition and structure of the photo-Fenton treated material under photo-Fenton treatment conditions in Example 3 are characterized, wherein (a) is an X-ray diffraction pattern; (b) is an infrared spectrum; (c) is a scanning electron microscope image of the untreated material; and (d) is a scanning electron microscope image of the photo-Fenton treated material.

[0025] Figure 5 The images show X-ray photoelectron spectroscopy (XPS) analysis of the photo-Fenton treated material under the photo-Fenton treatment conditions in Example 3. (a) is the total XPS spectrum of the untreated material; (b) is the C1S XPS spectrum of the untreated material; (c) is the total XPS spectrum of the photo-Fenton treated material; and (d) is the C1S XPS spectrum of the photo-Fenton treated material.

[0026] Figure 6 The graph shows a comparative analysis of the cellulose retention rate, lignin removal rate, and enzyme hydrolysis rate of straw treated using the methods in Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the embodiments.

[0028] The rice straw was purchased from Shuyang Caizhiyan Gardening Supplies Co., Ltd., Shuyang County, Suqian City, Jiangsu Province.

[0029] The hydrogen peroxide solution was purchased from Sinopharm Chemical Reagent Co., Ltd., with an initial concentration of 30%.

[0030] Activated carbon-doped nickel ferrite nanoparticles (AC-NiFe2O4 NPs) were synthesized using the green sol-gel method, specifically according to the method in Example 1 of the patent published in CN 117025471 A entitled "A Method for Constructing and Applying an Activated Carbon-Doped Nickel Ferrite Nanoparticle / Klebsiella Biohybrid System".

[0031] The intensity of white light was measured using an illuminance meter (DLY-1802, Delixi).

[0032] Glucose and xylose concentrations were determined using high-performance liquid chromatography. The glucose yield conversion formula is: (glucose concentration in hydrolysate * 20 mL * 0.9) / cellulose content in matrix * 100%, where glucose yield is the enzyme hydrolysis rate.

[0033] The total phenol content was determined using the Folin-Ciocalteu method.

[0034] The contents of lignin, cellulose, and hemicellulose components in the residue were determined using the biomass three-element determination procedure developed by the National Renewable Energy Laboratory (NREL). The sugar concentration was detected by high performance liquid chromatography (HPLC) using a differential detector, an Aminex HPX~87H hydrogen ion exchange column, a column temperature of 40℃, a mobile phase of 5 mmol / L H2SO4, and a flow rate of 0.6 mL / min.

[0035] The conversion formulas for cellulose retention rate and lignin removal rate are as follows: Cellulose retention rate (%) = Cellulose content in the pretreated residue / Cellulose content in the original rice straw * 100%; Lignin removal rate (%) = (1 - Lignin content in the solid residue) / Lignin content in the original rice straw * 100%.

[0036] The changes in photocurrent and potential were detected using an electrochemical workstation (CHI 760E).

[0037] The band gap is determined by detecting ultraviolet-visible absorption spectroscopy (UV-vis) and converting it according to the equation αhv=A(hv-Eg)n / 2.

[0038] Hydrogen peroxide and superoxide anion contents were detected using hydrogen peroxide content reagent kits and superoxide anion reagent kits, respectively; hydroxyl radical contents were detected using the salicylic acid method.

[0039] Example 1: Photo-Fenton treatment of lignocellulose raw materials

[0040] Rice straw is air-dried at room temperature, then chopped into 2 cm lengths using a shredder, and further pulverized using a high-speed grinder. The pulverized material was passed through 20- and 40-mesh sieves. Straw powder of 20-40 mesh size was taken and added to 150 mL Erlenmeyer flasks at a sample size of 5.00 g / flask. Hydrogen peroxide solution was added at concentrations of 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%, respectively. Activated carbon-doped nickel ferrite nanoparticles (AC-NiFe2O4NPs) were added at concentrations of 2, 3, 4, 5, and 6 g / L. Deionized water was then added to bring the final reaction volume to 50 mL. The flask was sealed with a high-transmittance sealing film and placed 10 cm under an LED white light source with a working wavelength range of 450-700 nm on a constant-temperature oscillator to simulate natural visible light. The light intensity was adjusted to 3000, 4000, 5000, 6000, and 7000 W / m² by adjusting the length of the LED white light strip. The flask was operated at 30℃ and a rotation speed of 200 rpm. The reaction was carried out at rpm for 24, 36, 48, 60, and 72 h. After the reaction was completed, all reactants were removed, filtered using a Buchner funnel, and centrifuged at 4000 r / min to achieve solid-liquid separation. The supernatant obtained was further filtered through a 0.22 μm microporous membrane and used to detect the contents of glucose, xylose, and total phenols.

[0041] The pretreated residue was used in two ways: one part was used to detect the content of lignin, cellulose, and hemicellulose components, and to further calculate the cellulose retention rate and lignin removal rate; the other part was washed 2-3 times with deionized water to remove residual hydrogen peroxide and soluble byproducts, and unreacted AC-NiFe2O4 NPs were recovered by attracting with a strong magnet. The washed residue was dried in a constant temperature oven at 105℃ until constant weight, weighed, and used for subsequent cellulose enzymatic hydrolysis and saccharification.

[0042] The lignocellulose components and reducing sugar concentrations under different light-Fenton treatment conditions are shown in Table 1.

[0043] Table 1. Lignocellulose components and reducing sugar concentrations under different light-Fenton treatments

[0044]

[0045] As shown in Table 1, the lignocellulose content of rice straw changed significantly after photo-Fenton treatment, and a certain concentration of reducing sugars—glucose, xylose, and arabinose—was produced. The production of these reducing sugars mainly stemmed from the partial degradation of cellulose and hemicellulose. Simultaneously, lignin degradation also produced some phenolic compounds. Figure 1 The results showed that the optimal photo-Fenton reaction time was 36 h, the optimal nanoparticle addition amount was 4 g / L, and the optimal light intensity was 5000 W / m². 2Under the condition of hydrogen peroxide concentration of 2.5%, the lignin removal rate is the highest, the cellulose retention rate is relatively high, and the total phenol content is relatively low. It can be preliminarily determined that the above reaction condition combination is the preferred photo-Fenton treatment condition.

[0046] Example 2 Enzymatic hydrolysis and saccharification of pretreated residue

[0047] The washing and drying residue obtained in Example 1 was added at a concentration of 5% (w / v) to a conical flask containing 20 mL of 0.05 M, pH 4.8 citrate buffer. Cellic® CTec3 HS cellulase (Novozymes) was then added at a concentration of 10 FPU / g dry matrix. The flask was then treated at 50°C and 150 rpm for 72 h using a constant temperature shaker. The hydrolysis products were collected and centrifuged at 10000 r / min for 2 min. The supernatant was filtered through a 0.22 μm microporous membrane, and the glucose content was determined by high-performance liquid chromatography (HPLC). The glucose yield was then calculated, which is the enzyme hydrolysis rate. The results are as follows: Figure 2 As shown, the optimal conditions for the photo-Fenton reaction were 36 h, 4 g / L of nanoparticles, and 5000 W / m² of light intensity. 2 The enzyme hydrolysis rate was highest when the hydrogen peroxide concentration was 2.5%. Based on the results of Example 1, the above reaction conditions were further determined to be the preferred photo-Fenton treatment conditions.

[0048] Example 3: Dynamics of electron transfer and free radical generation under preferred photo-Fenton treatment conditions

[0049] A method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment includes the following steps:

[0050] Rice straw was air-dried at room temperature, then chopped to approximately 2 cm in length using a shredder, and further pulverized using a high-speed grinder. The pulverized material was passed through 20 and 40 mesh sieves, and straw powder of 20-40 mesh size was taken and added to a 150 mL Erlenmeyer flask at a sample size of 5.00 g / flask. Hydrogen peroxide solution was added at a concentration of 2.5%, and activated carbon-doped nickel ferrite nanoparticles (AC-NiFe2O4 NPs) were added at a concentration of 4 g / L. Deionized water was then added to bring the final reaction volume to 50 mL. The flask was then sealed with a high-transmittance sealing film and placed 10 cm under an LED white light source with a working wavelength range of 450-700 nm on a constant-temperature oscillator to simulate natural visible light. The light intensity was adjusted to 5000 W / m² by adjusting the length of the LED white light strip, and the reaction was carried out at 30℃ and 200 rpm for 36 h. After the reaction was completed, all the reactants were removed, filtered using a Buchner funnel, and centrifuged at 4000 r / min to achieve solid-liquid separation, obtaining the supernatant and residue.

[0051] The photocurrent, potential changes, and band gap of the above-mentioned photo-Fenton reaction system were detected, and the changes in the contents of hydrogen peroxide, superoxide anion, and hydroxyl radicals during the reaction were monitored. The results are as follows: Figure 3 As shown.

[0052] Figure 3 Figure (a) shows that the cyclic voltammetry curves of both the photo-Fenton system and AC-NiFe2O4 NPs exhibit obvious redox peaks, and the energy level difference of the photo-Fenton system is higher than that of AC-NiFe2O4 NPs. This indicates that the transition rate of photogenerated electrons excited by the photo-Fenton system is faster than that of AC-NiFe2O4 NPs, which is more conducive to electron transfer.

[0053] Figure 3 The linear scanning curve in Figure (b) shows that the photocurrent density of the photo-Fenton system is higher than that of AC-NiFe2O4 NPs, indicating that in the photo-Fenton reaction system, photogenerated electrons can enter the system better and participate in the redox reactions related to the degradation of lignocellulose.

[0054] Figure 3 The band gap diagram in Figure (c) shows that the band gap of the photo-Fenton system is 2.15 eV, which is less than the 2.28 eV of AC-NiFe2O4 NPs. This indicates that the photo-Fenton system has a strong visible light absorption capacity, which is beneficial to the degradation of lignocellulose caused by subsequent photo-Fenton treatment.

[0055] Figure 3 Figure (d) shows that during photo-Fenton treatment of lignocellulose, the hydrogen peroxide content decreased sharply within 6 hours of reaction, indicating that the photo-Fenton reaction proceeded rapidly and consumed the hydrogen peroxide in the reaction system. From 6 to 12 hours, hydrogen peroxide continued to be consumed relatively quickly, followed by slower consumption and reaction. The superoxide anion content increased rapidly within 6 hours of reaction, and after 12 hours, its content fluctuated somewhat but remained at a high level. The hydroxyl radical content reached its peak at 12 hours of reaction, then decreased and remained at a relatively stable level. The changes in the content of superoxide anions and hydroxyl radicals indicate that the photo-Fenton system can promote the generation of superoxide radicals and hydroxyl radicals under the photogenerated electrons excited by visible light, thereby enhancing the oxidative decomposition of lignin. This is the mechanism by which the photo-Fenton reaction can effectively improve the lignin removal rate.

[0056] Example 4: Changes in the composition and structure of lignocellulose raw materials under preferred light-Fenton treatment conditions

[0057] After the reaction in Example 3 was completed, all the reactants were removed, filtered using a Buchner funnel, and centrifuged at 4000 r / min to achieve solid-liquid separation, obtaining the pretreated residue.

[0058] The composition, structure, and elemental composition changes were detected by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS).

[0059] XRD spectrum analysis results are as follows: Figure 4 As shown in Figure (a), 2θ at approximately 15.6° and 21.7° are diffraction peaks unique to cellulose, corresponding to the 101 and 002 crystal planes, respectively. Both the untreated sample and the photo-Fenton treated sample exhibit strong diffraction peaks at these two locations, indicating that photo-Fenton treatment did not cause significant changes in the crystalline structure of rice straw, suggesting that photo-Fenton is a relatively mild pretreatment method for lignocellulose.

[0060] FTIR spectrum as shown Figure 4 As shown in Figure (b), 3400 cm -1 The broad absorption peak at this point is related to the hydroxyl groups in cellulose and hemicellulose, as well as the phenolic hydroxyl groups in lignin. Compared with the untreated sample, the peak amplitude at this point is reduced in the photo-Fenton-treated sample, indicating that it interacts with hydrogen bonds during the separation process. 2940 cm⁻¹ -1 The CH bond at this position did not change significantly after photo-Fenton treatment, indicating that the basic chemical structure of cellulose was not destroyed. 1732 cm⁻¹ -1 The C=O bond on the acetyl group of hemicellulose shows a decrease in amplitude after photo-Fenton treatment, indicating that the hemicellulose has undergone some degree of hydrolysis. 1513cm ⁻1 The intensity of the C=C skeleton vibration peak of the lignin aromatic ring is weakened at 1368 cm⁻¹. ⁻1 and 1122 cm ⁻1 The deformation vibration peak of aromatic ring CH and 1262 cm ⁻1 The vibrational absorption peak intensities of CO2 in guaiac wood decreased, indicating that lignin underwent some degradation after photo-Fenton treatment, but some residues remained. (892 cm) -1 The vibration at this point is related to the CO bonds of glycosidic bonds and ring vibrations in cellulose. The peak at this point in the optically Fenton-treated sample showed almost no change, indicating that the crystalline structure of cellulose was well maintained. The optically Fenton-treated sample showed a peak at 792 cm⁻¹. -1 The peak of the lignin benzene ring structure was significantly reduced, indicating that the lignin structure was damaged and degraded to some extent. Correspondingly, the SEM images revealed that the microstructure of the photo-Fenton treated sample had changed significantly. Compared with the untreated sample, its surface showed more fragments and pores (indicated by white arrows), indicating that the microstructure of lignocellulose was destroyed.

[0061] Figure 5 XPS analysis results revealed changes in surface elements of the material before and after photo-Fenton treatment. Figure 5Figures (a) and (c) show the total XPS spectra of the materials before and after photo-Fenton treatment, respectively, indicating that the surface elements of both untreated and photo-Fenton treated materials are mainly C and O. After photo-Fenton treatment, the proportion of C=C bonds on the material surface decreased from 73.89% to 63.24%, while the proportions of C=O and O=CO bonds increased from 23.99% and 2.12% to 32.55% and 4.21%, respectively, as shown in Figures (b) and (d). This indicates that the carbohydrate composition of the material surface changed after photo-Fenton treatment. The decrease in the proportion of C=C bonds was mainly caused by the degradation of lignin, while the increase in the proportion of C=O bonds may be due to the better retention of cellulose.

[0062] Comparative Example 1

[0063] A pretreatment method for lignocellulose raw materials includes the following steps:

[0064] Rice straw was air-dried at room temperature, then chopped to approximately 2 cm in length using a shredder, and further pulverized using a high-speed grinder. The pulverized material was passed through 20 and 40 mesh sieves. Straw powder of 20-40 mesh size was added to a 150 mL Erlenmeyer flask at a rate of 5.00 g / flask. Hydrogen peroxide solution was added at a concentration of 2.5%, followed by deionized water to bring the final reaction volume to 50 mL. The flask was then sealed with a high-transmittance sealing film and placed 10 cm below an LED white light source (with a wavelength range of 450-700 nm) on a constant-temperature shaker to simulate natural visible light. The light intensity was adjusted to 5000 W / m² by adjusting the length of the LED white light strip. The reaction was carried out at 30℃ and 200 rpm for 36 h. After the reaction, all reactants were removed, filtered using a Buchner funnel, and centrifuged at 4000 r / min to achieve solid-liquid separation, obtaining the supernatant and residue.

[0065] Comparative Example 2

[0066] A pretreatment method for lignocellulose raw materials includes the following steps:

[0067] Rice straw was air-dried at room temperature, then chopped to approximately 2 cm in length using a shredder, and further pulverized using a high-speed grinder. The pulverized material was passed through 20 and 40 mesh sieves, and straw powder of 20-40 mesh size was taken and added to a 150 mL Erlenmeyer flask at a sample size of 5.00 g / flask. Activated carbon-doped nickel ferrite nanoparticles (AC-NiFe2O4 NPs) were added at a concentration of 4 g / L, followed by deionized water to bring the final reaction volume to 50 mL. The flask was then sealed with a high-transmittance sealing film and placed 10 cm under an LED white light source with a working wavelength range of 450-700 nm on a constant-temperature oscillator to simulate natural visible light. The light intensity was adjusted to 5000 W / m² by adjusting the length of the LED white light strip, and the reaction was carried out at 30℃ and 200 rpm for 36 h. After the reaction was completed, all the reactants were removed, filtered using a Buchner funnel, and centrifuged at 4000 r / min to achieve solid-liquid separation, obtaining the supernatant and residue.

[0068] Comparative Example 3

[0069] A pretreatment method for lignocellulose raw materials includes the following steps:

[0070] Rice straw was air-dried at room temperature, then chopped to approximately 2 cm in length using a shredder, and further pulverized using a high-speed grinder. The pulverized material was passed through 20 and 40 mesh sieves. Straw powder of 20-40 mesh size was added to a 150 mL Erlenmeyer flask at a rate of 5.00 g / flask. Hydrogen peroxide solution was added at a concentration of 2.5%, and activated carbon-doped nickel ferrite nanoparticles (AC-NiFe2O4 NPs) at a concentration of 4 g / L. Deionized water was then added to bring the final reaction volume to 50 mL. The flask was sealed with a high-transmittance sealing film and placed in a constant-temperature shaker under no-light conditions. The reaction was carried out at 30°C and 200 rpm for 36 hours. After the reaction, all reactants were removed, filtered using a Buchner funnel, and centrifuged at 4000 r / min to achieve solid-liquid separation, obtaining the supernatant and residue.

[0071] The residues obtained in Example 3 (LHA), Comparative Example 1 (LH), Comparative Example 2 (LA), and Comparative Example 3 (HA) were enzymatically hydrolyzed and saccharified using the method described in Example 2.

[0072] Comparative analysis of the cellulose retention rate, lignin removal rate, and enzymatic hydrolysis rate of four treatment systems (Example 3 (LHA), Comparative Example 1 (LH), Comparative Example 2 (LA), and Comparative Example 3 (HA)) is shown in the following results. Figure 6As shown, the cellulose retention rate, lignin removal rate, and enzymatic hydrolysis rate of the photo-Fenton treatment of lignocellulose (LHA) are all higher than those of the LH, LA, and HA reactions, indicating that the photo-Fenton system constructed in this invention can synergistically exert photocatalytic and Fenton reaction effects, thereby effectively promoting the degradation and enzymatic transformation of lignocellulose.

[0073] The above detailed description of a method for photo-Fenton treatment to enhance the degradation and conversion of lignocellulose, with reference to the embodiments, is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment, characterized in that, The method includes the following steps: (1) The crushed straw was mixed with hydrogen peroxide solution, activated carbon doped with nickel ferrite nanoparticles and deionized water to obtain a mixture; (2) The mixture is subjected to white light irradiation while being shaken, and then solid-liquid separation is performed to obtain supernatant and residue; (3) The residue is enzymatically hydrolyzed and saccharified.

2. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to claim 1, characterized in that, In step (1), the particle size of the straw is 20-40 mesh.

3. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to claim 1, characterized in that, In step (1), the mass concentration of hydrogen peroxide in the mixture is 1.0~3.5%; the concentration of activated carbon doped nickel ferrite nanoparticles is 2~6 g / L; and the concentration of straw is 0.1 g / mL.

4. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to claim 1, characterized in that, In step (2), the intensity of the white light is 3000~7000 W / m²; the irradiation time is 24~72 h.

5. The method for photo-Fenton treatment to enhance the degradation and conversion of lignocellulose according to any one of claims 1-4, characterized in that, In step (1), the mass concentration of hydrogen peroxide in the mixture is 2.5%; the concentration of activated carbon doped nickel ferrite nanoparticles is 4 g / L.

6. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to any one of claims 1-4, characterized in that, In step (2), the light intensity of the white light is 5000 W / m², and the irradiation time is 36 h.

7. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to any one of claims 1-4, characterized in that, In step (3), the enzymatic hydrolysis and saccharification method is as follows: disperse the residue in citrate buffer, add Cellic® CTec3 HS cellulase, and shake at 50°C for 72 h.

8. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to claim 7, characterized in that, The concentration of the citrate buffer is 0.05 M and the pH is 4.8; the mass concentration of the residue in the citrate buffer is 5%.

9. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to claim 7, characterized in that, The Cellic® CTec3 HS cellulase addition amount is 10 FPU / g residue.

10. The method for enhancing the degradation and conversion of lignocellulose through photo-Fenton treatment according to claim 7, characterized in that, The straw treated by the method retains more than 80% of cellulose, removes more than 20% of lignin, has a total phenol content of less than 15 mg / L, and has an enzyme hydrolysis rate of more than 60%.

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