A method for preparing pulp by dissociating straw fibers catalyzed by iron and manganese co-doped cerium oxide / carbon nanodots, the pulp and its application

Abstract

The present application discloses a method for preparing pulp by dissociating straw fibers catalyzed by iron-manganese oxide cerium / carbon nanodots, the pulp and its application; the pulping method includes: S1: obtaining straw bundles by splitting straw; S2: dispersing iron-manganese oxide cerium / carbon nanodots in ethanol, adding water, then spraying the surface of the straw bundles, impregnating and catalyzing the reaction for 24 to 48 h to obtain dissociated straw products, adding sodium hydroxide, steaming at 120 to 160 °C for 15 to 30 min, and then performing straw homogenization treatment to obtain fibrillated fiber pulp; this method can effectively weaken the rigid strength of straw fiber polymers, enhance the bond breaking and plasticity of the macromolecular chains of straw fibers, reduce the energy consumption of mechanical disk milling and homogenization dissociation pulping of straw fibers, has high environmental safety, and the obtained pulp can be applied to the preparation of straw products such as straw substrate blocks, straw mulch films, straw seedling containers, and straw trays.

Description

Technical Field

[0001] The present invention relates to the fields of straw dissociation, straw fiber pulping and straw fiber products, and in particular to a method for catalytic straw fiber dissociation pulping using iron-manganese oxide cerium / carbon nanodots and its application. Background Art

[0002] The pulping technology can be used to quickly pretreat lignocellulose to achieve the separation of plant tissues and fibers from each other. When pretreating straw, more importantly, in today's situation of scarce forest resources, using this technology can produce high-yield "straw substituting wood" pulp, and a series of special-shaped pulp molding products can be prepared, such as agricultural products, food, seedling raising, industrial packaging, etc. In particular, the development of green agricultural inputs has been a research trend in recent years, such as straw substrate blocks, biodegradable seedling raising devices, straw ecological bricks, agricultural mulch films and seedling raising substrate trays, etc. The key technology lies in how to use straw fibers to prepare low-energy-consuming and environmentally friendly plasticizable slurries.

[0003] The cell wall of straw fibers contains lignin-carbohydrate complexes (LCCs) with extremely stable structures, which are the main obstacles restricting the separation of lignin. Straw fiber dissociation pretreatment can effectively solve this technical problem. In traditional technical methods, acid pretreatment has low efficiency, high energy consumption and strong corrosiveness; in the process of alkali pretreatment of biomass with a high lignin content, intermediate products such as salts that have side effects on subsequent enzymatic hydrolysis and fermentation are produced, and the economic cost is high, making it difficult to be sustainably promoted; microbial pretreatment has the advantages of being green, environmentally friendly and mild in conditions, but the treatment cycle is relatively long.

[0004] Due to their unique properties, carbon dots (C-dots) have the advantages of small particle size, easy preparation and low cost. The abundant oxygen-containing functional groups on their surfaces, such as carbonyl, carboxyl, hydroxyl, etc., endow them with good water solubility and easy functionalization characteristics. Moreover, carbon dots have great potential in soil improvement, promoting plant growth and increasing yields. Carbon dots show peroxidase-like catalytic activity due to their small size effect and abundant active sites, but have little effect on the depolymerization of biomass fibers.

[0005] Adding metal catalysts can improve the dissociation degree of straw fibers, and thus improve the subsequent straw enzymatic pulping efficiency. Existing reports mostly use noble metals such as nickel, cobalt, ruthenium, rhodium, palladium, copper-based and their synthesized bimetallic catalysts, or couple elements such as iron and manganese to depolymerize straw fibers, and conduct research on the preparation of related products such as biomass renewable liquid fuels and chemicals. However, the raw materials for the related catalysts are not widely sourced, the synthesis process is complex, the cost is high, and the dosage is large.

[0006] Cerium oxide is a rare earth metal oxide that is non-toxic to the environment and is abundant in the natural environment. As a catalyst, cerium-based materials have a large specific surface area, and Ce 3+ and Ce4+ The oxidation states are easily convertible with each other, showing good oxygen storage performance and transfer function. The stability of its basic medium and the ability to disperse and stabilize oxide and metal particles. Small metal particles and metal clusters dispersed on CeO2 increase the active surface area of the catalyst, thus making the catalyst highly active and widely applicable to the degradation and oxidation of organic substances. The increase in oxygen-rich functional groups may also increase π-π stacking, reduce the bond energy of some C—O bonds in the remaining lignin part, weaken the intermolecular forces binding lignin together, and promote the overall dissociation of lignin macromolecules. Therefore, there is an urgent need to develop a carbon dot catalyst with high stability, easy preparation, low cost, and easy large-scale production. Iron-manganese cerium oxide / carbon nanodots can overcome the limitations of the existing technology, and there are few reports on their application in the preparation of special-shaped agricultural functional materials such as straw matrix blocks, straw mulch films, straw seedling containers, or straw fiber egg trays by catalytic fiber dissociation pulping. Summary of the Invention

[0007] The purpose of the present invention is to provide an iron-manganese cerium oxide / carbon nanodot (FeMn / CeO2@Cdots) catalytic straw fiber dissociation pulping method, pulp and its application. The iron-manganese cerium oxide / carbon nanodots can promote the dissociation of the three components of straw fibers, improve the fibrillation of straw fibers during the mechanical disc refining process, improve fiber softening and wettability, reduce energy consumption, and the obtained pulp can be used to prepare special-shaped agricultural functional materials such as straw matrix blocks, straw mulch films, straw seedling containers, and straw egg trays.

[0008] To achieve the above technical objectives, the present application first provides an iron-manganese cerium oxide / carbon nanodot catalytic straw fiber dissociation pulping method, and the specific steps are as follows:

[0009] S1: The straw is subjected to fiber separation treatment by a wire drawing machine to obtain a straw bundle; the shape of the straw bundle is rod-shaped or filamentous;

[0010] Preferably, the length dimension range of the straw bundle is distributed within the range of 5 - 120 mm, where the fiber length ≥ 50 mm, accounting for more than 55%;

[0011] S2: The iron-manganese cerium oxide / carbon nanodots are dissolved in ethanol with a concentration of 95%, after ultrasonic treatment for 5 min, added to a softening agent (water), stirred and then sprayed evenly on the surface of the straw bundle, and after impregnation treatment for 30 min, the moisture content of the regulated straw bundle is 60 - 65%, the pH is 6.0, and it is placed under the condition of 45 - 65 °C for catalytic reaction for 24 - 48 h to obtain a dissociated straw product;

[0012] Preferably, the mass-volume ratio of the iron-manganese cerium oxide / carbon nanodots to ethanol is 1:50 (g / mL).

[0013] The preparation method of the above-mentioned iron- and manganese-loaded cerium oxide / carbon nanodots is as follows: 1) At room temperature, cerium oxide is added to an Erlenmeyer flask containing an iron salt. After uniform stirring, a manganese salt is gradually added dropwise. The pH is adjusted to 9.0 - 9.5 with ammonia water, and the reaction is carried out at 85 °C for 60 min. After centrifugation and filtration, it is dried to obtain iron- and manganese-loaded cerium oxide for standby; 2) Choline chloride and a hydrogen bond donor are mixed according to a molar mass ratio of 1:2 to obtain a deep eutectic solvent for standby; 3) The iron- and manganese-loaded cerium oxide obtained in step 1), the deep eutectic solvent obtained in step 2), and protein waste are mixed and ground, and then calcined in an oxygen-free condition at 450 °C for 2 h to obtain iron- and manganese-loaded cerium oxide / carbon nanodots. In the above steps, the molar mass ratio of the added cerium oxide, iron salt, and manganese salt is 1:(0.1 - 0.5):(0.1 - 0.5) in sequence. The above iron salts include at least one of ferrous chloride, ferric chloride, and ferric sulfate; the manganese salts include at least one of manganese chloride and manganese sulfate; the above hydrogen bond donors include at least one of urea and thiourea. In step 3) above, the mass ratio of the added iron- and manganese-loaded cerium oxide, deep eutectic solvent, and protein waste is 1:(1 - 3):(1 - 5).

[0014] The term "carbon nanodots", Carbon dots (CDs), also known as "nanocarbon dots", have a large number of hydrophilic functional groups on their surface, and are characterized by high water solubility, easy modification, good biocompatibility, and low cytotoxicity.

[0015] The above protein waste can be a plant protein source, an animal protein source, or any ratio of the two protein wastes. The plant protein source can be one or more of soybean cake, rapeseed cake, cottonseed cake, peanut meal, sesame cake, camellia cake, sunflower seed cake, flaxseed cake, and safflower seed meal; the animal protein source can be one or more of black soldier fly shells, mussel shells, scallop shells, shrimp shells, crab shells, feathers, etc. Using protein waste as a carbon source can not only improve the catalytic dissociation effect on straw fibers, but also provide nitrogen, sulfur and other nutrients for agricultural straw-based products, promoting crop growth.

[0016] S3: Add sodium hydroxide to the dissociated straw product. After uniform mixing, the material is steamed at 120 - 160 °C for 15 - 30 min, and then a high-concentration disc refiner is used to homogenize the steamed material to achieve mechanical delamination and dissociation, obtaining fibrillated fiber pulp.

[0017] Preferably, in the method for catalytic dissociation pulping of straw fibers with the above-mentioned iron- and manganese-loaded cerium oxide / carbon nanodots, in step S2, the addition amount of iron- and manganese-loaded cerium oxide / carbon nanodots is 0.1 - 1.0% of the mass of the straw bundle.

[0018] Preferably, in the above-mentioned iron-manganese-loaded cerium oxide / carbon nanodots catalyzed straw fiber dissociation pulping method, the straw used in step S1 is preferably 10-30 cm long and has a moisture content of 10-15%; the straw includes at least one of rice straw, corn straw, cotton stalks, wheat straw, bamboo stalks, hemp stalks, and bagasse.

[0019] Preferably, in the above-mentioned iron-manganese-loaded cerium oxide / carbon nanodot catalytic straw fiber dissociation pulping method, in the straw bundle obtained in step S1, the fiber bundles with a fiber aspect ratio ≥50 account for more than 45% of the total mass of the straw bundle, which can not only increase the attachment surface area of the catalytic material, but also facilitate the subsequent fiber interweaving reinforcement effect.

[0020] Preferably, in the above step S3, the amount of sodium hydroxide added is 1-5% of the dry matter amount of the straw bundle, and more preferably, the amount of sodium hydroxide added is 1-2% of the dry matter amount of the straw bundle.

[0021] Preferably, in the above step S3, the high-concentration disc grinding equipment used can be a disc grinder or a pulping machine (such as the equipment and method disclosed in Chinese Patent ZL202110584251.9), and the solid content of the obtained fibrillated fiber slurry is preferably 25-30%. The fiber slurry has a low moisture content, and basically no wastewater is generated during the process, and the production process is clean and environmentally friendly.

[0022] Secondly, the present application provides a slurry prepared by the above method.

[0023] Third, the present application also provides the use of the pulp obtained by the pulping method in the preparation of special-shaped materials such as straw matrix blocks, straw mulch films, straw seedling containers or straw fiber trays. The straw fiber filament brooming disc grinding pulp catalyzed by iron-manganese-loaded cerium oxide / carbon nanodots has a high plasticizing torque and balance torque, which is conducive to the molding and processing of the straw fiber pulp and improves the interlacing strength of the straw fiber interface; after different times of mechanical decomposition and dissociation treatment of the straw fiber, the crop fiber pulp can be used to prepare these special-shaped materials according to the scale and morphological characteristics of the filament fibers.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) A low eutectic solvent synthesized from choline chloride and urea or thiourea and protein waste are used as the raw material sources of carbon nanodots. The heteroatom (nitrogen) doped biochar has well-developed pores and a large specific surface area. The surface contains a large number of oxygen-containing functional groups, and the N dopant is effectively embedded in the carbon lattice through the activation-Maillard reaction, changing its charge and persistent free radicals (R·), effectively improving the conversion of the target substance. At the same time, nitrogen and sulfur doping not only promote the formation of micropores in the carbon, but also introduce weak acid and medium acid sites, which can reduce the pH of the catalytic straw fiber dissociation system, and further promote the ability of iron-manganese oxide to catalyze the depolymerization of straw fibers under acidic conditions.

[0026] 2) The loading of iron-manganese bimetallic oxide can stabilize the dispersion of cerium oxide, further improve the mixed valence state of cerium and the migration of lattice oxygen, and enhance the synergistic catalytic dissociation effect by forming structural defects such as oxygen ion vacancies and chemical defects, as well as free radical species.

[0027] 3) The introduction of iron-manganese cerium oxide / carbon nanodots can effectively weaken the rigid strength of the straw fiber polymer, enhance the bond breaking and plasticity of the macromolecular chains of the straw fiber, and reduce the energy consumption of mechanical disk milling and homogenization for straw fiber dissociation pulping. In addition, carbon nanodots are a new type of nanomaterial that can regulate plant growth and development. Moreover, the addition amount of iron-manganese cerium oxide / carbon nanodots in this invention is small, the synthesis cost is low, and the environmental safety is high. The elements contained are also components of various enzymes in the crop body, and can effectively enhance the physiological and biochemical effects of crop growth and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention.

[0029] Figure 1 Schematic diagram of the technical route for the preparation of iron-manganese cerium oxide / carbon nanodots and the catalytic dissociation pulping of straw fibers.

[0030] Figure 2 Comparison results of the energy consumption of the fibrillated fiber pulp after disk milling with different amounts of iron-manganese cerium oxide / carbon nanodots added.

[0031] Figure 3 X-ray diffraction patterns (XRD) of cerium oxide, iron-manganese cerium oxide, iron-manganese cerium oxide / carbon nanodots, and carbon nanodots for Example 1.

[0032] Figure 4 Scanning electron microscope images and scanning energy spectrum diagrams of iron-manganese cerium oxide / carbon nanodots and other materials for Example 1: Among them, a) scanning electron microscope of cerium oxide; b) scanning electron microscope of iron-manganese cerium oxide; c) scanning electron microscope of iron-manganese cerium oxide / carbon nanodots; d) energy spectrum scanning of iron-manganese cerium oxide / carbon nanodots; e) manganese element distribution in the energy spectrum scanning of iron-manganese cerium oxide / carbon nanodots; f) iron element distribution in the energy spectrum scanning of iron-manganese cerium oxide / carbon nanodots. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1 Preparation of nitrogen-doped iron-manganese cerium oxide / carbon nanodots

[0035] Dissolve 1.62 g of anhydrous ferric chloride in 100 ml of aqueous solution and place it in a three-necked flask. Add 17.2 g of nano-ceria (Shanghai Macklin Biochemical Co., Ltd., size distribution 20 - 50 nm, spherical, content 99.5%) into the ferric chloride solution. After stirring evenly, gradually add 50 ml of a solution containing 7.55 g of manganese sulfate. Adjust the pH to 9.0 - 9.5 with ammonia water (Shanghai Macklin Biochemical Co., Ltd., purity: 25 - 28%, evaporation residue ≤ 0.004%). React at 85 °C for 60 min and centrifuge (rotation speed 5000 rpm) for 5 min; take the precipitate obtained after centrifugation and dry it (98 °C, 24 h) to obtain iron-manganese cerium oxide for standby.

[0036] Mix 69.5 g of choline chloride and 60 g of urea (in the specific implementation process, it can also be thiourea or any ratio of urea and thiourea) evenly at 80 °C to obtain a deep eutectic solvent (DES). Then take 10 g of the iron-manganese cerium oxide obtained in step S1, 10 g of the deep eutectic solvent, and 50 g of soybean meal powder and grind them evenly in a mortar. Place them in a tube furnace (RTL1200, Nanjing Boyuntong Instrument Technology Co., Ltd.) and calcine at 450 °C under anaerobic conditions for 2 h.

[0037] After the calcination is completed, the material is cooled to room temperature with the furnace, and then ultrasonic cleaning is carried out 3 times alternately with deionized water and absolute ethanol, 5 min each time (KQ-500GVDV type ultrasonic cleaner, ultrasonic power 500 w, Kunshan Ultrasonic Instrument Co., Ltd.), centrifuge (rotation speed 5000 rpm, time 5 min), and take the precipitate to obtain nitrogen-doped iron-manganese cerium oxide / carbon nanodots.

[0038] In the specific implementation process, the molar mass ratio of ceria, iron salt, and manganese salt is in the range of 1:(0.1 - 0.5):(0.1 - 0.5); the iron salt is ferrous chloride, ferric chloride, or ferric sulfate or any ratio of the three; the manganese salt is manganese chloride or manganese sulfate or any ratio of the two; the mass ratio of the added iron-manganese cerium oxide, deep eutectic solvent, and protein waste is in the range of 1:(1 - 3):(1 - 5), and the purpose of the invention can be achieved.

[0039] In addition, after grinding 10 g of the deep eutectic solvent and 50 g of soybean meal powder evenly in a mortar, they are also placed in a tube furnace (RTL1200, Nanjing Boyuntong Instrument Technology Co., Ltd.) and calcined at 450 °C under anaerobic conditions for 2 h to prepare carbon nanodots.

[0040] Example 2

[0041] S1: Feed 10 kg of rice straw with a length range of 10 - 30 cm and a moisture content of 12 - 14% into a wire drawing machine for wire drawing to obtain straw bundles (see Figure 1 S1 in it), which are rod-shaped or filamentous. The length dimension range of the wire-drawn straw bundles is distributed between 5 and 120 mm, among which the straw bundles with a fiber length ≥ 50 mm account for about 55%, and the fiber bundles with a fiber length-width ratio ≥ 50 account for more than 45% of the total mass of the straw bundles.

[0042] The wire drawing machine used in this embodiment is purchased from Zhengzhou Jifeng Machinery Manufacturing Co., Ltd. (9RS-4). The double-sided serrated fixed knife has a size of 60 × 150 mm, 3 pieces / group, and a total of 3 groups of 9 pieces. The hammer piece has a size of 60 × 160 mm, 6 - 9 pieces / group, and a total of 4 groups. The rotational speed of the wire drawing wheel is 2000 - 5000 rpm (the rotational speed in this embodiment is 4000 rpm), and the productivity is 1.5 - 1.8 t / h.

[0043] The wire drawing step is a conventional method in the art, as disclosed in the literature "Analysis of the Coupled Movement Characteristics of Materials and Airflow in a Multifunctional Forage Wire Drawing Machine", Transactions of the Chinese Society for Agricultural Machinery, 2023.

[0044] S2: Dissolve 0.2 g, 1 g, and 2 g of iron-manganese-oxide-cerium / carbon nanodots obtained in Example 1 into 10 ml of ethanol with a concentration of 95% respectively. After ultrasonic dispersion treatment for 5 minutes, pour them into 300 g of water, stir, and then spray them onto the surface of 200 g of straw bundles respectively. After uniform mixing, perform impregnation treatment for 30 minutes (as shown in Figure 1 S2). Adjust the moisture content of the straw bundles to 60 - 65% and the pH to 6.0, and then place them under the condition of 45 - 65 °C for catalytic reaction for 24 h to obtain dissociated straw products.

[0045] S3: Add 4 g of sodium hydroxide to the dissociated straw products obtained in step S2, mix them evenly, and then place them in a steam boiler for steam steaming for 30 minutes. After cooling to room temperature, use a high-concentration disc refiner (BX-300-2, Beijing Chunhui Xinji Paper Machinery Factory, the diameter of the grinding disc is Φ300 mm, the rotational speed of the main shaft is 0 - 3000 r / min, and the rotational speed of the feeding screw is 30 - 500 r / min) to perform straw fiber homogenization treatment on the steamed material to achieve mechanical disintegration and dissociation to achieve homogenization, and obtain wire-drawn and broom-like fiber slurries A, B, and C respectively.

[0046] In this step, the straw fiber homogenization treatment has achieved mechanical disintegration and dissociation. The specific process is disclosed in the literature "Characterization of the Structure and Properties of Rice Straw Pretreated with Choline Chloride / Urea and Its Dissociated Fibers", Chemistry and Industry of Forest Products, 2023, 43(04).

[0047] In a specific implementation, the catalytic reaction time can be 24 to 48 hours; the straw used can be rice straw, corn straw, cotton straw, wheat straw, bamboo poles, hemp poles, etc.

[0048] The schematic diagram of the preparation of iron-manganese cerium oxide / carbon nanodots and the technical route for catalytic dissociation of straw fibers into pulp involved in the above examples can be seen in Figure 1 .

[0049] Example 3

[0050] To detect the effect of iron-manganese cerium oxide / carbon nanodots on the energy consumption of straw fiber dissociation into pulp, a control group was prepared according to the following steps at the same time.

[0051] 1) 10 kg of straw was shredded by a silk rolling machine (Zhengzhou Jifeng Machinery Manufacturing Co., Ltd., model: 9RS-4) to obtain rod-shaped or filamentous straw bundles (parameters are the same as those in step S1 of Example 2).

[0052] 2) The moisture content of the straw bundles was adjusted to 60 - 65%, 4 g of sodium hydroxide was directly added, and after uniform mixing, it was steamed in a steam boiler for 30 minutes. After cooling to room temperature, a high-concentration disc refiner (BX-300-2, Beijing Chunhui Xinji Paper Machinery Factory) was used to homogenize the steamed material to achieve mechanical defibration and dissociation, obtaining the defibrated fiber pulp control group CK.

[0053] Figure 2 Table 1 shows the detection results of the disc refiner energy consumption of the defibrated fiber pulp obtained in Example 2 and Example 3.

[0054] It can be seen that the disc refiner energy consumption of the defibrated fiber pulp obtained in Example 2 is much lower than that of the control group. Compared with the CK prepared in Example 3, the energy consumption of groups A, B, and C prepared in Example 2 is reduced by 25.16%, 48.91%, and 41.06% respectively. This is mainly because the introduction of iron-manganese cerium oxide / carbon nanodots can catalyze the depolymerization of lignin in straw fibers, reduce the chemical composition in the fiber cell wall region, break the molecular chain, and reduce the intermolecular chain segment force, thereby reducing the defibration of fiber bundles in the material disc refiner stage and further reducing the energy consumption.

[0055] Taking the defibrated fiber pulps A, B, and C obtained in Example 2 and the control group CK obtained in Example 3 as pulping materials, a torque rheometer was used to monitor their plasticity (rheological properties). The measurement method was carried out with reference to the disclosure of Chinese Patent ZL201410569478.6, and the obtained results are shown in Table 1.

[0056] As can be seen from Table 1, compared with the control group CK, the retting and fibrillation disc mill pulp of straw fiber catalyzed by iron-manganese oxide cerium / carbon nanodots has higher plasticizing torque and balance torque. Among them, the plasticizing torque of treatment group B increased by 45.44%, and the balance torque increased by 2.59 times, indicating that the plasticity (rheological properties) of the retting and fibrillation fiber pulp obtained by catalytic treatment of straw fiber with iron-manganese oxide cerium / carbon nanodots has been improved, which is conducive to the interfacial bonding between fibers in straw products and thus improves the mechanical strength of the products.

[0057] Table 1 Effects of Iron-Manganese Oxide Cerium / Carbon Nanodots on the Plasticity (Rheological Properties) of Straw Fiber Pulping by Dissociation

[0058] Slurry Time / s Plasticizing Torque / (N·m) Balanced Torque / (N·m) A 65 7.51 0.95 B 88 9.25 1.22 C 74 8.67 1.06 CK 49 6.36 0.34

[0059] Furthermore, the retting and fibrillation fiber pulp prepared by mechanically defibrating and dissociating straw fiber 4 times with a high-concentration disc mill (as shown in the schematic diagram of S3) was used to prepare straw mulch film according to the method disclosed in Chinese Patent ZL201911111681.8 (A Preparation Method and Application of a High-Toughness Straw Fiber-Based Weed Suppressant Mulch Film), and the tensile strength, bursting strength and tearing strength of the straw mulch film were measured according to GB / T 12914-2018, GB / T1539-2007 and GB / T 455-2002 respectively. The effects of this technical scheme on the mechanical properties of the straw film were studied and compared. The basis weight selected in this example was 75 g / m Figure 1 2. 2 .

[0060] Table 2 Comparison of the Mechanical Properties of Straw Mulch Films Made from Retting and Fibrillation Fiber Pulps Prepared by Different Treatments

[0061]

[0062] The comparison found that the tensile indexes of the film of treatment groups A, B and C prepared in Example 2 were increased by 34.70%, 69.91% and 42.31% respectively compared with the CK1 group; the bursting indexes were increased by 14.20%, 16.57% and 25.74% respectively compared with the CK1 group; the tearing indexes were increased by 14.20%, 22.49% and 18.64% respectively compared with the CK group. In addition, compared with the film material CK1 prepared by the publicly disclosed patent ZL201911111681.8, the overall mechanical indexes of the film of treatment groups A, B and C prepared in Example 2 were higher.

[0063] As can be seen from the experimental results in Table 2, the introduction of iron- and manganese-loaded cerium oxide / carbon dots can effectively improve the mechanical strength of the straw fiber membrane. Different addition amounts have slightly different effects on the tensile index, burst index, and tear index of the straw fiber membrane, but generally show an increasing trend. In particular, the improvement of the tensile index of the membrane is relatively significant, indicating that the interfacial interweaving force of the fibers can be effectively enhanced after the mechanical disk milling treatment of straw fibers catalyzed by iron- and manganese-loaded cerium oxide / carbon dots, which is beneficial for the preparation of other functional agricultural materials.

[0064] Example 4

[0065] The fibrillated fiber slurry prepared by subjecting the straw fibers to mechanical defibration and dissociation treatment twice using a high-concentration disk mill in Example 2 was used to prepare straw substrate blocks using A, B, and C respectively according to the production method of the patent "ZL 201910978528.9 A preparation method and application of a full-nutrient degradable straw seedling-raising substrate block". The rice seedling quality indicators (Table 3) were compared with the straw substrate blocks prepared by this patent (as the control group CK2).

[0066] Rice seed variety: Nanjing 46, seeding rate: 120 g / tray, seedling-raising time: 20 d. At the end of the seedling-raising period, the emergence number, plant height, stem diameter, and chlorophyll of the rice seedlings grown under all treatments were tracked and measured. The detection method was carried out with reference to the literature "Du Yihan, et al. Effects of sowing on rice seedling quality, transplanting quality, and yield using printed straw substrate trays. China Rice, 2023, 29(2): 81-84."; The determination of root activity was carried out with reference to the literature "Chu Yutan, et al. Effects of exogenous melatonin on the growth and antioxidant system of rice seedlings under antimony stress, 2023, 44(04): 2356-2364."

[0067] Table 3 Basic biological trait indicators of rice seedlings grown in straw substrate blocks of different treatment groups

[0068]

[0069] As can be seen from Table 3, compared with the control group CK2, the emergence number, stem diameter, root activity, and relative chlorophyll content of the basic biological traits of the rice seedlings grown in the straw substrate blocks prepared by different treatment groups A, B, and C were all significantly improved. The plant height of the C treatment group was slightly higher than that of other treatments. It was analyzed that the higher urea content in the raw materials prepared by the introduced catalyst led to a higher nitrogen doping amount in the iron- and manganese-loaded cerium oxide / carbon dots formed.

[0070] Figure 3XRD patterns of cerium oxide, iron- and manganese-loaded cerium oxide, iron- and manganese-loaded cerium oxide / carbon dots, and carbon dots involved in Example 1. It can be seen from the XRD patterns that after the surface of cerium oxide is loaded with iron and manganese elements, the crystal structure of CeO2 is still preserved, but its XRD shows characteristic diffraction peaks at 35.85°, 44.21°, and 64.56° attributed to manganese oxides, indicating that manganese is successfully loaded on the surface. The characteristic diffraction peaks of iron are not obvious. It is analyzed that this may be because the iron content is low, and the characteristic peaks of the cerium oxide crystal structure strongly mask the relevant diffraction peaks of iron. For the iron- and manganese-loaded cerium oxide / carbon dots, it can be seen that the characteristic diffraction peak of carbon dots is at 26.38°, and the characteristic diffraction peaks of manganese and cerium oxide are significant, indicating that the synthesized iron- and manganese-loaded cerium oxide / carbon dots have the characteristics of relevant elements.

[0071] In addition, combined with scanning electron microscopy ( Figure 4 ), it is found that iron and manganese elements are evenly distributed on the surface of the iron- and manganese-loaded cerium oxide / carbon dots. It can be seen from the normalized mass data of the energy spectrum (Table 4) that cerium is the main element in all materials. Among them, the proportions of iron and manganese in the iron- and manganese-loaded cerium oxide material reach 2.96% and 14.37% respectively. In the iron- and manganese-loaded cerium oxide / carbon dots, the proportions of carbon, iron, and manganese reach 13.80%, 3.34%, and 11.57% respectively. The above test results prove the successful loading of iron and manganese. This analysis provides a theoretical support for the improvement of the catalytic effect of the iron- and manganese-loaded cerium oxide / carbon dots on the dissociation of straw fiber pulping.

[0072] Table 4 Normalized mass of energy spectrum

[0073]

[0074] At the same time, through Example 2 and Example 3, the fibrillation fiber pulp prepared by mechanically defibrating and dissociating the straw fiber 3 times with a high-concentration disc refiner equipment is used to prepare a straw egg tray according to "Paper Molded Egg Tray, Standard No. BB / T 0015-2021, Issuing Unit: Ministry of Industry and Information Technology of the People's Republic of China, Implementation Date: July 1, 2021". Referring to "Paper Molded Egg Tray, GB 10443-89", its compression deformation is 2.05 mm (lower than the limit requirement of BBT0015-2021, ≤3), and the moisture content is 8.3% (lower than the limit requirement of BBT0015-2021, ≤14). After being filled with water for 0.5 h, there is no leakage, and it has good waterproof performance. The single-item judgment meets the relevant requirements, and the mechanical properties are basically equivalent to those of the commercially available traditional paper pulp egg tray. It shows that by using this example, the straw fiber egg tray (tray) produced with straw as the raw material can replace the traditional paper pulp egg tray, and it is environmentally friendly, degradable, convenient, practical and low-cost. It can effectively protect eggs from breaking and is suitable for long-distance transportation. It not only solves the high-value utilization path of agricultural waste straw, but also solves the dependence on imported pulp in China.

[0075] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

Claims

1. A method for preparing pulp by dissociating straw fibers with iron and manganese oxide cerium / carbon nanodots as a catalyst, characterized in that, The specific steps are as follows: S1: The straw is subjected to wire splitting treatment by a wire splitting machine to obtain a straw bundle, which is reserved; The length of the straw bundle is 5 - 120 mm, and the proportion of fibers with a fiber length ≥ 50 mm is more than 55%; S2: The iron-manganese oxide cerium / carbon nanodots are dispersed in ethanol, water is added, and then it is sprayed onto the surface of the straw bundle obtained in step S1, impregnated and the moisture content of the straw bundle is adjusted to 60 - 65%, the pH is 6.0, and a catalytic reaction is carried out at 45 - 65 °C for 24 - 48 h to obtain a dissociated straw product; The preparation method of the iron-manganese oxide cerium / carbon nanodots is as follows: 1) Cerium oxide and an iron salt are mixed evenly, a manganese salt is added drop by drop, the pH is adjusted to 9.0 - 9.5, and a reaction is carried out at 85 °C for 60 min. After centrifugation, filtration and drying, iron-manganese oxide cerium is obtained and reserved; 2) Choline chloride and a hydrogen bond donor are mixed in a molar ratio of 1:2 to obtain a deep eutectic solvent, which is reserved; 3) The iron-manganese oxide cerium obtained in step 1), the deep eutectic solvent obtained in step 2) and protein waste are mixed and ground, and calcined at 450 °C under anaerobic conditions for 2 h to obtain the iron-manganese oxide cerium / carbon nanodots; In the above steps, the molar ratio of the added cerium oxide, iron salt and manganese salt is 1:(0.1 - 0.5):(0.1 - 0.5), and the mass ratio of iron-manganese oxide cerium, deep eutectic solvent and protein waste is 1:(1 - 3):(1 - 5); The hydrogen bond donor includes at least one of urea and thiourea; S3: Sodium hydroxide is added to the dissociated straw product obtained in step S2, and after being evenly mixed, it is steamed at 120 - 160 °C for 15 - 30 min, and the steamed material is subjected to straw homogenization treatment to obtain a wire splitting and brooming fiber pulp.

2. The method for preparing pulp by catalytic dissociation of iron-loaded manganese oxide cerium / carbon nanodots from straw fibers according to claim 1, wherein In step S1, the length of the straw is 10 - 30 cm, and the moisture content is 10 - 15%; The straw includes at least one of rice straw, corn straw, cotton stalk, wheat straw, bamboo pole, hemp pole, and bagasse.

3. The method for preparing pulp by catalytic dissociation of iron and manganese oxide cerium / carbon nanodots carried straw fiber according to claim 1, wherein In the straw bundle obtained in step S1, the fiber bundles with a fiber length-width ratio ≥ 50 account for more than 45% of the total mass of the straw bundle.

4. The method for preparing pulp by dissociating straw fibers with iron-loaded manganese oxide cerium / carbon nanodots as a catalyst according to claim 1, wherein In step S2, the addition amount of iron-manganese oxide cerium / carbon nanodots is 0.1 - 1.0% of the mass of the straw bundle.

5. The method for preparing pulp by catalytic dissociation of iron-loaded manganese oxide cerium / carbon nanodots from straw fibers according to claim 1, wherein, In step S2, the mass-volume ratio of iron-manganese oxide cerium / carbon nanodots to ethanol is 1:50, and the unit of the mass-volume ratio is g / mL.

6. The method for preparing pulp by catalytic dissociation of iron- and manganese-loaded cerium oxide / carbon nanodots from straw fibers according to claim 1, wherein In step S3, the addition amount of sodium hydroxide is 1 - 5% of the dry matter mass of the straw bundle.

7. The method for preparing pulp by catalytic dissociation of iron and manganese oxide cerium / carbon nanodots carried straw fiber according to claim 1, wherein, In step S2, the iron salt includes at least one of ferrous chloride, ferric chloride, and ferric sulfate; The manganese salt includes at least one of manganese chloride and manganese sulfate.

8. The method for preparing pulps by catalytic dissociation of iron-loaded manganese oxide cerium / carbon nanodots from straw fibers according to claim 1, wherein, In step S2, the protein waste includes at least one of a plant protein source or an animal protein source; The plant protein source includes one or more of soybean cake, rapeseed cake, cottonseed cake, peanut meal, sesame cake, camellia cake, sunflower seed cake, flaxseed cake, and safflower seed meal: The animal protein source includes one or more of black soldier fly shells, mussel shells, scallop shells, shrimp shells, crab shells, and feathers.

9. The pulp prepared by the pulping method according to any one of claims 1 - 8.

10. Use of the pulp obtained by any of the pulping methods according to claims 1-8 in the preparation of straw substrate blocks, straw mulch films, straw seedling containers, and straw trays.

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