Preparation method of waste paper fiber-based biochar and product thereof

Abstract

The invention provides a waste paper fiber-based biochar preparation method and a product thereof, and belongs to the field of carbon material preparation.The method comprises the steps that waste paper fibers serve as raw materials, a deep eutectic solvent (DES) composed of choline chloride and phosphoric acid serves as a reaction medium, and the waste paper fibers are carbonized at the low temperature to obtain the waste paper fiber-based biochar. The cellulose structure is effectively destroyed and the carbonization process is promoted; the waste paper fiber-based biochar which is large in specific surface area, rich in pore structure and good in surface functional group activity is prepared, and DES can be recycled and used for preparing new biochar. The method has the advantages that the raw materials are easy to obtain, green and environment-friendly, the operation is simple and convenient, the specific surface area of the charcoal material is large, the pore structure is rich, the preparation cost is low and the like, and the prepared charcoal material has a good application prospect in the fields of wastewater treatment and the like.

Description

Technical field

[0001] The present invention belongs to the field of carbon material preparation, and relates to a preparation method of waste paper fiber-based biochar and a product thereof. [Background Technology]

[0002] Hundreds of millions of tons of waste paper are generated annually worldwide. As a biomass raw material, it has long been primarily used in the papermaking industry. However, after repeated recycling, waste paper's quality gradually deteriorates, making it difficult to produce high-quality paper and board, and can only be used to produce mid- to low-grade paper and board. Therefore, finding the efficient recycling of waste paper fibers is an urgent challenge.

[0003] Biochar is a porous carbon material prepared by pyrolysis or carbonization of biomass, which has the characteristics of large specific surface area, rich pore structure and surface functional groups. Using waste paper fiber as the raw material of biochar can not only promote the recycling of waste resources, but also reduce the cost of raw materials. Traditional biochar preparation methods such as pyrolysis, carbonization or hydrothermal carbonization often have problems such as high energy consumption, low carbon yield, and difficult to control pore structure, which limits the further improvement of its performance and its application in high value-added fields. In recent years, deep eutectic solvents (DES) as a new type of green solvent have received increasing attention due to their advantages such as simple preparation, low raw material cost, recyclability and biodegradability. DES can be used as a reaction medium to participate in the pretreatment or carbonization process of biomass, which can effectively promote the depolymerization and activation of biomass structure, thereby improving the specific surface area, porosity and the types and quantities of surface functional groups of the obtained biochar.

[0004] Chinese patent publication number CN116396769A, "A Waste Paper-Based Biochar, Its Preparation Method, and Application," uses waste paper as raw material and carbonizes it in a high-temperature tubular furnace at 650-850°C. Chinese patent publication number CN106865524B, "A Method for Preparing Sulfur-Containing Carbon Microspheres from Waste Paper Fiber," uses deinked waste paper fibers as raw material. The process is pretreated in a hydrothermal reactor with concentrated sulfuric acid and then carbonized at a gradually increasing temperature, with a pretreatment temperature of 210-260°C and a maximum carbonization temperature of 900°C. Chinese patent publication number CN109437192A, "A Method for Producing Activated Carbon from Waste Paper," also uses carbonization in a high-temperature furnace at 600-700°C. Although previous studies have attempted to use DES directly as a carbonization reaction medium for biochar production, the performance of the resulting biochar remains poor. The paper "Deep eutectic solvent-mediated preparation of solvothermal carbon with rich carboxyl and phenol groups from crop straw for high-efficient uranium adsorption" uses cotton straw as raw material and choline chloride / citric acid as DES system to prepare biochar. The highest specific surface area of the obtained biochar is only 16.55m 2 / g. The paper "Production of biochar from lignocellulosic biomass with acidic deep eutectic solvent and its application as efficient adsorbent for Cr(VI)" uses wood and cotton stalks as raw materials, and uses p-toluenesulfonic acid and choline chloride as the DES system to prepare biochar. The obtained biochar has a maximum specific surface area of 7.1m 2 In terms of resource utilization of waste paper fiber as raw material, the existing technology still lacks a biochar preparation method that is low-cost, environmentally friendly and high-performance. [Summary of the invention]

[0005] The technical problem to be solved by the present invention is to provide a method for preparing waste paper fiber-based biochar and its products. The method can carbonize waste paper fibers at a relatively low temperature to prepare waste paper fiber-based biochar with a large specific surface area, a developed pore structure, rich surface functional groups, good activity and high adsorption.

[0006] The present invention is achieved in that:

[0007] A method for preparing waste paper fiber-based biochar, the method comprising the following steps:

[0008] Step 1, preparation of deep eutectic solvent DES: heating and stirring choline chloride and phosphoric acid, mixing them evenly, and forming a colorless transparent liquid at room temperature;

[0009] Step 2: Preparation of biochar from waste paper fibers:

[0010] (1) Put waste paper fibers into a grinder and grind them into 100-200 meshes;

[0011] (2) Add waste paper fiber and DES into the reactor, mix them evenly, heat them, and keep them warm for reaction. After the reaction is completed, wash them thoroughly with deionized water and ethanol, and then dry them to obtain biochar.

[0012] Furthermore, in step 1, the preparation conditions of the deep eutectic solvent are as follows: choline chloride and phosphoric acid are uniformly mixed in a molar ratio of 1:2, stirred at 80° C. and a rotation speed of 300 rpm until completely dissolved, and a colorless transparent liquid is obtained at room temperature.

[0013] Furthermore, in step 2, the waste paper fibers include deinked waste paper fibers and non-deinked waste paper fibers.

[0014] Furthermore, in step 2, the solid-liquid ratio of the waste paper fiber raw material to DES is 1:10-1:14, the reaction temperature is 150-210° C., and the reaction time is 3-9 hours.

[0015] Furthermore, in step 2, the drying temperature is 50-100° C., and the drying time is 4-8 hours.

[0016] Furthermore, a waste paper fiber-based biochar prepared according to the waste paper fiber-based biochar preparation method.

[0017] The method of the present invention has the following advantages:

[0018] The present invention is a new method for preparing biochar using waste paper fiber as raw material and a low eutectic solvent as a carbonization medium. The method uses waste paper fiber as raw material and adopts a low eutectic solvent (DES) composed of choline chloride and phosphoric acid as the reaction medium to carbonize the waste paper fiber at a relatively low temperature, effectively destroying the cellulose structure and promoting its carbonization process.

[0019] The present invention not only prepares waste paper fiber-based biochar with large specific surface area, developed pore structure, rich surface functional groups and good activity, but also can recycle and reuse DES to prepare new biochar.

[0020] In summary, the present invention has the advantages of easy raw material availability, green and environmental protection, simple operation, low reaction temperature, and the prepared carbon material has a large specific surface area, rich pore structure, and high adsorption. The prepared biochar material has good application prospects in wastewater treatment and other fields.

Brief Description of the Drawings

[0021] The present invention will be further described below with reference to the drawings and embodiments.

[0022] Figure 1 This is a scanning electron microscope image of the waste paper fiber-based biochar obtained in Example 1 of the present invention. [Specific implementation method]

[0023] The following will be combined with the Figure 1 The technical solutions of the present invention are clearly and completely described in the following and in detail. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention. If specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0024] 1. Experimental process and detection method

[0025] 1. Experimental materials

[0026] Domestic waste paper fibers were obtained from Liansheng Paper (Longhai) Co., Ltd. Choline chloride and phosphoric acid were purchased from Shanghai Macklin Company.

[0027] 2. Experimental Methods

[0028] Step 1. Preparation of a deep eutectic solvent: Evenly mix choline chloride and phosphoric acid in proportion, react at a set temperature and speed until completely dissolved and a colorless transparent liquid is present at room temperature. Store DES in a sample bottle and place in a desiccator for later use.

[0029] Step 2: Preparation of biochar from waste paper fibers: First, waste paper fibers were pulverized in a grinder to a mesh size of 100-200 mesh. The waste paper fibers were weighed and placed in the lining of a PPL reactor. DES was added at a specific solid-to-liquid ratio. The waste paper fibers and DES were thoroughly mixed and then placed in the reactor. The mixture was heated to 150-210°C and held for a specified period of time. After the reaction, the mixture was cooled to room temperature and thoroughly washed with deionized water and ethanol until the filtrate was neutral. The sample was then dried in an oven to produce the biochar product.

[0030] 3. Scanning electron microscopy observation of biochar

[0031] A small amount of dry biochar powder sample was evenly adhered to the surface of the conductive adhesive, and then gold-sprayed after N2 blowing to enhance conductivity. The surface morphology of the sample was observed at different magnifications using a scanning electron microscope, and the measuring voltage was 5.0 kV.

[0032] 4. Analysis of specific surface area and pore structure of biochar

[0033] Using powdered biochar as the sample, an automatic surface area and pore size analyzer was used to measure the specific surface area and pore size distribution of the carbon material through N2 adsorption-desorption isotherm at 77.3K. The carbon material was degassed at 160℃ for 7h before testing.

[0034] 5. Elemental Analysis of Biochar

[0035] Weigh 4 mg of biochar sample and place it in the sample tank. Select CHNS mode, separate the biochar using an adsorption-desorption column, and then separate it using a chromatographic column. Determine the C, H, N, and O contents in the biochar using an analyzer.

[0036] 6. Adsorption of methylene blue (MB) by biochar

[0037] 40 mg of adsorbent and 50 mL of a 200 mg / L MB solution were added to a conical flask at a pH of 7.5, in triplicate. The suspension was incubated in a constant-temperature water bath oscillator at a constant rotation speed and a preset temperature for a period of time. After adsorption, the solution was filtered through a 0.45 μm aqueous filter membrane. The MB absorbance in the filtrate was measured at 665 nm using a UV-visible spectrophotometer, and its concentration was calculated. 0.1 M HCl was used as the desorbent for STC regeneration and recovery to investigate the recyclability of STC.

[0038] The calculation formulas for MB adsorption capacity and removal rate are as follows:

[0039] q e =V(C0-C e ) / W (1)

[0040] R=[(C0-C e ) / C0]×100% (2)

[0041] Where:

[0042] q e ——adsorption capacity, mg / g;

[0043] C0——initial concentration of the solution, mg / L;

[0044] C e ——equilibrium concentration of the solution, mg / L;

[0045] V——volume of solution, L;

[0046] W——mass of STC adsorbent, mg;

[0047] R——MB removal rate of STC, %.

[0048] 2. Preparation of Biochar Products

[0049] Example 1

[0050] Choline chloride and phosphoric acid were stirred at a molar ratio of 1:2 at 80°C, a rotation speed of 300 rpm, and a reaction time of 30 minutes until they were completely dissolved and became a colorless transparent liquid at room temperature. DES was stored in a sample bottle and placed in a desiccator for future use.

[0051] The waste paper fibers were crushed in a grinder to a mesh size of 100-200 mesh. 1g of waste paper fibers were weighed and placed in the lining of the PPL reactor. DES was added at a solid-liquid ratio of 1:14. After the waste paper fibers and DES were fully mixed, they were transferred to the reactor and heated to 210°C for 5 hours. After the reaction was completed, the fibers were cooled to room temperature and washed with deionized water and ethanol until the filtrate was neutral. The sample was dried in an oven at 60°C for 6 hours to obtain a biochar product. The scanning electron microscope image of the biochar product is shown below. Figure 1 shown.

[0052] Under the above conditions, the specific surface area and pore volume of biochar prepared with DES as solvent were 93.6043 m 2 / g and 0.228174cm 2 / g, with an average pore size of 10.5908nm. The carbon content was 59.72%, the hydrogen content was 4.40%, the oxygen content was 29.17%, and the nitrogen content was 0.33%. The biochar prepared under the above conditions was used to adsorb MB solution. 40mg of biochar and 50mL of a 200mg / L MB solution were added to a conical flask, the pH was adjusted to 7.5, and after stirring at a constant speed for 240min at room temperature, the methylene blue in the solution was completely adsorbed.

[0053] Example 2

[0054] Choline chloride and phosphoric acid were stirred at a molar ratio of 1:2 at 80°C, a rotation speed of 300 rpm, and a reaction time of 30 minutes until they were completely dissolved and became a colorless transparent liquid at room temperature. DES was stored in a sample bottle and placed in a desiccator for future use.

[0055] Put the waste paper fiber into a grinder and crush it into 100-200 meshes. Weigh 1g of waste paper fiber into the lining of the PPL reactor, add DES at a solid-liquid ratio of 1:10, mix the waste paper fiber raw material with DES thoroughly, put it into the reactor and heat it to 210℃, keep it warm for 7h, cool it to room temperature after the reaction is completed, wash it with deionized water and ethanol until the filtrate is neutral, and dry the sample in an oven at 80℃ for 5h to obtain the biochar product. After collecting the filtrate, rotary evaporate the mixture of water and ethanol at 80℃ for the next washing of biochar. Under the above conditions, the specific surface area and pore volume of the biochar prepared with DES as solvent were 88.4072m 2 / g and 0.220245cm 2 / g, with an average pore size of 10.1431 nm. The carbon content was 58.86%, the hydrogen content was 4.75%, the oxygen content was 27.28%, and the nitrogen content was 0.29%. The biochar prepared under the above conditions was used to adsorb MB solution. 40 mg of biochar and 50 mL of a 200 mg / L MB solution were added to a conical flask, the pH was adjusted to 7.5, and after stirring at a constant speed for 240 minutes at room temperature, the MB removal rate in the solution reached 97.43%.

[0056] Although the specific embodiments of the present invention are described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing waste paper fiber-based biochar, characterized by: The method comprises the following steps: Step 1, preparation of deep eutectic solvent DES: heating and stirring choline chloride and phosphoric acid, mixing them evenly, and forming a colorless transparent liquid at room temperature; Step 2: Preparation of biochar from waste paper fibers: (1) Put waste paper fibers into a grinder and grind them into 100-200 meshes; (2) Add waste paper fiber and DES into the reactor, mix them evenly, heat them, and keep them warm for reaction. After the reaction is completed, wash them thoroughly with deionized water and ethanol, and then dry them to obtain biochar.

2. The method for preparing waste paper fiber-based biochar according to claim 1, characterized in that: In step 1, the preparation conditions of the deep eutectic solvent are as follows: choline chloride and phosphoric acid are uniformly mixed in a molar ratio of 1:2, stirred at 80° C. and 300 rpm until completely dissolved, and a colorless transparent liquid is obtained at room temperature.

3. The method for preparing waste paper fiber-based biochar according to claim 1, characterized in that: In step 2, the waste paper fibers include deinked waste paper fibers or waste corrugated cardboard fibers.

4. The method for preparing waste paper fiber-based biochar according to claim 1, wherein: In the step 2, the solid-liquid ratio of the waste paper fiber raw material to DES is 1:10-1:14, the reaction temperature is 150-210° C., and the reaction time is 3-9 hours.

5. The method for preparing waste paper fiber-based biochar according to claim 1, characterized in that: In step 2, the drying temperature is 50-100° C. and the drying time is 4-8 hours.

6. A waste paper fiber-based biochar prepared according to the method for preparing waste paper fiber-based biochar according to any one of claims 1 to 5.

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