A method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator for electrical pretreatment.

Abstract

This invention provides a method for using triboelectric nanogenerators (TENGs) for enzymatic deinking of mixed office waste paper through electro-pretreatment. The invention is based on a PANI-modified cellulose / PDMS composite material to prepare tubular TENGs. Using the tubular TENGs and white water as a base, different amounts of electricity are generated at different flow rates. This generated electricity is then used to treat MOW (mixed waste paper) pulp, followed by enzymatic deinking using cellulase, amylase, or xylanase. The brightness of the enzymatically deinked pulp is improved after electro-pretreatment. In the white water system, the electrical output performance increases with the flow rate of the white water in the pipes. The properties of the generated white water change with different flow rates; the pH, turbidity, CD value, and particle size of the generated MOW white water decrease to varying degrees, while the conductivity and zeta potential increase to varying degrees.

Description

Technical Field

[0001] This invention relates to the field of clean pulping and papermaking, specifically to an environmentally friendly pipeline-shaped triboelectric nanogenerator (P-TENGs) that generates static electricity through a white water system for enzymatic deinking of mixed office waste paper (MOW) via electro-pretreatment. Background Technology

[0002] With my country's economic development, the country's requirements for environmental protection are becoming increasingly stringent. Environmental protection has become a major issue concerning the survival and development of the pulp and paper industry. As problems such as raw material shortages and energy scarcity in the paper industry intensify, the recycling of secondary fibers is becoming increasingly important, as secondary fibers play an irreplaceable role in the paper industry. Waste paper recycling first requires deinking. Chemical deinking is prone to secondary pollution, while enzymatic deinking can save a significant amount of chemicals and reduce the COD of wastewater. With the increasing demand for sustainable and renewable energy, triboelectric nanogenerators (TENGs) have recently attracted attention as a novel energy harvesting device. Triboelectric materials are the core components of TENGs, and modified cellulose is a highly promising triboelectric material. Developing it into an environmentally friendly TENG device, which collects energy from the paper production process and applies it to bio-enzymatic deinking, promotes the recycling of secondary fibers. This can protect forest resources, reduce environmental pollution, and lower water and energy consumption, resulting in significant economic, social, and economic benefits. Summary of the Invention

[0003] In order to collect energy from the papermaking process for deinking mixed office waste paper, this invention provides a method for enzymatic deinking of mixed office waste paper (MOW) through electro-pretreatment using triboelectric nanogenerators (P-TENGs). The method generates static electricity through environmentally friendly pipeline-shaped triboelectric nanogenerators (P-TENGs) in a white water system for electro-pretreatment of mixed office waste paper (MOW) through enzymatic deinking.

[0004] The above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0005] A method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator for electrical pretreatment includes the following steps:

[0006] S1. The fabrication methods of the tubular triboelectric nanogenerator include:

[0007] (1) Preparation of PANI-modified cellulose / PDMS composite material: Polyaniline-modified cellulose was prepared by chemical oxidation polymerization in an ice bath using aniline as monomer, cellulose as stabilizer, HCl solution as dopant and ammonium persulfate as initiator. The dried polyaniline-modified cellulose was stirred and dispersed in polydimethylsiloxane stock solution under ultrasonic conditions. Then, a curing agent was added, and after thorough stirring, the mixture was placed in a vacuum environment to remove air bubbles. The mixed liquid was poured into a film mold and polydimethylsiloxane was cured to obtain PANI-modified cellulose / PDMS composite material.

[0008] (2) The PANI-modified cellulose / PDMS composite material prepared in step (1) is made into a hollow tubular structure: the PANI-modified cellulose / PDMS composite material is poured into a film mold for molding to obtain a hollow tubular structure; a metal tube is fitted on the outer wall of the hollow tubular structure, and the metal tube is connected to the wire to form a tubular triboelectric nanogenerator.

[0009] S2. The method for using the tubular triboelectric nanogenerator in step S1 for enzymatic deinking of mixed office waste paper through electrical pretreatment includes:

[0010] The hollow tubular structure is connected to water pipes at both ends, and water flows in the pipes. Water is generated by friction in contact with the hollow tubular structure. The electricity output by the triboelectric nanogenerator is transmitted to the mixed office waste pulp through wires connected to electrodes for electrical pretreatment.

[0011] Furthermore, the water flowing in the pipeline is white water used in papermaking.

[0012] Furthermore, the flow rate of water in the pipeline is 50–400 mL / min.

[0013] Furthermore, the mass concentration of the mixed office waste pulp is 8%.

[0014] Furthermore, the electrical pretreatment time is 30 minutes.

[0015] Furthermore, it also includes enzymatic deinking after electro-pretreatment. The process includes enzymatic deinking of the pretreated office waste pulp with cellulase, amylase or xylanase. The deinking conditions are: OP-10 deinking aid at a dosage of 0.06%, pH = 8.5, temperature of 50℃, effective enzyme activity of 0.6 U / g oven-dry pulp, flotation concentration of 1%, and flotation time of 10 min.

[0016] Furthermore, the mass ratio of aniline, cellulose, and ammonium persulfate is 1:1:1.25.

[0017] Furthermore, the curing agent is tetraethyl orthosilicate.

[0018] Furthermore, the mass ratio of the polyaniline-modified cellulose to the polydimethylsiloxane stock solution is 0.05:1; the mass ratio of the polydimethylsiloxane stock solution to tetraethyl orthosilicate is 10:1.

[0019] Furthermore, the curing is carried out in an oven at 70°C; the molding process is carried out in an oven at 70°C.

[0020] The present invention has the following beneficial effects:

[0021] (1) In this invention, polyaniline-modified cellulose (PANI-modified cellulose) is filled inside polydimethylsiloxane (PDMS). During the triboelectric generation process of PDMS, the PANI-modified cellulose becomes the path for electron flow, increasing the surface charge density and thus enhancing the electrical output performance of TENGs. This triboelectric material has a simple process, low cost, and can generate high electrical output.

[0022] (2) The papermaking process involves a large amount of liquid flow, making it an excellent application scenario for the tubular solid-liquid TENGs of this invention. This invention uses a PANI-modified cellulose / PDMS composite material to create a tubular structure as the inner wall of the pipe, collecting the energy from the liquid flow. The collected electrical energy is then used in processes such as white water degradation and enzymatic deinking of waste paper. This provides a feasible solution for the practical application of TENGs in the papermaking process.

[0023] (3) Beneficial results compared with enzymatic deinking of pulp without electrical pretreatment (0 mL / min):

[0024] Electrochemical pretreatment increased the whiteness of cellulase slurry by 2.56% at a flow rate of 200 mL / min. Electrochemical pretreatment increased the whiteness of amylase slurry by 2.56% at a flow rate of 50 mL / min. Electrochemical pretreatment increased the whiteness of xylanase slurry by 2.52% at a flow rate of 50 mL / min.

[0025] (4) In the white water system of this invention, the electrical output performance increases with the increase of the white water flow rate in the pipeline. The properties of the white water used for power generation change with different flow rates. The pH, turbidity, CD value and particle size of the white water after power generation decrease to varying degrees, while the conductivity and Zeta potential of the white water after power generation increase to varying degrees. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the tubular triboelectric nanogenerator of the present invention.

[0027] Figure 2 This is a schematic diagram of a tubular triboelectric nanogenerator for the electrical pretreatment of MOW waste paper pulp according to the present invention.

[0028] Explanation of reference numerals in the attached diagram: 1-PANI-CEL / PDMS tube, 2-Hose, 3-Wire, 4-Electrometer, 5-Peristaltic pump, 6-MOW white water, 7-MOW waste paper pulp. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the embodiments.

[0030] As attached Figure 1 As shown, the present invention discloses a tubular triboelectric nanogenerator, which is based on a PANI-modified cellulose / PDMS composite material to form a hollow tubular structure. A copper tube is fitted on the outer wall of the tubular structure for conduction and support, serving as an electrode to simulate the tubular equipment in the papermaking process, thus forming a TENGSs device (PANI-CEL / PDMS tube). A wire is connected to the outer wall of the copper tube to the positive terminal of an electrometer, and the negative terminal of the electrometer is grounded, forming a single-electrode TENGs. The two ends of the device are connected to flexible tubes, and a peristaltic pump is connected to the flexible tubes to form a tubular TENGs.

[0031] As attached Figure 2 As shown, a hollow tubular structure was fabricated using PANI-modified cellulose / PDMS composite material. A copper tube was fitted onto the outer wall of this structure to create a TENG device (PANI-CEL / PDMS tube). Flexible tubes were connected to both ends of the device, and peristaltic pumps were attached to these tubes. The peristaltic pumps drove MOW (polyurethane) white water to flow through the tubes, contacting the hollow tubular structure and generating static electricity through friction. The electricity output from this triboelectric nanogenerator was then fed into the MOW waste paper pulp via a wire connected to a platinum electrode for electrical pretreatment. The other end of the platinum electrode in the MOW waste paper pulp was connected to an electrometer via a wire. The electrometer was used to collect electrical signals and also served as a grounding wire.

[0032] Example 1

[0033] A method for preparing a tubular triboelectric nanogenerator includes the following steps:

[0034] (1) Preparation of PANI-modified cellulose / PDMS composite material: 1g aniline as monomer, 1g lignocellulose as stabilizer, 100mL 1mol / L HCl solution as dopant, and 1.25g ammonium persulfate as initiator were used to prepare polyaniline-modified cellulose (PANI-modified cellulose) by chemical oxidation polymerization in an ice bath; the dried PANI-modified cellulose was stirred and dispersed in polydimethylsiloxane stock solution (PDMS stock solution) under ultrasonic conditions for 0.5h, the mass ratio of PANI-modified cellulose to PDMS stock solution was 0.05:1, and then tetraethyl orthosilicate (TEOS) curing agent was added, the mass ratio of PDMS stock solution to TEOS in the reaction system was 10:1, and after thorough stirring, the mixture was placed in a vacuum environment to remove air bubbles, the mixed liquid was poured into a film mold and then cured in an oven at 70℃ to obtain PANI-modified cellulose / PDMS composite material.

[0035] (2) The PANI-modified cellulose / PDMS composite material prepared in step (1) is made into a hollow tubular structure: the PANI-modified cellulose / PDMS composite material is poured into a film mold and placed in an oven at 70°C for 1 hour to obtain a hollow tubular structure; a copper tube is fitted on the outer wall of the hollow tubular structure and connected to a wire to form a tubular triboelectric nanogenerator.

[0036] MOW simulation of white water preparation:

[0037] Mixed office waste paper (MOW) was torn into 5×5cm pieces, mixed thoroughly, and then stored in a sealed bag for at least 24 hours to equilibrate the moisture content. After measuring the moisture content, an appropriate amount of MOW was weighed and prepared into 10% pulp. This pulp was then processed in a high-consistency pulper at 60°C and 300 rpm for 20 minutes. The pulp was collected using a 100-mesh sieve, shredded, and stored in a sealed bag. The pulp was then stored in a refrigerator for 24 hours to equilibrate the moisture content, and the moisture content was measured for future use.

[0038] Weigh 20g of oven-dried pulp to prepare a 2% pulp concentration pulp suspension, and stir it in a constant-temperature water bath at 400 rpm for 1 hour using a mechanical stirrer. Quickly pour the thoroughly stirred pulp suspension into a dynamic water filter with a 200-mesh filter screen, and rotate the rotor at 800 rpm. The liquid obtained from the outlet of the dynamic water filter is the MOW simulated white water.

[0039] Output performance testing of tubular triboelectric nanogenerators:

[0040] As attached Figure 1As shown, a copper tube is fitted onto the outer wall of the tubular structure for conduction and support, serving as an electrode to simulate the piping equipment in the papermaking process, thus creating a TENG device (PANI-CEL / PDMS tube). A wire is connected to the outer wall of the copper tube to the positive terminal of an electrometer, and the negative terminal of the electrometer is grounded, forming a single-electrode TENG. The two ends of the device are connected to flexible tubes, and peristaltic pumps are connected to the flexible tubes. The peristaltic pumps drive MOW to simulate white water flowing in the pipes and contacting the hollow tubular structure to generate static electricity through friction.

[0041] The MOW (Medium-to-Wave Power) simulation of white water at four different flow rates—0 mL / min, 50 mL / min, 200 mL / min, and 400 mL / min—generated electricity. At a flow rate of 50 mL / min, the voltage was 13.64 V, the current was 1.01 μA, and the charge was 1.01 nC; at 200 mL / min, the voltage was 18.86 V, the current was 5.49 μA, and the charge was 1.16 nC; and at 400 mL / min, the voltage was 23.24 V, the current was 6.29 μA, and the charge was 9.41 nC. The results showed that in the white water system, the electrical output performance increased with the increase of the white water flow rate in the pipe. At a flow rate of 400 mL / min, the voltage was 23.24 V, the current was 6.29 μA, and the charge was 9.41 nC.

[0042] MOW simulation of basic properties of white water determination:

[0043] A certain amount of white water was taken and its pH, conductivity, turbidity, cation requirement (CD), zeta potential and particle size were measured using a pH meter, conductivity meter, turbidity meter, charge titrator and zeta potential and nanoparticle size analyzer.

[0044] Detection results: At four different flow rates (0 mL / min, 50 mL / min, 200 mL / min, and 400 mL / min), the pH values ​​of the white water were 8.8, 8.49, 8.56, and 8.44, respectively; the electrical conductivity was 108.1 μS / cm, 108.6 μS / cm, 110.1 μS / cm, and 111.8 μS / cm, respectively; the turbidity was 295 NTU, 301 NTU, 275 NTU, and 236 NTU, respectively; the CD values ​​were 1.21 mEq / L, 1.09 mEq / L, 1.22 mEq / L, and 1.16 mEq / L, respectively; the Zeta potentials were -8.43 mV, -9.69 mV, -8.85 mV, and -8.93 mV, respectively; and the particle sizes were 486 nm, 576 nm, 603 nm, and 563 nm, respectively. Measurement results: The properties of the white water generated by power generation changed with different flow rates. The pH, turbidity, CD value and particle size of the simulated white water after power generation decreased to varying degrees, while the conductivity and Zeta potential of the simulated white water after power generation increased to varying degrees.

[0045] Example 2

[0046] A method for enzymatic deinking of mixed office waste paper using a tubular triboelectric nanogenerator (P-TENG) for electrical pretreatment includes the following steps:

[0047] S1. The fabrication method of the tubular triboelectric nanogenerator includes the following steps:

[0048] (1) Same as step (1) in Example 1.

[0049] (2) is the same as step (2) in Example 1.

[0050] S2. The method for using the tubular triboelectric nanogenerator in step S1 for enzymatic deinking of mixed office waste paper through electrical pretreatment includes:

[0051] As attached Figure 2 As shown, a TENG (PANI-CEL / PDMS) device is fabricated by fitting a copper tube onto the outer wall of a tubular structure. Flexible tubes are connected to both ends of the device, and peristaltic pumps are attached to these tubes. The peristaltic pumps drive MOW (waxygen-generated wastewater) to flow through the tubes, contacting the hollow tubular structure and generating static electricity through friction. The electricity output from the triboelectric nanogenerator is then fed into the MOW waste paper pulp via a platinum electrode connected by wires for electrochemical pretreatment. The other end of the platinum electrode in the MOW waste paper pulp is connected to an electrometer via wires. The electrometer collects the electrical signal and serves as a grounding wire. After electrochemical pretreatment, enzymatic deinking is performed.

[0052] Preparation of the MOW waste paper pulp:

[0053] Tear MOW waste paper (laser printing paper: inkjet copy paper = 1:1) into uniform pieces, soak for 24 hours, adjust the pulp consistency to 1%, and process in a Walle pulper for 30 minutes to basically break down the shredded paper into pulp. Balance the moisture content for later use.

[0054] The process conditions for electrical pretreatment are as follows:

[0055] Calculate 10g of MOW waste paper pulp based on its oven-dry weight, and prepare an electrostatic treatment environment with a waste paper pulp mass concentration of 8%. Use P-TENG to generate electricity with white water at four different flow rates: 0mL / min, 50mL / min, 200mL / min, and 400mL / min. Use the electricity generated at different flow rates to treat the 8% MOW pulp mass concentration for 30 minutes.

[0056] The process conditions for enzymatic deinking after electro-pretreatment are as follows:

[0057] The pretreated pulp was enzymatically deinked using cellulase. The deinking conditions were as follows: OP-10 deinking aid at a dosage of 0.06%, pH = 8.5, temperature of 50℃, effective enzyme activity of 0.6 U / g oven-dry pulp, flotation concentration of 1%, and flotation time of 10 min.

[0058] Whiteness test of enzymatic deinking pulp after electro-pretreatment:

[0059] Take the pulp after enzymatic deinking and form it into a weight of 70g / m³. 2 Paper sheets were tested for whiteness. Results: The whiteness of cellulase-deinked pulp after electro-pretreatment at four different flow rates (0 mL / min, 50 mL / min, 200 mL / min, and 400 mL / min) was 59.03% ISO, 59.82% ISO, 60.54% ISO, and 60.28% ISO, respectively. Compared to enzymatically deinked pulp without electro-pretreatment (0 mL / min), the whiteness of cellulase-deinked pulp after electro-pretreatment increased by 2.56% at a flow rate of 200 mL / min.

[0060] Example 3

[0061] Unlike Example 2, the enzymatic deinking after electro-pretreatment uses amylase for enzymatic deinking.

[0062] Whiteness test of enzymatic deinking pulp after electro-pretreatment:

[0063] Take the pulp after enzymatic deinking and form it into a weight of 70g / m³. 2 Paper sheets were tested for whiteness. Results: The whiteness of the amylase-deinked pulp after electro-pretreatment at four different flow rates (0 mL / min, 50 mL / min, 200 mL / min, and 400 mL / min) was 58.97% ISO, 60.48% ISO, 59.63% ISO, and 59.61% ISO, respectively. Compared to enzymatically deinked pulp without electro-pretreatment (0 mL / min), the whiteness of the amylase-deinked pulp after electro-pretreatment increased by 2.56% at a flow rate of 50 mL / min.

[0064] Example 4

[0065] Unlike Example 2, the enzymatic deinking after electrical pretreatment uses xylanase for enzymatic deinking.

[0066] Whiteness test of enzymatic deinking pulp after electro-pretreatment:

[0067] Take the pulp after enzymatic deinking and form it into a weight of 70g / m³. 2Paper sheets were tested for whiteness. Results: The whiteness of xylanase-deinked pulp after electro-pretreatment at four different flow rates (0 mL / min, 50 mL / min, 200 mL / min, and 400 mL / min) was 58.83% ISO, 61.35% ISO, 60.00% ISO, and 60.11% ISO, respectively. Compared to enzymatically deinked pulp without electro-pretreatment (0 mL / min), the whiteness of xylanase-deinked pulp after electro-pretreatment increased by 2.52% at a flow rate of 50 mL / min.

Claims

1. A method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator for electro-pretreatment, characterized in that, Includes the following steps: S1. The fabrication methods of the tubular triboelectric nanogenerator include: (1) Preparation of PANI-modified cellulose / PDMS composite material: Polyaniline-modified cellulose was prepared by chemical oxidation polymerization in an ice bath using aniline as monomer, cellulose as stabilizer, HCl solution as dopant, and ammonium persulfate as initiator. The dried polyaniline-modified cellulose was stirred and dispersed in polydimethylsiloxane stock solution under ultrasonic conditions. Then, a curing agent was added, and after thorough stirring, the mixture was placed in a vacuum environment to remove air bubbles. The mixed liquid was poured into a film mold and polydimethylsiloxane was cured to obtain PANI-modified cellulose / PDMS composite material. The mass ratio of aniline, cellulose and ammonium persulfate was 1:1:1.

25. The mass ratio of polyaniline-modified cellulose to polydimethylsiloxane stock solution was 0.05:

1. The curing agent was tetraethyl orthosilicate. The mass ratio of polydimethylsiloxane stock solution to tetraethyl orthosilicate was 10:

1. (2) The PANI-modified cellulose / PDMS composite material prepared in step (1) is made into a hollow tubular structure: the PANI-modified cellulose / PDMS composite material is poured into a film mold for molding to obtain a hollow tubular structure; a metal tube is fitted on the outer wall of the hollow tubular structure, and the metal tube is connected to the wire to form a tubular triboelectric nanogenerator. S2. The method for using the tubular triboelectric nanogenerator in step S1 for enzymatic deinking of mixed office waste paper through electrical pretreatment includes: The hollow tubular structure is connected to water pipes at both ends, and water flows in the pipes. The water is generated by friction through contact with the hollow tubular structure. The electricity output by the triboelectric nanogenerator is introduced into the mixed office waste paper pulp through wires connected to electrodes for electrical pretreatment. After electrical pretreatment, enzymatic deinking is performed.

2. The method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator according to claim 1, characterized in that, The water flowing in the pipeline is the white water used in papermaking.

3. The method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator according to claim 1, characterized in that, The water flow rate in the pipeline is 50~400mL / min.

4. The method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator according to claim 1, characterized in that, The mass concentration of the mixed office waste paper pulp is 8%.

5. The method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator according to claim 1, characterized in that, The electrical pretreatment time is 30 minutes.

6. The method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator according to claim 1, characterized in that, The enzymatic deinking process includes: enzymatically deinking pretreated office waste pulp with cellulase, amylase or xylanase. The deinking conditions are: OP-10 deinking aid at a dosage of 0.06%, pH=8.5, temperature at 50℃, effective enzyme activity of 0.6 U / g oven-dry pulp, flotation concentration of 1%, and flotation time of 10 min.

7. The method for enzymatic deinking of mixed office waste paper using a triboelectric nanogenerator according to claim 1, characterized in that, The curing is carried out in an oven at 70°C; the molding process is carried out in an oven at 70°C.

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