Method for extracting graphene from single-use plastic.

Abstract

Abstract of the Invention A method for the extraction of graphene, and more particularly the method of extracting graphene by continuous wave fiber laser. The laser extraction method of I 0 graphene fabrication is a one-step process under ambient conditions for large-scale production of graphene. It is an economical, quick, chemical-free, simple yet effective means for recycling single-use plastic, agriculture, and food waste, etc., for large-scale production of "gree~" graphene.

Description

Field of the Invention:

[001] The present disclosure broadly relates to the method for the synthesis of graphene and other materials and more particularly the method for the large-scale production of graphene from single-use plastics by continuous wave fiber laser.Background of the Invention:

[002] One of the most persistent pollutants on the earth is plastic. "Consumption of one to five trillion plastic bags is estimated annually worldwide.Single-use plastic products epitomize convenience, but the damage they cause through litter is a major threat to the environment and human health. Most plastic recycling technologies are ineffective and only about 9% of produced plastic is recycled. As per the estimation of CIEL, the production, and incineration of plastic would add 850 million metric tons of greenhouse gases to the atmosphere. Pollution due to single-use plastic products has become an important environmental challenge confronting all countries.

[003] The method of graphene production from single-use plastic may openavenues for recycling single-use plastic for future large-scale production of graphene.

[004] Further, the prior art has failed to cope with the challenge of large-scale production of graphene from single-use plastic in a simple, economical, and efficient approach.

[005] For instance, in the CN-113880076-A: The invention provides high-purity graphene prepared by taking garbage as raw material, and a preparation method and application thereof, wherein multilayer graphene and porous nano graphite can be obtained by performing pre-treatment and laser scanning on a garbage mixture mainly comprising a carbon-containing polymer; the powdery graphene can be obtained by shearing and stripping in the steps; the powdery graphene can be purified to obtain high-purity graphene.

[006] In another patent US-20170327379-A1: A method for making graphene comprising the steps of reacting a catalyst with a plurality of source carbon solids; creating a graphene precursor from the reaction of the catalyst with the plurality of source carbon solids; pyrolyzing the graphene precursor; and extracting graphene from the pyrolyzed graphene precursor. Creating a graphene precursor comprises the steps of creating a solution comprising deionized water and the catalyst; reacting the catalyst with the plurality of source carbon solids by mixing the plurality of source carbon solids into the solution comprising deionized water and the catalyst; heating the solution; and stirring the heated mixture until substantially all liquid has evaporated. Pyrolyzing the graphene precursor is done by placing the graphene precursor in a furnace; creating a non-oxidizing environment within the furnace; heating the furnace; and annealing the graphene precursor.

[007] Further in Patent EP-3763672-A1: The invention provides a method and equipment for extracting carbon materials from plastics. Particularly, the method produces nanostructured carbon materials by heating at least one salt (e.g., NaCl) arid at least one plastic material (e.g. polyethylene terephthalate) to a temperature greater than the melting point of the said salt, in which the molten state of the said salt protects the carbonaceous material from oxidation. Moreover, molten salt promotes the graphitization of carbon materials. The product is in the form of graphene nano-flakes with high conductivity and high surface area.

[008] The existing physical, chemical, and mechanical methods of producing graphene that is present today are slow, require long processing times, are non-scalable, and present challenges of heterogeneous doping and tunnel barriers which cause large contact resistance and hinder application development.

[009] Therefore, there is a need to explore other effective methods of graphene fabrication from single-use plastic for large-scale production of graphene.Object of the Invention:

[0010] The principal object of the present invention is to develop a method for the synthesis of graphene, and more particularly the method of synthesizinggraphene from single-use plastics by continuous wave fiber laser.Summary of the Invention:

[0011] This summary is provided to introduce a selection of concepts in asimplified format that is further described in the detailed description of theinvention. This summary is not intended to identify key or essential inventive concepts of the claimed subject matter, nor is it intended for determining the scope of the claimed subject matter.

[0012] The invention elaborates a method of synthesizing graphene fromsingle-use plastics by continuous wave fiber laser.

[0013] In accordance with an embodiment of the present invention, multilayered, crystalline graphene is extracted from single-use plastic by using a CW fiber laser.

[0014] In yet another embodiment of the invention, a process of extractinggraphene from a feedstock carbon source that is substantially not graphene byapplying laser energy comprising the steps: mincing the feedstock carbon source into smaller sizes, mixing the minced carbon source with an absolute carbon source to form a mixture, applying high laser energy to the mixture in a vacuum, extracting graphene from the feedstock carbon source.

[0015] To further clarify the advantages and features of the present invention,a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended figures. It is appreciated that these figures depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying figures.Brief Description of Figures:

[0016] To further clarify the advantages and aspects of the invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in accordance with various embodiments of the invention, wherein:

[0017] Figure 1, illustrates the key unit operations and flowchart for extracting graphene from a feedstock carbon source that is substantially not graphene by applying a continuous-wave fiber laser, in accordance with an embodiment of the present invention;

[0018] Figure 2, illustrates (a) a FESEM image of single-use waste plastic (control) at 70,000 X; (b) a continuous-wave fiber laser extracted graphene showing crystalline structures at 150,000 X; (c) a Video Image, and; (d) a 2D structure of Continuous Wave Fiber laser extracted sample as observed with Raman spectroscopy at 532 nm excitation, in accordance with an embodiment of the present invention, and

[0019] Figure 3, illustrates (a) Raman Spectra of single-use plastic; (b)continuous wave fiber laser extracted sample collected with 532 nm excitation; (c) core level high-resolution XPS C1s spectra of graphene extracted with continuous wave fiber laser, in accordance with an embodiment of the present invention.

[0020] It may be noted that to the extent possible reference numerals have been used to represent like elements in the drawings. Further, those of ordinary skill in the art will appreciate those elements in the drawings are illustrated for simplicity and may not have been necessarily drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of aspects of the invention.

[0021] Furthermore, one or more elements may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0022] Further, skilled artisans will appreciate those elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device, may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the figures with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.Detailed Description:

[0023] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

[0024] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

[0025] Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristicdescribed in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in an embodiment", "in another embodiment", and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0026] The terms "comprise", "comprising", or any other variations thereof, are intended to cover a nonexclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional subsystems or additional elements or additional structures or additional components.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting. Embodiments of the present invention will be described below in detail with reference to the accompanying figures.

[0028] The present invention broadly relates to the methods for the synthesis of graphene and other materials, and more particularly the method for the large-scale production of graphene from single-use plastics by continuous wave fiber laser.

[0029] Referring to Figure 1: illustrates the key unit operations and flowchart for extracting graphene from a feedstock carbon source that is substantially not graphene by applying a continuous wave fiber laser showing the steps: mincing plastic pieces in 1cm2 size, mixing plastic with 1% charcoal powder by weight of minced plastic, applying continuous-wave fiber laser at 1000 watts power in the vacuum, extracting graphene from the mixture, Checking the quality of graphene using Raman shift cm-1, Observing the images of graphene to check the purity of graphene under FESEM, in accordance with an embodiment of the present invention.

[0030] Referring to Figure 2: illustrates (a) a FESEM image of single-use waste plastic (control) at 70,000 X; (b) a Continuous-wave fiber laser extracted graphene showing crystalline structures at 150,000 X; (c) a Video Image, and;(d) a 2D structure of Continuous Wave Fiber laser extracted sample as = observed with Raman spectroscopy at 532 nm excitation, in accordance with an embodiment of the present invention.

[0031] Referring to Figure 3: illustrates (a) Raman Spectra of single-useplastic; (b) continuous wave fiber laser extracted sample collected with 532 nmexcitation; and (c) Core level high-resolution XPS C1s spectra of graphene extracted with continuous wave fiber laser, in accordance with an embodiment of the present invention.

[0032] In an embodiment of the present invention discloses a process for theextraction of graphene from a feedstock carbon source that is substantially notgraphene by applying laser energy comprising the steps: Mincing the feedstock carbon source into smaller sizes; Mixing the minced feedstock carbon source with an absolute carbon source to form a mixture; Applying the laser energy to the mixture at high voltage in a vacuum; Extracting graphene from the feedstock carbon source.

[0033] In another embodiment of the invention, the said feedstock carbon source is at least one selected from a group comprising single-use plastic, household waste, factory waste, and combinations thereof.

[0034] In yet another embodiment of- the invention, the feedstock carbonsource is minced into pieces smaller than or equal to 1cm2 in size.

[0035] In another embodiment of the invention, the absolute carbon source is at least one selected from a group comprising charcoal, carbon black, and combinations thereof.

[0036] In an embodiment of the invention, the feedstock, carbon source ismixed with an absolute carbon source at a percentage of 0.5 to 1 percent by weight.

[0037] In yet another embodiment of the invention the laser energy source is a continuous wave Fiber (CW Fiber) Laser.

[0038] In another embodiment of the invention, the CW fiber laser is transmitted by fiber and QBH connector with water cooling compact structureas the adjustable, continuous beam of low-power visible light, and very highenergy power of near-infrared fiber lasers (1000 - 2000 Watts) with 10 mm burning range at room temperature (25 - 35°C) in the vacuum.

[0039] In yet another embodiment of the invention, the CW fiber laser is applied for a duration of 60-120 seconds to give 1.5 to 2 Kgs of high-qualitygraphene from 2.5 Kgs single-use plastic as feedstock in the vacuum.

[0040] In an embodiment of the invention, the said process results in the formation of valuable gases like hydrogen that can be captured, for industrial use.

[0041] In another embodiment of the invention, a multi-layered, crystalline green graphene is extracted from single-use plastic as the feedstock carbonby the process of CW fiber laserDetails of invention

[0042] The present invention relates to a method of synthesizing graphene,from single-use plastics by continuous wave fiber laser.

[0043] One of the most persistent pollutants on Earth is plastic. Consumption of one to five trillion plastic bags is estimated annually worldwide. Single-use plastic products epitomize convenience, but the damage they cause through litter is a major threat to the environment and human health. Most plasticrecycling technologies are ineffective and only about 9% of produced plastic is recycled. As per the estimation of CIEL, the production, and incineration of plastic would add 850 million metric tons of greenhouse gases to the atmosphere. Pollution due to single-use plastic products has become an important environmental challenge confronting all countries.

[0044] The laser extraction method of graphene fabrication illustrated in this work is a cheap, quick, chemical-free, very effective, simple, fast, and one-step process under ambient conditions and opens avenues for recycling single-use plastic for future large-scale production of "green" graphene.

[0045] Innovation is an improvement to existing physical, chemical, and mechanical methods of producing graphene that is slow, require long processing times, are non-scalable, and present challenges of heterogeneous doping and tunnel barriers which cause large contact resistance and hinder application development.

[0046] In the present invention Graphene was extracted from single-use waste plastic employing an energy-efficient, affordable, and easy continuous wave fiber laser and the whole process finished in 60 seconds (@ power cost of Rs 60 / hour to produce 1.5 to 2 Kgs of graphene approximately).

[0047] The developed method is efficient (> 90%), and can be extended to extracte graphene from a wide variety of plastics, agriculture waste, and food wasteApplication of the Invention

[0048] Graphene, a monolayer of sp2-hybridized carbon atoms, has received widespread scientific interest due to its unique structure and fascinating properties such as large surface area, high carrier mobility, high electrical conductivity, excellent thermal conductivity, mechanical strength, electronic, and optical properties, zero bandgap, ballistic transport, and tensile strength.It is widely used in different fields of material science, biomedical science, and energy for its potential to develop a large number of technologically important devices like bolometers, holograms; hydrogen storage, sensors, solar cells, supercapacitors, optoelectronic devices, .nanocomposites, electrothermal heaters, flat lenses, field-effect transistors, lithium-ion batteries, thermal sound sources, water purification, cancer treatment, etc.

[0049] The final product graphene is used as raw-material for various industrial applications in the electronic and automotive industries, aerospace, telecommunications, medical and energy storage, and generation.

[0050] Graphene has very large potential in the agriculture, industry, such as coffee, food industry, and the environment, as a plant growth stimulator and in fertilizers, Nanoencapsulation and smart-release systems, antifungal and antibacterial agents, smart packaging, water treatment and ultrafiltration, contaminant removal, pesticide and insecticide quantitation, detection systems, and precision agriculture. Despite its high potential, there are many challenges and mass production of graphene with minimum material wastage requires simplification of the fabrication process.Example:

[0051] The results of the present study clearly demonstrated the ability of FESEM, EDX, XPS, and the alpha300 RA confocal Raman-AFM microscope system to perform the non-destructive characterization of graphene.

[0052] In the present study, an attempt was made to extracte graphene, from single-use waste plastic, using a continuous-wave fiber laser and CO2 laser.Further, the characterization of the graphene spectrum has been extensively exploited by Raman spectroscopy due to its importance in the field of carbonresearch. Raman spectroscopy is centered on the inelastic scattering of % monochromatic light, usually from a laser source. The frequency of photons in laser light changes upon interaction with a sample. Photons absorbed by the sample are re-emitted. The frequency of the re-emitted photons is shifted up or down with respect to the original monochromatic frequency. This Raman shift provides information about rotational vibrational and other low-frequency transitions in molecules. The Raman spectra of all graphene display a broad G-band around 1570-1580 cm-1 corresponding to the first-order scattering of the E2g mode. The prominent D-band at 1350-1360 cm-1 results from structuraldefects. Hence, in the present study, laser-extracted samples were compared for quality and defects using FESEM and Raman Spectroscopy.

[0053] It was observed that the extraction of graphene using a continuous fiber laser was very efficient than a CO2 laser as the whole extraction process could be finished in a few minutes. The Raman spectra of graphene yielded accurate data on the electronic band structure, crystal structure, the electron-phonon interaction in sp2 carbon systems, and the photon energy dispersion. The surface morphology of laser-induced samples studied, with FESEM. The single-use plastic image was used as a control. The low and high magnification of CW fiber laser extracted samples dearly showed uniform extraction and crystalline structures of graphene.

[0054] Raman spectra of the laser-induced samples showed four distinguishable bands centered at the D band, G band, 2D band, and (D + G band). In Raman spectroscopy, the D-band is attributed to the phonon scattering at defect / impurity sites, while the G-band is the stretching mode of sp2-hybridized carbon atoms. If the D peak intensity is higher, the sample is having more defects in the graphene network; whereas if the G band is prominent, the sample is said to be graphene, in nature with a crystalline structure. The existence of 1346 cm-1 (D band) and 1577.8 cm-1 (G band) inthe sample extracted with CW fiber laser confirmed the formation of graphene - with lesser defects and crystalline structure.

[0055] The 2D and D+G bands are the second-order of the D band and a combination of D and G bands, respectively. The relative intensity of the D to G band (ID / IG) and the 2D to G band (I2D / IG) is employed for the estimation of the disorder level. The ratio of ID / IG is 0.4764, whereas the IG / I 2D ratio is 1.52 for the pristine graphene extracted with CW fiber laser. The almost equal intensity of D and G bands (1.21) in single-use waste plastic samples (control) implies a large fraction of structural disorder. The single-use plastic film had a crystalline size of 50 microns; this size was reduced afterward to - 9.24 nm.The increase in the ratio between the intensity of G and 2D peak, I(G) / I(2D), indicated an increase in the number of graphene layers in the CW fiber laserextracted sample. I(G) / I(D) values, of CW fiber laser extracted samples and plastic (control) were calculated as 9.24, and 3.62, respectively. The highest I(G) / I(2D) ratio of the CW fiber laser extracted sample demonstrated the largest number of graphene layers.

[0056] A similar formation of graphene-like carbon using a range of synthetic polymers and natural materials was demonstrated by several groups. Multiple-laser passes and defocused lasers were used to produce laser-induced graphene. The process involved the identification of a laser power, range of process parameters, and scan speed, that yielded 3D porous, graphene-like carbon. Non-optimal laser parameters lead to over-exposure effects like oxidation, material ablation, re-deposition, or combinations of these, and under-exposure effects like melting or incomplete graphitization. This complex materials challenge could not be achieved through annealing alone. The use of single-use waste plastic materials as feedstock and fast, scalable, easy, and energy-efficient CW fiber laser extraction method of graphene fabrication illustrated in this work, opens avenues for recycling single-use waste plastic for future large-scale production of "green" graphene.Advantages

[0057] The final product graphene is used as raw material for various industrial applications in the electronic and automotive industries, aerospace, telecommunications, medical and energy storage, and generation.

[0058] Graphene has very large potential in the agriculture industry, such as coffee, food industry, and the environment, as a plant growth stimulator and in fertilizers, Nanoencapsulation and smart-release systems, antifungal and antibacterial agents, smart packaging, water treatment and ultrafiltration, contaminant removal, pesticide and insecticide quantitation, detection systems, and precision agriculture.

[0059] While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. A process of extracting graphene from a feedstock carbon source that is substantially not graphene comprising the steps: a) Mincing the feedstock carbon source into smaller sizes. b) Mixing the minced feedstock carbon source with an absolute carbon source to form a mixture. c) Applying the laser energy to the mixture at high energy power in a vacuum. d) Extracting graphene from the feedstock carbon source.

2. The process as claimed in Claim 1, wherein the feedstock carbon source is at least one selected from a group comprising single-use plastic, household waste, factory waste, and combinations thereof.

3. The process as claimed in Claim 1, wherein the feedstock carbon source is minced into pieces smaller than or equal to 1cm2 in size.

4. The process as claimed in Claim 1, wherein the absolute carbon source is at least one selected from a group comprising charcoal, carbon black, and combinations thereof.

5. The process as claimed in Claim 1, wherein the feedstock carbon source is mixed with an absolute carbon source at a percentage of 0.5 to 1 percent by weight.

6. The process as claimed in Claim t, wherein the laser energy source is continuous wave Fiber (CW Fiber) Laser.

7. The process as claimed in Claim 6, wherein the hand-held CW fiber laser is transmitted by fiber and QBH connector with water cooling compact structure as the adjustable, continuous beam of low power visible light, and very high energy power of near-infrared fiber lasers (1000 - 2000 Watts) with 10 mm burning range at room temperature (25 - 35°C) in the vacuum.

8. The process as claimed in Claim 6, wherein the CW fiber laser is applied for a duration of 60-120 seconds to give 1.5 to 2 Kgs of high-quality graphene from 2.5 Kgs single-use plastic as carbon feedstock in the vacuum.

9. The process as claimed in claim 1, wherein the process results in the formation of valuable gases like hydrogen that can be-captured, for industrial use.

10. A multi-layered, crystalline green graphene, extracted from single use plastic as the feedstock carbon by-the process of CW fiber laser.