Method and composition for ionic liquid based regeneration of cellulose fibers from agro-waste

Abstract

The present invention provides a sustainable and environmentally friendly method for producing regenerated cellulose fibers from rice biomass, including rice husk and rice straw. The method involves delignifying the biomass using a sodium chlorite-acetic acid buffer, followed by dissolution in an ionic liquid, such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and its derivatives, optionally with dimethyl sulfoxide (DMSO) as a co-solvent. The resulting dope is extruded via wet spinning into a coagulation bath to regenerate cellulose fibers. The regenerated fibers exhibit high tensile strength, enhanced flame retardancy due to silica content, and significant biodegradability in soil. The process eliminates the need for toxic solvents used in conventional viscose or lyocell processes and allows for the recovery and reuse of the ionic liquid. Life Cycle Assessment (LCA) demonstrates a significantly lower environmental impact compared to cotton-based fibers. The invention enables valorization of agricultural waste into high-performance textile fibers, supporting circular economy and sustainable manufacturing goals.

Description

:FIELD OF THE INVENTION

[0001] The present disclosure relates to the field of sustainable material science and textile engineering. More particularly, it pertains to a green and environmentally friendly method for the extraction and regeneration of cellulose fibers from rice biomass, including rice husk and rice straw, using ionic liquids and wet spinning techniques. The invention also relates to the composition of spinning dope, the structure and properties of the regenerated fiber, and its applications in flame-retardant and biodegradable textiles.BACKGROUND OF THE INVENTION

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior ar.

[0003] Global textile industry is witnessing a transition from conventional synthetic and natural fibers to more sustainable alternatives due to the rising environmental and health concerns. Synthetic fibers, such as polyester, are derived from non-renewable petrochemicals and contribute to microplastic pollution, carbon emissions, and persistent environmental toxicity due to their non-biodegradability. Meanwhile, cotton cultivation is resource-intensive, demanding large quantities of water, pesticides, and fertile land, thus contributing to ecological degradation.

[0004] Man-made cellulosic fibers, such as viscose and lyocell, provide an alternative to both synthetic and natural fibers. However, the use of hazardous solvents (e.g., carbon disulfide and NMMO) in the viscose and lyocell processes poses significant environmental and occupational hazards, and the solvent recovery systems are both complex and cost-intensive.

[0005] Simultaneously, the agricultural sector generates vast quantities of lignocellulosic biomass, especially from rice cultivation, including rice husk and rice straw. Improper disposal of this biomass, particularly through open-field burning, causes air pollution, nutrient depletion, and greenhouse gas emissions. The conversion of this underutilized waste into value-added products such as textile-grade fibers offers both environmental and economic benefits.

[0006] Despite this, current technologies face challenges in effectively dissolving biomass, removing lignin and silica, and spinning high-strength fibers using environmentally benign methods. A significant technological gap exists in the development of integrated, scalable, and solvent-recyclable processes for the valorization of agro-waste into functional fibers for textile applications.

[0007] Therefore, there is an urgent need to develop a sustainable, non-toxic, and economically viable process that can utilize agricultural residues-particularly rice biomass-for the production of biodegradable and fire-retardant cellulose fibers. The solution must ideally enable recyclable solvent use, minimal chemical load, and superior mechanical and functional performance, while contributing to circular economy models and carbon footprint reduction.OBJECTIVE OF THE INVENTION

[0008] The principal object of the present disclosure is to provide a sustainable method for the regeneration of cellulose fibers from rice husk and rice straw biomass.

[0009] Another object is to use ionic liquids, such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and its derivatives such as [BMIM]Br / [BMIM]BF4 / [BMIM]PF6 / [BMIM]NO3, as green solvents to dissolve delignified biomass.

[0010] It is also an object to develop a wet spinning process that yields high-strength, flame-retardant, and biodegradable fibers.

[0011] A further object is to enable solvent recyclability, reduction in energy inputs, and lower environmental impact compared to conventional processes.

[0012] Yet another object is to enhance mechanical, structural, and fire-resistant properties of the regenerated fibers for use in eco-friendly textiles.SUMMARY OF THE INVENTION

[0013] The present disclosure provides a green process for producing regenerated cellulose fibers from rice biomass, specifically rice husk and rice straw. The process involves delignification of biomass using a sodium chlorite-acetic acid buffer, followed by dissolution in [BMIM]Cl, with or without DMSO as co-solvent. The resultant dope is wet-spun through a syringe pump into a cold water coagulation bath, forming continuous cellulose fibers.

[0014] In an embodiment, the present disclosure provides a method for producing regenerated cellulose fiber from rice biomass comprising the steps of:subjecting rice biomass selected from rice husk or rice straw to a delignification pretreatment using sodium chlorite in an acetic acid buffer;drying and powdering the delignified biomass;dissolving the delignified biomass in an ionic liquid selected from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), optionally in the presence of a co-solvent such as dimethyl sulfoxide (DMSO), under controlled temperature and agitation conditions to form a biomass-ionic liquid solution;loading the said solution into a syringe-based extrusion system and extruding it through a nozzle into a coagulating bath comprising water maintained at a temperature between 6°C to 20°C to form a regenerated cellulose fiber;collecting, washing, and drying the regenerated cellulose fiber.

[0015] In another embodiment, the present disclosure provides a regenerated cellulose fiber obtained from rice biomass comprising rice husk or rice straw, wherein the fiber is produced by de-lignifying the rice biomass, dissolving it in ionic liquids selected from [BMIM]Cl (1-butyl-3-methylimidazolium chloride, 3-methyl-1-isobutylimidazoliumchloride, 1-methyl-3-(1-ethylpropyl)imidazolium chloride, 1-ethylpropylidin-2-ylmethylamine) / [BMIM]Br (1-butyl-3-methylimidazoliumchloride) / [BMIM]BF4 (1-butyl-3-methylimidazolium tetraflourobromate) / [BMIM]PF6 (1-butyl-methylimidazolium hexaflorophosphate) / [BMIM]NO3(1-butyl-3-methylimidazolium nitrate), and wherein with composition of said ionic liquids of 60-95% in pure or mixture form, and regenerating it by wet spinning.

[0016] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.FIGURES OF THE INVENTION

[0017] FIG. 1 schematic presentation of rice waste biomass to produce RHD / RSD followed by green technology to produce RHF / RSF for high tensile strength, flame retardant and biodegradable and sustainable fabric.

[0018] FIG. 2 Dissolution of rice waste biomass in ionic liquid and flame retardant of rice waste biomass (A) biomass solubility in ionic liquid, (B) pictorial presentation of RHD / RSD, (C) flame retardancy of RHF / RSF fabric and (D) burning rate of RHF, RSF and CF.

[0019] FIG. 3 FTIR and XRD spectra (A), (B) FTIR spectra of rice husk biomass, (C), (D) FTIR spectra of rice straw biomass, (E) XRD spectra of rice husk (RH) and (F) XRD spectra of rice straw (RS).

[0020] FIG. 4 Mechanical graph of different concentrations of rice waste biomass (A) tensile strength of RHF, (B) tensile modulus of RHF, (C) tensile strength of RSF and (D) tensile modulus of RSF.

[0021] FIG. 5 FTIR spectra of pretreated agro-waste and agrowased based fibre

[0022] FIG. 6 tensile strength and tensile modulus of agrowaste and forest waste banana fibre (DBF), bamboo fibre (BF), coconut wastefibre (CWF), sugarcane bagasse fibre (SBF), wheat straw fibre (WSF).

[0023] FIG. 7 SEM micrograph of rice waste biomass, (A, B, C) present RHF micrograph and (D, E, F) present RSF micrograph.

[0024] FIG. 8 Flame retardant and burning rate of rice husk fibre and rice straw fibre and cotton fibre

[0025] FIG. 9 Biodegradation cotton fibre (CF), rice husk fabric (RHF), rice straw fabric (RSF) degradation in soil for 98 days.

[0026] FIG. 10 Midpoint result of environmental impact of production of agrowaste biomass fibre (A, B) 1 kg production of rice waste biomass fibre at laboratory scale, and (C, D) 500 kg production of rice waste biomass at industrial scale.DETAILED DESCRIPTION OF THE INVENTION

[0027] The following is a full description of the disclosure's embodiments. The embodiments are described in such a way that the disclosure is clearly communicated. The level of detail provided, on the other hand, is not meant to limit the expected variations of embodiments; rather, it is designed to include all modifications, equivalents, and alternatives that come within the spirit and scope of the current disclosure as defined by the attached claims. Unless the context indicates otherwise, the term "comprise" and variants such as "comprises" and "comprising" throughout the specification are to be read in an open, inclusive meaning, that is, as "including, but not limited to."

[0028] When "one embodiment" or "an embodiment" is used in this specification, it signifies that a particular feature, structure, or characteristic described in conjunction with the embodiment is present in at least one embodiment. As a result, the expressions "in one embodiment" and "in an embodiment" that appear throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the specific features, structures, or qualities may be combined in any way that is appropriate.

[0029] Unless the content clearly demands otherwise, the singular terms "a," "an," and "the" include plural referents in this specification and the appended claims. Unless the content explicitly mandates differently, the term "or" is normally used in its broad definition, which includes "and / or."

[0030] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0031] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0032] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0033] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.

[0034] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.

[0035] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.Definitions:

[0036] For the purpose of the present disclosure, Cellulose may be defined as a polysaccharide consisting of linear chains of β(1->4) linked D-glucose units, which constitutes the primary structural component of plant cell walls.

[0037] For the purpose of the present disclosure, Lignocellulosic Biomass may be defined as a Plant-derived organic matter composed mainly of cellulose, hemicellulose, and lignin, commonly found in agricultural residues such as rice husk and rice straw.

[0038] For the purpose of the present disclosure, Rice Biomass may be defined as Waste byproducts generated from rice cultivation and processing, including but not limited to rice husk and rice straw.

[0039] For the purpose of the present disclosure, Rice Husk (RH) may be defined as a hard protective coating surrounding rice grains, primarily composed of lignocellulosic materials and silica.

[0040] For the purpose of the present disclosure, Rice Straw (RS) may be defined as the stalks remaining after harvesting rice grains, rich in cellulose, hemicellulose, and lignin.

[0041] For the purpose of the present disclosure, Delignification may be defined as the process of removing lignin from plant biomass to isolate cellulose, typically using chemical agents like sodium chlorite under acidic conditions.

[0042] For the purpose of the present disclosure, Ionic Liquid (IL) may be defined as a salt in liquid form at or near room temperature, used in this invention as a non-volatile, recyclable solvent for cellulose dissolution. Example: [BMIM]Cl.

[0043] For the purpose of the present disclosure, [BMIM]Cl may be defined as 1-butyl-3-methylimidazolium chloride and its derivatives, an ionic liquid employed in the present invention for dissolving delignified biomass.

[0044] For the purpose of the present disclosure, DMSO may be defined as Dimethyl sulfoxide, a polar aprotic co-solvent optionally used in combination with ionic liquids to enhance cellulose dissolution.

[0045] For the purpose of the present disclosure, Dope may be defined as a viscous solution or suspension of cellulose in an ionic liquid or solvent mixture, suitable for extrusion in fiber formation processes.

[0046] For the purpose of the present disclosure, Wet Spinning may be defined as a fiber production method where a polymer solution (dope) is extruded through a spinneret into a coagulation bath to form solid fibers.

[0047] For the purpose of the present disclosure, Coagulation Bath may be defined as a liquid medium, typically cold water, into which the dope is extruded to precipitate and regenerate cellulose fibers.

[0048] For the purpose of the present disclosure, Draw Ratio may be defined as the ratio of the winding speed to the extrusion speed during spinning, affecting fiber alignment, orientation, and mechanical strength.

[0049] For the purpose of the present disclosure, Regenerated Cellulose Fiber may be defined as a fiber produced by dissolving cellulose in a solvent, followed by re-solidification through processes such as wet spinning.

[0050] For the purpose of the present disclosure, Flame Retardancy may be defined as the ability of a material to resist ignition and slow down combustion, measured by burning rate (e.g., cm / sec).

[0051] For the purpose of the present disclosure, Biodegradability may be defined as the ability of a material to be broken down by natural microorganisms, measured as percentage mass loss over time in soil.

[0052] For the purpose of the present disclosure, Crystallinity Index (CI) may be defined as a measure of the crystalline content in cellulose fibers, typically determined using X-ray diffraction (XRD) techniques.

[0053] For the purpose of the present disclosure, Tensile Strength may be defined as the maximum stress a fiber can withstand while being stretched, usually measured in megapascals (MPa).

[0054] For the purpose of the present disclosure, Tensile Modulus may be defined as a measure of a fiber's stiffness, representing the ratio of stress to strain in the elastic deformation phase.

[0055] For the purpose of the present disclosure, Life Cycle Assessment (LCA) may be defined as a systematic analysis of the environmental impacts associated with all stages of a product's life, from raw material acquisition to end-of-life disposal.

[0056] In an embodiment, the present disclosure provides a green method for producing regenerated cellulose fibers from rice biomass using ionic liquids. Rice husk and straw undergo delignification, dissolution in [BMIM]Cl and its derivatives, and regeneration via wet spinning.

[0057] In an embodiment, said fibers are high in tensile strength, flame-retardant, and biodegradable.

[0058] In another embodiment, said process eliminates the use of toxic solvents and allows recovery of ionic liquid, enabling sustainable fiber production. Life Cycle Assessment indicates lower global warming potential and toxicity compared to conventional cotton. The invention valorizes agro-waste into environmentally benign textile materials, promoting circular economy.

[0059] In an embodiment, the present disclosure provides a method for producing regenerated cellulose fiber from rice biomass comprising the steps of:subjecting rice biomass selected from rice husk or rice straw to a delignification pretreatment using sodium chlorite in an acetic acid buffer;drying and powdering the delignified biomass;dissolving the delignified biomass in an ionic liquid selected from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), optionally in the presence of a co-solvent such as dimethyl sulfoxide (DMSO), under controlled temperature and agitation conditions to form a biomass-ionic liquid solution;loading the said solution into a syringe-based extrusion system and extruding it through a nozzle into a coagulating bath comprising water maintained at a temperature between 6°C to 20°C to form a regenerated cellulose fiber;collecting, washing, and drying the regenerated cellulose fiber.

[0060] In another embodiment, the rice biomass is pre-treated at a temperature ranging from 60⁰ C - 90°C for a time duration ranging36 - 48 hours.

[0061] In another embodiment, the acetic acid buffer used for delignification has a pH of about 3 - 5.5

[0062] In another embodiment, the de-lignified biomass is dried at a temperature 25⁰ -70⁰ C for a time ranging from 24 - 36 hours before dissolution.

[0063] In another embodiment, the concentration of the delignified biomass in the ionic liquid ranges from 2 wt% to 16 wt%.

[0064] In another embodiment, the extrusion is carried out using a pipette tip of diameter approximately 0.21 mm and a flow rate of approximately 2 ml / min.

[0065] In another embodiment, the coagulating bath comprises two stages, wherein the first stage facilitates precipitation and ionic liquid diffusion, and the second stage facilitates complete removal of residual ionic liquid.

[0066] In another embodiment, the collected fibers are wound using a winder at a speed ranging from 5 mm / sec to 7 mm / sec to provide draw ratios of 2.0 to 4.0.

[0067] In another embodiment, tensile strength of said fiber ranges from 70 MPa to 243 MPa and a tensile modulus ranges from 11 MPa to 80 MPa.

[0068] In another embodiment, biodegradation rate of said fiber ranges from 70% to 90% within 98 days in garden soil.

[0069] In another embodiment, crystallinity indices of said fibers ranges from 47% to 65%.

[0070] In another embodiment, the present disclosure provides a regenerated cellulose fiber obtained from rice biomass comprising rice husk or rice straw, wherein the fiber is produced by de-lignifying the rice biomass, dissolving it in ionic liquids selected from [BMIM]Cl (1-butyl-3-methylimidazolium chloride, 3-methyl-1-isobutylimidazoliumchloride, 1-methyl-3-(1-ethylpropyl)imidazolium chloride, 1-ethylpropylidin-2-ylmethylamine) / [BMIM]Br (1-butyl-3-methylimidazoliumchloride) / [BMIM]BF4 (1-butyl-3-methylimidazolium tetraflourobromate) / [BMIM]PF6 (1-butyl-methylimidazolium hexaflorophosphate) / [BMIM]NO3(1-butyl-3-methylimidazolium nitrate), and wherein with composition of said ionic liquids of 60-95% in pure or mixture form, and regenerating it by wet spinning.

[0071] In another embodiment, the flame retardant properties of fibres with a burning rate is less than 0.5 cm / sec.

[0072] In an additional embodiment, the method may be extended to other lignocellulosic agricultural residues such as wheat straw, corn stover, sugarcane bagasse, jute stick, banana pseudostem, coconut coir, and cotton stalk. These materials can undergo similar delignification and dissolution steps to yield regenerated cellulose fibers using ionic liquid-based processing.

[0073] In an exemplary embodiment, while [BMIM]Cl / [BMIM]Br / [BMIM]BF4 / [BMIM]PF6 / [BMIM]NO3. is preferred, other ionic liquids such as 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), or choline-based ionic liquids may also be employed to dissolve delignified cellulose, depending on the desired dissolution behavior, recyclability, or specific compatibility with a given biomass type.

[0074] In an exemplary embodiment, dope composition may be modified with functional nanoparticles, such as silver nanoparticles for antimicrobial properties, titanium dioxide (TiO₂) for UV resistance, or graphene oxide for enhanced conductivity. These functionalized fibers may be used in smart textiles, wound dressings, or technical fabrics.

[0075] In an exemplary embodiment, cellulose solution can be co-dissolved or blended with chitosan, alginate, polylactic acid (PLA), or starch derivatives to impart enhanced properties such as improved flexibility, moisture retention, or antibacterial activity. Such blends may offer tunable mechanical or barrier properties.

[0076] In an exemplary embodiment, wet spinning process may be adapted to include co-axial nozzles or dual extrusion systems to produce core-shell fibers, where the core and shell consist of different cellulose or biopolymer compositions, offering unique surface properties or delayed release characteristics for active agents.

[0077] In an exemplary embodiment, other non-toxic coagulation media such as ethanol, isopropanol, or aqueous salt solutions (e.g., Na₂SO₄ or NaCl) may be used to optimize fiber morphology, strength, or ionic liquid recovery.

[0078] In an exemplary embodiment, the regenerated fibers may be subjected to hot drawing, annealing, or chemical crosslinking to improve alignment, crystallinity, or moisture stability. Surface functionalization (e.g., plasma treatment or silane coating) may further enhance adhesion, hydrophobicity, or dye affinity.

[0079] In an exemplary embodiment, the regenerated fibers can be directly formed into nonwoven mats, felted products, or used as reinforcement in biocomposites with thermoplastic or thermoset matrices for packaging, automotive, or building materials.

[0080] In an exemplary embodiment, the ionic liquid-based cellulose dope can be adapted for extrusion-based 3D printing of biodegradable scaffolds or used for electrospinning to fabricate nanofibrous membranes for biomedical

[0081] In an embodiment, the use of green solvents such as [BMIM]Cl (an ionic liquid) in combination with optional co-solvents like DMSO enables efficient dissolution of cellulose without relying on hazardous chemicals typically used in viscose or lyocell processes.

[0082] Unlike carbon disulfide or NMMO, the ionic liquids used in this invention are non-volatile, recyclable, and thermally stable, thereby minimizing environmental toxicity and occupational hazards. The wet spinning technique employed is both scalable and adaptable to existing textile manufacturing infrastructure.

[0083] Further, the resulting regenerated cellulose fibers exhibit excellent mechanical properties, including high tensile strength and modulus, making them suitable for diverse textile applications. Furthermore, these fibers show superior flame retardancy due to residual silica content and possess a high degree of biodegradability, thus reducing the accumulation of persistent microplastics in the environment.

[0084] Moreover, life Cycle Assessment (LCA) studies confirm that this invention achieves a significantly lower environmental footprint compared to conventional cotton and synthetic fibers, including reduced global warming potential, lower fossil fuel use, and decreased human toxicity.

[0085] Overall, the invention presents a sustainable, safe, and economically viable alternative for producing high-performance textile fibers while contributing to waste valorization and circular economy goals.

[0086] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art. EXAMPLES

[0087] The present invention is further explained in the form of the following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.Material

[0088] Rice husk biomass was collected from a local store (Varanasi, India). Sodium chloride (analytical grade, 98 % purity), 1-butyl 3-methylimidazolium chloride (analytical grade, 98 % purity), ethanol (analytical grade, 99% purity), and acetic acid (97% purity) was provided by Sisco research laboratory. Experiment and reagent preparation were performed using ultrapure water (conductivity 0.66 mΩ / cm) (Millipore, Merck).Example 1: Rice husk pretreatment

[0089] Rice husk (RHN) and rice straw (RSN) were delignified using 1.5% to 5% sodium chlorite solution prepared in acetic acid buffer (pH 3 to 5.5) at 60⁰C to 90⁰C for 12 to 36 h. After delignified, the rice husk delignified (RHD) and rice straw delignified (RSD) were washed with distilled water to remove trace chemicals and dried at room temperature. Pretreated rice waste such as RHD and RSD makes power using a grinder. Example 2: Solubility of biomass (Rice waste)

[0090] The DMSO / IL mixture with different DMSO / IL molar ratios (30:1, 25:1, 20:1, 15:1, 10:1, 5:1, 2:1, and 1:1) was prepared at ambient temperature. In a typical dissolution experiment, rice waste was dispersed in 2.0 g of the DMSO / IL mixture, and the resulting DMSO / IL-MCC mixture. The DMSO / IL mixture with different DMSO / IL molar ratios (30:1, 25:1, 20:1, 15:1, 10:1, 5:1, 2:1, and 1:1) was prepared at ambient temperature. 0.04 g RHD / RSD was added to the DMSO / IL mixture (1ml to 10 ml), and the resulting DMSO / IL-Biomass mixture was stirred at 50⁰C to 90⁰C for 1to 6 hours. 0.01g to 10g biomass (RHD / RSD) was added more and continuously stirred at the same temperature. If the added biomass cannot be dissolved within 3 hours, the solution becomes unclear under a polarized light microscope. The solution was considered to be saturated with cellulose. Rice waste biomass solubility (wt %) = (weight of biomass / DMSO / IL solvent (ml)) x 100 eq (1)Example 3: Dope preparation and wet spinning of dope After the dissolution of rice waste biomass, dope preparation for the wet spinning process to fibre regeneration was performed. Delignified rice husk (RHD) and rice straw (RSD) powder dried at 25⁰C to 70⁰C for 24 to 36 h to remove moisture, and 2% to 15% RHD and RSD were dissolved in pre-melted 1-butyl 3-methylimidazolium chloride [BMIM]Cl / [BMIM]Br / [BMIM]BF4 / [BMIM]PF6 / [BMIM]NO3 ionic liquids at 50⁰C to 90⁰C. Then dried rice husk powder dissolved in melt [BMIM]Cl ionic with continuous stirring at 50⁰C to 110⁰ C for 1 to 8 hours. The dope of biomass-IL was loaded in a 10ml to 60ml syringe (DISPO VAN) equipped with a pipette tip (0.21 mm diameter) and ejected at a speed of 1 ml / min to 10ml / min at ambient temperature using a syringe pump (NAVSON model). The pipette has a cone shape. The dope was spun into cold water around 6 to 20⁰ C coagulating bath with an air gap, h~ 4 cm to 10cm. The spun filament was transferred within the first coagulation bath for precipitation of cellulose fibre and diffusion of ionic liquid in the coagulating bath, and spun fibre was collected by a gadget winder (custom-built) at a speed of 5 mm / sec to 50mm / sec and calculated the draw ratio The collected fibre was deep in the second coagulating bath for 2 hours to remove the remaining IL. The wet spinning of dope of rice waste under a flow rate of extruder ʋ0 1.90 mm / sec to 10mm / sec and winder fibres wrapping ʋ1 5 mm / sec to 20mm / sec and draw ratio 2.6, to 8 with respect different winder rate. Finally, the spun fibre was collected and air-dried for subsequent characterization (FIG. 1).Example 4: Fourier transformation infrared spectroscopy (FTIR)

[0093] The ATR-FTIR spectra of thread samples kept on Zn-Se crystal were recorded within the infrared between 800-4000 cm-1 in transmittance mode with 4 cm-1 resolution and 64 scans (Cary 630, Agilent USA).X-ray diffraction (XRD)

[0094] Structural analysis of the sample was determined by the Miniflex 600 Desktop XRD System (RIGAKU Corporation, Japan). The copper anticathode was used as a source to produce X-ray (CuKα) scanning was conducted within the 2ʋ range of 5 to 70. The Segal equation (eq.1), Scherrer equation (eq.2) and Bragg's law (eq.7) were used to compute the crystallinity index (CI), crystallite size in nm (D) and d- spacing in nm, respectively.Mechanical characterisation of RHF and RSF

[0095] The tensile strength of the sample was measured by a texture analyser (EZ-SX-500 N, Shimadzu, Japan), having a maximum load cell capacity of 500 N, crosshead speed of 5 mm / min, and a gauge length of 20 mm. The diameter of the fibres was measured using a mini digital thickness gauge meter (Right Gear, India), and the experiment was repeated in triplicates (FIG. 4).Scanning electron microscope (SEM) of RHF and RSF

[0096] The morphology of sample was carried out on JCM-6000 Plus BenchTop Sem Neoscope (JEOL Asia PTE Ltd). Prior to the analysis, the samples were coated with gold and platinum using a Desk Sputter coater (DRS1, UK). During the coating process, a voltage of 10 kV and pressure within the range 2-3 mbar was applied (FIG. 7). Flame retardancy

[0097] Samples were cut into pieces, and a flame retardancy experiment was performed over the ethanol flame. The videos were recorded for each sample till the complete burning of the sample and rate of burning were calculated. The char content was determined by measuring the sample's weight and the char's weight after conducting the flame retardancy (FIG. 8).Biodegradation

[0098] Fabric samples were cut into 2cm x 3cm dimensions, and pre-weight was noted. The biodegradation experiment was performed in garden soil, and the samples were kept at a depth of 4 - 5 cm. The samples were removed every 7 days to measure the weight loss. Example 5: LCA of RH thread compared with polyester and cotton thread LCA for production of cotton thread

[0099] LCA was performed to assess the environmental impact generated during the production of cotton thread. The system boundary for LCA is depicted in Figures, and the assumptions are listed in Table S. The production of 1 Kg of Cotton thread was considered a functional unit in this study, and ReCiPe (H) (ReCiPe 2016 v1.1) was used for LCA studies. The data for analysing LCA impact were sourced from multiple outlets, including the GaBi education database (2020) and the Eco Invent database (version 3.8). LCA has determined in GaBi, and electricity taken from hard coal is considered. Normalization of the impact and sensitivity analysis of dominant categories were also performed. Comparative analysis for the cotton thread and rice husk thread

[00100] The study considered 10 kg cotton thread production as the functional unit to calculate environmental impact. LCA was conducted to assess the ecological impact of transporting raw cotton material from farm to wholesaler and its output in a factory with the assumption listed in Table S.Example 6: Functional properties of RHN, RHD and RHF

[00101] ATR-FTIR spectroscopy was performed to understand on the functional groups in native rice husk and rice straw (RHN and RSN), delignified rice husk and delignified rice straw (RHD and RSD), as well as rice husk fibres and rice straw fibres (RHF and RSF), as depicted in FIG. 3(A-D) and Table S1. The infrared (IR) spectra exhibited distinct peaks in native rice husk (NRH), RHD, and RHF samples at 786 cm⁻¹, 1632 cm⁻¹, and 3428 cm⁻¹)(De et al., 2020; Rai et al., 2024; Ranjan et al., 2024). The peak at 786 cm⁻¹ is associated with the Si-O bond, whereas the peak at 1632 cm⁻¹ is linked to the asymmetric stretching of Si-O-Si and the bending vibration of the O-H bond. The wide band at 3428 cm⁻¹ signifies the stretching vibrations of hydroxyl groups (O-H), indicative of cellulose. In NRH and NRS, the peak at 1625-1632 cm⁻¹ corresponds to the C=C stretching of aromatic carbons in lignin, indicating its presence in the untreated sample. In contrast, a peak at 1736 cm⁻¹ in the RHD and RSD samples corresponds to the C=O stretching vibration of the acetyl group, signifying the existence of hemicellulose. The spectral resemblance between RHD and RHF, as well as RSD and RSF, indicates the efficient regeneration of cellulose in the wet-spinning process utilizing green technology. The XRD study further established that the regeneration verified the structural integrity and increased crystallinity of cellulose after delignification and hemicellulose extraction. These results illustrate the efficacy of ATR-FTIR spectroscopy in verifying the existence and alteration of functional groups during the processing of rice husk and rice straw.Example 7: Structural investigation of RHN, RHD and RHF

[00102] The X-ray diffraction (XRD) analysis of rice husk fiber (RHF) provides valuable insights into the structural modifications occurring during the delignification of rice waste and cellulose regeneration through the wet spinning process. The XRD diffractogram of RHN / RSN, RHD / RSD, and RHF / RSF reveals three distinct peaks at 2Ɵ = 16.4⁰, 22.2⁰, and 34.5⁰ (FIG. 3(E-F)), corresponding to the (110), (200), and (004) crystal planes of cellulose I allomorphs (Biswas et al., 2017; Rai et al., 2024; Ranjan et al., 2024). Additionally, a peak at 2Ɵ = 26.5⁰ in the RHD / RSD and RHN / RSN samples is primarily associated with silica. The diffraction pattern remained consistent throughout the cellulose extraction process, with a significant increase in peak intensity observed in RHD and RSD following delignification, leading to enhanced crystallinity. The crystalline index (C.I) was initially recorded as 54.37% and 57.24%, increasing notably to 70.62% and 68.03% post-delignification. However, after regenerating RHF and RSF using green technology with ionic liquids, crystallinity decreased to 47.61% and 64.37%, respectively. The remaining peaks aligned with those of RHD / RSD, confirming that cellulose fibers regenerated through the wet spinning process after dissolution in ionic liquid [(Bmim)Cl] experienced a decline in C.I., likely due to hydrolysis and cellulose structure degradation. Furthermore, changes in crystallite size and d-spacing were observed across RHN / RSN, RHD / RSD, and RHF / RSF, as detailed in Example 8: Mechanical properties of RHN, RHD and RHF

[00103] Evaluating the mechanical properties of rice waste fibers, particularly their elongation and flexibility, is essential for determining their suitability in fabric production. Rice husk fiber (RHF) exhibits higher tensile strength, whereas rice straw fiber (RSF) has comparatively lower tensile strength. Specifically, 6% RHF achieves a maximum tensile strength of 242.99 MPa and a tensile modulus of 79.81 MPa, while the lowest values recorded for 4% RHF are 70.57 MPa for tensile strength and 11.87 MPa for tensile modulus. A similar pattern is observed in RSF, where 6% RSF reaches a maximum tensile strength of 133.95 MPa and a tensile modulus of 65.18 MPa. In contrast, 4% RSF records the lowest tensile strength at 72.65 MPa and a tensile modulus of 47.04 MPa. These findings highlight the impact of fiber composition on mechanical performance, influencing their potential application in textile manufacturing.Example 9: Scanning electron microscopy of RHF and RSF

[00104] The morphology properties are examined to comprehend the impact of pretreatment on rice waste. The NRH exhibits a brown colour that becomes white upon pretreament and off-white upon spinning in the form of fibres (RHF and RSF), as illustrated in FIG. 3. Due to the presence of silica in rice husk and rice straw, both RHF and RSF exhibit compact aligned cellulose fibrils with a granulated surface, as demonstrated in previous studies (FIG. 5(A-D)). The cross-section of RHF and RSF reveals a solid, compact structure of arranged cellulose chains, contributing to the fibres' high strength. The fracture morphology demonstrates uneven pores during the forceful fracturing of the fibres during the tensile measurement.Example 10: Flame retardancy of RHF, RSF and CF

[00105] The flame-retardant properties of RHF and RSF were evaluated by exposing them to direct flame for 32 seconds, as illustrated in FIG. 2(C). In comparison, conventional cotton fiber (CF) ignites rapidly within 12 seconds due to its high flame propagation rate, leading to incomplete combustion. This results in a residual char of 17.53% and a burning rate of 2.9 cm / sec, as depicted in FIG. 2(D). Conversely, RHF and RSF exhibit significantly lower burning rates of 0.2 cm / sec and 0.5 cm / sec, respectively. The presence of silica within these fibers acts as a flame inhibitor, slowing down combustion and facilitating the complete burning of cellulose fibers. Given their enhanced flame resistance, rice waste-derived fabrics offer potential applications in textile manufacturing, particularly for fire-resistant materials.Example 11: Biodegradation of RHF, RSF and CF

[00106] The biodegradation of regenerated fibres from RHF, RSF, and CF was examined under soil circumstances over 98 days, during which significant disintegration and colour alteration was seen as time progressed, as shown in FIG.6. After two weeks of soil burial, CF, RHF and RSF exhibited degradation rates of 12.28%, 4.4% and 6.67%, respectively, while CF demonstrated rapid disintegration, achieving 87.72% degradation in 98 days. In contrast, RHF and RSF had slower degradation rates of 71.75% and 83.48%, which might be the presence of silica in RHF and RSF.Example 12: LCA studies for the production of Rice waste biomass fibre

[00107] LCA was conducted to evaluate the environmental impacts associated with the production of RWF and is compared to conventional cotton fibre by pretreatment and dissolution and wet spinning of rice waste fibre (RWF include RHF and RSF) routes. The LCA of RWF in climate change category demonstrated the highest environmental impact of 2.66 kg CO2 eq. (excluding and including biogenic carbon). In comparison, LCA of conventional cotton fibre (including cultivation and harvesting of cotton, transportation and yarn manufacturing ) shows global warming potential of 22.1 kg CO2 which is almost 6 times higher than RWF (Kazan et al., 2020). Climate change, fossil depletion and human toxicity categories had impact of 2.66, 0.596 kg oil eq., and 0.0281 Kg 1,4 DB eq., respectively. The primary source of environmental impacts in RWF production is from electricity-intensive, pretreatment, dissolution and wet spinning processes due to utilization of hard coal. The production of RWF resulted in least environmental impact across three categories: fine particulate (0.00106 kg PM 2.5 eq.), freshwater eutrophication (1.44Ex10-7kg P eq.), and Stratospheric ozone depletion (5.34Ex10-7 kg CFC eq.). LCA of conventional cotton fibre shows metal depletion 12 kg oil eq., and human toxicity 1.098 kg 1,4 DB eq. which is almost 2 times higher than that of RWF.21 The mid-point impact was normalized (FIG. 9) to find out the dominant categories influencing RWF production. After normalization, climate change, fossil depletion, and human toxicity were found to have the highest impacts. The sensitivity analysis was performed to evaluate the environmental effects of various processes utilized during RWF production. According to the normalization results presented in Table S3 and S4, climate change, fossil depletion, and human toxicity emerged as the dominant categories. Sensitivity analysis was conducted to examine variations in impact of these dominant categories when input for electricity consumption, pretreatment, dissolution and wet spinning process were altered positively (by 10 %) and negatively (by 8 %). In case of electricity, it was noted that 10% increase led to corresponding rise in climate change, fossil depletion, and human toxicity by 11.27% 7.52% and 0.638% respectively. Conversely, reduction of 8% in electricity input resulted in decreased impacts of climate change, fossil depletion, and human toxicity by 7.37%, 6.02%, and 0.64% respectively. In case of pretreatment, dissolution and wet spinning process, 10% increase in input resulted in rise of impacts for climate change, fossil depletion, and human toxicity by 594%, 5.01% and 0.638% respectively, for pretreatment, and by 0% in every dominant category, for dissolution, and by 3.22%, 4.16%, 0.64% respectively for wet spinning process. Conversely, reduction of 8% input for pretreatment, dissolution and wet spinning process, led to decrease in climate, fossil depletion, and wet spinning process by 0.46%, 0.334%, 0% respectively, for pretreatment, by

[00108] LCA studies indicate that the newly developed regenerated wood fiber (RWF), produced using cost-effective and environmentally friendly ionic liquid chemicals, demonstrates considerably lower environmental impacts. The dissolution process shows rates of 0%, 0.16%, and 0%, while the wet spinning method exhibits values of 2.76%, 3.68%, and 0.319%. These findings suggest that RWF presents a viable and sustainable alternative to traditional cotton yarn in the textile industry, offering a more eco-friendly solution with reduced environmental consequences.Example 12: FTIR of WSF, BF, SBF, CWF and DBF

[00109] FTIR spectroscopy was conducted to investigate the chemical composition and structural changes during the dissolution, regeneration, and fiber formation of agrowaste using ionic liquids. The samples include raw biomass, delignified biomass, ionic liquid-treated substrates, and spun fibers, labeled as: DB, DBF, DBFF, DSB, DSBF, DWS, DWSF, DCW. All spectra exhibited a broad absorption peak around -3330 cm⁻¹, corresponding to the O-H stretching vibrations of cellulose. This peak was sharper and more intense in regenerated fibers ( DBFF, DSBF), suggesting stronger intermolecular hydrogen bonding post-regeneration. The peaks at -2918 cm⁻¹ were associated with aliphatic C-H stretching, common in cellulose and hemicellulose. The pretreated bagrowaste (DB, DSB, DWS) exhibited a prominent peak near 1732 cm⁻¹, attributed to the C=O stretching of ester linkages in hemicellulose and lignin

[00110] After ionic liquid dissolutin and spinning (DBF, DBFF, DSBF), the intensity of this peak significantly decreased or disappeared, indicating effective removal of lignin. In raw and partially treated samples, distinct peaks were observed around 1604 cm⁻¹ and 1510 cm⁻¹, which are characteristic of the aromatic skeletal vibrations of lignin. These peaks diminished in regenerated fiber samples, confirming delignification and regeneration process using ionic liquids. The peak near 1425 cm⁻¹ (CH₂ bending in cellulose) and around 1375 cm⁻¹ (C-H deformation) were observed in all samples but became more defined in regenerated fibers, indicating increased cellulose purity. A strong band near 1030 cm⁻¹ was present across all samples, corresponding to the C-O-C stretching of the β-1,4-glycosidic linkage in cellulose. This peak remained prominent in all regenerated fibers, confirming that the cellulosic backbone was retained after regeneration. The small shoulder at -896 cm⁻¹, assigned to amorphous cellulose (C-H deformation in β-glycosidic linkages), was evident in raw and untreated samples. A shift in intensity or appearance of a sharper band in this region in regenerated fibers suggests alteration in the crystalline / amorphous ratio, likely due to reorganization of cellulose chains during regeneration. FTIR spectroscopy conclusively demonstrated the chemical transformation of agrowaste biomass into high-purity regenerated cellulose fibers using ionic liquid treatment. The removal of hemicellulose and lignin was validated by the loss of associated peaks, while the preserved cellulose backbone was confirmed through the retention of β-glycosidic linkage signals. This supports the feasibility of ionic liquids for eco-friendly processing of lignocellulosic biomass into functional textile fibers.

[00111] The assessing of the mechanical properties of agrowaste, namely regarding elongation and flexibility, is crucial factor in determining its utilization in fabric production. Wheat straw fibre exihibits superior tensile strength 456 MPa and tensile modulus 78.90 MPa , whereas bamboo fibre (DBF) exhibits inferior tensile strength 89.3 MPa and tensile modulus 25.8 MPa. The mechanical analysis confirmed that wheat straw (WSF) and date-based fibers (DBF) provide the highest tensile moduli, indicating their suitability for high-strength applications. Ionic liquid-mediated processing successfully enhanced the mechanical integrity of fibers, particularly when the cellulose source was rich and properly purified.

[00112] Accordingly, the present invention highlights the use of green technology as an efficient, cost-effective, and scalable approach for producing textile fibers from rice waste. The incorporation of 6% RHF and RSF results in maximum tensile strengths of 179 MPa and 139 MPa, with tensile modulus values of 80 MPa and 65 MPa. Additionally, the fibers exhibit flame retardancy rates of 0.2 cm / sec and 0.5 cm / sec, along with a biodegradation rate of 69% within 90 days. Life Cycle Assessment (LCA) findings reveal that this sustainable production method has a substantially lower environmental impact compared to conventional cotton fiber production, reducing Global Warming Potential (GWP) by 86.53% during manufacturing. Furthermore, at the end of life (EOL), this green technology demonstrates 91.8% and 68.7% lower human health damage impact compared to cotton and synthetic fibers, respectively. The developed fiber exhibits a biodegradability range of 83.48% to 87.72% within 98 days, reinforcing its sustainability. The LCA analysis confirms that fibers derived from rice waste have an ecological footprint significantly lower than traditional cotton-based fibers, with a 12.04% reduction in GWP. This innovative approach results in fibers with excellent physiochemical and structural characteristics, making them a viable alternative to conventional cotton textiles. Moreover, utilizing rice waste, a renewable resource, through scalable and eco-friendly methods reduces reliance on monoculture cotton farming while mitigating microplastic pollution in the environment (FIG. 10).

[00113] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.ADVANTAGES OF THE INVENTION

[00114] The present invention offers several significant advantages over conventional methods of fiber production. By utilizing agricultural waste materials such as rice husk and rice straw-both of which are abundant and underutilized-the process adds value to biomass that is otherwise discarded through environmentally harmful methods like open-field burning.

[00115] The use of green solvents such as [BMIM]Cl (an ionic liquid) in combination with optional co-solvents like DMSO enables efficient dissolution of cellulose without relying on hazardous chemicals typically used in viscose or lyocell processes.

[00116] Unlike carbon disulfide or NMMO, the ionic liquids used in this invention are non-volatile, recyclable, and thermally stable, thereby minimizing environmental toxicity and occupational hazards. The wet spinning technique employed is both scalable and adaptable to existing textile manufacturing infrastructure. The resulting regenerated cellulose fibers exhibit excellent mechanical properties, including high tensile strength and modulus, making them suitable for diverse textile applications.

[00117] Furthermore, these fibers show superior flame retardancy due to residual silica content and possess a high degree of biodegradability, thus reducing the accumulation of persistent microplastics in the environment. Life Cycle Assessment (LCA) studies confirm that this invention achieves a significantly lower environmental footprint compared to conventional cotton and synthetic fibers, including reduced global warming potential, lower fossil fuel use, and decreased human toxicity.

[00118] Overall, the invention presents a sustainable, safe, and economically viable alternative for producing high-performance textile fibers while contributing to waste valorization and circular economy goals.

Claims

1. A method for producing regenerated cellulose fiber from rice biomass comprising the steps of: subjecting rice biomass selected from rice husk or rice straw to a delignification pretreatment using sodium chlorite in an acetic acid buffer; drying and powdering the delignified biomass; dissolving the delignified biomass in an ionic liquid selected from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), optionally in the presence of a co-solvent such as dimethyl sulfoxide (DMSO), under controlled temperature and agitation conditions to form a biomass-ionic liquid solution; loading the said solution into a syringe-based extrusion system and extruding it through a nozzle into a coagulating bath comprising water maintained at a temperature between 6°C to 20°C to form a regenerated cellulose fiber; collecting, washing, and drying the regenerated cellulose fiber.

2. The method as claimed in claim 1, wherein the rice biomass is pre-treated at a temperature ranging from 60⁰ C - 90°C for a time duration ranging36 - 48 hours.

3. The method as claimed in claim 1, wherein the acetic acid buffer used for delignification has a pH of about 3 – 5.

54. The method as claimed in claim 1, wherein the delignified biomass is dried at a temperature 25⁰ -70⁰ C for a time ranging from 24 – 36 hours before dissolution.

5. The method as claimed in claim 1, wherein the concentration of the delignified biomass in the ionic liquid ranges from 2 wt% to 16 wt%.

6. The method as claimed in claim 1, wherein the extrusion is carried out using a pipette tip of diameter approximately 0.21 mm and a flow rate of approximately 2 ml / min.

7. The method as claimed in claim 1, wherein the coagulating bath comprises two stages, wherein the first stage facilitates precipitation and ionic liquid diffusion, and the second stage facilitates complete removal of residual ionic liquid.

8. The method as claimed in claim 1, wherein the collected fibers are wound using a winder at a speed ranging from 5 mm / sec to 7 mm / sec to provide draw ratios of 2.0 to 4.0.

9. The method as claimed in claim 1, wherein tensile strength of said fiber ranges from 70 MPa to 243 MPa and a tensile modulus ranges from 11 MPa to 80 MPa.

10. The method as claimed in claim 1, wherein biodegradation rate of said fiber ranges from 70% to 90% within 98 days in garden soil.

11. The method as claimed in claim 1, wherein crystallinity indices of said fibers ranges from 47% to 65%.

12. A regenerated cellulose fiber obtained from rice biomass comprising rice husk or rice straw, wherein the fiber is produced by delignifying the rice biomass, wherein the fiber is produced by de-lignifying the rice biomass, dissolving it in ionic liquids selected from [BMIM]Cl (1-butyl-3-methylimidazolium chloride, 3-methyl-1-isobutylimidazoliumchloride, 1-methyl-3-(1-ethylpropyl)imidazolium chloride, 1-ethylpropylidin-2-ylmethylamine) / [BMIM]Br (1-butyl-3-methylimidazoliumchloride) / [BMIM]BF4 (1-butyl-3-methylimidazolium tetraflourobromate) / [BMIM]PF6 (1-butyl-methylimidazolium hexaflorophosphate) / [BMIM]NO3(1-butyl-3-methylimidazolium nitrate), and wherein with composition of said ionic liquids of 60-95% in pure or mixture form, and regenerating it by wet spinning.

13. The fibre as claimed in claim 12, the flame retardant properties of fibres with a burning rate is less than 0.5 cm / sec.